JekyllandHyde

iTrader: (3)

So I got idle dialed in nice and smooth. It idles rock steady at 700rpm. My question is about off idle. I notice that it's pretty hard to take off lightly with the T56. I always attributed it to the lightweight flywheel and Spec 3 clutch. Basically what would happen was I would apply light throttle and the rpms would shoot to 2000, then drop back down to 1600. I always thought I was lifting off the gas but turns out I wasn't. Took a datalog revving it in neutral and found something interesting. When I hold the throttle at 1.18% to hold an rpm less than 1600rpm, the revs would shoot up, and even though I'm holding the TPS steady, the rpm will drop about 500, then raise then drop, etc. It does this only if you're trying to hold an rpm less than 2k. 2k and above is fine.

BLMs are at 120-122, MAP is 20-30Kpa, though integrator is rapidly counting up and down following as the engine speed varies. I'm running sAUJP v4 set up for manual trans. I have played with spark and fuel in this area and it has not helped. Would this be caused by a prop gain table? I have already adjusted my prop gains at 4DE according to my injector size. What about the table at 4D8, Prop Step Size Gain vs. RPM. Would this be a good table to mess with?

RBob

iTrader: (1)

One thing that can help with this is to slow down the INT update rate. This is done via the INT delay tables. There is too much proportional gain which is causing the INT to chase the proportional gains.

> When I hold the throttle at 1.18%

Check to see if the ECM is still in idle mode. If so there are additional parameters that can be worked with.

I haven't found that the proportional durations help much. The proportional gain is what makes the most difference. With the INT moving rapidly it is a sign of too much gain.

Not enough gain and the INT slowly climbs and falls to create x-counts.

RBob.

JekyllandHyde

iTrader: (3)

RBob, thanks for the suggestions. I checked the datalog, and saw that I was still indeed in idle mode. So I looked at my bin and found Idle Max % TPS at address 494, saw it was at 2.34% so I decreased it down to 1.50% to start. AXXD has it at 1.96%.

I also found the Add Correction to INT Delay at idle value at address 49A and saw that it was at 0.00 seconds. I increased to 1.50 seconds to start with and see what it does. You said there were a couple of other parameters as well, did I miss any?

I'm going to try the changes out tomorrow morning after my neighbor leaves for work. I don't think they like it when I start the car while they're having dinner.

Saar

have you watched your IAC counts during one of these events?

JekyllandHyde

iTrader: (3)

Yes, IAC remains stable. The only thing that's changing is the INT, which goes up and down with the revs, so it's gotta be a fueling related surge.

Saar

in that case, disregard. i've seen an odd situation where at idle in park with a small amount of throttle, the IAC goes into what looks like a sine wave and takes the actual engine speed with it.

if i had to guess, i'd say you might also see the same problem just coasting along at low speed.

JekyllandHyde

iTrader: (3)

Well, I tried out the changes this morning and found something very interesting. The change in max idle vs TPS did not help. I ended up putting it back to the 2.34% value. The INT delay did help, but the car was still surging, though it would surge for about 5 seconds and then straighten itself out. BLMs were reading 126 at this point. I did notice that the IAC wasn't moving and was staying at 11 steps with the fan running. (Yes, I know I should have more steps for MPFI, but my TB screw is all the way out, so I can't close it anymore.. This is a stock TB bored out to 52mm.)

I found that the IAC in this case was my friend for a change. I was running throttle follower at 150%, so I raised it back to the AXXD stock value of 200% and it cured a lot of the surge. I'd give it gas, and the IAC would open faster letting more air into the motor at the low throttle setting. It did make the throttle very touchy, but it was actually EASIER to take off with the car at lower engine speeds since the rpms were more consistent. Trying to hold a low rpm below 1600rpm is hard though. I'm going to try adding more IAC steps at lower speeds to see if it can help me a bit more.