L98 Underrated?

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.

Originally posted by angel71rs
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.

Originally posted by StealthElephant
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.

Originally posted by lordmetalz28
so your saying a ls1 (lets assume) that the ls1 had dynoed at 325hp it most likley has 345 at the fly wheel.

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

Originally posted by kraftopia02
"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. Its a given that engine to engine is going to be different. Happens all the time. That's why they make 8-10 sets of pistons. Each cylinder isn't identical in a factory engine from engine to engine. Tolerance's aren't the same, that's why they give a range. And just about everything affects power. Many things can add up to a great "factory freak" or a complete dog.

i guess you are right, but i didn't think that the factory flukes would really add up to a noticable difference.

about the l98 being underrated...
i think it was always like 10 short on the vette
andthe reason they gave on thirdgen.org...
vettes had aluminum heads while the fbodies had cast iron
i think they mightve given another reason too, not sure
but when you're thinking abotu the narrow horsepower ranges back then (10 hp was a bigger leap then, than it is now) it might be underrated for the camaro, might not be
think about it:D

Actually, if you use the formula hp= torque x the RPM where max hp is supposed to occur divided by 5252 .


345 x 4400 = 1518000

1518000 divided by 5252 = 289 @ 4400 RPM

So according to the laws of physics the L98 actually produces 289 hp at the crank. Or 300 hp @4500 RPM for the dual cat option.

LT1 = 320 hp @5000 RPM

LS1 = 345 hp @5400 RPM

The Corvette is a lighter car, so they could get away with not having a large HP difference and the vette would still outperform an fbody to an "acceptable" degree in the hands of a good driver. I had a C5 vette run a 13.5 next to me as I ran a 16.xxx the first time I ever ran at the track. Back then it just looked really bad getting smoked like that, but when I think about it now 13.5 wasn't very impressive.

It's mostly insurance reasons as well....that's pretty much why HP is underrated. The government nitpicks car companies to death over things like that.

I doubt the TPI and LT1 cars are under rated. I know when I dynoed my 96 WS6 it was 274rwhp which comes out to about 310-315hp. With the K&N, thermostat, and airfoil might have made up the difference from a rated 305. Same for the TPI cars I've seen dynoed that were stock. I haven't seen a stock 350 TPI dyno higher than 210 rwhp.

The LS1 is definitely underrated. Its pulling rwhp numbers the same as what its flywheel rated. The turbo Buick in the turbo TA was under rated by about 40 hp also.

I know when I dynoed my 96 WS6 it was 274rwhp which comes out to about 310-315hp.

Yea, but if I remember correctly, wasn't the LT1 camaro rated at 275-285 hp in 1996?

Originally posted by mako350Z28
Yea, but if I remember correctly, wasn't the LT1 camaro rated at 275-285 hp in 1996? LT1 was rated at 285 in 96-97 in the Z28, Formula, and Trans Am. If you got a WS6 or SS, it was rated at 305.

If you have the ram air then that would account for the loss of power. It's kind of hard to use the ram air when you are sitting still.

don't they normally have the air element exposed during dyno runs? the ram air shouldn't matter.

Yes it would since the ram air does just that - it rams the air into the intake when the car is moving, providing denser air for the combustion process. Even if the hood is open, there is nothing forcing the air into the engine. It's getting pulled in instead of pushed in.

Air is always getting pushed in, it never gets pulled in.

Ram air does not make the air denser, cold air provides a denser charge, and therefore more horsepower. Though many will argue it, there is no significant "ram air" effect on an automobile.

All you want it is unrestricted cold air. Ram air on a dyno is restrictive, since the car is not moving. Keeping the air element exposed removes the restriction, most places have some way of keep the air cool that is going into the engine for best performance.

Wish I could remember the web site that explains the way it works but it does work. There is only one catch though - it works in the higher rpm range at high speeds (usually at 90 mph and above).

It works because it provides denser (hence more) air to the engine. Atmospheric pressure is lower inside an engine than it is outside and actually gets lower the faster the car moves. A good ram air system evens out this inequality and, on a really good system, provides about .156 psi of positive boost over atmospheric pressure.

You have to be going like 150MPH for 1 PSI of pressure, you get .1-.2 PSI at 100MPH....this is under PERFECT ducting of the sytem and a perfectly sealed airbox.

