Cerbie 4.5 RR Power Characteristic Question

Cerbie 4.5 RR Power Characteristic Question

Author
Discussion

GerryB

Original Poster:

13 posts

238 months

Friday 8th March 2002
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Do any of you guys know at what revs the 4.5 RR gets maximum HP and torque ? When Cerbie RR was featured in EVO magazine, against the Brabus Merc, the technical specs showed the peak power for the Cerbie was attained at 6000rpm and max torgue at 4500rpm. In comparison, the standard 4.5 it is 6750 and 5500 respectively. I hope this is true, because this could make a hell of a difference acceleration wise.

Thanks in advance.
GerryB.

dannylt

1,906 posts

257 months

Monday 11th March 2002
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Actually, making more power at lower revs would help the acceleration and tractability! As does more torque lower down. Those numbers do seem rather low though - maybe the engine wasn't very happy.

I'm sure you'll hear about it when the first Red Rose engine goes on the dyno...

danny

PS Nobody even knows the power and torque of the RR officially... let alone the actual numbers.

>> Edited by dannylt on Monday 11th March 12:47

GerryB

Original Poster:

13 posts

238 months

Monday 11th March 2002
quotequote all
Danny,

A couple of months ago, after ordering the RR, I spoke to John Ravenscroft and asked him how much more power I'd get with a RR, and he said approximately 20 - 25 BHP more, around 440 - 445 BHP in total. When he quoted this figure, I automatically assumed power from the flywheel and not at the wheels. I'd be interested to know if anybody has got dyno figures for a standard 4.5 or a RR. I'd estimate for a RR, approx. 350 at the wheels taking into account power loss in the gear box, drive shaft, diff and rear axles.

EVO magazine actually quoted 440bhp@6000rpm and 405LB FT@4500rpm. Again I think this is from the flywheel. If this is true, then there should be a noticeable difference against a standard 4.5 which delivers 420bhp@6750 and 380LB FT@5500rpm.

Regards,
Gerry

dannylt

1,906 posts

257 months

Tuesday 12th March 2002
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GerryB, forget all those official numbers for starters. All 4.5's so far on a dyno are between 320 and 350. I haven't seen a dynograph of one with more than 350 - this is corrected to flywheel numbers. 4.2s appear to be around 330 with less variation, though there are a few with quite a bit more.

I've had a decent play in a 4.5RR, and it's definitely noticeably quicker, but only really obvious over 80mph or so, though it was a bit slippery at the time.

danny

thom

2,745 posts

246 months

Tuesday 12th March 2002
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Do I have to understand all the official figures (from all manufacturers) given on Bhp and torque concern measures on the flywheel??

dannylt

1,906 posts

257 months

Tuesday 12th March 2002
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Yes

beaver

935 posts

257 months

Tuesday 12th March 2002
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Extra 25 HP is spot on, if you have a good engine to start with (maybe 370-375) you can just get into the 400 mark. As Danny says, forget 420 to start with...

thom

2,745 posts

246 months

Tuesday 12th March 2002
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quote:

Yes



All right, so the question to be asked is: what cars show the greatest gap between power output measured on the flywheel and power output measured on the wheels?
So Cerberas are nearly 25% "over-estimated"...does anyone has any idea on other car(s)?

tvradict

3,829 posts

247 months

Tuesday 12th March 2002
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Hold on...

Does it really matter???
I mean, so it doesn't quite do what it says on the tin! It hasn't quite got 420 bhp!
Do you not think that 350bhp is enough for todays roads and conditions? Ok, on a track or through MK it may matter, but there is nothing, nothing that even comes close to a Cerb that you are likely to encounter very often popping down the shops!!
If it bothers you that much stick a nitrous injection system on it! And a "Go Baby, GO" button on the Gearstick! Son't forget the arming panel in that wee cubby hole thing under the dash!

And I always thought TVR measured bhp at the Flywheel anyway!

thom

2,745 posts

246 months

Tuesday 12th March 2002
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Relax, tvradict
I didn't mean to criticise anything, I think it could be quite interesting to find out which cars "loose" a lot of power in the transmission.

tvradict

3,829 posts

247 months

Tuesday 12th March 2002
quotequote all
I am relaxed man...



