My 05 Envoy has no ballz. 0-60 times horrible!

[CaptainXL]

Wow! I know you said earlier that you felt performance was better in cooler temperatures but WOW!!! This CAN'T be the the complete explanation for what's happening. Essentially you would be saying that a 30-40ish degree temperature change equates to a 3+ second difference in your 0-60 times?!?! The air density doesn't change THAT much over that temperature range and even then I think the PCM is actively managing the air-fuel mixtures based on the IAT data.

I mean consider all the people that went to an aftermarket CAI...even though ours are already considered to be somewhat of a cold air intake system, even if the aftermarket ones gained someone a 10 degree intake air temp difference, your result would suggest that they should also experience significant performance improvents, which isn't really consistent with all the feedback that I've read (some impreovement yes, but nowhere near this much).

Temp change may be a factor, but I suspect it would have to be a secondary one...maybe along the lines of a bad IAT sensor feeding the PCM bad data?? I know there's concern sometimes about damaging the MAF sensors when people clean their throttle bodies, I can't say I've seen anything about the IAT's though...is it possible for one to go bad, be damaged or dysfunctional in a way that doesn't throw codes for the longer term?

You've suspected a lack of performance from when you first got the vehicle, you've had it now over 1-1/2 years, so did you notice a similar massive perfomance gain last fall when temperatures started getting cooler?

Yes i have felt this last year coming up to winter when the temps start going below 70. Feels like someone put nitrous in.

 

[DenaliHD66]

I have a cold air intake and I noticed a big difference when the air temp is in the low 70s and below. Especially when the air is really dry, my engine roars with all the air it sucks in, and it shifts much quicker too.

 

[CaptainXL]

Well the last bit of evidence we need would be to get someone from Florida or some other hot and humid state to do a run and see if their HP drops off this much. Michigan broke record highs this year so it was just as hot up here as down there. We would be looking for the same thing I saw. A 3-4 second drop in 0-60 times. Once confirmed we can close this case.

 

[Chickenhawk]

Heat plus weight?

I wonder what your all-up weight is right now?

The thing to remember about extra weight is that the horsepower required to overcome weight goes up EXPONENTIALLY. I am hoping one of the physics majours can confirm, but if I remember from high school, if you double the weight, you would need 4 times the horsepower for the same performance.

SWB trucks should run 0-to-60 times in 7 and change on a good day, in cool conditions, a part tank of gas, no extra cargo in the back and with no adverse slope on the road.

It is logical that a LWB with the extra 560 pounds or so would be a few seconds off that pace. In 2002, Car & Driver tested a SWB at 7.9 seconds 0-60 and a LWB at 9.5 seconds. (They also tested a 2WD V8 EXT at 8.7 seconds, and the saving of 236 pounds over a 4WD version was still not enough to overcome the extra weight with the long wheelbase.)

Weight, even 560 pounds or so, makes a BIG difference.

 

[CaptainXL]

Heat plus weight?

I wonder what your all-up weight is right now?

The thing to remember about extra weight is that the horsepower required to overcome weight goes up EXPONENTIALLY. I am hoping one of the physics majours can confirm, but if I remember from high school, if you double the weight, you would need 4 times the horsepower for the same performance.

SWB trucks should run 0-to-60 times in 7 and change on a good day, in cool conditions, a part tank of gas, no extra cargo in the back and with no adverse slope on the road.

It is logical that a LWB with the extra 560 pounds or so would be a few seconds off that pace. In 2002, Car & Driver tested a SWB at 7.9 seconds 0-60 and a LWB at 9.5 seconds. (They also tested a 2WD V8 EXT at 8.7 seconds, and the saving of 236 pounds over a 4WD version was still not enough to overcome the extra weight with the long wheelbase.)

Weight, even 560 pounds or so, makes a BIG difference.

What your ultimately getting at here is whats considered Power to Weight ratio and is directly proportional.

From what I understand, since a dynamometer(dyno) uses torque to calculate horsepower it would mean that the more a vehicle weighs then the longer it would take to get a vehicle up to a cetain speed. Calculations can be made easy enough using direct methods. But then you have to take into account certain variables such as aerodynamic drag and rolling resistance. Im not up to speed on such modifiers. My calculations would be based upon a frictionless environment.

Not sure if this is a correct method but lets use time to weight ratio and see what we get...

To figure 0-60 times using a baseline for the SWB going to a LWB you would plug in the following.

0-60 SWB time/ SWB Weight = x time / LWB Weight

8 / 4600 lbs = x / 5100 lbs

x ~ 9 seconds

Of course greater weight would add time to this calculation using friction modifiers so lets assume a 10 second 0-60 time is accurate.

To me this sounds like the correct method but Stephen Hawkins might need to interject as needed.

 

[DenaliHD66]

Heat plus weight?

I wonder what your all-up weight is right now?

The thing to remember about extra weight is that the horsepower required to overcome weight goes up EXPONENTIALLY. I am hoping one of the physics majours can confirm, but if I remember from high school, if you double the weight, you would need 4 times the horsepower for the same performance.

SWB trucks should run 0-to-60 times in 7 and change on a good day, in cool conditions, a part tank of gas, no extra cargo in the back and with no adverse slope on the road.

