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Not an RB but pretty solid on pump gas and then E85. HKS GT III RS 3.4L 2JZ. They don't look like they run out of turbine as mentioned in a previous post at 700hp.
GTIII-RS is a much bigger turbo compared to GTIII-SS, in the RB26 application the exhaust a/r of the GTIII-SS is 0.54 which is just a tad bit larger than the stock 0.49, the -7s and -9s are 0.64.
 

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What do you mean by "what i would go for i was building again"?
Presumably matty32 would've bought either HKS GTIII-SS or GTIII-2530 if given the choice to pick a set of bolt-on twin turbos again, rather than Tomei M8260. The ARMS M7655 and M8260 are known to be rather laggy for the power they produce.
 

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At the time of pulling it together (original time scale) and ordering , the only Japanese twin set up available was the tomei. Or used 2530. I wanted all new. When the car was 90% done HKS then came out with the GT3s. Tbh it was another 2-3k I didn’t want to spend when I had brand new tomei items fitted. So the headache & cost of engine out , refitting etc Midori did say they would have preferred to use the HKS items but the 32 runs great. Yes a little laggy but I’m not out to set any time records.

if I had the choice upon the original order. Definitely the HKS ones.

am I going to go through that situation again … no but if you have the choice I’d suggest you go HKS
 

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Oh I see. Too deep into it to go back to HKS. Not a cheap hobby by any stretch.

I should be receiving my GTIII-SS soon from RHDJapan. Yen is really cheap to the dollar. Will be going in the next month on my built R32 GTR. Was also thinking step 1 vcam, but lead time is 210 days! Really like the response upgarageusa seems to get with that setup. I am really after 400 whp with early 350ish wtq - say 3500ish RPM.

For the time being, what can I expect from these realistically without vcam? I have a lot done. To mention a few...
Link g4+
Japan Tomei B pon cams 260
R35 coils
Cam crank trigger
ID 1050 injectors
Twin 460 lph pumps and lines
Flex fuel
9:1 forged 2.6 L
No adjustable cam gears though

My biggest concern is the larger cams for these small turbos, especially hampering early responsiveness. Any suggestions and or data?

Thanks
 

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BTW...it's a long story...I will use the HKS turbos to break in my engine, and depending on the outcome, I may immediately sell them.

My original intent was to go g30-660. Now the artec single cast mani is available for the RB26, so I may go that route with my set up. If so, I will offer the HKS twins for sale with very little kms.
 

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Oh I see. Too deep into it to go back to HKS. Not a cheap hobby by any stretch.

I should be receiving my GTIII-SS soon from RHDJapan. Yen is really cheap to the dollar. Will be going in the next month on my built R32 GTR. Was also thinking step 1 vcam, but lead time is 210 days! Really like the response upgarageusa seems to get with that setup. I am really after 400 whp with early 350ish wtq - say 3500ish RPM.

For the time being, what can I expect from these realistically without vcam? I have a lot done. To mention a few...
Link g4+
Japan Tomei B pon cams 260
R35 coils
Cam crank trigger
ID 1050 injectors
Twin 460 lph pumps and lines
Flex fuel
9:1 forged 2.6 L
No adjustable cam gears though

My biggest concern is the larger cams for these small turbos, especially hampering early responsiveness. Any suggestions and or data?

Thanks
I did a 4th gear pull, 2000 rpm in real world conditions. With no VCAM the GTIII-SS will get you 7 psi by 3000 RPM with purely wastegate spring pressure. This is with an untuned RB26, just the turbos swapped and otherwise stock. This is nearly identical to what UP Garage reports with their stock untuned R32 GTR dyno charts. Eventually I plan to get it tuned with VCAM but there's a lot of things that I still need to get figured out first. The Poncams will likely not affect spool as much as you'd expect as their centerline and thus valve timing is going to be different from stock even without cam gears.

The Artec manifold looks good but to me it's disappointing that it's not a twin scroll manifold. The whole reason why the RB26 was twin turbo in the 90s was that by having two parallel turbos there was better exhaust scavenging. This way there's no two cylinders that have overlapping exhaust events trying to compete with each other for exhaust flow capacity. One of the major benefits of a modern single turbo is that they can achieve this with a twin scroll design while retaining the practical benefits of reduced routing complexity compared to a twin turbo setup. When you look at BMW turbo I6s they either use a twin scroll single turbo or parallel twin turbo for gasoline.
 

