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Boost and iac issues

esmth said:
That first video behavior is the exact same as mine when my (+t) throttle stop and tps was mis-adjusted. IIRC I opened the blade prop screw like a quarter turn or two more than the closed tps switch spec and it helped considerably. Have you started by setting the throttle stop/tps to green book spec? got the feeler blades out? Winging it doesn't work well.

What it looks like to me is lh is making the fuel rich during the pull as per usual, then when you tip-out the throttle the lack of air and too much fuel kill/almost kill it.

Is the MAF/AMM pre turbo?
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we have checked and adjusted the throttle body to greenbook specs, it's also been through multiple throttle bodies and tps I've the last couple years while chasing this issue.

the maf is pre turbo and I have added 2 90 bends aswell cause I read the 90 bends help with air velocity or something along those lines
 
VB242 said:
Do any of your setups recirc the blow off air? I thought that with my lh2.2 setup that with the blow off valve venting to atmosphere, it was letting the turbo still draw air through the amm and make the car rich until the throttle plate opened again or the turbo slowed down. I think if the blow off air is recirculated back into the turbo intake it would slow down the air coming through the amm to prevent that happening. I ended up with MS and no longer have that problem.
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mines the stock style cbv, it doesn't vent to atmosphere
 
gsellstr said:
I agree, the first video is exactly what mine is doing as well, and watching AFR's, it goes pig right, engine almost dies, and as the AFR's lean back out it comes back. I've just learned to baby it coming off the throttle, for now.

The IAC is controlled based on TPS setting, so if the engine rpm is above idle speed, and the TPS is open, the IAC is deactivated. Once the TPS closes, the IAC becomes active again. You can set how many steps the IAC stays open in it's 'off' position, but I've not found that to be of much help in this issue.
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I've learnt to live with it and have adjusted my driving style to compensate but it's auto so it's alot easier, it will be manual soon and I know this issue is going to become really annoying that's why I'm back at it again trying to finally figure out a solution haha
 
sorry for the slow replies, I'm in Australia so all you guys started commenting right when I was going to bed haha

I'm absolutely lost with this issue, when it first happened I was like oh OK this will be a simple issue it will be a badly adjusted throttle body or something simple along those lines, fast forward 2 years and me replacing every damn part I can and I'm still chasing this "simple" issue haha..

the most progress I've mad in 2 years is running it with the iac disconnected, instantly no stumble and I can snap that throttle shut all day long but then I have a high and ****ty hunting idle, I feel like I'm so close yet still so far away from a solution.
the best idea we have come up with is the timer relay to cut power to the iac, it's not ideal and not actually addressing the problem but it should work in theory
 
I don't see these problems with my rebuilt B21FT that's been converted to LH2.4 ('937 ECU / '148 EZK, 15G @ ~8psi), and I'm pretty fussy about how I expect the engine to run. I can only remember once in the last couple years where it even threatened to stall (and that was during warmup and an abrupt stop, so not entirely unexpected). I have an AW71, and don't usually push it, so maybe I'm just too gentle to see the issue?

I don't understand why it would go "pig rich" on decel -- the MAF is measuring the air coming in and unless there's a blowoff valve, or big leak, the AFRs should be well controlled. What do you have for a PCV setup and any chance that the extra air is blowing out of the PCV on rapid decel?

I'm still slowly working on my LH2.4 logger project. If you have the paid version of MegaLog Viewer, you can pull in my logs and see what my engine is doing (the logs are way too big for the free version). Dropbox link.
 
bobxyz said:
I don't see these problems with my rebuilt B21FT that's been converted to LH2.4 ('937 ECU / '148 EZK, 15G @ ~8psi), and I'm pretty fussy about how I expect the engine to run. I can only remember once in the last couple years where it even threatened to stall (and that was during warmup and an abrupt stop, so not entirely unexpected). I have an AW71, and don't usually push it, so maybe I'm just too gentle to see the issue?

I don't understand why it would go "pig rich" on decel -- the MAF is measuring the air coming in and unless there's a blowoff valve, or big leak, the AFRs should be well controlled. What do you have for a PCV setup and any chance that the extra air is blowing out of the PCV on rapid decel?

