when turbocharging a car u want a lower compression ratio right? i know the compression ratio on a cooper is 9:1 or higher(not sure). i want power baby!!! is there a way to lower the compression ratio? say to 8:1(perfect for a tuurbocharger ). Any help would be appreciated.
Thanks,
Ben

 

The CR on the non S Cooper is 10.6:1. This fact coupled with several other mechanical issues makes this engine, as well as the entire car, a very poor candidate for turbocharging. The other issues are durability issues. The MC, normally aspirated engines do not have the piston oil squirters and other enhancements necessary to provide durability when boosting intake pressure.

Additionally, the transmission in the MC is not near as strong as the MCS unit, another downside to serious power increase.

I too have an MC and would welcome more power. I prefer the looks, the lightness and simplicity of the MC as opposed to the MCS. The MC is 150 pounds lighter, is geared lower and a few other things that make up a little bit for the lower power availability. But, you can't have your cake and eat it too. If you are looking for considerably more power, you really should start with an MCS.

The good news is that if you want to move to an MCS, the MINI market is so crazy, that you might very well be able to get more for your MC than you paid for it, making the upgrade a little more pallatable. In the long run, I truly believe that an MCS would be a much better and wiser choice than turbocharging this engine and overstressing the drivetrain.

Good luck.

 

mybroscoop,

I just had a thought about your compression ratio question.

I have no idea if this will work, but posting a few questions and doing a little research should answer it for you. There are two things that determine compression ratio; combustion chamber size and piston dome or dish.

It could be that the MCS, with its lower compression ratio accomplishes it with a larger combustion chamber cylinder head. If this is the case and if the head is interchangeable with a non S engine, which I fully expect that it is, you could lower the compression ratio by installing an MCS cylinder head.

The stock MCS cylinder heads should be somewhat plentiful on the used market since they are removed whenever the JCW performance kit is installed. I also wouldn't be surprised if you learned that they have larger ports and/or valves.

If on the off chance this is a doable deal, you still will not have the other durability enhancements of an MCS engine, but it makes the project more feasible.

Good luck,

 

it is not the head but the pistons that give the S a lower compression ratio than the cooper. But thats also a doable swap with the sprayers, youd just have to find a wrecked engine that only had those parts. The only difference in the cooper and s head is the composition of the metal for the valves.

 

I thought the JCW kit was all "exchange" because the MCS parts are modified to be JCW parts and act as the core. The heads are ported, polished, with new valve gear, but they did start life as a MCS head, did they not? The supercharger is the same - it is rebuilt with coated vanes and other improvements, but it is basically a modified MCS part. Otherwise what COULD they do with al those old parts - they do not offer them to the purchaser of the kit. Who gets them?

 

heres where one set went:

http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW

http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW

 

except for the valve materials, they are identical. Soooo... the fatvalve heads, or a prted and polished head for either will do the trick for a MC.

 

Good information here. After I wrote the above post I noticed on the Tuner Transformation episode with the MCS that the S engine had dished pistons. I didn't know, though, if ALL the compression loss was due to pistons alone.

A note about swapping for MCS pistons. Yes, this apparantly would take care of the compression issue, but it is a very bad idea to simply stick a set of pistons in your current block. Pistons must be fitted to the block. When rebuilding an engine, the machinist has the piston set close at hand while boring/honing the cylinder to fit.

 

The compression ratio of the MCS is 8.3:1, the pistons are forged and this is a very conservative compression to run even for a turbo application. Most tuners and engine builders will drop from say a 10.5 or 11:1 stock compression to 9.5 or 9.0 :1, and rarely lower than 8.5:1 for example the Honda S2000, a good example of a normally aspirated car that has been already turbocharged and turbo kits made available by a few tuners.
There is one in this month's Turbo magazine that is running 9.0:1 custom forged pistons and pushing 23psi!! I Another example is my 2000 Audi S4, it has 9.3:1 compression, and I run 22psi of boost. So if you own a standard cooper, I would spend the money on a set of pistons(custom low compression pistons run about $150-$200 each if you shop around) and forged rods (about the same$$), and depending where you go, it will cost around $600-$1000 to install them, unless you can do it on your own, and you now have a boost ready engine, but of course now you need to give the transmission some goodies like a quaife, a better clutch, and maybe some stronger gears. You'll obviously spend as much as you would to make up the difference in MSRP between cooper, and cooper S...but you still have a car thats 100+lb lighter, and one hell of a sleeper!

 

MassMiniac points out what, to me, are the most important considerations when souping up an MC; the weak gearbox and the fact that the expense will far exceed the difference between an MC and MCS.

The MC compared to an MCS is right at 150 pounds lighter, in first gear it has about a 20% lower overall gear multiplication and much lighter wheels and tires. All these factors prevent the MC from being quite so far behind an MCS in the performance category as the horsepower figures indicate at first glance.

Since I too have a new MC, I am looking for more power, but I don't want to do it with a result of engine or gearbox life that will be measured in hours, weeks or months.

My approach is going to be slightly warming over the engine and spending the money to make the car handle as best I can and still not jar my teeth out.

Everyone loves lots of power and I'm CERTAINLY no exception, but if I have a car with really fun handling, which the MC is certainly capable of achieving, I can be happy with less than neck snapping power.

There is no doubt in my mind that by following MassMiniacs very good suggestion of beefed rods, forged pistons, light flywheel and a turbo, you could make this little darlin' FAST. Where my hesitation comes in is from the sick feeling that would come when the gearbox started making all that noise, or the engine spit up all over the road.

Everything has limitations and a limit of practicality. Now mybroscoop, I guess what we need to do is figure where in the world in this tiny little car we can hide the nitrous bottle.

I'm an old guy, so I've watched the cycle of particular cars being new, with expensive parts and performance goodies, moving to the car aging, depreciating and parts becoming dirt cheap on the used market. In ten years or less, you will be able to buy a wrecked or otherwise discarded MCS for nearly nothing. At that point the possible combinations will be fun to think about. At that point, building the car that MassMiniac describes will be very feasible for much more affordable cost.

At that point a six speed swap into an MC will be a low dollar project.

Good luck,

 

I never did on engines I rebuilt.

Well, one time on a 1959 Ford, the cylinders were so worn that I needed to get larger than normal pistons, but I STILL didn't have the pistons before completing the block.

There's plenty of clearance between the piston and the cylinder. You don't want them to really be close at all.

Try taking the rings off a piston and fitting it in a cylinder. It drops right through with a LOT of clearance.

 

Yes, of course, you can just drop a set of pistons in any old block and it will work. To have a good running, long lasting engine, however, they should be properly fit with proper clearance. Otherwise you will either be too loose causing a lack of good sealing over the long term, or too tight causing insufficient oil clearance and added friction, possibly even siezure, once the piston expands with heat.

You can do it the backyard way, or the proper way. Take your choice.