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Thanks for the feedback. Maybe there is not much exhaust efficiency drop in these compact turbos with turbines smaller than 1. a/r. There must be a reason why Garrett only offers the divided t4 above that. Strange they only show 1.06 a/r divided option for the standard rotation and not reverse rotation on their catalog.

Who knows the intent for sure? Cost savings due to limited applications? Juice not worth the squeeze maybe?

I do like the stout shorter runners of the artec which will be less likely to crack while providing improved adiabatic efficient to the welded manis. Plus it appears to play nice with must have factory peripherals. Would be nice if it came with individual egt bungs but probably not necessary for 500 hp realm.

I will see how the flex fuel tune goes with the HKSs once installed. I like the factory twin look, and there is no doubt that it plays nice with the peripherals - ps, ac, and brake lines. After all, looking for a responsive 400 to 450 whp reliable street car. Just might work!

Ps...not sure what you meant in your last statement about the cam shaft timing differences bw stock and the pons and how it won't have impact on response.
 

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Thanks for the feedback. Maybe there is not much exhaust efficiency drop in these compact turbos with turbines smaller than 1. a/r. There must be a reason why Garrett only offers the divided t4 above that. Strange they only show 1.06 a/r divided option for the standard rotation and not reverse rotation on their catalog.

Who knows the intent for sure? Cost savings due to limited applications? Juice not worth the squeeze maybe?

I do like the stout shorter runners of the artec which will be less likely to crack while providing improved adiabatic efficient to the welded manis. Plus it appears to play nice with must have factory peripherals. Would be nice if it came with individual egt bungs but probably not necessary for 500 hp realm.
The intent is likely that the twin scroll is more restrictive with the same a/r due to the divider and smaller runners. However, the improved driving efficiency with twin scroll usually outweighs this effect. I agree that a low mount manifold makes more sense to improve time to g and provides less leverage for warping to occur in addition to making room for accessories. Generally speaking the twin turbos will have a smaller a/r than an equivalent power output single turbo. So a 1.06 a/r may not be as bad as it sounds. I would look at the turbine chart of a 2860R and double the flow rate to get an idea for what that looks like vs an equivalent single.

I will see how the flex fuel tune goes with the HKSs once installed. I like the factory twin look, and there is no doubt that it plays nice with the peripherals - ps, ac, and brake lines. After all, looking for a responsive 400 to 450 whp reliable street car. Just might work!
Shouldn't be awful, at least if your expectations are basically somewhere in the region of what the Garrett GT2560R/-7s, R34 N1, Nismo R1/R3 turbos will deliver. I think the general poor perception of these turbos in the US/Australia are mostly driven by two metrics. First is price, which HKS has never been great at competing in and just the nature of two turbos vs one means this was never going to be a battle that they could win. The second is power output. The GTIII-SS is not a big turbo, it's not really designed for huge power. 5652 55T means the compressor is substantially smaller than even the GT2560R in both inducer and exducer. The turbine is not quite as different but it is still a little smaller than the -7s.

Ps...not sure what you meant in your last statement about the cam shaft timing differences bw stock and the pons and how it won't have impact on response.
Factory R32 RB26 camshaft intake and exhaust timing is 113 degrees ATDC on the intake and 125 degrees BTDC on the exhaust. Genuine Tomei JP 260 type B poncams move this to 110 on the intake and 115 on the exhaust. So that represents 3 degrees of advance on the intake cam, then 10 degrees of retard on the exhaust effectively. This decreases the lobe separation angle and allows for more scavenging effects, just not as far as you can push things with VCAM. I suspect what UP Garage has figured out is that with enough intake VVT advance they can have significant amounts of air that doesn't even fill the cylinder and starts spooling the turbo directly instead. This is how modern GDI turbo engines put out monstrous amounts of torque as low as 1500 RPM. The reason why OEMs didn't do this in the port injection days is that doing this causes a bunch of fuel to bypass the cylinder entirely which is problematic for emissions and/or the catalytic converter. With GDI you can delay fuel injection until both intake and exhaust valves have closed so no fuel shoot-through occurs:

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