who has done this??

[pboglio]

O.K.

Finally fell back on a computer program to verify some stuff. I used "Engine Analyzer Pro" (limited shareware version) www.performancetrends.com . This thing does wave tuning, can only guess its accurate, but its locked in for a Buick Reagal V6 naturally aspirated for the shareware version. I don't care because it has inputs for runnner flow drag coefficient, runner dia, runner length, runner taper angle, intake manifold type, plenum volume, etc etc. It's otherwise fully functional. Pressure wave and temp graphs that update real time during the crank rotation. You can also figure out how much an exhaust system thats rated for 450 cfm (like my small greddy) vs. a big 3" Buschur (750 cfm @.75psi pressure drop) costs in actual torque. Very cool stuff.

SilverbulletAWD was right, a 1.5* degree TOTAL taper is perfect for the intake runners. I simulated a 5* total taper and lost over 40 ft*lbs of torque almost everywhere in the rpm range. Using a very large plenum gained 10 ft*lbs everywhere, 3000-7250 rpm. Looks like no downside to a large plenum, especially at high rpms. Lag may be increased due to volume (like a big front mount) but it would be worth it looking at the torque gains. Going from 12" runners to 6" runners just shifted the torque curve from low-midrange to midrange-high rpm, no real secret here. The difference between running 6" length and 7.25" length was worth noting though. The 7.25" runner length gained 5-6 ft*lbs just by adding 1.25" over the shorter runner. The runner diameter is EXTREMELY critical though. The difference from 1.75" dia (ideal on this engine) to a 2.0" diameter was as much as 40 ft*lbs LOSS in the midrange at some points. Going smaller to a 1.5" diameter LOST even more, almost 50 ft*lbs over 5000 rpm.

I would say your average do it yourselfer would have to build over 10 prototypes using a hit or miss method. Using the above software it would still take a few prototypes to get it right. I'm buying the full blown software ($450), could be useful for exhaust system testing etc. too, along with cam and valve timing adjustments etc. But I just realized how difficult it would be to actually gain any power. The geometry has to be JUST right within a small tolerance otherwise you could see HUGE losses. Since my current setup really limits me to 7000 rpm (HKS cams, stock valvetrain) and my turbo is just about done by 6000-6500 rpm, I think I'll stick with the stock manifold. Building an intake manifold looks like the easy part, actually getting it to make more power and not less is the tuff part. Cheers.

 

[goonie]

PBOGLIO
one more question about the volume size after the throtle body?
(may be i missed it in the threads)
but is there a minimum volume size needed after the throtle body? or is it possibel to mount four equal runners directly after the tb?
with the tb positioned in the midle of the head (between cil 2&3)
something simular like the one in the picture you posted?
tia

 

[pboglio]

PBOGLIO
one more question about the volume size after the throtle body?
(may be i missed it in the threads)
but is there a minimum volume size needed after the throtle body? or is it possibel to mount four equal runners directly after the tb?
with the tb positioned in the midle of the head (between cil 2&3)
something simular like the one in the picture you posted?
tia

You don't need VOLUME, you need a large AREA change between runners and plenum. Its a balance between big AREA (wave tuning) and getting a good shape or turn into the runners (reducing flow losses), this requires both AREA and DEPTH or length, this dictates your minimum volume. Wave tuning only requires a big AREA change to cause wave reflection, although plenum volume helps out a bit at high rpm, not much though. It doesn't NEED to hit the back wall of a Plenum or anything. Just look at that FORD RS200 manifold I posted, every runner faces the open throttlebody, no back wall to bounce off. The waves will reflect based on hitting the wide AREA opening of the plenum.

Look at Magnuse's Manifold, the plenum is TINY. But it works great because each runner dumps into an AREA change thats the entire WIDTH and HEIGHT of the plenum. Remember, only one runner breathes at a time. The plenum DEPTH (front of car to back etc) is used to help turn the flow into each runner to reduce flow losses. For trying to fit into a very confined space, Magnuse's looks like a very good design considering the space requirements.

To be an effective sheetmetal intake, your runners are going to be around 6" (for instance)and of equal length. Your plenum needs to have a LARGE area facing the runners, and then somehow merge with the throttlebody without hitting the firewall. I think any type of bend BEFORE the throttle body is O.K., doing it afterwards creates more flow losses. Tapering Plenums are used for TURNING the flow minimizing flow losses or turbulence. The number #1 (drivers side) cylinder leans because it gets MORE air, its on the outside of the turn. The number #4 (passenger side) cylinder goes rich because it is on the INSIDE of the turn, right after the throttle body opening, which also causes a local flow loss and LESS air. The velocity BELLS help here. You actually want to turn the manifold and air flow WELL before the air ever gets near a runner, keeping air flowing EVENLY to all cylinders. The runner INSIDE diameters should be very close to stock, unless you have the software to find the optimal diameters. Those are your only limitations, base on Performance Trends "Engine Analyzer Pro" software and info taken out of "Scientific Design of Intake and Exhaust systems" and basic fluid dynamics. Go crazy

 

[95kate]

oh yeah!! well i know my a,b,d's