Help with Gen 3 8.1 twin turbo set-up

[JonathanLeskewich]

Hi Everyone, I have had my set-up running for about 2 years now. I would like to move more into boost, but it's difficult because it's a motorhome so it is almost always towing in a way because of the weight. Where I am stuck is that my EGT's keep climbing in boost. AFR is 10.8-11.2 and rpm is 2200-4200 when this happens. I am currently running only 3 psi of boost and being cautious. Timing is set to average of 8* in this area (0.9 grams-1.2 grams in the cylinder). I have a big intercooler in the set-up and IAT's are only 3*C over ambient. So 33 C on a 30 C day.

I am getting only very rare random knock mostly in throttle transition so I don't think the timing is causing knock really. I just don't know if 8* is way to aggressive and which way I should go with it (this is the first motor I have tuned). I saw some sample tunes with timing down to 0.20* and some as high as 20* in boost?

EGT's climb over 1550 F in about 30 seconds. I am running 2 bar mod, PE and BE enrichment crossover.

Here is the tune file
2 Bar VE 10 BE plus PE.hpt

Thanks for the help in advance!

Jonathan

[blindsquirrel]

Low timing causes high EGTs. Raise it a bit at a time, while monitoring knock of course, and see how it responds. 8* is crazy stupid low and will cause more problems than it prevents.

[JonathanLeskewich]

Low timing causes high EGTs. Raise it a bit at a time, while monitoring knock of course, and see how it responds. 8* is crazy stupid low and will cause more problems than it prevents.

Ok I will try that, thanks. If knock comes in what would you do at that point?

It is a very high load engine since it is pulling around 12,000 lbs all the time (at least). That is why I wondered if timing needed to be different than everyone else.

Sure seems like "fire" is running down the headers in a way though.

Jonathan

[5FDP]

With that low of psi and that rich of fueling I don't see why you couldn't run 13-15 degrees no problem. If you had E85 you could run even leaner and more timing no problem.

I want to see a log of this too. You have the factory injectors and you are running boost. I doubt you have enough injector for this thing too. Your duty cycle has to be over 100%.

And that PE/BE and your VE table is a complete trainwreck. I don't know how you are trying to tune that VE table but whatever you are doing is not working.

If you are having to rape the VE and boost enrichment with that much fuel you have no where near enough fuel flow with the injectors and pump for this setup.

Speed density isn't set right either, you want the MAF dtc's to be on MIL on first error. Turn off COT as well in the fuel tab.



So before you keep driving this and possibly hurt that somewhat fragile 8.1 you need to fix your fueling problem ASAP.

[JonathanLeskewich]

Thanks for the help! Can you elaborate on why my PE and BE are so bad? That would be helpful.

I haven?t finished tuning the VE table yet, so I admit it?s not great. If I set the MIL light I loose throttle and cannot drive so that doesn?t work for me. Is it necessary? Or is this only an indicator?

Thanks!

Jonathan

With that low of psi and that rich of fueling I don't see why you couldn't run 13-15 degrees no problem. If you had E85 you could run even leaner and more timing no problem.

I want to see a log of this too. You have the factory injectors and you are running boost. I doubt you have enough injector for this thing too. Your duty cycle has to be over 100%.

And that PE/BE and your VE table is a complete trainwreck. I don't know how you are trying to tune that VE table but whatever you are doing is not working.

If you are having to rape the VE and boost enrichment with that much fuel you have no where near enough fuel flow with the injectors and pump for this setup.

Speed density isn't set right either, you want the MAF dtc's to be on MIL on first error. Turn off COT as well in the fuel tab.



So before you keep driving this and possibly hurt that somewhat fragile 8.1 you need to fix your fueling problem ASAP.

[JonathanLeskewich]

Here is a log. I don't know how to log injector duty (the math). Seems like I have had enough fuel so far. Might have different injectors in the motorhome 2 bar map ve 10 BE and PE.hpl than in a truck... its a slightly different engine build in a motorhome.

I am using the goat rope garage version of tuning VE. I was using MAF only last year this is the first time tuning VE for me.

Can you let me know what you think of the knock events... I think there are only 3 (in this log) or so, so pretty minor I think they are false knock, but I don't know for sure.

Jonathan

Thanks for the help! Can you elaborate on why my PE and BE are so bad? That would be helpful.

I haven?t finished tuning the VE table yet, so I admit it?s not great. If I set the MIL light I loose throttle and cannot drive so that doesn?t work for me. Is it necessary? Or is this only an indicator?

Thanks!

Jonathan

[5FDP]

The injectors are the same, they are both 31lb/hr.

Your data log shows you the injector duty cycle, it's in the top box on the graphs. By 3,500rpm you are already well over 90% and by 3,800 the duty cycle is past 100%, so it's basically just staying open.

My point about the BE and VE is that you are asking for a 10.50 AFR but your VE table is so extremely inflated just to hit that target. That is why the injectors don't have enough for this. If you want to add more boost you need more injector because you already don't have enough as it is.

