Air filter position

[jimj]

Today I went with a pal to Aston Engineering in his Zagato bodied DB4. I call her Cheryl Cole; "not all of it is real but it looks good enough for me". In passing Dave Jacks remarked that the air filter was mounted on the end of an airbox, not dissimilar to a Lotus Twincam, behind the radiator. "That needs moving ahead of the radiator as it`s sucking in hot air" he said. My pal asked if it makes much difference. He said that they`ve found a big difference on the dyno, as much as 20 to 30bhp. That`s more than10%. We were amazed but he assured us that, consistently, that`s what they`ve found.
Jim

[CBUEB1771]

the air filter was mounted on the end of an airbox, not dissimilar to a Lotus Twincam, behind the radiator.

The engine air filter on standard Elans and +2s is forward of the radiator, or am I missing something?

[jimj]

Pardon my bad grammar, I meant that the air box, though obviously longer for the triple Webers, is similar to that on the Lotus Twincam which, correctly, trunks cool air from ahead of the radiator. In this case, incorrectly, there was a cone filter behind the radiator on the end of the airbox.
My point being that some (Lotus) people fit filters directly to their carbs, dispensing with the trunking, and there`s been discussion here whether it makes a difference. This was clear evidence it does, quite a lot, and for little trouble or expense.
Jim

[KevJ+2]

I intend to put my KN cone filter in the nose for the cold air reason but how is it affected by the in coming rain or water from the bonnet (hood) above?
Kev.

[Chancer]

I used to wonder about that with all my Caterhams and Westfields but on the road and track even in torrential rain I never noticed a loss of power, quite the opposite in fact as the cooler denser charge improved breathing.

And that is the reason that flow restrictions aside, the standard Elan set up will give better cylinder filling than filters directly on the carbs in the heat of the engine bay.

[vincereynard]

Whilst having a cool air supply is obviously a plus I have wondered how much a lump of a filter
interferes with the air flow to the radiator. See attached (apologies if its your car!)

I intend to have a filter attached to the carbs. (boxed in to look like an original) and an air tube running to the front of the intake. I would prefer a separate vent (nasa style) on the nose but this could obviously be a step too far. The spaces at the side of the rad will be closed off.
This would also make it safer to drive through road floods etc.

I am seriously thinking (purists warning) of experimenting with vents at the back of the bonnet to let hot air out! I have noticed that many cars have stress around the bonnet catches and have wondered if this was more air pressure building under the bonnet than incorrect closure.

I shall now duck down behind the sofa.

Vince

[richardcox_lotus]

Vince,
Re holes in the bonnet to let the heat out - this has been done before - check Peter & Allison Coates' rally version. A colleague of mine once drilled holes in the rear bonnet lip, but I don't believe it helped too much.

Re the Air filter - you may want to look up Clive's Boys'solution with a cone filter on the side.

Let us know what you decide.

Regards
Richard

[vincereynard]

Richard,

Thank you for the information.

I've had a browse but cannot find any images.

Any chance of some links?

Cheers
Vince

[ecamiel]

The area at the rear of the bonnet is a high pressure zone so not suitable for vent holes. The air intake for the heater is located there for that reason.
Letting hot air out when stopped is a different issue. Lotus recommends holes in the inner wing for additional hot air exhaust standing or running.
Eric
64 S1 Hart

[richardcox_lotus]

Vince

http://rallyelan.com/previous-rallies/previous/

And for Clivey boys bits

http://www.cliveyboy.com/products/

Regards
Richard

[vincereynard]

Vince

http://rallyelan.com/previous-rallies/previous/

And for Clivey boys bits

http://www.cliveyboy.com/products/

Regards
Richard

Richard,
Thanks for that! The filter is just what I was thinking about. And those cooling holes at the extreme back edges - I imagine the problem is even worse with the 2 seater. But something like that is what I had in mind.

The air intake for the heater is located there for that reason.
Letting hot air out when stopped is a different issue. Lotus recommends holes in the inner wing for additional hot air exhaust standing or running.
Eric

Eric.
I was thinking more as vent at the rear corners. I would not want them in the middle or it would draw "engine" air into the interior. Is there much flow through the air vents without the fan going?

Move the radiator forward a bit and cut inner wing "gills" was a close plan 2.