Power Output

[Alex Gurr]

I was thinking of putting my new toy on the rollers to see how the engine is performing. It is a totally standard 1997 500 for which TVR claimed 320bhp, although I am assuming that this figure is optamistic

So, what sort of bhp should a healthy engine be putting out? Has anyone got any experience of rolling road results?

Also, does anyone have a recommendation for a reputable (accurate) rolling road facility in and around Hertfordshire?

[virgil]

Had mine done early this year - std 500.

Was told they average 260 for a reasonable one...mine was spot on.

[Alex Gurr]

Blimey - 320bhp is quite some exageration from the factory then

[RichardD]

Weren't the earlier ones supposed to be 340bhp not 320bhp anyway? I had a RR graph last year and my engines performance was totally consistent with a 340bhp engine from 1000 rpm to 4500 rpm. At this point it was like the engine was strangled, as it gained 3bhp from 4500 rpm to 5000 rpm (peak power) and then lost another 3 bhp from 5000 to 5500rpm. So that was 280 bhp at 4500 rpm and 283 bhp at 5000 rpm.

I believe the power numbers came from theoretical results with the perfect exhaust and induction system where there is no problem with top end breathing....

[johno]

In fairness this is a complete minefield ...

If yours is a standard 500, no mods, the expect 260 as highlighted alreay. Below that then get it checked. Above that without mod's you're doing well.

[dumbfunk]

I don't doubt that *some* TVR Griff engine at *some* time measured 320bhp but the general consensus is that it was not in a car or running ancillaries and had erm ... optimised tolerances.

The torque number is much closer and the performance figures closer still. Save the bhp data for the pub and its all good in the hood


df

[virgil]

Alex Gurr said:

Blimey - 320bhp is quite some exageration from the factory then

Yes indeed, but there are a few folk kicking around here with more like the 'published' figure, so it is possible, but as is always the case...quite expensive.

Though with 'only' 260bhp, it is still pretty quick

[Alex Gurr]

virgil said:

Alex Gurr said:
Blimey - 320bhp is quite some exageration from the factory then


Yes indeed, but there are a few folk kicking around here with more like the 'published' figure, so it is possible, but as is always the case...quite expensive.

Though with 'only' 260bhp, it is still pretty quick

Oh yes indeed. It certainly feels quick, just not 300bhp/ton quick. Although coming from a Caterham Superlight the low reving, torque rich delivery really stands out.

I am not sure I want to go any quicker just yet, but am sure there will come a time. For now I just want to enjoy the gorgeous shape, fantastic sound and lazy delivery, whilst trying to ignore the fuel consumption and slightly iffy smell

[so8]

Mine as standard was 221 bhp at the wheels ..... which was 267bhp at the flywheel. I was told that was a 'good' standard figure, right in the middle of those the engine usually produced.

[jeffsy]

I ran my 'old' engine on Joolz at Track-cars RR and it pulled 251bhp from memory.Standard engine, unmodded. I believe Joolz set up is thought of as being 'honest' as well as there are some places that are believed to 'big up' the figures (allegedly). I was well pleased with that at the time....

[rev-erend]

I've never heard anyone say a Griff 500 feels slow with 260 ~ 280 bhp.. so even though TVR (and most other manufacturers) tend to exagerate - it's still a very quick little car

[tgriff]

97 griff 500
skimmed heads compression ratio 11.5 : 1 ported heads , fast road cam, solid lifters , double valve springs adjustable push rods , jaguar air flow meter various other bits and pieces

330bhp at the wheels , calculated 17% run down so 386 at the flywheel, at home I have the RR print out.
Car is horrible at slow speeds lumpy as fcuk , torque is really silly wants to kill you at every oppertunity.
overheats at slow speeds

but bloody hell in the dry, stright road,good tyres and very very little would catch it 0-120
Steve

[Griffter]

At the recent rolling road day in Bristol, 13 Griffs ran. 4 pinked and had runs abhorted. The average for a standard 500 was 265-275 bhp. The two 4.3s managed 256 & 250bhp. All at the flywheel.

[Lord Grover]

1992 Griffith 430 (>90,000 miles)



I assume the figure recorded is that at the wheels, then calculated back to the flywheel? I further assume there must therefore be a(some) formula(e) to work this out depending on variables such as transmission, wheel size, gearing, etc.
I was not asked to provide any such information so I wonder how accurate the flywheel figure is. Can anyone enlighten me please?
Edited to add: Or maybe the Drag figure is related?

Edited by Lord Grover on Tuesday 20th February 09:28

[crazycraig]

Lord Grover said:

I assume the figure recorded is that at the wheels, then calculated back to the flywheel? I further assume there must therefore be a(some) formula(e) to work this out depending on variables such as transmission, wheel size, gearing, etc.
I was not asked to provide any such information so I wonder how accurate the flywheel figure is. Can anyone enlighten me please?
Edited to add: Or maybe the Drag figure is related?

Hi Ian.

The way I've always seen it is that there are so many variables from accuracy of the dyno, the operator, which gear's selected, atmospheric pressure, temp, tyre pressure, tyre condition, tyre slip, strap down tension, weight in the vehicle's boot, wheel alignment, running gear condition, different run down methods, and many many more, it's virtually impossible to calculate the exact flywheel figures unless you take out the engine and bench dyno it.

Most operators use different methods of run down to 'try' and work out the transmission losses but these can vary wildly, so some people use a rule of thumb % for the losses and add it back onto the wheel figures.

The figures I tend to believe for losses are -

10 - 15% for FWD
15 - 20% for RWD
and 20 - 25% for 4WD

[mrcosmos]

Just thought of the cheapest 20 BHP on the market.Keep fuel tank around half full,be totally unsocialble[no passenger]and 6 months membership of weightwatchers.Well its only an idea! How many race car drivers do you know that look like Jonny Vegas.Cheers everyone,see you at the Growl.

[Griffter]

Lord Grover said:

I assume the figure recorded is that at the wheels, then calculated back to the flywheel? I further assume there must therefore be a(some) formula(e) to work this out depending on variables such as transmission, wheel size, gearing, etc.
I was not asked to provide any such information so I wonder how accurate the flywheel figure is. Can anyone enlighten me please?
Edited to add: Or maybe the Drag figure is related?

At Interpro they measure the bhp at the wheels, then measure the drag of the transmission on coast down from max revs. P flywheel = P wheels + P drag
In your case 256 = 175 + 81
I think you only need the other stuff if you want to calculate torque - which they didn't.

Edited by Griffter on Tuesday 20th February 12:50

[crazycraig]

Griffter said:

At Interpro they measure the bhp at the wheels, then measure the drag of the transmission on coast down from max revs. P flywheel = P wheels + P drag
In your case 256 = 175 + 81
I think you only need the other stuff if you want to calculate torque - which they didn't.

If that's right it would equate to 46%.

Sure you didn't bung him a fiver Ian to boost ya numbers.

[Griffter]

crazycraig said:

Sure you didn't bung him a fiver Ian to boost ya numbers.

I reckoned he bunged seven quid - pound a horse power eh LG?

[Lord Grover]

Griffter said:

crazycraig said:

Sure you didn't bung him a fiver Ian to boost ya numbers.

I reckoned he bunged seven quid - pound a horse power eh LG?

The most important thing being... I recorded the best figures (for a 430) on the day! - Furthermore, I can't afford seven quid, even if it was needed.


As this is a private discussion; I'd swap mine for either of yours - but don't breath a word to anyone else - cos I'll deny it!