5.3L Tune vs. no tune

[Mooseman]

I've had a tuned PCM and TCM from Lime Swap for some time in the Saab. Although I loved the performance, I hated the 13 MPG I was getting. Well, I still have the spare PCM/TCM and thought I'd try it with the stock tune just to compare. I had replaced all the valvetrain and cam to a non-DOD version and no VLOM so I knew I would get a CEL for the missing DOD hardware as well as the electro-viscous fan clutch (now thermal).

So what happened? It was an absolute dog! No power, shifted like a granny, revved like there was a rubber band on the throttle and just no power. Strange thing though, the intake made more noise (I don't have a resonator) and the knocking noise that had been plaguing this engine for some time was gone. I thought I had some sort of problem with the bottom end but winds up being just regular engine knock with the tuned PCM. Funny that the PCM doesn't retard the timing to stop it.

It was so terrible that I swapped my tuned PCM/TCM back right away! If I would have driven any longer on the stock tune, I would have driven it over a cliff. As for the knocking, I might get in contact with Jeremy to see if it can be fixed but in the meanwhile, I'll try mid-grade and premium fuel. If my MPG get better, it might compensate for the more expensive fuel.

 

[mrrsm]

Not knowing how long the Tuned PCM stayed inside of the Saab or how many miles you have put on the vehicle since removing the OEM PCM and swapping it out... My first guess would be... Try a CASE Relearn... as the later, worn in Crankshaft Angle may have changed just enough to throw off the original PCM settings and once back in there... it might be a tad confused from its previous legacy setting still kept inside since the day it was removed.

 

[littleblazer]

I wonder if it's just the advanced timing tables causing the knock. You try super?

 

[djthumper]

This is the very reason I have thought to get myself setup with HPTuners.

 

[Mooseman]

Not knowing how long the Tuned PCM stayed inside of the Saab or how many miles you have put on the vehicle since removing the OEM PCM and swapping it out... My first guess would be... Try a CASE Relearn... as the later, worn in Crankshaft Angle may have changed just enough to throw off the original PCM settings and once back in there... it might be a tad confused from its previous legacy setting still kept inside since the day it was removed.

This PCM had been in service in this vehicle while the original was gone to get tuned and was already CASE learned, however, just to eliminate that possibility, I did another one, no change. All else being equal, all I can say is that the stock programming just sucks.

I wonder if it's just the advanced timing tables causing the knock. You try super?

Not yet but planning on trying it this weekend.

This is the very reason I have thought to get myself setup with HPTuners.

Me too except it would be a big learning curve. I would have no idea where to start. Maybe once I'm retired I'd have the time to learn this stuff.

Thinking back, when I first installed the tuned PCM, I remember this beast just waking up it was such a change. I took off and lost traction on dry pavement where it never did before. I also remember that it pinged and knocked badly until it learned this engine and calmed down. Just that little bit of knock that crept back but didn't really notice until much later. The sound was so low, I thought it was the valvetrain so I replaced everything. Despite a new valvetrain and cleaned up heads and so on, the knock was still there so I thought it was piston slap or something else mechanical. Now I know it was just ignition knock.

One thing is certain, I am never going back to a stock tune.

 

[djthumper]

You can back up your current config and tweak it to see what you gain or lose.

 

[Mounce]

Makes me want to get my truck tuned...

 

[littleblazer]

I have bad experiences with ls based tunes so.... But I also want hptuners

 

[Reprise]

Me too except it would be a big learning curve. I would have no idea where to start. Maybe once I'm retired I'd have the time to learn this stuff.

From what I've read of your posts the past couple of years, I'm pretty sure you'd get the hang of it without too much trouble. Just make a couple copies of the original so you can reestablish baseline when needed.

Tuning programs were made for the tinkerer - and there's gotta be info online on a good starting point for a 3rd-gen LS tune.

Actually, looking back in this thread, that would be a modified 4th-gen, since you had DoD on it originally. I'm sure it's there, just the same.

The nice thing is, you could probably use it on the PPV Caprice as well (might need a second license file.)

 

[Mooseman]

From what I've read of your posts the past couple of years, I'm pretty sure you'd get the hang of it without too much trouble.

I know I can, just the time and research to learn a new thing.

The nice thing is, you could probably use it on the PPV Caprice as well (might need a second license file.)

True except that I will be doing a lot more mods on this one with headers along with a new exhaust system as well as a hotter cam. Will probably also change gearing. All that will require a real dyno tune.

BTW, for you 4,2 guys, the changes aren't as dramatic and I actually lost 2 MPG on my '07. I mainly did it to delete SAIS, fan codes, TCC PWM and torque management. With torque management gone, it made it more responsive and that's about it. Still worth it though. I may need to look into that 2 MPG loss.

 

[Reprise]

as well as a hotter cam

If you manage to do a writeup on this, it would come in useful for when I swap mine out someday (just a mild one for towing, I swear!)

