Rep Power: 313

I've been reading a lot of info about intake manifolds on the net lately. The reason I wrote this thread is because I am thinking of attempting to fabricate (or have a shop do it) a custom intake manifold later sometime. I'm sure everyone remembers the KMS manifold? Well, his runners were way too short to utilize any low to mid range power. KMS' deisgn seems to be more geared toward turbo applications where the air is actually induced into the head vs drawn such as in NA applications.

Intake manifold design involves using port tuning to achieve the proper airflow through the runners to the engine. This is why its best to have the head PnPed before installing a new intake manifold, so that the manifold can be flow matched to the head. I wonder how many porters out there (including DH) actually put their heads on a flowbench after they clean them up? I mean, for the cost involved I sure would want it done just to get a rough idea of how much of an increase of air is making it into the engine.

If you look at the engine bay of the 2001+ civics vs the previous generation cars, the engine bay seems to be more cramped. The area where the intake manifold rests is no exception. If you take a look at the previous gen manifold designs, they utilized a side flow design where the throttle body was mounted on the side of the manifold. The runners were fairly long, which is needed to maintain proper air velocity through them. Looking at the newer civics, with the cramped engine bays, utilizing the same style manifold cannot be accomplished due to space limitations. Honda's newer design still utilizes long runners as before, but they are wrapped around the air plenum from the rear side.

If you take a look at the design of the KMS manifold (as well as DH's from their photos), they attempt to utilize the standard straight runners from the air plenum to the head. This would be fine if the runner length could be made longer, but again, due to space limitations this cannot happen. My thoughts are that an intake manifold modeled after the stock manifold (with runners wrapped around the rear of the air plenum) would work better than just plain straight runners, due to the fact that the runner length can be maintained. At the same fime flow can be increased to match that with the new higher flowing head. This would give the benefits of increasing both torque and HP in mid-range RPMs as well as helping decrease HP rolloff on the higher end RPM band.

So.....with that in mind, when I actually have some money and time I might try and see about attempting this....Anyone else have any thoughts about this?

 
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I know someone that who is making a custom made intake manifold and throttle body for his B16 Turbo engine. He said that if I had a custom made intake manifold it will be have to be for a turbo application because there is no room for long straight runners. If you want NA setup then you will have to calculate air velocity + runner size to maximize volumetric efficiency.

To maximize the potential of our engines and b*tch slap all those V8 and those people that think that because they have an expensive sports cars that they won the road. And people that hate civics. You will have to start from the bottom and up. Head work NA setup will only give out 30-50hp it is better of just slapping on a RSX vtec engine. Too much work and money trying to go NA. Turbo and Nos will give the best gains for the money. Turbo + Intercooler running on 8psi will put out 180hp EST. NOS 50 shot will give an additional 50 + 180 = 230hp EST. This setup will run you around $3,000 to $4,000 cheaper trying to get out 230hp on a NA setup. At the end if you did it right and did not blow up your engine you can take it all off and sell the car. I just don’t want to put all that money and work on a car that will not spank V8 and people that think that having an intake and exhaust makes there car sports cars. And ya people that think that just because my car is a civic that I’m all show no go.

 
Rep Power: 313

The reason I am thinking of doing this is because of potential that the D17 has. I (as well as many others) don't want to just slap a K20 in and call it a day. I personally have fun working on my car, and would like to see companies actually come up with products for it. Rather than wait for them, I figure I'd go about it in my own way.....

And whose to say that starting with a ported / polished head up top vs doing the bottom end is the right path to go? Remember, the engine needs more air before you can achieve more HP - without it you can beef up the bottom end all day long and you'll still be making the same as you were before.

Also, you have to remember that everything works together - the intake manifold works with the ported head, the ported head works with the properly ported exhaust manifold - all to give the most gains possible (NA) when all's said and done. FI is of course a different matter (as you so have stated). However, you have to remember that for FI your car still runs NA until the turbo spools up - which may not happen until the middle of your RPM band, so your low end needs tweeking as well. With the proper sized components (ie the intake manifold, which we are talking about here), you can tune the engine to maximize its potential.

So yeah - I've got an idea of what I want to do, time and money are the only things needed from this point out....

 
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Money, time and hard work will get you where you want to be. I just hate the way Honda made civics so hard to mod. I am all for NA setup, NA cars are more impressive than any FI car. To tell you the truth the reason I wanted a civic in the first place what to make a NA car. But I was so disappointed when I started my research that our civics are not mod friendly. I use to own a 96 AWD Turbo Eclipse but I wanted to make a NA setup. Vortec makes a blower that is like a turbo but it uses a belt setup.

 
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opto, whats wrong with the stock manifold? I personally think it provides better torque numbers, at low rpm than previous D16/15 manifolds, if you were to go with something after market, i think you would gain maybe 4-5 hp(high rpm), but i think low end torque would suffer
drastically.


I would alter the throttle body before trying to mess with the IM. Thats just me though

 
Rep Power: 313

That's my point, Honda designed the stock manifold that way for a reason. So far the only two companies that have tried to make manifolds for the D17 are DH and KMS - both have tried to go the old route and use the side feed throttle body design. Unless you have long enough runners its not going to provide enough midrange torque.....

The stock intake manifold is great for the stock engine. Once you start to modify the volumetric effeciency of it (ie how much air will flow in / out) than you need a better manifold - which is why I wrote this thread....its just another piece of the puzzle...

 
Rep Power: 324

how about taking the "design" from a k20 engine and using it. thier runners slope downward to get the length they need. you could almost duplicate it and adjust to fit the d17. It flows enough for a 2.0 with a high rpm range why not a nicely modded d17. the only problem is that they are cast, and that takes alot of cash to do.

 
Rep Power: 313

I just measured the runner length of our stock manifold.....they are about 14 inches in length. The actual intake plenum is SMALL! Compared to the KMS manifold (and the DH one in the photo), their plenums are huge, and runners are much shorter in comparison.....

So we have a start....