Confused about tuning? Never knew a car like the GN

[cjmatt]

So let me get this straight, the GN doesnt use the MAP sensor for ECM Calibration? I read that it only is made to operate the gauge and that the PCM functions mainly on MAF only. So what happens when the maf maxes out? I see some people run the extender and some dont, Is there a limit when you have to run an extender chip? The other thing thats confusing me is how people tune from EGT and fuel pressure regulator settings....Maybe i'm new school or something, but every FI car ive owned, I have adjusted maf tables and VE tables in order to get the air/fuel zeroed in on a wideband. I also see alot of people shooting to get the a/f locked in with the 02 sensor. what is the point in logging that as nobody in there right mind is going to shoor for a narrow band 14.7 a/f when running boosted. Ive always been an 11.9-12.2 guy myself.

My first plan of attack is to get a fuel pump hotwire and pump, and a chip(TurboTweak?), as well as turning the boost up a hair from the adjustable wastegate mod. Any other reccomendations other than to get a scanmaster? There arent any free dataloggers? Ive got a laptop with obd1 cable i use to tune my trans am, Im guessing this wont work

Thanks in advance for the newb help

 

[Blazer406]

You are correct... the GN doesn't use the MAP for anything related to the ECM and fueling.

The computer does have code... that at a certain throttle opening (near WOT) it will go to the preset data stored in the fuel tables...... regardless of what the MAF sees.

The extender chips can read more CFM than the stock type chips. Is it necessary? Not IMHO .... because at WOT... it tunes off the tables.... not the MAF anyway. It would be fairly rare to experience 255 gm/sec that you weren't WOT anyway....

TurboTweak is the chip to get.... he gives some tunable features like fueling and timing adjustments that can be made using a scantool. You don't need to mess with the fuel pressure.

Since you haven't got anything yet... I recommend reading alot.... setting a reasonable goal... and looking at people running as fast as you want to be... and listening to them.

These cars can go low 12's with only a few mods... with traction....on a decent boost.

With the right mods... you can go low 10's on pump gas and alky... there are several board members already there..... your pocketbook is the limit...

HTH

 

[cjmatt]

thanks for the quick reply, as far as what my goal is, id like to get the car in the consistent upper 11s/low 12s yet still drivable...gotta love turbos. Ive got a 94 Trans Am thats got the power for mid 9s if itd ever hook and the streetability of it is less than desirable, hence why im now tooling around in the GN. Right now its pretty much stock except for a K&N filter and a removed cat/rusty exhaust. cant wait to get it dialed in a bit and start cutting some wicked 60's

BTW, were those times in your sig off of the old parts setup, or the new stuff?

 

[Vendor Defendor]

better be on his old combo.. that new stuff should put him in the 10s

 

[TurboDave]

You are correct... the GN doesn't use the MAP for anything related to the ECM and fueling.

The computer does have code... that at a certain throttle opening (near WOT) it will go to the preset data stored in the fuel tables...... regardless of what the MAF sees.

The extender chips can read more CFM than the stock type chips. Is it necessary? Not IMHO .... because at WOT... it tunes off the tables.... not the MAF anyway. It would be fairly rare to experience 255 gm/sec that you weren't WOT anyway....


HTH

Please don't mis interpret my question but, after a little over 15 years of burning chips for these cars, maybe you can help me out. I'm wondering where these "fuel tables" are that you refer to that take over after the maf tops out at 255. Maybe I missed something.
Other than the maf tables (which of course are useless after 255) the only other "table" that can affect fueling is the PE table, and it certainly doesn't have any dynamic ability beyond what's pre programmed and aren't very helpfull unless you manipulate fuel pressure (old school method of tuning) which isn't very condusive to both street and race.

You've got to get the maf to be able to meter beyond 255 in order to make a boost change and expect the fuel delivery to faithfully follow it.

Your assumption that "it tunes off the tables at WOT and not the MAF" are totally wrong particularly when the maf is still able to measure airflow.

But hey, maybe I missed something, I'm getting old and forget things. Clue me in.

 

[cjmatt]

on the lt1 maf, there is a table called percentage change to PE, whic you have to add fuel to in order to control fuel after you max the maf, im guessing the GN has it too.

Is there a list of what tables are in the PCM? I was wondering about that tonight when I was tolling around town as I was wndering how the pcm controlled the difference between different rpms and throttle conditions with varying boost levels

 

[Daniel Jost]

I think when he said PE he means power enrichment.
,dan

 

[TurboBob]

on the lt1 maf, there is a table called percentage change to PE, whic you have to add fuel to in order to control fuel after you max the maf, im guessing the GN has it too.

