intake manifold design

Posted By: feets

intake manifold design - 08/11/10 06:15 PM

It's been a while since I read Corky's book so I don't remember all the ins and outs of EFI manifold designs.

Fred has a tunnel ram and plenum design for his monster motor. Most guys use a typical 4 bbl intake with a throttle body. Others use a round throttle body on a 90* neck for a carbed style intake.

How do you determine the best manifold for your EFI engine? I know the long runner intakes are popular on the late model engines but what size plenum are they using?

My intake is a Weiand tunnel ram with a 390 cubic inch plenum on top. Is that better suited to street use, track use, or what?

Posted By: mr_340

Re: intake manifold design - 08/11/10 07:09 PM

Maybe define "best" a little better? It looks like the F1, IRL type engines have individual runners and throttles. Tuning the length of the runner would be easier that way with the common plenum area above the throttle plates. If I was looking for maximum HP, I'd look into following their lead. The single TBI on a single plane intake looks cost effective, but probably is not the optimum power wise. Since you are using the turbo approach and from what I've seen of your car, I'd say you are well below F1 budgets (as we all are). I was told by a guy at Rousch back in 1998 that the injection near the head was done for emissions, not max. power. He said for maximum power the injectors get moved up to the top of the runner. I've seen an F1 engine with the injectors above the entrance and fogging the fuel in on top.

Posted By: Mr.Yuck

Re: intake manifold design - 08/11/10 07:18 PM

I recall reading something like that the best intake for boosted applications should have equal length runners.

Posted By: feets

Re: intake manifold design - 08/11/10 08:05 PM

Quote:

Maybe define "best" a little better?

Sorry, that was poorly worded.

I was wondering the best application for each type of intake manifold.
large plenum
small plenum
converted 4bbl
long runner
short runner

Posted By: Mr.Yuck

Re: intake manifold design - 08/11/10 09:41 PM

going to make something Feets?

Posted By: Jerry

Re: intake manifold design - 08/11/10 10:30 PM

Even with EFI your best bet on intakes is to match them to RPM ranges that are most operated in. therefore, longer runner intakes will still build more torque you just don't need them now for fuel distribution. short runner intakes are better for higher RPM. in todays world of castings being converted, usually intakes that are dual planes have smaller crossectional runners and longer runners so they are more suited to milder engines. larger single planes have both larger cross sections and shorter runner length ideal for higher HP and more RPM.

Plenum volume is a whole other consideration. if you have an engine that has wide rpm swings like a nascar stock car you would prefer a larger volume plenum. an engine like a drag car designed to work in a narrow RPM band can get away with a smaller plenum as most of the time your at WOT anyway.

Posted By: feets

Re: intake manifold design - 08/12/10 02:33 PM

Quote:

going to make something Feets?

I already have:

My mind is just wandering a little.

An idle mind is a dangerous thing.

Posted By: Mr.Yuck

Re: intake manifold design - 08/12/10 02:46 PM

Quote:

Quote:

going to make something Feets?

I already have:

My mind is just wandering a little. A

n idle mind is a dangerous thing.

looks like that started life as a tunnel ram.

Posted By: feets

Re: intake manifold design - 08/12/10 02:55 PM

Quote:

looks like that started life as a tunnel ram.

Quote:

My intake is a Weiand tunnel ram with a 390 cubic inch plenum on top.

Posted By: OzHemi

Re: intake manifold design - 08/12/10 04:14 PM

How about the edelbrock one with the forward facing throttle body? (I've got the LS1 version on the Torana)

Posted By: furious70

Re: intake manifold design - 08/12/10 04:17 PM

Quote:

He said for maximum power the injectors get moved up to the top of the runner. I've seen an F1 engine with the injectors above the entrance and fogging the fuel in on top.

I believe this has more to do with the rpm those engines turn than anything else.

Posted By: The Shadow

Re: intake manifold design - 08/12/10 10:44 PM

I believe your reading into this too much if it's for a boosted application.

Just look a roots manifold.

Posted By: HEMIFRED

Re: intake manifold design - 08/13/10 12:26 PM

Quote:

I believe your reading into this too much if it's for a boosted application.
Just look a roots manifold.

