Top Speed Estimate?

[Oiluj]

Question for the site's pundits.

The thread about tickets got me thinking. Just how fast is my non-stock Z? I'll never actually find out firsthand.

Car specs:

1972 240Z

Rebello 2.7 liter upgrade & stage3 cam: 212 hp @ 197 ft-lbs torque

Stock 4 speed & diff.

BRE style front & rear spoilers

Lowered 1/2 " w/ eibach springs and tokico blues.

All new wheel bearings & brakes, tranny & diff flushed and refilled with MT90.

I expect it will do better than the stock 124 mph top speed. Question is, how much faster? 130? -135? - ??

Any racers / Z gurus willing to make an educated guess-timate?

[Zs-ondabrain]

Final drive? What's your diffs gear ratio? The Robello motor should allow you to keep up the power that is normally lost at those speeds.

I'll throw a wild guess at it and say about 140, +/- 5mph

But a lower gear ratio of say 3:90 versus 3:50? or similar will mean the Difference between 130 and 145. The 4-speed versus the 79' 5-speed will also make a difference. There's a top speed Link somewhere on this site or another.

See if this works for you. my computer won't allow it.

http://webspace.webring.com/people/cz/z_design_studio/transmission_300zx_tt.html

[sblake01]

Dave, I believe you meant to post this link:

http://webspace.webring.com/people/cz/z_design_studio/transmission.html

The one you posted if for a 300ZX Twin Turbo.

[Oiluj]

Cool. 140 mph is about what I thought it would be, but so much depends on other factors, that I wasn't sure.

It's got the stock tranny & diff. Final drive ratio is 1.0 w/ the stock 180 diff.

_(I've got a 280Z 5-speed I need to rebuild and install that will raise the final drive ratio to 0.864).

Thanks for the link. According to the calculator, it looks like 144 mph at 6300 rpm. With my 5 speed, it indicates 160 mph, but I doubt it will have enough power to reach that rpm in 5th.

It found it climbs to 90 quite fast, which is quick enough for me...

[jmortensen]

I posted a formula for estimating this from Race Car Aerodynamics. Using the formula it looks like you could expect 146.5 mph, that's estimating drag at .45 and frontal area at 22 ft^2 . As you said, in reality gearing is more important than what the potential is for redline in 5th. To me it looks like you could get pretty close to the estimate in 4th, 5th is just there for saving gas in your case.

[Zs-ondabrain]

So I guestimated pretty damn close then.

I was on the Datsun Z link but I'm not sure how I posted the 300ZX link? Weird. But either way, my computer won't allow it to run cause it's unlicensed or something. Can't verify the publisher or some crap.

At least I'm a good guesser.

Dave