E38 idle tuning

[hymey]

I thought so it happens a lot with e38s but i set the timers all to 0 and the test enable at 100 rpm in all of them now and they fire right up.

cheers

[The Alchemist]

Legend !. Thanks Swingy...
Now if I could only get the throttle to open more than 20.4% at any given time to help cold idle reach target of 900rpm .....Tried B1651 52 at 4.5 and still no improvement...any ideas
?

I had a chat with Mike yesterday and after going back and forth a bit, Mike realised that it only occurred when the MAF was disabled. We reset all the DTC types and then tweaked the MAF tests to ensure the MAF was failing and it all came good. We think that the ECM was taking too long to fail the MAF, so it's think there was no air flow, pull the fuel out and then by the time it realised the MAF was dead and it swapped over to the VVE, it was just too late and the engine died. After tweaking the MAf tests, it's all good now.

Simon.

[hymey]

This is where I get stuck and I must say I am a bit at fault for not mentioning the different o/s. I am in bed with the flu today and while it sux I get to go on the forum lol. B1602 varies from o/s to o/s some are topped out at 0.5 cold start others are at 1.0 cold start. A lot of the 2007 cars and also the VZ e38s have it to 1.00 at cold hence why they go the bigger hole they have to much air. I use the later table in these cars and run the bigger hole and they idle very nice. I have done two this week, one I built the engine it has a 239 239 lsl cam and runs in SD closed loop, the other is a 2008 VE maloo I put a 230 xfi 230 xer 111+2 cam in it. They are both well behaved. What I do in some cars(when I am time limited) is turn off the proportion which is the learning parameter, leave integral stock and flatten the hole min idle airflow table and tune for best idle air at 800 rpm. Then also also at 1000 rpm. I set the idle at 800 then put 4 g/s higher in the 600 rpm table, 2 higher at 1200 then a 1000, and 3 higher at 1600 and set max idle air at 1.50. This combination gets me in the ball park. I then push the multipliers around, So I get it idling at say 800 rpm and raise the multiplier till the TP% comes up and it hangs a little then back it off .05, see how it looks then .1 from the target and I know my bottom hard limit is reached. Doing this with a 5-7mm hole with mid size cams makes them idle so smooth and when i post the vid up you will see why I still use the larger holes, they just behave so well. Max idle area will change that upper limit to a degree but once you hit the upper limit thats it which changes in some o/s. My only suggestion is you try the multiplier B1602 in cold ects. Try and raise them it may come up to 21-22% region. It may work or may not I have not had the issue.

Another thing with maf tests in sd mode. If you have the airflow squared away with the maf, you have the scale right, and the vve correct. Sometimes when you disconnect the MAF you will notice after 4 seconds or so you feel you have no throttle and it bogs a little then goes. That is the maf still doing its tests. I alter the diagnostic tables aswell to stop this.

I remember back in 08 when I was drag racing my car- bolt on at the time I was stopping it starting it waiting to go through scrutineering and I was starting it engine would conk out and stall, then I would reflash it would start. Then stop a minute later same thing would happen just like your customers car. The scrutineer was going off , I ended up getting it started and just not turning it off, I eventually worked out to drop the timer, The VZ 1 meg o/s do this aswell.

Cheers

[The Alchemist]

" My only suggestion is you try the multiplier B1602 in cold ects. Try and raise them it may come up to 21-22% region. It may work or may not I have not had the issue."
Hi Hymey thanks for your help ...this table I already have at "2" up to 32deg C as per an earlier suggestion you made a while ago....20.4% seems to be the max it goes to .....
you can see how it stays on 20.4 right up to about 55deg c before the spark has lowered enough that the TB starts to drop to 19.5 and so on .... Even when fully warmed up and you engage drive but remain stationery the TPS goes to 20.4% and the timings at around 28 deg to try to acheive target idle of 800rpm...

[swingtan]

I've been playing in Excel a bit to try and confirm . deny a theory I came up with when talking with Mike yesterday. My theory is that the E38 uses both absolute throttle blade position and effective throttle area (as a percentage). But there is no indication as to which is being used when. This helps explain the old PE TPS graph that I went through a couple of years ago.

Anyway, I've been plotting the data out and it seems to fit in a general sense, but it's not quite there. It has helped explain a little about the hole drilling method though....

When calculating the absolute blade position and comparing it with the effective throttle area, we see that at low throttle openings, the effective area rises sharply compared to the blade position. This is because the blade tip moves through an arc from the top / bottom of the throttle body, toward the centre line. The throttle effective area is then the "gap" between the blade and the inner surface of the TB. Initially this gap widens quickly, but after a certain point (about 35% of blade position) it slows down and the change in effective area nearly matches the change in TP %. Then a short time after, the effective area changes slower than the TP% (about 65% of blade position ).

How this relates to the holes in the throttle blade can be seen when looking at the nominal Idle TP%, seeing the matching effective area and then looking at what the hole does to the situation. Here's an example.

