Heater Core Bypass Mod (Tony Wa) [How To]

[Tonywa28]

Thanks to Rob (who pointed out the obvious vacuum source, DOH! ), I re-invented the whole thing and it is working great for me. One hour ride yesterday that was nice and cold. Heat comes on very quickly after switching out of bypass mode. Best thing is there are no real custom parts. I have an extensive write-up with pictures, parts lists, cost and diagrams atttached. I would be willing to put some kits together if people are willing to reimburse my time and shipping. Maybe $25 bucks (?) above parts and shipping for running around and packaging. My feelings won't be hurt if no one is interested. I'd like to use the $$ to start working on a short shifter solution (at the transaxle, not the lever).

Now to the disclaimer. This mod works great for me. I can't promise it will work for everyone, but I don't see how it could hurt. Easily reversible if so desired. Use at your own risk....affect on warranty unknown....your mileage may vary....CMA...CYA.....

BTW - I see no difference in indicated coolant temperature with or without the bypass

I think we should get a handful of testers (2 or 3) to check their results before we go wild with this mod. I sent Rob a preliminary document and I think he's working on an install now. Hoepfully he'll post results.

To the poster with 226 degrees. That sounds like a problem with your specific car. I've never seen 200 degrees and almost never see 193 (maybe 2 or 3 times in almost 2 years). Check you fluid levels, check for vacuum leaks. Use may want to try some Red Line Water Wetter (I'm a believer).

[Tonywa28]

FYI - the mod cannot prevent your side sills from getting warm.

[Randy Chase]

Great write up Tony. Truly impressive.

[Bane]

Agreed... simply awesome contribution.

I will buy a kit from you simply for your writeup (I need an Elise first though)

[TekZones]

Just a question which I think I know the answer but have to ask. Is there any way to access the interior of the side rails without removing body panels or other major assemblies? My thoughts are to possibly use a reflective (solar) blanket with injectable foam that solidifies like some companies use to ship fragile items like computer monitors. The stuff is really light weight and and be molded to some extent. Even a 1/2 to 1 inch barrier would creat a huge insulating factor. Estimated total weight would be about 1-2 pounds. Thoughts? Coments?

[an0nym0u5]

This thread needs an actual POLL!!!!!

[David]

Great write-up. If you get a kit together, I'd be glad to reimburse you for time and shipping.

[Tonywa28]

Spent some time today on testing. Results are very good in my opinion (see attachment) Didn't spend a lot of time prettying up the write up, but forgive me. Content is king anyway!

I've got around 150 miles on the mod, no issues.

[Tonywa28]

LW,
Are your fans running when the AC is on? They should be howling like the devil up front.

[TekZones]

This is the best write-up and early follow-up I have seen in a long time for anything. I will get the parts and have ready to install after my 1000 mile service in a week or so. If you decide to put a kit together I would be very willing to buy it from you especially considering the work and testing you put into making a difficult situation better for all concerned.

[Tonywa28]

So you're an O-villian or is that O-Villain.....regardless, let's have a beer.
jwattwood@cfl.rr.com

[jim-clayton]

I had very similar results. I documented a 6 degree lower vent temp when I bypassed my core.


Check your Freon level. You probably can add some. I get 52 degrees out the vent. South Florida. 95 degrees 90 percent humd.

From a previous post of mine: ...........
My AC starts at 52 degrees and maxes out at 58 degrees after 1 hour of city driving. 96 degrees outside with 107 degree heat index. I was out today verifying the cooling power of my ac.

Bypass heater core.
Insulate duct.
Tweaked freon level to obtain 248 on high gauge and 39 on the low gauge. 39 on the low side is a good sweat spot. I did some testing.

[®ob]

Tony, one more thought I had. Get some aluminized heat shield cloth and wrap it around the air box vent tube. That should repel some heat from the rest of the car. Might be worth a degree or 2, and its only about 30$.

[JnC]

Great work!

Question, would it be possible to hook up the bypass back at the engine instead of at the heater core? That way the hot water associated with the core loop wouldn't circulate thru the framework.

[roadrunner]

Originally Posted by JnC

Great work!

+1
Excellent work and some good analysis - sign me up for whatever kit or finished package you put together...

[pianomaniac]

Great write up, Tony. Thanks for all your time and work in documenting this for us.

Best,

Ron

[lotus54]

Sounds great.
I'm certainly interested in the kit, even if it doesn't get that hot here.
I haven't noticed any hot air in the vents, but it seems this would really make a difference it the flap wasn't sealing perectly.

Keep us posted
mark

[Randy Chase]

I was driving bare footed today... after an hour of freeway, I noticed I could not leave my foot for more than a second at the end of the footwell behind the dead pedal. It gets extremely hot there.

Looking forward to this mod. My AC quit working after 20 minutes today.

[Tonywa28]

aw shux! Seriously, thanks for all the kind words. The board kept me going when I was getting worn out with the project a week or so back. It really does motivate you when you get some feedback!!

Special thanks to Rob for his help! He gave me some good input and reviewed my ideas and documents.

Looks like Jim-Clayton did some eariler testing on the straight bypass (good job!)with similar results to mine (5-6 degrees difference), so now I have more confidence that this is a common problem. Living in FL is a motivator, isn't it Jim. Also lowering the firewall heat soak is a less obvious, but maybe just as important by-product of the by-pass.

Sounds like there's enough momentum for me to take some names and put together some kits. If your so inclined, send me an email tony.wattwood@gmail.com. I'll probably collect emails for a few days (say end of the week, 7/29) to get the scope of the number of kits I need to make up, then I'll get back to each of you with the cost and availability date. If I see a number of quick responses, I'll go ahead and start ordering parts to cut down the time lag...please don't leave me hanging!

Two quick comments on recent posts
1) Foam in the sills. I've never really looked at the sills very hard to see the is there is any access, but I do know in Japan some of the Sport Compact guys are injecting their frames with foam for added stiffness. Should make them cooler and quieter too!
2) Bypass in the engine compartment rather than up front to have cooler sills. Likely wouldn't help too much as the main radiator pipes still go from back to front to the radiator. It would also take a larger amount of the available coolant out of circulation. It also bugged me a bit that when the bypass was switched off a fair amount of cooler water would hit the system. But I'm over analyzing....always. It would probably work great.

Again, Thanks for the Thanks!

PS - I guess I hijacked this thread from poll to fix. I get on tangents really easy....as you guys can clearly see.

[JnC]

Originally Posted by Tonywa28

2) Bypass in the engine compartment rather than up front to have cooler sills. Likely wouldn't help too much as the main radiator pipes still go from back to front to the radiator.

I may be making a bad assumption, but if the water in the heater core loop is as hot as the water in the radiator loop, wouldn't you be cutting the amount of hoses running hot water by half?

Or is the amount of heat generated by the engine now fully transferred to the radiator loop, and the net dissipation from hose to chassis hardly changed?

Originally Posted by Tonywa28

It would also take a larger amount of the available coolant out of circulation. It also bugged me a bit that when the bypass was switched off a fair amount of cooler water would hit the system. But I'm over analyzing....always. It would probably work great.

I think Tim made that point too. One might have to be careful not to shunt unheated water into a hot engine.