So does anybody here have the software that calculates how much HP is needed to make a certain speed?
We are getting serious about making a run at a record for a class on the Bonneville Salt Flats.

with a rear end of 2.73 and 15 inch tires we could make the record by achieving 6000 RPM in 5th gear (0.68 ratio).

So the question is how much power do we need to push through the air to achieve the 6000RPM ?

 

Carl, I have a program that is not intended for this, but I am able to configure it to give ball park #'s.

I am assuming you are looking for somewhere around 230 mph based upon your data.... my program shows that a 640 hp @ 6500 rpm motor will pull you to approxmiately 230 mph @ 6000 rpm with a .68 5th gear and 2.73 rear on a 25" radial tire. I reduced the tire to 24.6 based upon weight pressure, which is actually a little less than you're supposed to do.....

The above assumes a 3300 lb run weight, C4 corvette aerodynamics, and also assumes sea level track utilizing a .98 atmospheric power ratio.... up in Utah at Bonneville, you would probably need another 10 % power to achieve the same due to the elevation. This also assumes running on pavement.... I have read that the salt lake in itself will knock you down several mph at least vs running on pavement, so you would also need to take that into consideration.

My program showed it took you 59.81 seconds to go from zero to this speed and 15,565 ft.... however, once again, this is on pavement, your acceleration time and distance would both be greater on the salt.... you would probably want to add 5-10 seconds and another 1000 ft or so to achieve the speeds.

My program doesn't show me the minumum power required to achieve your objectives... it only shows based upon the parameters I put into it, thus you may be able to achieve 6000 rpm with a lower hp, but it would obviously take you longer and require additional distance to achieve.

I can run many tests to see if it is possible to pull 6000 rpm in 5th gear with a lower hp.... but its a tedious thing to do.

As a note, my sample motor made 640 hp @ 6500 rpm and 588 ftlbs @ 5000 rpm.

Hope this is kinda a little bit of help.

Good Luck with setting the record !!!

cheers,
Beach Bum

 

Wow.... This sounds exciting! Be sure to keep us posted with future happenings.

Aaron

 

Edit on my post.... I said 14.6" tire.... I meant 24.6" tire, which is I assume you had meant 25" tire instead of 15" tire..... as you know the rim size is irrevelant.

 

A couple of years ago Lingenfelter ran an '88 or something Pontiac F-body (similar aerodynamics and weight) at Bonnyville. That was well written up in the perfomance mags. That might give you some help. Probably you can get it from his website or someone there. The main thing I remember was he shot nitrous directly on the induction for heat control (not in the engine to make power).

Wow, go gettum!

 

For a C4 the equation is roughly:

HP =0.354*(SPEED^3)/8250

Sounds like you're using a different car than you did for the 130 MPH club, do tell more...

What speed? 15 inch diameter tires, what lawn mower did you steal that from??

 

Yup - I messed up the tire size - You guys know I don't know what I'm talking about. The tires are mounted on 15 inch rims - but are tall and thin - Z rated, Using the formula I come up with a tire that is 27.9 tall - so we overinflate figure 28inch tall tire.

It looks like we will be using the C-3 to try for the record (More than likely we are just looking to get into the 200 mph club). The C-4 is being fitted with a new tremek 5 speed and a ZZ4 this spring - and will be used to put people in the 150 MPH club.

Sothe C-4 will be putting out about 350 HP. gear ratios will be either 1.0 or 0.68 overdrive - rear end will be 3.07. Will we be able to make 150 in 2 miles?

While the C-3 will be putting out 455 HP with 1.0 or 0.68 OD and a 2.73 rear end over 3 miles

Anyone want to take a shot at predicting either speed?

 

Actually I completely messed up tire size - in actuality the tire is 28inches tall!

 

Thin, is good on the salt. You may have less horsepower when you get here, then you counted on. The altitude is approx 4200 feet. You won't see 26" on the uncorrected barometer. The temps vary as to the time of year, of course. The humidity is generally fairly low. On a hot day, 30% is absolutely muggy. I'm looking at a log book from late September. You won't be running after sundown. During the daytime, over two days, the temps for my runs were from 71.1* to 86.5*. The DAs ranged from 6146' to 7167'. Forewarned is... Wave as you go by.

RACE ON!!!

 

are those horsepower numbers RWHP or Wishfull-ThinkingHP (Crank HP)?

If we're talking CHP the C3 probably won't make 200.

Those gear ratios are putting you in a tough spot, with 28 inch diameter tires you'll need to be at 4400 rpm in OD to reach 200 mph, which will require over 350 HP for wind resistance alone. You may want to think about investing in taller tires for the back, you're cutting it too close.

I don't think you'll have too much trouble hitting 150 with your C4, assuming you're still doing a 3 mile run. If you're back to 1 mile runs, I'll wait to see a dyno graph before I go making any predictions.

You could always run with a 300 shot of Nitrous, you'd break 150 with a boom! (or, um, break 150 then go boom! )

 

Well we know that crank HP is 458. (we are looking at 1 more mod that could take us to 485 HP (crank) I know you loose some to the drive train - if you are running a manual trans could you expect to loose? 10%?

will look into taller tires - but you really don't want to lift the body to do that - for aerodynamics - right?
As far as gear ratios you would have the option of running in 4th - which would be 1:1 - would that help?

Well the 150 MPH run is 2 miles to get up to speed - then 1/4 mile timed - I'm thinking we should be able to make the C-4 go 150.

Ah - we don't believe in Nitrous - I mean we know it works - but it is contrary to our philiosophy - we drive what we race on a daily basis - we even drive em to the race - and we expect em to last and perform very well for a long time. Nitrous just doesn't feel right!