I knwo you weren't criticising anything thom, it wasn't directly directed at you it just bhp worries in genreal!! I could understand if it was a car that was overestimated by 25% and the estimation wsa only 15bhp! But come on, these cars aren't exactly slow! Who cars what the exact bhp is! There Fg fast and thats all that matters!



Peace and Love man

dannylt

1,906 posts

257 months

Wednesday 13th March 2002
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Hang on, nobody was claiming that 350 wasn't enough... we were just talking about what the numbers were. Besides, when you meet a RR Cerbie on the road, you will see that 350 is not enough

tvradict

3,829 posts

247 months

Wednesday 13th March 2002
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Hmmmmmmmmm, maybe I'm taking these threads in the wrong context! It sounds to me, that people get the hump because TVR make optimistic claims on BHP! And it sounds like people are complaining that a car that is sold on the basis of having 440bhp but only has 380!

I wish my car had 380BHP!

No on second thought, If my car had 380 bhp I'd probably crash and burn within an hour!

quote:
Besides, when you meet a RR Cerbie on the road, you will see that 350 is not enough



ToroTVR

73 posts

255 months

Wednesday 13th March 2002
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What gets me though is that if TVR are stating in their literature etc (I will look in my copies for small print or asterixs) that a 4.5 Cerbera engine gives out 420 bhp and it clearly doesn't by the sound of it, then surely there would be a very strong case against TVR by the Trading Standards Authority. With any consumer product there are acceptable tolerance boundaries but 20% out is ludicrous! I have noticed in the many threads that one of the many defences for the perceived unreliability issues of the AJP engines is the fact that they are a "race engine for the road",handbuilt and tuned etc, etc ,If this is the case
then the tolerance on power output should be even tighter. Can you imagine the Williams or Ferrari Formula 1 team claiming their engines give out 800bhp but it could be 600bhp for all they know......NOT likely! Don't get me wrong I LOVE all TVRs especially Cerberas, but at times (if all the comments in the threads have a glimmer of truth in them) I feel that TVR seem to think they are a law unto themselves. They will have no chance selling cars in the US thats for sure!!!!
Andy.

plotloss

67,280 posts

243 months

Wednesday 13th March 2002
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I dont think trading standards could say a thing. Where was that 420bhp measured? Was it at a higher elevation than the UK? So many variables that wont make horsepower a consideration. I cant see it now:

"I dont want this Cerbera because you said its got 420bhp and its actually got 390bhp"

"Does it scare the sh!t out of your Sir?"

"Yes, of course"

"Thanks very much Sir, please call again..."

Matt.

thom

2,745 posts

246 months

Wednesday 13th March 2002
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quote:

They will have no chance selling cars in the US thats for sure!!!!
Andy.



Good, let's keep the right stuff

venom500

2,984 posts

256 months

Wednesday 13th March 2002
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To much power is never enough!!The 550bhp and 600tqe of my Viper GTS never seems enough!!Maybe one the heads have been moded to give 600+ i might be happy......but then again.

dannylt

1,906 posts

257 months

Thursday 14th March 2002
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quote:

I dont think trading standards could say a thing. Where was that 420bhp measured? Was it at a higher elevation than the UK? So many variables that wont make horsepower a consideration. I cant see it now:

"I dont want this Cerbera because you said its got 420bhp and its actually got 390bhp"

"Does it scare the sh!t out of your Sir?"

"Yes, of course"

"Thanks very much Sir, please call again..."

Matt.

Elevation, air pressure, humidity is all taken into account by standard corrections - there are very well defined ways of measuring power. If we had 390, I'm sure nobody would be complaining too much. A missing 80 to 100bhp is a lot though!

AndrewD

7,266 posts

257 months

Thursday 14th March 2002
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Pah, you don't need 420bhp. In fact, 190bhp is more than enough if you are driving a motorised eggbox which actually goes round corners properly

dannylt

1,906 posts

257 months

Thursday 14th March 2002
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quote:

Pah, you don't need 420bhp. In fact, 190bhp is more than enough if you are driving a motorised eggbox which actually goes round corners properly

Yeah - but then you need the power to get down the straight again