Smoooother over 20k rpm?

[SlowRider]

Hi
Had my Chim 4.0 for a couple of months now and love it. Am wondering if this is normal: its smoother over 20k rpm, whatever the gear ..... and then it certainly flies (surpsing how quickly youre at the speed limit!)

At lower revs its not exactly jerky, but a bit 'lumpy'. I dont mind if this is normal, but does it indicate that all is not perfectly well?

Cheers
Jeremy

[zertec]

20,000 rpm is rather a lot of revs.....

[philshort]

20k rpm? Oooer!

I once had a SuperDream Honda motorbike as a courtesy bike while my GSXR750 was serviced. This was redlined at 10k if memory serves, and the red quadrant went up to 13k.

It was totally gutless (only a 250), but I soon discovered that revving beyond 13k actually produced something like a power output. Thankfully I only had it for a couple of days, I'm not sure how it would have survived long term!

PS Normally I have a great deal of mechanical sympathy, but those SuperDreams were revolting and it deserved it!

[q405mb]

Jeremy,

I am no expert, my 450 is fairly smooth, plenty of torque low down. Typical V8 lumpiness at very low revs. (I presume you mean 2000 rpm, not 20 000?)

There are many possible causes for lumpiness at low revs:

Stepper motor
(Possibly?) modified cam
Timing
Ignition system (HT leads, sparks, coil etcetera)
and many more...

My suggestion would be that if it is causing you some distress and you feel it is "not right", compare it to a similar car or get it checked out by a dealer/independant.

I am sure that if you go to an event like Chatsworth this weekend, you will find plenty of experienced guys willing to share an opinion

H

[SlowRider]

ok ok! i posted early this morning. 2k, not 20k rpm!

[pbrettle]

What model do you have? If it is a 5.0 then expect to have it a little rough at the very low end of the rev range (though even this is fairly subjective) while the 4.0 and 4.5 you can expect to be smoothish at low revs. However, dont expect it to be German-smooth at low revs - the engine is in a relatively medium state of tune and as a result sacrifices some of the smoothness and driveability at low speeds.

But, you should try something like Optimax for a couple of tankfulls. Makes a big difference for most (including me) at low speeds - also improves the fuel economy too. If it still isnt much better then take the car to a specailist (either dealer or independant) to have it checked - unlikely to be anything serious, but worth checking out just in case.

Chances are that it is nothing...

Cheers,

Paul