Loss Of Power At Higher Revs.

Loss Of Power At Higher Revs.

Author
Discussion

BLUETHUNDER

Original Poster:

7,881 posts

259 months

Sunday 26th January 2003
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Whilst out yesterday,i came across an RS escort turbo spoiling for a fight.Not wanting to dissapoint him i obliged.I would like to add that the conditions were safe.A long dual carrigeway and an all out blast and round one went easily to me,reducing him to a mere spec in my rear view mirror.With round two approaching(around the roundabout and back up the otherside of the dual carrigeway)i decided to give him an advantage and let him take the lead.With him now in front,i push on the power 2nd gear 5500 rpm and the car suddenly starts to jerk and looses power,change up to third and problem gone,push up to 6000rpm in third and problem appears again.subsequently i loose round 2,and hes off to tell his mates how he thrashed a tvr.I think my problem is electrical,i.e a lead breakind down.But as i have had these changed 8 months ago,could they be at fault once again.Any help would be more than appreciated. MARK

chris watton

22,477 posts

259 months

Sunday 26th January 2003
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mark,
I get exactly the same symptoms with my Chim 450 at times! Sometimes it's fine, but other times my car acts in a way you describe to a tee! It's like it runs out of puff too early and can't go any faster in that gear, till you change up then all's fine, untill you hit the 5000+ mark!!
I intend getting mine checked out on a rolling road and see if there is something amiss.
Strange thing is that it doesn't do it all the time!!!

chris

BLUETHUNDER

Original Poster:

7,881 posts

259 months

Sunday 26th January 2003
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Chris mine only seems to do it when the car is really warmed up.Im hoping it is the leads as i have heard tvrs eat leads constantly with all that heat under the bonnet.

amayson

35 posts

255 months

Sunday 26th January 2003
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You sure this isn't just the rev limiter kicking in?

BLUETHUNDER

Original Poster:

7,881 posts

259 months

Sunday 26th January 2003
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amayson said: You sure this isn't just the rev limiter kicking in?
Not knowing how the rev limiter would act,i wouldnt have thought it would have acted in a violent manner like it did.Does any one know how the rev limiter acts.

chris watton

22,477 posts

259 months

Sunday 26th January 2003
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Am positive it's not the rev limiter. Sometimes I can rev to just beyond 6000 revs no problem, but other times, I just don't seem to have any more power in that gear past 5000!! very strange!
I have cleaned the stepper motor, but I haven't opened the throttle up enough to check yet.
I would change the plugs and leads just to be sure, but the plugs seem very hard to get to, and I don't want to break one when trying to contort myself getting the plugs out! Is there an easy way of doing this??

Chris

amayson

35 posts

255 months

Sunday 26th January 2003
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It sounds like the rev limiter to me. Mine felt like hitting a wall the only time it's ever kicked in! Here's a typical link on the subject.
www.pistonheads.com/gassing/topic.asp?f=13&h=&t=25046

ABBTVR

68,798 posts

257 months

Sunday 26th January 2003
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amayson said: It sounds like the rev limiter to me. Mine felt like hitting a wall the only time it's ever kicked in! Here's a typical link on the subject.
www.pistonheads.com/gassing/topic.asp?f=13&h=&t=25046


Certainly sounds like the rev "brickwall2 I hit a couple of times,
FWIW Found a cure that suits me, hit the loud pedal harder and change quicker.

Big Al.

BLUETHUNDER

Original Poster:

7,881 posts

259 months

Sunday 26th January 2003
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But can anyone tell me how the rev limiter acts,because on my first round with the RS i exceded 6200 rpm in 2nd gear and had no problems.It was only on my second run in 2nd gear at 5500 that my problems started.If there is a limiter why then didnt it cut in at 6200rpm instead of 5500.?

STEVE_HALL99

23 posts

263 months

Sunday 26th January 2003
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Blue, I'm surprised you needed all the revs to take an RS Muppetmobile! I had a weird bespoilered V6 Probe have a dig today and absolutely destroyed him using just over 5K rpm change up's... Anyway, how does the revcounter re-act? Basically you hit 6k rpm and hit a brick wall...

BLUETHUNDER

Original Poster:

7,881 posts

259 months

Sunday 26th January 2003
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It wasnt a standard RS by the sounds of it,it was well tuned and had a serious sounding dump valve fitted.I caned him on the first round,but was a bit embarrased on the second with this problem.

dannyboyo

2,388 posts

278 months

Sunday 26th January 2003
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Doesn't the rev limiter kick in about 6000rpm on a Chimaera. Not sure what system it uses, but most rev limiters work by centricfugal (spelt wrong!) force on the rotor arm, so at certain revs the rotor arm stops supplying sparks to the cylinders. This does have a pretty dramatic effect (the same as turning your engine off!!)

