BlackWS666

iTrader: (31)

Ok fellow turbo guys and gals, I know this kind of has been a talk forever....I have read countless threads about this and peoples opinions and thoughts but i am yet to see any proven results or differences. I am wanting to change my crossovers from 3" to 2.5". Im doing it regardless of what people tell me/think/predict. I am looking for PROVEN results on a car with no other elements changed. Ether dyno, or logged results will work. Maybe some track times if thats all you have. If no one has them then I will change my crossovers on the dyno next time i go, and you will see mine.

So has anyone else have some proven results?

kmracer

iTrader: (1)

talk to phil, he has data. i suggest you log boost pressure vs rpm vs time before and after as well. im guessing you'll notice more of a difference staging than anything.

are you running a trans brake?

Sluggish

iTrader: (10)

Didn't most people say to go with 2.5" when you were building your kit anyway?

JAX04

iTrader: (17)

Im using 2.25"

I gonna have uberifically high this and that....

Fireball

iTrader: (21)

3" is not needed on a small block, if anything it'll hurt early numbers. Going to 2.5 will increase velocities in the hot side.

I went 7.70s pedaling with little 2.5"

Need_a_Camaro

iTrader: (27)

How much will it affect staging? I went with 3" based on Josh's(KY Turbo) suggestion. I've been worried about staging on the tbrake/2 step as it is, and now I see this.

boost27

iTrader: (3)

I'm building my cross over right now and I think I might go with 2" sch 40 pipe. I wanted something to keep the truck very street able. Also room is very tight up front. The motor is a stock lq4 and magnum 76bb.

Need_a_Camaro

iTrader: (27)

Sch 40? I'm guessing you mean sch 10. That was my plan for my headers, but those plans quickly changed. The price of the material was a turn off for me.

GulfM3

iTrader: (14)

Use sch 10 pipe. 40 is VERY overkill and heavy

BlackWS666

iTrader: (31)

Yes, but for every person who told me that 2.5" would be fine, i came across a guy running 3". Wasnt really all the one sided. Plus i like experimenting


If i didnt have a problem staging i wouldnt be doing this. I was on my brake for over 8 seconds building 7 psi. Tranny went from 91 to 225 real fast.

Josh@KY-Turbo

iTrader: (120)

It all depends on how the Build is done. If the Turbo is Mounted out in the Bumper or where the charge pipes have alot of length to them I do 2.5". The short Charge pipes I do in 3". These Charge pipes are usualy less than 12-14" from the Collectopr to the turbo.

I have debated this a million times. Tested it several times a few years back. In a dedicated Race car where every bit on ET counts I see the reasoning. In a street Car with a Header with a smooth Transistion collector Vs a Stepped Collector I will keep the 3" Charge Pipe.

I dont get the Spooling issues. everyone wants to blame the Tube size. You need to be looking at your Tune among other aspects of your Builds. Hell we have spooled 101mm Large Frame turbos to 12-14lbs with 310ci SBF engines in under 4-5 seconds that dont breath nearly as well as the LS1 Platform's.

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I would stay on the small side personally. I think you would need to go much smaller than 2.5 before the crossover became more of a restriction than the turbine.

JAX04

iTrader: (17)

This is why im using 2.25", was actually considering 2 1/8" (even considered 2") but was talked out of it.

hellbents10

iTrader: (10)

I think it depends on the length of pipe, but more then anything how much total power you plan on making.

BlackWS666

iTrader: (31)

What were the results on the tests? Vehicle tested? Cubes? Turbo? This is what im looking for

Nitroused383

iTrader: (10)

Tune / cam / head / intake all will effect spool. That being said you have a cam designed for a supercharger not a turbo cam at all. Oh and let's not forget the single most important thing in a turbo drag car... the torque converter. The right torque converter will make or break you.

98Z28CobraKiller

iTrader: (17)

Are you using a 2 step?

Josh@KY-Turbo

iTrader: (120)

370 cubes. FAST XFI/XIM computer. S480 turbo. 1.32 A/R. Used 6.0L manidolds to make it easy. Did a 2.5" and 3" Crossover, Used the same 4" DP. The diffrence in spool up was minimal. Maybe 200rpms diffrent, and maybe a second or so time wise. I used a TH400 and T-Brake. Never used the 2 step. I used alot of timing down low. Belive me it makes a huge diffrence.

We did this over the course of a weekend. Should have video taped it all, but didnt. At the end of the day I fall back on what I said earlier. The headers I use on alot of the builds I do come from Stainless Works. They have a 3" Collector. On those I build Short Charge pipes in 3" Stainless. When I build Custom headers I use a Slip Merge Collector with a 2.5" end. I do the Charge Pipes on 2.5" on those.

Dont overthink this stuff.

BlackWS666

iTrader: (31)

yes sir lnc-002....told i need a 3 step to do it right though.

BlackWS666

iTrader: (31)

Please explain.