Thrashing noise at 5500 RPM

[peebee]

Took the Chim out today and pushed it for the first time. Found that when the revs got to 5500 there was a sudden thrashing noise - as though I had chrunched the gearbox (I hadn't touched the gear lever at this stage but soon did to put it out of its misery).

I see the max revs are listed in the Bible as 6250rpm. The noise was not a progressive increase - it came on suddenly at around 5500. Happened a second time but then I decided best to change up at 5000. I appreciate max power is at around 5250 and so no real need to go to 5500 but I'm concered about what this noise might be, or is it normal?

Any thoughts would be appreciated.

[_Deejay_]

peebee said:

Took the Chim out today and pushed it for the first time. Found that when the revs got to 5500 there was a sudden thrashing noise - as though I had chrunched the gearbox (I hadn't touched the gear lever at this stage but soon did to put it out of its misery).

I see the max revs are listed in the Bible as 6250rpm. The noise was not a progressive increase - it came on suddenly at around 5500. Happened a second time but then I decided best to change up at 5000. I appreciate max power is at around 5250 and so no real need to go to 5500 but I'm concered about what this noise might be, or is it normal?

Any thoughts would be appreciated.

My old 4 litre Chimaera used to rev happily beyond that. However, I suspect they'll be different depending on age. Are you sure you didn't hit the limiter?

[peebee]

_Deejay said:

My old 4 litre Chimaera used to rev happily beyond that. However, I suspect they'll be different depending on age. Are you sure you didn't hit the limiter?

I don't think so - I'd think if I did the engine performance would just plateau, but there was a definate unpleasant sound as though I'd crashed the gears (except it came from the engine - so far as I could tell). Also I'd expect the limiter to be set at a higher rpm.

It's a '98 400 by the way.

Edited by peebee on Sunday 15th April 18:14

[Red V8]

Sounds like the rev limiter to me... I remember getting a similar shock first time it happened, thought I'd crunched the motor.

[bigdods]

Could be the limiter which 'should' be set at around 6200 BUT its not unheard of the for tacho to misread. What speed does the tacho show when ticking over ? perhaps take her out for a run and make a note of the revs at say 40, 50 and 70 in 4th or 5th then post back on here and see if some kind soul with a 400 can go out and check/compare for you.

On my 450 its a hard cut limiter and makes some nasty noises if you hit it.

[peebee]

Thanks for your comments. It ticks over around 1000 rpm but I will check at various speeds and post back as suggested.

What does a 'hard cut limiter' mean out of interest? I know I had a Ford a few years back and when I hit the limiter on that the acceleration stopped and the engine sort of died - but no harsh sounds.

[bigdods]

In my case I would describe hard cut as hitting a wall. It wont accelerate any further and makes some nasty noises. ANd it comes on very suddenly. I know there are some Chims out there with softer limiters which gradually reduce power as you pass the redline , but I would assume they also have a replacement ECU. I guess if you are still getting acceleration but just a nasty noise then its not the limiter. Get yourself off to a specialist...

[blitzracing]

The rev limiter value is held in the plugable Eprom in the ECU. Im told on good authority that its not fixed, but depends on what other parameters from the engine the ECU is picking up. The standard Range Rover limit can come in as low as 5500 rpm, but Im sure TVR would have altered the with the cam the engine uses. To check the ECU program, open the cover and look for a chip with a TVR lable like "3.9 cat".(It will be on a socket). The Range Rover / Land Rover chips have a software revision number on them. Have you cosidered something vibrating in the exhaust system ?

[Konrod]

Not sure if this will help, but had to go out in the Tiv (OK, I had other choices, but...........) and can offer the following:

3000rpm 5th gear 98mph
2000rpm 5th gear 64mph
4000rpm 4th gear 90mph

All of these are indicated figures (and were achieved on a rolling road, officer ) Sorry couldn't get slower figures on account of the weather and good (rolling) roads

Car is a '95 Chim 400 with the finned diff (BTR???) and standard wheels. Rev limiter cut in above 6000 (not sure exactly whyat though, my eyes were elsewhere

J

[peebee]

Blitz' I don't think it was coming from the exhaust. I'm reluctant to go over 5250 because of the frightening noise! I've got it booked in for a 12000 mile service at Racing Green and will ask their opinion.

Thanks J. I'll check the accuracy of the rev counter later on the rolling road in the garden. What happened when you hit the limiter - were there any strange noises?

Thanks for your comments.

Edited by peebee on Monday 16th April 14:24

[konrod]

Hi Peebee

No nasty noises, just no power and vibration as the ignition was cut and then restored by the limiter. There was a strange fluttering sound, but that was my a$$ehole when I saw what looked like plod coming the other way as I had it "moving fluidly" ........fortunately it was an ambulance

[rev-erend]

It very much depends on what the source of the noise is.

Most Rv8's have hydraulic lifters and the noise of the engine does change - somewhere around 5500 rpm.. and as peak power has generally been reached - it's time to change up.

It could also be your cam has past it;s best..

[HarryW]

Are you sure it not the limiter, its not unknown for the limiter to be set at 5400 on some RV8 TVR's from the factory, particularly early cat cars .

[rev-erend]

Or the famous tune resistor..

[peebee]

I don't think its the limiter because the engine didn't seem to die at all. I did some quick checks today and found at 4000 rpm in fourth I was doing 85 mph rather than the 90 that Konrod had and so it seems if anything my rev counter is showing higher values than Konrod's (ie if I'd gone to 90 it would have shown around 4200 rpm), and so I think if it was showing 5500 when the thrashing started it was probably actually running at less than 5500 rpm (have I got that right?).

If it is the cam and followers what sort of money are we talking to replace with standard items?

[jsr]

I have a 94 400 which loves to be revved! From my data logger, i can confirm the power and torque dont drop away anywhere near as much as other's i've seen, and so i often use over 5500 revs, sometimes up to 6000rpm.

It sounds perfectly happy until it gets around 6000 when it becomes more violent, metallic and harsh. It's not a limiter though as the car will still keep accelerating. I sometimes fear that i don't have a limiter (i've never hit the limiter) and so it is only fear of pistons flying through the bonnet that stops me going above 6k!

[GreenV8S]

[quote=jsr]i often use over 5500 revs, sometimes up to 6000rpm.quote]

Be aware that regular trips to the top end of the rev range won't do your engine any favours, even if you feel that the engine pulls well at those revs.

[jsr]

GreenV8S said:

jsr said:

i often use over 5500 revs, sometimes up to 6000rpm.

Be aware that regular trips to the top end of the rev range won't do your engine any favours, even if you feel that the engine pulls well at those revs.

Yep, well aware of that, thanks GreenV8S

My philosophy is that the car is for driving and if it was really bad for the engine the red line would be at 5000 revs. I take good care of the car, but it's 13 years old, the chassis is showing signs of age, the front has a few stone chips, so might as well make the most of the car. It's a pretty solid engine which doesn't put out that much power given its capacity. And i probably only go above 5500rpm every once every other drive or so.

I would be a lot more restrained if it were a Speed Six engine however

[peebee]

jsr said:

It sounds perfectly happy until it gets around 6000 when it becomes more violent, metallic and harsh.

That sounds like it!

[v8 racing]

Do you know the history on the engine? if it has had a cam change for a softer cam then softer springs may have been fitted so it could be a case of valve bounce or even lifter pump up.