But maybe on TVR's it's governed by the ECU which i would imagine would have a softer effect. I'm sure Steve (Mr.bible) or another clued up bod will fill us in!!

>> Edited by dannyboyo on Sunday 26th January 23:40

greenv8s

30,149 posts

283 months

Monday 27th January 2003
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dannyboyo said: Doesn't the rev limiter kick in about 6000rpm on a Chimaera. Not sure what system it uses, but most rev limiters work by centricfugal (spelt wrong!) force on the rotor arm, so at certain revs the rotor arm stops supplying sparks to the cylinders. This does have a pretty dramatic effect (the same as turning your engine off!!)

But maybe on TVR's it's governed by the ECU which i would imagine would have a softer effect. I'm sure Steve (Mr.bible) or another clued up bod will fill us in!!

>> Edited by dannyboyo on Sunday 26th January 23:40



Rev limiter will be pretty violent, but it will also be consistent between gears - it won't let you pll up past 6k one time and then cut in at 5500 another time. I suspect you have some other problem here, but there are so many possible causes that you may be best taking it on a rolling road to track it down. It's also worth noting that these engines don't like being revved hard, and if you have a standard engine your optimal change-up point will be below 6k rpm. And the last few hundred rpm really make very little difference, so 5k5 is a pretty reasonable shift point even if you're trying to make a point.

Cheers,
Peter Humphries (and a green V8S)

royalexander

43 posts

258 months

Monday 27th January 2003
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Mark,

This seems a common problem and I experienced same not long after purchasing a 450. Also from looking around the Forum others appear to have simlar issues.
List of possibles common ones I have come up with (I am sure there are more).
1) Leads
2) Coil (check for oil leaking from top)
3) Distributer Cap.
4) Rotor Arm
5) Stepper Motor needs cleaning.
6) Vacume advance loose.
7) Fuel Filter needs cleaning (this was done last service but failed to fix problem).

Out of interest I found that the vacume advance was loose on mine tightend it up and problem went away for a couple of weekends came back once and has been running ok for the past 6 weeks without a problem.

My money would be on the coil, where it is located it must be cooked and as it heats up I am guesssing the insulation is breaking down somewhere.

Problem is as it is so intermitent it's a B&*$££ to know when it is fixed.

Regards,

Roy.

incorrigible

13,668 posts

260 months

Monday 27th January 2003
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You mention a roundabout, I can induce fuel starvation on heavy cornering with less than 1/4 of a tank (which is weird) at least that 's what I've put it down to because I've done the same corners repeatedly with different fuel loads and low fuel makes a difference

Also when I'm down to the last few litres (like on the M3 in convoy yesterday) when I put my foot down there was a little hessitation, filled up and all was well

headlights

21 posts

257 months

Sunday 2nd February 2003
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I’m sure a read somewhere that the fuelling map in the ECU is only programmed to 5500 r.p.m above that the engine can start to ‘gag’. The rev limiter is also controlled by the ECU, as an ignition based one would allow unburnt fuel to get to the cats, which isn’t recommended. I have a 5lt Chimaera, which pulls like a train to 5,500 and then power drops off up to 6,000 when the rev limiter cuts in. You can get your ECU reprogrammed to continue fuelling correctly at higher rpms. Tower View are probably the people to talk to. Good Luck.
P.S I had a good drag with a viper a while back, it was close but I lost my bottle at 5,500rpm in fourth!

BLUETHUNDER

Original Poster:

7,881 posts

259 months

Sunday 2nd February 2003
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Headlights. you say the power falls off, but in what way.mine when it gets to 5500rpm feels like its having an electrical breakdown.

JamieBeeston

9,294 posts

264 months

Sunday 2nd March 2003
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www.vsupermarket.co.uk/act/Image4.jpg


Above graph shows my 450 before and after some engine / exhaust work by Mr 2Sheds..

You can see before, it virtually stops at 5500, but with the better breathing and exit... it gets thru th around 6000 before dieing a death.

Check the healthy Torque gain all over too

This was AFTER a tornado chip.

Details here

www.pistonheads.com/gassing/topic.asp?f=8&h=&t=23948

>> Edited by JamieBeeston on Sunday 2nd March 13:22