MyE28.com

I'm getting started on my next project, a turbo 68 2002. I really made a good find on this one and plan on a full restoration, but first things first, which is to make it go fast. I'm playing with different ideas for the intake manifold and one option that has surfaced is a setup with individual throttle bodies and a large custom plenum.

other than the coolness factor, what could be gained? I'm thinking that the standard throttle plate isn't that big of a limiting factor in a forced induction setup, but i have no real experience to base my guess on. Any thoughts out there on the benefit of 4 48mm throttles on an M10? vs say a single 60mm?

tia

You'll obviously get more cross sectional area with multiple throttles, i.e., potentially more air might get into the engine, but with forced induction you dont really need to care - infact, the usual tricks that people use to suck more air into NA engines are sometimes counter productive in turbo ones.

The reason ///M puts individual throttles on cars is for throttle response. Which you dont need to worry about on a turbo car

Disclaimer:
I do not design engines. I just read stuff

[QUOTE="Matt"]You'll obviously get more cross sectional area with multiple throttles, i.e., potentially more air might get into the engine, but with forced induction you dont really need to care - infact, the usual tricks that people use to suck more air into NA engines are sometimes counter productive in turbo ones.

The reason ///M puts individual throttles on cars is for throttle response. Which you dont need to worry about on a turbo car

Disclaimer:
I do not design engines. I just read stuff [/QUOTE]

While throttle responce may be one issue, its a lesser factor than the high RPM breathing increase from shorter runners and large plenum area. Theres no way long runners will breath well at 7krpm. the shorter runners will make good torque up high.

This increase in top end power also translates to forced induction. If your trying to make your trubo sytem breath well and 7k, then this is for you. If not, then stick with the longer runner manifold, its much easier to maintain, and makes great low end torque.

Russ

I will want to run the engine up to 7K... but my main question about the ITB's is the cost/efficiency ratio. In the 2002 i'll have plenty of gear, probably a 3.91 w/ 5 speed, the only thing i'd be worried about at low end is ripping the half-shaft apart.

so lets say i'm going to run 25psi, from my experience with hydraulics as the pressure and velocities increase the losses to friction increase exponentially. So if running 45mm sidedrafts on an M10 is worth 20 more hp with the appropriate camshaft then would opening up the intake with 48mm butterfly's at each cylinder produce an exponential increase in hp under 25psi? my intuition says it would. Of course i'm after a certain pressure in the combustion chamber and losses through the intake and cyl head could be made up by increasing the boost. So do the friction losses saved via the ITB's, cylinder head porting and larger intake valves add up to more hp under hight boost, or is just a waste of $$?

[QUOTE="Justin in C'ville"]I will want to run the engine up to 7K... but my main question about the ITB's is the cost/efficiency ratio. In the 2002 i'll have plenty of gear, probably a 3.91 w/ 5 speed, the only thing i'd be worried about at low end is ripping the half-shaft apart.

so lets say i'm going to run 25psi, from my experience with hydraulics as the pressure and velocities increase the losses to friction increase exponentially. So if running 45mm sidedrafts on an M10 is worth 20 more hp with the appropriate camshaft then would opening up the intake with 48mm butterfly's at each cylinder produce an exponential increase in hp under 25psi? my intuition says it would. Of course i'm after a certain pressure in the combustion chamber and losses through the intake and cyl head could be made up by increasing the boost. So do the friction losses saved via the ITB's, cylinder head porting and larger intake valves add up to more hp under hight boost, or is just a waste of $$?[/QUOTE]

Your on the right track, the whole system has to be able to fow air @ 7krpm. If your doing head work, using a better/more duration cam, open the exhaust and use the ITB intake, you will make way more than 20hp over a non tuned system at the same 25psi.

My only issue is the head itself. Is the M10 a 2v or 4v per cylinder head. I'm not sure a 2v/cyl head will breath that well, even with all the parts and work at 7krpm. The ///M cars make great hp at 6.6k rpm because of the 4v/cyl head and all the other stuff. You can get a 2v/cyl head to breath at 7krpm, but the cam will be so large, the idle will be crap and the turbo will be not be good at that much cam overlap.

RussC