Something on the car makes a noise when accelerating in fourth gear...any ideas?

When in 5th gear at 3000rpm, roughly what speed should I be able to do. I think the car needs tuning as it is fine when ticking over but seems quite high in revs when travelling faster....if you see what I mean. (6/00)

1 Does it only make the noise in 4th or always at certain revs/speed.

2 Gearing determines the speed you do at 3000 rpm not the state of tune of the engine. If you stay in the same gear the revs will rise when you go faster. (6/00)

1)Only makes the noise in 4th and I think, although I'm not sure, at certain revs/speed.

2)Yeah....I know that much but surely 3000rpm at 60 is a bit out and maybe tuning would help??? (6/00)

1)Only makes the noise in 4th and I think, although I'm not sure, at certain revs/speed.

What sort of noise and which area of your car does it appear to be coming from? There's a noise which I've been unhappy about on mine which is only really noticeable in 3rd & 4th at about 4000rpm.. It seems to be coming from behind me somewhere - sounds to me like a friction noise as if a belt were rubbing against something - a sort of loud shushing noise. The dealership claims that it's due to air passing over the bottom of a drainage pipe inside the back wheelarch but since it seems not to be speed related but revs related I'm dubious... They're not having it though & I've learned to live with it over the last couple of years.

2)Yeah....I know that much but surely 3000rpm at 60 is a bit out and maybe tuning would help???

I'm not an expert here, but tuning should affect how fast you get to a specific rev speed & how smoothly your engine is running at certain revs/speeds. My car (late mk1 1.6) hits the redline in third at about 80-85ish, in fourth I think 60 would be around 3-4000 revs from memory -- I'm tempted to nip out of work and try it out now though.. ! :) (6/00)

2)Yeah....I know that much but surely 3000rpm at 60 is a bit out and maybe tuning would help???

All the tuning in the world ain't gonna change the gearing - unless you swap cogs in gearbox or differential.

With standard wheels/tyres (14 x 5.5JJ, 185/60R14), 4.3:1 diff reduction ratio, 0.814:1 5th gear (ie original 1.6 MX-5/Roadster spec) - 3000rpm = 58.5 mph.

Anyone interested in one of my famous spreadsheets showing speed in each gear throughout the rev range, table and graph? It's an excel spreadsheet, should work in Excel 97 on. Only for 5 speed gearbox, but I'm sure 6-speeders can derive their own chart from it. (6/00)