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Anyone heard of any gains from porting the head and/or intake on stock turbos....I know of two here in Ky that have ported their head and run 11.30-11.40 with traps of 120-122. They both credit these time to the head work.

On the other hand I have talked to 3 of the different "BIG WIGS" in the Supra industry and they say it is a waste of money unless you have a big single. One of these guys even went on to say that would probably even be a loss of power due to the increased volume the "itty bitty" turbos have to push air through now, ie running out of breath!

Could it be that these cars I have seen run these times and dyno 450+ just be lucky.......I dont think so!!

BTW my head and intake are at Extrude Hone right now.....and will display the relsults when the car is back together
 

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I've always believed that a little human elbow grease never hurts. Even though the 2JZ-GTE comes from the factory very stout, it's still a production motor coming off an assembly line and still may have little flaws. Match porting and polishing the exhaut tracts is just a solution to cleaning up the head. Extrude Hone is pretty cool. If you can, please take some pics when you get your head back. BTW, how much did it set you back?
 
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about $1300 for both. Rick at extrudehone claims I will see 30-40 hp?? I'll soon find out!
 
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Out of all those views, noone knows , has seen or has experience with ported head/intake at the BPU level huh?
 

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Several people have run in the 120-122mph range with BPU cars and no ported head or intake. Phillip Long ran over 122mph and Frank Ward ran 120.4 in my car before he installed the FMIC and cam gear. He picked up about 30rwhp from the FMIC and cam gear, but never took the car back to the dyno. If you look at the stock turbos you will see that they cannot hold over about 17psi to redline. This is all the air they will push. I bet with a ported head you will see that you will make the same peak hp, but the boost will fall even more by redline. The porting makes it easier to make the power, but the stock turbos just can't push more air. I do believe you peak torque will go up though. You make peak torque at an rpm where the turbos can maintain boost. If they maintain the same boost and your head flows better than you will probably make more torque. In the end it may make a little bit of difference at the track (because of the extra torque), but it won't make any more peak hp. Of course this is all theory and the real results will be interesting.

Later, Steve
 

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Isn't boost really a measure of backpressure? In other words if you port the head, see lower boost, but the turbos are still pushing the same amount of air then in fact you're ingesting more air? Trouble is a turbo wastegate will continue trying to meet that 17PSI setting and overheat the air or worse. Lower the boost setting and still get the same amount of air I'd bet. The bug in this is how much heat the turbos might impart to the air..

You can see this occur with belt driven centrifigal superchargers. They spin a fixed speed and move a fixed amount of air based on a set of pulleys. I owned a car making about 10lbs of boost. Replaced the intake with a much higher flow unit, had the heads ported, and then put headers on it. Boost gauge then maxed at about 6lbs of boost but the car was noticably faster! Same amount of air, I was just using it more effectively.

This is why I laugh so hard when Mustang owners bench race blower cars quoting boost pressures. It's a measure of backpressure in the intake manifold, with two different blowers, two different sets of manufacturer's heads, and different intakes the boost reading on the gauge between the two cars means diddly.

Porting the head should allow it to ingest more air and hopefully exhaust more too. Perhaps backpressure from the stock turbos nullifies the effectiveness of the porting? Air under pressure shouldn't get lazy in the ports I wouldn't think (?) but backpressure on the exhaust side could back the exhaust into the combustion chamber. Perhaps while it's all torn down you could port the turbos in some fashion? Would the wastegates benefit from porting? How about the stock exhaust manifold? If you decide to have that Extrude Honed I'd suggest hand porting it first and then letting them shoot putty through it for a more effective job. Wait till you see the ports when the head comes back - if it looks like the intake I had done years ago the surfaces will be VERY smooth....
 

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I think the problem is two-fold:

One, at BPU the stock turbos are way out of their effeciency range. Any increase in flow pushes them farther out there, meaning they produce more heat and more exhaust backpressure.

Two, the backpressure caused by the restrictive exhaust manifold and turbos causes the wastegate to open prematurely (which is what causes boost pressure to fall off). Any increase in flow of the head wouldn't mean the engine is moving any more air, because the wastegate will start to open. Some people (like Chris B) have used some method or another to keep their wastegate closed, and have gotten 30 psi or more on the peashooters.

I think you would see better gains if you ported the exhaust manifold and clipped the turbos at the same time. Or better yet, saved the money for a single turbo. The stock turbos simply cannot produce as much power on race gas as even the smaller singles can on pump gas.
 
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Thanks for the interesting feedback/opinions.....I am anxious to see the results.....there are so many different opinions out there and I respect and understand the logic behind almost all of them...its hard to tell what will happen. All I am going on is comparison.

Those supras mentioned that had the high traps attained them after their heads have been done. I know one of them was 118 mph before. So its not a comparison of what all these other bpu buys run, but a comparison of before and after.

The truth will be known soon.
 

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Grant--"One, at BPU the stock turbos are way out of their effeciency range. Any increase in flow pushes them farther out there, meaning they produce more heat and more exhaust backpressure."

Steve--"If you look at the stock turbos you will see that they cannot hold over about 17psi to redline. "

I'm assuming both of you are making these statements based on compressor maps. May I ask which map you're using?
 

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I am not using compressor maps. I am using the scientific method of watching my boost gauge when I go to redline. Not to mention the reliability of the bearings on stock twins is historically compromised at above 17psi.

Later, Steve
 

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Steve Jarvis said:
I am not using compressor maps. I am using the scientific method of watching my boost gauge when I go to redline. Not to mention the reliability of the bearings on stock twins is historically compromised at above 17psi.

Later, Steve
I really think that the 17psi figure varies from car to car. My old BPU+ (VPC) couldn't get *less* than 19-20 psi on a 4th gear pull. It was usually around 20-21 psi with the EBC off. If I turn it on and crank it up I'd see 22-24+ psi in 4th & 5th (never did 6th gear pull). And it would hold that to redline.

Maybe intake/ exhaust combos have something to do with it. I had that huge 9" K&N, VPC & 4" HKS Ti w/ RMM DP.
 

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I recently shimmed my wastegate to hold more than 19 psi to redline.

I say they are out of their effeciency range because they don't make good power! A SP60 is roughly the same spool, yet will make 100 more horsepower on pump gas boost. I just assumed Toyco made their turbos effecient at 11 psi
 
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