sprayinLS1s

iTrader: (17)

something similar to this may be helpful for the rear-mount guys. basically what phil said earlier, its dumping before the "bottle neck"
i have almost zero back pressure, instant spool, no boost creep, and can spin +7,000 rpm, with a 76mm rear mount, .96 exh

TracyRR

iTrader: (8)

Yes, i will hopefully complete the new exhaust by next weekend.

I have this cover already.

Yes, i will be changing my exhaust around and will also move my wastegates up front. Thanks

Phil99vette

iTrader: (11)

What are you using to measure backpressure and is that 2.5" tubing? there is probably a good bit of turbulence at your merge.

Phil99vette

iTrader: (11)

One thing I am thinking about doing when I add a pressure guage is add a check valve so it will hold the highest value.

TracyRR

iTrader: (8)

Great idea.... i had to video the pass because the backpressure gauge moves so quick, kinda hard to tell without it.

TracyRR

iTrader: (8)

I finished the new hot side.... Coming out of the manifolds is 2.5" diameter pipe for less than one foot, then it steps down to 2.25" for approx six feet and then steps down to 2" diameter pipe for approx two feet..... I also relocated the tial 38mm wastegates up front just after the exhaust manifolds and positioned well for good flow. Everything is wrapped from front to back. My original hot side consisted of 2.5" all the way with some pretty restrictive bends. My butt dyno says it spools quite a bit quicker with the new exhaust AND the larger exhaust housing T3 .82 versus my old exhaust and the smaller T3 .63 exh housing. In addition to the smaller diameter hot side, i also relocated the turbo's higher and closer to the center of the car so as to give a straight shot for the hot side to reach the turbo's and also for better ground clearence. I will run a backpressure test this weekend to see how much better the backpressure ratio is and will update then with another short clip. In the next couple weeks, i will fab the cold side.... The current charge pipe is dual 1.75" pipe and seems to be wrapped around every inch of the car..... the new cold side i will fab will be dual 2" pipe and approx four to five feet shorter per side. I am hoping to make my rear mounted twins more efficient with less backpressure and quicker spool..... So far the hot side is a success, i'll update soon. Thanks for all of the help!

Phil99vette

iTrader: (11)

Interesting results!

JAX04

iTrader: (17)

This is interesting, nicely done, i will be watching to see the results of the testing.

TracyRR

iTrader: (8)

Thanks for the help phil! I would have never thought smaller hot side pipe would improve my combo until i started reading your threads on crossover pipe size.... You got me thinking and i appreciate all the help!

hey kyle, what size hot and cold pipes do you run?

JAX04

iTrader: (17)

When i was rear mount, i ran a dual 2.5" into a single 3" that ran about 6' long to the turbo.

Currently as a front mount, i run dual 2.5" into a 3" merge, kind of typical i suppose, lol.

and the cold side is a 3" from the compressor to the intake.

I considering doing some smaller ones, like 2" etc. but was told for fabrication purposes as i am def. a novice, it would be easier to to this route.

That and im not making near the power you gents are. lol. But, i will continue to pay attention to yours and phils ideas and testing. Keep up the great work.

TracyRR

iTrader: (8)

I forgot you were moving to a front mount..... Spool shouldn't be an issue anymore for you!! ha ha I'll have to check your build thread. Best of luck, tracy

TracyRR

iTrader: (8)

The car is definitely making more power!! I measured backpressure today and it went from 2.1:1 b/p ratio with the .63 housings and old exhaust to 1.75:1 with the .82 housings and the new smaller exhaust..... Instead of killing the tires at 18 pounds of boost, it now does it at 16 pounds. The spool up is better and it makes more power, i'm pumped!! I'll update when i fab the cold side..... Thanks guys

98Z28CobraKiller

iTrader: (17)

I don't see why not as the area of (4) 1.5" pipes is still more than a single 2.5". That transition near the collector should help velocity and pressure.

Phil99vette

iTrader: (11)

So basically it spools faster and has less backpressure. Boy that is phucking confusing but hey what do I know.

Phil99vette

iTrader: (11)

On a setup that you would use a 1.5" primary, you wouldn't use a 2.5" tube.

98Z28CobraKiller

iTrader: (17)

I thought we were talking about a 1 5/8th stepped to a 1 1/2 and then into a 2.5" collector. The 4 1 1/2's would have exactly the same area as a 3" collector. But most turbular headerd single T4 systems use a 1 5/8th-1 3/4 primary and choke that straight down to a 2.5" collector/merge and then choke it again into a single T4 flange.

Zombie

iTrader: (2)

Reducing surface area of the hot side piping retains more heat which allows more exhaust to be bypassed through the waste gate and around the turbine with a bigger turbine housing while retaining the same spool characteristics. All that = reduction in back pressure, more power and faster spool.

Phil99vette

iTrader: (11)

We're not really choking anything, its controlling velocity. Everyone is free to do it however they think works the best. IMO, which is just my 2 cents, you dont need 2.5" crossover tube on a setup only making 1000-1100hp. Will it work, yes.... Do I think you can see better results with a different crossover, yes. And simply because you have a 2.5" collector doesn't mean you need to use a 2.5" crossover.

HydroStream6

iTrader: (16)

Just something to think about. Suppose in a particular turbo setup, the turbine wheel/housing is the restriction of the hot side. Suppose you've reached a plateau where adding more boost is no longer making any more power due to back pressure. Now also suppose this setup has excessively large waste gates for boost control, and now you want to spray a 200 shot on top of this combo. Would it make the power you would expect from a 200 shot, or would the restrictive turbine/wheel combo still limit power?

Just curious to see what everyone thinks.

TracyRR

iTrader: (8)

hey zombie, do you have an opinion of what i'm about to do with my cold side? Thanks for your input.