Speaking of intake manifolds
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From: Baltimore
Speaking of intake manifolds
i remember talking with prolene and few others about our stock intake manifold, and it seems everyone agrees there are room for improvement. UL had mentioned one-off designs, but i'm interested in mass producing (~100 pcs? can we say group buy?) his one of designs. looking at other brands and designs, i see aftermarket intake manifolds start from ~$350 to over $1k (yikes!), so i was wondering what kind of engineering may be needed to improve upon the stock intake manifold vs. fabricating a new one? UL, bud?
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From: You wish
Composites are sometimes better for small production runs. They aren't really any harder to fabricate than sheet metal, and sometimes its easier to get curved surfaces with CF layups vs. sheetmetal shaping.
There are several things to consider in looking at the F20C manifold.
1. Flow, obviously. This may surprise you, but I don't think flow is the primary issue here, at least not with stock internals. From what I can see looking through the throttle body opening, the inside is shaped about like you'd expect (quasi-velocity stacks on each runner, runner opening properly elevated above plenum walls, etc.). However, since intake manifolds are cheap, I plan to have my favorite porter mess with one of those too when we start on the head R&D project (flow bench should be in next week, I'll start soliciting for funds, although we now have a sponsor for half the cost!). If there are flow gains to be found iwth simple tweaks, we'll know. We'll also know if the manifold is a restriction.
2. Plenum volume. Honda engineers admitted in their SAE paper that they went with a smaller plenum volume than originally anticipated, ostensibly to improve throttle response. I'm no expert, but think about it this way. When you snap open the throttle, the first thing you have to do is fill the plenum. Until that happens, you can't get maximum flow through the runners. Hence, a smaller plenum volume helps response. However, the idea of an intake plenum is to give each cylinder access to a large, high pressure and stable airmass. Each intake event takes a gulp out of that volume. If the size of the gulp is too large relative to the plenum volume, you can get large pressure variations in the plenum, which you really don't want. Historically, the larger the plenum, the better the power, particularly at high rpm.
3. Runner length. Thing of Helmholtz resonance here. Length of the runner (which inlcludes the port length to the valve) determines the primary frequency as well as the harmonics. Shorter runner equals higher frequency. I'm not ready to speculate about runner length on the F20C yet. If the power curve wasn't rolled off so artificially up top, I'd be a little more certain, but it may be that the runners certainly don't need to be any shorter at the rev range we're working in. A bit longer might even be beneficial if the stock limiter is retained and good tuning available.
Overall, proper manifold design requires some trial and error. Once we buy a spare, I may have some CFD simulations done to determine the effects (assuming a certain port length added on). I think the biggest area for gain is probably in the plenum volume area. An increase of 500-700 cc might make a nice difference in power.
UL
There are several things to consider in looking at the F20C manifold.
1. Flow, obviously. This may surprise you, but I don't think flow is the primary issue here, at least not with stock internals. From what I can see looking through the throttle body opening, the inside is shaped about like you'd expect (quasi-velocity stacks on each runner, runner opening properly elevated above plenum walls, etc.). However, since intake manifolds are cheap, I plan to have my favorite porter mess with one of those too when we start on the head R&D project (flow bench should be in next week, I'll start soliciting for funds, although we now have a sponsor for half the cost!). If there are flow gains to be found iwth simple tweaks, we'll know. We'll also know if the manifold is a restriction.
2. Plenum volume. Honda engineers admitted in their SAE paper that they went with a smaller plenum volume than originally anticipated, ostensibly to improve throttle response. I'm no expert, but think about it this way. When you snap open the throttle, the first thing you have to do is fill the plenum. Until that happens, you can't get maximum flow through the runners. Hence, a smaller plenum volume helps response. However, the idea of an intake plenum is to give each cylinder access to a large, high pressure and stable airmass. Each intake event takes a gulp out of that volume. If the size of the gulp is too large relative to the plenum volume, you can get large pressure variations in the plenum, which you really don't want. Historically, the larger the plenum, the better the power, particularly at high rpm.
3. Runner length. Thing of Helmholtz resonance here. Length of the runner (which inlcludes the port length to the valve) determines the primary frequency as well as the harmonics. Shorter runner equals higher frequency. I'm not ready to speculate about runner length on the F20C yet. If the power curve wasn't rolled off so artificially up top, I'd be a little more certain, but it may be that the runners certainly don't need to be any shorter at the rev range we're working in. A bit longer might even be beneficial if the stock limiter is retained and good tuning available.
Overall, proper manifold design requires some trial and error. Once we buy a spare, I may have some CFD simulations done to determine the effects (assuming a certain port length added on). I think the biggest area for gain is probably in the plenum volume area. An increase of 500-700 cc might make a nice difference in power.
UL
Joined: Mar 2001
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After doing the temp recordings, I would like to see a way of 'cooling' the intake manifold. I think Honda's done a pretty good job with it in terms of flow and such to get the output they do out of this little engine. I know there are insulating kits you can buy to help this situation but I'd rather see a different approach. Perhaps if a new intake were to be invented anyway, you could incorporate a material that would not conduct the heat very well, both from the head and by way of engine bay heat. I wonder if that's why Chevy uses plastics for some of their intakes. Would double walled plastic be better? How about ceramic? Probably way too expensive. I don't know.
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From: Fort Worth
I think it's interesting everyone thinks there's so much room for improvement- I don't doubt it's possible, but I'd like to see someone prove it. Compare our manifold to, say, an Integra Type R or a Euro Accord Type R and I think you'll find this to be one of the shortest, fattest, and straightest manifolds Honda has ever made.
I know from experience UL is very right- testing, testing, testing...
I know from experience UL is very right- testing, testing, testing...
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From: You wish
That's why I don't believe there is much to be done in runner design. But, if you look at our plenum volume, we're running less than the B16A, about as much as a D16A! I believe that has to have a negative impact on power. Perhaps it has been made up elsewhere (I'm thinking its taht unusually large airbox), but I'd like to see.
UL
UL
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From: Houston
[QUOTE]Originally posted by marcucci
[B]I think it's interesting everyone thinks there's so much room for improvement- I don't doubt it's possible, but I'd like to see someone prove it. Compare our manifold to, say, an Integra Type R or a Euro Accord Type R and I think you'll find this to be one of the shortest, fattest, and straightest manifolds Honda has ever made.
[B]I think it's interesting everyone thinks there's so much room for improvement- I don't doubt it's possible, but I'd like to see someone prove it. Compare our manifold to, say, an Integra Type R or a Euro Accord Type R and I think you'll find this to be one of the shortest, fattest, and straightest manifolds Honda has ever made.
