Jbferra

I recently had a dyno test preformed on my 1992 conv. , 6 speed at a car show in MN. The car has 55,000 miles and the only engine mods have been high flow air filter, induction foil and Comp Cam roller rockers. (I stayed w/stock ratio of 1.5) The LT-! is rated a 300hp from the factory which is "gross" horsepower (rated with no power train power losses). The test results from my dyno test were explained to me to be "net horsepower" or power to the wheels. The dyno operator explained that you should add 18% to the "net" horsepower results of the dyno test to come up with a comparision of any power increases the mods may have caused to boost the factory rating.
SO this was the results....Dyno "net" HP to the wheels was 272 horsepower. If I add 18% to the "net" figuire , you get 321 "gross" horsepower ...which seems to indicate that the mods I did to the engine gained me 21 more horsepower from the factory rating.

Is this a fair assumption??......Would appreciate any feedback on this issue.

Thanks.................JB
:auto:

mn_vette

I believe it is closer to 15% for manual transmittions. 272 * 1.15 = 312.8.

12 hp seems like alot for roller rockers and an air filter, but perhaps not.

vader86

It has 300 NET hp, gross is just an engine with no accessories measured on an engine dyno.
Net is the factory ratings since the 70s (72 i think?), with the alternator and all accessories on the engine.

LT1s have 300 net, then you usually lose about 16% of that thru the manual transmission, and 17-18% thru the automatics (additional friction).

Your car gained probably 10-15hp from just the Roller rockers and air filter.

Strick

Hey JBFerra, Thanks for this post. This is something I've always wanted to know as I have basically the same LT-1 that you have plus headers and an electric water pump. Hopefully, I'll be on a dyno this year. :thumbs:

mn_vette

I'm not so sure about this....I've got a poster at home done up for the LT-1 engine when it first came out in '92(it's currently hanging in a frame in my living room). This poster quotes the power output at 300 and the gross or net I'm not sure at 315.

thepenguin99

He is correct 300hp is the net rating. Gross ratings are without accessories/exhaust/ect and haven't been used on production vehicles since the early 70s.

Jbferra

Opps....thanks for the clarification about "gross" power. I'm looking for power increase from "NET" like you stated.

JB

vader86

Starting with 300 at the crank, it should put out in the 250-260 range.
Since youre getting 272 at the rear, using a .16 loss, I get 325hp at the crank. With a .15 loss, about 320hp at the crank.

Mr Mojo

Well my stock LT1 with well over 110,000 miles dynoed at 285 at the wheels, only mods are K&N and Corsa cat back.

The Example

I believe that mine dynoed 276rwhp stock. Has flowmasters, ignition, couple little things.

91 black convert

You're forgetting that he said he had an airfoil installed, too! :D

VMAX451

Just nitpicking here...
To back out a 15% loss, you should divide by .85, rather than multiply by 1.15 ---> 272/9.85=320. even more power!

Seems like everyone likes 15% for 6-speeds, but do they really dyno stock at only 255? Seems a bit low, but maybe it's right. :confused:

R23HTC

Here's a copy of my stock run. K&N and an airfoil



Here's a copy after mods. Though it was lean due to bad fuel pump.



It's since made 329rwhp, I'm just waiting to get my new sheets. (left them in Houston. :( )




[Modified by R94 LT 1, 5:23 PM 7/29/2003]