trying to settle an argument. What do the big three, ford,gm chrysler, and everyone else for that matter refer to when talking HP. Does a new ford that claims 300HP is that crank or RWHP. like in a tpi that has 230 HP? wondering what most people talk about when they are on this topic? curious any imput appreciated.

 

Factories talk in Flywheel horsepower.... GM advertises the ls1 at 320hp and they average 300 at the wheels stock...so a tpi that make 230hp will probably barely put 200 at the tire.

 

Auto manufacturers ALWAYS advertise in flywheel horsepower, with the engine on the stand hooked up to an engine dyno. They NEVER advertise the rear wheel (or front wheel) chassis dyno numbers.

 

To further clarify, they are required to rate their engines as-installed in the vehicle they are selling it in - air cleaner, exhaust, accessories (alternator, water pump, fuel pump), that would be used in the car, when it is installed on the engine dyno. So, it is what has become known as "net flywheel horsepower". This is why identical engines can have different ratings in different cars (Vette vs. f-body, for instance - different air intake, different exhaust make a difference in rating).

The "old" method was "gross flywheel horsepower", where a lot of cheating went on - long tube headers, velocity stack on a carb that wasn't used on the engine, different carb to come up with peak horsepower and peak torque, electric water pump powered by the facility, etc. In fact, that is how almost all crate engines, whether factory or independent, are rated.

 

So using the old method. What is your opinion on what the LG4 would be rated. It would have a better air source, better exhaust, no water pump, power steering pump, air pump, no fan, etc.

I would be very curious.

 

honestly, i think you would be rather lucky to see over 130 RWHP on a non-rebuilt, lightly modded 20+ year old LG4.

 

https://www.thirdgen.org/forums/tech...light=dyno+lg4

the following is from post #2

""This is not exactly what you are looking for, but Hot Rod dyno'd their completely stock 82 LG4 and ended up with 145 HP @ 4000 RPMs and 165 ft/lbs @ 2400 RPMs. This is at the flywheel, not rear wheel horsepower. The LG4 is a pathetic engine in stock form.""

 

The early LG4's would be in the 165 range. The later ones, with higher compression, a little higher, 175-190.

 

I took my 84 T/A to a shop here that had a chassis dyno. They told me they couldn't get a true reading because I can't get to WOT in my highest drive gear (overdrive) because the car shifts. We tried it once and ouch...I thought the car was going to come apart...good thing the chains and mounting points held. Hoever, I did several 1st gear pulls and the best 1st gear pull reading I got on my L69 was 100hp and 120ft-lbs torque at 4200rpm. THis was an unrebuilt engine with 127k miles on it. Now, I don't know how to get a proper reading for my automatic on the chassis dyno but at least I have a baseline for when I get my new 350 finished.

 

57 kid is exactly right in the way they rate horsepow all acc installed now my question is if a tpi engine dynos at 245 hp at factory , then when us guys test them on chassis dyno we say its like 17-20 percent less. but havent they already used up a few percent like maybe 10 percent already so we shouldnt say there is a 20 percent loss at chassis dyno. am i way off on this one lol or somewhat correct? ive been thinkin to hard lately.

 

they can also sway it either way to make one car seem to be faster than another. the best example is widely known and that was the the LS1 corvettes were rated higher than the LS1 equipped F-Bodys and the motors were identical, and there were actually reports of the F-Bodys reading higher on the chassis dyno. GM did that to make it seem like the corvette was faster to justify the significantly higher price on the vette than the F-Body.

 

A chassis dyno will already include the losses from the accessories and intake/exhaust. Chassis dynos are also one of the worst ways to measure HP. There is no standard, and results can be all over the place depending upon how it is set up and operated.

Engine dynos are much more accurate. The only way to measure drivetrain losses is to do an engine dyno test w/accessories/exhaust, and then repeat on a chassis dyno.

There was a magazine article a couple of years ago about rating the power of your engine. They said in order of accuracy, from highest to lowest: 1. engine dyno; 2. dragstrip ET and MPH (along with vehicle weight); 3. parts combination; 4. chassis dyno.

I have no reason to doubt them.

 

that's interesting, considering the rough equations don't include air resistance, or much of anything really, just the absolute basics. though the less numbers to fudge on the better