E38 idle tuning

[hymey]

Whats your afrs at cold Rich?

cheers

Joel

[ringram]

If I ever get my car back from the guys learning at my expense Ill tell you!
I took the WB out for warranty work a while back. Ive been without my car for basically a year, its just gone back for an oil leak less than 1000 miles after a £10k rebuild.
Not pleased.
Anyway, Ive no garage, so need to wait until its semi dry to roll under the car and fit the WB again. Ill get some NB O2 MV info for a rough idea if/when I get the car back!

[Tordne]

Despite originating in Australia it is a British car now so it is supposed to leak oil. Seriously hough, that is very bad for the amount of time and money you've put into that thing. I take it back now, it may just have been cheaper to get the ZO6

[hymey]

Is it a rear main leak Rich? I have heard some guys puting the reverse lip seal in back to front to combat oil leaks, especially with engines with forged pistons with larger ring gaps and piston to bore clearance, they tend to have a little more blow by and can cause this.

[hymey]

Just an update, Thanks to Simon and a few tips(which were actually brought up at the beginning of this thread). I was able to get my best drivability results with this cam 6L L98 upgrade. The cam is a 233 238 on 110+2 @ .600" lift. After I installed the cam I nearly died when I seen how minimal the ptv clearance was on the intake. All I can say it is safe for a race engine and more then what some people run so I spent a bit of time trialling differnt pushrod lengths to minimise preload just incase it gets valve float and pumps up. After a few hours I was very happy with the valve train setup,

This cam has 15.5 degrees overlap the end result I am very pleased with, performance of the engine is the best I have done "cam only" by a long shot, but the drivability was also the best I have done. The moderate duration tight lsa cams work very well and will behave if tuned correctly.

Idle was very simple. This time proportional tables zeroed out, 6mm hole in TB. B1652 1.15 and B1651 0.6. Integral tables, well looks like GM sacked there old tuner because they look a lot different, and it appears to me there tuners are learning the e38 at the rate which everyone else is...very slowly. lol. I tweaked the coast down integral table making it a little more aggressive, timing correction as per normal, 15 degrees idle timing, idle air was 8 g/s(mind u I didnt even follow the steps I normally do I just plugged the values in above and left it) Getting rid of LT idle trims helps a lot. Makes it so much easier. I ran 30 degrees in coast down table and ran less airflow on coast down to stop the chugging around roundabouts. Drivability tune was then complete but I decided to go on a 20 km fuel economy course and just keep an eye on the engine parameters. In 6th gear at 1500 rpm the car sat at 100km/h but it had a surge that was annoying and wasn't helping economy. Typical of a cam of this size. The air fuel was on the rich side in the high 13s, I tried even 13.2 it still had the problem. I new then there was a reversion and atomization issue in the chamber. The Ls7 injector does not have the best spray pattern. I decided to follow some ideas I had doing aftermarket engine management and that is to trial injector timing. By firing the injector earlier while the valve is still closed it gives the fuel more time to atomize. In GM's stock tune it is setup to allow for maximum fuel economy and emissions. A late injector fire that leaves little amount of fuel residue on the port wall.

A trick with injector timing is to advance it till the afrs are at there richest for the given pulse width. This proves that all the fuel is atomized that enters the chamber. If you keep advancing afr can drop off a little leaner which means the fuel maybe suspended on the port wall. Standard at 92 ect the injector timing is 220 degrees then the rpm table adds to this as rpm increases. I was able to go up to 400 degrees total at idle and cruise then build to around 480 at peak rpm. This cam took a lot more lead then most others do as well 31 deg at peak torque was MBT. But cruise at 38 degrees was terrible. I went upto 50 and it still wanted more but the engine did love 50 at cruise. With the injector timing and ignition timing dialled in the vve took some more work. I was running much richer this was a good sign, I was able to lean back to stoich at cruise and have perfect drivability. Running 30 degrees in coast down timing and correct coast down airflow eliminated any chugging on and off the gas. I stopped for a quick drink and let my mind rest...just for a minute and made a flash for minor timing changes. On the trip back home over 20km of country and then city driving it was a totally different car. It drove like stock just as it did when the customer dropped it off. I was very happy with the outcome. From 1000rpm in 6th pulls away like a stock cam,Most stuff of this size carries on like a pork chop! All up 6 hours work on drivability. Airflow , timing, vve and injector timing all playing equally important roles. Injector timing makes a big difference on high overlap cams. You can reap awards with aggressive cams and drivability if you focus on these areas.

