INTAKE MANIFOLD ( Modification / Design / Fabrication )

[A20A1]

There were a few for domestic carbed motors... I'm sure some applies to efi as well.
I just hang out in boarders books and read thru the books there.

There is a book specificly on automitive math but I'm not sure how much of it atually went into tuning... it was probably more for engine tolerances and stuff like that.

Or look for books on Computer IC engine building. usually they show the written form of the formulas that their program performs... and some have software included in the back page as a CD.

[ICEMAN707]

That JG Engine Dynamics manifold looks like they hacked a stock b-series intake manifold in half and welded on a tank-style plenum. I'm sure the same thing can be done to a stock A20A3 manifold. I think the 89 manifold would be the better choice cus it's a 2-piece design instead of having to hack the 87 manifold. Just take the runner half and port and polish it then make a custom plenum yourself and bolt it on. That would be the cheaper and easier way to do it. If I were to spend $500 on a manifold, I'd much rather save up and go ITB's, for non-turbo I mean.

Also, I've been thinking about removing the spacer on the 89 A20A3 manifold to see if that makes a difference...anyone ever tried it?

[rjudgey]

you can still use ITB's with a turbo you just have to get a airbox thats sealed and can handle the pressure from the boost, the ITB's are sealed and air tight so no reason why it shouldn't work, you'd then be in control of the size of the air box and the tubing going to it might work out better like that maybe?

[ICEMAN707]

you can still use ITB's with a turbo you just have to get a airbox thats sealed and can handle the pressure from the boost, the ITB's are sealed and air tight so no reason why it shouldn't work, you'd then be in control of the size of the air box and the tubing going to it might work out better like that maybe?

That's true! Best of both worlds. ITB's are way better.

[smufguy]

ITB's are not good for turbo since they beat the purpose of their true nature. ITBs are used in naturally aspirated cars to ensure each cylinder gets its own dose of clean air rather than being distrubuted by the plenum with one big Throttle plate. THe reason using one TB is it that its cheaper, but it does not even out the air flow across cyls making some burn rich and some lean since NA works off engine vaccum. On a turbo, its force fed as we know and there is no Reason to have a ITB. There are race manifolds that look like the ITBs without the individual Throttle plates. They call them horns or venturies and they are constructed in the way venom does, gradiating towards cyl 1 from cyl4 to speed up air flow towards cyl1 and have air flow somewhat even across the cylinders. unless otherwise we use intake manifolds like the RX7s, there is no assurance that we will have even air flow.

ps: next time you guys wanna reply to this thread, can u guys please stick to the subject? Thanks

[Accordtheory]

None of that makes any sense to me...except the cost rationale. I think individual throttle bodies are b.s., something left over from the days of carburetion. (no plenum to dampen the pulse of intake suction across the venturi= better fueling) I see no reason to use this shit with multiport injection. If you have uneven volumetric efficiency from cylinder to cylinder because of your intake manifold, that doesn't mean you have to go to ITBs to correct this. Change/replace/improve your manifold. (And how the Hell would being under boost change the cyl/cyl efficiency??) If anyone thinks they can convince me otherwise, go for it. To back up my point of view, Endyn didn't use ITBs on their 300whp B20 Vtec, they modified the shit out of a skunk2 casting. Also, if endyn is going to be associated with the AIR manifold, then it automatically gets my approval.

[FyreDaug]

First I should mention my intentions of this project, it will be a carbed charged system, obviously pull through setup with a 500+cfm carb (undecided, this is just a research step)

Not sure on the charger I will use either, but I plan to only run on 6psi. I was thinking of getting a GM charger from a wrecker off of a 3.8L v6(roots), but it looks too big. Either way I will keep looking around for chargers and carbs, but for now I need to research intake manifold design.

First I have 1 request, since cant currently pull the head off my daily driver and I havent bought a wrecked one yet I would like to see a picture of the cylinder head. Showing the intake ports and if possible the exhaust aswell.

Ive been doing quite a bit of research about tuning intake runners, length, diameter and flow and Ive learned enough that I'm ready to do one on my own. Ive got some designs in my head, but I'm not sure how it would work.

But basically all 4 runners will be the exact same length/diameter going straight back to a single "charge tube" 3x the size of a single runner that all 4 runners be connected to. Not sure about the size of that as of now, but its all R&D. I plan to have the runners tuned to 4500rpm.

