Trying to figure this out (VE table differences)

[guardsman01]

Figure this one out......99 Camaro, 00 Impala, both have the 3.8 V6.

The only differences between the engines are the design of the intake and exhaust manifolds. Other than that, they use the same throttle body, MAF sesnor, heads, bottom end, ignition system, etc......

I was comparing the VE tables....I expected that maybe there would be a bit of difference, but holy crap.....(I can't figure out how to copy the tables to here).....

Anyhow, as an example, the Camaro VE at 20Kpa MAP and 0-6400rpm is
31,34,46,50,54,55,57,59,60,60,58,56,53,50,42,36,29

The Impala VE at 20Kpa MAP and 0-6400rpm is
65,48,44,44,44,44,44,44,43,43,42,42,42,42,42,42,42

The PE enrichment Add vs RPM is also significantly different, as are the timing tables.....

Could the different intake and exhaust systems cause this much of a variance in the VE tables on the same engine?

Same question on the timing and PE fueling requirements. Thanks.

[Monodax]

It "might" be possible for them to be that different but most likely they use a different formula to derive @ the VE values listed in the VE table. I would check with Keith or Ken as they know the VCM code that interprets these values.

[AnotherUser]

As the vehicles are updated, so are the VE tables. Cam makes a big difference, and I am sure that they all use different cams. Intake and exhaust also play a really big factor. The other key thing to remember is that the VE tables are not intended as a primary fueling table. They are intended as a backup in the event of a critical failure, or for when the MAF is not accurate. As such, I would expect that the VE table be particularly on the "rich" side...just in case.

[guardsman01]

Another user, they used the same cam on these engines, apparently regardless of the application.....That's one of the things that irked me about the V6 Camaros......we got the same granny cam as the Buick Le Sabre's, etc. >

Anyhow, I would expect a bit of difference, but this is a huge difference, and not only in the VE tables, the timing is completely different, even the injectors tables are different (same size injectors, but the Camaro table is non-linear while the impala one is linear).

It's like looking ata completely different engine.

The intake manifold is similar to the LS1 intake, and the exhaust is just set-up for a cross-mounted motor. I can't see those two things resulting in that much of a difference across the board, though.

Hmmm....it only makes tuning that much more difficult, because it now makes it look like relatively small changes in the intake and/or exhaust will create wide variances in how the engine reacts....basically, a very sensitive engine ......

[AnotherUser]

The only other thing I can tell you is that a large amount of the time the stuff GM does defies logic. Keep that in mind. They "design" in plenty of problems to keep from retooling facilities, or to make multiple different models, basically anything to keep costs down. So there could be major differences in those exhaust manifolds, and there is probably a lot of difference in the intake manifolds. Are they both plastic?

[guardsman01]

The Camaro/Firebird intake is a two-piece aluminum, and it's actually similar in design to the LT-1 intake....large upper body, and then straight intake runners underneath that are open directly to the main plenum.

The Impala/Grand Prix/Les Sabre, etc. also uses a two-piece, but the upper piece is a composite intake that is the same general design as the LS1 intake, with a main plenum with the runners going over top of it, and the the lower piece just has the last bit of the runners going to the intake ports on the heads.

That just got me thinking, too....our engines having the intake ports on the heads with a straight shot back into the main plenum, and the FWD engines having more runner, would make a bigger difference there than would be readily apparent......effects of any blowback from the cylinder, harmonics, etc., would be entirely different.

I see what you mean, now, about them re-configuring the engine......easier and cheaper to screw the software all to hell, than to have to re-tool the engine assembly lines......

Basically, though, that means that, for the V6 Camaros and Firebirds, we're on our own in terms of working with owners of other body style/same engine combinations.

The closest I think that we would get in terms of physical engine set-up would be the LT-1 F-Bodies. The biggest physical difference there (other than displacement) would be the compression ratio.....

Thanks for the ideas on this.....it's got me thinking now. I'll have to start looking more into the technical side, and work on it from there.

Thanks. John