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Dyno Run

I'm still waiting for a reply from Cometic, the guy was away in the US last week, so hopefully he'll get back to me this week.

I took the head gasket to an engineering shop and we opened up some holes for the waterways...don't try this at home, the steel is very hard & you might distort the gasket.

Thanks for the comments about the new car. Good result yesterday, class win, fastest saloon car, fastest car on road tyres, 10th overall & I had a good battle with some slick tyred Caterhams. Boy, those Radicals are fast !

I'll be doing a full race report for the site later tonight I hope.
 
Is that at the wheels or with calculated drivetrain losses added back in to approximate the flywheel figures? Presumably at the wheels, which would indicate around 285 at the flywheel, which feels about right for a fairly high compression 3.0 at 7psi. The modest boost should mean cool charge temperatures and the whole thing having a fairly easy time. It might not be a cheaper way of getting that sort of power out of a turbo, bumping a 2.5 up to 14 or 15 psi being the cheap and simple way, but it's a lot nicer sort of power curve for a fast yet easy-going road car. Taking the second run as representative, it's going like a train from about 2400 rpm, which is lovely.

Looked at another way, I reckon with that drivetrain, from a standing start you could stay with a fully-extended normally aspirated 2.7 or 2.7 car without ever exceeding 3000 rpm, which would be a giggle.

But what happened between run 1 and run 2? It's a totally different picture below 3500 on run 2.
 
I think thats calculated back. The differences are I think due to it needing more tying down. It tried to jump off the rollers when off throttle. I normally run a bit more boost than that but I cocked up and reset the boost control when I was setting up the knock monitoring.
 
I would expect that to be at the flywheel (DIN on the graph) and about 250 would seem reasonable to me - any higher at that boost would be odd I would think.

Very crudely, 3.0 litre engine, so 20% bigger than a standard turbo, but at only 0.5bar boost gives 4.5 litres (ignoring VE).

Compared to 2.5 litres at ,say, 0.8bar boost on a standard 250 turbo which gives 4.5 litres again.

So should see similar power - about 250bhp at the crank.

A 250 turbo will make 300bhp at 0.95 bar by the way.

All very crude and generic, but close enough for ball park comparisons?

Regards

Graham

 
Haven't seen any curves, but logically, an 8v 3.0 ought to be around 185 to 195 bhp at the flywheel, assuming it's of a compression ratio and ignition setup safe for standard unleaded, similar to the setup of the late factory 2.7 944 and 924S, and with a similar sort of cam profile and peak power rpm.

So, yes, I agree with Graham on reflection, my original 285 at the flywheel estimate was a bit optimistic for that boost pressure, and a bit over 250 seems what one should expect, allowing for back pressure and pumping losses.

Barry's 3.0, running standard Turbo boost, did 300 bhp at the flywheel, and that also broadly fits in with Graham's rule of thumb formula.
 
Cheers, guys. I'm awaiting a 3 bar fpr, then a proper setup and I'll post the results.

I was a bit concerned with the whole dyno thing and the stresses etc but it's nice to be able to stand behind the car under maximum power and see no oil smoke. Not something you can do everyday.
 
What compression is your engine running James? Is it low enough to ever get the boost up around the 15psi mark?
 
Thats a very good question. Which I cant answer exactly, I think about 9:1.
I usually run it at 9 psi and its plenty quick enough for me.

CFM (the rolling road operators) are happy to map megasquirt/microsquirt so a proper map should improve performance without needing to boost it to bits.
 
Personally I think for road use there is a lot of be said for the combination of high capacity, highish compression and modest boost.
Oops, better shut up now before Oli suspects me of S2-ite tendencies...
 
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