It is logical that a LWB with the extra 560 pounds or so would be a few seconds off that pace. In 2002, Car & Driver tested a SWB at 7.9 seconds 0-60 and a LWB at 9.5 seconds. (They also tested a 2WD V8 EXT at 8.7 seconds, and the saving of 236 pounds over a 4WD version was still not enough to overcome the extra weight with the long wheelbase.)

Weight, even 560 pounds or so, makes a BIG difference.

Who said an XL with the 4.2L 4x4 with oversized tires and cargo can't run in the 7s? I present: my truck.

[video=youtube;YqktkkHInVc]http://www.youtube.com/watch?v=YqktkkHInVc&feature=plcp[/video]

 

[seanpooh]

7 seconds huh? I think you were going down a hill

I seriously cannot think of anything to get to 60 in that short of time. Something has to be lagging or the 2002 just suck.

I'm loading up my video of my run today (finally) from 0-90mph on flat land from rest with ~1/8ish of a tank of gas and no one inside or cargo.

Just remember, my speedo is off by 2 mph ahead (because of tires in rear). So if I was at 55mph cruising, I'm actually going 57 mph according to my gps and a sheriffs speed thingy on sides of a road.

 

[CaptainXL]

Who said an XL with the 4.2L 4x4 with oversized tires and cargo can't run in the 7s? I present: my truck.

I found out you did the following to your truck.
Are you telling us that these mods gave you those results?

K&N FIPK Cold Air Intake.
Flowmaster Cat-back Exhaust System.
PCM4LESS PCM Tune (87 Octane, governor removed).

 

[Phantom]

I'm curious to see what ours will do now that's its cooling off. I can say that tonight coming home from work (with it being 50ish out) it seems that there was more power than usual well at least it felt like it. I might have to do a run tomorrow morning on the way home at 5:30 am...

 

[seanpooh]

[video=facebook;509453809065110]http://www.facebook.com/photo.php?v=509453809065110[/video]

Here is my 0-90. Shift from 1-2 is at 50, then 2-3 at 90. Does the torque converter stall pertain to anything since I don't move from 0 until 2000K rpm or the speedo is sluggish?
Or the tranny is just slow, deep pan at that... it's been tuned for the hardest shift... as for temperature outside, I didn't notice a change.

The video from DenaliHD shows that his 1-2 was extremely fast to get through 600-6000K rpm which shifted at the same 50mph and his 1-2 shift time was fast and soft like a car would shift. My shift from 1-2 throws heads back.

Straight cat back exhaust for me.

 

[CaptainXL]

Here is my 0-90. Shift from 1-2 is at 50, then 2-3 at 90.

Can't answer your question...but I find it amazing that you have all those mods and yet your 0-60 times are still right along with some of our stock trucks (about 10 seconds). Is PCMForLess screwing people?

 

[WarGawd]

Lol, lots of commentary added since my last...be warned I've had a few drinks before this post.

Yes i have felt this last year coming up to winter when the temps start going below 70. Feels like someone put nitrous in.

Honestly I'm surprised that anybody would be experiencing that kind of a change. I'm not disputing what you're saying, just commenting that people's perceptions when they notice a difference tend to magnify the reality somewhat. In your case you seem to have real data/video that supports your claims so let's work with it for now. Just curious, is that around the same time frame that it started to dawn on you that you may have something going on?

Well the last bit of evidence we need would be to get someone from Florida or some other hot and humid state to do a run and see if their HP drops off this much. Michigan broke record highs this year so it was just as hot up here as down there. We would be looking for the same thing I saw. A 3-4 second drop in 0-60 times. Once confirmed we can close this case.

I think that would be premature. I think we've seen enough vehicle performance variability in this thread alone to suggest there's more going on than a simple temperature difference. You may get results from one person in Florida that seems to have the same issue, and just accept that this is the way it should be. To be clear I'm not disputing that temperature will have some effects, perhaps even measurable & noticeable. My argument is with the magnitude of the change you have seen...it doesn't fit for me.

One of the reasons I started commenting on this thread in the first place is that we have essentially the same truck...and my performance seemed to be significantly different from yours. While I hoped to offer you a baseline for comparison, I also expected to learn a lot about my own truck, as it is still relatively new to me. Lastly, I wanted to comment and stress here that my video runs vs my scan tool runs DID NOT experience any real difference despite a fairly similar temperature change betweeen the two tests. In fact I would argue that the differences (of the order of 10ths of a second), were almost statistically insignificant given the limited number of samples.

Heat plus weight?

I wonder what your all-up weight is right now?

The thing to remember about extra weight is that the horsepower required to overcome weight goes up EXPONENTIALLY. I am hoping one of the physics majours can confirm, but if I remember from high school, if you double the weight, you would need 4 times the horsepower for the same performance.

SWB trucks should run 0-to-60 times in 7 and change on a good day, in cool conditions, a part tank of gas, no extra cargo in the back and with no adverse slope on the road.

It is logical that a LWB with the extra 560 pounds or so would be a few seconds off that pace. In 2002, Car & Driver tested a SWB at 7.9 seconds 0-60 and a LWB at 9.5 seconds. (They also tested a 2WD V8 EXT at 8.7 seconds, and the saving of 236 pounds over a 4WD version was still not enough to overcome the extra weight with the long wheelbase.)

