Turbo kit and fuelling help - 3SGTE ST205 GT-FOUR (Gen 3?)

[13Beast]

Hi guys,

I'm a new member here and drive a newly bought 1996 ST205 GT-FOUR.

It's a JDM model (as I live in Japan) and am looking at potential turbo upgrades that will still run well and perform well on a motor with standard internals.

The GT2860RS seems like a good turbo, and while I love its quick spool and drivability, I am worried that it might be a little low on overall hp levels. I'd love a GT30, but it's probably overkill, and won't be in its volumetric efficiency range boosting safely on a standard motor.

As such, the GT2871RS has my eye... I see they are offered in a kit by KO Racing and ATS, but I am interested to hear people's opinions of the quality of their kits - especially considering they mostly cater for the USDM MR2 market, and pre-94 all-tracs, as opposed to later model ST205's. Ideally, I'd like to find a kit that can more or less bolt straight on, tried and tested, for an ST205.

Are the ST205 motors classed as Gen 3 motors?

I am happy to increase fuelling - Sard, Power Enterprise etc offer injectors in 600cc, 650cc, 700cc and 800cc. I am guessing 800cc is overkill for a standard motor running a GT2860/71, but I am worried that 600 or 650cc might be a tad small. Standard ST205 injectors are 540cc and max out around 340hp (so I have heard). Am I wrong in thinking that 700cc would probably be the best choice?

Will the standard fuel rail flow enough? I have seen ATS bore out fuel rails, but those are for earlier MR2's. Curious to see what advantages (if any) would be gained from selecting a Sard, HKS etc aftermarket fuel rail, or if the standard ST205 one is fine.

The standard fuel pump probably won't cut it, so will a Supra TT fuel pump flow enough fuel for that purpose? Or will a 255 pump such as a Walbro be needed? Is a flow rate of 255 lb/hr overkill? Ideally I want something not overly noisy. Any recommendations?

My regular workshop is Do-Luck Racing, near me in Kohoku. If you used to get into Option magazines and videos from 10 years ago or so, you'd probably know Do-Luck. I'm lucky to have them to tune my car, and they are very good at what they do. I will probably opt for a full HKS F-Con ECU and have the boss there tune it.

I guess quality tuning in this case will be imperative, as the standard ST205 3S will be getting pushed to its limits with around 400 crank hp or so? Or can it take a bit more?

Cheers
Dave

[jonathan yee]

1st. you have an tune-able ecu for this already? you'll need this apart from the obvious fuelling upgrades, but one that will do individual trim on the cyl's. as if you retain the stock centre feed manifold cyl's 2+3 get more direct feed/boost than outer and require more fuel to stop dangerous lean out, coupled with the fact that cyl's 2/3 are prone to cracking in some motors. various reasons for this.

yes st205 is a gen3 3sgte. already has MLS HG, pistons and rods can take a beating provided you have it tuned well with no detonation etc.

either go walbro, cheap as chips, or supra, or even the aeromotive stealth, bigger still and cheap.

standard gen3 rails is fine. much better design and flow than gen2 rails.

how well your stock engine copes depends alot on previous care and maintenance and as said how well the cars is tuned with the new upgrades.

can't comment on those kits personally, tho i think theres a couple guys on the mr2 forums with them and they're happy enough, nothing beats a properly designed mani and ext gate than an adapter based kit. but obviously it costs a lot more.

[13Beast]

How inefficient is the CT20B when boosted up? It seems most of the engines that I have heard blow up, are from guys running the CT20B at high boost. Do they tend to become very inefficient past 17psi and end up pumping just hot air, increasing the risk of detonation? That's one reason why I am leaning towards a larger turbo, as I know the CT20's are rather small, and I want to keep the intake charge cool.

I've also heard about the block's cracking as certain production runs of blocks were thin-walled. But there seems to be some conjecture as to when and how many of these blocks were produced?

[jonathan yee]

The 20b is def better than the ct 26, but yes people do push 18etc on them which will shorten their life span, esp the ceramic jdm ones.

Ive been in a gen 3 powered st185 with 264 cams etc and a gt2860rs with 0.86 rear, supposed to have approx 240odd awkw. Very responsive which is what you want for a gt4.

Are you going to retain the stock wta intercooler? Ive heard they dont like excessive boost and can split.

[13Beast]

Yes I plan to retain the stock W2A ic as long as I can. I have heard they only need to be changed after you surpass over 400hp. Ideally, I'd like to stay away from an FMIC as long as I can if it isn't needed as it will increase lag.

I'm leaning towards a GT2871R, purely for having more power than a GT2860RS. I'm hoping the precision billet version that KO racing offer (the road rage PT28), together with a low 0.64 A/R might give it similar to, or not far off, 2860rs spool-up times with a significant bucketload more power... but not enough to kill a standard motor if tuned sensibly.

Coupled with a good tune and some cam gears, maybe it might end up a nice little ride.

