In the never-ending search for more horsepower AND torque, I am considering increasing flow - porting/polishing the intake side of things, maybe the supercharger, maybe adding a header. The car is a pretty typical modified MCS: 15%, Alta CAI, uuc cat-back exhaust, plugs and wires, GIAC, and dyno'd recently at 186 whp 163 torque.

My question is this - can increasing flow negatively effect torque, or will torque figures improve with any/all/ or combination of the above potential modifications?

 

is bad news for low RPM torque. This has to do with cylider filling, where long, narrow runners increase air charge velocity. As the cylender fills, the moving air in the runner acts like a ram and pushes more air in as the valve closes. I'm sure you've heard of "tuned" intakes? This is where they use this effect to maximize intake manifold efficiency at certain RPMs. In the new BMW 6, there's a version with three stage intake manifold, where it can change it's runner length so that it can provide "tuned" behavior over a much wider RPM range. I think the intake on the new M5 is continuously variable, providing optimal runner lenght tuning at any RPM.

Don't know how old you are, but there was a motor called the Ford 351 Cleavland 4v (heads for 4 barrel applications) it's ports were so huge that it was a low RPM dog, but really fun if you were running around an oval track! There are even aftermarket items that fill a bunch of the port volume just to inclrease low end torque. But this is mostly at the intake runner.......

On the other hand, polishing and matching all the parts in the intake track should give you less pressure drop, resulting in a more efficient intake, increasing overall flow capacity. Don't know if this will show up as a benefit at part throttle, the computer will just open the TB more to get more air into the motor.... But at WOT, you will have more flow capacity, and a higher theoretical top end.

Remember though, as you add more air into the motor, you need more gas, so watch the injector duty cycle or you'll run lean.

Matt

 

Have you thought about having your engine blueprinted? it will show you where you should add the horsepower and such.. it is costly, but in the end it is a great knowledge tool. I know I will have mine blueprinted in a while after the Twincharger has all of it's bugs worked out, add the clutch, flywheel and LSD.

 

Define "blueprinted".
Will you be disassembling the entire motor?

 

Blueprinting the engine does no such thing. It involves dissassembling the engine and making sure everything is within spec of the "blueprint".

--
Cheese

 

it may not add horsepower, but it will tell you where you can add the horsepower, and Macncheese, have you tried this? I know i haven't but i have had my dad's F150 drag truck blueprinted, and yes it did show us where to add the horsepower..

 

clarify, since blueprinting is really just a careful assembly/tolerancing technique.

 

Yes, I've personally blueprinted engines. I dont quite understand how that would tell me where to add horsepower? Out of curiosity, where did it show you to add the horsepower on your dad's F150 drag truck?