Weight, even 560 pounds or so, makes a BIG difference.

Advance warning....you may just want to skip ahead a few paragraphs to the SUMMARY.

I agree weight can make SOME difference. When we are talking about 5000lb trucks, a difference of 250 lbs is 5%. CaptainXL gets it fundamentally correct later on. Newtons F=ma rewritten as a = F/m = 1/m *F . So mass is a constant. Any acceleration will be linearly (but inversely) proportional to the applied force. My next statement may take a read or two but here goes: EVEN IF the force is non-linear (say due to drag factors, velocities, whatever other variable you wish to throw in) the RESULTING ACCELERATION IS STILL LINEARLY PROPORTIONAL TO THAT FORCE. Bear with me you'll see in a second why I risked complicating things.

Take my truck as an example for the moment. It's mass (m) is fixed. If I apply a force (F) to it, it will experience a certain acceleration (a). If we dig deeper and look at what produces that force we could write a big long equation involving a pile of variables. So we could substitute F' for F where F' = (w + cx[SUP]2[/SUP] + dy[SUP]3[/SUP] + ez[SUP]4[/SUP] + ....). Here the w represents the original force F where we ignored the nonlinear modifiers, c,d & e are just some constants, and x,y,z... are all the nonlinear variables you wish to include. I have 2 arguments here:

1) The constants will be small thus making the nonlinear effects small, and even though it wouldn't withstand scientific scrutiny, it would withstand engineering scrutiny. In lay terms what that means is these additonal terms don't add up to beans. They are small enough to be ignored, especially when you consider argument #

2) EVEN IF THOSE TERMS ALL ADDED UP to be something significant in proportion to our original "F", IT DOES NOT MATTER when you are comparing vehicle A to vehicle B. Both vehicles have fundamentally the same engine, same power production, same tranny, same rear end, same PCM, same fuel yada yada yada. Those are all the important things that belong in the linear force component. All the other crap cancels each other out when comparing Vehicle A to B.

SUMMARY: No, sorry Chickenhawk. I think what you're recalling is the squared relationship of power and air drag. Air drag is what varies with v[SUP]2[/SUP]. And it is not logical that a variance of 560lbs (~ 10% weight variance) would account for a "few seconds difference". Well maybe, but only if we're talking about 30s vs 27s or 33s (IE ~ 10% time diff). Think about drag racers...they spend a ton of time stripping out carpeting and trim and dash pieces and so on, to reduce weight by several hundred pounds to save of the order of several TENTHS of a second on 1/4 mile times...here we're talking about 0-60 times over a much shorter distance - someone has a hell of a job cut out for them if they wanna claim a 10% weight difference (doubtful its anywhere near that, since Captain and I have the same truck remember) and 30 deg air temp difference are going to save anybody 3 or more FULL SECONDS on a 0-60 time of ~14s, ie 20% or better?!?!?! And also don't forget that CaptainXL has experienced this massive change with NO SIGNIFICANT WEIGHT CHANGE to his own truck. A few pounds of gas and a pile of cookie crumbs is irrelevant.

What your ultimately getting at here is whats considered Power to Weight ratio and is directly proportional.

<snip>

Not sure if this is a correct method but lets use time to weight ratio and see what we get...

To figure 0-60 times using a baseline for the SWB going to a LWB you would plug in the following.

0-60 SWB time/ SWB Weight = x time / LWB Weight

8 / 4600 lbs = x / 5100 lbs

x ~ 9 seconds

Of course greater weight would add time to this calculation using friction modifiers so lets assume a 10 second 0-60 time is accurate.

To me this sounds like the correct method but Stephen Hawkins might need to interject as needed.

Not at all. I totally agree with the methodology and math. Friction and other modifiers only affect the absloute results for a single vehicle. For vehicle comparisons, all those terms cancel each other out on both sides of the equation. My friction is NOT fundamentally different than yours, my air drag is NOT significantly different to yours etc etc. We're looking for something that can account for a BIG difference...a BIG change that you have happen to you that I DO NOT have happen to me, under extremely similar environmental conditions. And furthermore, whatever it is that ultimately is found to account for that, is something that also eludes detection and reporting via codes or MILs.

LMFAO - post exceeds forum character limits....see Part 2 Next

 

[WarGawd]

Who said an XL with the 4.2L 4x4 with oversized tires and cargo can't run in the 7s? I present: my truck.

<video link snipped - GOD I hate when people quote the whole damn post complete with 41 attached pictures!!! LMAO>

So along comes Denali, with video evidence, to make me eat crow. If this wasn't a semi serious forum where I have no reason to believe anyone is faking videos, I'd run outta here screaming B*****T. I can't say too much, the video is there. Tranny shift at 6100/50mph (indicated, but wrong) suggests the 3.42 rear end, if you could confirm that (it might have 3.73 or 4.10 IF the tires are large enough to throw the speedo off by the appropriate amounts) ? I say 50mph indicated but wrong, because you have oversize tires, and PCM4 I don't believe can do speedo adjustments on pre- '06 PCMs. OTOH, the larger tires effectively REDUCE your gear ratios, which should lead to SLOWER TIMES!!!. Helluva CAI and tune from PCM. Get me one of those!!

