998cc turbo project
Turbo Mini Forums

Hi guys, last year to earlier this year I have converted my standard 998cc engine from the old SU hif38 to an ms3x port injection, with a lot of help from this forum, especially from Paul S. After getting the AFR's almost balanced I had to dismantle the engine to replace the clutch and is currently doing some restoration on the bodywork as well. Since I have the engine and subframe out I'm thinking to turbocharging my engine when it is back in (I'll try to fit the engine in next week or the week after).

Currently I know only very little on turbocharging the A-series. I know that the T3 is not the best option however it is the cheapest. In some threads I have read that there is a GT1752 and the turbo from the Renault 5. Is that right ? And are there any other options ? Somewhere in this website I have also seen a thread about chinese turbos, how do they perform?

Obviously budget is an issue. The more the cost effective solution, the better.

Any help is greatly appreciated. My aim is to get mild boost but preferably at low RPM's as I drive the car on the road.

Also with regards to fuel injection, I know I have read somewhere that the standard MPi manifold (which I have installed) would need to be modified to have staged injectors, however that is as far as I know.

Thanks in Advance

Forget the t3 and gt17 for your application. Gt1548 or ihi rhf 3 or 4 is what you want. There are other choices. But keep it small.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

From where is it possible to buy a reasonably priced GT1548 ?

I've just built a 998 turbo (not started her up yet) after LOTS of research and cost effective concerns I settled for the IHI RHF 4, the RHF 3 might be better for faster spooling and quicker boost on a 998 though. I'm afraid I can't comment on how it performs yet! Still need an afr and to plumb the exhaust up..

Hey mate... may I ask on what the IHI RHF 4 is fitted originally ? I found that they are fitted to a Peugeot diesel. Is that true ?

Just bought a GT1549 for the 998cc. Do you think its a feasible option ?

And regarding compression ratio, my engine is completely standard. Would I still need to lower the compression ratio ? Somewhere I read that the original 998cc had a CR of 8.0:1. Is this sufficient for around 8psi boost ?

I know nothing of the GT1549. Got any liks to what it's off?
EDTI: just checked, the GT1549 is used widely on 1.9 and 2.0 diesels, so likely a decent size for a 100bhp mini. It will need a bespole manifold though.

CR varied widely over the course of their production: from 8.5 to 10.5:1, so you need to know what engine you have.

Edited by wil_h on 18th Jul, 2016.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

For atound 7psi of boost what is the recommended CR ?

9:1

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Wouldn't it be smart to rebuild that 998 first? It geels like you will just bolt it on. But putting allot of stress trough it by turbocharging it. If it were me i would at least want to know how the bearings and other parts look.

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018

The engine was rebuilt last year by myself, and it sat in the garage waiting to be mounted on... however suring rebuilding I never thought of turbocharging it to be honest... thus I don't even know exactly its compression ratio, but I will do an experiment to find it.

Easy calculated. Mesure volumes set in formula and you have static compression.

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018

So today I dismantled the cylinder head from the block and calculated the swept volumes and unswept volumes by pouring oil with a syringe. The compression ratio I calculated ranged from 8.0 to 8.5.... I've done the ecperiment twice. Is there an alternative route maybe to be more accurate ?

Get a sheet of thin clear perspex - I use the lid of an old CD case - and drill a small hole in the centre and lightly grease the cylinder head face/block face so the perspex sticks to it.
Use something thinner than oil, I use parafin or even water, and by filling through the hole you can (a) see when all the air is out and (b) the perspex stops the meniscus of the fluid affecting its level.
And dont forget to include the head gasket volume in the calculation.

Schrödinger's cat - so which one am I ???

Thanks mate I'll redo the experiment then

So I have done again the experiment. Used engine oil, diesel and water as fluids. The cylinder head cups seem to be 24ml and the pistons 7ml. By calculating the CR it cokes 8:1. Is it normal ? I'm seeing it a little bit on the low side.

So I have done again the experiment. Used engine oil, diesel and water as fluids. The cylinder head cups seem to be 24ml and the pistons 7ml. By calculating the CR it cokes 8:1. Is it normal ? I'm seeing it a little bit on the low side.

So I have done again the experiment. Used engine oil, diesel and water as fluids. The cylinder head cups seem to be 24ml and the pistons 7ml. By calculating the CR it cokes 8:1. Is it normal ? I'm seeing it a little bit on the low side.

Not a specialist by far. But that sounds acceptable. Had one like that to with dished pistons. Mesured the bowl and ringland etc? Presume yes.

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018

Have you include the volume added by the head gasket ?

An accurate measurement of the head chamber and piston dish isn't the final answer.

Schrödinger's cat - so which one am I ???

I haven't included the volume of the gasket, but that I believe reduces further the CR since it is an "unswept volume" isn't it ?. What is tje best method to measure its volume ?

Yes, the gasket reduces the CR hence a lot of people adding "decompression plates" or even more shamefully, two gaskets, to get the CR down.

There are some quoted volumes on the web but simplest is just measure the thickness of a used one at the fire rings and the diameter of the hole. Most 998 gaskets aren't actually round but you can get the average diameter then it's just Pi*(r^2)* thickness to get the volume.

Schrödinger's cat - so which one am I ???

So today, the GT1549 bought arrived and tried to begin planning on fitting it. Its quite a little bulky to be fit, but I'll think I manage to fit it just below the firewall cross member.

With regards to fitting it are there any guidlines I should follow or be aware of ? So far I know that the turbo should be positioned above the "max" mark of the dipstick to let the oil from the turbo drain off to the sump. I also know that the exhaust runners should be preferably equal in size.

With regards to oil feed I was going to use a tee off the pressure switch, and since I'm positioning the turbo a little bit downwards to save the cross member from being cut, I was going to use the blanking plate seen in the attached photo as the oil drain.

Is it a good spot to drain off the oil from the turbo ? Else I would use the place of the mechanical pump, that would be as much as the same height as the turbo shaft.

Thanks in Advance

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Thats plea has the oil pick up pipe on the other side. Return it somewhere else or you'll be feeding the oil pump/crankshaft etc hot oil.

Have a read here, lots of useful info

http://www.turbo-mini.com/4598.html

also search on here for manifolds for inspiration.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk