F50 GPP ... The Old One, the story begins....

So just to confirm that's a 2.5 bottom end with A610 cams, running how much boost to make 400bhp? And makes about 50 bhp more than a 3.0 version of the pretty much the same engine at half the boost . Can you explain how this is possible to a layman like me?

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As always I think Martin's being rather modest on the amount of thought and work that goes in to this.

Something was troubling me with the F525-F50 graph last night. Just realised I'd blanked out the power curve from the second run on mine so I had two torque curves. Silly sausage.

Anyway all fixed now (yes I should fix the three car one two when I get a moment). Worth noting that where the two torque curves cross you get the same power value as you well should at the same RPM.



Useful calculator here for QC - http://www.1728.org/mtrtrq.htm

So I should add that mine is way up on torque lower down as you'd expect. This was with the old failing turbo though so it'd be interesting to see what it could do now.

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I think you misinterpret my interest, its not criticism, not bothered whether mine is more powerful, I like my car as it is regardless of how much power it has, could turn the boost up more but feel the car is nicely balanced as it is and nothing too stressed. Its never been about that, Dave Miles car I'm sure is more powerful than mine for the same boost pressure. Just you said it was basically a 2.5 version of an A610 engine spec wise and makes 64 bhp more at little more than half the boost pressure of a decatted 610. Would love to incorporate some of those mods into my car so I could make the same power and run half the boost pressure. PRV tuning and getting good power out of them is great and about time some modern technology went into it.

Saying that though could you not concede that 324 bhp at 7psi, on a similar spec engine but 500cc smaller than a standard A610 which probably makes no more than 210-220 bhp at that boost is a miraculous improvement. That would be an improvement in efficiency of something like 60% taking into account the smaller capacity,. If you tell me that's realistic I've got no reason to disbelieve you, your cleverer than me with this stuff by a mile. I want to believe it :0).

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Actually thinking about it that 324 figure was probably just an error because you would be disappointed to get 76bhp from an additional 19 psi of boost. My comments have never been about dissing you or your work , I think the stuff you do looks fantastic and has obviously been researched and tested extensively beforehand. I do think the rollers you use probably read a bit higher than most RRs but I know that's not why you use them. Be good to see how quick the cars are , love to see some GTAs shocking some more exotic machinery. Would much rather do a Santa Pod day than going on the rollers, having burnt holes in 2 exhaust manifolds setting up over the years, sort of puts me off. A 400bhp GTA should run high 11's low 12,s at about 115 120, which is very fast by any standard. Best time I ever managed was 12.8 at 108 on a hottish day at The Pod a few years back. Runs a bit more boost now and the mapping is better so might make 110. I only set out to achieve 300bhp when I started my GTA in 1990 (gulp), but was always trying to do this with bolt on mods. Found I couldn't do it with the 2.5 with what little info and equipment was about then and when a Safrane biturbo engine came up at a reasonable price I bit the bullet and had it converted to fit. Chargecooler carried over from before, bought a very high quality turbocharger (which could have probably been a little smaller with hindsight) and then the worst decision of the build - fitting aftermarket management. Really wish I'd found someone to remap the A610 ECU , be a nicer car to use everyday and probably only made 10-20bhp less. But too much money and grief to change now. Haven't had it on the rollers since it was running 0.7 bar where it made 280 bhp. Pretty confident the extra 0.5 bar will have taken it past 300bhp. If I get asked how much bhp shes got mister, I say about 310-320 which I think is a fair estimate.

Good luck with future developments. Be good to see some of it marketed by Lee as phased upgrades.

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The suspension can be quite hard to set up and is sensitive to small changes which doesn't help. I've tried the Spax and GAZ set ups back to back and personally prefer the Spax, gives a better ride for the same level of stiffness. Prefer the bigger wheel setup on GTAs , the ride isn't too badly affected and find the front resists understeer much better. A proper alignment set up and setting the shocks at about 40% of maximum hard works best on the fairly poor roads near me but would up that if the roads were smoother or for circuit work (which will be never because the car is too loud!). John is working on a mod that will allow the rear camber to be altered which will work well with lowered suspension.

Is the clutch standard Martin? All this talk of Santa Pod is making me wonder what you'd be left with.



2nd gear rolling start may be better option clutch / driveshaft wise.

Or if you want to test the entire driver / car package, maybe a 60s Le Mans style entry where people jump into the cars..... or maybe not.

I've been on a diet since then :0)