14 replies to this topic

[mic]

yes i have searched both here and TM

so i understand the T3 were metros original turbo. i also understand people say its not as good as a T2 due to amount of lag. by all means correct me if i miss anything of am wrong.

1. im guessing theres a reason as to why they used T3 in the beginning as opposed to a T2?
2. what actually causes 'lag'? not sure how a turbo unit works.....
3. is there a way to cure/beat/cut down on lag?
4. boost (or psi). its ok saying a T2 is good for 180 BHP - does that mean a T3 isnt?
5. if a T2 kicks in at lower revs than a T3, is this a big range difference i.e. T2 at 2000RPM and T3 5000RPM? (figures used hyperthetically)
6. would choice of cam alter performance accordingly with use of T2/T3 (as in are some cams better suited for each turbo)

i am aware some of these may have been answered already but thought it might be nice to have 1 post covering the basics rather than lots of posts!

cheers

mic

[mini25]

the t3 will give more power but higher up the rev range so u have to wait for the power to kick in,

the t2 will give less power but through a greater proportion of the revs and so is more user friendly

on a small bore engine u need to use smaller turbos as a turbo works by air flowing through it, and small bore engines dont flow that much air, so if u smack a big turbo on it ull need silly revs to make it work, and there will be wheel spin all over the shot the moment it does!

the lag is caused by the turbo having to 'spin up' the bigger the turbo the more air that has to pass through it to get it to work

u cant beat lag unless u use a supercharger or turn down the boost or run a smaller turbo, thats it, unless u can get one of the funky turbos prodrive have made that is half way between a turbo and a charger

hope this helps

Edited by mini25, 29 March 2007 - 04:03 PM.

[rollin on 13's]

things such as fitting an intercooler will help with turbo spooling up time. also chosing the right cam will do wonders on the power band and will also help the turbo. also compression ratio will also affect the turbo, ie to low compression well mean it be really slow off the start but as soon as the turbo kicks in ur be away. running slightly higher compression will help with the off boost performance. i believe the t2 kicks in about 800 to 900 rpm earlier than the t3 but then looses power quicker too.

to be fair a well set up tuned up turbo mini running a t3 will be spot on as you can gain more power out of it.

But ive also heard the other side of things once you driven a t2 then you will want to change yours, however i cannot comment on this only pass on word of mouth as i only own a t3 mini

[Turbo Phil]

yes i have searched both here and TM

so i understand the T3 were metros original turbo. i also understand people say its not as good as a T2 due to amount of lag. by all means correct me if i miss anything of am wrong.

1. im guessing theres a reason as to why they used T3 in the beginning as opposed to a T2?
2. what actually causes 'lag'? not sure how a turbo unit works.....
3. is there a way to cure/beat/cut down on lag?
4. boost (or psi). its ok saying a T2 is good for 180 BHP - does that mean a T3 isnt?
5. if a T2 kicks in at lower revs than a T3, is this a big range difference i.e. T2 at 2000RPM and T3 5000RPM? (figures used hyperthetically)
6. would choice of cam alter performance accordingly with use of T2/T3 (as in are some cams better suited for each turbo)

i am aware some of these may have been answered already but thought it might be nice to have 1 post covering the basics rather than lots of posts!

cheers

mic

The reason BL used the T3 was because they didn't have the range of Turbos available, that we do today. The T2 didn't exist for a start.
The Turbo is basically an exhaust driven compressor, the larger the exhaust turbine the more gases it takes to get it spinning {more lag}, but ultimatley being able to flow more {higher power}. A smaller turbine obviously taking less inertia {less lag}, but not being able to flow as much.{lower power} So it's a case of trying to match the Turbo to the engine.
The Renault 5 spec T2 is spot on really IMO, my motor made 184hp on one of these. Though after 6,000rpm the power falls flat on it's face with this Turbo, and boost becomes inefficient above 16/17psi, even with the huge alloy intercooler i run.
It would probably have made more on a bigger Turbo, but i like the drivability of the smaller unit.
Running a well matched Turbo, optimsed ignition timing and as high a compression as safely possible will all help reduce lag.
I've run a stock T3 and it came on boost properly around 3,500, the T2 comes in around 2,500.
The best Turbo cams have little overlap, but a big exhaust duration. The Avonbar P2 being a popular choice. The normally aspirated MG metro cam is also good.

things such as fitting an intercooler will help with turbo spooling up time.
To be fair a well set up tuned up turbo mini running a t3 will be spot on as you can gain more power out of it.
But ive also heard the other side of things once you driven a t2 then you will want to change yours, however i cannot comment on this only pass on word of mouth as i only own a t3 mini

Fitting an intercooler will, if anything, increase lag as the compressor has the intercooler and associated pipes to fill before the compressed charge reaches the inlet.
You may be able to gain more peak power running the T3, but on the road while you're waiting for the T3 to come on boost a T2 would be on boost more often and be much more driveable.
I know of lot's of people , myself included, that have moved from a T3 to a T2. I do't know anybody that's gone the other way. I think that says it all.

