It IS an R5 Turbo, what now?
Turbo Mini Forums

Just got the turbo off the manifold, and stamped on the inside is 35.

So turbine A/R of 0.35
and
Compressor A/R of 0.48

It's an R5 turbo. So now where do we go?

Wil

Edited by AlexB on 3rd May, 2006.

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

Ho hum. Maybe looking at turbine inlet pressures may be a start, to see if the small turbo is choking the engine? Or how about checking the turbo outlet pressure to see if it is something daft like a restriction in the exhaust?

measure the pressure of the two and compaire the pressure drop across the engine...

this will tell you a fair bit about whats happening!

Alex

AlexF

Well,

This is interesting...
I didn't get a chance to do the T2 plots last night though. Will try tonight.

Head changes are certainly do-able at a RR session hey Jon

would certainly be the best way to judge any gains etc.

Thanks to TD for these. He supplied the info for the T3 and I just coppied his figures into the other maps. I think the T3 is going back on. Still no maps for T2s available as far as I know. Not easy to see, but the yellow lones are 18psi the red 15 and the green 12.

Edited by wil_h on 4th May, 2006.

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

I think you should persist with the T2. It could be something else. Whatever caused the head gasket to blow could have been part of the problem.

If you go back to the T3 you will still have the problem of a lack of power below 4500 rpm. If you look at the compressor charts above for the T3, you can estimate that below 4500 rpm you will be operating to the left of the surge line - not good.

If you want more torque lower down to give a better launch out of the bends then the T2 must be better.

But why your dyno results are poor is still a mistery.

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."

I still think the T2 is the way to go. We need to see the T2 map before making a decision. Putting the T3 back on should at least get us to where we were and see us through the season.

The only real way forward is get a hybrid, but that is for the future.

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.

At least if you put the T3 back on, it will confirm that it is a turbo problem and not something else.

You're not running a radical cam are you????

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."

i know pretty much nothing about turbos, but isn't there a middle ground?

What's a t25, is it bigger than a t2?

The trouble is that the T25 units have a larger frame turbine than the T2's and there is no way a 998 will spool a T25 adequately...

This turbo map looks good - but once again garrett are being very annoying in not supplying the fitting that is needed (IE a 4-bolt flange) for the turbo to manifold interface).

http://www.turbobygarrett.com/turbobygarre...44_454083_2.htm

I'll work throgh some more specs for you based on 'budget' turbo's...
First thing is to see how the vehicle actually drives compared to the T3. If you're able to gain from acceleration despite the apparant power loss, then you'll either decide of the T2 frame is - or isn't for you; also considering the financial aspect.

That T3 map is bloomin' perfect for your 998 though. If you could get that compressor on a T2 frame......

If we cannot get a map for the T2, with some dimensional data from a T3, I could calculate one using the affinity laws.

If we could get hold of the dimensions of a T3 compressor of the same A/R ratio and measure the inlet diameter, the outlet diameter and the outlet width, we could derive a scale ratio and work from there.

It's a well proven science.

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."

I've looked at the T2 map - and it's suprisingly un-suited to the boost and RPM that Will and Ben are after.

The 60-trim T2 compressor increases flow, but drags the surge line over with it - and is very un-suited to the 998.

I'm going to shuffle through the T25 maps and see how they look - at least you can build something with that combination of bits.
I definately think that the 0.35 turbine should be retained though, so this will be a hybrid for sure.

Edited by turbodave16v on 4th May, 2006.

Dave,

If you have a T2 map can you share it with us?

A lot of us are investing a lot of time and money into 998s with T2s - we need to know if this combination is not going to work.

I have a R5GT T2, same spec as Wil/Bens. It sounds like this is not going to be any good at all on a 998 in a road car.

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."

This is the only T2 compressor map I can find


It suggest that it should be running out of puff by the time it gets to about 100kW/133 hp.

But it should be able to maintain boost from 50 hp upwards.

Is the problem with the turbine, not the compressor?????

Edited by Paul S on 4th May, 2006.

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."

i think yuoll find the t2 inlet size is about 33mm ,this would make its flow comparable to the gt15 above with its 32.9mm inlet. ,with a little less pk efficiency , .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

yes pete ,althugh i feel it'd get to 20 ok ,maybe 22 in a small window ,its what i should really be using on my bike ,but its not free and the t25 was ,also it made such an interesting challenge to get the boost in at 3800 on a 500cc engine , looks like wils engine is going to be another factor than the turbo with the compressor hes got it should be fine ,if the engine itself is exactly the same barring head work ,id start to look at manifolding ,or chamber shape ,if its been de beaked than could well make it less octane tolerant, ,and check usaual periferals like timing mix etc , time will tell im sure , i do feel for the chap thuogh , i remember having a freind come to me and put his astra on my rolling rd ,and it should have had 90 bhp ,and it had 25at the wheels!!! losses were 55
!! looked at the front wheel to see what i thuoght id see ,front brake glowing bright orange ,his little face on a 25 bhp picture was totalement chagrin ,poor bloke ,its not fun when you spend all that time and money ,but im sure wil ben will get it fixed .regards robert.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

:)

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

So I have a T2 map AND would also be interested in finding out how you did that aswell...

Potential for a mutual Exchange of information?

or just post your t2 map dave :p

I've lost mine :(

Alex

AlexF

Exchange of skills / knowledge. I have something someone wants, They have something I want. Simple.

thank you for your generous offer dave ,i dont feel that my theories compare in value with your t2 map ,and feel i had taken unfair advantage of your kindness.incidentaly i feel that to all intents and purposes ,a gt15 map with the same inducer proportions would give a very similar map ,so to preserve the exclusivity of your t2 map then maybe put the gt15 map up and that would help wil and ben without exposing your technical resources ? regards robert.

Edited by robert on 5th May, 2006.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

lost me.

so exactly how many degrees of total timing would that be then?????.

carl

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

lol
you made me burst out laughing so loud carl that i think i woke the neighbours ,thank you .

Edited by robert on 5th May, 2006.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Back to Topic!

My theory, for what it's worth, based on zero practical experience but a lot of engineering experience with rotodynamic machines.

I have been worrying about this all week because I am worried that the pile of bits accumulating in my workshop is not going to work.

Despite the lack of a T2 map, I do not think the problem is directly due to the turbo.

Anyway, i think that the problem is more than likley the cam.

The smaller turbine of the T2 will create more exhaust pressure than the larger T3.

During overlap the exhaust back pressure is preventing the cylinder from filling. This is further compounded by the lack of any inertia in the gas flow due to the ported head.

As you say, the engine is coming on boost earlier in the rev range but it is not producing any more torque.

Eventually at around 7000 rpm it is producing the sort of torque we would expect. I think this is due to the inertia effects of the gas flow overcoming the back pressure.

If you are using a Ph2 cam, then it would probably be better to use an SW5 or even a standard turbo cam (not the MG).

Is this bollocks or what?

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."