Type IV plenum intake manifold questions..., Why single and not double like the 911 motor? Options

[McMark]

To what end? Why spend the time engineering? And how will you know if you actually made an improvement?

[r_towle]

I suspect the 911 intake developed two 'plenums' mostly due to space constraints. I seriously doubt there is a payoff to the development for a dual plenum for the T4.

Also, IMHO, if you're going to modern fuel injection in a street car, one of the huge benefits is being able to use a single throttle body. Remember that any number of throttle bodies (more than 1) must still be accessible and adjustable for syncing, just like carbs. PITA.

Aside from variable intake length (VarioRam) and variable valve timing (VarioCam) most engine engineering developments are going to be of more benefit in the fuel economy and emissions department. If you're looking to increase engine output, as in horsepower or torque, stick to the basics. Displacement and forced induction. There isn't a fancy 2.0 that will compete with a 2270.

My Idea is more for efficiency, not to increase HP. I just want the motor to breathe easier.

The 1.7 is severely under aspirated.....IMHO. All the corners it turns to get into the plenum and transitions into the runners can be easily improved on.

Spend your money on new 1.8 liter AMC heads.
It won't breath any better until you fix the heads.
1.7 heads have way to much restriction to bother doing any supposed improvement on the intake.....
The exhaust port is the issue.

[larss]

Not that it adds wery much but this is my expetiment:
Dual TB


Lars S