Pressure based Acceleration Enrichment

[Benzmac16v]

So, my tps sensor is pretty useless at the moment.  Not sure exactly what is wrong yet, but I have a feeling it is a combination of improper installation and poorly balanced wheels.  The tps will report huge changes in position the faster you go (up to 15 on the completely unintuitive dotrate scale at 80mph when you start to feel the wheel imbalance).

At anyrate, as a temp stop gap I want to enable pressure based AE to try to make the car a little bit more drivable.  It is very responsive with small throttle change, but chokes with heavy changes. Rev matching is very lathargic.  We have 3 of these cars, two totally stock, one with vems.  They all have similar power (although hard to compare with the seat of the pants given the different differential of this car) but the other engines respond so well to quick throttle...  I drove one the other day for the first time in a while and I was overreving the shit out of the engine during down shifts because they just rev so much freer.

But when I try to get the pressure based acceleration enrichment in vemstune, there are no settings.  I still get dotrate vs scale, except the the dotrate indicator does not ever move.  So it would appear I am not getting anything.  Is this just something no one uses anymore and no longer works, or am I just missing something?

Thanks,
Jim

[z0tya]

Maybe try fuel film insted of. It works well w/o normal acc. enrichment.

[Benzmac16v]

Fuel film hasn't really helped under hard throttle blips/drops...  I think the under lying problem with the lackluster response is a very quick misfire during acceleration.  I cannot figure it out.  I have done everything from no enrichment to absurdly large amounts of enrichment and it always misses the instant after acceleration.  Lambda will go lean (hits the lean limit) and then bounces back.

I re-enabled tps based acceleration and did some hard throttle drops at idle and out of gear (tps is very smooth in this condition, so there is no noise on the signal).  There is a log file of this attached.  I have also tried dropping ignition timing from as high as 36 degrees to 0 and always comes up with the same issue.  Lambda table has also been played with, but it will happen over the entire rpm/map range.  I am beginning to think it may be hardware based...  I have a (new) map referenced fpr, maybe it is doing strange things when the map changes rapidly...

Anyway, here is the log:

http://dl.dropbox.com/u/20887362/v3.3_n001612-2011.04.13-15.36.26.vemslog

Thanks,
Jim

[mattias]

@ Jim:

Too little acc enrichment, it's not even 1 ms of total pulsewidth. At low revs you need a lot, raise your "RPM vs amount" at 1000 rpm and just above.
For better cold acc enrichment, set cold multiplication factor to 200-300% and added amount to at least 100%.

Disable the priming pulse. Set your injectors to fire simultaneously while cranking, divider 1 - it'll start faster and get more fuel more effectively in there. Lower your cranking VE to 70% or you'll flood when cranking hot.

Double your injector voltage compensation, might explain your excessive crank VE% if your voltage drops a lot while cranking.
Afterstart cold time, set it to 300-400 cycles, disable any hot afterstart (0 cycles).
Not sure about your warmup and cranking enrichment, seems you're using too little warmup and too much cranking enrichment. Start the wideband heater through the calibration dialog, just to activate it before cranking to get immediate report. It should run lambda 0.90 up to 30-40C coolant temp, and richer the first 10s of seconds to avoid having a non-responsive engine.

Compare with the config in my signature, a year old firmware but soon updated to 1.1.88, no difference concerning what I just wrote above.

I forget, did you have the single throttlebody 16v engine?

[Benzmac16v]

Thats gold!  Ill be able to go test it tomorrow.

I have a single throttle body 16v.

I really haven't done much with cold anything...  It will fire up and run good enough to get warm as it really doesn't take very long to warm up.  Once I get it running really good warm Ill start to really tune up my cold settings.  But thank you for the details on how to do it, that will be very helpful.

Thank you very much!

Jim

[Benzmac16v]

Oh, and another thing.  I always get a validation error when I open a config file.  Something about low boost not being supported in the future... Do I have a setting mixed up?  Or will I need a new sensor at some point in the future?

Jim

[mattias]

Check under ECU calibrations. You will have to redo the pressure bins on all your tables, no biggie.

[Benzmac16v]

Ok, so when I click on the error message it has 2 things highlighted in red (I assume those are the issues)...

1. Map Range Unit:  Set to: Normal (<510kpa Sensor)
2. Table Kpa Unit:  set to: 1 (<250kpa)

So I think it is telling me to change the table kpa unit...  Just change it to the >250kpa or the >510kpa?  I have never touched this setting because I don't know what it is...  And why do I have to redo my pressure bins?  Isn't the sensor just reporting pressure?  I guess I dont have any idea what this setting does!

I just made the changes you suggested and they work!  Starting is pretty much the same as before, maybe a little harder (I imagine I just need to tune the fuel a bit more).  The acceleration enrichment actually works now!!  Now I really need to fix my tps (I think it is just a loose screw as my map is dead steady... Its just a mild bitch to get to as I kept the old MAF housing (MAF sensor and plate removed) so I could keep the stock throttle linkages... KISS is a pain in my ass sometimes!).

Is there a general lambda target I should go for while tuning AE or should I just go with the old seat of the pants meter?  I am going to have to put a cat back on shortly so I know I should limit the lambda as to not kill the cat (again.....).

Thanks,
Jim

[mattias]

Set Table kPa unit to  : "2 >250 kPa"
All the pressure bins in your tables will now have doubled their value.

It's a matter of having 8 bits of data to define the pressure bins, with your old setting of "1" it only gives 2^8 = 256 different values. If you use more pressure than that and have a MAP-sensor capable of it, then this variable will indicate that the values double so that the largest value is 2*2^8 = 2^9 = 512 kPa, which is good enough for most but the insane.

[Benzmac16v]

Thank you for the explanation.

One more quick question.  I have to put a cat back in my car, I know they operate best between .98 and 1.02 lambdas, but what lambdas will cause premature failure of the cat?  I am not sure how sensitive it is and just want to make sure I am never running at that point.

Thanks,
Jim

[mattias]

Running insanely rich will kill it. You'll be fine.

[Benzmac16v]

hahaha, ok.  This car used to eat cats like none other.  It ran stupid rich at the time.  It would fall out of tune in about a month and I wanted a project, so I decided to EFI it, rather than spend hundreds, if not thousands, on a CIS system that didn't even have an O2 feedback...

Jim