Cheers

Joel

[VEV8]

Joel what settings do you normally run for "airflow correction coolant multiplier"

[swingtan]

VEV8, you need to run what the engine wants and every engine combination will be different. It's also very dependant on your base idle airflow. A guide for working out that table is to log the spark and see how it compares to the tune settings. The ECM will try and control the idle speed by adding or removing spark advance. If the logged spark is higher than the tune settings, add more air. If the logged spark is lower than the tune settings, remove some air. So all you need to do is to watch the spark as the ECT rises to see what sort of airflow is wanted. Remember to rest the learned data before trying this though.

Simon.

[VEV8]

Thanks Simon...So it doesn't necessarily matter what the factor is, i can just alter minimum idle airflow to suit. But does the factor also play apart at higher rpms as well
I already knew about watching average base spark at idle to get an average airflow required.. originally my OS was a factor of 2 & was scaled down to a factor of 1 at full operating temp.. Later OS i seen were 0.5 down to .25

My setup is a 224/228 cam with a 5mm hold drilled in throttle body,13* idle spark.... with my original settings i had a minimum idle airflow in the 6's (which i thought was quite low for that cam) and still had a rather high idle

I do have it idling quite well using a setting inbetween those two original settings, just wasnt sure it was a common rule to change this setting or just change minimum idle airflow only

[hymey]

Try zeroing the proportional table. It uses a PI controller. P being proportional learnt data. You can use a very slight correction factor in integral tables. And moderate timing correction. The e38 is so fast it will try and adjust timing to maintain idle speed. If the rpm dips way to fast it is a sign the min idle airflow is to low. If it hangs or timing is very low try removing some timing. The reason why I change B1652 and 51 is they have a big effect on drivability. But I run B1652 high enough that it will allow enough air on cold start. Usually 1.20 B1652 0.7 B1651 is a good combination with around 7 g/s across the board in min idle airflow. I have tried every combination possible with idle tuning I always end up around here. There is a very high possibility that the "learned" data will still be there, ie the Long term idle trim. You have to zero this out in the tune to get it right. 6g/s-7g/s is about right. Some people have had good results not drilling the TB aswell. But there min idle air will be much higher. I personally get them idling better with a hole but everyone has there own methods. Not zeroing learnt data will give you a world of trouble. The main method I use will allow you to find best idle air without worrying about the learnt data but when max idle area is raised the idle lifts back up. Thats why if I drove around for a few hours and then raised the max idle area value the idle would not hang as it had learnt correctly.

As simon and I discussed a few months ago. Zeroing proportion is the right thing to do. (All proportion tables) Then you will be very close.

My email is joelprince@bigpond.com if you want me to look over your tune feel free to email me or Simon. We don't charge here lol , just help each other out.!

[swingtan]

Thanks Simon...So it doesn't necessarily matter what the factor is, i can just alter minimum idle airflow to suit. But does the factor also play apart at higher rpms as well
I already knew about watching average base spark at idle to get an average airflow required.. originally my OS was a factor of 2 & was scaled down to a factor of 1 at full operating temp.. Later OS i seen were 0.5 down to .25

Yes, it does matter. The colder engine weill want additional air flow to help it idle and the ECT correction factor works across the whole base idle airflow table.

My setup is a 224/228 cam with a 5mm hold drilled in throttle body,13* idle spark.... with my original settings i had a minimum idle airflow in the 6's (which i thought was quite low for that cam) and still had a rather high idle

A 5mm hole for a cam that size is massive, way too big IMO. It'll cause all sorts of high idle and hang issues that may not be correctable in the tune. I'm running a 220/224 with no hole and I can tune it to idle like a stocker or have a big cam lope. I'd also look at increasing the base idle spark toward 20' to help with the idle. Don't forget to adjust the high and low spark tables to suite though.

I do have it idling quite well using a setting inbetween those two original settings, just wasnt sure it was a common rule to change this setting or just change minimum idle airflow only

I've altered the ECT tables a lot, as I've done on most other tables..... When you mess with the mechanics of the motor, most of the tune settings will need to be tweaked to suit the changes.

For comparison:

My hot idle is 700RPM
Min airflow is set to 7.8gm/S

For B1602: fromt an ECT of 80'C down to 20'C I have a steep curve startingfrom "1" @ 80' and rising to just under "1.7" @ 20'. The graph angle then drops off to a value of "1.8" @ -140'

The E38 and 6lt motors like to be over fed idle air if you want it smooth. The E38 seems to do better at reducing idle speed, than increasing it, so err on the higher side and it will be easier to tune. Also as Joel says, for B1845, zero out 2 to 3 cells above and below "0" for each "idle correction type" then blend the remain cells. Once you have optimised the idle tune, the Proportional table becomes less important.

Simon