Car wants to stall with under heavy braking/fast stop!

[Chalky]

Having an issue with with stalling. When coming to a slow stop, car seems to hold desired idle. when I bring speed down quickly and bring the car to a stop, it drops below desired idle rpm, drops down to about 500, tries to catch itself and will die. I am not aware of any other quick decel issues and this only happens with the clutch in at a full stop

I have tried to slow down decay rates in TC and TF but it doesn't make much difference other than now when it does catch, the idle hangs slightly.

All other parts of the idle are fine with no hunting, and smooth engine accel.

Appreciate any suggestions.

[WHYTRYZ06]

tune the idle tables....

B4307
B4309
B4315
B4308

set up some maps to look like these tables, and you'll be in business

I have a very radical setup compared to yours and I tuned these tables and have no problems..

[Bruce Melton]

Float level set too high?:)

[TAQuickness]

sounds like your cracker, maybe the follower, could use a bit more decay delay

[Doc]

What is spark doing during the drop?

[jfpilla]

Try setting B4311 and B4312 to 12 and 11. If it stops doing it then it's likely the TC/TF need work. If it continues it is likely DAF/timing need work.

[Chalky]

Float level set too high?:)

Thanks was it. Thanks Bruce. Damn updraft carb!

[jfpilla]

Thanks was it. Thanks Bruce. Damn updraft carb!

When did Tony start porting 90mm carbshttp://forum.efilive.com/images/icons/icon5.gif

[Chalky]

sounds like your cracker, maybe the follower, could use a bit more decay delay

I tried adding a little at lower rpm and also reduced decay but problem persists.

[Chalky]

What is spark doing during the drop?


Doc:

Just looking at some logs from weekend. Spark seems to hold @ 24* from 900 to <600 rpm. When I add fuel to save from stall, timing drops to 9*

I had a a log going today using air.pid but when car stalled, I lost the end of the log.

[Chalky]

Try setting B4311 and B4312 to 12 and 11. If it stops doing it then it's likely the TC/TF need work. If it continues it is likely DAF/timing need work.

I tried 6&5 today but noticed no difference. Should I raise to 12 and 11?

FWIW, I had the idle so very close before that I ws quite happens. I recently chanegd from a FAST90 back to my LS6 intake and idle issues took a turn for the worse.

[Chalky]

When did Tony start porting 90mm carbshttp://forum.efilive.com/images/icons/icon5.gif

Bruce is his biggest customer! Looking for more power for his 441.

[Chalky]

I didn't realize I had this many replies. I am still not getting post notices.

[jfpilla]

I tried 6&5 today but noticed no difference. Should I raise to 12 and 11?

FWIW, I had the idle so very close before that I ws quite happens. I recently chanegd from a FAST90 back to my LS6 intake and idle issues took a turn for the worse.

Higher will give you a better test. If your too close to stopping there's a chance that the decay is so fast that it will overshoot idle. I actually test at 24 and 23.

You changed manifolds. No leaks?

[Chalky]

Higher will give you a better test. If your too close to stopping there's a chance that the decay is so fast that it will overshoot idle. I actually test at 24 and 23.

You changed manifolds. No leaks?

I busted an ear off my Mamo ported FAST90. I had a whistle and found the front left bolt loose. When to tighten it up with a 1/4" drive ratchet and busted the ear loose. I figured I might as well take it off and put the LS6 back on until I can get it fixed or replaced. I do think my FAST90 was sealing OK after some effort. I also think my LS6 seals up better than my FAST90.

When I throw th FAST90 back on, I am going with fresh runner seals from FAST. Hope that is the last time I have to deal with it. Funny but my FAST90 and LS6 pull same kpa of 95-97 KPA.

OOps. Thought you were inquiring about my FAST90. No leaks with the LS6

[Chalky]

Higher will give you a better test. If your too close to stopping there's a chance that the decay is so fast that it will overshoot idle. I actually test at 24 and 23.

You changed manifolds. No leaks?

BTW, is this the only way to disable TC, using B4312? What I am trying to understand is why you have decay rates for TC after TC is disabled. Wouldn't TF be making air decay adjustments once TC is disabled?

[joecar]

I didn't realize I had this many replies. I am still not getting post notices.The vbulletin software doesn't seem to be sending out email notifications... Andrew(Tordne) is looking into it.

[jfpilla]

BTW, is this the only way to disable TC, using B4312? What I am tring to understand is why you have decay rates for TC after TC is disabled. Wouldn't TF be making air decay adjustments once TC is disabled?

My testing, I try a lot of stuff out of curiousity, has indicated that zeroing the TC table does not turn off the TF. Using the parameters table turns both off. I could be wrong, but that's what I've always observed and would seem logical otherwise you wouldn't need the parameters table, you could just zero the TC.:blahblah:
Try a high number which should make it more obvious. It can't hurt.
Have you done the RAFIG and RAFPN?

