[charlie66]

Originally Posted by Tom McQueen

Quick and dirty. Measure the length, width and height of the plenum. Subtract the width of the intake material. Multiply LxWxH. This gives ci.

Take the plenum ci and divide it by the ci of the engine. = ratio.

example

Plenum = 6"x7"x4" = 168ci
168ci / 198ci = .85

What do you mean by saying subtract the width of the intake material? would that be if you measured from the out side. So if I measured it from the inside I wouldn't have to subtract?

[Boostedbird]

Originally Posted by charlie66

Not bad first time out. That's probably a 10.00 to 9.90 1/4 mile pass. So you made 610 hp at 8.5 and you made this pass on 6psi ? Most likely that was with less then 600 to the wheels that gives me a good idea what mine will run , my car weighs 3400 and made 616. So I guess I should be in the 9's then. Thanks for posting that...

So if all you did was put a spacer on and port the sort turn at the top of the runners then maybe I can try this before I try making a new manifold just to see if I get similar results . A lot less work , hmm worth a shot I think. Thanks again...

Charlie, I guess it's hard to tell from the pictures, but there was over two full dustpan of material from the plenum when I was done removing the cloverleaf lugs and laying the walls back. The ports were widened a ton and shortened some from laying the walls back some. Then it gained some more volume from using the HVH over the 1" cloverleaf. Plus it's a Dominator plenum to begin with. If I were you and the math worked out I'd probably buy a Dominator Victor intake and use that for yours. Should have a big plenum then.
At the track last night I only went to watch an Outlaw race, but my buddie is friends with the track owner. He let me make two passes to test. At first I was all disappointed with what it ran. I thought " wtf?" It didn't feel right, and I was nervous with not being on the track in four years and having a lot of people there watching. I just made my passes and left. On the road home I rolled into a couple of times and looked at the boost gauge because I was thinking about it not being as strong as it was. Only 6psi! Damnit. I used push to lock line on my reference lines and the wastegate line pushed out lowering my boost. Those lines will not be on there next time.
This picture is what the intake looked like before.

[BruceWilkie]

Charlie, seeing you run EFI now, you may want to consider building a new intake. Plenty of places on the internet for info/ideas. Suggest YellowBullet. A modified tunnel ram could make a good starting point.

At your 4 cylinders @200 ci you'll want approximately a 300 ci plenum. Thats a box 15"x4"x5" (inner dimension)or a 15"x 5" ID tube. (total plenum = space between throttle plates and ends of runner. You could use other dimensions to come up with a 300 cfm plenum btw.)

Pypemax should give you an idea of how long you want your runners.

[twooldgoats]

Originally Posted by Jack Gifford

As I did with the blown hemi, since the magneto at the rear ruled out moving the blower back any more (and the hemi rear intake ports are WAY back). But doing that simply acknowledges the need for better air distribution- via a larger plenum or whatever. Off-hand, I think my port nozzle range was as much as #16 rear to #22 front. This could roughly translate to [maybe] a 25% air (and thus power) "deficiency" in the rear cylinders. That's why the blower manifold for my four-cylinder will be almost five times the engine's displacement (with the blower centered on the ports- a special center-outlet billet 14-71).

My situation is complicated by the shape of my blower outlet. The high-helix blower has a small teardrop-shaped outlet at the front of the blower on the bottom. That limits air distribution. I'm running .036" & .038" port injectors in the front, tapering down to .032" on both sides in the back. That keeps the EGT's close on all cylinders, but implies the front half of the engine makes more power than the back half. I've wondered what effect that might have in the long run, if any.

Jim

[johnta1]

Pypemax should give you an idea of how long you want your runners.

PipeMax I think also gives a plenum size in the data?



For a 4 cylinder engine, it would take a lot bigger plenum than what a V8 would use.

[Boostedbird]

Why would a 4 cylinder need a larger plenum than a v8? Just asking?

