Technical Theory : Plenum Design

[bszopi]

Ok, I've finally started working on my plenum. The original design wasn't going to work because of runner length (it would actually have been too long) and also the alternator. So I did some redesigning and came up with a design that will make the total runner length around 20" (stock is around 15.75"). And it should still fit under the hood. I haven't tested that yet, but from measurements and previous experiences, it should be pretty damn close. I'm hoping to have a decent amount done for the meet. I'll post pics after that...

[EspanolaGuitarista]

Are you trying to tune....

For horsepower and torque byzop? That would require variable geometry like the Ford modular engine. I'm unclear how your tuning for two frequecies. Maybe I'm out of my league on this one.

[bszopi]

I'm actually trying to bring the power band down some, so trying to increase low end torque. With a aggressive cam, these engines gain a decent amount of power from 3k and up, but the low end seems to lack some. So the idea behind the whole thing is to lengthen the runners in order to raise the low end torque, and thus shift the power band back down some. There has been a decent amount of research behind the project, but I won't really know anything until its done and tested....

[EspanolaGuitarista]

According to my.....

information a runner can only be tuned to one frequency. That frequency determines the rpm at which inertial ramming takes place. If anything you probably need to figure out where peak torque occurs with the cam you intend to use then tune for that range. I think for the street this would be effective since horsepower is based on peak torque. Have you ever heard of Rhodes lifters? They expand at a certain rpm to deliver more duration and of course lift. I think it is about 3000 rpm. That would solve your dilemma of low-end torque, then perhaps you could to tune your maifold for top-end. The best of both worlds. I think all of us put our minds together we could really come up with some great stuff.

[bszopi]

I would much rather keep it in the thread for others to read and input. What's the use of a public forum if threads topics like this are kept in PMs? Just my opinion...

Here is some info I used when coming up with the design:

Stock runner length is ~15.75", therefore...

For 2nd harmonic, RPM range is from 7459 to 9051 with a pulse strength of 10 percent
For 3rd harmonic, RPM range is from 5604 to 6405 with a pulse strength of 7 percent
For 4th harmonic, RPM range is from 4370 to 4886 with a pulse strength of 4 percent

With a 21" runner length, the values change as follows...

For 2nd harmonic, RPM range is from 5594 to 6789 with a pulse strength of 10 percent
For 3rd harmonic, RPM range is from 4203 to 4804 with a pulse strength of 7 percent
For 4th harmonic, RPM range is from 3277 to 3665 with a pulse strength of 4 percent

This would put the 2nd harmonic in the redline range of a slightly modded 3400. With the stock setup, the 2nd harmonic is way above what a 3400 can spin to (oh yeah, here is the link for this info: http://www.bgsoflex.com/intakeln.html ). There was some other research (as somewhat documented in this thread) to come up with the numbers, but that was probably the biggest factor. So feel free to go from there...

[bszopi]

Ok, so I changed my mind... I decided to give a quick peak, mainly because my daughter so so cute in this pic...

[EspanolaGuitarista]

Here's a link...

http://www.rhoadsproducts.com/

I think that would be a good way to go...
I see your point about the 2nd,3rd,and 4th pulses...
I wish I had that dynosim software...I'll just do it on paper.
From your design it looks as if your are increasing the runner length of the original manifold? I have an idea about using a 3 part fiberglass mold.
1st- The flanges and valley as one...
2nd- The runners
3rd- The plenum which would have a thick flange to mount the 62 mm TB.
Casting can be precise enough to eliminate mismatching of the parts.
My idea would probably not fit underneath the hood. Pro stock type.
I'll look up your website. Thanks for all the info.

Cute kid..Makes me wish I had one of my own.

[RacerX11]

Rhoads doesn't make any roller tappets (which the 3X00 engines have), and they don't have any 60degreeV6 applications.

The Rhoads lifter doesn't really give you any extra lift/duration at high rpm, it simply bleeds off lift/duration at the low end. To take advantage of this, you need a pretty agressive cam. The stock 3X00 cam is tuned more for low/mid rpm performance than top end power, so without going with a healty re-grind on the cam, I don't think you would gain much from it down low.

It is really a crutch for those people who want to run a hot cam, but don't want to sacrifice the low-speed drivability of the milder cams. You have to ask yourself, if the anti-pump up lifter was so good, you would be seeing them used in OEM applications.

Marty

[SappySE107]

are you gonna drop a 3400 into that red wagon in the background? The hp/weight ratio would be phenomenal! hehe

[EspanolaGuitarista]

I went to the rhoades site....

Yeah. They make a roller tappet but not for this application. Damn. It was an idea at least. Are the tappets for a 350 close to the Beretta. I'm sure the lifter bore's can be oversized a tad if need be. I'll look it up. I don't think it's a crutch. I think it's a great idea. Variable duration is always better than fixed duration. Look at the dyno chart on the Rhoades lifter page. They couldn't stabilize the power below 2000 rpm with the regular cam and lifters. Not only did it do pull torque below 2000 rpm but improves output until peak which with the lifters was higher. Higher peak torque,I preach again, means more horsepower. If they don't or won't make an application for this engine then I guess it's all pointless anyways. I think this engine can handle 6000 rpm. Of course 225's won't have enough bite, but that's another issue. Anybody make an LSD for this car?

[v6h.o.]

Re: I went to the rhoades site....

Anybody make an LSD for this car?

which transmission??


possibly you will find one here:

http://www.geocities.com/pontiacjeff/EPlsd1.html

i have a Race version 5spd getrag LSD....

but back to the topic at hand, im still learning and researching intake tuning.... much to learn.

[SappySE107]

Why wouldn't it handle 6000 rpm? BTW, I see I fairly easy 2 stage setup on your current design if you can cut open between the fuel rail.

[EspanolaGuitarista]

According to that calculator the optimum would be 24 in. runners. That would make the 2nd pulse hit in the max hp range and the 3rd hit in the max torque range. Is 24 " practical ? Probably not.

[Wolf]

Re: I went to the rhoades site....

Yeah. They make a roller tappet but not for this application. Damn. It was an idea at least. Are the tappets for a 350 close to the Beretta. I'm sure the lifter bore's can be oversized a tad if need be. I'll look it up. I don't think it's a crutch. I think it's a great idea. Variable duration is always better than fixed duration. Look at the dyno chart on the Rhoades lifter page. They couldn't stabilize the power below 2000 rpm with the regular cam and lifters. Not only did it do pull torque below 2000 rpm but improves output until peak which with the lifters was higher. Higher peak torque,I preach again, means more horsepower. If they don't or won't make an application for this engine then I guess it's all pointless anyways. I think this engine can handle 6000 rpm. Of course 225's won't have enough bite, but that's another issue. Anybody make an LSD for this car?

1st gen buick v6 lifters are very,very (but not exactly) similer (flat tappets at least) t

[XLR8ING]

24" sounds about right, since I had mine calculated to be 22" based on cam specs. Unfortunately 22" runners ain't easy to make fit under the hood.....so the next phase goes to a steel hood with a hole in it.