T3 Turbo Considerations
Turbo Mini Forums

I've seen it written that the original T3 that came with the Metro Turbo has too much lag, and going to the smaller T2 or T2.5 is the way to go. However, when I drove mine, before the tear-down, I did not note an excessive amount of lag.

With the mods I'm planning (8.3 to 8.5 compression ratio, custom header, ceramic coating and wrapping header, and reflective and insulative coatings on the head), does the T3 become more of an adequate choice? Or do you all think I should look for a smaller turbo that can spool up quicker?

I'll start with the T3, of course, because it's what I have. I'm more looking for opinions from those that play in this area, than anything else.

Cheers!

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1967 Cooper 's' Turbo build @ www.drjing.com

It all comes down to how mauch power you want!!

T2 are good to about 140bhp... IMO after that you are looking at hybrids or just sticking to the good old t3!

I run about 8.5:1 with a big head on std eninge (track fun only not road)... but the lag is not a problem!

Alex

AlexF

so how do you explain how TD gets much higher than 140 on his T2??

not only that but quick 1/4's etc with a very lardy car compared to most

very good intercooler setup :p

Note I didnt say 140 was the limit... but thats when a t2 on our engines drops off the good parts of the compressor map and the result you can easily see and measure is the ACTs shoot up!

alex

AlexF

ACT's??

C'mon give us a clue?!

I am guessing something to do with air temperature here?

Air Charge Temperature (I cheated and asked my WRX buddy what that was).

Thanks for the info, guys. So, it seems that the T3 is definitely rated for higher than the T2, all things being equal. I guess I'm concerned with lag, right now, based on my engine's spec. Since I'm keeping my EGTs as high as possible, I should get good velocity through the turbo. But is it enough? That is the question... I guess, barring someone's experience with my setup, I'll just have to post my results. Of course, I'll keep my website updated with my goings-on, so any experimentation I do will be there as well.

Thanks, guys!

**************************************
1967 Cooper 's' Turbo build @ www.drjing.com

sorry Tom!!

Air Charge Temps

Jargonises infected I'm afraid!

alex

AlexF

Ask your WRX buddy form some anti-lang (bang bang) ideas!

AlexF

Well then I have an idea for anti lag......

Uses a very small nitrous system to provide 10 bhp max worth of nitrous when the engine is off boost and at full throttle opening.

That injection of N20 rapidly increases the amount of molecules impinging on the exhaust turbine in the turbo. Due to that, the turbo should be 'driven' onto boost maybe 500rpm before it would usually produce boost. In addition to this, once the turbo is producing boost it is self sustaining as the denser air being pushed in is then pushed out back to the turbo. Also, the injection of nitrous low down gives increased torque before the turbo kicks in. Once the inlet plenum detects boost then the nitrous is turned off......
So what do people think of that idea? I reckon it could work, although I don't really like the idea of nitrous, I suppose that only using a small amount should not really hurt engine components.

Alex, when are you going to give up on this T3 bull?

Pull out the compressor maps for the metro T3, assume the 0.25 turbine housing, and then compare to the R5GT spec T2...

I haven't done this, i don't believe i need to - because i've driven and experienced enough of both types of turbo to know there is probably very little in it powerwise, other than the driving sensation...

As regards my intercooler set-up, i ran a few sub 14's on a stock RST intercooler...
Go and measure the T3 air charge temps at different boost levels - a little 40 trim compressor will soon have them over 120 degrees once you wind the boost up.


Anti lag?

Why?

oh Jon, in reference to your question...
The T3 doesn't really suffer from lag, more a high inertia...
The small 0.25 turbine (exhaust side) ensures a sufficiently high turbine speed, and that it spin up as fast as possible for our small displacement engines.
All i'd advise if you want to retain the road manners is to use a stock or very mild camshaft... MG Metro / Kent 500 is a good start - the SW5 if you can afford one!

I also keep my inlet and exhaust ports small - only slightly larger than the stock MG turbo head ports. The ex manifold can't be ported, so why bother doing the head to extremes?.
You'll gain a lot by matching the exhaust manifold ports to the head however - there is usually a big offset here. I can't comment on ceramic coating - having never felt i've developed the A-series enough to warrant going to that level of detail. Can't do any harm, but for me it's comaprable to the icing on the cake; and i'm still trying to get the main ingredients right!

Edited by turbodave16v on 15th Sep, 2004.

Dave's success is due to years of in depth developement, a sorted ignition set up and being a perfectionist, amongst other things.

Shave 150kgs off Dave's car to get it to a comparable weight to mine and then send him up the strip!!

Oh anyone witness my "lag" off the line a Silverstone on sunday with my T3 that has been modded to give more lag than a standard 0.25A/R item...no!

What's the fuss?

Thanks, guys.

Dave, my budget won't allow me to get too many parts, other than what I have. So, I'm going to use a 1.3 rocker set with a 286 cam. Hmm, porting hadn't been much of a consideration, because the head is so restrictive in the exhaust ports near the valves. I've opened them up, but hadn't planned on doing much porting. I do, however, plan on getting some madrel bent tubing and making my own exhaust header so that it goes over to the turbo mounted above and behind the clutch. Loads more work, but it will prevent the need for a bulkhead cutting, and should be better than the stock manifold!

I'm really enjoying the work of putting this together! I hope that some day we might all meet and compare notes!

**************************************
1967 Cooper 's' Turbo build @ www.drjing.com

Stock manifold is a trick bit of kit!

yeah i think we should of took some bits out of daves car at avon and seen what happened.

ive witnessed both cars, both completely different, it has to be said but both very effective hopefully i can get mine half as good

I'll give it up when I see a t2 at over 140 bhp not running off the efficent part of the compressor map :tounge:

The t3 begins to hit the sweet spot at about 140 bhp.

As for anti-lag... why not, it sounds good lol.

I agree with jf on this, if you keep the revs about 3.5k, which isnt that hard, then were is the problem?

alex

AlexF

I am more interested to try out the nitrous idea just to see if I could make it work really, the lag to me is all part of the fun of having a turbo....and all the more fun when boost DOES start.....

Right, and a 40 trim T3 is STILL on the efficient part of the compressor map when driven with a 0.25 turbine at 140hp???

Edited by turbodave16v on 16th Sep, 2004.

Jing, would'nt go for a 286.

Bit racey even in a road car.

IMO.

Oops, typo. I'll be using a 266 cam... Sorry for the confusion.

**************************************
1967 Cooper 's' Turbo build @ www.drjing.com

excellent choice...