23 replies to this topic

[hammoj28]

Right jumping ahead a bit here but here goes anyway. I haven't got my 1275 MG metro turbo engine yet but my Dad says when we do get it we should get it bored out. What kind of size should I get it bored out to?? I have heard that they have been bored out to sizes like 1600cc but I expect they would probably blow up. Any suggestions?? Also can you put twin SU' on them or do you have to stick with the turbo carb?? thanks in advance.

[Guess-Works.com]

The maximum you can sensibly bore an A series block to is 74mm, which will give approx 1400cc with a std crank, then using a longer stroke crank can it up into the regions of 1500, but you are talking about an engine which is at the extreem of it limits... any more than this and your close to breaking through oil ways, water channels etc.. ( well you're already close @ 74mm )

I've heard that 1380 (73.5mm) turbo's go well, but you have to remember to keep the compression ratio down ( increasing the bore also increases the compression ) and turbo's need lower CR's..

Re carbs, why use anything other than what the turbo was designed to use ?

[Turbo Nick]

its best to keep a turbo to 1293 really, bigger bores like 1380's means less meat between the cylinders and you can get bore flex.
I know there's a bloke on turbomini's with a 1380 turbo, i think he runs about 15psi and it goes pretty well apparently.

Just stick with the standard turbo carb, there's no way you could put twins on without fabricating your own inlet manifold then you'd also need to make a plenum chamber aswell. plus there probably wouldn't be enough room in the engine bay without even more bulkhead mods, and access to the turbo and the downpipe clamp would be impossible.

basically forget most things about tuning an N/A engine when it comes to a turbo, they're completely different!

[philster]

a lad i know from the shows has a 1293 turbo with weber alpha injection and a t2 turbo, it goes like stink and regularly posts low 13's on the strip.
It has five different modes he can switch between, each mode altering the boost and ignition/mixture settings.
He can put it on the tamest setting and use it for pottering the shops with no prblems and even returns reasonable mpg! But flick a switch and it turns into a 7mpg guzzler.
last time i seen him it was running about 147bhp at the wheels and apparently he's done a lot more on it since.

[hammoj28]

Yeah I have heard lots of people speaking about 1293cc being a good size. what would this cost to get bored out?? Also how much would a t2 cost and where ould I be able to get one.

[hammoj28]

Also whats weber injection?? I assume it's and injection system that replaces the carb, expensive I guess??

[clubman_dan]

stick with the carb, its simple and it works basically, matt woods (aka mini williams on turbo minis) has 224bhp or something crazy like that running the turbo carb, just keep it simple and you'll get god results, i've been in a 100 bhp mini and that was fecking fast, the metro turbo has almost 100bhp straight from the box,
getting to the point, don't bother injecting just spend the money you save on making the engine strong.
DAN

[hammoj28]

O.k, so how much do you reckon it would cost to get it bored out to 1293cc. And a t2 turbo??

[clubman_dan]

t2's are going to vary in price, don't get ripped off, make sure there is no play in the shaft, a recon turbo will cost up to £300 or more, a decent second hand one should set you back 100-150 i guess, not too sure though, i just got a t2 which was reconditioned and only did 2k miles for £150 so i guess paying over £150 for a less than perfect turbo 2nd hand would be a bad idea, don't forget a lot of them will have been ragged to death before they go up on ebay or where ever, just takes care.
as for the rebore swiftune are charging £70 for a +.20 rebore and £35 for a centre main strap to be fitted, this sort of price is probably about the going rate at most places i would imagine, make sure you budget for a rebuilt gearbox, and probably straight cut drops, turbo phil will probably know more about that sort of thing.
HTH
DAN

[hammoj28]

Right so basically heres what i need to spend:

£150 on turbos 2nd hand
£70 on rebore
£35 for centre main strap (whatever that is?)

Also I will need?? bigger pistons and rings. What else wil need uprating?? I also assume the gearbox will be bloody expensive.

[clubman_dan]

it seems like your in the position i was in a little while back, still learning, we always are!
a centre main strap keeps the centre bearing for the crank shaft nice and tightly secured, it is pretty much an essential on any reasonably tuned mini engine, the prices for turbos is just a guide, don't follow it religiously, do some research and make sure you take the time to find a good one, there's plenty out there, the gearbox would cost about £350 for a fully rebuilt standard box fomr most mini suppliers, aim for some special "turbo" pistons, they have a larger dish to drop the compression ratio, (this is important on a turbo motor, especially if you want to run high boost) i think mini spares do some good ones, they come with rings too i believe, its probably worth gettig the crankshaft tougened, but i'm not sure sure how much it costs,
be prepared to spend the money on the proper stuff, its not worth getting it all cheap then finding your engine just blows as soon as you give it some welly,
also don't forget you need a fuel regulator, turbo fuel pump and modified fuel tank..
just noticed, that list of stuff looks scary!
dont be put off, it will be worth it!!!
DAN

[hammoj28]

Thanks a lot for all that info. I would have thought that I could use the origional fuel regulator, turbo fuel pump and modified fuel tank because it's a turbo engine anyway be obviously not.

Yeah I am still learning at the moment but my knowledge is getting better(so I hope). Best way to learn is actually doing it. I will try not to take shortcuts as I have heard that turbo motors like blowing up. I just want a turbo mini so much.

By the way I would also like the dump valve whoosh. That means that I would have to upgrade the dump vale doesn't it?? Expensive or not??

[clubman_dan]

do you have the original turbo fuel regulator? if so use it, the same goes for the pump, if you have metro turbo fuel pump use it too, it will save you money, the reason you need those is the fuel pump is a special high pressure pump similar to injection fuel pumps, the regulator is a rising rate one meaning it delivers varying amounts of fuel according to engine load, this stops you melting pistons from lean out! so remember the regulator has to be a rising rate one.
the tank needs a fuel return pipe put in nice and high up so that the fuel not used can go from the regulator back to the tank.
the plenum chamber will need modifying to fit a dump valve, its not too hard to do i don't think, i havent done it yet though! still building my turbo (998 turbo, just to be different! ) and you can then block of the weedy standard dump valve which is next to the carb on the plenum. i can't really explain without pictures.
turbo minis don't like to blow up by the way, as long as you build it carefuly and make sure you ROLLING ROAD IT! (very important) it will all be good. they only blow up when they are poorly buit, badly set up or running too much boost for the engine spec to take!
i cant wait to hear that dump valve go off on my mini!!!
DAN

[hammoj28]

Well as I said I haven't got it yet. However I was speaking to the guy who can get it for me and it is an whole MG metro turbo. The car is a bi of a wreck apparantely but the engine is really solid so I expect I will get the whole package!!

A 998 turbo will be mean. I love the idea of a dump valve on a mini, so different. Would shock people a bit as well.

Thanks again for all the info. I just can't wait to ge tthe engine and start doing stuff to it.

[Turbo Phil]

As already said, sticking to the smaller overbore sizes will help reliability. 1293 being a popular choice. Minispares "mega pistons" are suitable for a Turbo engine as are Omegas "Turbo" pistons. Don't bother with forged, a good cast piston, as mentioned above will be fine.
Check the engine when you get it, if you're really lucky it may not even need to be rebored. The stock 1275 MG Turbo pistons are a good bit of kit, and going from 1275-1293 will gain little in terms of power.
Fitting a dump valve is easy, just make sure you block the "overboost spring" in the plenum. http://www.turbo-min...9320/index.html

Phil. :grin:

Heere's a picture of a centre main strap for you. :wink:

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