Problem I'm having though is I dont have a head to work off of for research stuff right now so all I have is you guys. I'm gonna pick up a wrecked accord when I can find one for cheap with an engine, Id rather have a parts car than just an engine. I'm going to do this 1 step at a time, the intake manifold will be made, and then port matched to the head, same with a header to the head.

I can build the manifold for cheap and get it welded good to hold the boost, also the upper dogbone mount will be relocated, and will probably have 2, 1 on either side of the engine.

Anyways, I'm going a little off topic right now but how good are the internals on these a20s will it be good for 4-5psi? I dont know how much milage will be on the donor car but I will probably be using that one for this project, as it would save time and money and ill still be able to drive the car. Plus Im pushing 290k on the factory engine still holding strong and beating non vtec integras :p

I'm thinking if I do everything right the first time, it will be under 700 bucks.

[A20A1]

Would runner length really be as effectice since you're under boost instead of N/A.

well you have the higher c/r to deal with the stock pistons...
As for stock internals I wouldn't say they'd give you more then 7 psi.

I have a head laying around but the ports are all sooty and oily... you may not get the pics you desire.

[A20A1]

Here you go... I wasn't sure if you wanted the port or all 4 so I did both.

Click on the images below to see the full size.
Exhaust is the left image ... intake is on the right.


BTW: There is a thread on SC carbs... not much has been done but I have looked at a system by CAMDEN for the 22R problem is our pully isn't on the same side as the 22R and we cant just rotate the SC or the screws will spin in the opposite direction. I asked if the pully could be removed from one side of the shaft and placed on the other but I got a reply telling me to call someone... I'm not ready to do that, and I'm surpised they didn't just reply let me know what I figured would be common knowledge to them.

[FyreDaug]

Excecllent just what I was looking for. Why do you have a head just lying around? heh. Thanks.

[shepherd79]

Excecllent just what I was looking for. Why do you have a head just lying around? heh. Thanks.

All of us have cylinder heads laying around just in case we need some to work on it.
look here: https://www.3geez.com/showthread.php?t=18800

[A20A1]

If you notice I bought a magazine on blower tuning in the pic, I've had it laying around for some time...

I was reading up on cam selection and they said a mild profile for the intake paired with an agressive exhaust profile is good for supercharged motors.

[FyreDaug]

Yeah, since its forced induction it doesnt need a long duration for the intake.

About the runners, theres 2 theories I have, 1 being short runners will help low end with a charger because it has a shorter path travel and it would have higher velocity.

The second being long runners will be more effective for higher end, since it will use the runner as a "buffer" during higher rpms.

Basically a very short version of it, but I will be keeping it closer to the long size of the runner.

[FyreDaug]

Alright, a friend an I were working on my theory a little more and we came to some better conclusions. When I was in high school I took welding class, with a couple friends too and our teacher told us "If you took my class, your set for life if you need to come back" and he's still teaching there, so we can use his shop.

Anyways, the idea we came up with (whether it will work the way we want or not is part of the R&D) is having header style runners off of a 3" intake charge pipe. Basically from the SC it will have 3" piping that will be split into 4 equal length 1.5"(?) runners, which will then have a widening (and maybe a split, into 2 0.75" pipes for each valve, if it deems to be unpracticle it will just be 1.5" to it, then matching for each valve (which does seem more practicle). There wont be a plenum on the manifold, and the runner will be running down to the firewall, thus giving me space to mount the blower/carb.

On the intake side pre-carb it will be 3" piping, however we came up with another mini-theory now that there is no plenum that near the end (about 80% of the way to the filter) the 3" will split to 2 2.5" and then run for another foot or so and connect to 2 filters. Essentially acting as a plenum in there with the increased space in the intake housing some filtered air ready to be used.

***Is there anything specific to a draw through system I should be worried about? I couldnt find too much information on it, but its basically sticking a carb on the intake side of the charger, and the charger pulling in air/fuel and compressing. Probably 4-5psi boost.

