E38 idle tuning

[swingtan]

Excellent info there ringram!. I'll have a play with this as I've been hunting for a low speed, low load surge for a while now. I've also "reduced" the commend cranking air in my car and found it starts better.

On a different note, I thought I'd offer a tip on idle fueling for those still running a MAF. It seems that on some E38 OS's, the ECM will drop into SD mode for idle fueling and no amount of MAF adjustment will help. I get the feeling that it's what is termed "closed loop idle" in some OS's, where the "closed loop" does not refer to O2 trims, but to the airflow bias between MAF and MAP. At certain idle settings, the MAP takes precedence even if the MAF is not in a failed state. I'm still working on this one though.

Simon.

[hymey]

Ok, update from me. I decided to epoxy up the hole and retry perhaps with a smaller hole.
BUT after speaking to Jessie from Waitforme at PRI did some messing with B1650 Max ETC area and what do you know. All seems well now.
Way, way better on cold starts than before and NO HOLE! I told it the area was smaller. Im guessing all the tables we cant see and corrections etc now think the throttle is small so it has to move the blade a larger amount.
I cant remember if Jessie said to make the value larger or smaller, but figured Id play around anyway.
So before anyone drills anything Id try this table first.
I can now drive at idle in 6th gear at 32mph on the flat, no jerking or lurching. Mind you cam is only 227/243-113

Thats good to hear Ringram, I noticed you had values of over 2 in max idle area which would not work with a hole in the TB, with the earlier o/s you can get away with a smaller hole(or in your case-no hole) but I can guarentee u I could get it running better with a hole. The blade just trims to far. Trust me after years of hard work on this and fixing a crap load of them (I have learnt the hard way) I can honestly say I have seen people come to me very happy with there tuners results with no holed TB to then drive a car with a stock like cam. I can only tell people the method I use. Just like a uni lecturer they give out the info weather the student can grasp it and make it work for themselves is another thing. But all in all I am glad you got it running and sorry if I lead you down the wrong path..again though as shown by the video before a car 220s duration on 112 lsa in an early o/s e38 with 7mm hole idling like stock. Cold start is relatively simple aswell. Infact I have a car in the workshop here with a 230s cam on 110 and drilled it 7mm once its tuned will post up some vids.. BTW I am glad guys are reading this stuff and messing with the max idle area tables.

Cheers

[ringram]

No worries mate. As you say as long as everyone has the tools in their tool bag they can select the one that works best for them

[hymey]

I spoke to Simon the other day about integral and proportional tables integral being short term and long term being proportional. If anyone has read the thread you will see some stuff on PI controllers and how they work with the 'P' being a learnt value and 'I' being a direct input by zeroing out the P table like you can do with long term idle trims in LS1s this allows any memory to not be used and allows the car to run on the direct value. I myself tried this the other night and found the min idle air much more responsive to changes without the need to reset the pcm all the time so good stuff Simon.

I have a vid here that I am experimenting with I have setup a 4 barrel manifold on my VE-G8(248-254-106 cam 40 deg overlap) and I can switch from carb back to efi in like 2 hours(yes a carb) just by changing the regulator and reconnecting fuel rails and some minor tune changes. I am amazed at how well super sedans run with massive cams and idle at 800 rpm and just bump over but super responsive with there competition carbs and powerful ignition systems. So in a sense I am playing with the e38 to obtain a correct idle while no injectors are there just thought I would show people it can be done. Vid is a little dodgy but its just an update on the progress(getting there). The car has a nitrous setup can go upto 300hp. I also have a large garrett turbo here I would like to setup blow thru carb. Will see how we go.

http://www.youtube.com/watch?v=EFqKZ_CWAok

http://www.youtube.com/watch?v=ORiZ5kd1580

sorry bout ordinary filming lol

[swingtan]

Ringram: I've made some initial tests on a "smaller" cam (220/224) and found that B1650 has an interesting effect. I like it so far but the verdict is still out on the light throttle surge. I found that reducing it too far, resulted in a hanging idle when cold and the normal ECT correction table needed a lot of work to try and correct it. So I increased it to about 80% of the stock value and it seems fine. I still get a small amount of surge so may need to work on some dynamics again.

