E38 idle tuning

[gmh308]

Well I think we are missing a couple of tables still
Like an ECT modifier for adding g/sec for cold starts.
Min airflow is fine once warmed up. But not for cold starts.
Sure there is ECT "Correction" multipliers. But nothing for base idle airflow addition vs ECT.

The reason I mention this is because my 440 cube lump doesnt like cold starts. It fires and dies immediately no matter what min idle airflow I use.
Im going to have to join the rest of you lot and drill the blade. Im sure if there was an ECT adder to base airflow then that would not be necessary.

Cranking idle air is also fine for the initial firing, its when it blends into idle airflow at like 3*C it just dies. Ramping correction multiplier up doesnt do anything useful either.
At around 40*C ECT she settles down and idles much better.

Anyway, the drill is coming out this week hopefully that will give me the base airflow g/sec I need to prevent the cold start stalls.

Tried reducing the cranking VE mult table ?

[hymey]

Well I think we are missing a couple of tables still
Like an ECT modifier for adding g/sec for cold starts.
Min airflow is fine once warmed up. But not for cold starts.
Sure there is ECT "Correction" multipliers. But nothing for base idle airflow addition vs ECT.

The reason I mention this is because my 440 cube lump doesnt like cold starts. It fires and dies immediately no matter what min idle airflow I use.
Im going to have to join the rest of you lot and drill the blade. Im sure if there was an ECT adder to base airflow then that would not be necessary.

.

B1602 Richard. It's all there This is the multiplier to min idle air. So when it is warmed up it is fine. Take note earlier o/s gave 1.00 there when hot, later have 0.25. It's all been looked at mate and tested over and over.

The reason why it won't start cold is because the e38 is designed for a stock cammed engined not a cammed 440. You need to drill it to allow for a LOT more air cold. And after you drill it, it will need to be retuned at idle

So when you first replied to the thread a while ago and said it is not required, just add it in the tune, this is all good on paper, but it will not work for the reasons I have outlined over and over, hence why I originally told you it was important. Would have saved you a whole lot of heartache to follow instructions You need to drill 2 holes in yours maybe two 5 mill holes, 1 at the top and 1 at the bottom. B1602 x your final g/s value will max out min idle air so that it runs on B1652 at cold. If it rpm's low dont add timing add a bigger hole. Once you do this cranking idle air will be to high it will race off.! As cranking idle air will max out max idle area aswell just like min idle air does! ie at 12 g/s she is maxxed out hence why it won't fire right up.

Once it is enough air at cold( and believe me you will be better off with two small holes rather then one ten-but start with one first, then step up 1mm a time in the second to achieve your goal) you will find it may overshoot on cold start. Simply add your min idle air values to the cranking idle air table and test it. It will be close just need a slight raise at the most towards cold ect values.

Also Cranking VE can stay stock, I recommend don't touch tables that are not required and this is one of them.

I would also change cranking timing in yours to around 20 degrees cold and 12 hot. Big cammed stuff likes this, Again it is not a factory engine.

I am not writing this to send people backwards, It will solve your issues, just tuned another one last night with 240s cam and heads, idle done in ten minutes.

Let me know how you go champ,

Cheers mate

[The Alchemist]

yup '1" and a idle learn reset did it !!! yay
Also found my other little problem with the IPW jumping was "fixed' by a fuel learn reset too
I thought when you reflashed a E38 the fuel trims were reset automatically?????
I had the car in full open loop of course but obviously there was a long term trim still stored in the E38.
VVT sorted in 5 AFR sweeps on the dyno > wicked !
Question: why can't you "see" LTFT's stored in memory like you can in the LS1 ECU's?

[swingtan]

Well I think we are missing a couple of tables still
Like an ECT modifier for adding g/sec for cold starts.
Min airflow is fine once warmed up. But not for cold starts.
Sure there is ECT "Correction" multipliers. But nothing for base idle airflow addition vs ECT.

The reason I mention this is because my 440 cube lump doesnt like cold starts. It fires and dies immediately no matter what min idle airflow I use.
Im going to have to join the rest of you lot and drill the blade. Im sure if there was an ECT adder to base airflow then that would not be necessary.

Cranking idle air is also fine for the initial firing, its when it blends into idle airflow at like 3*C it just dies. Ramping correction multiplier up doesnt do anything useful either.
At around 40*C ECT she settles down and idles much better.

Anyway, the drill is coming out this week hopefully that will give me the base airflow g/sec I need to prevent the cold start stalls.

What you may also want to look at is....

1. {B1832} Cranking Idle Air: Sets the base airflow for cranking. If you find the engine starts better if you us a bit of throttle, then you want to increase the values in here.
2. {B1833} / {B1834} Cranking Air Mode Upper /Lower: Times when the ECM switches from cranking mode to general run mode. It's possible that in your case, the ECM is either staying in crank mode too long, or not long enough. I'm going to guess the first one.

