Best suited turbocharger

What are peoples opinions on the best suited turbo size for a GTA? Basically mine is a bit worn and letting some oil through into the plenum etc so I'm wondering about a replacement.

Standard boost at the moment, but with an eye to say 15psi maybe as an upgrade what's the best compromise in terms of size, AR ratios etc and what's the boost threshold / lag like.

David and I were chatting about this last time at the Ace in reference to his t3s and t3/t4. It's a tricky one because obviously boost volume is what counts (not necessarily pressure) and a big turbo spools up slower but is already pumping at lower turbine speeds and cooler so all is not always as it seems

Life's choices are never simple are they?

Not sure what the answer is but I know a friend of mine replaced his standard unit with a T3 hybrid. I believe this is basically a T3 body with slightly larger impeller/fan. Essex Turbos provided him with the unit as an exchange - dont know the cost but possibly could find out. He also fitted a thingy in the engine bay to alter his boost level and opened up the standard silencer removed all the insides and refitted it.

His car seems to be a lot more fierce on acceleration but I recall he still maintains a serious amount of turbo lag.

I do know that when he accelerates hard up to this roundabout close to his home you can see flames out the exhaust when he lifts off

I would always sacrifice extra grunt for less lag I'm not putting it down the strip . After driving the Atmo for a bit you get to love the instant response and once back in the turbo it's a let-down




for a while ................ till you turn up da booost

Its hard to take judgement on other people's cars as they are all set up differently, for instance, you may go out in a car that has a 'hybrid' and punches harder, but it may simply be running more boost, or have a new actuator which is better at holding boost.

The standard turbo is at its limit even at standard boost.

The Stage 1 unit will have almost the same spool up as the original but the compressor wheel is much larger, as its a T4 wheel - it runs cooler and will flow more at peak revs.

The Stage 2 is the same, but with the larger exhaust housing. This makes the physical engine breath better and combined with more flow from the large compressor wheel makes more power. More in, more out.
This is beyond the spec used on the Europa Cup GTAs

Ive ran the larger turbine housing on my own car, and didn't notice any significant lag difference, if anything, the engine felt less choked off boost.

Both these turbos compressor wheels can flow enough lb/min for 400bhp, so the compressor side will never be lacking.

The T3/T4 hybrid will be replaced with a more modern Garrett GT series turbo, but will require a new downpipe.

I would always sacrifice extra grunt for less lag :

No easy way round it on the GTA. The turbo is very small to begin with (same size as on the Escort RS Turbo) and it is still laggy. The reason why is because of the cam profiles and length of the manifolds. Because the exhaust valve is only open for 48 degrees of the camshaft rotation, there is not much gas speed at low rpms to drive the turbo, and because the cams are chain driven and the pulleys fixed, its not like you can advance the cams manually to bring the exhaust valve in earlier as you could on say a Renault 5, or 21..

My celica had a twin entry turbo does anyone know if one can be fitted to the gta as this helps stop lag etc

lag wouldnt really bother me as my old 5gtt had a t28 and was laggy and i loved the way the power kicked in felt as if it had about 400bhp but down the twisties it was harder to keep on boost still didnt get beat by much

My celica had a twin entry turbo does anyone know if one can be fitted to the gta as this helps stop lag etc

Yes, Im working on this at the moment...

On my high power V6 engine build I have purchased a high specification Garrett GT series twin entry turbo(twin scroll), with a larger than standard compressor side and exhaust turbine which is specced for 520bhp, but I have tubular manifolds which each side leads to each scroll on the turbo.

This could be fitted to the standard GTA (if you don't retain the heatsheilds) Basically, twin scroll (for those who dont know) means, that instead of all the gasses from each cylinderhead banging into each other when they meet the turbo, they stay divided right up until they meet the turbine wheel, and the gasses are parallel to each other when they meet, instead of opposed..

Much better at high rpms and better for lag, and it has a 2.75" exhaust outlet too instead of the crappy 2" outlet on the GTA exhaust system..

Price is around £650 for the turbo and this will flow up to 420bhp, and is far newer technology than the existing Garret T3/T34/T38 range..

lag wouldnt really bother me as my old 5gtt had a t28 and was laggy and i loved the way the power kicked in felt as if it had about 400bhp but down the twisties it was harder to keep on boost still didnt get beat by much

Same as mine, at 4k it hits you hard and you just keep smiling rite round to 7000+ rpm

i think to be honest you only notice lag for a few days then you get use to it! and learn how to change your driving style to get the best from it,
i cudnt go back to a T2 on a 5 now!!

Lag is not a problem if your engine can breathe better, and hence rev higher, but the problem with the GTA, physically and electronically, is the upper rev limit doesnt really change, so all you are doing in narrowing the rev range.

Im not expecting my engine to go past 6.5k..even with the perfect manifold, turbo and exhaust system...

because the cams are chain driven and the pulleys fixed, its not like you can advance the cams manually to bring the exhaust valve in earlier as you could on say a Renault 5, or 21..