Is there a list of what tables are in the PCM? I was wondering about that tonight when I was tolling around town as I was wndering how the pcm controlled the difference between different rpms and throttle conditions with varying boost levels

There is a PE AF Ratio mod vs RPM. This is where most guys throw extra fuel when the MAF maxes out (255 grams/sec). The more modern chips are more sophisticated than that.

The TurboTweak stuff has adjustable factors so you can tune the settings in without burning a ton of chips.

The Extender stuff uses a MAF (LT1/LS1/etc.) with higher range, and extends the MAF range to 512 or 768 grams/sec. This way, if you turn the boost up, the fueling increases to match.

Bob

 

[Blazer406]

BTW, were those times in your sig off of the old parts setup, or the new stuff?

My times were with stock unopened motor and stock turbo. Mods were basically bolt-ons.......alky, TT chip. 60lb injectors, dutt necked stock location intercooler, translator and LS1 MAF meter, 3-1/2" Big Mouth cold air kit, 3" TH DP, Hooker cat back with a test pipe in place of the stock cat, Comp 980 valve springs.... that is about it.... oh... I had my converter.... which was too loose for the stock turbo (I had bought it for my future combo at the time).... 9-1/2" Vigilante 5-disk lock-up..... 3200-3400 stall (aka 0-pump). I also had 275/50 MT Drag Radials....

That combo should have gone into the 11's had I stuck to it... but only one track trip with the alky netted 12.65 with 32 psi in the tires.... would have 60' better probably if I could have let some air out..... they were rubbing my fender lips... and I was scared if I let any air out... they would bulge out more... and really cut the tires....

Boost was around 22 psi..... on pump gas and alky.

A TE44 would have put down 11's easy with my old parts... just change turbo....

 

[Blazer406]

Please don't mis interpret my question but, after a little over 15 years of burning chips for these cars, maybe you can help me out. I'm wondering where these "fuel tables" are that you refer to that take over after the maf tops out at 255. Maybe I missed something.
Other than the maf tables (which of course are useless after 255) the only other "table" that can affect fueling is the PE table, and it certainly doesn't have any dynamic ability beyond what's pre programmed and aren't very helpfull unless you manipulate fuel pressure (old school method of tuning) which isn't very condusive to both street and race.

You've got to get the maf to be able to meter beyond 255 in order to make a boost change and expect the fuel delivery to faithfully follow it.

Your assumption that "it tunes off the tables at WOT and not the MAF" are totally wrong particularly when the maf is still able to measure airflow.

But hey, maybe I missed something, I'm getting old and forget things. Clue me in.

I maybe had a bad chioce of words.... What I intended was to imply that the ECM didn't rely on the MAF readings to make WOT fuel adjustments....that is a function of how the chip was programmed....

As far as I know... there is no dynamic real time fueling adjustments that are being made at WOT....

edit... I didn't realize the extender chips were adding more fuel at WOT if the MAF was still reading.... sorry...evidently I missed that....

Also.. the old school "turn up the fuel pressure" IMHO is a bad idea... because you are typically trying to give it more fuel at WOT under boost.... which it will do...... but what it also does.... is make it have more fuel everywhere else... which in nearly all cases.... not likely what you want.... part throttle may be just fine.... but when you jack up the FP... it puts the extra fuel everywhere....

Am I off my rocker?

FWIW.... O2 corrections via AFR target off a wideband is what I am after..... there is some people toying with this with the stock ECM...

Maybe I am getting too far off topic... sorry.

 

[TurboDave]

I maybe had a bad chioce of words.... What I intended was to imply that the ECM didn't rely on the MAF readings to make WOT fuel adjustments....that is a function of how the chip was programmed....

Well actually, as long as the maf is reading (not maxed) it will be a mojor player in fuel deliver and doesn't care whether it's cruise or wot. The only thing that quits at WOT is BLM learning. If (as in an extender extreme) the maf is able to measure all the way up to 768 gpm of airflow, it's going to be controlling fuel no matter the conditions.

As far as I know... there is no dynamic real time fueling adjustments that are being made at WOT....

MAF (it it isn't topped out)

edit... I didn't realize the extender chips were adding more fuel at WOT if the MAF was still reading.... sorry...evidently I missed that....

Yup

Also.. the old school "turn up the fuel pressure" IMHO is a bad idea... because you are typically trying to give it more fuel at WOT under boost.... which it will do...... but what it also does.... is make it have more fuel everywhere else... which in nearly all cases.... not likely what you want.... part throttle may be just fine.... but when you jack up the FP... it puts the extra fuel everywhere....

We certainly agree on that point.

Am I off my rocker?

FWIW.... O2 corrections via AFR target off a wideband is what I am after..... there is some people toying with this with the stock ECM...

Maybe I am getting too far off topic... sorry.