Also if you are tuning the VE you can't have your fuel trims working. Your short term and long term fuel trims will be skewing your data and right now you have your long term fuel trims being carried over into power enrichment which isn't good.

We also assume this is on premium 91/93/94 octane right. I also think that once you get that stuff fixed you'll be able to adjust your PE and BE a little better so that it's not smacking it with a 10.50 AFR at 2 psi of boost. It should still be okay around a 12.0 with low boost and that will save on fuel economy. It shouldn't need more fuel until your past 4-5psi where it can be down in the low 11's for a safe spot.

[JonathanLeskewich]

Ok thanks for that. I guess I will have to stay at 3 psi this year until I can get bigger injectors put in. I will adjust thE BE and PE to around 12 and up the timing.

What about the MIL for the MAF? Do I need that on still? It doesn’t work for me since it just codes out and I can’t drive.

[5FDP]

I've never done a workhorse chassis so I haven't had that issue with failing the MAF sensor. If I have the MAF fail high at 0hz and the dtc's set to first error it always went into speed density with no loss of throttle control on trucks.

New injectors aren't that expensive I would just do them now. That VE table just isn't right and to me I wouldn't keep driving it like that. It's already out of injector at 2-3psi in the upper rpm and I don't like to play with it like that. Timing and fueling are what make for high EGT's, if you fix them both you'll be able to bring them down.

[JonathanLeskewich]

Ok so I am actually not in speed density is what you are saying correct? That sucks... I will have to figure out a different way to lock out the MAF then.

[5FDP]

I can't tell from the log is all I can say. The code P0103 is not present because you have it set to no error reported. Maybe you will have to try no MIL light or something to see if it doesn't freak out. Or just unplug the MAF if the IAT sensor is not built into it.

[JonathanLeskewich]

Thanks, this is all super helpful. One last question. Any suggestions on injectors? I already have a new fuel pump I’m putting in.

Jonathan

[5FDP]

A popular choice are stock injectors from a later model truck. The 6.0 flex fuel trucks/vans ran 50lb/hr injectors and the flex fuel 6.2's ran 52lb/hr injectors. I don't have the part numbers on me.

They are GEN 4 injectors but we can still convert the injector data over into the GEN 3 computer with a spreadsheet. Input the data from the tune and it will spit it out in the GEN 3 style.

[JonathanLeskewich]

Thanks so much. Will do! I have spent a lot on the project and the motorhome. Some injectors are not a big deal.

Cheers,

Jonathan

A popular choice are stock injectors from a later model truck. The 6.0 flex fuel trucks/vans ran 50lb/hr injectors and the flex fuel 6.2's ran 52lb/hr injectors. I don't have the part numbers on me.

They are GEN 4 injectors but we can still convert the injector data over into the GEN 3 computer with a spreadsheet. Input the data from the tune and it will spit it out in the GEN 3 style.

[blindsquirrel]

12613412. They are pretty short, you will probably need injector spacers.

Here is a Gen4 tune file with that injector data:
2010 Yukon 6.0 L96 E38 T43 1GKZKREG0AR189018 - 12613412.hpt

[JonathanLeskewich]

Thanks! These are super cheap as well!

Do you know the spacer number too? Or maybe someone else has done this before?

Jonathan

12613412. They are pretty short, you will probably need injector spacers.

Here is a Gen4 tune file with that injector data:
2010 Yukon 6.0 L96 E38 T43 1GKZKREG0AR189018 - 12613412.hpt

[blindsquirrel]

Sometimes there is already a spacer between the rail mounts & manifold, simply removing the spacers drops the rail down about the same amount as the difference in injector heights. I don't know the 8.1L intake setup well enough to know for sure.

Here's a handy chart for injector interchange stuff:
innjector dimensions.jpg

[JonathanLeskewich]

FYI Here is what I bought for injectors. They are the right length (There are three different lengths to choose) and bit more room in the flow than the 6.0 ones. I spoke to FIC and they had a ton of knowledge on this.

They have better atomization and they are flow matched for this price. Will be easier to control fuel as well since they have newer tech pulse width control internally compared to the Delphi's.

Thanks again for all the help on this guys! Hopefully the below helps someone trying to do something similar on an 8.1.

https://fuelinjectorconnection.com/p...high-impedance (Could have got the 60 lb ones as well, but then idle quality gets a bit iffy...)

Adapt My Injector To
EV to Mini Delphi (99-07 Truck)
8 $52.00
FIC BOSCH 52 LB 550 CC for LS - Fuel Injector Connection8
FIC BOSCH 52 LB 550 CC for LS
Adapt My Injector To: EV6 to Mini Delphi (99-07 Truck)
Year/Make/Model: 2006 workhorse motorhome, 8.1 twin turbo
8 $424.80

Sometimes there is already a spacer between the rail mounts & manifold, simply removing the spacers drops the rail down about the same amount as the difference in injector heights. I don't know the 8.1L intake setup well enough to know for sure.

Here's a handy chart for injector interchange stuff:
innjector dimensions.jpg