Improving Performance on an Mpi

[Billy]

Following from the discussion in the For Sale section on JKnight's 00 Mpi, I've started this thread to talk about tuning an Mpi.

Here's a great discussion on the subject from the Mini Cooper Register's forum:

http://forum.minicooper.org/showthread.php?t=8813

Dylan, feel free to add your own spec.

Billy

[Jknight]

Does swapping the throttle body make any real difference?

[Billy]

Some say it does, others say it doesn't. The 48mm plastic bodies are known to crack. Burlen supply both 48mm and 52mm metal bodies. The official Cooper Works kit used a 52mm body and a fuel pressure regulator. Apparently you can pick up the regulators cheaply off old Fords. There are plenty out there that will tell you that you need to spend a fortune (especially if they're making a handy profit out of the deal) but you can do it in stages and gauge the effects for yourself. Start with modifying the airbox and the restrictor on the throttle. Total cost: FREE! Then consider an RC40. And maybe then Santa might get you a Stage 3 head. Do it one step at a time and the improvements will be worth the effort.

[keith]

just sounding a note of caution here. this from the NCT Test manual: (http://ncts.ie/pdf/nctmanual.pdf)

LAMBDA
13 For vehicles first registered on or after 1st day of January
1994, the lambda value at 2,500 rpm or at the speed
specified by the vehicle manufacturer is not 1 ± .03 or
within the vehicle manufacturer’s recommendation.

cars prior to that don't appear to have a lambda test applied to them.

basically what this means is that the later Mini's in Ireland have a much more stringent emissions test to pass the NCT. This does not appear to apply to cars in the UK, so modded cars that are MOT certified might not pass the NCT test here.

[Jknight]

Some say it does, others say it doesn't. The 48mm plastic bodies are known to crack. Burlen supply both 48mm and 52mm metal bodies. The official Cooper Works kit used a 52mm body and a fuel pressure regulator. Apparently you can pick up the regulators cheaply off old Fords. There are plenty out there that will tell you that you need to spend a fortune (especially if they're making a handy profit out of the deal) but you can do it in stages and gauge the effects for yourself. Start with modifying the airbox and the restrictor on the throttle. Total cost: FREE! Then consider an RC40. And maybe then Santa might get you a Stage 3 head. Do it one step at a time and the improvements will be worth the effort.

Modding the airbox consists of cutting away the extra plastic inside it that restricts the flow right? Would rigging up some kind of cold air feed from the grill to the airbox inlet help any bit too??

[keith]

Modding the airbox consists of cutting away the extra plastic inside it that restricts the flow right? Would rigging up some kind of cold air feed from the grill to the airbox inlet help any bit too??

yes.. i use a flexi aluminium & cardboard tube from the grill to the airbox. granted thats on a clubby and its got a carb, but the principle is the same.

[woody]

LAMBDA
13 For vehicles first registered on or after 1st day of January
1994, the lambda value at 2,500 rpm or at the speed
specified by the vehicle manufacturer is not 1 ± .03 or
within the vehicle manufacturer’s recommendation.

Surly that should read " is 1 +/- .03%"

The main objective of the ECU is to maintain a lambda of 1 which is the optimun air /fuel ratio which it does by adjusting the timing and fueling via the injectors.The Rover ECU is a learning ECU which can adapt to changes to the engine but the one thing that will throw it out is a lumpy cam. If changing the exhaust manifold it is critical to relocate the lambda sensor in the correct positoin.

[Dylan8660]

I'm not going to refer to the cost of this as I never said it would be cheap and its up to you whether you go all in on piece by piece.

The main performance gain you'll get is from the head, everything else just makes that work better.

If I was to start again then I would go for the John Cooper Works kit from Classic Minis Online (if they're still going) simply because it was factory recognised and they continuity of the brand might add value. The Palmer Brothers kit is worth a look as it's basically the same except you get the 52mm throttle body too.

Kits include: Stage 3 head, 1.5 rockers, LCB (do your research on this as the lambda position is important), Free flow twin box exhaust, K&N air filter element, Modified air box, Ported inlet manifold and a uprated fuel pressure gauge (my personal view on these is that they should be avoided as they and poorly placed lambda sensors do nothing but cause emission failures).

The other performance part for the top end of the motor I'd add to that list is the SW5i duplex kit.

The one thing you must prepare yourself for is Diff failure. Because of the increased torque of the ridiculas 2.7:1 final drive (makes the mini geared for 130mph) it will break, usually around 40k without warning just as your pulling away. Mine went at 35k yours could be due, but view it as an opportunity to get a strong diff and change the fd to 3.1:1 (don’t forget to change the speedo drive to suit). I put a 2.95:1 fd in when mine went which is better, 75mph @ 3500 rpm, but I wish I went for 3.1:1 so that 4th would be more useful.

Then there’s the handling……..
Good luck.

[Billy]

I'd agree with Dylan on the diff. Mine shattered the diff casing at about 55k and I have since replaced it with a Minispares 4-pin diff. As regards the final drive, I like the fact that at 80mph on the motorway, the engine is only at 3500rpm and you can hold a conversation but I use my car as my summer daily transport so comfort and noise level is important to me.

[Jknight]

Lots of food for thought there. Looks like I will have to take it slowly and get the bits one at a time. Mostly due to my long suffering girlfriend's constant dismay at the money I keep spending on the car

[Dylan8660]

I always find quoting the cost of a new Golf/Panda/Fiesta, its servicing, depreciation and a few comparative parts over a similar period of ownership helps keep that conversation in perspective.

[woody]

You can get the best of both worlds on gearing if you fit a 5 speed box with a lower diff ratio .I think 2.9 in fifth is about 3.2. I agree you should buy the best head you can afford and then build on that.

[Jknight]

I always find quoting the cost of a new Golf/Panda/Fiesta, its servicing, depreciation and a few comparative parts over a similar period of ownership helps keep that conversation in perspective.

Good point Might just try that next time she is complaining!

[jonathanganly]

Hey guys, following the thread,

Have a 1999 MPi mini, already have a K&N Kit and a magnaflow back box on t already, sounds great, just wondering about these John Cooper Works and Palmer Brothers kits, where can you get them, can some post a link?

cheers.

[Dylan8660]

The Cooper kits link isn't working, http://www.classicminis-online.co.uk/ and Palmer Bros don't seem to have a web site, so it'll be the old fashioned telephone call for them. Failing that either Mini Sport or Mini Spares do a kit but beware of the Lambda boss postion I mentioned earlier.

[bc130]

Just wondering if you changed tha car.I passed yesterday evening and saw a grey bini sitting in the place of your mpi.

[Billy]

Just wondering if you changed tha car.I passed yesterday evening and saw a grey bini sitting in the place of your mpi.

Not me anyway. Who do you mean?

[bc130]

Sorry for confusion. The reply was ment for JKnight.