Hi guys,

I purchased one of Peep's kits this spring and finally got the car (mostly) running right - it wouldn't rev over 4k and new speed and ref sensors fixed that.

However I am still have some nagging problems.

First a little history on the car. It is an 88 951 with a vitesse stage III turbo in it (with 3 bar FPR and appropriate injectors). 98k miles. Rebuilt throttle body and it also has new injectors (high-z ones Peep recommended).

I was having drivability problems (not running well off boost, very rich running, rough idle, bad fuel consumption, loud popping in intake when accel at low RPMs, however would go like a scalded cat once boost would build) and figured that VEMS would allow me to better diagnose issues as well as all the tunability features.

Anyways, ever since I have got VEMS running, at idle there is popping in the exhaust, and if I go to the tailpipe it's almost like it misses an exhaust pulse each time there's a pop. Misfire? It goes away as soon as throttle is applied. I did note when rebuilding the TB that the bypass screw was set to 3.5 turns out, which I am now finding out is way off stock setting of 0.5 turns out. I turned the screw back in to 0.5 and my idle is down to a more appropriate RPM, but still higher than target. On a stock 951, I know you are supposed to jumper the diag port to set idle, but what is the correct procedure with VEMS? Is just turning the screw in ok, or do I need to do something in VEMS with the IAC when doing this?

I am attaching a log of my car just coming off of cold start enrichment and idling. The entire time in this log that the car was off enrichment, it was popping, Attaching current VEMS config as well if that could help. Peep is usually really good about getting back to me with questions, but haven;t been able to reach him this week - maybe he's on a (well deserved) vacation? I get the impression that guy is really busy!



Thanks so much!

 

You can close the bypass entirely and control idle purely via icv and ignition timing.

all your symptoms seem resultant of overly rich mixture...have you adjusted your VE manually or with auto tune?

 

Hi,

I will try closing the bypass.

I have done probably 100 miles of autotuning with live VE analyzer and autotune on, burning to ECU each time. Req_fuel was set as per Peep's instructions - kept adjusting until lambda =1.

 

Also note that 'all my symptoms' re: drivability were BEFORE VEMS. It runs much better now, just idle is weird.

 

Hi,
can you post your config file? Do you have the Siemens Deka 630 cc injectors? Watchout for cheap chinese replicas on the internet for those injectors!
req_fuel should be calculated to 7,7 ms.

 

Yes, these injectors.

https://www.ebay.ca/itm/4-x-835cc-Si...72.m2749.l2649

Req_fuel currently 5.5

Config and log should be in .zip file in my first post.

 

Ah ok, just didn't see the zip-file.

I think that maybe the injectors are way to big for a 2,5L engine. I am running the 630cc injectors on a 3L 951. That is the opening times will be very short at idle. can you test it with the stock injectors?
For first approach to get a smooth idle deactivate all "helpers" such as EGO-correction (set step size to "0"), IC PID ( all to "0") and disable ignition based idle control. Btw: retard and advance change is with 15 degrees way to high (should also work with max. variance of "4" a/r) .

Set ignition to 10 or 11 degree at idle in the ign. table.
Set target lambda at idle a little more rich to "0.97".

Alter the settings in the overrun fuel cut (that should eliminate exhaust popping)
fuelcut RPM: 1400
fuel resume RPM: 1200
The 20 kPa MAP line in the VE table is around 35 in my table. Will help popping issues too.

Now tune the VE-table and WUE. It is possible to achieve a good idle without the helpers mentioned above. When idle is quite ok you can enable IC PID and IC ignition a/r.

Hope this will help you.

 

Hmm..

I just pulled my plugs (NGK BPR6ES) and the cyl 4 (or 1; the one furthest from the firewall) is extremely sooty, definite misfiring going on there.




I don't know what to make of this - hmmmm.,,,

 

Thinking more, I think these plugs I have previously fouled and subsequently cleaned with a wire wheel while chasing lambda with req_fuel (my board was missing a resistor and kept reading way lean).

I am going to get some fresh plugs and try this again, maybe that's all this is.

 

With #1 being the only sooty one, I would check orientation of intake manifold gasket, as it is reversed as opposed to the other 3. Fuel isnt spraying properly, fuel puddling and causing overly rich on that cylinder. Do you have a test pipe or gutted catalytic converter? That would cause popping during idle. As far as req_fuel setting is concerned, you adjust until lamba is close to 1. Everyones tablet is different. Im running siemens deka high-z 80# on my 2.5L and my idle is smooth ( without an idle valve also, just need to open throttle on cold starts ). Peep has been quiet lately. But the community here has a good grasp of how VEMS works. Check out the other VEMS Install thread, its become the goto for information. Cheers -Wayne

 

Hi,

Thanks for the reply. Yes, I saw the big VEMS thread and read through it.

I know about the gasket being reversed on #1 and am pretty sure I installed it correctly. However it never hurts to double check. When I get my new plugs I will take the injectors out and have a look down that hole.

req_fuel seems to be good and lambda is 1.00.

We'll see what happens with fresh plugs.