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View Full Version : TR2/3/3A Anyone running a cold air duct to the carbs?



karls59tr
12-17-2013, 01:12 PM
I have a header on my 3. I installed a heat shield to keep the excess heat from the SU's. I also thought it would be a good idea to run a duct from the radiator shroud up to the mesh/foam air filters. I used a piece of corrugated plastic duct tubing that I thought would do the job but found out in a write up by Ken Gillanders that the turbulence caused by the "corrugated" duct reduces the air flow by half! Mine is just a street car not a racer :-) and I don't know how much difference getting cooler air to the carbs really makes but I'd like to build something that would help keep the under hood temperature down for the carb intake. Any ideas or pics of cold air duct setup?

trrdster2000
12-17-2013, 05:28 PM
Karl you might open a whole kettle of worms on this subject. The arguments might go something like this:
1. Street driving doesn't move enough air by the carbs to make a difference.
2. It's not getting the cooler air in, but getting the hot air out at town driving.
3. If you make a box for the carbs, which works great at speed but when you stop for a ice cream cone, the heat will build up in the box and unless you put a pump to blow that hot air out, starting is a problem.
4. Look at the MGA for reference on the size of the duct work required to make a difference.
Just a few things I ran into over the years.

Wayne

Geo Hahn
12-17-2013, 06:53 PM
...Any ideas or pics of cold air duct setup?

As I recall, back in the day it was a practice among some racers to remove the right hand headlamp & bucket making it into an air intake.

TuffTR250
12-17-2013, 07:08 PM
I have mocked up with cardboard a damper below the radiator that goes as far to the left and right as possible and then curved the ends up. It seems like it might work to force air up around the inner fender to blow cool air into the engine compartment around the radiator (and some through the radiator). Not sure this would help cool the engine compartment, but seems that way to me when I envision it. Not sure I'll get around to actually making one. Then, of course, I'm not sure how I'd know if it actually worked. That would be an interesting project for engineers in a wind tunnel. :)
Regards,
Bob

RossL
12-17-2013, 08:30 PM
As I recall, back in the day it was a practice among some racers to remove the right hand headlamp & bucket making it into an air intake.

https://i665.photobucket.com/albums/vv20/rossl56/Spring%20Summer%202012/TR6Intake.jpg (https://s665.photobucket.com/user/rossl56/media/Spring%20Summer%202012/TR6Intake.jpg.html)

vivdownunder
12-18-2013, 09:11 AM
I suspect Ken Gillander's findings applied to a race car with open carby intakes such as ram's horns. Foam aircleaners on a road car should even out any turbulence from ribbed ducting.

I found an answer to increased engine bay heat from a header by only using side deflectors on the radiator. This allows plenty of cool air to pass over the top of the radiator and make a difference to engine bay temperature. I've also fabricated a deflector beneath the shroud to bring cool air up into the lower portion of the radiator. Painted out matte black it goes unseen.

A 12" electric fan takes care of city traffic and an electric fuel pump keeps the carbies filled.

These various mods allow the car to operate in summer temperatures over 100 degrees F without any fuel vaporisation or overheating worries.

Viv

TuffTR250
12-18-2013, 07:06 PM
Viv, could you post a picture of the side deflectors and also of your deflector beneath the shroud? I'm curious how you mounted those. Thanks!
Regards,
Bob

karls59tr
12-18-2013, 08:52 PM
Viv, I'd like to see pictures of the deflectors as well if it's convenient. Karl

karls59tr
12-18-2013, 08:56 PM
Ross. Nice motor. Are those Mikuni's? TR250? What kind of HP are you getting? :-). Karl

Geo Hahn
12-19-2013, 11:30 AM
Not Viv -- but this is the deflector I use on the TR3A to throw more air at the lower third of the radiator --

https://i1214.photobucket.com/albums/cc499/Ahwahnee18/TR3/TR3-Dam2_zps3d61c84d.jpg

Simple pair of metal brackets use existing bolts (end of crank hole stays) --

https://i1214.photobucket.com/albums/cc499/Ahwahnee18/TR3/TR3-Dam3_zps784f2618.jpg

It takes a beating as it sometimes serves as a 'feeler' for parking lot curbs stops. The pattern showing the angle of the bend in that bar stock --

https://i1214.photobucket.com/albums/cc499/Ahwahnee18/TR3/TR3-Dam4_zps677268df.jpg

pdplot
12-19-2013, 01:13 PM
Wow - that's some engine. Triple carbs? What kind of horsepower are you getting and what's with the extra MC reservoir?
The only thing in common with my engine is the valve cover...

karls59tr
12-19-2013, 01:29 PM
Geo That air spoiler looks like it will do the trick. Think I'll build one just like it. Cheers Karl

TuffTR250
12-19-2013, 07:46 PM
I must say, when I made my cardboard template, I got the idea from Geo a few months back. Thanks Geo!! I was thinking of making it out of metal so I could curve the ends up to divert air up around the radiator into the engine compartment, as well as push air to the bottom of the radiator.
Regards,
Bob

karls59tr
12-19-2013, 08:58 PM
I must say, when I made my cardboard template, I got the idea from Geo a few months back. Thanks Geo!! I was thinking of making it out of metal so I could curve the ends up to divert air up around the radiator into the engine compartment, as well as push air to the bottom of the radiator.
Regards,
Bob
What kind of metal were you thinking might be suitable? Sheet metal? aluminum? I suppose metal would be less forgiving than 3/4 plywood for curb damage but like you I think I'd try fabricating a metal one of some sort.

TuffTR250
12-20-2013, 10:01 AM
I'd probably use 16 gauge sheet metal. I think any thinner sheet metal would vibrate or flop around too much.
Regards,
Bob

Rhodyspit75
12-20-2013, 10:11 AM
How about using a piece of a modern car bumper cover. You can probably find one lying on the side of the road at the scene of a fender bender. If not I'm sure a local body shop will have plenty to choose from. Most likely for free.