www.dodo-upgrades.nl

i think i get the jist of what your saying, yes porting your manifold could be good but its proabably best to just buy an aftermarket one. Porting and polishing the head is a must if your N/A though, so yeah.

If there are too many differences in diameter the air will loose velocity. When a fluid (gases are counted as a fluid from an engineering perspective) contacts a surface it will slow down. With the fluid in contact with the wall actually stopping for a short time this causes friction against the fluid "layer" next to it which will cause it to slow down aswell (you have to imagine the fluid flow through a pipe as loads of layers of fluid).

This is a normal striaght intake tube
The lenght of the lines is the airs relative speed compared to each other.
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This is one with smaller diameter

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As you can expect the air slows down at the junction but it also slows down all the air next to it, and that slows down the layer next to it etc. So yes you gain velocity for the uniterupted air in the middle but the air towards the edges gets slowed down dramatically. You might actually get less air flow so thats why i think you should match you inlet tubing to your manifold diameter, or try to make changes gradual so you dont get lots of interference. (this picture was done freehand, its not meant ot be accurate!!)

Good explanation. Thank you very much.

i have a custom CAI with DNA marine, filter

Can anyone tell me where to get a performance panel filter for a stock D14A3 IM/airbox?

From ebay or at local car tuning shop.
If you order from Usa you will ask for D16Y7 engine one.

BETEK wrote:From ebay or at local car tuning shop.
If you order from Usa you will ask for D16Y7 engine one.

Why D16Y7 if I have the stock IM/airbox on my D14A3? Searched the internet a bit and only found this http://global.ebay.com/33-2047_KN_KN_Ai ... 76094/item - Civic from 97-01/1.4 but on the picture it just doesn't look right and tbh I was kinda hopping to get it a bit cheaper

The d14a3 and d16y7 have the same air filter and intake manifold

Tis true they have the same crappy IM as our D14's

Dunno but I quite like the IM of the standard D14 - hope you won't ban me for this statement but it has long/narrow runners with no plenum and that means that air gets really quickly into the engine at low revs/speeds. That's why it's so driveable for a 1.4 cause it has some punch deep down and at mid-revs but I totally agree that it's a crap design for high-revs cause the stock engine really losses power rapidly after 5500-5800rpm. Without a different cam or the mini-me swap I'm not prepared to lose this so I decided to leave the stock IM on my D14. I'm just gonna make a better/smoother intake.

Did a 80-120/kmh run with my stock D14A3 (75hp) - 9.2sec so there is much room for improvement. First I'm gonna get the 1.4IS 90hp TB gasket, panel filter, remove the resonator box and maybe do some work on the TB/airbox while I'm at it

Is this the right filter - http://global.ebay.com/KN_Air_Filter_96 ... 94704/item

Or is it this one - http://cgi.ebay.co.uk/33-2047-K-N-Filte ... 35a73999f3

If you do the OBD1 swap then you will gain a lot of torque back and gain a lot of high end power due to true MPFI making the engine a lot more efficient, rather than the (rubbish) stock D14 setup 2 sets of injectors lumped together