An engine at WOT has 0 vacuum, ram air does not change any inequality, the theory is if the system is designed correctly that pressurization occurs in the airbox....at automobile speeds it's almost worthless....stock ram air isn't correctly designed, it brings COLD air in, nothing more.

Originally posted by mako350Z28
If you have the ram air then that would account for the loss of power. It's kind of hard to use the ram air when you are sitting still. Don't think so. For that setup takes about 90-100mph to see any real effect of the intake setup. You'll find that the gains with the ram air is it being a straight shot and not doing two 90 degree bends before the TB.

The only problem I ever had was heat soak because of it being right over the radiator. The summer took its toll on that car on back to back runs.

Originally posted by mako350Z28
Actually, if you use the formula hp= torque x the RPM where max hp is supposed to occur divided by 5252 .


345 x 4400 = 1518000

1518000 divided by 5252 = 289 @ 4400 RPM

So according to the laws of physics the L98 actually produces 289 hp at the crank. Or 300 hp @4500 RPM for the dual cat option.

LT1 = 320 hp @5000 RPM

LS1 = 345 hp @5400 RPM
Even if that is correct, it will present you with gross hp--not net hp at the flywheel. Which is how engines are rated.

That is the way it is done. Period. As for the gross and net, how can you lose 45 hp from the crank to the flywheel (while not losing any torque), considering their close proximity?

Belt driven accessories and many other things factor into parasitic loss.

You lose anywhere from 30-50HP, Crank horsepower is SAE Gross, many 60's muscle cars are rated at 400HP, but they were rated in SAE Gross. They were dynoed with no accesories, open exhaust, and in actually could have put out 100 less HP in the real world. Gross is not accepted anymore because it wasn't honest.

SAE Net is the standard today in HP rating, it takes in account the engine running with ALL accessories, exhaust manifolds ETC, anything that would take away horsepower.

Rear wheel horsepower takes SAE Net horsepower, and factors in drivetrain loss (transmission, driveshaft, etc etc)

LS1's dyno like 290RWHP bone stock...it's just not a fair battle putting stock L98 vs. stock LS1

Ok, I can got with that but it still doesn't answer why it doesn't lose any torque in the process.

BTW, I have seen in a few places around the web that the power output readings were taken at the rear of the transmission on a 3rd gen, not at the flywheel.

Don't know if that is true or not. Anyone got a clue?

There is rear wheel torque as well...again, 10-20% drivetrain loss.

i know this isnt a ram air message board but im about to put a smile on the believers faces and ruin the non believers day. my mods are listed unde rmy signature but ask yourself this. from a 55mph role can a lB9 beat a 94-98 mustang gt. well it was about 49 degrees monday night and i have the sheet metal ducting ram air that is professionally built and i got a hell of a boost on the highway and i wasnt doing more then 55 and i never felt a boost more powerful in all my time it helped me beat a stock gt and it works. weather its cold air or cold air going into the motor bieng rammed it ****in works its the cheapest most worthwhile mod anybody can do on thier tpi motor. this is my believes you cant prove me wrong it happened to me

Good work on the GT....but I refuse to believe the word of a handful of people who go out and spend money and swear they feel a difference when physical and mathmatical fact states otherwise.

Its funny because when I talked to my boss one day a while back talking about making my Iroc hood louvers "functional" to open and close with my throttle to give me ram air, he told me ram air wasn't important and began drawing the very "nozzle" that dave rodabaugh explans http://www.vetteguru.com/ramair/

There I am standing in a parking lot watching my boss draw that very "divergent" nozzle as he tried to explain why packing factors prevent ram air from being practical on a car. A few days later I go into "Advanced Tech" and being reading that article and the thread that followed. If it were just people online arguing I probably wouldn't feel as strongly....but I have to believe fact over what people "claim" to feel.

Maybe the fact that my boss is an engineer, an obsessive F1 fanatic, math god, and former owner of a dyno shop makes me believe him over whatever anyone "feels"

well i felt it big time and i spanked a mustang gt im so proud

Well the stock 3rd gen setup with the Y into the TB is a pretty restrictive design, so I wouldnt' be surprised if the combination of cold air and less restriction got you more power, but it wasn't the "ram air effect"