Hymey: Those tables can give some good results, don't they. As mentioned, I zeroed out the few cells around 0 RPM in the Proportional table to help with idle control. I'd found that my engine idled better if it was commanding slightly more air than it really needed. The problem was that the Proportional table would pull too much air out and the idle would go rough. I was consistently adding 0.5gm/S to the min idle air, then it would learn down and run rough again. So I zeroed the cells and all is good now. Min idle airflow is what I want it to be and the ECM does not remove addition airflow.

Simon.

[hymey]

Simon, It works wonders, infact I seen it zeroed out in a stock 09 VE clubsport OS. So HSV been playing too. They definately like to idle better with a little more air and lesser amounts of timing. The cams people mainly use arent that big and don't call for large amounts of timing. The motor needs to breath at idle. You just command what idle air you want and it responds basically , the integral tables do a fine job trimming the air and getting as fussy as we do now means proportion is not required. And it sure does mess things right up at times.

The only real fix for surging I have found is lowering B1651 a little and running in openloop. This helps a lot.

Also It has a lot to do with the engine. If I put a 230s cam in dot to dot and cam is retarded it will surge in CL. If I then fit a new timing chain and degree the cam with a rollmaster etc So it is advanced say 2 to 4 degrees. No more surging in CL in most cases. 3.9 and 4.11 diff gears will eliminate it with a M6 once you have the tune right they drive amazingly like a stock car or better!

Joel

[hymey]

Ringram: I've made some initial tests on a "smaller" cam (220/224) and found that B1650 has an interesting effect. I like it so far but the verdict is still out on the light throttle surge. I found that reducing it too far, resulted in a hanging idle when cold and the normal ECT correction table needed a lot of work to try and correct it. So I increased it to about 80% of the stock value and it seems fine. I still get a small amount of surge so may need to work on some dynamics again.

Hymey: Those tables can give some good results, don't they. As mentioned, I zeroed out the few cells around 0 RPM in the Proportional table to help with idle control. I'd found that my engine idled better if it was commanding slightly more air than it really needed. The problem was that the Proportional table would pull too much air out and the idle would go rough. I was consistently adding 0.5gm/S to the min idle air, then it would learn down and run rough again. So I zeroed the cells and all is good now. Min idle airflow is what I want it to be and the ECM does not remove addition airflow.

Simon.

Another note B1650 if changed will alter TP% reducing it actually increases TP%, so if you get 9% TP% you maybe getting 15 or more % just a guess really.

[ringram]

I think it will act on some hidden airflow calculations. (ie) I need 10g/sec so given ETC area y I need x% ETC.TP to deliver the 10g/sec, of course a "smaller" throttle means greater x% for airflow.. So its tricking the ECU, but whatever works Given mine is skewed due to limited IFR another skewed value is ok. Thanks to Jessie for the heads up.

[hymey]

Sounds good, I have read some of the HPT guys doing it, A lot of guys there having issues with things it is easy to mess things up. I redid a car last week had been to so many shops I had to start again. The main thing is the hard limit, even if you change the multipliers the hard limit is still there changing b1650 it still thinks its the same but you get more percentage. Just make sure it is getting full throttle when it should be. Cold starts is easy to sort I am more concerned how your idle is with the TP% trimming. As simon mentioned he has also opted to not drill his which is a personal preference. But he also said his idle does move around a little because it steps 0.4% at a time. I'm a little different and I the way they end up changes the note of the car, A lot of commodore owners approached a friend of mine during powercruise asking the same. The airspeed buffer works wonders

Another thing that must be considered is dynamics. Again I base these ideas on speed density. Tuning the MAF at idle takes longer. SD gives a better idle with big cams. Also most tuners in US are using MAF based tunes. When they go over to speed density with e38 they are treating it like a ls1 o/s(not altering dynamics) and if dynamics isn't right it results in very poor drivability and lag in throttle response. WOT tuning is also an issue. With stock dynamics and SD the car will ramp up a nice number and afr curve then on the street low gears will be lean at WOT with lean spikes during shifts resulting in very poor performance. The first thing they do is put the MAF back on in which if they don't know what there doing is a very good idea.

[ringram]

Yeah I think cold start dynamics needs tweaking. More fuel required. Though once warm its fine. I have too much throttle response with 440 cubes and a 227 cam as it is.