Contour Enthusiasts Group Archives Forums Modifications Forced Induction Turbo Kit..... Pic #1

yeah, baby! How much longer till it's for sale? Me wants! Me wants!

Thats not entirely true. However they will work, and since you will have a turbo on the engine the boost will cover for the most part the shortcomings of the log manifolds. Log manifolds will be allright on a street turbo set up.

NICE!!!!!!
May 1st

im with redsvt on that one

equal length headers will make more power even with turbo but in most cases there isnt the room or the cost is to high

we have tested and seen 50hp out of equal length headers vs a good log manifold on cars but they were race cars with everything gutted and lots of room

tom

Guess we have to agree to differ......

Yes, my impression was that although scavenging isn't necessary for a turbo motor, backpressure is a concern. Unequal length headers will cause certain cylinders to have more backpressure than others. Turbocharging isn't totally 'free' horsepower.

So, is it a packaging issue? Or a cost issue? I'd like to see a pre-production schematic on how the headers are going to collect.

If you increase the path to the turbo the lag will increase.
This may be no problem on an "all out" race engine setup, but if most definitely noticable on a street driven car.
Those large tube log style manifolds will reduce lag and still flow plenty of air at high rpms.

Yes back pressure may be a bit uneven at lower rpms, but in full song the difference will likely be fairly minimal considering the turbo size and the engine's efficiency.

BTW - no there really isn't room for equal length tubes anyway.

Increasing the path to the turbo will not cause lag. With a turbo exhaust the only restriction you want in the system would be the turbo itself.Once the engine fires the exhaust in front of the turbo is pressurized because the turbo is the restriction. Lag is more a product of turbine wheel size and A/R ratio of the turbine housing.

So you are saying that initial spool up is not affected by the length of piping before the turbo.

Equal header length only aids one small rpm range. Exactly the same as the intake, that is why we have dual runners on our cars (sorry zetecers). Mazda once had a valve in their exhaust to give it dual header length. These benefits will help all cars, turbo super NA. But on forced induction you will not notice the difference.

As far as the spooling, this is determined by two things turbo mass and pressure. Short headers give less volume thus faster spool up. But do the math, >2.5 liters per rev, volume of the headers is going to be much much smaller, so this should be pretty insignifigant.

In and ideal engine your would have trombone pipes on the intake and exhaust that varied infinately from 25 feet to about 5 feet. I think I heard that variable intake could increase your map by up to 3 psi, but only at a specific rpm. BMW M3s have an infinitely variable intake, but we have no room for that (maybe on a zetec).

Take this with a grain of salt, I only speak from my limited experience.