'91 LB9 A4 rating accurate?
 

I have a friend that suggested his 91 LB9 Z28 A4 has 230 hp instead of the 205 that is stated in the tech data area of the site. Does anyone know if these Auto ratings are accurate or not?

Just curious, couldn't find anything through searching...

yeah the speed density cars usually make more hp. Thats also with a m/t

How about your 'friend' showing supporting documentation instead of the other way around. The burdon of proof should be on him or her.

well he said his auto has the L98 cam in it from the factory, which I wasn't aware of. Why would the bhp ratings be different if they auto and manual both had L98 cams? His info mixed up or is mine?

there is no difference if auto or 5sp if they both came with l98 cam, but as far as i know ONLY the 5sp came with l98 cam, dual cats and 3.42 rear, all the AUTO LB9 i have seen didnt come with dual cats, l98 cam and 3.42 rear. so the cam and dual cats makeup the hp difference

thanks for the reply, thats what i was thinking myself. He said his Auto has the L98 cam in it and so is he wrong I'm assuming?? I don't know where he got that info but its his defense I guess... anyone else?

Do a search, you'll find a bunch of arguments but the general concensus is that all the 91-92 cars came with the L98 cam.

"In 1990, the base engine for the IROC was finally the LB9 TPI 305 rather than the base LO3 V-8. However, G92 had to be specified now to get the better cam/230hp LB9 motor in the 5 speed LB9 IROC-Z."

"G92 performance packages were only available with B2L or LB9/5 speed."

its in the tech data

There are numerous errors in the tech data.

I have a non-G92 91 305 and it was never apart before and it had the L98 cam.

just curious, how do you know for sure its a L98 cam

I degreed it and used a dial indicator to check lift.

187whp and 270wtq.....bone stock!!! So that's around 230hp and 320tq at the crank. All in my 1991 LB9 auto Trans Am.

My car had the single cat with 2-1/4 cat back exhaust. However it also came stock with an aluminum Driveshaft and aluminum drums. I don't know how much power aluminum parts make over steel and discs.

All Speed Density TPI cars had the L98 cam.

so if thats an error in the tech data, why isn't it being corrected?

Dunno. Lazy? Maybe when they fix that error they can fix the search engine. Most of the time, they want to far of a general search that you get 500 posts that have nothing to do with your post. Then you have to wait 1 minute, which is forever when you are staring at a computer screen.

Stuff there has been wrong for more than 5 years, nothing new about it. Some have tried to fix things here and there but there are always things hanging around... none of us are perfect after all.

From 87 - 89 The L98 & LB9/M5 used the same cam, and the LB9/A4 used the same cam thats used in the LG4 (87 only) and the LO3 (88 & 89).

STARTING IN 1990 and going through 1992 all TPI cams use the SAME PART NUMBER FROM GM, therefore they use the same cam...

WITH THAT SAID!, you must note that the LB9/M5 can be rated as much as 10 hp more BECAUSE many of them used a dual cat system starting in 1989. THis was suposed to be standard on the FORMULA and GTA, and an option on the Trans AM, IROC and Z28.

Your friends 1991 Camaro, according to the literature the "OFFICIAL" rating from Checy was 205 HP for either engine with the M5 or the A5 in the camaro. IF he has the G92 then he SHOULD have the dual cats which would boost him up possibly 235 HP...

No where in the Chevy Camaro literature can I find a rating of 235 hp for the LB9/M5/G92 combo, its just not listed.

John

I'm new to all this... what is a speed density camaro?

I'm new to all this... what is a speed density camaro?

in 1990 all TPI cars changed from MAF sensors to MAP sensors (speed density).

Interesting thing about G92, everywhere I have read does state it was supposed to be standard on 1989 GTAs, yet I had one that was single cat and no G92 on the RPO.

From 85-1989 The TPI powered F-body (and corvette for that matter) used a Mass Air Flow sensor, AKA MAF. As air passes by the MAF it cools a heated wire, and the more air that passes over the wire the cooler it gets, as the temperature changes the voltage through the wire also changes, this is compared to the air temperature in the Plenum. This combined with the O2 sensor you can accurately determine the proper Fuel to air ratio for the engine to run properly. The down side is the MAF is restrictive and the ECM program is much more generic, and slower. The up side is modifications to the engine are easy as the computer compensates for them.

Starting in 1990 the MAF was droped and replaced with a Manifold Air Pressure sensor. SD comes from "Speed Density" in effect the the sensor measures the pressure in the plenum, combined with the temperature in the plenum and the O2 sensor the computer can calculate the proper air to fuel ratio. THe down side is the SD systems are very sensitive, most modifications beyond minor will require a re-tune. The Up side is the restrictive MAF is gone AND the programming is much more specific. Tuning is slightly more difficult BUT on the same engine you can get better performance.

IIRC starting in 1993 or 1994 onth LT1 the MAF returned and was used in conjunction with a MAP.

Make sence?

John

The tech data is a mess because it's been a mess for years... Keep in mind its not something that was created for this site, it was borrowed from another site back in the early 90's. It's been edited countless times since then and is IMO the best historic outline you'll find for a car that was produced for 10 years. It's better then nothing, which is what most enthusiast groups have on thier websites, but its still a victim of errors. The biggest problem is that there isn't any one person who knows all there is to know about every car from 82-92. Most of the information can't be verified and there will always be someone who swears his/her fbody is one of a kind and has the paperwork to prove it.