avro206

beiseds the camshaft substitution--is there any other difference that contributed to the 25hp loss??

thanks

f-crazy

iTrader: (-1)

the N10 exhaust

avro206

I don't think so--N10..isn't that dual cat exhaust? If there are just diffeences in exhaust diameter, what are they?


Just to clarify--I am talking from the 85 215hp rating to the 86-87 190hp rating (automatic obviously)

87WS6

iTrader: (1)

The autos got the peanut cam and the manuals got a better one. That is the reason for the difference.

If you have a standard version of the car with the dual cats you had like 230HP.

f-crazy

iTrader: (-1)

only untill 91...then all tpi cars had the l98 cam

the 85 was very close to the fastest LB9 of the years..
from 85-90 the auto lb9 cars had the peanut cam..
after that they ALL had the l98 cam

this has been gone over like 456 times..

ill let ED or TPI Roc somebody hanlde this one in greater detail...

avro206

Okay guys--I said in my first post I know about the cam--so this doesn't need going over

I am trying figure out if the exhaust was a different size for automatic 190hp TPI VS 215hp auto TPI (85).

So does anyone know?


(oh and FYI 85 was NOT peanut cam)

jfreeman74

I am pretty sure the exhaust was the same. The only differences between the 2 that I know of are the cam and the ECM.

T3am Z28

I think it was just a cam difference.. but I'm not totally sure either..

-LJ

avro206

okay--thanks. The reason I am asking is this guy I know (with an 85 IROC-Z) is replacing his with an aftermarket exhaust.

My stock exhaust is in bad shape--so I was hoping his was bigger--I think I'll swap it anyways. Have no dough for cat back

gmgod

I had an 86 iroc lb9 auto car with the peanut cam and the stock exhaust measured 2 3/4 inches, the same as the 87 l98 car I have now. The exhaust on the 92 lb9 auto car I have looks to be 2 1/4 inch. I guess they decided to choke the 90-92 lb9's down to the 205 hp rating through the exhaust, makes no sense to me.

gmgod

I guess I did'nt really answer your question. I THINK all of the maf lb9 cars got the 2 3/4 exhaust.

jfreeman74

I'm not so sure about that. I just removed my stock exhaust and it was 2 1/2.

mikobu3

why does the 85 305 tpi 215hp have only 275 tourque compared to the 295 rating on g92 230 hp cars, i no the computer is diff could that be the loss in tourque, i was reading an article on the 85 305 tpi cars, they had a test with the ta and iroc, q-mile run, the 85 iroc pulled off a 14.90 while the ta pulled off 15.00 in the q-mile, i will try to find the article for you guys to read , it was pretty interesting

Grim Reaper

There's another reason too, the eprom is different. The Auto cars have 2.7x rear gears and the spark curve is "milder". While the standard cars with 3.4x rears have a more aggressive spark table.

Also, there are a LOT more variations of eproms for the standard cars vs. the auto. GM was always trying to improve the programming of the standard cars to compete with Mustangs.

jfreeman74

My car is an auto and it has 3.42 gears in it not 2.73. None of the '85's came with anything less than 3.08. The LB9 Auto was the only camaro in '85 that had 3.42 gears. Some of them came with 3.23 gears I think but most were 3.42. The '86 came with 2.73 gears almost all of the autos. For some reason GM chose to use the 2.73 gears in most of the camaros after '85.

Grim Reaper

Well, the auto TPI 305s ONLY have one BIN with no variations for the rear gears. While there are variations for other GM vehicles (mostly Y-bodies) based on their rear gears. But for 305 TPI autos, one BIN seems to do all from what I'm finding.