Cheburator

Car is completely stock - the heads have been skimmed in a previous top end rebuilt, but not enough to raise the compression or anything such like. The car runs on 255/40/17 on genuine Cup 1s... That was on a run in Germany between Cologne and Bonn...

The speedo over-reads by about 7 to 10mph so I guess the real speed was more like 290km/h...

Brett928S2

Hi

Ummm..S2 s come with 16 inch wheels as stock...NOT 17...which means unless you keep same rolling radius..top speed will be affected..one way or the other...

All the best Brett

928 S2 AUTO V8 4.7 LTR 1986 IRIS METALLIC BLUE WITH X-PIPES ,RMB ,PROMAX CHIPS, KICKDOWN SWITCH.K&N.NITROUS KIT 150 HP.
PCGB UK 928 FORUM MODERATOR - Email managingdirector@pchealthcare.co.uk

928ntslow

Seems to me, the best combination for top speed, is an S4/GT body, a GTS engine with a 6500rpm redline, post 87 5 speed transmission (as the auto's will "slush out" eventually and lose an mph or two) fit to a 2.20 final drive. Barring removal of all the little doo dads to increase aerodynamics, as well as adding spoilers and such, the next best thing is to add taller tires keeping width to no more than 9", preferably 8".

Just using these STOCK components should get a 928 close to 200mph....wouldn't you think?

Ketchmi

With proper aerodynamics it will take approx. 400-430rwhp (460-500 crank hp) to hit 200mph. A very well built GTS engine will not make that much without some additional help.

928ntslow

Sounds like there is a point when one hits an atmospheric brick wall then. Good to know!

whitefox

So why is it Cherburator's S2 can hit ~180 mph but needs almost 200 more horsepower to get 20 more mph?

Ketchmi

If you notice, he is just shy of fuel shutoff. He cannot go any faster at that point regardless of horsepower or aerodynamics. I would be tempted to say that speed was attained on a long, possibly slight downhill with a tail wind. 928 speedometers are pretty linear with respect to their amount that they are off. My 86.5 did 163 on GPS but the speedo was pegged. A friend hit 195mph in his mostly stock 87' on GPS but it did involve a loooong downhill. Let me rephrase...in a straight line, level, with no wind it will take 400-430 rwhp to attain 200mph. Speed is not linear with horsepower. It takes considerably more horsepower to do 200 than it does 180 (or 165-170ish in this case).

heinrich

Fuel cutoff is apparently 6500RPM in my '87 5spd. I found it yesterday the first time in many years.

Tahoe Shark

Dave,

Is your calculation of 400-430 hp for sea level or at altitude. It seems that where we are running at 6,000 - 7,000 ft it would take a bit more HP to get to 200mph. Pulling a 2:20 at 7,000 ft takes a lot of HP. I know my GTS (320 rwhp) runs out of steam much over 6,000 rpm's and you are right 180 mph is a long long way from 200 mph.

I think the Beast will solve the HP and aero problems.

Ketchmi

Actually Tim, 400-430 rwhp uncorrected is what it takes. If corrected for altitude, you would need 18 to 21% more than sea level numbers. (475-520 rwhp at sea level!) ((roughly 3% loss per 1000' altitude)).

I can't wait to see "The Beast"! I have no doubt it will break 200mph and do it in pure style. Are you going to have the A/C on during the run?

Tahoe Shark

Thats what I thought about the corrected HP figures to go 200 mph @ altitude.

Alas we will not be using the A/C in Open Road anymore because the Beast has other parts where the A/C used to reside. Now we will just have to drive with no A/C like the Corvettes, Vipers and all the rest. I let Bill & Richard take over the Air Conditioning duties.

I know your car is layed up, but why don't you come out to Wendover and cheer on the 928's. Isn't it only 150 miles or so. Maybe even a day trip. Lunch is on me.

Ketchmi

I should get the GT out and stretch it's legs...

My 86.5' should be back on the road in July and will be much prettier than it was. (I hope that makes it faster!)

I may take you up on that lunch.

Vilhuer

http://www.miata.net/garage/tirecalc.html

I have heard stories of one particulary fast ROW '83 S. According to owner it also went very close to 300 km/h on autobahn years ago.

James-man

In response to original question, 130 and legally.

sweanders

Uhm, what?

Look at pretty much any car and it has the same marking since 50 km/h is a base speed throughout Europe..