Well I brought my daily driver to the dyno just to see what exactly it makes to the wheels. Its an 89' IROCZ with an L98. The only things done to it are a BBK T.B. and a Hooker Catback exhaust with no cats. But It does have a T56 from a 95Z28 which helps with mileage on the highway but with my factory 2.77 9 bolt it kills acceleration. In 4th Gear at 5500 RPM the dyno says Im doing 162 MPH!! Is this right or are things screwed up? And my Numbers were 199.4whp and 279tq. Is that about right for a stock L98? I thought it would be higher than that? Thanks for your help guys.

 

the motor is stock and came out with 250 horse at the flywheel

hard to believe and the torque number says cam

 

You mean factory flywheel hp is 250?
For the torque is that more or less than factory?

 

I had a 1988 GTA 5.7 (sold a couple months ago) which made 224 hp at the rear wheels. I had headers and a few little things done to it you don't list. 304pounds torque at the wheels.

As far as the top speed, aerodynamics come into play on the road where a dyno doesn't have to fight the wind.

Real world, your car MIGHT hit 140-145 mph or so on the top end.

jms

 

In 1987 Hot Rod magazine tested two new cars
at the proving grounds.

87 Iroc- L98- Showroom stock.
87 Mustang 5.0- Same.

L98 Iroc- 149 and change.
5.0 Mustang 140 and change and blew up before completing run.

Still have the mag around somewhere.
Headers and slight mods guessing mid 150.
Also 89 had a few more hp & Torque than 87.
The faster you go, The harder it gets

Later

 

I figured the torque would be more.

 

IMO those numbers are a little low, especially for a manual car. My car put down 229whp and 359rwtq through an auto. Only had a pvc cai, 3 inch catback and an open 3 inch cutout. Timing was dead stock and I want to say that was on 87 octane so I know the timing wasn't bumped.

 

Mine put down 230rwhp and 305ftlb torque with headers and runners. The motor had bad rings at the time and was blowing oil.

I would expect a stock 89 L98 with T-56 to put down around 215rwhp and 310ft lb torque.

 

Don't worry about what the damn dyno says. They arent reliable indicators of true hp. Not even good for tuning in my opinion. The only thing they are useful for is finding your peak hp and tq rpms for choosing the correct gearset, and comparisons between parts, if only on the same exact dyno.

You dont have that car in japan do you??? Nice car BTW.

 

I can vouch for the fact that a bone stock L98 will do 145 in real world conditions.

>.> <.<

 

Your number appear about right for a stock L98. Factory stock was 235 HP and around 340 TQ at the engine. After you figure in drive train loss you are close. My all stock 1986 L-98 vette only had 194 RWHP.

 

Dyno's are good for comparisons with a baseline. There are a lot of variables, both with atmospheric conditions from one day to the next and with possible calibration errors on the dyno. You need to check carefully all of the data that was put into the dyno calibration to be sure you are getting the correct hp & tq readings. What altitude was the dyno actually at, and what altitude was it calibrated for? What did the o2 sensor show for your a/f ratio, and was it accurate? How did the dyno a/f ratio compare to what your stock o2 sensor was showing? You probably have a good baseline for checking future mods, or even for doing some tuning, but I've seen dynos off by 25 to 50 hp just because one of the set up calibrations was wrong.

 

When my '87 350 IROCZ was mostly stock, I had it at a drivers school at Michigan Int raceway in 1991 or so. We would come out of the infield in NASCAR turn 3 and head for the main straight. My car would top out at 135mph and be starving for air, thanks to the TPI. The car was not good for top speed, but the handling and torque was great. I still own this car that I bought new in '87. I've made a few changes since then.

 

My original motor would knock a lot, and draw out timing. Running 100 octane helped. I can't remember what it was, carbon deposits due to age, or a bad TPS...Never really did fix that...

When I dynoed it, had intake and headers & small stuff done, got 255 hp and 320 torque.

Anyway, don't rule out some vague thing causing the car to run less than optimal.

 

The 200 RWHp sounds about right. And the 162mph might be possible with your gearing on the dyno, but you wont get it on the road. You will not be developing enough torque to drive it through the air.

 

according to calculations with stock size tires ( not sure what you are running with those wheels ) 5500 RPM in 4th would 152 MPH

And to add to the Dyno numbers game, my 87 L98 mostly stock did 190/280 at the wheels. It also ran a best of 14.2 @ 95 mph.

 

Like Jay mentioned stock size tires (245/50/16) would yield 152 mph on that configuration.

Be very careful with the T56 on highway. It says you will be doing 60mph at 1100 rpm with this same combo, so anything over that is basically speeding.

But yea it sounds about right,

 

Hey my all stock 28,000 mile 1987 b2L or L-98 put down a best of 215.4 hp @ 4400. If you go to the after market venders section and look up Dyno numbers any one interested? You'll see my build-up and what you can get with just bolt-ons. Last run showed a gain of 29 hp and 49 ft-lbs TQ. Robin

 

Also a well respected auto writer who was very well connected with the C-4 platform states that GM’s accepted drive train loss was 18% for the L-98 6 speed and 22% for the L-98 auto. Since our f-bodies have very close drive trains we could use those figures to calculate our flywheel HP/TQ.

Also I misprinted it's Aftermarket Product Review...sorry