Anybody out there with experience of KO Racing products, or being for a ride in a 2871R-equipped GT4?

[jonathan yee]

you mentioned cam gears but not cam's themselves. it's a waste of time getting cam gears for the stock cams.

RE:wta splits, they split more due to the boost pressure than what power your making. ie: you can make more power with less boost on a larger turbo than big boost on a small turbo. check in the gt4 dedicated thread. pretty sure thre's a couple there with split cores from running 18-20psi of the ct20b.

but you could always fit a more beefy wta unit than going to a frount mount.

tbh if you want peoples exp with KO/ATS procucts you'll prob find more info on the US sites. i don't know of anyone with an st205 with one of their kit's, there may be some st185/165's or sw20 mr2's.

[13Beast]

I'd only get cam gears to give my tuner some more versatility at tuning the car, and perhaps fine-tuning it a little better. It wouldn't be for whatever minimal hp gain as I'd be running stock cams.

I personally don't want to run anything over 17psi on my CT20B. It's JDM, so its ceramic-wheeled, plus all that hot air pumping into the charge-cooler... I'd rather a steel-wheeled, larger aftermarket turbo with a cooler intake charge to minimize the chance of any det killing my motor.

I can get a Trust TD06 manifold for an ST205 cheap here. Wondering if a TD06-20g would give me adequate power? Would it be a jump over the GT2860RS?

Something squarely between the GT2860RS and a GT3071/76 is what I am looking for.

I'm wary to try any of the T3/T4 "street brawler" kits offered by KO Racing, nor any of the hybrid turbo's. I'd like to stick with a name I can trust (scuze the bad pun!) such as Trust or a Garrett.

I read this article here - How To Choose The Right Turbo For You - Boostcruising

Doesn't say many good things about the 2871R or the 2876R... The GT3071R, while a lovely sounding turbo, is probably a tad too big and laggy for a stock motor in my circumstances

[jonathan yee]

yes, some people think the 2871 and 3076 are mismatched turbo's, i can't comment really i have no idea. but it makes sense, it's the same turbo as a 2860 (or 3071) with a bigger comp wheel, sounds like a hiflow......

but in regards to cam gears with stock cam's, i highly doubt your tuner will get any benefit from adjusting the timing of the stock cams. on gen2 3sgte's there was some benefit from adjusting the exh cam to the same timing as the gen3 exh cam.

and it'll just cost you to have them installed which is time consuming reseting the timing belt etc.

there seems to be a lot of talk about the new borgwarner turbo's with Ti turbines etc. i know there was a massive backlist for people wanting the turbo's, dunno how much info there is on them installed and running on 3s motors yet.

[13Beast]

I hear you about the cams, duly noted. I'm discovering more and more differences between gen 2 and gen 3 motors as I research. Sucks that so much of the aftermarket support is geared for gen 1 & 2, and mostly all-tracs and MR2's.

I've seen the BW turbos and they look great. But will they bolt up to the factory T2 flange on the ST205's? Are any companies selling adaptors for them?

Choosing a turbo is doing my head in. I thought about sourcing a Greddy TD06 as I have access to buying a s/h Trust tubular exhaust manifold for an ST205 that will mate a Trust/Greddy turbo to the gen 3 block. What are the advantages of using a proper manifold like that to mount a TD06, as opposed to using an adaptor plate such as ATS offer in their kit? Will it flow better? More power? Less heat?

Trouble is though, the Trust TD06's are a fortune. I'm thinking of sourcing a Mitsubishi TD06, but am confused as to which would be the suitable compressor, turbine wheel and housing size to go for. I want something that can be run in its sweet spot with minimal lag on a stock motor (read: a lovely balanced, efficient turbo such as the 2860RS or 3071R), yet have significantly more power than the 2860RS... but a fraction tamer than a GT3071R - allowing it to be not marginalised by running on a stock motor.

A TD06S / SL2 -18g sounds good... Or a 20g, provided the spool isn't too slow. Not sure whether to opt for a 7cm, 8cm or 10cm housing. Seems like EVERYBODY using these turbos is driving a Subaru or a Nissan, and I don't want to let my decisions of which turbo to choose for the 3S be from reports on how they spool and produce power on entirely different motors.

Plenty of MR2/Alltrac guys rave about the T3/T4 SB .46 kits. Maybe that's easier, simpler, more tried and tested?

[jonathan yee]

1st, altho the turbo is called a cT26/20b the flange is not T2 based at all. it's a toyota only design and it's twin entry, flange is closer to t3 size but still not the same.

TBH, i'm not entirely sure you'll be able to hit your power goals without changing CAM's. IMHO, i'd go with a gt2860, the stock cams will limit head flow, you can't always ness just add more boost.

check for cracks in the S/H manifold.

cost is the big factor in going adapter or new manifold

i've been for a ride in a friends sw20 gen2 with td05, very fast spool.

re: US/UK dyno power outputs, in general the figures are higher than what we get in aus for various reasons.