One big difference is that the factory EFI‘s using the reluctor where is the aftermarket does not. If you scroll back a page or two blue85 was talking about referencing that reflector when you first plug in a new computer would be something similar to how the aftermarket EFI makes you reference the timing.
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
Replaying to Scott:
I doubt anyone would fault you for that. I'm guilty of ignorance all the time. The timing is based off of a Cylinder Airmass vs rpm table and is adjusted via the ecm. The idea here is that you can adjust timing for maximum brake torque throughout the entire rpm vs cylinder fill range. High load and low rpm, vs low load and high rpm and everything in between. It can offer maximum efficiency throughout the entire operating range. You're system will most likely be similar but with an initial base timing from the distributor.
Spark tuning is a bitch as what's really need is a Load Bearing Dyno. Its about the only way to do it correctly. It can also make tuning your air model super easy.
I doubt anyone would fault you for that. I'm guilty of ignorance all the time. The timing is based off of a Cylinder Airmass vs rpm table and is adjusted via the ecm. The idea here is that you can adjust timing for maximum brake torque throughout the entire rpm vs cylinder fill range. High load and low rpm, vs low load and high rpm and everything in between. It can offer maximum efficiency throughout the entire operating range. You're system will most likely be similar but with an initial base timing from the distributor.
Spark tuning is a bitch as what's really need is a Load Bearing Dyno. Its about the only way to do it correctly. It can also make tuning your air model super easy.
Screenshot logs aren't always the best. And Mark is way older than I am, even if his statement is true.
With that said I like some TM. On my rig I use transmission torque management as well as abuse mode. Slamming reverse during a climb or limiting power during front and rear digs was something I wanted. You don't have that option but that's ok.
I'm glad to see the fuel pressure corrected. So when you pull the vacuum its right at spec correct?
I won't touch a tune where the vehicle has any fuel, air, or spark mechanical issue. You're just chasing your tail and there's a good possibility when it gets fixed you made shit worse.
Two more question: Firstly don't worry about Howell. Leave them alone for now. The whole cooler heads will prevail thing. Have you looked and found that was stock GM TM tables in that tune? This could be a clue.
Second: I didn't read much so I don't know this whole backstory. Per our PM, have you checked the injector part numbers that are in the engine. if so what are those?
Those are the first questions that need answered.
Fuel pressure increased another 9-10 psi with the vacuum source removed.
I'm not calling Howell until next week or maybe later.
I really want to see Larry's file and compare it against mine. It's been well tested for the last 15+ years....
and the injectors haven't been touched or even removed. That's one of the few parts on this engine I haven't touched.
The torque values come from airflow? MAF? If so, that brings up the earlier concern about MAF placement on the intake piping. I've used two different MAF's so I don't believe it's a sensor failure.
Add to that injector opening and closing times
Dang I go to sleep and this thread blows up.i brought my laptop to work, anything you want me to look at skunk?
Nevermind, I see it now.
Engine Torque calculations are based on the Airflow model. Maf placement in custom intake ducting, Intake manifold changes, cylinder head changes, cams, exhaust, etc... all change the airflow model.
So you've got the fuel pressure thing sorted out and it is now in spec. If you feel comfortable moving forward, I.E. the MAF is functional and showing good baro, O2's are good and are in good placement in the exhaust stream, plugs are good, etc then we can move forward.
I'm not an 8.1 guy but it really doesn't matter.
-First step is always verifying cylinder volume in the tune. Lets do that. So verify that's correct in the tune. Engine>general. (there's more first steps but its gen III to gen III)
-After that we need to verify injector data. I do not have an excel spreadsheet for the 8.1l injector flow data, but that should be in a stock tune we can download from the repository on HPtuners website. (https://www.hptuners.com/my-account/tunerepository/) You will need an account. Find one closest to the year of your engine and as stock as possible.
Here is where I need 8.1l guys help. Were there multiple injector mfgs used on this engine? We need to know that. If there were we need to know whats in it. This is important.
This is all just diagnostic stuff. It all has to be correct or we are chasing our tail. If it runs good enough for you now and that's all you want then cool, we can skip all this.
So you've got the fuel pressure thing sorted out and it is now in spec. If you feel comfortable moving forward, I.E. the MAF is functional and showing good baro, O2's are good and are in good placement in the exhaust stream, plugs are good, etc then we can move forward.
I'm not an 8.1 guy but it really doesn't matter.
-First step is always verifying cylinder volume in the tune. Lets do that. So verify that's correct in the tune. Engine>general. (there's more first steps but its gen III to gen III)
-After that we need to verify injector data. I do not have an excel spreadsheet for the 8.1l injector flow data, but that should be in a stock tune we can download from the repository on HPtuners website. (https://www.hptuners.com/my-account/tunerepository/) You will need an account. Find one closest to the year of your engine and as stock as possible.
Here is where I need 8.1l guys help. Were there multiple injector mfgs used on this engine? We need to know that. If there were we need to know whats in it. This is important.
This is all just diagnostic stuff. It all has to be correct or we are chasing our tail. If it runs good enough for you now and that's all you want then cool, we can skip all this.
I used to think I was pretty tech saavy, but after reading through all of this I'm not so sure anymore. 
I used to think I was pretty tech saavy, but after reading through all of this I'm not so sure anymore.
