Most data came from chassis dyno operators comparing RWHP with the manufacturer's engine rating. Maybe a couple tuners would run an engine on an engine dyno, then a chassis dyno. Various brands of chassis dynos would give different HP numbers for the same vehicle. Chassis dynos calculate torque and HP by measuring incremental angular accelerations of the big drum. Its inertia "loads" the engine and goes into the calculations. Unknown and variable quantities of inertia come from the wheels, engine flywheel, transmission etc that contibute some inertia to the whole system aft of the engine.
If one really wanted to see large chassis dyno numbers, he'd use an aluminum flywheel and the lightest wheels and tires he could find. The engine would make the same torque and HP, but the chassis numbers would be higher. I believe that's how it works. CSXDreamer is right. However, don't expect HUGE gains by just changing to an al-um-i-num flywheel and lighter wheels.
You may see something, but you need to consider what you gain to be a benefit. Read the threads and look on the web about using which flywheel for your application. There are also variables on the engine dyno as well. For the best numbers I have seen builders use electric water pumps, carb spacers with the shops carb and stepped headers. There is also parasitic loss due to accessories like water pump and alternator, not to mention the differences in cobra headers and the short little air cleaners we use.
This all happens before the drive train loss! What really matters is how much are you able to put to the ground and how fast can that peak power be delivered. These cars weigh between 2, and 2, pounds.
When you think about it, even HP at the wheels is pretty damn good. I think chasing a big RWH number on these cars is more vanity than common sense. And, yes, I have this sickness. Next car will be the "common sense" car, I promise. I saw the point made by CSXDreamer illustrated on one of those half hour car shows where they hop up cars. They took a showroom stock import sedan and prepped it for road racing. They started by taking dead stock dyno readings and lap times. Next they upgraded the wheels, tires and brakes, and did some intake and exhaust improvements before putting it back on the dyno.
Feel free to leave us a comment below and ask us anything that might be on your mind. We love answering questions from you guys and creating new material to inform our readers. First Name. Last Name. Call Us: Email Us. Flywheel by West Coast Engines May 21, Summary So what have we learned here today? Joined Aug 25, Messages 1, Location Connecticut. Sure, you find the percentage of Driveline loss. Sorry, but doing math that way doesn't work.
The percentage of loss cannot be treated as a constant. The only way to truly compare for a specific car and motor is to measure the hp of the motor on both a chassis dyno and on an engine dyno, and then you run into the fact that they are two different dynos. That would mean RWHP should be FredK'03Cobra said:. Click to expand Last edited: May 10, Just take a silly wild assed guess? Five or seven percentage points can, and will, make a significant difference.
People get blasted on this board daily for coming up with numbers that they may believe are correct, but just aren't real. Remember the recent thread about the SLP ad where they claim hp? Members here blasted SLP for using numbers derived in the same fashion you just suggested.
While many folks out there do their math that way, I just choose not to perpetuate the fantasy. No biggie, just a difference of opinion. Steeltwo Active Member Established Member.
Booyah Cantankerously Blunt Established Member. Joined Nov 20, Messages 4, Location Last edited: May 11, Wow, I didn't realize this would get to this depth of a thread!
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