[charlie66]

Originally Posted by BruceWilkie

Charlie, seeing you run EFI now, you may want to consider building a new intake. Plenty of places on the internet for info/ideas. Suggest YellowBullet. A modified tunnel ram could make a good starting point.

At your 4 cylinders @200 ci you'll want approximately a 300 ci plenum. Thats a box 15"x4"x5" (inner dimension)or a 15"x 5" ID tube. (total plenum = space between throttle plates and ends of runner. You could use other dimensions to come up with a 300 cfm plenum btw.)

Pypemax should give you an idea of how long you want your runners.

Thanks Bruce, is this some sort of software? I'm not really good at that sort of thing.... ill try though...

[johnta1]

Why would a 4 cylinder need a larger plenum than a v8? Just asking?

To smooth out the pulses of the cylinders firing.

[charlie66]

Originally Posted by Boostedbird

Charlie, I guess it's hard to tell from the pictures, but there was over two full dustpan of material from the plenum when I was done removing the cloverleaf lugs and laying the walls back. The ports were widened a ton and shortened some from laying the walls back some. Then it gained some more volume from using the HVH over the 1" cloverleaf. Plus it's a Dominator plenum to begin with. If I were you and the math worked out I'd probably buy a Dominator Victor intake and use that for yours. Should have a big plenum then.
At the track last night I only went to watch an Outlaw race, but my buddie is friends with the track owner. He let me make two passes to test. At first I was all disappointed with what it ran. I thought " wtf?" It didn't feel right, and I was nervous with not being on the track in four years and having a lot of people there watching. I just made my passes and left. On the road home I rolled into a couple of times and looked at the boost gauge because I was thinking about it not being as strong as it was. Only 6psi! Damnit. I used push to lock line on my reference lines and the wastegate line pushed out lowering my boost. Those lines will not be on there next time.
This picture is what the intake looked like before.

If im going to make a new manifold , im going to make one from scratch. It took me a lot of months to get this one to work. I think the plenum of this one, if I did it correctly, is something like 74ci. That's way off from what Bruce is suggesting in size. I guess I have a winter project now . lol..

That sux about your boost being low but it still ran good. Just imagine what it will do at 12 and a tight converter1 I bet some low 9's!

I had some fun this morning. My girl and I went to this big car show and on the way home wound up being in the middle of a pack of new vets. As they were all passing me I cut in the middle of them , the one in front of the pack downshifted 3 times at 50 mph (guess he had a paddle shifter) He was about 200 feet in front of me when he hit it. I drove right to him like it was nothing. At about 20 feet off his bumper I lifted . As all the others drove bye they all gave me the thumbs up. lol.. I know that guy thought he was going to smoke me. Would of loved to tell him I only had a 4 cylinder.....

[charlie66]

Originally Posted by johnta1

To smooth out the pulses of the cylinders firing.

What would your suggestion in size be?

[johnta1]

Give me some engine specs:

Bore, stroke, rod length, intake diameter,cam duration, LSA, and I can run PipeMax on it.

[charlie66]

Originally Posted by johnta1

Give me some engine specs:

Bore, stroke, rod length, intake diameter,cam duration, LSA, and I can run PipeMax on it.

Ok Thanks..

4.090 bore

6.635 Rod length

2.15 intake valve

251 242 .050

114 lob separation

[charlie66]

Max rpm will be only 6500.Will be running high boost levels. Wouldn't be afraid of 50 psi just incase of that being a factor.. hahaha! seriously .....

[johnta1]

Stroke?
(3.75"? 4.25"?)

Also what is the head flow?

[charlie66]

Originally Posted by johnta1

Stroke?
(3.75"? 4.25"?)

Also what is the head flow?

sorry 3.75

[johnta1]

That's what I figured.

Looks like PipeMax doesn't actually give a plenum volume.
(it would be for a N/A application also)

It gives the usual min as the single cylinder size to the max of the total engine CID.

A calculator I have says for your engine it would be around 156 cubic inches.