I'm still slowly working on my LH2.4 logger project. If you have the paid version of MegaLog Viewer, you can pull in my logs and see what my engine is doing (the logs are way too big for the free version). Dropbox link.
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my pvc setup is yoshifab block vent and oil cap too catch can and back pre turbo.. it did this back when I had the stock pvc system too.
we have boost leak checked it and checked for vac leaks many times
 
I think it's related to the decel fuel cut aspect of things, combined with the larger MAF and injectors. I haven't been able to put a finger on the root cause at all, but there's also several tables in the fuel map that are unknown, could be something there that's not liking anything on the larger size for fuel. For reference, I'm on the 012 MAF and #80's.
 
gsellstr said:
I think it's related to the decel fuel cut aspect of things, combined with the larger MAF and injectors. I haven't been able to put a finger on the root cause at all, but there's also several tables in the fuel map that are unknown, could be something there that's not liking anything on the larger size for fuel. For reference, I'm on the 012 MAF and #80's.
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I have the 025 maf and green giant injectors but it used to do it on my standard maf and v70 white injectors
 
cosbySweater said:
Have you tried using a 2.2 throttle body with the adjustment scre on the bottom? You can raise the idle a tad and it helps
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I haven't, I don't particularly want a higher idle, like I will if I have too but I would really just like to figure out a way to fix the damn problem haha
 
I had some strange luck on the 025's, the 012's were more stable. I have tried the 2.2 TB, have it on the car now actually. It's not really any different than setting the throttle plate a touch wider open and readjusting the TPS though, if you need to raise the idle, and it didn't help with the rich stumble coming down.
 
gsellstr said:
I had some strange luck on the 025's, the 012's were more stable. I have tried the 2.2 TB, have it on the car now actually. It's not really any different than setting the throttle plate a touch wider open and readjusting the TPS though, if you need to raise the idle, and it didn't help with the rich stumble coming down.
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025 was the only 3"maf I could find here they are far and few between these days, the car ran alot smoother with the 025 compared to the 016.

this stumble is so annoying, the car runs flawless, it makes good power and pulls hard, Afrs are spot on its just this damn stumble letting it down
 
pigdog said:
025 was the only 3"maf I could find here they are far and few between these days, the car ran alot smoother with the 025 compared to the 016.

this stumble is so annoying, the car runs flawless, it makes good power and pulls hard, Afrs are spot on its just this damn stumble letting it down
Click to expand...

I have a 012 maf I'm selling if you want one to try.
 
have you tuned your ecus to match your current setup?

if not, you're relying on the good graces of lh and its "self learning" abilities... which is nothing more than fuel trims... to handle that for you. That's not always a good bet.

Another thing to check is boost leaks, also where is the MAF located relative to the compressor inlet.

At some point you need to punt and either embrace tuning the stock ecu to suit your specific needs, or get an aftermarket ecu and have a bit more intuitive control over things(maybe, depends on what you get lol).
 
linuxman51 said:
have you tuned your ecus to match your current setup?

if not, you're relying on the good graces of lh and its "self learning" abilities... which is nothing more than fuel trims... to handle that for you. That's not always a good bet.

Another thing to check is boost leaks, also where is the MAF located relative to the compressor inlet.

At some point you need to punt and either embrace tuning the stock ecu to suit your specific needs, or get an aftermarket ecu and have a bit more intuitive control over things(maybe, depends on what you get lol).
Click to expand...


the chips I'm running suit my setup but obviously they were generic chips tuned for someone else's actual car.

tuning the car myself is way out of my league and there's absolutely no tuners here willing to touch lh2.4, it's to much hassle for them.

the end goal is to go aftermarket management but that's a ways away yet.

we have looked for boost leaks and pressure tested the system there's no leaks.

the maf is pre turbo as far away as possible and has 2 90 bends Inbetween the maf and turbo
 
trying to tune it with maf/injector size without touching the ecu/maf translation table is a recipe for disaster, its not 2007 anymore. I'm surprised the return to idle is your only problem tbh
 
esmth said:
trying to tune it with maf/injector size without touching the ecu/maf translation table is a recipe for disaster, its not 2007 anymore. I'm surprised the return to idle is your only problem tbh
Click to expand...

well unfortunately unless I go aftermarket management there's no real options here.
the chips I'm running suit my exact setup and as I said before the car runs flawless, my afrs are spot on everywhere literally the only issue I have is the stumble snapping the throttle shut and I had that issue on a dead stock turbo setup, 13c factory ecu and ezk etc etc.

it's always done it which is what makes no sense to me, if it only just started happening now that i'm craming 18psi down its throat sure I would be looking at the tunes but it hasn't, literally removed everything from a 740t and put it in the 240 and the issue was there. instantly
 
I must say the chips and my setup seem to work perfect together, I run consistent 0-100 in 4.9s and consistent low 13s 1/4miles 13.2 being my best to date..
I can live with the stumble and have learnt to compansate for it but I would really like to find a solution I'm not ready to fork out for aftermarket management this is just my daily driver I'm absolutely happy with where it's at apart from my 1 issue.
 
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