***And also, should I be worried about cooling the intake manifold? I dont want to use the engine coolant running through it. And I dont know how its effectively cooled stock. Since echarged air is warmer I was hoping to get some suggestions from you guys on how to effectively cool it. I wont be running an IC, but I would like to have some sort of setup cooling the charge pipe and the very least. Not sure if this is a good idea or not, but I was planning on putting that exhaust cover stuff (keeps heat out, long day cant think of the word) around all 4 runners, and cooling the charge pipe.

But please, if there is something I'm missing with this setup, please let me know. Maybe I'm missing something with the draw-through setup that I need to know, like if charging air/fuel is gonna reduce the life of the charger etc.

For the parts I'm considering (without doing any proper research yet) is a carb off of a 350 chevy, rebuilt. Not a performance one or anything, just a stock carb off a 350. And the charger off of a 3800 series II engine (pontiac GTP). I dont know if the charger is electronicly controlled in any way, but its obviously belt driven.

I will need a MAP (manifold air pressure) sensor, which will be fitted right before the 3" goes into 4 runners. But what about boost controlling? How would I go about getting a constant 4 psi all throughout the power band?

[phrenology]

Hell the new 05 Mini Cooper S gets 168 Hp out of its 1.6 Litre with a SC. Hmmm if I had 22K I could get me one of those and put the charger in my Accord! LOL. I wonder if BMW would sell us a supercharger from the Mini? So much for carbs though. I've always wanted to work on doing a small draw through SC with my DCOEs, but I'm having enough shit to deal with just getting the motor back together. Hah.

[A20A1]

The link isn't working for me when I visit the J&S site... so I found some other stuff written on them
http://www.mustangworks.com/articles...ckControl.html
http://www.hotrod.com/techarticles/45840/

[A20A1]

I wonder if BMW would sell us a supercharger from the Mini? So much for carbs though. I've always wanted to work on doing a small draw through SC with my DCOEs, but I'm having enough shit to deal with just getting the motor back together. Hah.

Not all SC will work with carbs though... some could cause the fuel to ignite in impellers/screws.

[phrenology]

Not all SC will work with carbs though... some could cause the fuel to ignite in impellers/screws.

I realize that..that's why I said "So much for carbs..."

Fantasy: A fully stocked machine shop, a dyno and a small research and development crew and I'd be churning out parts for an Accord ready SC.

Reality: I'm broke as shit, and my A20A3 is still in pieces and the amount of headaches involved in this NA rebuild multiplies daily as it is.

[A20A1]

Here is the stock manifold cut... you could add a plenum to that instead of 4 into one... but then the runner lenghts are long and the runners taper wider near the ports instead of smaller.

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[FyreDaug]

Thanks for the replies. What about the PCV? Can that be disregarded entirely or do I need it? (not emission controlled area)

Im going to steal the scanner from my moms place since she doesnt have a computer anymore and scan my diagrams. I want all the input I can get before building stuff.

I do live in a climate that gets to -40 in the winter, and the manifold will be made out of cheap shop class metal. (well not cheap, but not aluminum though)

[A20A1]

be careful what metal you use, you don't want your manifold rusting... and coating the inside of the manifold to prevent rust... well I dunno if the paint would work well with fuel... it may begin to errode and then expose the metal again.

You do need PCV, and the brake booster... and some way to provide proper vacuum to those... add check valves so they don't see pressure if you connect them to the manifold but there is no gaurantee that you'll ever get a good high vacuum signal from the manifold... even with the car at idle.

I read that some carburetors that are not setup to run with superchargers tap into manifold vacuum thru ports in the carb base... this causes problems because there is a fake vacuum signal created by the suction of the blower... and since there is extra vacuum the powervalve closes and leans the fuel mix.

They may be trying to sell demon carbs but they said that there is a demon that uses boost referenced powervalve.

[FyreDaug]

be careful what metal you use, you don't want your manifold rusting... and coating the inside of the manifold to prevent rust... well I dunno if the paint would work well with fuel... it may begin to errode and then expose the metal again.

You do need PCV, and the brake booster... and some way to provide proper vacuum to those... add check valves so they don't see pressure if you connect them to the manifold but there is no gaurantee that you'll ever get a good high vacuum signal from the manifold... even with the car at idle.

I read that some carburetors that are not setup to run with superchargers tap into manifold vacuum thru ports in the carb base... this causes problems because there is a fake vacuum signal created by the suction of the blower... and since there is extra vacuum the powervalve closes and leans the fuel mix.

