[Tom Vaught]

Originally Posted by johnta1

It would be interesting to hear John M's views on the intake.

Yes it would. I have seen pics of what John M did on Brian H's intake to make it work right.

He can post the mods if he wishes.

Tom V.

[Jack Gifford]

Originally Posted by charlie66

... It just dawned on me that my elbow probably adds to my plenum size...

If considering only full-throttle power potential, why wouldn't ALL of the intake plumbing (post-turbo) contribute [at least somewhat] to the plenum volume?
[A stupid question maybe...]

Where are fuel nozzles?

[Tom Vaught]

The fuel Injectors are in the "OEM Typical Location" above the intake manifold gasket flange.

On turbo cars occasionally you will see the pipe from the turbo to the "inside Inter-cooler " is large and the pipe from the inter-cooler to the throttle body is large.

Obviously the intercooler is in the middle of the flow circuit so the "plenum" does not exist all the way to the Turbocharger compressor outlet. The intercooler discharge point is basically the end of the "plenum" when the Throttle valve is at WOT.

Tom V.

[Jack Gifford]

Okay. But there appears to be a large volume of ducting between intercooler and throttle body, which perhaps contributes to "plenum" volume at full-open throttle? Charlie was only considering taking into account the elbow's interior volume, but that looks like only a fraction of the whole duct from the intercooler.

[BruceWilkie]

Possibly the manifold sees ducting to manifold plenum as throttle??? If ducting is say 3 inches the velocity would be fairly high and a sudden large change in area in the transition to "sudden" large volume area would "dampen" velocity. A plenum on an NA manifold behaves as a velocity dampener after throttle and before runners.

[Boostedbird]

Originally Posted by BruceWilkie

Possibly the manifold sees ducting to manifold plenum as throttle??? If ducting is say 3 inches the velocity would be fairly high and a sudden large change in area in the transition to "sudden" large volume area would "dampen" velocity. A plenum on an NA manifold behaves as a velocity dampener after throttle and before runners.

This is what I was thinking also. The air would need to slow down to turn into the runners properly. On a street car you also need a fairly large gulp volume for when the throttle is cracked there is a supply of air for the engine to digest. On a race car I read that gulp volume isn't as important and the plenum can be smaller. Idk. I'm just trying to get at the need at designing the plenum for more than just volume. I know on Charlie's car the air doesn't carry fuel, but there is still the need for smooth flow with good distribution. It doesn't seem like the charge pipe can be considered as plenum because the engine doesn't draw from it directly, and there probably isn't enough time to get air from the charge pipe into the cylinder before the valve closes.

[Boostedbird]

Or I'm wrong and it is. Lol! The way that I think about it is that no air moves until the valve opens. The air is just under pressure. When the valve opens the cylinder is going to be filled quickly, but only with a certain volume of air and only in a small amount of time. So how much air upstream of the runner is making it to the valve each time it opens? Somebody help me out with my thinking! Lol

[Tom Vaught]

If the plenum is too small the runners are all fighting for air at higher rpm, like a "tug of war" deal in a room.

With a larger plenum, the engine runners want the same air flow as before but "the table is full of food, so they are not fighting over the SAME piece of pie". With the Boosted Air coming into the intake plenum area, the closest runners or the strongest runners always get the larger share of the "food". This happens with even NA intakes.

So the bigger Plenum allows each runner to basically not have to share its appetite for air flow. I have video of air flow (with a coloring agent) vilmed in a intake plenum under different rpm conditions. A Small open plenum has a lot of violent air moving quickly back and forth across the plenum. A dual plan intake is less violens at the runners are basically "quiet" 1/2 of the time, a space in time between inlet events.

Tunnel Rams are big enough so that each signal from the runner tries to turn on a specific booster of the dual carbs. The rest of the air acts like a cushion so that the air is not so violent. Why a plenum spaces helps at times and a 2" spacer helps more than a 1/2" spacer.

Tom V.

[Jack Gifford]

Originally Posted by BruceWilkie

... Possibly the manifold sees ducting to manifold plenum as throttle???...

That very well could be the case. I don't really know much about "plenum volume". But when Charlie mentioned adding in volume of the elbow, I wondered why consider the elbow and not the ducting leading into it?

Incidentally, the main reason I'll be concerned about plenum volume is to dampen the pulsing from the rotors of a Roots blower- and also some concern for more-equal pressure across all intake ports.

[Tom Vaught]

Originally Posted by Jack Gifford

Incidentally, the main reason I'll be concerned about plenum volume is to dampen the pulsing from the rotors of a Roots blower- and also some concern for more-equal pressure across all intake ports.

Banks has worked in the past on Geislers engine/vehicle "Hanky Panky" Bonneville Studebaker with using a Intercooler between the Blower and the Intake Runners.

The inter-cooler dampens out some of the rotor pulsations.

Tom V.

[wheneaglesfly]

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.....

That is Awesome !

[Jack Gifford]

Originally Posted by Tom Vaught

... The inter-cooler dampens out some of the rotor pulsations...

Intercooling certainly would be desirable- especially from a power-producing standpoint. However, It wouldn't have the "old school look" that I'm going for. And besides, space is at a premium inside the drop tank body.

[wheneaglesfly]

[wheneaglesfly]

[wheneaglesfly]

My bud Ed & Me built the One Off Air to liquid charge air intercooler last month Jack.
We built 2 actually identical. Owners on North side of Chi town.
One for the Audi R8 V10 pictured here.
Same as Lamborghini Gallardo just reskinned body panels.
Target HP was 1,000 on pump gas to the rear wheels.

Just a few ideas to share when packaging is an issue.
The Cooling radiator is up front for the liquid side of the Intercooler.

[wheneaglesfly]

The Main intercooler cores are universal,
purchased pre made.

Fab up the box & all charge air cold side piping.

[Tom Vaught]

I realize that the "Bomber Tank" vehicles are more period correct for a earlier time at Bonneville, Jack. Just wondering why you are using a 60s 4 cylinder engine with state of the art style valve train engineering and a 60s style roots boosting device (roots blowers were around much earlier) and no inter-cooler technology. Inter-coolers were also used years earlier on some stuff. But I can understand the "Package" deal.

The Geisler Studebaker is a early 50s vehicle and uses a Inter-cooler.

Tom V.

[charlie66]

wow this thread really took off.

I haven't been on in a while because I had some unfortunate luck . My 4 cylinder finally gave out . The block lost number 4 cylinder. At first I thought it was 1 crack, but after getting it all apart I found 3 more up on the deck in-between the bolt holes and the water holes.. So now im getting my other spare block ready for the machine shop. Its kind of a shame because I have it running so good now. I think I weeded out almost all the bugs. I built this block back in 2009, and have been killing it with 30+ pounds of boost since 2010. I think it lasted a long time being how I beat so hard. I have had it up at 44 psi a few times , and a whole lot at 35. I think it goes to show how strong these blocks really are. I also have to say that this block went through all the learning stages which I think may have made it even more stressful for it. So maybe by having it all ironed out now, the new one will last longer...

Thanks for all the reply's here. I will have to go back and read them all when im done with my motor...

[Tom Vaught]

Sorry to hear about the block finally failing. Stuff gets tired Charlie, at some point.

We dynoed 3 different engines (same basic engine architecture) and all three failed about 1600 engine dyno HOURS on the things. They JUST WORE OUT!

Don't beat yourself up on this deal. YOU DID REALLY GOOD OVER THE YEARS.

Tom Vaught

[BruceWilkie]

Sorry to hear that Charlie. How stock was bottom end?