Individual Runner ?'s

[Doubt_Incarnate]

i did, at one time, use styrofoam, to make some patterns for plates to complete the heads (that last bit under the valvecovers), so i could make an intake to bolt to that. i'll try to find them, if they are still intact. it wouldnt take anything but sheet metal to cover the valley. this idea is still in the back of my head, but there isnt a machineshop around here willing to cut the peices out for me, you say "car" or "motor", and they say "no". i'd have to drop the cash on a good drill press and nice bits. need to find a good sliding vise thing that will let me move the piece around to. if i can find the stuff cheap enough, i wll. it would be the ideal thing to do. the things in the way right now are paying off my daily driver, and credit card. i have a digital camera, i'll make up some sketches, shoot them and post them.

after work.

[Guest]

Also in that pic, the injectors are firing about 90 degrees from where they should be. its going to be a tuning nightmare and wont reach its peak performance potential.

I've been pondering this statement for a few days now and am having a hard time figuring out why tuning will be any different or why the potential will not be realized due to where those injectors are pointing.

Take a look around at some built engines, you'll see why I'm confused, a lot of home made intakes use injector angles similar to the ones pictured, there seems to be a lot you are not considering here, where injector angle is a very low factor, very low.

To the original poster, I will suggest not using carbs as the TBs, use small TBs from anoth EFI donor if need be. The carbs will be much larger and more difficult to fit than dedicated TBs. Maybe look at using TBs from a 2.)L OHC turbo engine that came in the late '80s/early '90s Grand Ams ('87 to '89 IIRC) and Sunbirds ('87 to '90), Skyhawk '87 to '89) I'm thinking there was at least one other model, but it's not coming to me. IIRC these TBs were 42mm in size. There was a later 2.0L OHC that was MPIF N/A, that used a slightly larger TB, but may be too large for an ITB set-up, IIRC they were increased to 45mm. These TBs also have vaccum ports on them along with IACs that will need to be blocked to adapt a proper IAC set-up to this intake design. I'm sure there are other vehicles out there will have donor TBs, I'm sure there will be some import that would have perfectly side TBs Honda D16 maybe?

Anyway, also check out Kinsler fuel injection. http://www.kinsler.com/
They sell ITB components and have very good technical papers (I think you still need to buy them though).

Good luck and keep us posted on your progress... I'm just about to start a sheet metal EFI intake for a 409, for a friend of mine, this aught to be intersting.

[Anonymous]

the injectors firing at that angle is a good thing, so long as the rpms are up. when rpm is kept high and at high throttle percentage, air flows through the fuel, this in turn gives you a very good mixture, and prevents fuel from "sticking and pooling to the runner walls." And batch fire is also not as much of a bad thing as kinsler says. In fact, at high rpm, most SFI systems turn over to batch fire. And since these manifolds traditionally are not made for low rpm performance, batch fire and cross mounted injectors can be good.

[Guest]

the injectors firing at that angle is a good thing, so long as the rpms are up. when rpm is kept high and at high throttle percentage, air flows through the fuel, this in turn gives you a very good mixture, and prevents fuel from "sticking and pooling to the runner walls." And batch fire is also not as much of a bad thing as kinsler says. In fact, at high rpm, most SFI systems turn over to batch fire. And since these manifolds traditionally are not made for low rpm performance, batch fire and cross mounted injectors can be good.

That's where I was going with that...

Anyway, SFI is good for controlling large injectors at low RPM, no other real benifit, well economy could be enhanced slightly, but IO don't feel it's as drastic as some people are lead to believe.

[Anonymous]

Probably not.

Weren't the later years of the dohc SFI? Like the 95 on or something. Well the earlier versions still made just about the same amount of power, down 5-15, but no big deal.

[Doubt_Incarnate]

ive seen the kinsler stuff, but im a budget, and its not within my range, wish i could get that stuff though. igot 7 carbs for under 100$, 3 that i wouldnt use as carbs, and 4 good ones. i figured the smaller size would be better for lowend, and prevent hesitation, if there would be any.

i have an 88 integra siting in storage, i thinks its tb is 56mm, so its more of an upgrade for the stock manifold, a little overkill for IR.

[Anonymous]

Well if you are going to be making your own lower intake, it is best to mount the injectors far away from the head/intake valve. The best place is directly after the throttle plate with an ITB setup.

IMO, the best is yoru lower right drawing, just move the injectors up the runner some. This setup will also make throttle linkage easiest.

[Doubt_Incarnate]

i like that one, it has the smoothest flow routes. but now that i think about it, there isnt a hole lot of space around the rear valvecover, so sending anything towards the back in my car would hit the fire wall or come soo close to it i wouldnt be happy. i lik the looks of the leftmost one. it has potential for the "six pack" setup, looks like it would actually be the easiest too. like the throttle would be simpler, and all the vacuum ports would be right there.
if i do that i guess i have to fiberglass a scoop to stick all 6 throttles under, with shinny chrome stacks/horns. just more work. not as sleek looking either, but its a square car, how slick can it look?

i've seen i think the kinsler stuff has the injector right behind the throttle plates, i think i guess that good for short 2-6" runners. i figure thats too far for the mix to go in a setup like i want, so i was going to keep the injectors a "stock" distance from the valves, if possible.

[Anonymous]

The following is a direct quote from TWM Induction, a popular supplier of ITB manifolds and such. I suggest you do some reading on their site, www.twminduction.com

Why don't TWM throttle bodies have venturis like carburetors?

Carburetors rely on the pressure differential created by a venturi to draw fuel from the float bowl via the various jets and circuits. By their very nature these components cause a restriction to air flow, and contribute to pumping losses. The inevitable disadvantage of this system is that, while a venturi of a certain size may be necessary to provide low speed driveability it then acts as a restriction at high RPM. Because the fuel in an EFI system is injected under high pressure there is no need for any venturi. That is the reason throttle bodies flow so much more air than a carburetor of the same size (see page 21 for flow data) and the reason that EFI systems can use larger throttles than the equivalent carburetors.