 

[littleblazer]

Cam swaps are fun. I don't know how they are on ls engines. All I know is generally the heads need to come off. I know a sbc can probably be done in a day or two I'd imagine this is about the same.

 

[Mounce]

Nah heads don't HAVE to come off. Pull rockers, spin the cam, stick in some dowels to hold the lifters up, r&r the cam and reassemble. Pretty simple but still a load of work

 

[littleblazer]

I thought the dowel option came much later? I don't have good luck with things holding so if still probably pull the head as with my luck there would be a lifter in the oil pan second the cam came out.

If I had to guess on a sbc with normal v belts you could probably do the swap in an hour or two. 12 intake bolts water pump and pull the timing cover. Valve cover off rocker arms push rods then lifters unbolt the cam gear and out the cam comes. Most of the week on the vette was spent getting the damn serpentine accessories and efans out. Intake was fast. Oil pan was quick but a pain on the garage floor. I've never torn into an ls engine but from just looking at it it looks like it's more annoying but I could be wrong. Certain aspects are much better though. Both are probably much better then dohc or quad cams. I grew up on boats and they're all carbed with thunderbolt 4 ignition. I'm young but learned old-school because that's what we had. Yea I'm weird. I have no issues with anything I'm pretty easy going.

 

[HARDTRAILZ]

I can not imagine driving an LS without a tune.

 

[Mooseman]

Update. Drove it to Lindsay ON, about 5 hours away, mostly highway, it did almost 16MPG on a tank of about 75% reg and 25% premium. Had gauges up on Torque and saw up to 3.5 deg. knock retard whenever I would accelerate. It took about 3/4 of a tank to get there. Filled with premium on a quarter tank, so this leaves only about 12% reg. The drive back showed no knock retard except a tiny 0.2 deg. on moderate acceleration and used only half a tank. I haven't filled it yet but going to work tonight I will and get a hard MPG number.

As for the knocking noise, it didn't change. So there is something in the bottom end. It manifests itself only between 2 - 4000 RPM while accelerating moderately. I did notice a little bit under 2000 RPM when decelerating on cruise on slight downgrades. I have a feeling it's piston slap on the right side. It doesn't sound deep down in the engine, almost in the head. I'm not looking to fix it.

 

[littleblazer]

Even if it's a wrist pin it'll run forever like that too.

 

[Mooseman]

Even if it's a wrist pin it'll run forever like that too.

Thought of that too. If it blows up, so be it. It's now relegated to wintet beater status.

Filled it tonight, nearly fell on my ass. I got 18.7 MPG, best ever even when it had DoD! Although this was mostly highway, the real test will be city where I was getting 13 MPG. I will report later.

 

[Kelly@PCMofNC]

Generally these motors are kind of knock sensitive. Even on the stock tune with 87 they will want to ping. It's best if you can commit to premium if you are going to have it tuned, that gives the tuner some room to grow. Almost always we find that the added MPG we pick up offsets the cost of the gas anyway.

If it is still pinging, it may have too much timing in that one area that needs toned down a bit. You can also try to Sea Foam it if you have not already. If there are a lot of carbon build ups this can make it even more knock sensitive.

 

[Mike534x]

Generally these motors are kind of knock sensitive. Even on the stock tune with 87 they will want to ping. It's best if you can commit to premium if you are going to have it tuned, that gives the tuner some room to grow. Almost always we find that the added MPG we pick up offsets the cost of the gas anyway.

If it is still pinging, it may have too much timing in that one area that needs toned down a bit. You can also try to Sea Foam it if you have not already. If there are a lot of carbon build ups this can make it even more knock sensitive.

What kind of gains would there be switching to premium once the custom tune is flashed? I'm running 87 currently on my tune, so I'm mostly curious on what to expect if I make the switch and have the PCM reflashed.

 

[Mooseman]

Well, after my last fill after city driving, I'm at my usual 13 MPG so no gains there. Maybe I just had the wind in my back on the highway drive home. I just did another premium fill and will see how it goes.

Regardless of MPG, tunes on the 5.3 really wake these beasts up. I was reminded how much of a dog it was when I put my spare PCM back trying to see if my MPG would improve. I didn't care at this point it was that bad I switched it back right away.

 

[Kelly@PCMofNC]

What kind of gains would there be switching to premium once the custom tune is flashed? I'm running 87 currently on my tune, so I'm mostly curious on what to expect if I make the switch and have the PCM reflashed.

Usually on the V8's running 93, we are able to pick up a good 15-20hp. It makes a remarkable difference...not just going WOT, but you notice it in little areas like part throttle passing someone as well. Just a lot more punchy and responsive. I'm biased obviously, lol, any time I get a new vehicle it doesn't sit in the driveway 10 mins before we are fiddling with the tune I can't stand them stock anymore. The transmission stands to gain quite a bit as well with a 'real' shift pattern vs. what GM sends them out the door with!