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Discussion Starter · #1 · (Edited)
I'm running a new borg warner 60mm turbo (SX300 177272), which is technically capable of 800hp (although I don't know if that's possible on a 3l 2jz due to the amount of airflow it can move)

S300SX3 Complete Turbo
Bearing Housing Material Cast Iron
Comp Wheel Inducer (in) 2.36 (60mm)
Comp Wheel OD (in) 3.29
HP Range 320-800
Turbine Housing A/R 0.91
Turbine Housing Inlet T4
Turbine Wheel Exducer (in) 2.66 (68mm)
Turbine Wheel OD (in) 3 (76mm)

I've run this with a standard exhaust manifold, 23psi dropping to 21~22 up to 8000rpm, made 600wheel on pump, no problem.

I then went and swapped over to an old school RPS manifold, changed nothing else, and suddenly the turbo barely makes 21psi, and drops to WG spring (18psi) by 7kprm, with the wastegate fully shut (or at least that's what I think since my MAC valve could be on it's way out?.. for another time...) I tried increasing the boost solenoid duty but it's not improving boost. The car pulls like a bat out of hell, doesn't necessarily feel like it's loosing any power.

Head has BC stage 2 cams, light valve train, otherwise stock VVTI. What are the chances that I'm now outflowing this turbo? Could the exhaust manifold be that much more efficient in that the turbo cannot keep up? I'm used to running large turbos and haven't run into this issue, thought I would ask around for opinions.

Yes, I've checked your standard boost leaks and what not, nothing obvious. I took apart the wastegate, looks good (Tial 44mm). New turbo gasket as well.
 

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Back Pressure !

I have been running and racing the same turbo since 2013. My set up is stock bottom end,BC 264 cams, BC valve train, "light" Port and Polish, Flex fuel, stock intake, 4"inter cooler and 3.5" full exhaust from turbo housing back, and a 6 boost T4 flanged split exhaust manifold. I have the 1.00a/r Turbine housing, 4 port boost solenoid with 7psi waste gate spring.

I share the same experience as you even tho i have the larger Turbine a/r. Measured back pressure with and without the exhaust connected, it makes no difference. From 19psi, the back pressure sensor literally circa navigates the dial. Unit of measurement range is 0 to 55 psi. Definitely the turbine side maxed out, not the compressor side as IAT's barely rose upwards from 34 degrees.

RWHP recorded on 98 Ron 433rwhp, 100 horses more on E85 at 18psi max on an brand new Dyno Tech by Dyno Dynamics roller. As you say, car pulls like a bat out of hell and is Miss Daisy reliable with all the abuse it has received.

Moving forward if you stay with Borg Warner, need to step up to their 80 mm turbine exducer which means new turbo. Retaining the same compressor core, you can buy the 1.10 a/r but it is longer and will require dump pipe mods, or Full race can source a 1.27 a/r but that will have to be specially made as it is not a shelf product.

Rob
 

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Discussion Starter · #3 · (Edited)
Glad to hear, thanks for the quick feedback. Well, two things. I luckily found a hairline split on the MAC valve wg line leading to the top wg port. Found it by luck, and wasn't showing up on a boot leak test (I stop at 15psi testing). Fixed the hose, went for a drive, and back to 23psi dropping to 21 (which is what I had before manifold swap).

To your points - this turbo is rock solid reliable and responsive, and I agree regarding backpressure. I have a straight 3.5" exhaust, no muffler or resonator, possibly the least restriction I could imagine. Definitely seems to be turbine limitation. I'm still on the .91 ar, but will stay here for track use. I have no need for more power! My biggest concern was the change in performance from one exhaust manifold to the next, and I found the issue here.

This turbo made 600wheel on 93octane here, you definitely have more power capability imho since we have similar engine builds. I did have a turbine housing warp from presumably excessive road racing heat. The housing turned into an egg-shape - as I rotated it aruond the turbo center section, it would click the turbine wheel on one specific spot. I'm sure these things need water cooling for this type of abuse. Luckily, I caught it early as it was blowing blue smoke on decel.

Thanks Rob!
 

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To help keep oil-only turbos cool, I use a bunch of methods,
1. put wastegate near the turbo and use water cooled gate design
2. Put a shield between turbine and compressor that bolts to the compressor backhousing and acts as a heat sink
3. blanket, coat, wrap the turbine
4. With an EGT sensor, use water injection to hold exhaust temperature down below specification (Max BW turbo inlet temp by specification is 1380*F)
5. Make additional shields over the turbine and then run liquid water down those shields when it is safe to do so using a $1 water pump from ebay
6. Run water lines "Around the area" possibly through additional, small heat exchanger. Its okay to use a secondary loop (non-coolant based) like with #5 so the water can be pure, and spill out if it wants.

for #5 I took it one step further and used a PWM driver for the $1 pump, along with a 555timer so that I can run it for 30~seconds after a shut down, like a turbo timer, except it drizzles water at a PWM rate down the shields overlapping the turbine
 

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3. blanket, coat, wrap the turbine
That will hold the heat in the turbo and cook that oil after shutting the car off. IIRC, Corky Bell recommended against that. That was why I sold a brand new DEI blanket. I still ceramic coated the exhaust manifold though.

Al
 

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Discussion Starter · #6 ·
Al - perhaps, but to counter, if your oil temps are in check, does it matter? For a datapoint, I measure my oil temp right at the bottom of the turbo drain, and it barely hits 250 after 25 minute long sessions. I do have the turbine DEI blanket on it. Without it, I cook the paint on my hood :( For 10 second 1/4 mile runs (or highway pulls), may not be necessary...
 
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