10 replies to this topic

[sam138]

just wondering if someone could help point me in best direction for next engine modification. The mini is a road weekend use only really and I’ve searched online at all the possible options turbo/ supercharger and 7 port but I’m really stuck.

I currently have a fully rebuilt 1275 cooper engine as per below spec and have a spare suck through supercharger kit. But I’m really concerned after reading story regarding blowing pistons etc with forced induction and the possible poor running of the suck through set up. Which frankly scares me after taking the time to rebuild an engine. I’m looking for between 90-100bhp for hopefully a once reliable engine.

Is the m45 suck through set up really that bad on low boost 6/7psi ? Am I going to be having reliability issue all the time ?

Current engine spec:
1275 cooper rebuilt engine ( honed, bearings,, rings ,water pump , oil pump etc )
Stage 1 kit ( maniflow etc)
MED ultralight ST1 clutch kit
Upgraded ally rad
Standard gearbox
Rebuilt hif44

73bhp at flywheel with 80ft I.b torque

Current supercharger kit :
Will aim for 8.5.1 compression
Suck through m45 Hif44 carb (Vmax )
Metro turbo distributor
90mm crank pulley ( speaking with Stuart at Vmax should be 6-8psi instead of the normal 110mm . Doing calculation it’s coming out at 8psi.

[Bat]

Hi,

If you want reliability then I'd go for a GT1752, intercooler, metro turbo carb and ECU controlled dizzy less ignition.

If you want to go all out have injection too.

Ignition and fuelling controlled by an ecu will protect your engine if done properly.

Cheers 

[DeadSquare]

Don't be frightened,  I have blown A series for almost 50 years and never had a melted piston, which I have had happen on full race engines.

 

Listening to other people's blowing problems, it seems that they claim that they are only aiming for a 20% increase in power, but go for 40% without preparing for it, and then wonder why things go wrong.

 

You have to get the timing correct for the rev range that you will be running at.  DON'T RUN A WEAK MIXTURE.  Some people say that you must run a rich mixture, which is helpful but wasteful.  Remember that a suck through set up blends the load, which produces a better burn.

 

If you are frightened,  pass the buck to an expert.

[mini13]

The usual reason for problems is cutting corners on setup, get it on a rolling road with a good operator and you should be fine, Stuart gurr would be a great choice. Too many people get them running then can't resist " trying them out up the road" without establishing everything is OK.

I do prefer a turbo, but as you have the vmax kit it would be a wise way to go. As bat says I would definitely get a marble ignition system on there too.

[sam138]

Thanks for the help.

On a fully rebuild engine on standard internals would it be ok to run low boost suck through 6-8psi with a compression of 8.5.1 ? With an updated turbo clutch plate / cooling and x pin diff .

Could someone help me on how to measure the piston/ block deck height please ? As I’m trying to work out my compression.
Could you use a straight edge with a feeler gauge ?

I also need to remove the diff to change to x pin, I’ve had a look through the forum and people have said it’s possible with engine in situ by moving it forward ?

[Bat]

Hi,

I'm aiming to put your 6-8 possibly 10 psi into a bog standard MPI engine!

I'd say don't lower the compression unless you're absolutely sure you need too.

It may be that you have to with a supercharger or if you used an ECU to control the ignition you wouldn't need to?

I've no experience with a supercharger but the turbo is well underway.

Cheers    

[Steve220]

with an 8.5:1 ratio, you could run good quantities of boost! Mine's a similar CR and I intend to run 15psi.

[sam138]

Thanks for the reply’s. Could I posisbly go to 8.7.1 or 9 with low boost ?

Would standard internals be reliable on low boost ?

[jsyjamie]

This is the best compression ratio calculator I've found.

 

https://jscalc.io/ca...RNEglVkKLQir11T

 

Not sure who wrote it so can't give any credit unfortunately...

[sam138]

Thanks for that I’ll have a look over . What do you guys think of the standard engine spec above I have ? Will this be ok for low boost ? I’ll also run an X pin diff .

[r3k1355]

You'll be fine.

 

Will you be running a wideband lambda or any kind of knock monitoring?