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Discussion Starter #1
In with keeping with the mostly stock look for Jeffs R32, its going with a twin GT-RS setup, and the stock twin turbo outlet pipe. We have seen some modified pipes in the past, and decided to make one up for Jeffs car. By keeping the front turbo from meeting the rear turbo at such a 90 degree angle, it should help with the balance between the two turbos, and might even help out with power.

Jeffs car is still going together, so we decided to test the modified pipe on the orange R33 . The orange car is Stock engine, stock turbos, aftermarket downpipe, exhaust, intake, Apex intercooler, Power FC.

The starter on the orange car was starting to click, but it would start about every other time. While dynoing another car, Josh put some more pump gas in it, and pulled the front propshaft so we could run it on the dyno.

The last time on the dyno boost was about 14.7 psi and the car did a max of 346 whp.



This time boost was up to a peak of about 19 psi and the car with the modified outlet pipe did 378.3 hp , 380 hp, and 378.8 hp. Josh changed the outlet pipe back to a stock pipe, went to start the car, and the starter just clicked. Time to change the starter. 20 minutes later, with another starter in it, do a couple pulls. 361 hp first pull , then 371 hp , then back to 361 hp. Boost was around the same 19 psi, but the car was a lot less consistant.

I have to work on the dynochart and replotting it. See if there are any other differences I can see in the runs. I figured that the split outlet twin turbo pipe was worth about 10 hp or so. We will try it on Jeffs car and see how much of a difference it makes on a bigger turbo car.

 

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I think the Nismo type hot duct is a lovely piece of work and would certainly liberate 20-30HP on a 500+car, better spool, better everything!

Replace the nasty rubber low-pressure duct (to rear turbo) as well....
 

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Discussion Starter #10
so the 10 - 15 bhp difference was purely down to the divider?
Well , we started with an R33 with it installed. Ran the car three times. 378 , 380 , 378 hp , and were pretty satisfied at the numbers being so consistent.

Let the car cool off and swapped the twin turbo part, still attached to the Dynapack, and redynoed. No other changes to anything. Well other than the starter that took a dump.

This time we did 3 pulls, all over the place on numbers. Ended up doing 5 pulls in total. Same exact setup. Every pull was at least 7whp, and a few were 18 whp less to the hubs.

Going to test again on a higher power car.
 

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It seems a strange design, the stock item - definitely doesn't encourage flow from the front turbo to go where you want it to.

Sean - did you take any other measurements besides power, eg pressure and temperature at the compressors and/or plenum? I'm interested to learn exactly how the improved flow at this end actually resulted in more power.

What was controlling boost?
 

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Discussion Starter #14
Sean - did you take any other measurements besides power, eg pressure and temperature at the compressors and/or plenum? I'm interested to learn exactly how the improved flow at this end actually resulted in more power.

What was controlling boost?
I have boost pressure and air inlet temperature. Both are logged by the Dynapack. Boost pressures were all about the same run to run. about 18.8-19.0 peak boost pressure over the 8 runs. An HKS EVC was controlling boost.

I could have recorded the runs on a Datalogit, but I didn't . It was just a quick test, one night - late after we had dynoed another car.

Mr. Tamura had told us a long time ago that the twin turbo pipe causes the two outlets of the turbos to come together roughly. If you look at it, makes sense. Air doesn't want to do a 90 degree turn.

Also another couple things, should help with surge. tyndago - Advanced GT-R notes

"Stock inlet hose to rear turbo collapes due to vacuum , replace with steel
Rear turbo always runs much hotter and fails first .
It also produces a different pressure than the front turbo and this contributes to turbo surge
R34 Vspec II has NACA duct to help with rear turbo cooling"
 

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Discussion Starter #15

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It would be interesting to find out precisely how, from the engine's perspective, this increases the power. I'm wondering whether it's one or both of

a. turbos having easier time and thus producing slightly lower charge temps
b. turbos having easier time and producing less exhaust backpressure, somehow

I'm not really sure how much exhaust backpressure can be affected in this way, unless the wastegates can be allowed to flow more gas through themselves, thus allowing marginally greater flow area?
 

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...same effect you always see when decreasing pressure drop - lower charge temps due to lower pressure ratio, lower turbine speed for the same manifold boost. Wastgate open more, by-passing more gas, dropping pre-turbine pressure decreasing internal EGR, charge heating, knock limit etc etc etc.

I imagine the pressure drop is quite high with the std pipe on a 500+ car, proably quite alot of reversion between front and rear compressor......
 
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We been doing this for a while, helps with turbo shuffle as well.
 

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Discussion Starter #19
I imagine the pressure drop is quite high with the std pipe on a 500+ car, proably quite alot of reversion between front and rear compressor......
In a perfect world - both turbos would produce the exact same output. I don't live in that world. I live in the real one. In the real world - the rear turbo will produce less output(flow, air, boost, cfm) than the front turbo. The air will take the path of least resistance. The IC/TB is less resistant, but some will actually block the flow from the rear turbo, and make the flow out of the rear turbo even less.

If we think of air as a liquid, and spray a firehose straight up in the ceiling, and cross the path with another hose, its going to create a mess.
 

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sorry for this guys but im a bit of a newbi at this and im trying to get my head round this

you have welded in a peace to cover the air coming from the first turbo thus making it turn the the 90 degres before joing the air flow from the second turbo so that both air flows are traveling in the same direction towars the fmic etc when they merge ?

if thats correct does the pice you welded in cover the air inlet from the first turbo compleatly ie at an angle so that the flow from the rear turbo moves over it smothley or is there a gap so that the air from the rear asists in blowing trough so that the air from the first turns the 90 degrese but hits a wall insted of the top of the twin turbo pipe interupting the airflow from the rear


again im sorry if it sounds a little simple and if i didnt use the right terms etc but im still learning all i can about them and you dont find out things less you ask do you

ill do a simple drawing later to help explain my question after reading it and it being a bit complicated lol
 
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