On a slightly more serious note, that seems like great perfomance, and I think it's really worth looking into. For the original purpose of CaptainXL's post, it helps to keep all the variables as similar as possible. It seems like Cap'n is more familiar with your mods than I, so for everyone else's benefit, can you summarize any and all pertinent truck specs?

7 seconds huh? I think you were going down a hill

Nah I think he forgot to mention the Nitrous!!! :wootwoot:

I found out you did the following to your truck.
Are you telling us that these mods gave you those results?

K&N FIPK Cold Air Intake.
Flowmaster Cat-back Exhaust System.
PCM4LESS PCM Tune (87 Octane, governor removed).

Not to mention that seanpooh has a PCM4 tune and doesn't seem to have gotten anything out of it.....so if those are even close to the same, that leave only the CAI and Flowmaster???? Lol I was gonna say I was speechless, clearly that's not true....how about heheh

I'm curious to see what ours will do now that's its cooling off. I can say that tonight coming home from work (with it being 50ish out) it seems that there was more power than usual well at least it felt like it. I might have to do a run tomorrow morning on the way home at 5:30 am...

Please, have a go....I think we're all kinda curious for anything that could lead to a satisfactory explanation....just post all the relevant details/truck specifics

<video snip>

Here is my 0-90. Shift from 1-2 is at 50, then 2-3 at 90. Does the torque converter stall pertain to anything since I don't move from 0 until 2000K rpm or the speedo is sluggish?
Or the tranny is just slow, deep pan at that... it's been tuned for the hardest shift... as for temperature outside, I didn't notice a change.

The video from DenaliHD shows that his 1-2 was extremely fast to get through 600-6000K rpm which shifted at the same 50mph and his 1-2 shift time was fast and soft like a car would shift. My shift from 1-2 throws heads back.

Straight cat back exhaust for me.

Yeah that was kinda painful to watch. Little hard to keep the timeline onscreen , but geez...like 30 seconds to get to 90? WITH a PCM4 tune....and presumably at close to the same ambient temps as Captain's latest video????

Can't answer your question...but I find it amazing that you have all those mods and yet your 0-60 times are still right along with some of our stock trucks (about 10 seconds). Is PCMForLess screwing people?

I kinda see your point Captain, but it wouldn't be my first suspicion. I mean they have competitors....and have many satisfied customers that say they experienced right around the kind of benefits they expected to (a few HP and maybe 1-2 mpg). It would really be interesting to see a bunch of members who have the Wester's tune in this thread for comparison.

But this is all part and parcel of the big picture as to why I was leaning against engine/power production factors...you've been meticulous on maintenance, (carpets? drain tubes for sunroof?? I can just tell you're as anal and detail oriented as I am...no insult intended either...) your fuel pressure seems right, plugs, TB done, ECT, clean air filter,no codes, no exhaust backpressure, Torque app that told you at least once that the power is roughly right (BTW what was the ambient temp when you did that?).

To me all that points in some other direction. I'm sorta glad to see that others more familiar are pointing you to consider tranny issues. Hopefully something comes of it.

Does ANYBODY have any fkn CLUE how hard all that was to type by blowing in a little air tube attached to my keyboard?!?!?!??! Hope it's appreciated!!

 

[neelskit]

Since you noticed a difference based on ambient temperature are you able to read the value of your IAT with your scanner? If so, how does that reading compare to the actual ambient temperature in the engine compartment? Just curious about something...

 

[C-ya]

Since you noticed a difference based on ambient temperature are you able to read the value of your IAT with your scanner? If so, how does that reading compare to the actual ambient temperature in the engine compartment? Just curious about something...

Since you asked (I don't have an issue with low power), I have noticed that the IAT reading is generally several (20-30+) degrees higher than the OAT reading. I have been meaning to ask about this as I am not sure sure where the IAT sensor is and why it would be so much higher than ambient.

Or maybe my IAT PID/formula is wrong.

 

[CaptainXL]

Since you asked (I don't have an issue with low power), I have noticed that the IAT reading is generally several (20-30+) degrees higher than the OAT reading. I have been meaning to ask about this as I am not sure sure where the IAT sensor is and why it would be so much higher than ambient.

Or maybe my IAT PID/formula is wrong.

Already proved to not be an issue. My IAT is about 30 degree f higher than outside temp as well. It must be normal because I changed it with a new one from GM. No difference.

 

[neelskit]

Is that temp difference on a cold or warm engine?

 

[CaptainXL]

Honestly I'm surprised that anybody would be experiencing that kind of a change. I'm not disputing what you're saying, just commenting that people's perceptions when they notice a difference tend to magnify the reality somewhat. In your case you seem to have real data/video that supports your claims so let's work with it for now. Just curious, is that around the same time frame that it started to dawn on you that you may have something going on?

No, I have been experiencing off and on instances where the power seems to be much greater than average. My acquisition of a scan tool prompted me to investigate further.

I think that would be premature. I think we've seen enough vehicle performance variability in this thread alone to suggest there's more going on than a simple temperature difference. My argument is with the magnitude of the change you have seen...it doesn't fit for me.

I'm going to have to agree with you there. Let's continue to troubleshoot.

