you can say its all about the heat of the air your feeding the engine with.
thats why the factory turbo can handle the high CR and the low boost without an intercooler. the quite big turbo doesn't heat the air that much.
if you could keep the temps very low you could run high boost with high CR

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Rover 214 atm ....

I'm not sure what lower compression pistons are on the market, but the static compression can be lowered by the amount you take out of the chamber.

Klaus, your right with the low intake temps & high CR! It can be done, but most drivers get a little greedy....




As Grant puts it nicely.....

High CR, low boost....with an intercooler...some more boost.
Lower the CR, increase the boost. More power on boost but you start to loose out on driveability off boost.
The more the compressor has to work, ie the more boost you want, the more the intake air will be heated up. The hotter the air is in the engine, the less spark advance you can run, thus the less power you will make.
Increase the compressor size, the less work it has to do & the less it heats up the air. So turbo sizing plays a large roll in it too!

Cheers Shane

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If it's not a Cooper S, the mini was designed to be modified!

Hi all


the compromise , boost, heat, compression, build eg pistons.... do those factors hold true for supercharging?

For example
boost is comparitively low compared with Turbo at full boost.. so CR could be higher???
heat - if blow through IC could mean increased CR????


i have heard and seen reference to supercharged mini Compression Ratios - 8s, high 8s and even 10 and 11s -if with forged pistons

thoughts?

It is all the same but most roots type superchargers are less efficient than turbos. That is they will discharge hotter air for a given amount of boost. The result is that you need better intercooling or less total compression ratio - boost combination.

So if you run an Eatom M45 (MINI etc), SC12 or AMR500 you will typically have a hotter charge than the same amount of boost from a well-chosen turbo. Sprintex chargers are much more efficient due to internal compression (spiral lobes) and the centrifugal SCs are also more efficient. Take a BIG step up in $ to run these.

NG has chosen the best positive displacement SC on the market for his (Sprintex) so he will be able to run more boost safely than the equivalent M45 or SC12 fed car.

SC powered cars need a good bypass system if you run a long intake (ie include an intercooler). All factory set-ups have one but the common kit (from Ben '92') doesn't have an intercooler or bypass. It is all just more hardware to try to fit in the engine bay.

M

im very close to getting mine going as well.

im just stuck waiting on parts to come..

Hey guys, I want to know how to put a multi V belt onto my engine to drive the supercharger.

I would just get the kit C-AEA538 which contains the crank, alternator and water pump pulleys from an MPi mini BUT... All the pulleys are NLA. Searching for the kit or the pulley part numbers (like crank LHF100130) either returns nothing or a big fat 'Out of stock'.

So, are there any places with these in stock or are there any aftermarket versions?

What do others do in this situation?

Thanks,

M

I machined my harmonic balancer's V groove down to mate with the outer ring of a Landrover Diesel water pump pulley. I just put the water pump pulley in the lathe and machined the guts out of it. Once machined I welded it in a few places to keep it in place

For the water pump, I got an idler from a generic sort of japanese engine (nissan maybe) that had about the right size and number of grooves. I machined the standard mini water pump pulley down and welded the outer ring from the one from the wreckers.

The alternator is from a subaru - dunno what exactly, it was in with a heap of other alternators at the wreckers - something like a brumby or fiori

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did I tell you that I won a trophy?

Thanks Simon. If I have to go that route I will but I have to pay for machining. The only machines at my work are the copier and the coffee machine and my home tool collection is a little underdone.

First step is a wanted ad I guess.

M

if you've thought about sourcing an electric water pump, a replacement outlet for the block and a fan that will mount to the engine side of the radiator, I'd love to hear about it

would be nice to get rid of the water pump pulley altogether

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did I tell you that I won a trophy?

electric water pump i would use this: http://www.ebay.de/itm/BMW-E81-E87-E88- ... 4ad6ddff1b
if you don't mind its from a N43 engine out of a BMW
and there is electronic to controll it: http://www.ebay.de/itm/Tecomotive-tinyC ... 51be0b72c6
not cheap for sure. but the pump is as reliable as OEM gets.

replacement outlets are readily available. but to modify an old water pump is an option, i think

and if i had to make new pulleys to drive a charger i would skip the poly v and use a Gilmer setup

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Rover 214 atm ....

I'm not going gilmer drive, way too noisy for a road car.

I can't see the need for electric water pump for a road engine.

M

But they sound sweet when you rev it at the lights .

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Respect mine and I'll respect yours.

Why not use the exhaust to drive the supercharger?

yeah... I have a few reasons for going to an electric pump, you mightn't care, but:

my belt doesn't have a lot of contact area with the water pump pulley - maybe only 3" where it goes from the alternator over to the first blower idler
I'd like to get rid of the mechanical fan for a bit more room at the front of the motor, but I won't cut the bodywork
heat-soak after a drive annoys me, I'd like to be able to let the water keep circulating and cooling after the engine is shut off



thanks

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did I tell you that I won a trophy?

i was looking for some other stuff but i found this and remembered this thread.
https://www.flickr.com/photos/mini_klas/14435272262/
https://www.flickr.com/photos/mini_klas/14435477864/

crankshaft and water pump pulley are factory MPi, the alternator pulley is from something else. it has a 17mm hole, fits A127 alternators IIRC. was for my SC setup. but that was not that easy to be made road legal over here, so i dropped it.

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Rover 214 atm ....