GEN IV 3S-GTE differences

[Al]

Thats what I thought....from all the dyno plots that I've seen from the US MR2s...it doesnt matter what you do to the ct26...its still doesnt pull the numbers that it should.

I'll dyno my mr2 once all the goodies are finished and we will see

[Wildcard]

The problem with the CT20B is that you basically can't upgrade or rebuild them, at least from what I've found available in NZ.

If you could upgrade them I beleive the compressor wheel is still the major restriction in stock form. On my Blitz K1-380v which has a very similar layout to the CT20b they upsized the impeller wheel by about 7mm while leaving the exhaust wheel the same size.....

[Farmer_dave]

What do you mean when you say cant be rebuilt?
I had mine fully rebuilt and they say they did some minor porting whatever that means

[Farmer_dave]

Oh unless you mean putting a larger compressor wheel in it cause that I know nothing about

[Wildcard]

Who did the rebuild and what did it constitute?

When I was considering turbo options I rang sources in AK and ChCh only to be told you couldn't source the appropriate steel wheels / shaft to upgrade them nor the bearings / wheels to rebuild them to the stock spec. I could find no help online either. Toyota only sells the turbo as a complete piece, maybe you got lucky?

[Farmer_dave]

The shop that did the install job subcontracted the job to a local turbo shop all it said on the invoice was "stripped turbo polished shafts replaced bearings cleaned up ports beadblasted and assembled with new kit.
p.s wasnt implying you were wrong just I was a bit confused

[Wildcard]

Well if they did find bearings obviously I'm wrong
Thats definetly a step in the right direction although its still a problem if the wheel / shaft is damaged or you want to upgrade.

[Twolitre]

Hey Ben I was recently quoted a price from altech to rebuild my CT20b, bearing in mind that mine is a steel one, but you can rebuild ceramic turbochargers it's just that there's a risk of them breaking when you take them apart meaning the people you contacted probably just couldn't be bothered with it.
All things being equal I might dyno my car with CT20b and then with CT26/T04E on the same boost pressure (1 bar) to determine "for arguments sake" which is the more power productive of the two but I find it hard to believe the turbo with the smaller compressor and the smaller turbine will make more!

[fivebob]

Identical modifications? Identical boost pressure?
One member here installed a CT26/T04E onto his ST205 after his CT20b failed and said it was considerably quicker on 15 psi than that of the CT20b on 18psi
No other mods were done before or after installing the new turbo.

Ahh the good old "I had a mate, and by his SOTP dyno (after how many months off the road?) it was heaps faster" logic. Sorry but that's not going to sway my viewpoint when I have lots of stats to compare with.

Why don't you spend a few moments and check out the link I posted you'll find a lot of turbos with same basic mods and you'll see the CT-20B performs very well against most other turbos it's size certainly far better than any CT26 or even T3/T4 combo, and at comparable boost too.

However if you must modify a Toyota turbo, why not start with the better turbo anyway, both the Blitz K1-380v and the Power Enterprise PE-1919 are modified CT20B's, K1 is a KKK CHRA (Centre housing & Rotating Assembly) rated at 380PS and the PE-1919 is an IHI CHRA rated to support 400PS so it's more than enough to tax the 540cc injectors.

Changing the CHRA is a simple engineering task as long as there is sufficient material in the housings to machine out, ie you're putting a bigger wheel in it's a simple job, gets slightly more complicated if you have to machine the compressor/turbine to fit the housing though, with the whole assembly needing a dynamic balance.

I find it hard to believe the turbo with the smaller compressor and the smaller turbine will make more!

It's all about flow, that's why they clip the CT26 turbine, can't flow enough exhaust gasses out so you can't make the HP. Exhaust back pressure must be pumped against by the incoming charge resulting is less cylinder fill, less charge, and charge diluted by exhaust gasses results in lower power, quite simple really.

Anyone measured the AR on the CT26 vs the CT20 turbine housing? That might tell the real story

And just a minor point but shouldn't the GT-T turbo be called the CT20C as it's no longer the "Twin entry CT20" that TTE referred to

[fivebob]

Now back to the topic at hand.

The manifold, from the top left there is the PCV vent from the cam cover, then the outlet pipe for the brake booster. Just below that is the fitting for the MAP sensor (directly above) and FPR (on the end of the fuel rail), in the centre of the plenum there is the Manifold Temperature sensor. Black plastic thing at the bottom of the throttle body is the Idle Speed Control (ISC) valve

Next is the top feed fuel rail, the three mounts attach to the head (corresponding mounting points can be seen in the pic of the cylinder head at the start of thread).


