Which pistons do I have?
Turbo Mini Forums

According to the large table at Miniforum on engine codes, my 12HC01AA has 9.75:1 compression. Formatting is buggered below, but you can see it more properly here: http://www.theminiforum.co.uk/forums/index...e=post&id=37198

Engine Fuel Pistons
Engine Number prefix cc A / A+ Leaded/UnLeaded Flat/Dished Circlip/inteferance Notes
*** H - High Compression
*** L - Low Compression

12H C01 --> 11 1275 A+ L D I Metro, 9.75:1CR

It is saying that my engine is an A+, Leaded Head, Dished pistons, interference (piston pin fitting I presume), with 9.75:1 compression.

Now I know it is a leap to assume the engine is stock internally, but here is what I want to know:

What pistons would have been in this engine originally? Would they be the dreaded slotted type, or would they have oil drain holes and a solid skirt?

I'm keen on cranking the boost up, and want to know what the broken pieces will look like.

Edited by fortfun on 8th Nov, 2007.

1275 with Back Door Turbo

Hi,
What igintion system are you running, what intercooler and how much boost are you running?
10psi is as far as you want to go with that CR.
To be in with a good chance of it staying together you should run mapped igintion, prefereably with charge temp compensation.
Wideband lambda would be a good idea too!
Rolling road / dyno setup essential.
It's also about as much as the standard gearbox will cope with too....
Cheers,
Gavin :)

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My Mini build diary

Running a Mallory (rebadged as Summit) multi-spark capacitive discharge ignition with boost retard (programmable in degrees per psi of boost). This is triggered by the ignition module on a Lucas 65 electronic dizzy.
The turbo is mounted under the body between the rear wheels. Intercooler is the pipe that goes under the car, around the transmission, up the front of the engine between alternator and distributor, then around the engine to the back where it blows into a heavily modified Weber 38 DGES.
I have wideband lambda. With the permanent wideband install, I've done most mixture tuning on the road. Running ~12.9:1 under high load above 5000RPM in third gear.
The engine never pings. Running US Super Unleaded gasoline, roughly 95 RON.
Right now running 8psi boost. My wideband controller can also do boost control based on MAP sensor & RPM - I have a boost solenoid but not installed yet. It can also control water injection, which is also going on soon. This is the Prologger system, which also has a feature that will drop the boost back to wastegate pressure if your mixture ever goes leaner than a user-settable level. With water-methanol injection, you enrich the mixture. I plan to set the controller to drop the boost back if it ever goes leaner than 12:1.
I've been working with this setup since the spring of 2006 - feel ready now to program up the boost. With the logger I can set it up to give a known, programmed maximum torque through the boost vs. RPM curve. Intention is to run ~100lb-ft of torque from 4000 to 6500 RPM.

Edited by fortfun on 8th Nov, 2007.

1275 with Back Door Turbo