Need help with twin turbo LS2 tune

[camcojb]

OK, I got the stock motor tuned well with the twin turbo kit and 8 psi of boost. But I have a 402 turbo-specific engine sitting here so I installed it this weekend.

I have the 15000HZ patch in. As soon as I go WOT the HZ jump to 12700-13000 or so. The car doesn't shut off but acts like it has a rev limiter on it. The rpms in this case were about 4800 but it won't accelerate, just barely speeds up.

A/F is not completed yet, but at WOT was 12:1 or so. Boost was only hitting 9 psi as the engine won't accelerate at all.

With the 15000HZ patch you still have nothing past 12200 hz to tune with. Seems like too much of a coincidence that this is exactly where I am having problems.

Has anyone here tuned an LS2 with a maf past 12500 HZ or so? Is it possible that since I am exceeding the maf table it is limiting the engine?

Jody

[camcojb]

Dropped the boost as low as it would go (8 psi) and it seemed fine, though my maf lb/min maxes at 61.04 and stays there throughout the run. That equates to 462.42 g/sec, but it appears maxed to me as it doesn't wiggle one bit during the run even though the rpms climb.

If I go to any more boost the car breaks up and does the "limiter" thing. I can't meet the max 512 g/sec because the maf lb/min locks up at 61.04, but I'm sure something in here is the issue. With the extra boost (1-2 psi) it breaks up, lb/min still stops at 61.04. But the bank 1 O2 goes lean off/on, the HZ have spikes down to almost 0 from a high of nearly 15000.

Does this sound like a maxed maf issue? Is there a way to fix it with an extender? Is the max of 61.04 on the maf lb/min a symptom of a maxed something, or just as high as it can read?

Here's the two logs.

Jody

[BLOWNZO6]

You have a few problems.

1. The car never shows WOT. I can see where you have it floored but the car is showing 88% or less at what you think is WOT.

2. The car does not appear to be entering PE. You have it floored the car is still in FTC 15, which is not open loop.. so I don't think you are going into PE.

Not sure what a 15000 HZ mod is... something with the LS2 setup? As far as I have done you can only scale the maf to 512 g/s. You are pegging the MAF, which is fine. The reason the car is breaking up like it is, is because the MAF is pegged and the car is still trying to calculate from the MAF, but it cannot. You have to get the car into PE if you are pegging the MAF.

Do you have a wideband?
Did you adjust the cylinder volume in the calculations?

Start there and see if you have any questions. If you send me you bin file I will look at it for you.

Nick

[camcojb]

You have a few problems.

1. The car never shows WOT. I can see where you have it floored but the car is showing 88% or less at what you think is WOT.

2. The car does not appear to be entering PE. You have it floored the car is still in FTC 15, which is not open loop.. so I don't think you are going into PE.

Not sure what a 15000 HZ mod is... something with the LS2 setup? As far as I have done you can only scale the maf to 512 g/s. You are pegging the MAF, which is fine. The reason the car is breaking up like it is, is because the MAF is pegged and the car is still trying to calculate from the MAF, but it cannot. You have to get the car into PE if you are pegging the MAF.

Do you have a wideband?
Did you adjust the cylinder volume in the calculations?

Start there and see if you have any questions. If you send me you bin file I will look at it for you.

Nick

The LS2's only show 88%. You can read it a different way to show 100%, but 88% is WOT. The 15000 patch is to extend the ls2 maf.

How do I get it into PE? I do have a handheld and in-car wideband, A/F is showing 11.8-12:1. I forgot to change the cyl calcs, I will do that.

Sure wish I could dump this friggen maf!

Jody

[BLOWNZO6]

The LS2's only show 88%. You can read it a different way to show 100%, but 88% is WOT. The 15000 patch is to extend the ls2 maf.

How do I get it into PE? I do have a handheld and in-car wideband, A/F is howing 11.8-12:1. I forgot to change the cyl calcs, I will do that.

Sure wish I could dump this friggen maf!

Jody

Ok.. that makes sense if the LS2 only shows 88... sorry I have only done LS1 stuff. Same with the 15000 patch...

Don't know why you really need it though. If the MAF will still only read to 512 g/s you are really wasting your time.. you will still peg the MAF.