[josh_tacon]

phil is that 184 bhp with a standerd t2 off a r5 gt turbo or is that a hybrid type?
im going to use a r5gt turbo (have it waiting to go on) but after the engine is run in and iv saved the money im planing on having it hybrided by turbo technics in northampton as iv heard there the dogs ******* for turbos etc.

turbo motors dont usally rev more than 6500rpm anyway do they? so surly your not realy loosing anything by using a t2 rather than a t3?


cheers
josh

[stevenford_uk]

i would stick with the T3 mate more scope for power and once the turbo kicks in properly its highly addictive, the torque steer and sledgehammer in the back the T3 gives is soooo much fun IMO its the best way to go as your not building one of these cars to pootle round at low revs, give it stick and its on boost and ready to rip your face off.

[Turbo Nick]

T2 all the way for me, my mates running 160hp @ 15psi with a std R5 T2, i've got a T25 ready to go back on mine and will be looking for similar amounts of power seeing as we almost have the same engine specs now. We wound his up to 18psi at the weekend and its just unreal, stupid fast.

Once you've driven a mini with a T2 you'll wonder why you didn't do the swap earlier, it really is that much better. No more waiting for the boost to kick in at 3k its just there almost straight away, makes the car a lot more driveable and a lot smoother.

[josh_tacon]

bud does it kick you back in your seat as much as the t3? or is it about the same?
im planing on using a T2 standerd at first then once the engine is all run in and im looking for more power (as you do!) ill get it hybrid so it should cope with upto 25psi! or maybe more if its possible?
i carnt wait!
does the renalt 5 unit run 10psi standerd?


cheers
josh

[Turbo Nick]

you dont get as much of a surge as you do from the T3 i've found, its just a lot smoother no sudden bang and its there if you get me.

[Leonard]

I've heard rumours that the standard renault5 T2 doesnt cope with over 12psi for very long? seeing as some of you run above this, can you confirm or deny this? maybe its only when on the r5 engine.

[Turbo Nick]

well after the weekends 18psi adventure on my mates its smoking a little now, lol. He's got a new one on the way though thats why we wound the boost up.

[josh_tacon]

but does it still pull you in your seat??
what rpm does it come on boost on your engine bud? and when would you say it drops off?


cheers
josh

[Turbo Nick]

its not really got a set rpm that it comes in at, it just spools up a lot quicker. if i put more gas on at 1500 it'll start going then it'd be at full boost by 2500 maybe, can't say for sure as 5psi is all i've been running while i've been sorting out my smoking problem. i haven't had it run out of puff either, my limiter kicks in at 6500.

as for putting you in your seat, mine doesn't on 5psi but my mates is crazy.

[Turbo Phil]

phil is that 184 bhp with a standerd t2 off a r5 gt turbo or is that a hybrid type?
im going to use a r5gt turbo (have it waiting to go on) but after the engine is run in and iv saved the money im planing on having it hybrided by turbo technics in northampton as iv heard there the dogs ******* for turbos etc.

turbo motors dont usally rev more than 6500rpm anyway do they? so surly your not realy loosing anything by using a t2 rather than a t3?


cheers
josh

Mines a T2/T25 hybrid. But it's the exhaust side that's restrictive on mine really. Once the backpressure mounts the power tails off rapidly. Mine will bounce off the rev limiter, which is set at 7,500, very easily but makes no more power after 6,000.
I don't think i'll ever go back to a T3, the power spread with the T2 is so much better.

Edited by Turbo Phil, 18 April 2007 - 10:25 PM.

[redwing2]

but does it still pull you in your seat??
what rpm does it come on boost on your engine bud? and when would you say it drops off?


cheers
josh

I did manage to hitch a back to back ride today. 2 x 1275 minis on a standing quarter. Everything said here about T2 is true IMHO but... the T3 produced the suprise kick in the a** when it comes in at about 3500 rpm and runs mcuh better through to 7K. The T2 seemed to 'gag' at around 6K. Both ran about 12 psi with standard metro cams. The T3 was using a better DV in my view. My car will be running on the standard T3 (without the ECU).