I haven't drilled the blade in mine, but it's only got a small cam. I'd drill the blade if I had a spare one to play with though..... Maybe I'll just drill it anyway :p

yup '1" and a idle learn reset did it !!! yay
Also found my other little problem with the IPW jumping was "fixed' by a fuel learn reset too
I thought when you reflashed a E38 the fuel trims were reset automatically?????
I had the car in full open loop of course but obviously there was a long term trim still stored in the E38.
VVT sorted in 5 AFR sweeps on the dyno > wicked !
Question: why can't you "see" LTFT's stored in memory like you can in the LS1 ECU's?

Excellent work! I had a feeling that the LTFT's may still have been active, but not learning. The only way I've checked for LTFT's is to log them, or I just do an ECM reset to ensure they are gone. This also clears any learned idle control as well, which is a must when trying to get the idle right. It would be nice to have a "learned data reset" option in the V2 Tuning section..... nudge, nudge.....


Simon

[ringram]

Yeah maybe my cranking idle air is too large. I did wind it up quite a bit earlier on with the last cam (only 6* overlap). It fires up to 2000rpm and drops from there, perhaps if it was 1300rpm or so it wouldnt overshoot.
When warm it cranks, fires and idles pretty well. With only about 100-200rpm overshoot on the downside. (which a small hole might sort)

I read b1602 as a multiplier to the correction factors rather than a multiplier to min idle air.

Some more ideas to play with anyway

[hymey]

There are multipliers for correction factors, but not b1602, it is for min idle air. Try doubling its value. As a matter of interest does your car have 0.25 multiplier when hot? or 1.00. The earlier ones had 1.00 and later 0.25 hot and 0.5 cold. Now try changing this value to 1.00 and you will see it multiplying min idle air It will max out the TB for 13 seconds and then learn back.

[hymey]

I do the same as Simon, sometimes I flash e38's and they do not clear codes when they should so I manually clear them.

Latest issue, Turning cat protection enable to off does not seam to work on some os. The DTC is activated still on long drives, so I leave them enabled and raise the temp enable to 2000 degrees C.

Some weird things happen with e38s and reseting the ecm is the go. If the ecm has learned it self to idle at 8g/s and it needs to be 5 and you command 5g/s it will still try and idle at 8 etc.

Personally I have not had any LTFT issue's as I never use them, but it is a good idea to reset anyway.

Wait till you flash a car that has been tuned with HPT cos, even after a full reflash there are so many glitches!

[hymey]

I haven't drilled the blade in mine, but it's only got a small cam. I'd drill the blade if I had a spare one to play with though..... Maybe I'll just drill it anyway :p






Simon

Gday Simon,

You most likely won't need to as the L76 os gives you a higher limit.

Long time no hear bud , will have a chat to you when I see you on msn. Need to run some things over with u

Joel

[swingtan]

Yeah, it's been a while :P You've been a busy boy up there. As you say, there was change in {B1602} and as I don;t get a large number of cars to play with, I haven't looked at the differences a lot. In my tune, I go from 1.0 when hot, all the way to 1.8 when cold. This gives an additional 1.8x the min idle air when cold. I'm just in the middle of doing some screen shots to show a few other tricks for Idle tuning, because the e38 learns very fast and remembers for a long time.

Simon

[swingtan]

OK, here's a few more tips.....

attached are 2 images ( click for larger view ) showing the effects of too much idle air and too little idle air. Let's first look at too little...



Commanded spark is 23'
Commanded idle air is 7gm/Sec

Note the logged airflow and spark for the entire idle section is fairly constant, but there is some instability shown in the MAP and RPM traces. The averages of all traces shows close to spot on the commanded values, though Idle airflow is up at 7.5gm/Sec, indicating that idle air control is adding air.

Now for comparison, too much idle air...



The main difference here is that min idle air is set to 8.5gm/sec. You will quickly see the difference in the start of the idle data. Initially, the ECM is commanding too much airflow and to try and reduce the idle speed, is pulling timing. Airflow at the start is about 8.2gm/Sec, timing is down to 16' on average, try and reduce the idle speed. From the time the clutch was pressed in, it took about 18 seconds for the ECM to pull the airflow back to where the idle speed meets the commanded value. After this point, idle speed and spark average out to the commanded values. At this point, the logged airflow is averaging 6.7gm/Sec and the idle but both the idle speed and MAP traces are very stable.

The comparisons here are interesting....

When idle airflow is commanded low and the ECM learns up, the idle quality is worse than if the commanded air is high and the ECM learns down. This occurs even though the resultant airflow is lower when the commanded air flow is high. If the commanded airflow is set too high, the idle hangs for a little while till the ECM corrects the airflow. This can help if the engine tends to stall on "clutch in", but can be annoying by causing the idle to stay high for too long.

It's not a surprise that commanding a higher airflow at idle helps with stability, it's just that now we have some actual data to help understand what is going on. In this case, I'm going to set min idle air at about 8gm/Sec

Simon