Manifold To Access Rear Plugs

[TTstealthracing]

Originally Posted by supermac

link aint working

http://gatherings.3si.org/ECG2005/pi...s/image61.html

[supermac]

well guess ill go back to the drawing bored then and make the plenum look more like that box shaped thing. but it still probably wont fit under a stock hood. there is only about an inch or 2 of clearance under there.

[pearlwhitwin]

i still think you should try this design if you can get it close to clearing the hood.

[supermac]

It wont. its not possible. ive tried.

[pearlwhitwin]

oh ok well nevermind then just an FYI for you and others i found some good reading that a member posted awhile ago. maybe try sticking to these principles would be good?

Originally Posted by mjannusch

In "Forced Induction Performance Tuning" (A. Graham Bell), he says:

Quote:
The three things we are interested in with regard to the plenum is its volume, how equally it distributes air to the individual cylinders, and how the openings to the individual runners are formed so as to maximise flow. Some tuners claim that the plenum volume must be carefully monitored, and that volumes of between two and three times the engine size work best. I disagree, having found that anything in the range of 0.8 to 1.5 times engine capacity works well in 3 to 6 cylinder engines, while 8, 10 and 12-cylinder engines are usually happy with considerably less volume.

Regarding runners inlets:


Quote:
Preferably, the air should not have to make a sharp turn from the plenum into the runners, and in turn the runners should have a nicely formed bellmouth to help flow. Ideally, we don't want the plenum wall closer than 1.5 times the runner diameter from the bellmouth - twice the diameter is better, if possible.

Regarding runner design and size:


Quote:
The runners are a real tuning tool. Both their diameter and length have an influence on the shape of the power curve. The diameter basically fixes the rpm at which the engine makes best hp, so while a big fat runner will let the engine breath freely at high revs, it will be down on power at low rpm. Runner length tends to 'rock' the power curve around the point fixed by the runner diameter. Therefore, long runners will push up bottom-end power, but once past the peak the engine will fall on its face. Short runners do the opposite - they kill the bottom-end and help the engine maintain power way past the peak.





There's a chart for determining runner diameter and length. For a turbo street/rally car he's recommending a runner length of 350-400mm (13.8" to 15.7") and a diameter of .99-1.05 times the intake valve diameter. I don't know what the diameter of our valves are, so I can't give the math here.

For a turbo circuit/drag car he's recommending a runner length of 260-300mm (10.2" - 11.8") and a diameter of 1.12-1.18 times the intake valve diameter.

I assume the runner diameter calcs are supposed to be the diameter of BOTH intake valves times the indicated values. Times one would seem to be awfully small of a runner.

The runner lengths he's recommending are measured from the valve seat to bellmouth face in plenum. Our lower intake manifold and upper plenum are certainly longer than what he's indicating to be the lengths to shoot for.

Thoughts? Comments? Is he full of it, or is this something good to shoot for?

[supermac]

Just a quick note. with the boxed shaped plenum that everyones been posting... keep in mind that you will have to replace your factory outter studs in order to bolt this down. we will be able to suppoly hardware to install a neew plenum, but you will still have to remove the studs from your factory plenum.

if you dont understand y... then you probably shouldnt be removing the plenum for a new one.

thanks,
chris

[servidjo]

Keep up the good work Chris. You have A LOT of suggestions and ideas being thrown at you.. and I know you are trying to please everyone, and thats not easy.. especially in with this platform. Im sure the final product will be great, with either design.

[Dartvdr]

Keep up the good work Chris. You have A LOT of suggestions and ideas being thrown at you.. and I know you are trying to please everyone, and thats not easy.. especially in with this platform. Im sure the final product will be great, with either design.

Your hard work is not without appreciation.

Dartvdr

[TTstealthracing]

Originally Posted by supermac

well guess ill go back to the drawing bored then and make the plenum look more like that box shaped thing. but it still probably wont fit under a stock hood. there is only about an inch or 2 of clearance under there.

hey Chris I saw that box type plenum installed and fits good with the stock hood and when it was on the dyno it put down 20/30 more Hp on a stock set up

[supermac]

that box style might fit under the stock hood but it wont fit the the stock radiator fill neck. there is no way it would ever clear that.

also. we spent all day trying to figure out a way to make a plenum that woudl actually be benificial to the car and still clear the hood while having a drivers side Tb and im sad to say its just not going to happen. even on teh passenger side without removing the fill neck it just cant be done like what people want. it would have to be less than 6 inches wide and less than 2 inchess tall to even fit under the hood, and then you have the tb to deal with the fuel rails, the fill neck, the hood liner, just lots of things that dont make it possible.

we will continue to do our short runner manifold to access the rear plugs, but the super short plenum on top of the lowe intake just isnt going to happen unless people want to modify the hood. we will make them for people on a special order basis only. and we can even do them out of aluminum.

so... from now on. we will be focusing on doing the regular plug access plenum only.

thanks,
chris