They may be trying to sell demon carbs but they said that there is a demon that uses boost referenced powervalve.

How would I run a PCV system? I've still got a new valve, but I'm just not sure how to set it up. I figured I could live without it.

As for vacuum, I know I'm going to have problems getting negative pressure under boost. But what about pre-carb, there is a small line tapped into the already 3" opening that runs to the carb aswell. And by small I'm thinking, large vacuum line size, and then connecting all vacuum accessories pre-carb through a check valve? (I'll add this to my diagram when I get the scanner and explain what I mean)

What are the chances a typical charger wont work with air/fuel? I dont want to be blowing myself up, but I also want to be getting a charger from a wrecker.

I dont understand why a carb wont work with a charger when its being pulled through for a couple reasons, mainly it doesnt have to make the carb work as hard, it will just be creating a different pressure (still negative) than that used in the intake stroke to pull the mixture through, so why would it lean it out? Wouldnt it just take the mixture faster?

As for manifold rusting, I'll leave that for later. I'll get it working and then pull it off ~1000km later and check it out, if it needs some coating, that can be done, but I'm not too worried about it right now.

What kind of charger should I be looking at? Would a roots be acceptable? From what I know off hand without doing anymore research is that a roots charger can pretty much give me full boost down low (which is what I am wanting) but it heats up alot, thus the previous question about cooling the manifold. I'd rather not push hot air into the engine if I can cool it. And twin screws being very efficient (but where would I find one from a wrecker?? Good luck finding one) and a centrifugal is iffy to me.

I think roots would be the best way to do it and

An intercooler will most likely be necessary at boost levels above 6psi with a roots supercharger.

and since I'm not boosting that much, if I can cool the intake I should be fine. Like a secondary rad idea, with an aux water pump to run all over the intake manifold. And a roots would be the one I would typically find in a wrecker. (and is the one on the GTP's)

[FyreDaug]

And I just had a wild idea of expanding the charge pipe width a little bit (maybe to 4") and running 2 parallel lines of coolant through there, that way when the charge passes around it, it will hit some chilled pipes. Probably not effective, but it was something that just came to me right now. I'm thinking maybe just tap into the engine coolant line like what is normally done on the manifold would help cool a roots charge, but I would love the idea of having secondary rad to cool it seperately this way.

Any comments on this?

EDIT: By the way, the charger I am looking at is the Eaton M90. Comes on thunderbirds, GTP's etc. Typical roots setup capable of 9psi I believe.

[A20A1]

I dunno About the Eaton, I've only seen them on newer 1990 and up model EFI cars and it doesn't look like a top feed like most carbed blowers I've seen on domestics... I remember you saying something about 6cyl though... for me I'd look for something with a carb on it already, that to me would at least get rid of the doubt... you could always e-mail eaton
...
What about digging around for a Weiand 142 cid blower
or a Camden?

[A20A1]

I dont understand why a carb wont work with a charger when its being pulled through for a couple reasons, mainly it doesnt have to make the carb work as hard, it will just be creating a different pressure (still negative) than that used in the intake stroke to pull the mixture through, so why would it lean it out? Wouldnt it just take the mixture faster?

I didn't say it wouldn't work... you will just get LEAN spots when the extra vacuum created by the blower CLOSES the POWER VALVE. Blower vacuum is not the same as manifold vacuum and is usually much higher..

True that other parts of the carb work better... but remember most of the carb doesn't run off ENGINE / MANIFOLD VACUUM it runs off of VENTURI VACUUM... the VENTURI VACUUM is created at the VENTURIES.

On a supercharged motor vacuum below the carb is giving the parts that operate off of ENGINE VACUUM false vacuum readings.

Vacuum below the carb 24"
Actual engine vacuum 14"

As you open the throttle vacuum is supposed to drop to allow the power valve to open... however...

Vacuum below the carb is 12"
Actual engine vacuum is 2"

Under actual engine vacuum the power valve should be open all or most of the way @ 2"
but because of the blower you get 12" so the valve doesn't open all the way or not at all and your mixture ends up being lean.

The POWER VALVE needs to be OPEN in order to RICHEN the fuel mixture...

I hope that clears things up. the "CAPS" are just to highlight terms