Errrrr..... yes you can. Been doing it a couple of months now, evening up the banks on the odd-fire (DeLorean & GTA Atmo) engines and re-timing them. Press the pin out of the sprocket. and you just have to put your faith in the torque of the retaining bolt - and trust me, it works.

Got the twin turbo DeLorean running again today with "new" turbos.

Basically we were stuck with the IHI RB52's that were used originally (peculiar manifold mount) and the manifolds they came with. Rich (the owner) did his research and turned up the Mazda 323 1.5 turbo as using a modern RB52, so a pair was sourced and fitted.

Twin turbos help with lag because of lower rotational inertia. However, tubular manifolds make lag WORSE, but allow for better top end power. Tight cast manifolds as found on most modern production (not performance) turbo cars work because of the turbulence generated in the manifold helps spool the turbo up. My HDi Xantia spools up at 1500rpm.

Quick spool time helps torque. Decent manifolds and large compressors help breathing and therefore power. When it comes to turbos, there really is no such thing as a free lunch. If you want torque, buy an Atmo, fit high lift cams and a free-flow exhaust.

*I* love turbo cars. The nuttiest car I've ever driven is my friend's R31 Skyline GTS-R with a T4 on a 2 litre 6 pot. It spools up at 5500rpm and pulls to 8000 peaking at somewhere near the 400hp mark. THAT has a tubular manifold like you wouldn't believe.....

Personally I think the Z7U has a lot more problems than just the turbo. It needs a larger downpipe, a larger throttle (even the DeLorean's K-Jet manifold has twin throttles that together are some 50% larger). The manfolds could do with being equal length and the cams are ridiculously mild... Oh and it's only got 12 valves

Martin

Is this suitable for the GTA Will it fit to the exhaust housing
It ends today so pleeeeease shout out if you know
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because the cams are chain driven and the pulleys fixed, its not like you can advance the cams manually to bring the exhaust valve in earlier as you could on say a Renault 5, or 21..

Errrrr..... yes you can. Been doing it a couple of months now, evening up the banks on the odd-fire (DeLorean & GTA Atmo) engines and re-timing them. Press the pin out of the sprocket. and you just have to put your faith in the torque of the retaining bolt - and trust me, it works.

Well, no..

Its not like you can play around with it on a rolling road to get the best results, which is the only way you are going to know if the modification actually reaps any benefits..Other than that its just hoping its correct..

When I used to take customers Rover Turbos to my local RR, just setting up the inlet and exhaust cam timing by a couple of degrees either way could increase power by up to 15bhp, and bring the turbo in earlier by altering the exhaust cam..

Remember, on the PRV, we can not play with exhaust and inlet timing independantly which would give you maximum torque and power, as its a SOHC motor. All we can do is advance or retard the whole cam timing..

So as I said, we can't bring the exhaust valve timing in earlier with out advancing the inlet side too..

Twin turbos help with lag because of lower rotational inertia. However, tubular manifolds make lag WORSE, but allow for better top end power. Tight cast manifolds as found on most modern production (not performance) turbo cars work because of the turbulence generated in the manifold helps spool the turbo up. My HDi Xantia spools up at 1500rpm.

Depends what the turbos are. Small turbos will spool up quick, but then not give decent top end power. If you find the equivalent match in twin turbos to my GT single turbo, it would be twin T3s with 0.48 housings and 50 trim compressors, which will take longer to spool than my single GT3235X. And your HDi has a very small turbo, hence why it spools quick (and being a diesel) The benefit of this engine type with a low rev limit is that you can undersize the turbocharger to maximise low end torque.

Quick spool time helps torque. Decent manifolds and large compressors help breathing and therefore power. When it comes to turbos, there really is no such thing as a free lunch. If you want torque, buy an Atmo, fit high lift cams and a free-flow exhaust.

It helps low end torque, but not not make a higher torque figure than an unrestricted large turbo setup with minimal exhaust restriction (which is what you would have with smaller turbos to decrease lag)

Personally I think the Z7U has a lot more problems than just the turbo. It needs a larger downpipe, a larger throttle (even the DeLorean's K-Jet manifold has twin throttles that together are some 50% larger). The manfolds could do with being equal length and the cams are ridiculously mild... Oh and it's only got 12 valves

Martin

Its not just the downpipe. The wastegate flange on the turbo is only a 2" outlet, the original downpipe is 2.25". The new twin scroll unit I do has a 2.75" outlet, which can be bolted straight up to the relevant sized downpipe. The throttle body is fairly irrelevant at this power level, and for the CFM consumption at this power. As long as the rest of the intake system is 55mm, then that is sufficient for around 350bhp. 65mm would be the next step, but only nesseccary if the engine is heavy breathing. Ive used a 75mm throttle body, but only because I have had the inlet manifold honed out to this size, and all the pipe work (and chargecooler diameter) is 75mm also..