Acceleration enrichment query

[Tony C]

took the car for a run the weekend and she ran fautless,
cold start is near perfect now just a few tweeks needed here and there, and warm running is also near spot on,
one thing i have though is under light throttle acceleration my vems gauge reads 1.02-1.09 briefly until i squeeze the throttle a bit further then she drops to about 0.82,
you think i should drop the (0) to around 3 instead of 5???

my accel bins are as follows.
(0) 5
[1] 25
[2] 44
[3] 104

accel amount.
(0) 0.9
[1] 1.7
[2] 2.0
[3] 2.5

duration [ms] 2.9

[[email protected]]

Nice to hear that things are coming together, the suggested bin values are:
1
5
20
40

Rob

[Tony C]

cheers Rob,
will change them shortly
shall i leave the accle amounts as are for now,?

yeah things are coming together and the more i play the quicker the car feels,
i used around 1/4 of a tank to Uxbridge and back, and we got caught in a bit of traffic too, was well pleased with the fueling,
at cruise the af gauge is reading 0.99. shall i go leaner?

[[email protected]]

leave the amounts as they are, I'd expect a little bit of tweeking will be required.

0.99 seems pretty good, you can try and take it to 1.0 but I'm not sure what gains in fueling you'll see.  It will be interesting to see what dnb gets in the way of improvement when he tries his leaning experiments.

[dnb]

I'd suggest 1,5,20,40 may be a problem on the Rover if you're using the standard throttle position sensor - it's quite noisy on mine (by one LSB), and always triggers the accel enrichment.

I use 3,7,20,40 instead.

[Tony C]

cheers guys, i'll try your settings Dave as im using the rover tps unit.

im hoping to be sorting a rolling road day on my v8 forum soon in uxbridge, any one local to there who maybe able to give mine a look over and a possible tweek after its power run?

[dnb]

I've just looked at my latest log and it shows very clearly some of the things Cliff has talked about here.  I'll post it up tonight

It means I have a fighting chance of getting accel enrichment right now.

[Tony C]

Keep me posted dave please,
as it may also help me out

[Sprocket]

I'd suggest 1,5,20,40 may be a problem on the Rover if you're using the standard throttle position sensor - it's quite noisy on mine (by one LSB), and always triggers the accel enrichment.

I use 3,7,20,40 instead.

I am having a head ache over this as well

I have just come back from a holidy in Cornwall in the Mini and encountered little problems other than the engine cutting out in the second lane on the up side of the Avon bridge crossing on the M5, lol, thats another story. Whit this did allow me to do is watch what was going on, when the screen wasnt playing up, again, another story.

It was clear that the suggested 1 5 20 40 bins were causing AE when the throttle was almost stationary. The Mini is not the smoothest of rides and every small bump caused AE unnecisaraly. Having read this topic before we left, I altered the bins to that that you suggested and the problem dissapeared. I do however still need to sort out the transient fuel amounts.

Slow acceleration is almost perfect, only issue with sudden WOT situations where a massive lean period causing the engine to cut and recover. Im finding it difficult to tune as i really dont know which bit im altering.

So, in AE for dummies, can some one help me understand, its a real killer on the drag strip and its showing on times.

OK so far i understand the acc bins as the rate of acceleration, small number gentel acceleration, large numbers hard acceleration. I also mildly understand the acc amount as being the extra, added ontop PW?? to that of the base PW??

Im thinking the acceleration duration is the time the 'lean' peariod lasts??

Now after messing about, the larger duration time i use, the larger the rich dip is on gentel acceleration, the better it gets on hard acceleration, so the duration and amount need to be tuned together.

Am i correct in thinking as I increase the duration to get the hard acc sorted, i need to reduce the lower acc amount to stop the rich dip.

Or do i just increase the hard acc amounts, in which case where dose the duration fit in

the longer i think about it the more i'll understand it , i now have a week to play with it without relying on the car to get us home

[Tony C]

mines running real sweet after setting my accel bins to daves settings,
just need to drop the fuel table at WOT now as she is reading 0.75 now
or change the accel enrichment, but it runs good so may tweek the table instead.

[dnb]

Tony - tweak the VE table if it holds the 0.75 lambda for a decent period of time.  If it's only a spike at 0.75 then drop the accel enrichment amount a little.

Sprocket - You're about there with your understanding.

The 4 bins determine how much the fuelling pulses are extended when you're accelerating.  So if you have a base pulsewidth of 2ms in a given cell, and you accelerate through that cell then the pulsewidth will be 2ms + whatever the accel enrichment is set to.

The duration is how long the pulses are extended for.  MT says the units for this are ms.  (I think they are actually seconds!)  So yes, this should be the same length as the lean excursions you are seeing in the log.  (Well, give or take a bit)

The amount of extension should then be set so that you achieve your target fuelling as soon as the accelerator is used. 

Have a read of the accel enrichment thread in the config (I think) forum and see if it makes a bit more sense.

BTW, I am using 2 as my lower accel bin instead of 3 now and this seems to work a bit better.

[Tony C]

cheers dave,
i will have a look in the week as the car is away now,
i will try dropping to 2 also.

[Sprocket]

Right then, not happy with this.

I can get the AE about right for 90% of driving, but when you floor it the engine stumbles. I can also replicate this with tiny, quick  throttle movements. No good with heal and toe down shift, engine response is piss poor with no load on engine.
I have tried and tried, either way the engine stumbles rich one way or lean the other, there is no happy medium. Bloody SPI, wish i ditched in the first place, low ohm injectors and wet manifold, royal PITA.

So, I am looking at the pressure based rather than throttle based, my thinking on this that small Dv at low RPM generates large Dp.

Trying to fully understand the Acc bins, is this number caculated by multiplying dv and dt, or is it divided. The side bars show divide, as delta volts 'over' delta time [dv/dt] or the bin value an actual rate, so if dv was 4, dt would be 10ms, all seems backwards as shorter dt would give small number and less fuel yet rate of throttle increased. I assume the number is a factor rather than a rate, but how is this factor calculated in the firmware

Need to know this to try the pressure based, I suspect not many are using it.

Also, the 'agreed' acc bin values, how and why are these suitable for all aplications. Every engine is different as is the throttle and its rate

What do the OEM guys do that we are not, the principle cant be that complicated.

this is starting to put me off as throttle response is unpredictable.

Please hurry with the new AE firmware

[[email protected]]

I doubt you'll get any better results from the pressure based system,

The agreed rates are based on throttle opening speeds - change in TPS sensor voltage/time.  They're based on a

Normally its not as bad as you're seeing with your engine, have you tried adjusting the enrichment time?

The 1.1.26 firmware has improved accel enrichment, development is afoot.

[dnb]

Are you TOTALLY sure your VE & lambda maps are correct?  (I'm not questioning ability here, but it's really easy to overlook something if you are trying to map alone or based on datalogs alone)

AE is only intended to make the richening effect of this into a "step" response (ie an instantanious change from say lambda=1.0 to lambda=0.88) to throttle, instead of a more gradual rise.  It isn't there to ensure you hold a rich mixture during the car itself accelerating.  (Perhaps "acceleration enrichment" is the wrong phrase - I like Cliff's "tip-in".) 

Can you put up a plot of RPM, MAP, TPS, Lambda & pulsewidth against time for a couple of your acceleration tests?   Or better yet, chop them out of a log file and put them in an excel sheet.

Appologies if I'm giving you lessons in removing the innards of eggs without breaking the shells...