[jfpilla]

The vbulletin software doesn't seem to be sending out email notifications... Andrew(Tordne) is looking into it.

I'm getting notices, but out of order.

[joecar]

I pm'd Andrew, thanks for the feedback. :cheers:

[Chalky]

My testing, I try a lot of stuff out of curiousity, has indicated that zeroing the TC table does not turn off the TF. Using the parameters table turns both off. I could be wrong, but that's what I've always observed and would seem logical otherwise you wouldn't need the parameters table, you could just zero the TC.:blahblah:
Try a high number which should make it more obvious. It can't hurt.
Have you done the RAFIG and RAFPN?

RAFIG is right on.

[SSpdDmon]

Emailed you back...

[Chalky]

My testing, I try a lot of stuff out of curiousity, has indicated that zeroing the TC table does not turn off the TF. Using the parameters table turns both off. I could be wrong, but that's what I've always observed and would seem logical otherwise you wouldn't need the parameters table, you could just zero the TC.:blahblah:
Try a high number which should make it more obvious. It can't hurt.
Have you done the RAFIG and RAFPN?

Bumped B43111 aND b4312 TO 12/11 and still no difference. I have a log I ran this morning and let the car die 2/3different times. No doubt, but the more agressive the stop , the worst the stall. I can even accle to 35-40 for example, disengage clutch, hot brakes to slow car and motor will die before I stop.

I even went back to settings I used with my FAST90 for TC/TF and they worked well before.

When I look at TC/TF activity when coasting and waiting for car to die, all TC/Tf acitivity stops by about 3000 and idle comes down. Still trying to understand TC/TF!

[Bruce Melton]

When it goes into the stop funk does it by any chance revert to open loop?

[Chalky]

Bruce:

I am in OL and have been for a while. Car always had a slight tendency to drop idle a little even before I changed back to Ls6 intake. Now it is just worse.

[Bruce Melton]

OOOO, well, then you have to filter the advice which might not apply.

If you have to have good OL AFRs under all conditions then you have a real project.

[Chalky]

OOOO, well, then you have to filter the advice which might not apply.

If you have to have good OL AFRs under all conditions then you have a real project.

Just an idle situation. Just surprised but the cam is not big as you know.

I need to finish up VE and MAF and get back to CL! :)

[Chalky]

Update:

OK, made a few adjustments and now car holds an idle with no drop idle drop off UNTIL car reaches a complete stop and then it stalls. Anything prior to the complete stop and the all is fine. From what I experienced, this also seems to crop up after car reaching full operating temp. I tried some stops prior to car being at operatign temp and had no stalling.

Appreciate any ideas.

[jfpilla]

Chalky,
The TC and TF show no contibution when you decelerate. Your idle should be high enough, to not stall, without them. I would look at DAF.
I've never seen RAFIG lock at 0. Did you turn on the A/C?
Post your tune file, someone may see something.
Joe

[Chalky]

Here you go!

No AC but heat was on Auto!!

[jfpilla]

Here you go!

No AC but heat was on Auto!!

With Corvette, Automatic is same as A/C on.

Here's what I would try.
B4308 back to stock. That's a definite
B3606 It seems that when your rpms start to drop is when you hit the
rich area of the table. Suggest back to stock.
B4307 Increase values by 1.0. Try this after you have already tried the
first 2.
The VE's look very much out. I would run the MAF until you get a WB. Could be part of the problem
You are tuning trims with the IFR and leaving the MAF table stock? I have not had good luck getting a stable tune that way.

[SSpdDmon]

Sent a file. As suggested, try running MAF only tune as an alternative by moving the MAF threshold down to something very low like 100rpm. If it's not a big cam, there shouldn't be that much trouble with this. That way if the problem is fueling related, it should expose itself.

[Chalky]

Joe:

VE table is based on WB02 SM-AFR.

One thing that did catch my attention was the fact that I have PE and CFOL around 12.95 or so. when I checked commanded vs actual AFR, WB is showing a leaning condiiton the harder I run the car. Not sure what I have here but am going tor replace fuel filter at the least. Might check header gaskets again. Car should not go lean.

I don't tune with IFR, IFR are setup for SVO 30's.

[jfpilla]

I forgot that when I had SVO's they flow tested as the attached.
I would take another shot at the VE table.

[Chalky]

I looked at some older VE tables after running them through a AUTOVE rinse and they all had the same basic shape.

I'll try your IFR settings and see what happens. I have been thinking about trying a different injector as well. Maybe even a 42.

Using my scaled number for IFR, I am at 85-90% IDC.