My car normally idles at around 6% as indicated via the ETCTP PID. This gives me 8gm/S of idle air and all is well. At this pint I have an effective throttle area of about 21mm^2 which is 0.44% of the total throttle area.

If I drilled a 5mm/Dia hole in the blade, I'd introduce an additional 20mm^2 of effective throttle area, which would double the effective throttle size. So I'm going to assume the ECM will almost close the throttle to maintain the desired airflow. At this point, the ECM can not 'reduce' airflow, as it can't block the hole in the TB blade. So you have effectively removed the ECM's ability to reduce the airflow below this point.

Personally, I've never drilled a hole, possibly because I've never had a car with a big enough cam to need it. We know that the E38 likes to over feed the motor with air, as the engine seems to idle better, so the hole seems a good method to hard limit the minimum air flow. I'm pretty sure you can still do it in the software, but you can't make the hole smaller in software....

There are a couple of other things I'm still pondering....

The difference between {B1650} and {B1701}. One is set for a 78mm dia throttle and the other for a 102mm Dia throttle. Why the difference? Something to think about.

Simon.

[hymey]

Yeah depends on the B1602 parameters simon. If I run no hole, it idles quite high percentage, if I drill the hole it reduces by 4%, this is real testing though. The only reason I do it is to stop the pulsing of the air at idle, you hear the slight air differences. So if I use sae.tp it idles at 20% idle with say a 232 234 112 cam. I only have 1 % left for cold start. If I drill a hole its back to 15-16% roughly. But the issue is with the L76 o/s is they won't idle less then that region, whereas the later o/s will. Hence why they have "0.25" at 92 degrees in the B1602 multiplier. Change to this like Holden did in all there o/s, then 8 g/s really is much less g/s and you get real world figures. All the cars I do idle stock even with 239 cams, they wont get there otherwise. I have tried the car idling hot. No hole, And then worked on the integrals for two nights straight. Im bipolar and had a bit of a manic stage for 48 hours of solid e38 tuning a week ago, I tried the stock B1602 settings and then worked hard on the airflow tables and integrals also altering integral limits (which helps) I would aim first at a thousand and it idled OK, but the rpms moved around slightly and it was very choppy. I would increase the hole, alter the airflow tables and also changed the B1602 settings to the later setup, and the car progressively got better. I also done away with the L76s horrible pcv system and went to the later L98 setup and valley cover. I just kept going bigger (I have a spare blade) with the multiplier set to 0.35 max at lowest till I found the hard limit, then went down to 0.25 at 92 degrees, and min idle air went

10.00
10.00
6.00-----800 rpm
7.00-----1000 rpm
9.00
10.00

Now big cams and blowers need a TONNE of air at cold start. I have plenty at 20.9% cold start just like a stock car then work down to 6 g/s at hot like a stock car so the whole system is essentially working factory like. You can change the effective area values. I have never changes these and dont want to alter wot settings which it may do?

I ended up with 7mm in the 239 car. I tried going smaller just to test it as a few guys with bigger cams then this car suggested they had but I ended up with the best results doing this method. I never used an excel sheets or data logs. I just listen to the motor and do whats best for it and the customer and they drive stock. The bigger hole also makes them a lot smoother on transition and also start a lot smoother. The main reason is for the airflow buffer. Simon your car would have a larger area going from the passenger rear tappet cover to the manifold which will act as a hole itself and give extra air plus act as a buffer. The L98s/LS3s have the later restrictor in the cover which doesnt appear to give any more air. If I block it or not it does not effect idle timing. If I did that on Bens L76 it would change the timing quite a bit, just thought I will let u know that. I am pretty sure I have it covered now to the best of my knowledge. If I started again on this thread I would change a few things I do but overall it is the same out come and I think to this day I am pretty confident with what I have done with idle tuning. I have been thrown a lot of curve balls. I know some guys like to change things just in the tune but it is still a motor, like make the cam timing retarded and intake biased and you will work a lot harder in the tune to get it right. I have a method that is 100% proven, the only thing I do differently now is ensure the L76 pcv systems are modified and also work on the B1602 multipliers to help set upper and lower hard limits. I do also do what Simon does and that is zero proportional tables and keep integrals populated and play a bit with that method aswell as max idle area. The rest just comes up with the tuners ability to see the problem as it arises and how to go about fixing it.

[The Alchemist]

so it seems that 20.4% is THE HARD UPPER LIMIT for my Max idle % ? Does this sound about right...ie even increasing b1651 52 from "1.8" up to "4.5" did not change the max idle over 20.4% at any given time....Looks like drilling a hole in the TB IS the only option left for me ...surely other people with S/Chargers must have had similar problems?

[swingtan]

Try increasing {B1650}, maybe it'll allow for more throttle.

[ringram]

I had same issue, not enough air no matter what min idle airflow. As above b1650 definitely puts more air in.
438 cube with 230\240 cam.

[swingtan]

Thanks ringram, I thought that may work. Was I right with increasing B1650 to allow for more air?

Simon