Tuning out stalling problem with SAFC

[SlimLim]

Hi,

My car keeps stalling, when warm, after i let go of the accelerator. I want to fix this problem. I don't have access to a wideband currently, as i used somebody elses.

The car has a AFPR at 35psi base fuel pressure. I'm using the stock 440's with a lex AFM with tuning screw that it about 1/4 turned. We have tuned the car so that boost cut still kicks in at around 19psi. It is boosted to 17.5psi on a Blitz BAG hi flow turbo.

I have had my SAFC tuned on Hi-throttle (65&#37 with no changes made to the lo-throttle setting (10%). It was tuned at around 11.5 afr's across the board. I want to know if increasing the lo-throttle to a value of 25% would help solve the problem, and if so, will it be safe doing so?

And yes, my bov is plumbed back.

Any help regarding the stalling issue would be great.


Regards


Nick

edit: Actually i think the AFPR is more towards 40psi. It idles perfectly fine. If i could just get the car to operate like it does when colder, and hold its idle, that would be great.

 

[grimreaper]

how is the bov routed? if its vented, the safc will not allow you to tune this issue out

 

[suprahero]

I've never heard anything good coming form the Lexus AFM and 440's. You should be running lean all the time.

My bov was blowing into the atomosphere and I never had stalling problems, but I also had 550's. I don't know what your problem is, but I do know you're getting 25% more air and the same amount of fuel as stock.

 

[SlimLim]

The bov is plumbed back, which is not venting to atmosphere. It's something else.

Wouldn't raising the fuel pressure compensate for the larger AFM?

 

[supramad77]

I get the same problem on mine two. I have the lexus afm and 550's with safcii fitted on a auto car. Mine stall on decelaration at junctions and roundabouts. Not alwasy but when you least expect it. Been like it more than a year now and no one seems to have an idea why.

 

[speedfreak426]

John Lunsford and his 7m celica are running lex AFM and stock injectors @ 37psi of fuel pressure


http://jblmk3.com/cars/pt_upgrade.php <<--- near the bottom of the page

quote from his site

"I took advantage of having the actuator off so I painted it so it would look new too. This is the turbo that I made 437 RWHP/469 RWTQ at 18 psi with! I used the stock intercooler with PVC pipes, stock fuel injectors, no fuel computers, Walbro GSS-315 and SX AFPR at 37 psi, 12 deg timing, no race fuel, no tricks on a hot rainy day!"


What do you guys think about this? His car seems to run pretty damn good and he isn't even running an afc, he is venting to atm. too!

 

[nhum]

I too have that same problem. There's an adjustment on the S-AFC for Dec Air. It supposed to componsate for blow off valves that are vented to the atmosphere and should stop the car from stalling. I could never get it to solve the problem. But one of my friend had the same set up, Lex AFM, 550 injectors, K & N intake system, factory FPR. His car never stalls! Mine is an 89 5spd his is a 91. Figure this one out.

 

[grimreaper]

if you read the manual that is for a hot wire setup...

 

[isnms]

Everyone that starts trying to defend 440/Lex combo always points to John.
Well you're not John.
If you were you would not be making post like; I'm running lean or I'm stalling or I blew my...

Read these and do it right and do it safe:
http://suprasonic.org/lexusriemer/lexusnotes.html
http://rob.carlile.home.mchsi.com/lexus/lexus1.htm

 

[suprahilux]

grim., I think you need to read through that again. The karman is included.:icon_bigg

Back to the problem. First of all, I would suggest that you swap to the 550 injectors so that you get the fuel that your engine needs. I bet your neo is adjusted WAY up (20-25%) to compensate for the lack of fuel, essentially defeating the purpose of the lex afm. Also, the fuel pressure you are running is not going to compensate for the air flow of the lex afm.

Yeah, I was able to turn up boost by letting air in behind the afm(about as much as a lex), got 17psi. Melted a HG. I was lucky. Wouldn't try that again.

For the stalling problem: After you fix your injector issue. If you are not using the decel air function, I would attribute your stalling prob to the improperly adjusted partial-throttle settings. That is one part of tuning that is commonly overlooked by tuners. I personally would use the decel air function whether I am venting or not.

 

[Poodles]

John is paid to tune other people's cars, so if he did it, it's because of his expert tuning. It's not a stable setup and never will be...

Back to the topic at hand, check your dashpot...

 

[grimreaper]

id like to know how its setup then as nothing ive read supports it working on a karmen system

 

[suprahilux]

id like to know how its setup then as nothing ive read supports it working on a karmen system

Taken from p23 of 'my' neo user manual:

"If the throttle is rapidly released on a vehicle with a hot wire and Karman turbo air-
flow signals, the engine may be stalled by blow-back. "

Then..

"If the throttle opening goes less than the value set by“Dec Air”at a rotation speed
lower than“Air Map”engine rotation speed“Ne 02,”airflow signals that are higher than
the airflow usage ratio (or Karman turbo frequency) set in“Dec Air”are not output.
This is to stabilize the airflow signals. "

However, I just got off the phone with apexi and they said it WAS a feature for the neo with karman signals, but they were having problems so instead of fixing the problem, they omitted it from the program. So I am right about the ealry neo software, but you are right about the later version. They did change the manual on their website and it does not mention the karman sensor in the decel air.

 

[grimreaper]

^ sounds good, SAFC and SAFC II do not allow adjustment of the NE1 and NE2 points in anything except air flow percentage making it a guess to pick the right points on them. The neo lets you select actual hz readings for these two points?

OP you said you have a safc, assuming thats a SAFC I, then there is nothing you can do with it (apart from guessing) to set the decel air unless you find a chart that compares Hz to air flow percentage...

 

[suprahilux]

the neo tunes decel air in airflow percent just as the previous units.

I asked the guy at apexi if they were trying to fix the problem with decel air, he said not to hold your breath. He even suggested to get the safc2 unit instead. I guess they don't hold it to be very important. I sure would like to have that function working properly on my neo.

BTW if your neo software version is prior to 1.104 then your neo has karman sensor input errors. Most people don't notice the problem. You can send it in to have it reprogrammed.

 

[tekdeus]

Would be nice to find a way to use the SAFC to improve the stumbling/stalling problem. Even when my BOV is recirculated it sometimes stalls. Can't figure out why after lots of reading, testing for boost leaks, etc.

 

[grimreaper]

^ your not alone! Mine doesnt stall anymore, but stumbles down to 5-550 rpms once its fully warmed up

 

[supramad77]

Yea mine is just the same with a safcii wired in. Just had some tuning done an a rolling road to sort out over fueling and timing issues but that dam stalling still happens every so often and if not stalling the revs dropping to around 550rpm.

 

[grimreaper]

I think its the modifications stacked on top of a stock ecu. If i let it engine brake to below 1500 rpms it will usually hit 750rpms solidly and drop slowly to 650rpms.