E38 idle tuning

[hymey]

They definately like more air then less, I normally run a hole around 4-5mm for that size stick to get them idling how i like and end up around...6gm/s with a dead smooth idle at 800 rpm and 13.5-14 afr, 15 degrees timing (no correction) and zero lope. That size hole wont cause you any dramas if u set max idle air up correctly and min idle air. Twin turbo stuff with stock cams I drill 3mm holes to help the surging at idle and pulsing by the compressors.

You will find they like more air then less. My 248-254-106(admittly a carb) using stock pcm for spark idles at 20 degrees timing at 800rpm and NO spark correction, And it idles like a 224-228 would in LS1 terms at 14:1 afr and idle very smooth. The trick to this is consistent idle spark and airflow. Any changes in airflow and spark will disrupt the idle to a degree and cause it to hunt up and down by 50-100rpm. My carb has a 4mm hole drilled in each butterfly (yes four of them) so they sit in the correct position with 40 thou of the transfer slot exposed. My TK cam had an 8 mm hole in the TB I had to keep going bigger with the airflow "maxxed out".

I still prefer the original method of maxxing out max idle air. I can arrive at the point a lot faster. The integral correction is still taking place otherwise I try to eliminate that. The amazing thing is if you "lock out" the air you can then push the timing up and down(with no correction) while datalogging and engine running, I keep the air fuel in the high 13s and then raise the spark up and down until I get the best idle vacuum. In most cases then I run very minor correction in both timing and throttle like -3 deg max for timing and 0.080 for integral as a max number. Thats how I get them with a standard idle. Usually at the drags/etc combined with varex mufflers it passes as a 100% stock engine at idle. Fuel economy drastically improves around town and it really passes as a stock car to drive, Most people even if they love a tough sounding engine always go this way as it is so much better to drive. Most tuners just try to get the car driving and eliminate hunting and stop there. Go beyond that. Lock airflow, adjust timing with DVT. get in open loop Note down the max idle air, and adjust timing, increase air try different timing again. Once you arrive there establish min idle air and get the corrections to a minimum with a bypass in the TB. Cold start and drivability it all goes hand in hand.

[VEV8]

Thanks Joel & Simon... i am pretty close now.. i zeroed the proportional table, set max idle air to 0.7 & 1.0, 15* idle spark, warm idle at 770rpm, 7's in minimum idle airflow, coolant modifier is 0.6 when warn (still had hanging idlle & low spark with anything more then that)

Its very close now i think.. may need to look at spark correction in gear setting to get it even smoother

[swingtan]

Oh it's an auto? Guess what, autos in gear are the easy ones to tune :p. The additional load of the auto helps smooth out the idle a lot. Good news that you're getting close though.

[hymey]

What o/s is it some of them run 0.25 with the coolant multiplier hot and 0.5 cold. Others run 1.00 hot and towards 2.00 cold. Why? I dont know. If I use values from my o/s which has 1.00 and put them into an o/s which has 0.25 at full operating temp the idle hangs! There still both e38s and both end up with the same min idle air but the multipliers are different. Just something I picked up. If u do want to experiment with a smaller hole I have a spare TB here somewhere I can send down to u.

You can also setup B0148 for OL fuelling tune the car with that then enable PE at 90kpa. I have great results doing this. Use Simons VVE tuning guide. I have been chatting with Girch from LSX tuning, he runs 90% of his VE;s with the MAF. Something Simon and I have preached all along and I do remember Girch actually disagreed with me on this 3 years ago but 12 months ago he came around and admitted that MAF tuning is the go and will deliver the same rwkw top end and have much better drivability. Something I thought I would add if you are currently in tuning mode. To put in perspective Simons engine is the most tuned LS engine in the world by far I would think, He has tried all combinations in different cells and still goes back to the MAF. It does take longer to get right as you dial the vve in first then scale the maf. But maf tuning is definately fun and enjoyable and the fuel curve is rock solid and consistent with awesome response. THought it would be wise of me to preach it to you! You can also command a 16:1 stoich in OL MAF and use B0148 to multiply it like a ls1 cos. Run it lean at 15.5:1 cruise and 14.7 idle etc. The OL maf has better results the dynamics work so much better and the car has better partial throttle feel which helps a lot at cruise.

