Terryathome Posted August 17, 2013 Share Posted August 17, 2013 Reading this web page http://www.maddoldb*******.supanet.com/gearbox.html about changing the 5th gear cog in MT75 gearbox and quote "This would change the ratio in 5th to reduce the engine revs at 70mph from 3039rpm down to 2746rpm, enough to give better economy at this speed and reduce engine noise. But if allowed to run flat out, would give a top speed of 178mph@7000rpm in place of the old top speed of 161mph@7000rpm. if you had the power and could rev to 8000 rpm you could get 204mph" So what you had out of you streamed lined brick, top speed that is? Whos the brave ones to admit to the above? Terry Quote Link to comment Share on other sites More sharing options...
Norman Verona Posted August 17, 2013 Share Posted August 17, 2013 I was measured at 150.6 on the runway at Brize Norton. However I've since fitted a 4.44 diff so it's now about 135. Quote Link to comment Share on other sites More sharing options...
User0083 Posted August 17, 2013 Share Posted August 17, 2013 I've done 120-130... Still a few revs last. But at those speeds I wasn't looking at speedo/revs much. It was on a disused runway and had a few potholes/grass on it. Can't remember exact figures, but on a dyno the guy said I was doing 80 at 3500rpm, so 160 at 7000rpm. I know this isn't massively relevant, as aerodynamics would destroy these figures and figures not accurate from memory! I just remember thinking "wow!!! I can do 160 in mine!!!" Then thought... "Hmm... Nah, aerodynamics!" Quote Link to comment Share on other sites More sharing options...
davidgh Posted August 17, 2013 Share Posted August 17, 2013 Fastest I've ever seen through a speed trap (Aintree) in my 1600VX (nearly bog standard you understand ) SEi is 126mph. Also, I don't think Tommo's/Kurt's "Flymo" has ever been clocked at over 150. Theoretically (in simple terms), aerodynamic drag is proportional to the drag factor (shape related), the frontal area, and the velocity squared. Terminal velocity is when the power available and the drag are equal. Se7ens tend to have very poor drag factors . The square relationship to velocity means that (theoretically) my 215bhp Westy would need over 300bhp (without being bigger) to achieve 150mph and almost 400bhp (without being bigger) to achieve 170mph. And that ignores all other kinds of drag (tyre friction, etc.). Net, net, any normal Se7en which is geared for more than 150mph tends to be more about bragging rights in the pub than practicality. Quote Link to comment Share on other sites More sharing options...
Wile E. Coyote Posted August 17, 2013 Share Posted August 17, 2013 Net, net, any normal Se7en which is geared for more than 150mph tends to be more about bragging rights in the pub than practicality. Or more relaxed cruising in top? In theory mine is geared for 150+, but remains relatively civilised at 70. Front end seems to gets interesting at ~130, but not a tremendous problem as there aren't that many places to wind it up to that. Quote Link to comment Share on other sites More sharing options...
Norman Verona Posted August 17, 2013 Share Posted August 17, 2013 David, I've never bragged about this. Removing the screen helps a lot and fitting the 5.75" headlights also helps. The BBC (Brize Norton Bike Club) did the speed checks at the end of the runway. There were two Westfields there on the day that were a lot faster on the standing 1/4 mile. Not sure if they did the maximum speed run. I did have a high ratio diff and a high 5th ratio at the time. Quote Link to comment Share on other sites More sharing options...
alexander72 Posted August 17, 2013 Share Posted August 17, 2013 I think ive managed about 80 in mine Quote Link to comment Share on other sites More sharing options...
dombanks Posted August 17, 2013 Share Posted August 17, 2013 flat out foot to the floor in 5th i was doing about just under 130 but mines a type 9 not a mt75. i know my speedo is about 3mph fast at 90 as ive had one of those sat nav speed things in the car with me before. i find mind is really comfy at motorway speeds Quote Link to comment Share on other sites More sharing options...
AidanPlace Posted August 17, 2013 Share Posted August 17, 2013 70, never more Quote Link to comment Share on other sites More sharing options...
Hammy Posted August 17, 2013 Share Posted August 17, 2013 Caterham claim 155 mph with 310 bhp for their car. I expect this is on a good day, but gives you idea of the power required to pass 150mph ins seven . More aerodynamic cars can get to this sort of speed with a lot less power ( my VX 220 does 150 on 200bhp, E type Jag on about 260?) This lines up well with Mr Hussey's numbers . I did draw a graph on the derby & notts page on Facebook, from published power /top speed figures, which is instructive in response. Done in response to another post on here where someone wanted to do 170mph ( probably not possible !!) You'd also need to get the gearing spot on to archive your max top speed - a car geared for 170 is unlikely to achieve 150 ( ignoring aerodynamics for a moment ) as its probably not at peak power at 150mph. Really a Westfield is not for going fast in ! Quote Link to comment Share on other sites More sharing options...
minesapint Posted August 17, 2013 Share Posted August 17, 2013 Only been up 95-100 in mine, everything rattling & shaking, eyes streaming, seat belt ends slapping me in the face, hair follicles being pulled out, all was blurred, sounded as though my ears were 12" away from the exhaust of an RB211 Trent, frightened the brown stuff out of me, don't know how you guys are talking about 150!! Cheers 1 Quote Link to comment Share on other sites More sharing options...
Boney Posted August 18, 2013 Share Posted August 18, 2013 Owdo was at 130 on back straight of Bruntingthorpe last week with a few revs left as just cant bring myself to sit their on rev limit in fifth, but when you are being past by MP4-12C's and gallardo's as if your are standing still you realise your car is not built for top speed Boney Quote Link to comment Share on other sites More sharing options...
Norman Verona Posted August 18, 2013 Share Posted August 18, 2013 I think the runway at Brize Norton is a mile and a half long. Long enough to get every bit out of an engine which is limited to 9000 rpm. ed to add that I calculated the top speed on THIS 9000 rpm .86 4.44 15" 210.4 MPH. So 60 mph below due to aerodynamics seems OK, if a lot. Quote Link to comment Share on other sites More sharing options...
Steve_Farrimond Posted August 18, 2013 Share Posted August 18, 2013 mine hits the rev limiter at 6800rpm @ 135mph Quote Link to comment Share on other sites More sharing options...
SteveD Posted August 18, 2013 Share Posted August 18, 2013 wheres del when you need him , aintree speed trap Quote Link to comment Share on other sites More sharing options...
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