Crank Hp vs. RWHP

[D-rek]

What is a good rule of thumb for losses through a manual transaxle? My car dynod at 410 to the rear tires just curious what the motor is putting out.

[Josh_K]

About 30-35% loss for a auto and 20 to 25% loss for a manual. I would say you have a honest 500+ hp engine.

[Josh @ DanZio]

It all depends on the dyno and the way the dyno is set up. It also has a lot to do with what kind of drive train and tires you are running. We use a Mustang dyno in our shop and we see anywhere fom a 36% to 28% loss depending on drive train.
We just ran a customers blower engine in my car on our chassis dyno. We then pulled it out and ran it on Jim Horn's engine dyno at HP Engines. It was a 36% loss. This was through an Mendeola S5, 934 cv's, and 35" baja claws. There are an inumerable amount of variables that can cause it to be different.
Our dyno is very stingy for horse power numbers, while others in the industry are very forgiving.What was your set up and who dynoed it?

[FABRICATOR]

We only get about a 20-25% loss on big trucks and buses. I would imagine that the lower loss is due in part to everything operating at lower speeds. Dual wheels probably loose a lot less on the rollers too. What gear you test in can also change things.

We've run powerful cars and pickups on the dyno but they have to be blocked and chained. That means the tires are pressing really hard on the rollers and wasting HP. It's not the same efficiency as on the street (or dirt).

[BioMax]

When we had our car dyno-ed they removed the wheels and bolted the machine directly to the car. I was told that the machine was very "stingy" with numbers, but I thought the idea was killer. A whole hell of a lot safer too!

[BAPerf]

After reading hearing everybody and their brother say that their dyno is "stingy", or so and so's is optimistic, etc... I've had enough! Everybody's dyno reads low, just ask them... We don't race dyno's so why does it matter? The gentleman at Danzio's answered the man's question with his observations, and I think that will give the original poster an idea of where he stands.

[Josh @ DanZio]

After reading hearing everybody and their brother say that their dyno is "stingy", or so and so's is optimistic, etc... I've had enough! Everybody's dyno reads low, just ask them... We don't race dyno's so why does it matter? The gentleman at Danzio's answered the man's question with his observations, and I think that will give the original poster an idea of where he stands.

This exactly correct. We use our dyno for tuning not bench racing. The most important thing about the horsepower numbers and dynos are repeatable results. It must be able to be accurate over a variety of tests and conditions. This way when things are changed we are able to determine the scientific result of those changes, or the difference in power from set up to set up.

I'm not gonna lie, people love to see the horsepower numbers because they are fun. However, in my opinon the bragging rights are only good if everyone has there car on the same dyno. Dyno to dyno vary so much that comparing results is irrelevent and unscientific.

[Saleen F-150]

Wouldnt Gearing show different Numbers on the dyno??

[Josh @ DanZio]

Wouldnt Gearing show different Numbers on the dyno??

To some extent. It makes a bigger difference with the mass of the gears.