998 project
Turbo Mini Forums

Hi so basically I got my first mini on the road in the summer, which is a mini 1985 mini riz 998, after a few weeks of slightly over excited driving it was smoking rather badly. My original plan was to just rebuild the 998 with some modifications. Cooper head, cam etc.
Since returning back to university for my final year in motor sport engineering the plan has change, my third year project is to turbo a naturally aspirated engine. As I have an A series in bits and would like to have turbo power in my life I am going to turbo a 998. Well first I will be doing the theory behind it all first then depending on time and money the engine may be build. If not built before the end of uni it will be built in the summer.
Another element I would like to look into is being able to run the 998 naturally aspirated after the turbo build, this is because I am only 20 and on a trade insurance policy so not sure I can have a turbo until I am a certain age. This is something I will have to look into during the build. Also look into dyno runs with and without the turbo fitted to analyse the results/gains of fitting a turbo?
So I will be doing some turbo calculation in the next few days so if anyone is interested in them I will post them up.
Also I would be very grateful for any information anyone can give me on specs needed for the build and theory behind the A-series running boost. Any web sites books or anything out there? Also if anyone has any bits for sale of knows of where the best place to get bits for a turbo set up form I would be very grateful.
Should be running 1 bar boosted and achieve 120-150 bhp! Thoughts?
Would greatly appreciate anything anyone’s input.
Thanks Grant.

You have already found the best resource for turboing an A series. All the information you need is on this site. Plenty of people with calculations that you might be able to compare with.

Use the search function, it really works and almost all the questions you have will be covered somewhere.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Here is how I used to calculate air flow, pressure ratio and hp:

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=213848

You can always convert back to NA by swapping the head to get a decent compression ratio. Apart from maybe cam selection, the head is the main difference between NA and turbo.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

"Hi comp" MG Metro turbo and low comp Minis share the same CR, namely 9,4 (also share cam IIRC)

Now the Metro Turbo doesn't have an IC as standard wich is not so good for output and probably requires a very conservative timing to prevent from det.

So, I guess that it all depends on what you expect from the engine.
Obviously an engine tailored to be able to run with or without boost is gonna be a big compromise so is not gonna be sparkling in either trim.
I assume it is doable.

I don't know what a 9,4 CR 998 with a Cooper head and MG cam (N/A) would put out but it is probablyl still better than stock and when turboed, should make you enter the 3 digits power club.

Rusty by nature

yeah that's what I am looking for big power with turbo then average power for road use until I can afford the insurance on the turbo power. long was to go until then though haha

"big power" as in how much ?

Wil H has a 150HP 998 hill climb car.
I assume it has a very high boost hence pretty low comp.
Now that engine without its turbo is probably crap.

120 HP out of a 998 seems reasonable, althought to the limit for standard pistons.

Another way of thinking is dynamic CR.
Let's assume you do your "big power" turboed engine throught a long duration camshaft (=> high RPM), you can then have a high-ish CR wich, when you convert back to N/A will do good with both mid-range power and economy IF you swap back to a shorter duration cam.
I am just thinking out loud here ...
But longer duration cam sap low end where the turbo is of no use if not a drawback.
It all depends on how long a duration and if your engine is dedicated to something in particular or just meeting a target on the dyno ...

Would be probably simpler / cheaper to swap heads then.

You already have on your engine and you will probably want a better one for the turbo application (like a 12G295 from a Cooper 998)
The main drawback I see here is the pain it's gonna inflict you when driving the car in N/A after it's been convert back from turbo ...

Rusty by nature

I have a 998 cooper head.
I am not sure what the spec of the engine or anything is going to be yet still looking in the the whole thing.
i was thinking of geting the engine bored out to +60 then just using flat top pistons will have to work the compression ratio out first.

If your intent is to run it N/A then go to turbo with minimal modifications between the two, the only real way I can see you achieving good power with both with N/A and turbo is to down the bike head route.

You then have good adjustment in the cam overlap without needing to replace the cam, you can run a reasonably high CR with the turbo setup, and run a decent amount of boost through it. If you run a plenum and single TB onn the N/A setup you'll make it easier for yourself to turbo, and get the right size injectors, the only thing you'd need to do is bolt the turbo on, and adjust the fueling and ignition on a laptop

Of coarse the major draw back is the building of the engine in the first place. But once its built, it could be quite a diverse engine.

Edited by matty on 30th Nov, 2011.

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1/4mile in 13.2sec @ 111 terminal on 15psi

Altough I agree with Matty says, there are 2 dividing line beetween these 2 aspect of the build.

The question you have to ask yourself are :
How much you can spend on the build ?
How long you intend putting in the build ?

Some of the time you spend can make the bill less painful but there is a price to pay.
And to be fair, starting with a 998, for the same kind of money you will have to spend, you can get yourself something like a Golf 3 VR6 who would probably as fast, not to mention the size of the boot amongst other features.

Anyway, I digress.

A turbo 998, built on the cheap still needs almost 1K£ for 100 HP.
You can get to 150 hp but you will need more money (I assume you do all the work yourself, including exhaust collector and you can grab some bargains here and there).
The more power you expect, the longer the build so if there is a dead line, work backwards from there.

Also, the 100 HP 998 is the one requiring the least mods done to the gearbox (more money saved)

On the other side, in the marvellous world of the cost no object builds, you have the K head wich as Matty says can give you the best of both worlds either turbo or N/A.
It does so at a price and related build time.

To be honest, I bought my mini late 2002, started stripping it down looking for more power and projects.
2012 in a few weeks, the car is just about to hit the road as a bog standard stage 1 998.
Maybe it's just me being so slow (not available to be true) but I wish I rode it standard back then and upgrade a few things at a time.

I would say, aim for a 90ish turbo 998.
It will be faster than a 90ish N/A 1275 and potentially the same price.
If reverting to N/A, change the head.
That is a big if because it is aid by the wise "once you go turbo, you can never go back"

Rusty by nature