Max Ever Hp With A Screw ?

I'm curious about something, and would appreciate anyone chiming in either online or offline.

With a "screw" (take your pick, Whipple, C, D, etc.) and with just meth, what's the max Hp that's ever been made with no rules in place?

I hear anecdotal stories of big numbers in years past, but the et's of the time just don't support such numbers.

Thanks.

 

Well the el general car when they went 5.47 was around 4400hp according to petty. Taylor had to be pretty close to that number id think.

 

Are the "c" guys really up that high? I suppose in a perfect world, if Norm's super factor is applied. But really, that much?? I would have figured maybe 3200-3400 if actually tested? Theoretically a "c" can touch the 4's, but has this actually been done yet?

 

Exactly. I think he was around 263 mph. I don't know what those guys weigh though? If around the weight you indicate, then somewhere around 3400'ish hp probably in his case.

I have been "told" that a C at 225%, with the "right hat", has run 4200 Hp in unofficial testing. Whether I believe this to be the case or not, is another story. If you look at the basic math behind a "C" here is what you get. This is basic physics & thermodynamics & mechanics.

At 225% over and 10K engine RPM, you get about 474 pounds per minute of air at near 100% compressor VE. Norm says the "C" should be supercharging itself by about 19% or more at this point, but let's ignore that for a moment. About 9.4 pounds per minute of air will get you the gross potential of 100 Hp at the crank, to make power and to drive all the crank loads. 474 divided by 9.4 times 100 gives us about 5044 Hp of theoretical gross Hp production to work with. Lets assume (this is a big assumption...... so I may be totally wrong here) that the screw takes maybe 500 Hp to make the 50-60 psig boost at the mass flows in question.

So 5044 Hp minus 500 Hp loss, should be right about 4500 Hp to have fun with. Throw in friction and pumping/windage losses within the engine, and maybe a little further less fun factor.

So if a PDRA car is running 228% and making just 3400-3600 ish Hp. Where's the missing 1000+ Hp ???? That's what's confusing me?.....

Thanks

 

Some of the other things will be Oil and Fuel pump, Magneto.

I imagine there all taking quite a lot of power to turn at rpm.

Grant

 

The best C rotor to date I have ran is just shy of 3500Hp. The best D rotor to date is shy of 3100Hp

88mm Turbo 481x just shy of 3500 hp

Darren

 

Thanks Mike. I already subtracted a pessimistic 500 Hp from the crank, above, to drive the screw. Still over a 1000 Hp left unaccounted for after that. The real screw draw is likely less, but I had to make a guess of some sort......

Thanks Grant. It just seems weird to me that according to the numbers there's over 1000 Hp left unaccounted for. I agree that it takes power from the crank to overcome friction, windage, pumping losses, accessories, etc., but 1000 Hp worth or more? That's where I get a bit confused when I start to think about the numbers........

Thanks Darren. You certainly would have seen some cool motors at your place. Appreciate your input!......


So Lindberg recently ran down around 5.36 and 272 at 2275# in his funny car with a D. Would that imply that he's got to be about 3400-3500'ish with a D do you figure?


I'm beginning to wonder whether there is a shortfall in the VE of the screw (ie: it just doesn't breathe as well as I am told.....), or whether there is just a ton of energy being lost to waste (which makes me wonder where it is going......).


TOL

 

Puuling power to get rolling?

I know most guys pull quite a bit of power to get things rolling, or some magic stuff happens in clutch world for a bit of time .... maybe that has something to do with the loss???

 

Good conservative numbers.

 

These numbers will seem conservative to a water brake dyno operator. I have had a customer make 2810 hp on a Superflow. He wanted to run on an inertia dyno also, for whatever reason. The result here was 2340hp. When he talks to his friends at the bar he made 2800. At the race track the score board shows 2300. Really doesn't matter in the big picture. Peak power is only part of the equation.

 

I have experienced this first hand with our engines, water brake vs inertia.

I really don't understand it as our acceleration rates were similar and both styles were repeatable.

Can you shed some light on what makes them different readings?

 

Darren; probably one of the best statements ever posted in this forum!
Say hello to Carlo for me, next time you talk to him.





Bob Meyer
Meyer Race Cars / San Diego
2015 Our 50th Anniversary

 

Another thing to ponder... How much fuel is blown trough the engine during overlap? This could figure into the missing HP.

 

For a thumbnail I'd estimate a C rotor as follows...

476CI per rev, 20,000RPM = 5509CI per min
5509 / 14.4 = 382lbs of air per min
382lbs - 38lbs loss to move the air = 344lbs
344lbs x 10hp per = 3440HP

I'm unaware of the adiabatic or volumetric efficiency of the PSI units, or the pressure ratio for that matter... but just based on displacement and RPM info I've seen it seems 34-3500HP is a reasonable guess.

 

The water brake simulates acceleration. The inertia brake measures it. Think what is happening when the water brake control is keeping the motor at the programed sweep rate.

Both dynos are good. Because acceleration is my sport of choice, the inertia dyno was the best fit for my needs.



Enjoy

 

I dont doubt the blower can pump 4000+ hp of air but can the engine use ALL of that to make power? At 225 overdrive and 100% VE the boost should be around 46 psi on a 520 ci Engine. 476x2,25=1071. (1071/260)-1=3,11. 3,11x14,7=46. A number above 50 on the boost gauge tells me the engine doesnt swallows it all.

 

Exactly.......

Turbo's are air density modifiers and they have no backflow prevention. The motor below is the volume metering device in that case. Screws on the other hand are volume metering devices themselves, and they DO have inherent backflow prevention due to the internal compression within the case (within certain pressure ratio ranges.....).

In the case of a screw on a motor, what goes in (air mass....) is pretty much what goes out, just in a different state. The screw pretty much does not care about the motor below. The screw is the metering device and the motor will just constipate the screw to some degree more or less based upon the size and volumetric efficiency of the motor.

My question (the one which started this thread.....) is if a screw allegedly has a linear or positive curve-linear VE relationship with respect to shaft speed, then why is that the net measured output of the motor is much lower than what one would expect from running the anticipated air mass versus power calculations even after subtracting the power to run the screw from the crank?

Where's the missing power? Is it lost in the breathing (VE...) of the screw, as in the screw is not breathing as well as we are being told? Or, is it lost after the screw, as in there are huge losses (mechanical or thermodynamic....) that are not being accounted for by the equations? Something just seems 'screwed up to me.

I'm looking forward to instrumenting mine. Now I am really curious why the big difference between calculated and actual output.