Cr ratio expected boost and bhp?
Turbo Mini Forums

I'm using standard block and Pistons but having the chambers in the head opened up to 26cc hopefully , is anyone running this setup? What can I expect to see from this bhp wise, I'll be using standard t3... And a megajolt setup, Avonbar phase 2 cam, also what would my CR ratio then be? Sorry but I not very clued up on this sort of thing, many thanks

I'd work out a target CR before touching the head.

There's plenty of guides to work out your current CR on here.

Between 0 and 300hp with the information you have supplied.

You need to think the other way around. How much power would you like ish. Then work out what sort of boost you need to achieve that power with the spec of the rest of the engine. That will then determine the CR.

As a guide you should expect.
10psi = 100hp
15psi = 150hp
20psi = 200hp

It can be more or less than these values depending on many factors. But this is what you should be aiming for.

In the 13's at last!.. Just

Plus ........ 25psi Boom !

Edited by PhilR on 8th Feb, 2016.

I want at least 110 bhp if not a bit more, but I want it reliable, standard metty block and Pistons, standard turbo, Avonbar phase 2 cam, I want as much power as I can get woth what I have, the heads been reconditioned but the chambers are standard appart from the head being skimmed which can increase the cr ratio, I'm not well educated with his sort of thing, so would 8:5:1 cr be a good cr to have to work around or?

8.5:1 on another wise standard metro turbo engine (pref with an inter cooler added) will easily be able to make 120+ bhp with reasonable reliability. Much above this and you will need to look at the gearbox. I'd be putting a x-pin in there regardless.

If something is worth doing, it's worth doing half of.

Nice one john, thanks for all the replies, I'll get it sent off to benross he's the guy for the heads heard good reviews

This may help:

http://www.turbo-mini.com/70947.html

I don't know enough about the Phase 2 to comment, but T3 aren't known to boost early. Know that as you lower the CR, you will start to hurt the off-boost performance. If your gearbox is the weak link I wouldn't make the CR any lower than 8.5

People have made much more power with higher CRs (and intercoolers), but of course there's less room for error. Megajolt is a good idea, but you should get a wideband lambda controller+gauge in there too.

Edited by PhilR on 8th Feb, 2016.

Definatly going megajolt, gearbox is standard but fully reconditioned, all tolerances are spot on etc, and got some sc drop gears, I will change the turbo at a later date but for now I'll run with what I have, I've spent quite a bit already with buying the car as well as all the bits lol! Mrs going mad..... Lol and I'll definatly have an intercooler on there straight away

Edited by Jonnyturboboy on 8th Feb, 2016.

X-pin diff 100%

If something is worth doing, it's worth doing half of.

This any good what best buy for money?

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That's the one!

If something is worth doing, it's worth doing half of.

Nice one