I totally agree with the methodology and math. Friction and other modifiers only affect the absolute results for a single vehicle. furthermore, whatever it is that ultimately is found to account for that, is something that also eludes detection and reporting via codes or MILs.

That's what I originally thought.

 

[CaptainXL]

Is that temp difference on a cold or warm engine?

It depends on the outside air temp and weather your at idle or not. The hotter the outside air and the slower you are moving the greater the discrepancy. I thought about moving the IAT closer to the front of the vehicle but that would require a ram air intake which I am not going to invest in. Now here is the kicker. We have an outside air temp sensor. Whether or not GM decided to use it to calibrate the IAT sensor is unknown. All I know is that when the truck is idle and it is hot outside the IAT swings to the hot side noticeably greater than the outside ambient temp. Could be a result of under hood heat as it is directly above the exhaust. If it proves that all our IAT sensors function the same (which they should), then the IAT shouldn't be a factor as WarGawd has been suggesting.

 

[C-ya]

To add a little more to that mess, I watched IAT, OAT and the temp display on the climate control console while driving home yesterday. IAT was 90F, OAT was 71F and my display showed 66F. Again, I'm not sure if the PIDs are correct for IAT & OAT or what. I would imagine that GM would do a better job of reading OAT for use in engine control.

 

[Phantom]

0-60 in tenish 0-90 in 21ish
About 85 degrees out during the day. video quality is kinda poor. off my boost phone. Nobody in the truck except me. About a 1/4 to 1/2 tank of fuel.
[video=youtube_share;LCTSFcbCIlQ]http://youtu.be/LCTSFcbCIlQ[/video]


0-60 in 8ish 0-90 in about 19,20ish
41 degrees outside again nobody in the truck except me, and a full tank of gas.
[video=youtube_share;Z95UKlIB9GI]http://youtu.be/Z95UKlIB9GI[/video]

Both videos were taken in the same exact spot.

 

[WarGawd]

0-60 in tenish 0-90 in 21ish
About 85 degrees out during the day. video quality is kinda poor. off my boost phone. Nobody in the truck except me. About a 1/4 to 1/2 tank of fuel.
<snip>

0-60 in 8ish 0-90 in about 19,20ish
41 degrees outside again nobody in the truck except me, and a full tank of gas.

<snip>

Both videos were taken in the same exact spot.

Hmmmmmm very interesting. Gotta run to work, back later. A few thoughts:

1) I think you have the 3.73 rear end based on 45mph shift at 6100? Can you confirm?

2) Watching the 2nd vid a few times, it seemed to me like times were still closer to 10/21ish but marginally improved over vid 1...I'm not trying to argue or nitpick, just wondering if others who watch have the same opinion???

3) The temp diff between my video runs and scanner run was about 15C/25F...if temp is making that much of a difference for others, why aren't I seeing someting much bigger myself?? Maybe I need to do a few more...I'll prob be distracted at work all night chewing on this lol.

 

[Voymom]

Hmmmmmm very interesting. Gotta run to work, back later. A few thoughts:

1) I think you have the 3.73 rear end based on 45mph shift at 6100? Can you confirm?

2) Watching the 2nd vid a few times, it seemed to me like times were still closer to 10/21ish but marginally improved over vid 1...I'm not trying to argue or nitpick, just wondering if others who watch have the same opinion???

3) The temp diff between my video runs and scanner run was about 15C/25F...if temp is making that much of a difference for others, why aren't I seeing someting much bigger myself?? Maybe I need to do a few more...I'll prob be distracted at work all night chewing on this lol.

1) Yes we have the 3.73 gears

2) If you watch the second video, and start the count for actual take off which is around 4 seconds and then stop counting or hit pause when he reaches 60, it's 9-ish seconds. 4 seconds(Take off) to 13 seconds(when he hit 60mph) is 9 seconds.

3) I can confirm that I get the same results on cooler days and nights compared to warmer temps. The truck truly takes off like a bat out of hell when the temps are cooler, and when warmer it seems to drag ass a little.

Thought I would chime in lol

 

[CaptainXL]

0-60 in tenish 0-90 in 21ish
About 85 degrees out during the day. video quality is kinda poor. off my boost phone. Nobody in the truck except me. About a 1/4 to 1/2 tank of fuel.


0-60 in 8ish 0-90 in about 19,20ish
41 degrees outside again nobody in the truck except me, and a full tank of gas.

Both videos were taken in the same exact spot.

In the second video I see a 9-10 second time going off the timer on the dash. I don't see any drastic difference here.

 

[Voymom]

In the second video I see a 9-10 second time going off the timer on the dash. I don't see any drastic difference here.

The 1st video shows about 11-12 seconds

the second video is 9-ish seconds. It's not a drastic difference no, but it is nonetheless a difference. And it shows that temperature can play a small role in times and performance.

If you do the video the right way you will see the 8 second result like Mat first stated in his original post. Stop the video at 3 seconds and watch the timer on the truck, Mat goes WOT as soon as the timer hit 15 seconds....he hits 60mph at 23 seconds, just watched it again, so that is an 8 second run compared to a 10-12 second run in 80+ degree weather.

I honestly think we can sit here all day and go back and forth about it, but to me there are just WAY to many variables to go off of other people's times. We all may be full stock, with damn near the same exact trucks, but we will all still run in some way, differently.

