My first time tuning - 370 in a BMW! Need some input on hot starts.
08-18-2015, 10:19 AM
#1
My first time tuning - 370 in a BMW! Need some input on hot starts. My current toy is a 2001 BMW 540i with a forged 370 (originally an iron 6.0 out of a 2002ish truck). Built T56, 3.91 M5 rear, yadda yadda. I have been through various iterations of tune and motor from a junkyard Express 6.0 (stock interally) all the way up to the most recent build. From the time I originally swapped the car, I left the tuning to local professionals, and although they did a mostly good job (under WOT at least), the driveability/idle/starts always left me looking for that OEM feel. So, I am jumping into DIY tuning head first and seeing if I can get this thing to start and putter around like a luxury car, while still ripping around like the sports sedan that it is.
While browsing through the general tune I did find a few interesting things - such as the fact that 3 separate tuners (mail order, local buddy, and local pro tuning shop) have had their hands on this PCM while it has been in my possession, and torque management was still turned on. The transmission type was still set to 4L80E (probably didn't matter much), the rear gear and tire size was incorrect (left on old settings),
In case anyone is interested here is the build thread for the car:
https://ls1tech.com/forums/conversio...-bmw-540i.html
and for the fresh motor:
https://ls1tech.com/forums/generatio...ld-my-bmw.html
Here is the modification list so that we are all on the same page.
2002 LQ4 Iron 6.0 pulled from "steak" truck - craigslist yeehaw special.
Stock crank, .010 undersize mains
Sealed Power Speed-Pro flat top pistons (4.030" Bore)
Forged I beam rods, ARP rod bolts
New Clevite P rod bearings, cam bearings, main bearings, etc
GTO oil pan, pickup tube, windage tray
Sticking with the same cam, TSP 228R (228/228, .588/.588 @ 112*)
Top end:
stock 241 heads,
No porting, stock otherwise
GM 6.0 MLS headgaskets
ARP headbolts
TSP pushrods, dual springs, titanium retainers
Intake:
Stock LS6 intake manifold
LS6 throttle body
3.5" aluminum intake pipe with stock LQ4 MAF, large cone filter
Stock LS6 fuel rail, with 42# Ford Greentop injectors
Exhaust:
CTSV cast iron manifolds with the cats removed, into OEM BMW exhaust with 2 secondary cats.*
3" QTP Cutout/exhaust dump before all mufflers/ resonators
Drivetrain: Stage 2 T56, 3.91 M5 LSD rear.
The PCM is out of a 2003 Express Van 3500 (6.0, 2WD).
The issue I am encountering currently is a hard start condition when the engine is warm/hot (say, above 150F or so). I have read about this issue on other cammed LS Gen 3 cars and it seems that it is related to an imbalance of fuel and air while the engine cranks. From what I have read it looks like the cure is either added airflow during cranking, or reduced fuel by changing Cranking VE, Startup Airflow Initial, and Cranking FA Mult Stage 1. I spent a good 3 hours this evening learning the effect that changing each of them had on the quality of the startup. I think I improved on what it started as, but it is still far from good. The car starts AWESOME when cold - just a revolution or two and she's already thumping along. My goal is to recreate that great start condition at all ECT values.
Here is my tune file, and a log of a Hot Start. Keep in mind that this is with Cranking VE, Startup Airflow Initial, and Cranking FA Mult Stage 1 all modified from factory settings. It's better than it was when I started but still needs lots of work to be as good as the cold start is.
If there is any information I left out please let me know, and I can update the thread.
Thanks again!
While browsing through the general tune I did find a few interesting things - such as the fact that 3 separate tuners (mail order, local buddy, and local pro tuning shop) have had their hands on this PCM while it has been in my possession, and torque management was still turned on. The transmission type was still set to 4L80E (probably didn't matter much), the rear gear and tire size was incorrect (left on old settings),
In case anyone is interested here is the build thread for the car:
https://ls1tech.com/forums/conversio...-bmw-540i.html
and for the fresh motor:
https://ls1tech.com/forums/generatio...ld-my-bmw.html
Here is the modification list so that we are all on the same page.
2002 LQ4 Iron 6.0 pulled from "steak" truck - craigslist yeehaw special.
Stock crank, .010 undersize mains
Sealed Power Speed-Pro flat top pistons (4.030" Bore)
Forged I beam rods, ARP rod bolts
New Clevite P rod bearings, cam bearings, main bearings, etc
GTO oil pan, pickup tube, windage tray
Sticking with the same cam, TSP 228R (228/228, .588/.588 @ 112*)
Top end:
stock 241 heads,
No porting, stock otherwise
GM 6.0 MLS headgaskets
ARP headbolts
TSP pushrods, dual springs, titanium retainers
Intake:
Stock LS6 intake manifold
LS6 throttle body
3.5" aluminum intake pipe with stock LQ4 MAF, large cone filter
Stock LS6 fuel rail, with 42# Ford Greentop injectors
Exhaust:
CTSV cast iron manifolds with the cats removed, into OEM BMW exhaust with 2 secondary cats.*
3" QTP Cutout/exhaust dump before all mufflers/ resonators
Drivetrain: Stage 2 T56, 3.91 M5 LSD rear.
The PCM is out of a 2003 Express Van 3500 (6.0, 2WD).
The issue I am encountering currently is a hard start condition when the engine is warm/hot (say, above 150F or so). I have read about this issue on other cammed LS Gen 3 cars and it seems that it is related to an imbalance of fuel and air while the engine cranks. From what I have read it looks like the cure is either added airflow during cranking, or reduced fuel by changing Cranking VE, Startup Airflow Initial, and Cranking FA Mult Stage 1. I spent a good 3 hours this evening learning the effect that changing each of them had on the quality of the startup. I think I improved on what it started as, but it is still far from good. The car starts AWESOME when cold - just a revolution or two and she's already thumping along. My goal is to recreate that great start condition at all ECT values.
Here is my tune file, and a log of a Hot Start. Keep in mind that this is with Cranking VE, Startup Airflow Initial, and Cranking FA Mult Stage 1 all modified from factory settings. It's better than it was when I started but still needs lots of work to be as good as the cold start is.
If there is any information I left out please let me know, and I can update the thread.
Thanks again!
08-19-2015, 02:18 AM
#2
I have a far more radical setup than you. I would advise not to mess with any of the startup fueling tables. I did that and eventually returned them all the stock.
You need more airflow in the startup tables. Set to 4g/sec. And add 2-3g across the board in the startup friction tables (you'll notice they are ECT dependent). The factory fueling tables are generally right for startup. The airflow is what needs to be adjusted (assuming the injector data is correct).
You need more airflow in the startup tables. Set to 4g/sec. And add 2-3g across the board in the startup friction tables (you'll notice they are ECT dependent). The factory fueling tables are generally right for startup. The airflow is what needs to be adjusted (assuming the injector data is correct).
08-19-2015, 08:48 AM
#3
i'll give that a try. I did play with startup airflow, and although it helped, it flared WAY up once it started (2500rpm+), and then slowly settled. I understand this can be fixed with the decay setting in that table, but it doesn't seem ideal. that's why i wanted to pull fuel.
08-19-2015, 12:27 PM
#4
Thanks JakeFusion. I have been fighting a slow start condition, cold start and hot start. Of course, it isn't very cold here. I was getting ready to get a new starter and battery cable. I increased the startup air and it fires right up, and I checked, it starts good when hot also. 
This is on a E40 PCM.
This is on a E40 PCM.