You need to check at what parameters the car is set to go into PE. You can check it in the fuel section of the table. It is under fuel control and power enrichment.

I guess you cannot do 2 bar on an LS2 yet?

I have it on my ZO6 and it is VERY nice with the Twin Turbo setup.

[camcojb]

Yeah, no 2 bar for the LS2's yet. Before I did the maf patch the car would shut off when it pegged. Now it acts like a rev limiter and breaks up, but guess it's still doing the same thing?

According to everything I see in the PE area it should be wot. I mean the trims 0 out, etc. so I assumed it knew it's wot.

Guess I need to either figure out how to extend/trick the maf, or give up on this project, as 8 psi on an 8:1 402 is not enough. It's a bummer as there's several maf extenders and re-scaled mafs for the Fords.

Thanks for the input, much appreciated!

Jody

[BLOWNZO6]

Yeah, no 2 bar for the LS2's yet. Before I did the maf patch the car would shut off when it pegged. Now it acts like a rev limiter and breaks up, but guess it's still doing the same thing?

According to everything I see in the PE area it should be wot. I mean the trims 0 out, etc. so I assumed it knew it's wot.

Guess I need to either figure out how to extend/trick the maf, or give up on this project, as 8 psi on an 8:1 402 is not enough. It's a bummer as there's several maf extenders and re-scaled mafs for the Fords.

Thanks for the input, much appreciated!

Jody

Send me the file to [email protected] and I can see if anything stands out.

Something you are just missing... there is no reason I can think of for it not to work.

[camcojb]

I just e-mailed it to you, but I thought if the MAF was pegged you're done.

Thanks again!

Jody

[Chris@HPTuners]

what is your MAF fail freq set at (its under Engine Diagnostics)? It should be set higher than the highest frequency you see on the MAF otherwise the ECM will switch to the VE table causing a major leanout.

Usually on LS2's it is set at 13500 which you are probably exceeding.

Chris...

[camcojb]

what is your MAF fail freq set at (its under Engine Diagnostics)? It should be set higher than the highest frequency you see on the MAF otherwise the ECM will switch to the VE table causing a major leanout.

Usually on LS2's it is set at 13500 which you are probably exceeding.

Chris...

Yes, it is set at 13500, and yes I am exceeding it with any more than 8 psi. It allows a max of 16384 HZ so I will change that. But won't it go to "0" at 15000 with your patch anyway, or will it hold the last numbers seen to 16384?

Is there anyone who can tune these for bigger power yet, and are there any solutions for these maf's to extend them?

Is there 2 bar SD tuning for the LS2's even on the horizon for some beta guys?

Jody

[camcojb]

Well, short of finding a way to extend the maf readings 10 psi is at the limit with this 402. When I go to 11.5 psi it maxes the g/cyl and the MAF HZ.

Kind of a bummer having a motor that can run 18 psi or more and be limited by tuning to 10 psi (and probably should be dropped to 8 or 9 as 10 hits too close to the limits). When I built this engine I knew HPTuners was going to have the LS2 tuning. I did not know they wouldn't have 2 bar speed density with it though. Not blaming them at all, Chris and Keith have been great. I didn't ask the right questions!

Jody

[QuickSilver2002]

Well, short of finding a way to extend the maf readings 10 psi is at the limit with this 402. When I go to 11.5 psi it maxes the g/cyl and the MAF HZ.

Kind of a bummer having a motor that can run 18 psi or more and be limited by tuning to 10 psi (and probably should be dropped to 8 or 9 as 10 hits too close to the limits). When I built this engine I knew HPTuners was going to have the LS2 tuning. I did not know they wouldn't have 2 bar speed density with it though. Not blaming them at all, Chris and Keith have been great. I didn't ask the right questions!

Jody

Hey camcojb, i recognize you from the GTO board. I just got HPTuners for my ls2 and I'm trying to figure out a few things myself for my upcoming Gen TT project (i'm on there as lsxfanatic). I've done lots of ls1 stuff but the ls2 is new to me.

I don't think you are as limited as you think, although I have no experience on the ls2 yet.

First, I would try disabling P0103 (the maf high DTC).

If you can just get the last airflow to hold you will be able to do the rest of your tuning in PE vs RPM. Although not ideal, you can still tune around a static maf reading up top.

