Testing modified Twin turbo pipe

[tyndago]

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.

[ExScoobyT]

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....

[tyndago]

Originally Posted by ExScoobyT

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! ..

Yeah but then it wont look stock - go fast.

[Toby Broom]

I though the Nismo pipe made my tubs spool quicker, Nice job Sean, real data to back up the claims

[tyndago]

Actually here some real data. This is all just plotted by eye, so its not 100%.

[kingsley]

Any pics of these pipes?

And also where can you get the nismo pipe, what does it cost and do you know where there are any pics of it?

[tyndago]

Originally Posted by tyndago

This is a modified pipe. It has a divider welded inside to keep the front turbos discharge air coming in at a 90 degree angle.

[tyndago]

126,000 yen from Nismo according to the 2006 catalog.

[kingsley]

so the 10 - 15 bhp difference was purely down to the divider?

[tyndago]

Originally Posted by kingsley

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.

[tyndago]

[GT-R Glenn]

Like this

[kingsley]

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?

[tyndago]

Originally Posted by kingsley

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"

[tyndago]

You just need to see how close the rear turbo is to the outlet tube in the front turbo. That can't be good for it, and makes the rear turbo produce a different pressure. Air will take the path of least resistance. It will try and fight the rear turbo a bit.