Tuning for Low Compression

[5_Liter_Eater]

My new motor is 9.6:1. Anyone have tips for low compression tuning, I guess I'm thinking they would like more timing pretty much across the board. Open to any input.

[5_Liter_Eater]

For that matter, any tips on tuning when increasing displacement. I am just not happy with the way my car is running so I'm grasping at straws here.

[DSteck]

Throw ALL the timing at it!

[5_Liter_Eater]

Can you be more specific Dave? :P

[DSteck]

ME be more specific?

"My car runs poor. How do I fix it?"

No tune, no log, no service.

First rule of [HP Tuners] fight club:
Post the file

[5_Liter_Eater]

Touche'

The tune is up there in post #2 now.

[DSteck]

There's your problem. It's an E40.

[Pekka_Perkeles]

I think in E40 Cylinder Volume is relevant. Change it to reflect your new cylinder size. I guess you have scaled tune, though, based on injector values, but anyway.

And please, make your VE tables smooth! Your Boost VE in 3D is incredible...

[5_Liter_Eater]

There's your problem. It's an E40.

Thanks Captain Obvious.

I'm getting ready to throw it out and go Pro EFI. If only I weren't so cheap.

[DSteck]

I think in E40 Cylinder Volume is relevant.

It's not.




The E40 works just fine. I'm just giving you trouble. I can't see the file, but I'll look when I get home.

[5_Liter_Eater]

I think in E40 Cylinder Volume is relevant. Change it to reflect your new cylinder size. I guess you have scaled tune, though, based on injector values, but anyway.

And please, make your VE tables smooth! Your Boost VE in 3D is incredible...

I believe cylinder volume is irrelevant but I'm not opposed to changing it to reflect actual volume. I did have it that way but I made a bunch of changes back to stock to try and line out my idle problems and that was one of them.

VE could definitely use some smoothing but I think the boost VE looks worse because there is only a difference of ~500 units between the lowest and highest. Still I admit, it's ugly. But the problems are out of boost.

Things I'm trying to address with this thread:

It's lazy until it gets into boost and this is new behavior with the new motor and slightly bigger turbos. Every time I shift it falls out of boost. Didn't used to do that. It's not crisp at all, for a ~big cam 408 I would expect a lot more of a torque'y feeling out of boost. This is the primary reason for the thread, to get it snappier out of boost.

Idle airflow doesn't jive with actual. IE: I have to jack up the idle airflow to get it to idle, almost double the values I'm seeing for dynamic airflow at idle. I "think" this has to do with the fact that the tune is 50% scaled for the injectors. Some tables have been un-scaled recently to try and get it to idle.

I have to pedal the fuck out of it to get it to start. So sorta in line with the above, the idle airflow numbers are whacky so I don't know what to do with the startup airflow table to get it to start without pedaling.

[5_Liter_Eater]

It's not.




The E40 works just fine. I'm just giving you trouble. I can't see the file, but I'll look when I get home.

Thanks Dave,

I'll post a log when I get home too. I realize I'm beeing like Ned Flanders' beatnick parents here; "You gotta help us doc, we've tried nothin' and we're all out of ideas".

[SultanHassanMasTuning]

I like the E40 (besides the IFR tables and other fuel parameters)

lower compression you can add more boost and timing. basically your knock threshold now gives you more room.

[Pekka_Perkeles]

I believe cylinder volume is irrelevant but I'm not opposed to changing it to reflect actual volume. I did have it that way but I made a bunch of changes back to stock to try and line out my idle problems and that was one of them.

Sorry, my mistake. It is indeed irrelevant, just as Dave said.

[Pekka_Perkeles]

VE could definitely use some smoothing but I think the boost VE looks worse because there is only a difference of ~500 units between the lowest and highest. Still I admit, it's ugly. But the problems are out of boost.

Things I'm trying to address with this thread:

It's lazy until it gets into boost and this is new behavior with the new motor and slightly bigger turbos. Every time I shift it falls out of boost. Didn't used to do that. It's not crisp at all, for a ~big cam 408 I would expect a lot more of a torque'y feeling out of boost. This is the primary reason for the thread, to get it snappier out of boost.

You have two VE's and they should match at 105 kPa. Now they do not and there are some huge differences.

Furthermore, I don't think the primary VE shape is ok in all areas. It may be one source of your lag after shifting (as well as timing). Without logs, well, you know... I'll let Dave to continue, as I'm not really an expert with E40 since I've tuned just a single Vette with E40.

[MikeOD]

You need to throw way moahh spahk at it guy!!!

All kidding aside, The tune is scaled right? That said, changing the ETC area scalar might help you bring the idle airflow numbers inline with actual...that number is used in the calculation to determine how much throttle angle equates to how much airflow for the given RPM ranges. After that, you may find you no longer need to pedal it to get it to start, but if it still needs some help, adjust the startup airflow table...and use Marcin's spreadsheet to build a cranking VE table from your VE after you're tuned.

[carlrx7]

-6an line from nitrous bottle to intake, no jet, crack open bottle prior to engine start. leave full open to fix laggy boost.

[5_Liter_Eater]

Mike, I never thought to scale the ETC scalar. That could be playing a big part in the idle issues. I doubt it's as easy as cutting it in half like the rest of the tune though.

I haven't come across Marcin's cranking VE spreadsheet. I'll look for it.

[5_Liter_Eater]

Edit: Marcin's spreadsheet doesn't work for the 4th gens (at least not the E40). The E40's cranking VE table is a percentage of ideal cylinder volume and the GMVE values from the VE table are borked. I guess if I knew how I could convert the GMVE to regular VE numbers which would work. Stock E40 cranking VE is all 100%'s.

[DSteck]

Don't scale idle stuff. Don't worry about making it match dynamic airflow either. It has zero correlation.