cold air box?

[anthony7777]

got my engine out and engine bay totally stripped, been snooping around left fender area and "fresh air duct" now would be the appropreat time to design/build/buy/install a "cold air box", anyone done this?, think its viable/worth doing? /bcforum/images/%%GRAEMLIN_URL%%/savewave.gif

 

[roscoe]

Anthony,
Cold air is denser, and does boost horsepower some. I'd rather have air filters where I drive, and I doubt that you would notice a difference under normal driving conditions. If I had a 100 M I probably wouldn't remove it, but I'd worry every time I drove through a cloud of dust. Only a dynomometer test would tell for sure. Anyone have the data?


p.s. I was born on May 12th too! (1952)

 

[anthony7777]

roscoe, thanks for your responce, so your exactly one year younger then me. /bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif

 

[Dave Russell]

Air density increases about 1.8% for each 10 degree F temperature drop.

If intake air were reduced from 200 to 100, not hard to do, density & power would be increased about 18%. Where else can you get this much power gain so easily? Carb jetting does have to be noticeably richer.

In the case of the 100 LeMans, after running down the road for a bit, the carbs & intake are very noticeably colder than their surrounding air.

The filter problem is easily solved by putting a good filter on the front end of the intake duct ahead of the radiator & hot stuff.

A lot of performance engines use cold air intake from in front of the radiator.

A dyno is not really needed. Thermometer measurment of the temperatures will tell the story.

See pic of a 6 cylinder with CAB.
D

 

[anthony7777]

Dave, that's pretty much the idea im kicking around, looking at the empty engine bay i began mentally designing a box to take place of the old round air filters and using the fresh air intake plumbing hose to feed the box, im up to the part now on how then to get fresh air back into the cockpit, run two separate lines? use and intermediate baffle? you know that kind of stuff, i think the filter part would be easy.

 

[Ed_K]

Air density increases about 1.8% for each 10 degree F temperature drop.

If intake air were reduced from 200 to 100, not hard to do, density & power would be increased about 18%. Where else can you get this much power gain so easily? Carb jetting does have to be noticeably richer.

In the case of the 100 LeMans, after running down the road for a bit, the carbs & intake are very noticeably colder than their surrounding air.

The filter problem is easily solved by putting a good filter on the front end of the intake duct ahead of the radiator & hot stuff.

A lot of performance engines use cold air intake from in front of the radiator.

A dyno is not really needed. Thermometer measurment of the temperatures will tell the story.

See pic of a 6 cylinder with CAB.
D

Wow ! I didn't realize that it would help the horsepower that much. That would be about 27 extra HP on a BJ8.

/bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif /bcforum/images/%%GRAEMLIN_URL%%/driving.gif

 

[Dave Russell]

Anthony,
The pic originally came from here:
https://www.team.net/mharc/archives/html/healeys/2004-08/msg00393.html

Although this was for a RHD car, it might give you some ideas.

Ed,
There "could" be a down side. In very cold weather the carbs could be too cold. More modern versions use a temperature regulator to blend hot & cold air to keep it more constant with varying ambient conditions. Helps a lot with emissions.

Having said this, my BN2 seems to have no problems in quite cold outside temperatures.

Maybe worth investigating.
D

 

[AJAX50]

I've been trying to design a cold air box for my BJ8 (RHD).
I've got Webers on the works magnesium inlet manifolds, so space is very tight. Do you think there would be any significant benefit in just feeding ,say, three 2" pipes to the carb. intake areas. If so, where are the best high pressure areas to locate the pipe inlets?

 

[oslo100]

On the filter issue, I've tried the ITG filter supplied by Denis Welch
https://www.bighealey.co.uk/section.php?id=16&page=2
I use the filter adaptor straight on to the cold air box. Works very well and reduce the stress level a lot when driving on dusty roads. During the summer I use an airduct, but late autumn with temperatures dowm to 4-5 Celsius I drive without the duct for the reasons mentioned by Mr. Russell.
I guess using a filter mitigates some of the air pressure created at higher speeds in addition to reduce the maximum cold air potensial, but I am not sure whether this is highly relevant. Would also like to hear if anyone has comments on whether to attach the filter to the cold air box or on the front of the air duct, close to the grille?