Why are the injectors positioned in the TWM throttle bodies and not in the manifolds, like original equipment EFI systems?

Original equipment EFI systems are configured to meet very stringent emission regulations and to provide "soft" driveability characteristics. Positioning the injector as close to the inlet valve is beneficial in this respect. Maximum power however, is usually obtained by moving the injector away from the inlet valve, some racing engine manufacturers going as far as to mount the injector high in the velocity stack and others installing two injectors, designed to operate at different RPM. When TWM designed the throttle bodies our engineers were not in favor of having high pressure fuel on the atmosphere side of the throttle plate, although this could have resulted in some power increase. We compromised by mounting the injector as far from the cylinder head as possible while still maintaining the safety afforded by keeping the fuel downstream of the butterfly.

As you can see, you may want to rethink your use of carbs and the injector position. But if you remove the venturi, you should be fine, assuming also you can get all 6 carbs to sit close enough to each other, that way you do not have to spread them apart, which would mean unequal runner lengths.

[bszopi]

Those look somewhat like some of the ideas I had in mind. But as I found out, the ports don't line up as ideally as you'd first think...

[oil pan 4]

Check out my intake harmonics chart, it is a must if you
are going to build an intake.

[Doubt_Incarnate]

i did notice the almost-evenly-spaced part of everything not lining up as nice as i'd like, one reason to fab up a custom manifold. i checked out the twm page, but i couldnt find "page 21", i was interested to see the flow rates of the carbs vs. tbs. if the carbs help in the low end i'l stick with them, ive driven some cars that feel like they cant get out of their own untill 5K(honda) i want it to be a good driving car on the street, not a big hesitator, i dont want to have to be in the 4K range to feel like its moving, thats one reason to keep a stock injector location, and for the longer runners, i can sacrafice some top end for the low end. i figiure i can get it together with what i have, and upgrade later, if i can put this together, changing things over shouldn't be a problem. i looked that harmonics thing to. i dont quite understand, elaborate. this isnt going to be a high rpm motor, just 6K. i read maximum boost, and it stakes there is a big difference in stress for even a 1K rpm increase.

[speedvisioncavalier]

i know its a different idea, but i would suggest if you are going to be fabbing up a new intake manifold, and probably raising the hood up a bit, then why not mount a blower up there? an M62 should do the trick. you will make alot more power, at all rpms with the blower, even at a low 4-5 psi. if you make it out of sheetmetal, it shouldnt be too tough. also, you can keep your stock TB, which would be in roughly the same place as the 3x00 intake manifolds, and you dont have to worry about the IAC not working because you still have a single TB.

take this manifold as an idea. you make the intake for a V6 (of course), and not quite as tall. then instead enclosing the top of the plenum as if a carb would be mounted, you could instead make a plate to mount that M62. it would take some effort to mount up the fuel injectors and fuel rails, but it should be able to be accomplished.

[Anonymous]

Here is a really simple run down of intake manifold harmonics. When the valve closes and the piston moves up, it causes an air pulse to travel back out your intake, the opposite direction of intake flow. The pulse or wave then 'bounces' off a point in the intake, and reflects back down the intake ports. You can time your intakes so that your valve will be open when the pulse reaches it by adjusting runner length. This will give you a mock forced induction result, just not nearly as powerful. This is totally negligible in ITB setups, as there is nothing for the pules to resonate on before the throttle plate, there is no common manifold area. This is also negligible in forced induction applications.

As for injector placement, closer to the valve doesn't mean better low end, worse high end. It just basically allows the engine to run more smooth and efficient, but it makes noticably less power than with the injector spaced far away. For your application, I would leave it in the stock or near stock location, it sounds as if everyday driving is important for you. With the setup on the above DOHC, it looks to be all high end.

The ports on the dohc are also not evenly spaced, if you cross them they will run into each other, like that pic of the pushrod 660.

Here is a pic, also from the TWM induction. Note that this is carburation vs EFI, but notice the high end gains of the EFI over the carbs. This probably has a lot to do with the venturi, the air interuption yields good low end power. Obviously FI is better, but it shows the carbs making better on the low side. But, assuming they adjusted their runner lengths properly, they could make that same engine make more hp and tq than the carbed version, but it sure wouldn't be maxxing at 8200rpm.

I couldn't find that page either, their site is very tough to get around I have noticed.

What it comes down to is that ITB are the best setup around. There will never be a manifold that can outperform an ITB, on the lowend, midrange, or high side, assuming the ITB's critical dimensions are tuned properly. Once tuned, they can be made to perform to 3,000rpm or 30,000. So they are a bit more selective than manifolds, you aim for a 3,000rpm curve, and shoot for it. For you it is 3-6, for that dohc it is probably 4-7 or even 5-8. So basically many people will argue that ITB setups are for all high end, but this is completely false. Adjusted properly like your's will be, and you will be amazed.

All of your above setups allow for adjustment, and this is good. If you can get a dyno hook up, you can adjust runner length on the dyno, and watch at how it moves your power curve left, right, up, and down. One mroe thing I suggest is using tapered pipe. On sections where you have straight piping, like your far right pic, I'd advise using osme sort of tapered piece, that starts at a large diameter, and very gradually tapers down. This increases intake velocity with profound effects, it gives the same type of result as people using hourglass-like pieces in their exahust, just much more of an effect. Most manifolds nowadays taper, and all custom ones either do, or should. So if possible, with straight sections, add tapers.

[Guest]

Brad I now see the direction yuo were/are going with that intake, I like it.

*runs off to start on new upper manifold*