This VSV with bleed to atmosphere (the black cylinder), is in line with the FPR, maybe some form of fuel pressure control.


The injectors same 4 nozzle pattern as the side feeds, and different from the 2 nozzles on the Supra injector.

[imghttp://www.users.on.net/~fivebob/Images/GenIV/Fuel3.JPG[/img]

Turbo VSV (lower left) and added accumulator (upper right), Purpose of the accumulator?? Maybe to keep the wastegate open longer so it flutters less??


The Ignition coil (bolt attaches to cam cover), and connector. The outside two wires (black seal) are common to all coils, inside two wires (red seals) have different colour coded wires.

Cam cover top, crankcase breather pipe on left goes to the intake before the turbo, and the hole in the top right is the fitting for the PCV one way valve the goes straight into the intake plenum.

Underside baffling acting as catch can and oil return for the PCV (lower right), and the intake (top half) crankcase breathers

[Lanius]

Grey cam wheel cover = gen II, black cam wheel cover = gen III, both have plain alloy cam covers and distributor ignition. If it's got a plastic cam cover in black or red and direct fire ignition it's a VVTi engine. My money would be on gen III though.

Well we checked it out the other night, its got a distributor and a black plastic cam wheel cover, so Gen III it is

Would still love to see some dyno results for it ...

Cheers Nem


Geez fivebob ... everytime I think I've got it down, you introduce some more parts I've never seen / heard of before
Keep it coming

[KiwiMR2]

The problem with the CT20B is that you basically can't upgrade or rebuild them, at least from what I've found available in NZ.

I had quite a long discussion with Kruncy about upgrading the CT20b....as a comparrision with the Fensport upgrades, he said he has done a few Caldina ones and could do a MR2 one as well, NZPC forums is down so once it's up I'll post his comments

Cheers
KiwiMR2

[Mr Revhead]

i also have just spoken to my turbo guy and he was a little cautious. they havnt done a ct20b but said he'd very keen to have a look at one. there are no off the shelf replacment parts for them but he reckons it may be possible to fit parts from another turbo with some machining. so if any ones got a ct20b out there they need to off load let me know and we maybe able to get to the bottom of this!

[Wildcard]

I'm a little perturbed here.. 2Litre - I spoke to Culley @ Altech 3 months ago and he said there were no upgrade options for the CT20B... what was the quote like?

I've seen it done overseas via the likes of someone like Fensport but the local knowledge and parts do seem a little scarce.

Anyway, if you can rebuild / upgrade them - thats great news

[Twolitre]

The quote was for a rebuild only, $400 + gst
This was from Chris James at Alltech Deisel and turbo, did you ask for a quote on a rebuild as well as an upgrade or just an upgrade?

[Wildcard]

Pretty sure Culley told me he couldn't source the bearings to do a rebuild... obviously they do exist but it looks like upgrades are still scarce.

[Mr Revhead]

from culley himself:

Basically the answer is this: CT20B's are rebuildable, but unless there's something specifically wrong with them it's not advised to do so. Ceramic turbine turbos are highly susceptible to failing after rebuild - the bonding between the ceramic wheel and the steel shaft often isn't strong enough to survive the disassembly-reassembly process. Usually any turbo that leaves here which is a rebuilt ceramic will have no warranty on it.

Replacement all-steel shafts aren't available for the 20B - Toyota don't sell the WRC ones separately, and no other third party manufacturer make them. That leaves the option of retrofitting another shaft from a different turbo, however this is harder than it looks. Toyota use a shaft profile that is different to just about every other turbo in existence, and at very least you'd be looking at a large machining cost on top of an expensive new shaft, IF you could find a suitable shaft to start with.

We've just recently retro'd our first steel shafts into a 2.5L TT (1JZ) Supra with good success, and potentially the same could happen for the 20B in the future, but I wouldn't be holding your breath that parts will become available.

and:

the bearings and piston ring seals are available for them, so from a pure time-expired rebuild point of view they're perfectly servicable

[Farmer_dave]

Ceramic turbine turbos are highly susceptible to failing after rebuild - the bonding between the ceramic wheel and the steel shaft often isn't strong enough to survive the disassembly-reassembly process. Usually any turbo that leaves here which is a rebuilt ceramic will have no warranty on it.

$&#$%!!!!! Should I be worried??

[Mr Revhead]

not if there is a warranty with the turbo work

[Dell'Orto]

Hmmm, including CT26's? I had mine rebuilt and have put about 5,000k's on it so far
Oh well, when the car is back it'll be packing a steel wheel