advice
Turbo Mini Forums

building a 1071 engine with a 7 port head and a sprint cam using a standard metro turbo I need advice on compression ratio, boost pressure and do i need a fuel additive. Thanks for any help.
Alan

What will the car be used for Alan? Also, what intercooler will you use and where will it be mounted. What fuel do you intend to use and could we have more info on the cam?

In the 13's at last!.. Just

I'm doing the British hill climb championship in a GTM rear engine car, the intercooler is behind the rear wheels using standard pump fuel and the cam is the Leyland Sprint cam not the super sprint with 1.5 roller rockers.
thanks Alan

You will be able to build an engine that makes good power, but the cam is totally not suitable for forced induction, and the turbo also not ideal.
In very basic terms you will want a turbo specific camshaft, and there are lots of more suitably sized and more modern turbochargers available than the old metro t3, which wasn't even that well matched to the Metro it came on.

have been in touch with Piper cams and they recommend BP 300 3000-8000 rev's duration 316 Deg valve lift 390". As I have used the 649 and the 544 cams in my 1480 engine's but never gone the turbo road that's why I was going to use the metro turbo till it's all set up and running

There is a camshaft calculator online, you can plug in your desired values for what you would like your camshaft to provide for your inductions and exhaust.

Basically it's spits out figures for a cam profile that fits several available cam shafts
Kent 266
MG Metro
SW05
Mini speed turbo cam
There is very little variance between their profiles, the one thing they have in common is lift at overlap that should relate to negligible/zero flow.

Edited by Mr Joshua on 20th Dec, 2023.

Own the day

Have got in touch with Piper and they are grinding a race turbo cam for me now which turbo is the one to get. also on the metro turbo were do the vac pipes go from the top of the turbo and do I still need the vac dump valve on the turbo as I have a remote valve on the plenum chamber.

Those two vac pipes from the brass tee on the turbo go to the computer and to the waste gate solenoid valve. Im going to assume your talking about the OE dump valve fitted to the plenum. If you are then i would say yes you will need a vac style dump valve, and block the oe position with a suitable nut and bolt and sealant.

Own the day

The turbo specific can grind is not much help without knowing your turbine back pressure.
You just need to pick a turbo that’ll work for your needs.. and we don’t know your needs.
A turbo that makes 350hp at 9000 rpm is quite different from one that makes half that.

Report back with an honest statement of where you want the power range to be (while also understanding that full boost at 9000 rpm won’t spool up from anything even close to2000rpm), and the peak hp you are seeking, and the options for a turbo will become clearer.

As the car is just used for racing It is outright power that I want rev's 8500

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Im going to chip in with... what 7 port are you using??
if its a cast iron one... i had issues woth the centre exaust guides nipping up due to heat... ive heard of this even on NA cars let alone a turbo... its why i flogged my head and went down the K 1200 route.

The head is a Specialist Components 7 port alloy billet one and the cam timing = inlet 28* btdc open close 68*abdc. duration 276. exhaust 80* bbdc 40*atdc dur 300*. I have got the engine ready for the buil with the plenum chamber connected to the inter cooler and a blow off valve at the other end is it worth putting a pipe connector for a pressure guige on the chamber.

Your running 68 degrees of over lap assuming that flow is occurring at the measurements you have given.

Own the day

mmm sounds like a lot of cam for a 1071 turbo,

Yeah, i would add a take off for the gauge, and probably one for the dump valve, and for the ecu if using one.