200+ MPH in a C900?

[SwedeSport]

Top speed in a C900 is advertised at about 145 or something like that. I had always wanted to show up at the salt flats or a dry lake bed with a C900 all done up for landspeed attempts. Not that Ill ever get around to building such a beast, but just curious what it would take to get there. Its obvious that 500+ hp would be required to get there, but what to do in terms of gearing? In order to keep it simple, it would have to be based on the stock C900 trans case. I know the limits of a C900 trans start to show up above 200 hp. I think the trans could hold much more in this instance due to the power being introduced to the trans in a smooth, more gradual curve. In road racing, autocross, and rally, the on/off throttle transitions are what is gonna kill the box.

Any thoughts ?

[Jordan]

I think the amount of torque that would be needed to push the car through the air at that speed would still make the gear set short lived, no matter how gradual its application.

[Crazyswede]

for comparison the Bugatti Veyron can do 250 mph and as I recall it has a quad turbo charged W16 for an engine that puts out 1001 hp. It only needs 270 hp to reach 150 mph but needs another 750 to reach 250 mph...it also needs about 4 miles of perfectly straight road...

Veyron:



I suspect that a Saab 900 has more frontal area in its windshield then the entire veyron has. So while 200 may be possible you will likely need in excess of 750 hp to reach it. Consider dumping the stock drive train and going to a front engine rear wheel drive allowing you to run a strong enough gearbox.

http://www.youtube.com/watch?v=jk1t6S737Cs

[Jordan]

The *new* Veyron , the Super Sport just set the record at 267mph. I believe it's something like 1200hp

[Crazyswede]

I bet you could hit 200 mph in a Renault Robin...after all its pointy in the front.

[Jordan]

Reliant Robin.. it's British engineering.

[Crazyswede]

Renault...Reliant....7 letters starting with and R and ending with a T....french vs English..

[hutch]

Theres a guy in finland with a 9-3 that does 190+mph in a standing mile but obviously the 9-3 has better aerodynamics and a much taller gearbox, which he altered to be even taller in 5th so hes able to hit those high speeds, and he still revs past 8000rpm. To do it in a c900 you would probably need a big holset turbo for breathing up in the high rpms, a pretty worked over T5/T7 head, and all sorts of spoilers to keep the car remotely stable at those speeds, I don't know about you but every c900 I've ever been in has been scary around 100mph and frightening anything above that, I can't imagine what sort of terrifying sounds you'd be hearing as you approached 200mph. It would certainly be cool but if I were to pick a car to do it in I would probably choose a 9000 over a c900.

http://www.garaget.org/video/ow3zdxhzaka0

[SwedeSport]

There is a 69 camaro called "big red" that runs open road races out west. He tops out at 228 MPH. He did the 92 mile stretch of highway 318 in 28 minutes. A 69 camaro isn't exactly the most aerodynamic ride either.
I would expect extensive mods to the body and chassis to make it happen. My 86 900 is rock solid at 100 MPH. But 200 is another story. Things like spoilers, and fins are a must, but the panel gaps are critical as well. Shaving anything you can to make it smooth. Maybe even raking the windshield, raking the hatch, chopping the top, and removing the window trim, and possibly even the drip rails. All that is a given.

Enough horsepower is possible in a Saab 4 cylinder. It has been done. The biggest issue is mathematically determining what kind of gearing would make it possible. I would think that with a custom ring and pinion you could get close. But there is probably more to be done internally with the gearsets to push it over the top.

A horsepower figure, and some gear ratio combos are the place to start.

[Jordan]

Here is a formula from the gearset program I made...
rpm = speed / (0.00595 * loaded_tire_radius ) * gearset_ratio * primary_ratio * rp_ratio)

Using the tallest stock components made....

standard 195/55/15..loaded tire radius = 11.75255102
#8 primary (33/24) = 0.7272727272
#big R&P = 5.17
5th gear = direct drive ratio = 1

rpm = 200 / (0.00595 * 11.75255102) * (1 * 0.7272727* 5.17 )

= 10,754rpm

So yeah, you've got some work to do. But check my maths

[squaab99t]

Here is a formula from the gearset program I made...
rpm = speed / (0.00595 * loaded_tire_radius ) * gearset_ratio * primary_ratio * rp_ratio)

Using the tallest stock components made....

standard 195/55/15..loaded tire radius = 11.75255102
#8 primary (33/24) = 0.7272727272
#big R&P = 5.17
5th gear = direct drive ratio = 1

rpm = 200 / (0.00595 * 11.75255102) * (1 * 0.7272727* 5.17 )

= 10,754rpm

So yeah, you've got some work to do. But check my maths

No offense, but your math is freaking me out. You need to label your units. You have inches, miles, minutes and hours? Is the .00595 the conversion factor that gets the units to RPM?

33/24 is 1.375. Is the 33 or the 24 the on the end of the input shaft?
you also need the rolling distance the tire travels in one revolution. Not sure but, the tire may grow in diameter at 200 mph. I might have to grab some paper and pencil

[Luke]

also, you are using the sport and rally 6:31 R&P and that isnt going to help... I think 9:33 is the tallest available.

[Crazyswede]

most of the cars I saw on the salt flats were so tall geared that they had to pushed off the line because 1st gear was too tall. I should clarify....most of the cars built specifically for running on the salt flats were so tall in the gearing that first was useless until about 10 or 15 mph.

[SwedeSport]

Assuming 500 HP, and the tallest gearing obtainable , what speed could be reached? If there is a group of guys that could figure this out, its here on this forum.

I would think you could run taller wheels and tires to effectively alter your final drive. What about custom primary gear/chain set?

[Jordan]

Here is a formula from the gearset program I made...
rpm = speed / (0.00595 * loaded_tire_radius ) * gearset_ratio * primary_ratio * rp_ratio)

Using the tallest stock components made....

standard 195/55/15..loaded tire radius = 11.75255102
#8 primary (33/24) = 0.7272727272
#big R&P = 5.17
5th gear = direct drive ratio = 1

rpm = 200 / (0.00595 * 11.75255102) * (1 * 0.7272727* 5.17 )

= 10,754rpm

So yeah, you've got some work to do. But check my maths

No offense, but your math is freaking me out. You need to label your units. You have inches, miles, minutes and hours? Is the .00595 the conversion factor that gets the units to RPM?

33/24 is 1.375. Is the 33 or the 24 the on the end of the input shaft?
you also need the rolling distance the tire travels in one revolution. Not sure but, the tire may grow in diameter at 200 mph. I might have to grab some paper and pencil

It was late and I'm no smart..... but it was a start Yeah I fast forwarded on the .00595 to convert the units... I would have to go back and see where I got that from. I could try again but nobody wants to see that. My point that I failed miserably to make is that the math shouldn't be too hard to figure out. There are probably many calculators on the web that could give you a rough estimate if you really wanted to go that route.

edit: you could also try this http://www.wallaceracing.com/gear-speed.php
and put in the R&P gear as the rear gear and primary as the Transmission gear..should work?