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| Joined: | 09-17-2007 |
| Location: | San Francisco, California USA |
| Posts: | 221 |
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Ahhh... you have airhorns inside the airbox? How long are they? Or more to the point, how close do they come to the opposite wall?
I used to run this engine just open with no air filter and about 80mm trumpets. I felt like this benefited the mid range and top end the best on this setup. No airbox would fit the 80mm rams, so I looked for other options including building my own.
I realize now the diameter of the horn needs that length of clearance, that is a great point. I knew this earlier but Pipercross told me to at least have 19mm to the wall, which isn't enough.
What I needed was an airbox that would allow the long trumpets and still give it clearance. I considered making some kind of box that would fit at or towards the edge of the rams, so that I could stand off the airbox by the needed length. Otherwise, if you look at the Lotus airboxes, they aren't big enough for the longer rams.
The name of the game in these airbox designs is do you place the trumpet inside of the airbox (so the airbox itself just bolts to the face of the carb) or do you look for other options. I felt like making a airbox big enough to accept a long ram would make the airbox HUGE, so I didn't really go down that route.
I found an Australian company called EFI that makes some nice universal fiberglass boxes that probably would work clearance wise. But it was big and a little dopey to me:
Then I found the Pipercross 600, which is a very low profile design (only about 40mm thick):
The challenge was to get the long rams to work in this setup. I found another Australian company called RHD that had what are called "runner extensions".
I realized with the backing plate on the Pipercross 600 (which they sell in a Talbot Sunbeam Lotus config which fits DCOE and DHLA spacing) could bolt to this and then I could use some 30mm trumpets, for a combined length of around 90mm. This is how it came out:
Problem was this: the airbox edge was still too close to the trumpet. Like you said Tim, if I ditch the rams it will probably be ok, or run what they call "lip rams" that are basically just round lips that bolt to the edge, maybe only 15mm in length). You can see here it was very tight in there:
I might come back to this design based on some of your input eventually, probably using no rams with the setup. The Pipercross 600 is just so thin, I don't know if it will be able to handle the requirements.
Last edited on 09-01-2020 03:17 am by discogodfather