But then again we do have the 3.73 gears, which pretty much makes our run a moot point, besides the difference in times with different ambient temps. Uhg I slowly feel myself going crazy lol

 

[gmcman]

[video=facebook;509453809065110]http://www.facebook.com/photo.php?v=509453809065110[/video]

Here is my 0-90. Shift from 1-2 is at 50, then 2-3 at 90. Does the torque converter stall pertain to anything since I don't move from 0 until 2000K rpm or the speedo is sluggish?
Or the tranny is just slow, deep pan at that... it's been tuned for the hardest shift... as for temperature outside, I didn't notice a change.

The video from DenaliHD shows that his 1-2 was extremely fast to get through 600-6000K rpm which shifted at the same 50mph and his 1-2 shift time was fast and soft like a car would shift. My shift from 1-2 throws heads back.

Straight cat back exhaust for me.

Something surely doesn't look right after 5K, looks like it kinda falls asleep. You should be pulling much harder than that in 2nd gear above 4500.

 

[CaptainXL]

But then again we do have the 3.73 gears, which pretty much makes our run a moot point, besides the difference in times with different ambient temps. Uhg I slowly feel myself going crazy lol

I have 3.42 gears and I ran a 10 second 0-60.

 

[gmcman]

Who said an XL with the 4.2L 4x4 with oversized tires and cargo can't run in the 7s? I present: my truck.

[video=youtube;YqktkkHInVc]http://www.youtube.com/watch?v=YqktkkHInVc&feature=plcp[/video]

That's rollin.

Looks like an even 7 or just a tick under. Can you elaborate more on the road, was this level or down a 10% grade...

All seriousness, that's really good if the road was flat for an XL. Really makes me want a tune now if that made such a difference, I understand the exhaust plays a factor but we have a decent setup stock.

 

[Phantom]

All seriousness, that's really good if the road was flat for an XL. Really makes me want a tune now if that made such a difference, I understand the exhaust plays a factor but we have a decent setup stock.[/QUOTE]

I second that, I was telling Tami that I was wondering what it would be like with a tune and the TM gone.

 

[DenaliHD66]

That's rollin.

Looks like an even 7 or just a tick under. Can you elaborate more on the road, was this level or down a 10% grade...

All seriousness, that's really good if the road was flat for an XL. Really makes me want a tune now if that made such a difference, I understand the exhaust plays a factor but we have a decent setup stock.

Was going down a slight grade... 1 or 2 percent perhaps. It was a stretch of highway... best place to get away with speeding around here. If I were to come up the same grade, add maybe 3-4 seconds though.

 

[Voymom]

I just think in order to put this all to rest, we all need to meet up at the 3/4 mile track

 

[WarGawd]

Was going down a slight grade... 1 or 2 percent perhaps. It was a stretch of highway... best place to get away with speeding around here. If I were to come up the same grade, add maybe 3-4 seconds though.

LOL! LMFAO!!!!! That kills me "Hey George, guess what?!?! My truck fell off a cliff, and I went 0-60 in a little over 3 seconds!! :wootwoot: It might take me an hour to drive back up the road to where I fell off, but if I only report the first result, do you think I'll get more chicks?"



Sorry, I just HAD to poke you on that. I mean clearly the AVERAGE of the 2 runs is what would be critically important here. Even if you are correct about the grade and the additional time required for the reverse run, (lets use the 4s difference for sake of argument), your average time would be 9s, way more in line with the results for 3.42 rear ended XL's. Furthermore I highly suspect the grade you assigned would be on the low side. 1-2% is barely perceptible visually. On 1320 ft (1/4 mile) that equates to 25 feet. On a shorter 0-60 run, (I'll guess for now that would be a run of ~ 500 ft, can calculate better later) you'd be talking a drop of around 10 feet (@ 2%) - roughly equivalent to the height of a highway sign!!!. Inconsequential.

I see two possiblities here - your truck will do 0-60 in almost exactly the same time in the reverse direction (at same time /temp/weight etc) OR if your estimate of 3-4 seconds difference is even CLOSE, the grade will be like umm I dunno freakin' HUGE. Either that or your flux capacitor is kicking in well below 88mph!!!

You do see the problem here right?

Watch out Voymom - Ima gunnin fer yew next! heheheh

 

[WarGawd]

@ Voymom - where oh where do I start with you?

You've provided me with so much material, I could do a comedy tour for a year, and not repeat the same joke twice - kinda like Jeff Foxworthy's redneck jokes.

1) Yes we have the 3.73 gears

Noted, tyvm

2) If you watch the second video, and start the count for actual take off which is around 4 seconds and then stop counting or hit pause when he reaches 60, it's 9-ish seconds. 4 seconds(Take off) to 13 seconds(when he hit 60mph) is 9 seconds.

LOL ;-) even though I had to Google it for verification, there's no disputing your math there! I guess my point was having watched it several times, in my opinion the starting point was something just after the 3s mark (video time), and the end point right around 13. I agree it's hard to gain consensus on the exact points, especially from a youtube video, which is why I opened it up for other commentary.

