Carl Fausett

Finished Size: With these intake runners installed on 32v heads, here are your new specs:

Intake runner length from plenum mounting flange to back of valve = 10.93"
Intake runner diameter at plenum mounting flange = 2.25"
Intake runner O-ring (supplied) outer diameter = 2.88"
Height of the 928MS intake runner = 3.90" or 99.08mm
Space envelope: Intake plenum flange to bottom of hood at front = 3.70"
Space envelope: Intake plenum flange to bottom of hood at back = 4.70"
Space envelope: Max plenum size is 20.6 Liters without extending outside the fuel rails.

Carl Fausett

These pics show how I finished my installation

Carl Fausett

From the front....

ptuomov

Looks bad ***.

Is your 800 hp target at the crank or at the rear wheels?

Lizard928

Looks good Carl,

I am curious as to why you didn't just use a 90 to go into the drivers side plenum instead.
And possible smooth out the transitions to the two plenums.

dcrasta

Awesome as usual.!

Dave928S

I'd be interested to hear your thinking on that issue too. I would have thought that putting a 90 at the end would favour that plenum ... but can't think of a smooth balanced flow alternative to feed both.

I assume that if the primary tube is big enough, relative to the two secondaries going to the plenums, the secondaries act as if they're just flowing from a chamber, and only need to be exactly equal in length and diameter to get balance???? Did you flow test that part of the configuration to determine sizes?

Nice work!

Carl Fausett

There are two reasons for taking the air out of a log at that point:

1) If we would have used a 90 into the second plenum, the air flow to the two plenums would be different, and we wanted them to be the same.

Remember there are 3 inlets into these plenums, not 2. The "balance tube" in this design is not a mear 3/4" tube (like a true balance tube) but rather a full 3" crosspiece - the same size as the inlets.

That makes the plenums actaually a circuit, and equal on all sides and also front-to-back. Again to the firing order... whenever the firing order fires the same bank two times in succession (which happens twice each cycle) one plenum will have higher pressure in it than the other. This tube not only balances the air pulses, but actuall spills and shares the air with the other plenum that needs it.

You might ask... if the two plenums are actually one large circuit - why not make just a single plenum and be done with it. We tested the strength of the composite runners to make sure they could handle the tension of the heads moving away from each other as the motor heats up, and they could.

But, the single plenum would have been enormous and thats why we went to twins. These plenums are 12.54 Liter in volume now (not including the ram tube) and thats already bigger than I wanted by about 2 liters. Our math showed that as a single plenum it would have been about 18 liters and I thought I would loose too much throttle response at that point (supercharged).
If I were running NA, I would have done just a single larger plenum.

2) The second reason is to maintain the pressure at the doors of both tubes.
This is a pressure system, and the pressure at the inlets will be higher if the outlet is not at the end of the tube. The next time you are in a restaurant with forced-air HVAC in the rafters, or if your home has a forced-air system... go look at the placement of the registers in the ducts.

The engineers will never place a register at the end of a run. You get very poor pressure that way. But rather, the duct is closed off beyond the last register/runner so as to keep the pressure up in the duct, and ultimately move more air at higher velocities as a result.

A single-inlet/single outlet system is not the same. Yes, if this was a single inlet and single outlet system, you would just hook up the tubes straight-away and be done with it.

Carl Fausett

Note the nice, long and relatively flat torque curve.

Boost reduced at 6100 RPM due to valve spring float we think, so once that is corrected, the curves should not drop off at the top end.

This was on 91 octane pump gas, no additives.

smith 928

How much boost?

Carl Fausett

10 psi. 6.54 liter 32v stroker motor.

smith 928

Is that RWHP or Crack hp?

smith 928

This is in your race car?

Carl Fausett

It's a chassis dyno...so those numbers are rear wheel HP.
Figure about 860 Crank HP.

toofast928

Impressive!