Just as with port shapes and having nice blends with forced air all rules regarding n/a go out the door. exacting size numbers and runner lengths mean nothing. I only have a tunnel because I had it sitting around and cost was zero

Posted By: blownEFI

Re: intake manifold design - 08/13/10 02:25 PM

Street car vs. Race car makes a difference. Force inducted race car doesn't care too much about intake design as has already been stated in this thread. However, a street car is not on boost 99% of the time and therefore behaves the same as naturually aspirated, so manifold design will have an affect on driveability. If you only care about WOT HP on boost then slap on any ole thing you want and it will probably function.

Posted By: furious70

Re: intake manifold design - 08/13/10 03:37 PM

Quote:

Street car vs. Race car makes a difference. Force inducted race car doesn't care too much about intake design as has already been stated in this thread. However, a street car is not on boost 99% of the time and therefore behaves the same as naturually aspirated, so manifold design will have an affect on driveability. If you only care about WOT HP on boost then slap on any ole thing you want and it will probably function.

I agree with this, that's why I converted an rpm performer intake for my efi. While I'm still running N/A at this point, the best advise I was given was use the intake you'd use on a carb'ed N/A engine since it's 100% a street car (and heavy at that).
I did look at trying to chop and channel an LT1 intake, thinking an OEM designed efi intake would be a great place to start, but with a/c in the conventional location it wasn't going to work.

Posted By: TheOtherDodge

Re: intake manifold design - 08/13/10 05:31 PM

"Street car vs. Race car makes a difference. Force inducted race car doesn't care too much about intake design as has already been stated in this thread. However, a street car is not on boost 99% of the time and therefore behaves the same as naturually aspirated, so manifold design will have an affect on driveability. If you only care about WOT HP on boost then slap on any ole thing you want and it will probably function."

Hense, my intake is an M1-FI style. I thought about making another intake using the M1 base/runners and doing something similar to what Feets did, but then thought about what was said above.

Posted By: The Shadow

Re: intake manifold design - 08/13/10 11:30 PM

Quote:

Street car vs. Race car makes a difference. Force inducted race car doesn't care too much about intake design as has already been stated in this thread. However, a street car is not on boost 99% of the time and therefore behaves the same as naturually aspirated, so manifold design will have an affect on driveability. If you only care about WOT HP on boost then slap on any ole thing you want and it will probably function.

I really can't agree on this theory
The car will drive around just fine with efi as it's tuned with the map/fuel. It might not be optimal but it works.
I would think converting a single 4 manifold over a tunnel ram proves my point. With the unequal runner length and usual poor fuel/air distribution characteristics and issues they still work.
An equal length runner intake should blow it out of the water but the don't seem to.
Show me a factory F.I. manifold with unequal runners

Posted By: DaytonaTurbo

Re: intake manifold design - 08/14/10 05:56 AM

Quote:

Show me a factory F.I. manifold with unequal runners

Modern factory boosted efi cars are designed around providing fuel economy and passing emissions standards. They aren't designed with race-only in mind. I would still say that a crappy 4bbl intake is still going to perform lousy on a boosted vehicle if anything just from air/fuel variations from cylinder to cylinder. I think you at least want a reasonable intake.

Posted By: whiplash

Re: intake manifold design - 08/15/10 03:13 PM

another thing to keep in mind is that most of the manifolds we can get our hands on for the older engines are/were/ designed for "wet flow" applications. I would venture to guess even the ones with efi bungs cast in them still were designed with wet flow ideals. For efi, we have to think about dry flow before the injector. You want some turbulence before the injector to start the mixing, and good velocity. But, the problem is, when you throw boosted flow velocities in the mix its tough to get all that, plus good injector targeting with the older intake openings. Just look at a modern engine and how the intake port has injector openings to help direct the flow at the back of the valve. I know on my EFI 383, you can see the clean spot on the opposite side of the intake port (bottom) from where the injector spray is hitting. Most likely at idle low flow conditions. If I could do it again, I woul look at a short tunnel ram with the injectors underneath to try and adjust that angle.

Posted By: Five9Dak

Re: intake manifold design - 08/17/10 12:30 AM

I'm going to see how the modman works with a twin screw sitting on top of it. The runners are short fat and have nice radiused (almost bellmouthed) entries right out of the box.

For a max effort centrifugal application a plenum box on top of the modman might be pretty nice. Stree manners would be pretty terrible I bet though.

Posted By: jyrki

Re: intake manifold design - 08/19/10 12:25 PM

I think that with the hp/cu in most people are taking out of their combos, it's about just the same whatkind of intake there is, as long as there is one.

With a regular intake and a 90 degree elbow you shouldn't have much problem of making 2000 hp out of a big block, which is way more than enough for most.