L20b performance down draft intake manifold??

[Lozer]

where can i find one of these and what kinds are avalable.

 

i currently have a stock l20b intake with a 32/36 webber.

[datsunfish]

You can occasionally find offenhauser dual plane and edelbrock intakes on ebay. I cant tell the difference from my edelbrock to my ported l16 intake. Runs about the same but thats on an L16. Might improve things on a L20b but dont expect any miracles.

[banzai510(hainz)]

the stock L20b intake might be bigger than the Offenhauser.

 

I seen the dual plane ones and notice the small ports. More for low end torq i think. But dont quote me.

 

were the Wber DGV fit on the carb adapter you might want to open the throat so there is not sharp corners. so the air flows nice and smooth.

 

But if your car truck is running fine I wouldnt fuck with it!!!!!!!

Edited December 22, 2008 by banzai510(hainz)

[Phlebmaster]

I have used all three....L16 stock, L20 stock, L16 ported, and an Offy Dual Port which I am running now.

 

I noticed an improvement when I ported and hogged out my L16 stock mani, very throaty sound and ran great.

 

The Offy I am running now does have smaller ports...but they were specifically designed that way to speed up the air flow into the cylinder according to the Offy web site. (Air Ram Effect) I did notice a lower speed improvement, but a more restricted intake changes the sound a little. My cam does not sound a mean as it did with the ported L16 mani.

 

In my opinion...stick with a stock L16 mani but port it out and get a high rise adapter for your Weber.....and call it good. :lol:

[banzai510(hainz)]

the stock L20 manifold should have bigger ports but has the EGR sideplate things ect......PCV

[datzenmike]

The stock intake has BIG runners. Small runners force the intake air to speed up and pack it into the cylinder just like sucking the last of a coke through a straw.. it comes out of the straw very fast and to the back of your mouth, with force. The problem is that at high RPMs the engine has to suck too hard and power drops off so a bigger intake port is needed for extra flow. The Dual plane manifold is an attempt to give added high speed at low RPMs.

[Phlebmaster]

The stock intake has BIG runners. Small runners force the intake air to speed up and pack it into the cylinder just like sucking the last of a coke through a straw.. it comes out of the straw very fast and to the back of your mouth, with force. The problem is that at high RPMs the engine has to suck too hard and power drops off so a bigger intake port is needed for extra flow. The Dual plane manifold is an attempt to give added high speed at low RPMs.

 

Yes...this is exactly what I have noticed. It is a toss up between the ported L16 mani and the Offy. I like the sound of the L16 but the low RPM performance of the Offy.

 

Choices....choices :D

[datzenmike]

What we need is an intake that morphs into a larger size as the revs go up. Somewhat like VVT for the cam.

Edited December 22, 2008 by datzenmike

[Phlebmaster]

What we need is an intake that morphs into a larger size as the revs go up. Somewhat lik VVT for the cam.

 

Yeah...something like a shutter of a camera. :D That would be cool! Then it could be mechanically activated by the throttle.

[datzenmike]

Check these E and DE intakes. The little butterflies semi block intake flow at low speeds and high vacuum and open as the vacuum lowers. The small restriction is "to aid turbulence around the injector at low speed to improve mixing and engine efficiency"

 

http://i138.photobucket.com/albums/q251/datzenmike/motorKA24DEg.jpg[/img]"]

 

KA24E intake butterflies open: note that even full open there is a slight up tilt toward the injector.

http://i138.photobucket.com/albums/q251/datzenmike/720EFIstuff001Large.jpg[/img]"]

 

KA24E butterflies closed. Note notch in top.

http://i138.photobucket.com/albums/q251/datzenmike/720EFIstuff002Large.jpg[/img]"]

[Guest jaimesix]

The Canon downdraught intake manifold works with 38DGES and 32/26 DGEV.

[racerx]

Yep..heard that its not worth getting an offy intake, unless you buy one cheap. Even then what is the gain 1-2 hp, maybe none?

[Llittle_Llama]

the focus SVT has an intake that swaps from short to long runner, it has been done, but takes a lot of room....

[RacnJsn95]

What we need is an intake that morphs into a larger size as the revs go up. Somewhat like VVT for the cam.

 

I was thinking along the same lines myself... I was thinking a variable length intake, where the runners reacted to the engine vacuum, moving in and out as needed through out the rpm range. The old theory says longer runners make more low end torque, and shorter makes more top end zing!

 

Though about getting 2 different pipe sizes, one that fits inside the other, and machine 2-3 oring grooves into one of them to seal. You'd most likely have to have some sort of dust boot to keep dirt, etc out... It could possibly work, but I think it would only have a practical use on an EFI motor, don't think it would be that great for a carb.