If the PCM does not do it for you, you could find a frequency clamping device that would hold you at 16000 Hz. Don’t give up yet.


And here is some additional info I found while searching on here. You may already have this done.

Also, you'll need to check out the Engine Diagnotics seciton and set the P121,101 values so those tests don’t run and the P0068 enable RPM. Finally, go to the DTC list and set P0108 to 3 - No Error Reported

From what I have read, the patch is just a bug fix that GM made for some type of quirk where the frequency would drop off for a second. I don't think the patch actually extends the maf frequency range or adds any tuning ability. You will need to tune in PE once the maf hits the limit (if the max reading holds).

[camcojb]

I can shut off the P103 dtc, but I've never got a dtc light for that. Above 10 psi I am at 1.2 g/cyl which I am told is the end. I'm hearing you can tune through PE beyond that, but have not figured out how yet.

Jody

[QuickSilver2002]

I can shut off the P103 dtc, but I've never got a dtc light for that. Above 10 psi I am at 1.2 g/cyl which I am told is the end. I'm hearing you can tune through PE beyond that, but have not figured out how yet.

Jody

Yea, sometimes the code never sets even though it impacts the tune.

1.2 g/cyl may be the limit but it does not really matter. The 512 g/sec limit has always been on the ls1. Your g/cyl will actually start going down as RPMs go up once the maf maxes out.

The trick is to find the spot where it stops moving and then you start adding fuel in PE vs RPM.

[camcojb]

Yea, sometimes the code never sets even though it impacts the tune.

1.2 g/cyl may be the limit but it does not really matter. The 512 g/sec limit has always been on the ls1. Your g/cyl will actually start going down as RPMs go up once the maf maxes out.

The trick is to find the spot where it stops moving and then you start adding fuel in PE vs RPM.

OK, I'll keep playing. Thanks!

Jody

[EC_Tune]

Jody,

The 1.2 g/cyl is the limit on the spark table not fuel. You will just end up using the last value on the table so tune spark for Max Boost.
Fuel *should* go to ~2 g/cyl. before limiting out.

A "cheat" i tried (and it works Thanks Chris!) is to drop the VE & the IFR by the same % to effectively give you more "table" to play with. It's not "technically" correct but it works great.

[camcojb]

Jody,

The 1.2 g/cyl is the limit on the spark table not fuel. You will just end up using the last value on the table so tune spark for Max Boost.
Fuel *should* go to ~2 g/cyl. before limiting out.

A "cheat" i tried (and it works Thanks Chris!) is to drop the VE & the IFR by the same % to effectively give you more "table" to play with. It's not "technically" correct but it works great.

Does that work with a blow through maf, since you aren't using the ve? I've been told that once the maf is pegged (as long as it doesn't fail which I hope I have stopped) that you do the rest of the fueling with the PE table. It's been raining here the last couple days so I can't try it to see if the car will run at 12+ psi.

Jody

[QuickSilver2002]

Does that work with a blow through maf, since you aren't using the ve? I've been told that once the maf is pegged (as long as it doesn't fail which I hope I have stopped) that you do the rest of the fueling with the PE table. It's been raining here the last couple days so I can't try it to see if the car will run at 12+ psi.

Jody

I would say that method does not work when in MAF mode. Still not sure about the ls2, but the ls1 was 100% on the maf for the base airflow calcs once over 4k.

I've never had a need to get that granular with the timing under boost. The spark table should give you all the control you need as is.

[SMOKINV8]

Read through this thread to get an idea of another (temporary) work around.
http://www.ls1tech.com/forums/showthread.php?t=471543

You lose some resolution, but it might work for what you're doing until the 2bar is released. Be careful with your trials though, the LS2 PCM might not take quite as kindly to halving the VE table like that.

[camcojb]

Read through this thread to get an idea of another (temporary) work around.
http://www.ls1tech.com/forums/showthread.php?t=471543

You lose some resolution, but it might work for what you're doing until the 2bar is released. Be careful with your trials though, the LS2 PCM might not take quite as kindly to halving the VE table like that.

What I do not understand is how halving the VE table helps on an LS2 at all. It doesn't use it with the MAF. I thought when the maf runs out, and if it doesn't fail it goes to the PE table, not VE table for fuel.

Jody