Competition Engine HP/Dyno Questions...

[Wingate]

I have recently purchased a 94 12v that I plan on building up to approx. 800hp. I keep seeing dyno pulls on chassis dynos and what I'm wondering is when I see a report of 800 hp. is that at the wheels, or is the dyno software calculating flywheel hp?. Another question, do they run with the transmissions in 1to1 drive? Surely running anywhere but at 1 to 1 (no overdrive or underdrive) would skew the #'s??. .

Another question, when the load comes on the engine, how far down (in RPM) do they typically pull the engine?.

I have thought of entering this little pup into some local events , but knowing HOW they are dyno'ing would be helpful while building it.

 

[Extreme1]

The power being measured is at the wheels. Some dynos measure HP and calculate torque, some measure torque and calculate HP. Unless the dyno is set up to measure your engine RPM (either reading an engine output or done with a combination of tire OD and gear ratio), you will be doing your own calculating to get the other (torque or HP) number based on what the operator gives you on the slip. Sometimes you are just given a sheet with HP or torque and MPH.



You will need to run the truck in 1-1 trans ratio which ever gear that may be (autos lock up the TC and run in D).



The engine will accelerate through its power curve. You will typically tell the operator where (speed or RPM) you want the run to start.



Beware of downshifting your auto trans at WOT with a locked up TC on a dyno, bad things can happen. I won't dyno my truck anymore unless I'm behind the wheel.

 

[Wingate]

Thanks for the info... mine is a 5-sp. manual... So they start on the bottom end and pull upwards to RPM limit?... makes sense. .

I have access to an engine dyno that I could use to measure real flywheel hp and torque... difference being that we typically run the engine up to full speed with approx. 1/2 load on it... once we get it to full speed, thats when you really jump down on it and see if you can drag it to its knees, or down to rated speed... whichever comes first.

Not sure if using the engine dyno will be relavent due to the amount of uprating that the engine will have. . Its not like I could use rated speed/power specs. from Cummins if I'm turning it 1000 rpm faster...

 

[DCreed]

sit back and do some homework. It will take near 920hp @ engine to reach 800 @ wheels due to driveline loss. Doing this on fuel only will require extensive engine and driveline mods costing thousands of dollars. Also bear in mind, if it is just a dyno queen and you plan to use NOS or meth or twins you will prolly get bumped into an "unlimited class" where 800hp isnt much.

 

[Wingate]

It will get driven some... probably not much... more of a toy than anything. While I havent done a bunch of research yet on the specifics... I do plan on turning the engine to 4K+... possibly 5k. I feel like I will have to replace EVERYTHING in the valvetrain, overbore the block to the max. safe limit(to get max. displacement), balance the rotating assembly, port/extrudehone the cylinder head, use the later style P7100 pump and a bigger set of sticks, then stuff as much air in it as possible(twins). I'm really not sure what # I can put up with that. . but I feel like it would be a good start. From that point, I may experiment with meth, nos, propane... etc. . I really would like to stay inside the "fuel only" realm. I thought I remember reading somewhere that the dyno classes were usually broken up into 12v fuel only, 12v unlimited, 24v fuel only, 24v unlimited... etc... Is that not the case???

Does running twins with fuel only put you into the unlimited class?

 

[DCreed]

Does running twins with fuel only put you into the unlimited class?

yep. dont ask me why but for some reason folks seem to think turbos MAKE power like meth does. So you can run a HUGE single and a 14mm Ppump with all the bells & whistles done and be grouped with guys that just have a fuel plate and BHAF, now take the same near stock truck and put twins on because you do a lot of heavy towing and you get bumped to the "unlimited" class where any and all power adders are legal.
I have to compete with guys running "race only" set ups like 3 stages of NOS, meth, ect. and I drive to and from the dyno and the truck works on the farm all week to boot.
Heck, pullers just go by inducer size, and deal with guys running a 3. 0+ charger with a 2. 5 bushing.

 

[Wingate]

Well, that ain't worth a crap... I would have thought that there would be more "levelling of the playing field"... . I need to attend some of the local events and see just how the different rules are. maybe their is some regional variation.



800 HP at the wheels isn't much out of a 12v?... . so what kinda #'s are respectable and competitive out of a 12v??????

 

[DCreed]

Depends on the class. 12v's are some of the most modded trucks out there and capable of well over 1000hp. Some pullers run closer to 2000hp! So I guess its how you define "competitive".