Georg

 

[zblu]

Went with rams and KN filters on carbs and use the flex to feed the cold air onto them, Its an M spec setup except for this, the AH ali cold air box with inline filter sits on the shelf until I get time to see which is best

 

[Dave Russell]

Ajax,
I think you would need 2.5" dia. hoses to get enough air flow. Since there would be no useful ram effect at speeds below 120 mph, a high pressure location would not help much & ram effect would present it's own mixture change problems. Better to locate the intakes in a convenient but cool location & not worry about ram effect.

Georg,
I tried the DW filter in the recommended location. As you will note, with the filter stuffed inside a 4 1/2" diameter hose, the larger diameter portions of the filter are blocked by the hose walls. After several tries, to verify, there was just so much air flow restriction that the engine became increasingly choked & would not run above 5,000 rpm.

Another fellow placed the DW filter inside the front end of the hose & claims it worked. I contacted DW & he said that the filter would not flow enough air to support more than 150 HP. I suspect from experience, that the true number is well below 150 HP, due to the previously mentioned hose wall blocking of a good portion of the filter outer diameter.

I used a K&N #RU-2590 filter on the front end of the hose & it works very well. See attached pic.

On the BN1, BN2, it's very easy to replace the top five grill retaining nuts with wing nuts. You can reach in through the wheel wells & remove the nuts, the grill hinges out on it's bottom pegs, & can be removed for very easy filter service.
D

 

[anthony7777]

dave that looks very nice, so you didnt use any of the "fresh air system" ?

 

[zblu]

Hi Dave Russell,
My filter as supplied was a cone shaped one that fitted just before the ali box inside the flex, so what i've done is put the filters on the carbs, with the air flow onto them from the flex, yes I know I lose some force effect, but the air is still cooler and with the single air filter at the end of the flex being an obstruction, have I lost or gained anything, still out on this until I can get it checked out

Cheers

 

[Dave Russell]

There should be "some" benefit. As I mentioned, a cone filter inside of a tube may or may not allow enough air flow.

I forgot to mention that if a sealed system is used, the carb float bowels must be vented to the intake system, not to atmosphere. If not, the pressure differences will screw up the fuel flow.
D

 

[Dave Russell]

Anthony,
The old cars like mine only had a fresh air intake on the RH side. The LH side was free space.

Earlier in the Keith Pennell response that I quoted, he mentioned being able to fit in fresh air intake AND carb cold air intake. I'm sure it will take some head scratching to figure out. How badly is the LH fresh air to the cockpit needed?
D

 

[zblu]

I am actually thinking of upping the 4" to a 6" tube, and re: you pic of the filter in front of the rad, over here we have enough trouble with keeping cool without obstructions to the rad!, ambient temp is in the range of 20-45C in the shade, not on a black tarmac!
Cheers

 

[Dave Russell]

We have very hot summers where I live also. Keep in mind that the filter flows air freely & is not really much of an obstruction to radiator flow even though it appears to be a solid obstacle.
D

 

[dphilippo]

Interesting topic. I don't think that losing the "cold air" duct is any great loss. When it's hot out I keep mine closed anyway because two minutes at a stop light will turn it into a hot air duct once you get going again. I get more cold air into the footwell via the vent windows on my BJ8 than from the cold air duct.

Drew,
65 BJ8

 

[GregW]

Hi Dave,
Is the cold air box double walled? Or is that over-engineering.

 

[Dave Russell]

Hi Greg,
Single walled seems to be fine. It may get hot at a stopped idle, but once moving, the engine will draw somewhere between 50 & 250 CFM of air, the metal will come back down close to ambient temperature pretty quickly. The more throttle & rpm the more quickly it cools, just when you need it. The heating actually helps warm up in cold temperatures.
D