And actually if you watch and listen closely, you can hear Mat hit the throttle just after the DIC time turns over to 14s. Do this: Start at the beginning of the video, and hit the play button. Now as FAST AS YOU CAN, hit pause and look at the DIC timer...repeat this until the very first instant you see the timer display 15s - and you will see the speedo already reads almost 10mph. In video 1, we were able to see the tach needle move by the same method. In my opinion that's the instant we all have to start the timer for comparison.

At the 60mph mark, what I did was watch for the needle to hit 60 square on, and hit pause as fast as I could. Almost every time, the very next frame I see when I hit play the DIC timer turns over to 14s...average human reaction time is pretty close to a quarter second...but if you repeat the excercise several times they will tend to cancel each other out at the beginning and end. So what I see is "just after 14s" to "just before 24s" - so a little more than 9, a little less than 10, for the moment I'm happy to split the difference and call it 9.5 if you're ok with that.

So let's revisit video 1 with the same methodology, except there we use video timer, timed to first instance of detectable tach needle movement: I can repeatedly stop the video showing the tach at ~900rpm, while the video timer is STILL displaying 1s - every time I get it stopped there, the very next frame shows the video time turn to 2s. So this is the starting point here. Those of you from Missouri may appreciate the screen capture:

View attachment 23052

Doing the same at the other end I consistently get the video to stop just as it hits 12s - but the speedo shows a tad under 60mph. Missourians now know better than to doubt me, so this is for stubborn Michigan moms only:

View attachment 23053

I leave it for judicious students to verify that this means the 0-60 run in video 1 took a tiny shade more than 10s...I'll be friendly and not argue for those last couple tenths, let's call it 10s even.

Time difference between run one and run two where hypothetically temp was the only changed variable (oh and ~ 75lbs of gas)?

ZERO POINT FIVE SECONDS! {Slightly less actually, because I can show (yeah, just trust me now) that run 2 was 9.8s and run 1 was 10.2, or 0.4s}

3) I can confirm that I get the same results on cooler days and nights compared to warmer temps. The truck truly takes off like a bat out of hell when the temps are cooler, and when warmer it seems to drag ass a little.

Thought I would chime in lol

That's fine - I always conceded some allowance for some effect due to temperature. I hope now though that you get my earlier point that your perception of the change is a fair bit magnified from the reality.

The 1st video shows about 11-12 seconds

But Mat said 10 - are you arguin with him or with me? Better be him cuz I can back it up baby!

the second video is 9-ish seconds. It's not a drastic difference no, but it is nonetheless a difference. And it shows that temperature can play a small role in times and performance. If you do the video the right way you will see the 8 second result

LOL goofball. What's "the right way"? There's ONLY ONE right way - the way that yields the correct answer. Just so happens to coincide with MY WAY! hehehehe

like Mat first stated in his original post. Stop the video at 3 seconds and watch the timer on the truck, Mat goes WOT as soon as the timer hit 15 seconds....he hits 60mph at 23 seconds, just watched it again, so that is an 8 second run compared to a 10-12 second run in 80+ degree weather.

So when you watched it again, the time changed from 9s to 8s? Or did you just do it "the right way" the second time? LMFAO And now run 1 has a range of "10 - 12" vs previously stated "11-12"??? Mat came in and saw you typing, realized you were disagreeing with HIM and made you change it, didn't he? C'mon admit it!

I honestly think we can sit here all day and go back and forth about it, but to me there are just WAY to many variables to go off of other people's times. We all may be full stock, with damn near the same exact trucks, but we will all still run in some way, differently.

But then again we do have the 3.73 gears, which pretty much makes our run a moot point, besides the difference in times with different ambient temps. Uhg I slowly feel myself going crazy lol

Nooo oh no not at all. {Psssssst Mat, can you still get your money back for the ring and cancel the hall?}

 

[WarGawd]

OK, so I took a pile of potshots at Tami in the name of humor...Tami thanx for being gracious enough not to take offense.

The reason I nitpicked it to death was that we need to refocus on getting CaptainXL useful info. I never wanted to hijack his thread, or turn it into a competition to see whose truck is faster. I was hoping people would post useful comparative data, so he could determine if he has a performance problem or just a perception problem. If the data being supplied is very subjective and highly inaccurate, it doesn't help - it just adds confusion. Phantom supplied examples which were useful, but those became the source of confusion and MISinformation when people fielded wildy varying subjective opinions on the result.

@Tami - I know you're fairly reasonable, and willing to listen. I didn't comment on it above but when you still thought that the time diff was of the order of 2 or 3 seconds but "It's not a drastic difference no, but it is nonetheless a difference" I want to convey that 2 or 3 seconds on a 0-60 run IS a drastic difference. It's why I was shocked when Captain posted his result. It's why people were very surprised to see Denali's 7s video (and jabbing him about nitrous and hills etc).

In the next day or two I hope to post a quick graphic for discussion & illustration, in support of my contention that temp ALONE does not make anywhere near enough difference to account for CaptainXL's performance change. (FWIW it does seem in his case that the change is real & objectively measureable). I believe you will now accept my demonstration above that Phantom didn't really experience the performance change claimed, and that the posted results actually support my claim. However, I also know from Octane's thread your a betting lady...if you don't accept I have a few $$$ to wager on the subject if we can agree to terms!