BTW I live in Gladstone another QLD e38 tuner!

Cheers

[VEV8]

Thanks Joel,

Im currently running CLSD (dont have any experience with maf tuning) and running a reasonably rich VVE and bringing PE in earlier 65/70KPA to be safe.. I will post my tune for you guys to run your eyes over and see if anything obvious needs doing that i have missed (Dynamics ect).. I would like to run a little leaner in the cruise cells and idle for fuel economy

[VEV8]

current tune

[The Alchemist]

COLD START.efi
Hi Guys,
Got this supercharged ute back with starting issues. TVS2300, mild cam 230ish, other supporting mods etc. What its doing is: the 1st cold start starts perfect and runs no problem, takes a throttle, mixtures good etc etc, let it run for a while say to 40 to 50deg C, turn it off and start again immediately it will start fine 1st crank but as it comes down to idle it just stalls and each successive try to restart it gives the same stalling issue. Walk away have a coffee calm down, try it again and it starts and runs perfect. I have included a log and what is most noticible is:
on the 1st start of the day and the problem ones is that the IPW drops out to 0.9ms just after starting and the LOAD drops out as well to almost nothing even thoug the engine is at 1000rpm or so. Pumping the throttle does nothing as the engine is on its way down by then and the IPW just keeps sitting on 0.9ms.
The ECU is configured MAFLESS with the MAF unplugged.
Any ideas on where to look? Thanks,
Mike

[Naf]

COLD START.efi
Hi Guys,
Got this supercharged ute back with starting issues. TVS2300, mild cam 230ish, other supporting mods etc. What its doing is: the 1st cold start starts perfect and runs no problem, takes a throttle, mixtures good etc etc, let it run for a while say to 40 to 50deg C, turn it off and start again immediately it will start fine 1st crank but as it comes down to idle it just stalls and each successive try to restart it gives the same stalling issue. Walk away have a coffee calm down, try it again and it starts and runs perfect. I have included a log and what is most noticible is:
on the 1st start of the day and the problem ones is that the IPW drops out to 0.9ms just after starting and the LOAD drops out as well to almost nothing even thoug the engine is at 1000rpm or so. Pumping the throttle does nothing as the engine is on its way down by then and the IPW just keeps sitting on 0.9ms.
The ECU is configured MAFLESS with the MAF unplugged.
Any ideas on where to look? Thanks,
Mike

So it starts up after initial start up. Thats a good thing, but what is your Min airflow set at? Also your airflow correction to coolant multiplier may need a tweak.

I wouldnt know where to start on the IPW

[hymey]

I had this the other day, There are some tables that help the engine recover airflow if it dips. B1833 and B1844 you can set these to less then 1.0. It seams a strange issue. Remember with the engine colder it needs more fuel on cranking then hotter. I have found that the cammed engines require much less fuel on crank . B8062 try this set down to 75%,

If an engine does this it normally means it is performing tests to see if the maf is there, the e38 will perform these tests over a few seconds on start up. Some engines actually are more sensitive then others ( and some e38s) unfortunately I have found that all cars and e38s respond differently, they all throw curve balls so when you think you have it nailed it comes back and bites you.

I think it is definately fuel only issue before you change any other settings try this.

C0310 set from 1 to 0.

C0312 set from 400 to 100 rpm. Ensure all other parameters in maf diagnostic tables are completely stock. I have seen this scenario on my car.

Make sure P0101, 102 and 103 in DTC type are not set to not reported, they should be B: 2 trips, emissions related or C: Non emissions.

[swingtan]

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.