Engine power, speed, etc

[944Turbo]

ORIGINAL: TTM Well... I would say building a gearbox to reach such a "politically incorrect" speed on a 944 turbo probably doesn't stay within the financial realms of the usual owner. And I didn't say I was going to try this on the public road anyway (too dangerous for other users), thankfully we have some decent airfields here too. (I modified the title of the thread, I hope it's doesn't read as "politically incorrect" as the first one) Back on topic now, the S2 5th remains too short I'm afraid, I'm not sure it is worth it. Did you monitor speed with Satnav? The speedo is highly erratic...

Thought it was the n/a 5th gives you about 200mph at reasonable revs in a turbo box - some details here http://944hybrids.forumotion.com/t1190p30-5th-gear-options-audi and the V8 conversion manual does show it as a relatively straight forward swap, Tony

 

[333pg333]

ORIGINAL: Hilux

ORIGINAL: TTM Paul, good point. The graph for the Veyron is as follow, with its particular Cx, frontal area and weight. It's still quite in line with official figures, isn't it?! []

Thats the sort of curve I would expect (very well described by George as diminishing return) []

I would have expected a curve flattening off a lot more than that even with a 3L motor?

 

[mik_ok]

Aerodynamic drag (which will be the dominant factor at high speed) varies with the square of speed, (Drag = 0.5 x CdA x speed squared x air density). Power requirement varies with the drag (Power Required = Speed x drag) Therefore - Power required varies with the cube of speed. It's pretty easy to estimate power requirement if a known top speed already exists.... Example numbers :- If a 944 can do 155mph on 250bhp 186mph target speed = 20% higher than original top speed (ie. 1.2 x original top speed). This ratio cubed = 1.2 x 1.2 x 1.2 = 1.73 Power requirement for 186mph = 432bhp (ie 1.73 x 250 bhp) To do a Veyron-esque 254mph (with appropriate gearing of course) the ratio of speed increase is 1.64. This cubed is 4.4 ~ so you'd need around 1100bhp. Easy enough to make a model in excel, but then you start messing about for no good reason to answer questions that weren't asked.... - The Macca F1 would be able to match the Veyron VMax with only 750-odd bhp. (Shows how slippery and small-frontal-area the F1 is). - A Macca F1 with Veyron power levels would be able to do over 280mph. etc etc [&:]