ITBs with trubo

[Pyrorocketeer]

ITB's with a Turbo, can greatly reduce turbo lag. Also, look at it this way, lets say each ITB butterfly is 1.5 inches diameter. Multiply that by 4 and you get the same flow as you would a 6" throttle body. I have yet to see a 6" throttle body on a 4 cyclinder street car. I have seen boosted ITB's and am actually setting up a 1.8T 20 Valve VW engine to run 2 bar boost through CB performance throttle bodies (based of a Weber Sidedraught design) using a T3/T4 60 Trim Ball bearing Innovative Unit.

 

With the paper calculations we should be able to hit 450 WHP peaking as soon as 3900 RPM. All going in a Longtravel Baga buggy.

 

ITB's are great for boost, you just need a lot of tuning and dyno time to get them perfect, but they will allow individual cyclinder tuning at finer increments than a common manifold single Throttle body.

 

911 Porsche Turbo race cars are all boosted though ITB's. VF engineering kits for the M3 BMW are boosting through ITB's.

 

If you have the skill and the cash its definetely worth it.

 

The hard part I am going to have is creating a tuned equal length header before the turbo.

 

 

Wrong.......1.5 x 4 doesn't equal the flow of a 6" TB.

do the math (1.5^2(3.14))4 = sqrt(DIA/3.14) solve for DIA and you get....1.5r

 

4 - 1.5's = one 3" dia. which is easy to do.

 

 

How is turbo lag effected?

Equal length runners aren't necessary. Look at subie motors? 2 runners are almost double the length of the other. Turbo header short= better.

 

I'm still not seeing the benifits.

 

btw....I'm into veedubs too.... have a rail, a 74 super, and a 57 oval ragtop

[Skwurlz]

Wrong.......1.5 x 4 doesn't equal the flow of a 6" TB.

do the math (1.5^2(3.14))4 = sqrt(DIA/3.14) solve for DIA and you get....1.5r

 

4 - 1.5's = one 3" dia. which is easy to do.

How is turbo lag effected?

Equal length runners aren't necessary. Look at subie motors? 2 runners are almost double the length of the other. Turbo header short= better.

 

I'm still not seeing the benifits.

 

btw....I'm into veedubs too.... have a rail, a 74 super, and a 57 oval ragtop

 

A tuned header before the turbo, will help with turbo spool. You must arrange it so at the collector, the firing order flows in the direction the turbo is spinning. It doesn't do much but it helps.

 

Here's my old 1.9L 8V on carburation that made 159hp at the flywheel on Fuel.

 

This same engine, fuel injected on a ported intake manifold, with an aftermarket 3" TB wasn't anywhere close to the response as it was on the carbs. It was also down almost 22hp. You would think the torque #s would be up with the longer runners, but it was down 18 ftlbs. Still on Fuel.

 

 

The response on the engine with the butterfly's for each cylinder was insane. This effect is just going to be increased with boost.

[Pyrorocketeer]

Response will be quicker I already said that. nothing else tho. Still have to draw the air in through a plenum exactly like a regular intake manifold tho.

 

I know the response is very crisp on my rail... (basically same setup as ITB's.... twin 2 barrel webber 44's, on a built porsche engine)

 

tuned header yes, equal runners, no. you want that exhaust as hot as possible, and extra tubing will kill the temperature.

[..SSR..]

Log spools faster than equal length, ram horn, and top mount. Full-Race has a test on their site. They actually have a lot of tests on their site with manifolds vs spool.

 

He never did a before/after with the ITB's. Just take a look at Full-Races manifold.