I have read on several sites on the net that GM may have for some reason or another underrated the L98. Anyone know if there any truth in that?

 

yea i was curious about that too... what numbers would a stock 1990 iroc-z (g92) dish out on a dyno compaired to the GM rated numbers?

 

I don't think the hp is underrated. These engines make so much torque that they can move the weight of an fbod or vette easily. The first gear pull in my 89 Formula 350 is as good as any stock lt1 or ls1. It just runs out of breath at 4,500.

 

GM has underrated alot of engines, I wouldnt be surprised if the L98 has a little more then advertised.

 

Yeah, no kidding. Think of the 302 in the Z28 way back. What did they say it had, like 250 horses or something? Yeah, riiiiiight.

 

Anyone ever dyno a stock L98? I'd be interested to see RWHP. LS1's are dynoing almost 300RWHP bone stock, consider 10-20% loss, that doesn't add up to the advertised 325HP. More like 350HP.

 

they advertise flywheel (325) horses on the LS1?

 

GM does underrate most of the f-bodies with respect to the corvette.

LS1's are pretty restricted with stock lid and exhaust to keep the power below the corvette's, then they just underrate them some so that not only are you happy when you dyno it, but it doesn't look like they are charging 25K for a camaro with 345hp and 50K for a corvette with 345hp.

I would not be surprised if the L98 f-body was slightly underrated to keep it at a good sight from the corvette power.

As far as my LB9 i had.. with 135,000 miles.. and just these mods: 80 series flowmaster with 3 inch catback, high flow cat, k&n, splitfires, Hyperjunk chip, msd coil, accel 8.8 wires, airfoil, stewart high flow waterpump, 170 thermostat with 4 little holes, Tb bypass, and a stock tranny acting up.. did i mention 135,000 miles.. it pulled 177rwhp and 243rwtq. which is approx. 220hp and 300 tq figureing a 20% drivetrain loss. The car was rated from the factory with 210hp and 285 tq***.. so that tells you right there.. imagine if i had dynoed it at 35,000 miles.

*** 1990 Lb9 2.73 a4 base Iroc.

 

so your saying a ls1 (lets assume) that the ls1 had dynoed at 325hp it most likley has 345 at the fly wheel.

 

Sorry guys but the l98 in no way underrated. Back then some where made better than others and some ran better than others.but they were not underrated.

 

"some were made better"

That's not really true, though...

In a factory setup you should assume that all motors are built equally. Their only differences being the break-in drive period.

The motors are not "built differently," they just have differing wear patterns after the first 5,000 miles which determines the motor's lifetime power and torque.

Every L98 that came out of the factory had the same potential (within reason) to be just as powerful than the most powerful L98. Just get a good driver behind it for the first few miles and you will see the difference in any engine.

If every car was driven the exact same way for the first few thousand miles, then it would be pretty easy to assume that they all would have the same power and torque.

 

Usually the drivetrain loss is around 10-15% for a manual and 15-20% for an auto.

So 325rwhp on the dyno for a auto is 385-400 hp at the flywheel.

X=flywheel hp
325= dynoed rwhp
100%-15%=85%
85%= .85
X * .85 = 325
X=325/.85
X=385

 

Most stock L98 dynos I've seen get like 212RWHP and 314RWTQ.

 

most LS1s i've seen dyno at about 290hp/340-50ish tq.

One of my old car-club members was still fighting for 300 horses even after she had the miraculous "lid and filter" on her 2000 Z.

oh, yeah it was an auto

 

I think it was Stangkilla on this board who dynoed his stock car and pulled 214rwhp.

It was an auto so lets assume 18.5% Drivetrain loss. It equals out to 254HP...

-Rippin