Has anyone any experience with machining out the standard 4x4 T3 compressor housing to take the T34 compressor wheel, to produce what i guess could be called a T3/T34 hybrid?

Is doing that likely to produce a more responsive turbo than using a real T34 cover?

I've been doing some reading trying to figure out exactly how responsive the T34 turbos are compared with the T3, but i'm not finding that much data. Some folk seem to think its "laggy" - i know this is the wrong term, and others seem to think its great. Obviously with this sort of thing its relative to what else you've used.

I found one mention in a post years back that the combination of the T34 wheel in a T3 housing produced "full boost" from as low as 2700rpm and was more responsive than a real T34.

I've also found some mention of a T34-48 managing to produce >20psi by 3100rpm, is this generally regarded as the norm, or was that a bit unusual and they typically take longer to get going than this?

If anyone happens to have a dyno plot from a T34.48 or a 4x4 T3 with T34 wheel i'd like to see them!

Cheers
Kev

 

My new spec see's me using a T34.48 purly for the fact I can get reasonable power without not much more lag than a T3.

 

Yeh, i'm just trying to get a handle on how much "not much more lag" actually is.

If they can genuinely hit 20psi by 3k as some of my reading suggests then fantastic. If its more like 3500-4000 then its less so.

I'm also intrigued as to using a T34 wheel in a modified T3 housing, as it could work out a fair amount cheaper doing that than trying to find/buy a T34 and if it makes it even less laggy then all the better.

 

iv got a t3/t4 hybrid for sale built by aet turbos .48 housing

 

my t3 had a 34 wheel machined into it by The Turbocentre. i don't know how the lag compares to a T34, it just made sense to go for the upgrade while it was being rebuilt.

does look standard, though, which i prefer

 

Bloomers: Whats the boost threshold like?

IE if you were to stick it in 3rd or 4th at 1500rpm and go full throttle, at what point do you start to see positive boost, and at what point does it get to say 10 and 20psi?

Cheers

 

depends on setup mine its 25 psi around 3000 rpm and holds through to around 7000rpm
going for a t35 .63 so a little more lag to come ( just drive it harder )

 

Thanks paul, its good to know that it really is possible to have these turbos producing good boost by 3k.

Will be interesting to see how Bloomers T3/34 hybrid compares.

To give a little more info, i'm thinking of using one of these on a different engine (VAG 20vt). Given its only 1.8L its going to spool slower than the YB, although i'm hoping that the fact it has a better cylinder head will help counter the reduced capacity. If a YB can hit full boost by 3k, then i'd imagine at worst i'll be 500rpm behind, which should be acceptable.

I do a lot of motorway driving, and what i dont want to end up with is a car that has LESS power than a standard engine at motorway speeds. I know if i want to properly accellerate i can drop it into 3rd and i'll be off, but what i also want is to keep as much power as a standard car around the 3k mark where the engine sits on the motorway.

I've noticed that some Bigturbo 20vt builds using big GT30's and the like can make 20 or 30hp LESS power at 3k than a completely standard motor, and its this i'm trying to avoid.

As it stands, i'm trying to decide between a T3 from a 4x4 (either with or without the T34 wheel) or going to an actual T34. I Know the 4x4 T3 will give me what i want, but i'm hoping that either the T34 wheel in a T3 housing, or a complete T34, will give me a bit more power potential at the top end, while still meeting my desire to have at least standard power at 3k.

Cheers
Kev

 

Bump.

Any more experiences with these turbos?

 

not sure what you mean by threshold, bud. only put mine back on the road yesterday, so it was hard to say when it starts building.

from driving yesterday, i'd say it starts building from 2.5k. i know if i throttle it with the revs held at 3k, its off like a stabbed rat

hope that helps, i really should pay more attention :S

i'll take it down the bypass tonight and see what it actually does

i'll take at look at my power charts for you an see what it was making at 3k on the rr, too

 

Boost threshold is the rpm at which it starts to make positive boost, accelerating from low rpm (1500rpm for example).

Lag is the time it takes to get the boost when you are off throttle, in the turbocharger's working rpm-zone, and push the right pedal to the floor.

 

Is it common to have turbo surge with t34.48. Last spring i tried everything to overpass this trouble ,but nothing helps.

Surge occurs in motorway speed cruising ,when engine not need much boost. That t34.48 Charges very early ,almost like stock t3. It's like engine can't swallow all that air.

Car spec: Sierra Cosworth 1988 2wd ,ported head ,4wd inlet manifold,803 greens ,MSD evolution chip, GReddy PRofec B-spec Boost Controller, rs500 style IC , 044 bosch and 2.5" exhaust.

i tried adjustable cam pulleys ,fuel pressure changes ,AFR changes ,Other 803 green chips ,Two different ECUs ,MAP sensors ,new pf09 TPS and other sensors ,but nothing helps. Bad turbo surge and that's it.

And it's really a turbo surge. Not air striking back to compressor trz,trz,zzz noise ,when release gas pedal Dump valve works very well.

Stock T3 is now in place ,but i want little bigger turbo. Is t34.55 or .64 good choice. I think it can't surge that easily like earlier .48

Some friends in our own Cosworth&rs club forum in finland says that 3" downpipe may help? but i'dont think so ,because no surge in full throttle.

 

If you could post the graphs that would certainly be useful! If not then even an idea as to when it goes positive (ie when it starts making >0 on the boost guage) and when it gets to say 10/20/max boost.

Cheers
Kev

 

My Graph

driving down town in a min, will make a note of where the threshold is...

 

drove it last night, positive boost build from just below 2250 rpm

 

Thats pretty impressive, 135hp by 3k!

Seems a reasonable way to go then. Spools more or less the same as a standard T3 by the looks, but manages to make 360hp!

 

mines got a nicely balanced bottom end, and a lightly ported head, but makes good power for the spec.