G'nite folks
Big day of truck work getting done tomorrow

 

[Harpo]

Why dont you all get the tourqe app and use the 0-60 function in that to get to compare apples to apples??.

Every car i had was always running much better like after a summer afternoon rain after the temperature fallen like 10C and the air is slightly moist and more dense and full or oxygen, especially the turbo cars i had.
Nothing strange with that, cooler air = more oxygen hence the INTERCOOLER.

twocents

 

[gmcman]

The reason I nitpicked it to death was that we need to refocus on getting CaptainXL useful info. I never wanted to hijack his thread, or turn it into a competition to see whose truck is faster. I was hoping people would post useful comparative data, so he could determine if he has a performance problem or just a perception problem. If the data being supplied is very subjective and highly inaccurate, it doesn't help - it just adds confusion. Phantom supplied examples which were useful, but those became the source of confusion and MISinformation when people fielded wildy varying subjective opinions on the result.

I think it was a good post, there are many variables here.



I feel temp does indeed play a role, not a terribly huge one but it's definately a factor... anyone who has flown planes can attest to this. Warm humid days compared to cool days is a huge difference in terms of performance and climb rate. The higher the density altitude, the less performance you can expect.

Our engines being normally aspirated rely on outside conditions to provide cylinder fill regardless on how much the pistons suck things inside. My shop teacher way back in the day told us that you can stick a fire hose of fuel into the motor but you need to get the air to burn it and that's where the magic happens.

Anytime you can provide dense, cool air over warm crappy air there will be more air molecules to burn the added fuel which in turn increases power output. This is where an intercooler comes into play on forced induction cooling the heated air from the turbo.

Since our ECM's read the amount of air entering the motor the fuel is automatically proportioned. I would think the same vehicle in Michigan would perform better than one in the Louisiana.....in the summer.


I'm not proficient with our ECM's and their ability to adjust for changing conditions, but is it safe to assume if we are just trolling along for days on end at light to part throttle settings that if we want to perform a random 0-60 time, that the first crack at it will give some unyielding results? Then after a few runs the ECM will be more adapted to these settings and can fine-tune the parameters?


I know I have been easy for times and then one time I needed to roll out and there was a loud growl from the intake and less than satisfying results from my butt-dyno.

 

[CaptainXL]

Why dont you all get the tourqe app and use the 0-60 function in that to get to compare apples to apples??.

Every car i had was always running much better like after a summer afternoon rain after the temperature fallen like 10C and the air is slightly moist and more dense and full or oxygen, especially the turbo cars i had.
Nothing strange with that, cooler air = more oxygen hence the INTERCOOLER.

twocents

Warmer air would lead to preignition if I am not mistaken and the pcm would retard timing. This is exactly the type of thing that it seems to be...ignition related. I am going to try some premium gas and see what happens. I think this might lead somewhere.

 

[Phantom]

Nooo oh no not at all. {Psssssst Mat, can you still get your money back for the ring and cancel the hall?}[/QUOTE]

COMPLETELY UNCALLED FOR. Don't care if it was a joke or not. I didn't like it one bit.

 

[gmcman]

Warmer air would lead to preignition if I am not mistaken and the pcm would retard timing. This is exactly the type of thing that it seems to be...ignition related. I am going to try some premium gas and see what happens. I think this might lead somewhere.

That's what the 44K will clean up when you get it. Late to get it out since it can't go by air and the USPS sends most through the airlines. Carbon deposits can and will lead to preignition for sure, hopefully we can cross one variable out if it works or not.

I find mine runs well on 89 even though it's engineered for 87.

 

[Voymom]

OK, so I took a pile of potshots at Tami in the name of humor...Tami thanx for being gracious enough not to take offense.

The reason I nitpicked it to death was that we need to refocus on getting CaptainXL useful info. I never wanted to hijack his thread, or turn it into a competition to see whose truck is faster. I was hoping people would post useful comparative data, so he could determine if he has a performance problem or just a perception problem. If the data being supplied is very subjective and highly inaccurate, it doesn't help - it just adds confusion. Phantom supplied examples which were useful, but those became the source of confusion and MISinformation when people fielded wildy varying subjective opinions on the result.

@Tami - I know you're fairly reasonable, and willing to listen. I didn't comment on it above but when you still thought that the time diff was of the order of 2 or 3 seconds but "It's not a drastic difference no, but it is nonetheless a difference" I want to convey that 2 or 3 seconds on a 0-60 run IS a drastic difference. It's why I was shocked when Captain posted his result. It's why people were very surprised to see Denali's 7s video (and jabbing him about nitrous and hills etc).

In the next day or two I hope to post a quick graphic for discussion & illustration, in support of my contention that temp ALONE does not make anywhere near enough difference to account for CaptainXL's performance change. (FWIW it does seem in his case that the change is real & objectively measureable). I believe you will now accept my demonstration above that Phantom didn't really experience the performance change claimed, and that the posted results actually support my claim. However, I also know from Octane's thread your a betting lady...if you don't accept I have a few $$$ to wager on the subject if we can agree to terms!

G'nite folks
Big day of truck work getting done tomorrow

I'm usually a pretty easy going person, but a few things you said were uncalled for. If our video's and advise are not helpful here there is an easier way to go about telling someone.