The theory is all the same. That's the most important thing to remember. Its still just an air pump.
Speaking of torque management, most of those options are off the table since there are no sensors or solenoids in the transmission, no shift control and manual throttle. You can't baby 1st gear because you don't know which gear it's in. You can't do traction control because there's no wheel speeds.
Just a little help with his injectors, My 8.1 had Delphi 25343789 that spec at 26lbs per hr at 43psi but he should check his part # just to be sure.
At what psi ?
My engine was out of a 2009 4500 Kodiak so who knows, lol
The first problem is that there are no timing marks. Basically, the reluctor wheel is attached in a specific orientation to the crank and the sensor is in a known location, so the crank position is known exactly. The CASE learn is a fine-tune kind of thing looking at the small errors coming from that specific assembly. Even my old 3800s had no timing marks, just teeth attached to the harmonic balancer.
You can't use an 8.1L base file without electronic throttle control. Apparently, that is part of the 8.1L segment you would need to swap in. As for running a compare between the two files and looking at all of the normal settings...that would be value-added and is some of what we've been doing in this thread.
I’m glad major progress got made today.
I’m actually really surprised the tune is so far off. Don’t get me wrong the technical discussion has been very enlightening.
What’s even crazier with all the talk of injector flow rates, air flow models and such is that mine is literally copy/paste of Larry’s setup. I don’t know what part number the injectors are. The maf is in a decent spot but probably not perfect but it’s where it can fit. It just worked from the first time we started it. I’ve put enough miles on the first engine to not question the tune at all. I’ve run it at high elevation, stupid hot temps and freezing cold. It’s been as close to oem consistency as I can expect. It just makes the issues on this truck all the more odd.
I’m really curious what’s different between Larry’s tune and this one.
I’m actually really surprised the tune is so far off. Don’t get me wrong the technical discussion has been very enlightening.
What’s even crazier with all the talk of injector flow rates, air flow models and such is that mine is literally copy/paste of Larry’s setup. I don’t know what part number the injectors are. The maf is in a decent spot but probably not perfect but it’s where it can fit. It just worked from the first time we started it. I’ve put enough miles on the first engine to not question the tune at all. I’ve run it at high elevation, stupid hot temps and freezing cold. It’s been as close to oem consistency as I can expect. It just makes the issues on this truck all the more odd.
I’m really curious what’s different between Larry’s tune and this one.
Was it posted what OS and base vehicle was in here?
Doesn't the 8.1 have a different firing order from LS's?
Will these run if the firing order is off?
Doesn't the 8.1 have a different firing order from LS's?
Will these run if the firing order is off?
They are the same.
LS numbers usually reference 4 bar (58psi). They used to mostly be rated at 3 bar, which is probably what you mean (43.5psi), in which case we're both talking about the same size injector.
I’m just getting home and beginning to recover from 3 days of wheeling. I was planning on leaving Wednesday morning however my buddies decided to surprise me with a Tuesday “hey get your shit together, we’re on our way”
I caught up to them outside of Truckee somewhere and we made it to meadow lake around 11pm where the rest of the crew had a campsite setup for Sierra Trek.
We ran from meadow down to WH1 and back on Wednesday and the truck performed well overall.
The new Kevlar bushings from ORD are far superior to anything I’ve ran before.
The PSC assist is acting up again with the slow/restricted response to steering input, very similar to the problems I had previously. Mostly when it’s cold but it’s less than ideal at speed on fire trails.
The tune is still off or some other issues are causing a no start issue and rich conditions at times. The no start problem is resolved with throttle input however I experienced a backfire a couple times. Scared the shit out of people more than once. I noticed the CEL light is illuminated for the first time yesterday heading back to camp however I haven’t had a chance to look at it. Even with these problems, the truck is a blast on fire trails now with excellent throttle response and torque to propel the fat pig.
Below are a couple pics from the trail and one from our lakeside campsite at meadow lake. I’ll have more later after the guys setup a photo share.
And the new fender is smashed again from WH1 and I hit the A pillar against a rock.
8600’ lookout. This was a new trail we found with epic views.
I caught up to them outside of Truckee somewhere and we made it to meadow lake around 11pm where the rest of the crew had a campsite setup for Sierra Trek.
We ran from meadow down to WH1 and back on Wednesday and the truck performed well overall.
The new Kevlar bushings from ORD are far superior to anything I’ve ran before.
The PSC assist is acting up again with the slow/restricted response to steering input, very similar to the problems I had previously. Mostly when it’s cold but it’s less than ideal at speed on fire trails.
The tune is still off or some other issues are causing a no start issue and rich conditions at times. The no start problem is resolved with throttle input however I experienced a backfire a couple times. Scared the shit out of people more than once. I noticed the CEL light is illuminated for the first time yesterday heading back to camp however I haven’t had a chance to look at it. Even with these problems, the truck is a blast on fire trails now with excellent throttle response and torque to propel the fat pig.
Below are a couple pics from the trail and one from our lakeside campsite at meadow lake. I’ll have more later after the guys setup a photo share.
And the new fender is smashed again from WH1 and I hit the A pillar against a rock.
8600’ lookout. This was a new trail we found with epic views.
Is it time for exo-cage to protect the fender?
Or maybe follow the lead of Scott and others and narrow the front.
Or maybe follow the lead of Scott and others and narrow the front.
