Gary Z

I have recently started basic PE tuning of my stock 2002 Z28. I have HP Tuners software and an LM-1 Air/Fuel meter. My measured AFR very closely follows the commanded AFR at WOT which exactly follows my High Octane PE table. I was surprised that the stock LS1 PE table is as rich as it is since most tuners recommend 12.5:1 or so for max power. I decided to compare the LS1 PE table to the LS6 PE table. I created the attached comparison chart using stock LS1 and LS6 Power Enrichment Tables. The chart shows PE entries converted to Air/Fuel. The LS6 table baffles me. I would appreciate any opinions or explanations of why these tables are as they are and why they differ so.

-Gary

Gary Z

There are other significant differences, such as ignition timing tables, between the LS1 and LS6. I view the LS6 as a slightly better breathing LS1. I want to understand how relatively minor hardware differences relate to seemingly major tuning differences. GM engineers obviously put a lot of time and effort into tuning the LS6. They didn’t just “tweak” the LS1 tune. I think the stock PE tables might be good clues about the nature of combustion in these engines. Or is that a dumb idea?

-Gary

Gary Z

I think I can more clearly state my idea as follows: Tuning an engine is an optimization process. At GM this process is probably highly automated and very effective. We have in the LS1 and LS6 two reference points. My question is: Given these reference points, what can we learn by extrapolation that we can apply to tuning our personal LSN? I think the two stock PE tables can tell us something.

-Gary

jimmyblue

iTrader: (11)

I believe the difference lies in the demographic.

The Z06 (LS6) was top-of-the-line, narrow performance
enthusiast market where max HP was more important than
the occasional pinging problem and the drivers are made
of money and will pay to tweak it up.

The LS1 was mass-market, you get a few tens of thousands
of these coming in for warranty beefs on account of pinging
under load, you're screwed (if you're GM).

That, and if the LS1 made the same numbers as the LS6 then
corporate Hell would freeze over. So da Man be holding us down.

The LS6 profile is more like what I'd expect for a performance
tune, I think the declining commanded AFR at higher RPM is
probably covering fuel fade (I have seen other places, the
idea that you want fatter at midband (for torque) and lean
it out a bit - relatively speaking - up top for HP. You need a
faster burn rate at high RPM to get it all done in the power
stroke, and your spark set to put in the right place.

The 'vettes also have that funny air bridge deal that biases
airflow centrifugally and this probably accounts for some air
flow side differences, that and the lack of screen on the MAF.

Gary Z

Jimmy’s posts are always informative but I was slow to appreciate this one. Following his lead I eventually discovered that F-Body LS1 tuning is very different than Corvette LS1 tuning – stock F-Bodies appear to be detuned! I assume many others are aware of this but I had not previously found specifics. I found that the LS1 Corvette PE Table more closely resembles my understanding of how a performance tune should look. I have attached another graph showing the differences. F-Body and Corvette tuning differences are extensive – ignition advance tables and the main VE tables differ. I had been slowly modifying my Camaro’s stock tune but I now plan to assemble something close to the stock Corvette tune and start over. Thanks, Jimmy.

-Gary

Another_User

F-body cars detuned? LOL. Of course...there is no way GM would want these things cutting in on Corvette territory. That is why our doors are so heavy and sound like coffin lids when they close. The heavier they made the F-body, the better.

luv2spd

iTrader: (1)

LOL. That's a great description of the doors!

Third Gear

iTrader: (3)

As far as the Spark Table goes... the LS6 has a pretty conservative table. Again for obvious reasons, but hey if you want to compare things, that has considerable differences than a stock LS1 Spark Table.

Viper

iTrader: (6)

But the LS6 heads are more effecient, thus the different LS1 spark table no?

Another_User

Not really. On a lot of years the spark is more aggressive on the LS6, but with the higher compression it would not need to be. Unless the F-body was detuned, which we all know it is.

SmokingWS6

iTrader: (1)

JimmyBlue,

after looking at the ybody and fbody pe table, its obvous the Vette has the better tune. However I thought more fuel helped torque down low and leaner at high rpm's helped it combust faster. Would a 180 of the vette graph be a good starting point for a tune? say start at 11.5 and work up from there? I know many factors would be affected. I'd probably have to pull a degree or two of timing up high with a leaner condition.

Predator

If that was the case, why would they use lighter plastic material for the door panels?

John_D.

iTrader: (2)

Leaner, on a catted car, gets into catalytic converter overheating. They have to keep the cats alive for the feds... Us on the other hand, that's a different story.

No, GM wouldn't make a car heavier to de-tune it.... They struggle enough with CAFE and mpg ratings as it is, without making the car intentionally heavier... Now turning the PE and timing down, that's very likely.

Another_User

I have absolutely no idea. But tell me those doors are not heavy as heck. I don't think I have ever seen another car (70s vehicles excluded) with a door as heavy as you see on an F-body. They are just as bad as the 80s, early 90s. They had that coffin-lid sound too. I am just saying that GM was by no means going to go out of their way to make the F-body more weight-efficient like they did with the Corvette. I suppose it may not have been a blatant attempt to make the car heavy, but they definitely did not try to make it light.

Predator

Good point AU.

My reasoning, about the doors, is that the car is a 2-door coupe, with a back seat (unlike the Vette), which necessitates longer doors. If GM wasn't weight conscious at all, they probably would have slapped sheet metal on there.

I wasn't aware of the better LS6 factory tuning (before reading this thread); It's pretty interesting to consider. I agree with you guys that GM was just trying to cover their ***. I believe that they think of Corvette owners as true enthusiasts, and the f-body guys and gals fit all categories from secretaries, to pimply-faced first-time car buyers, to enthusiasts--a nice safe tune for the masses.

Predator

BTW Gary, that LS6 tune looks like it's on the safe side too: it could be leaned-out a little. It seems that GM is playing it safe with the Vette too, and WAY safe with the f-body.

tici

iTrader: (1)

Here some more AF curves (98 - 02), F and Y bodies.
Also what Hypertech does for the 98 F fody.

...looks like a jungle!

Another_User

That is very interesting data.