But a lot of 4 cylinder racers have been using up to 2 times the CID of the engine to get the HP out.
(446 in your case?)

Plenum volume is not really understood as well as it could be.

Also the carb/Throttle Body needs to be bigger than a V8 type size.
(for the same reasons basically as the plenum)

PipeMax runner data (in inches):

- Induction System Tuned Lengths - ( Cylinder Head Port + Manifold Runner )
1st Harmonic= 33.676 (usually this Length is never used)
2nd Harmonic= 19.114 (some Sprint Engines and Factory OEM's w/Injectors)
3rd Harmonic= 13.344 (ProStock or Comp SheetMetal Intake • best overall HP )
4th Harmonic= 10.503 (Single-plane Intakes , less Peak Torque • good HP )
5th Harmonic= 8.521 (Torque is reduced, even though Tuned Length)

[Boostedbird]

Originally Posted by charlie66

If im going to make a new manifold , im going to make one from scratch. It took me a lot of months to get this one to work. I think the plenum of this one, if I did it correctly, is something like 74ci. That's way off from what Bruce is suggesting in size. I guess I have a winter project now . lol..

That sux about your boost being low but it still ran good. Just imagine what it will do at 12 and a tight converter1 I bet some low 9's!

I had some fun this morning. My girl and I went to this big car show and on the way home wound up being in the middle of a pack of new vets. As they were all passing me I cut in the middle of them , the one in front of the pack downshifted 3 times at 50 mph (guess he had a paddle shifter) He was about 200 feet in front of me when he hit it. I drove right to him like it was nothing. At about 20 feet off his bumper I lifted . As all the others drove bye they all gave me the thumbs up. lol.. I know that guy thought he was going to smoke me. Would of loved to tell him I only had a 4 cylinder.....

I would have loved to seen that! I like the new Vettes, but most of them guys are really cocky! After the track last night my buddie with the turboed LS Mustang put 3 lengths on a new nitrous Vette that money races around here. That guy has a mouth on him. It was great to see him get smacked on his own road! Sorry! Back to plenums!

[BruceWilkie]

Build your plenum so you can easily add more. I stated 1.5 x engine displacement...I'd start there.as a minimum. Test and add space and see what it does for you. Pypemax runner length factors the distance from valve center to manifold face.

[Tom Vaught]

A 156 cubic inch plenum volume works out to around a 80% vs displacement plenum which would be correct with a good flowing NA Intake manifold.

I always thought that a Wenzler Tunnel Ram intake manifold with half of the runners cut off at the base of the plenum and 4 runner plugs welded in even with the plenum floor would make an "easy to create and fairly cheap" large volume Boosted 4 cylinder intake
manifold.

You could also feed the plenum in the center and get better runner distribution vs feeding from a end position BUT with the right lid design and a "End Feed" with a throttle body deal would work well too.

Tom V.

[charlie66]

Originally Posted by johnta1

That's what I figured.

Looks like PipeMax doesn't actually give a plenum volume.
(it would be for a N/A application also)

It gives the usual min as the single cylinder size to the max of the total engine CID.

A calculator I have says for your engine it would be around 156 cubic inches.

But a lot of 4 cylinder racers have been using up to 2 times the CID of the engine to get the HP out.
(446 in your case?)

Plenum volume is not really understood as well as it could be.

Also the carb/Throttle Body needs to be bigger than a V8 type size.
(for the same reasons basically as the plenum)

PipeMax runner data (in inches):

- Induction System Tuned Lengths - ( Cylinder Head Port + Manifold Runner )
1st Harmonic= 33.676 (usually this Length is never used)
2nd Harmonic= 19.114 (some Sprint Engines and Factory OEM's w/Injectors)
3rd Harmonic= 13.344 (ProStock or Comp SheetMetal Intake • best overall HP )
4th Harmonic= 10.503 (Single-plane Intakes , less Peak Torque • good HP )
5th Harmonic= 8.521 (Torque is reduced, even though Tuned Length)

Thank you...