Heater Core Bypass Mod (Tony Wa) [How To] - Page 17 - LotusTalk - The Lotus Cars Community
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post #321 of 343 (permalink) Old 08-28-2014, 04:46 PM
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Originally Posted by xxxotic View Post
I couldnt find the part number. The thing I was remembering was a guy that built his own buy using a bunch of radio shack parts on a circuit board. Too complicated for the average person. Does anyone know if Tony is still around? The switch that he put on my car works fine and I always keep it pulled out, since I never use the heater. He did all the wiring and soldering on it so I am afraid to take it apart to look at it, since I would never be able to figure it out if a wire came loose.
Yes, I saw the circuit board idea, would have loved to do that but it's just a little outside my comfort zone, I can solder but I don't do schematics. Would pay somebody a reasonable amount to build one for me though.

If Tony W was still lurking around here he could tell me straight away if that POT was what he originally was looking for. It's about $10 US so I may just order it anyway. I know theres a few on here who can tell me. Probably should have started a new thread instead of rekindling a 2 yr old thread. Just wanted to try and get the information in one spot for others in my position.

For now I have a basic switch I can use and just leave hidden or just fish the wires and leave them. I have the clam off for the Switch Pack upgrade so it seemed like a good time to get this done.

Anyway appreciate all the assistance
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post #322 of 343 (permalink) Old 08-28-2014, 04:47 PM
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Originally Posted by tvacc View Post
I have a complete kit here. Unopened. I bought for my son's car should he ever get one. He did. This past spring. Will look at it and see if there are any part numbers.
Thanks for any assistance Tony!
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post #323 of 343 (permalink) Old 10-27-2015, 11:37 PM
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disable recirculation pump ?

Instead of installing a bypass valve, can we disable the recirculation pump to the heater instead? Looking at the coolant circuit diagram, it seems the radiator and heater are separate circuit. Maybe just unplug the recirculation pump? Am I missing something?
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post #324 of 343 (permalink) Old 10-28-2015, 12:38 AM
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Found this message which explained that it's a bit more involved.
https://www.lotustalk.com/forums/f92/...tml#post453152

Still it should be easy to devise a circuit that is spiced in front of the recirculation pump that does the following:
- detect if the engine is running
- engine not running grant ECU direct control of recirculation pump
- engine is running, turn off recirculation pump when the cabin temperature switch is set to cold

If only we can directly change the ECU firmware, we wouldn't even need a new circuit.
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post #325 of 343 (permalink) Old 10-28-2015, 03:42 AM
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The recirculation pump is there to cool engine hot spots after shutdown as you discovered and is not a completely separate. Your idea seems more like a problem in search of a solution to me, the bypass mod is a very simple design, inexpensive, and easy to install and it has a fail-safe in that if it fails, the 'circuit' is left open as it would be without it.
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post #326 of 343 (permalink) Old 10-28-2015, 11:42 AM
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mavster,

The question of "fail-safe" really depends on what you include in your consideration of failure modes. For example, what if the mechanical bypass valve stuck in the close position? Or the bypass valve leaks like the air flaps? What if there is a vacuum leak? Are you sure that won't cause other problems for other subsystems?

We are comparing the robustness of a simple solid state electronics circuit vs a mechanical solution. You decide which is simpler and more robust.

Furthermore, the circuit to change the existing re-circulation pump behavior can probably be put together for $5.
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post #327 of 343 (permalink) Old 10-28-2015, 12:19 PM
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FYI post 79.

Quote:
Originally Posted by TimMullen View Post

[ . . . ]

Making it a manual bypass valve by the engine, would defeat the purpose of the recirculation pump. Even making it automatic (like the vacuum operated on valve) might cause problems with "cold" water from the bypassed heater circuit is suddenly recirculated into the cylinder heat. That's why the bypass valve is mounted up front - all it is removing from the circuit is the actual heater core (removing it as a heat source in the HAVOC box).

It would be possible to put a manual valve in the vacuum line to turn off the bypass in the winter, and make it automatically come on in the summer if you wanted to save the effort of doing the electrical wiring. But I would think that the on-off switch would be worth the effort.

-Shawn (2005 Elise) || New England Members of Lotus Ltd. (NEMOLL) - PM me to join local info list or NEMOLL || UberPost - Elise/Exige info: common problems/fixes, etc.
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post #328 of 343 (permalink) Old 10-28-2015, 12:36 PM
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Originally Posted by crazyhog View Post
mavster,

The question of "fail-safe" really depends on what you include in your consideration of failure modes. For example, what if the mechanical bypass valve stuck in the close position? Or the bypass valve leaks like the air flaps? What if there is a vacuum leak? Are you sure that won't cause other problems for other subsystems?

We are comparing the robustness of a simple solid state electronics circuit vs a mechanical solution. You decide which is simpler and more robust.

Furthermore, the circuit to change the existing re-circulation pump behavior can probably be put together for $5.
By fail safe I mean all of the default failures, ie. vacuum leak, loss of power/signal from switch, leave it in open/normal position. Also, if it were to stick it would be far more likely to stick in the open/default position since it requires the powered actuation to close and bypass. Add to that Keeper's repost of Tim's reasonable concerns and I think you have a lot of good reasons why that may not be the best solution. But if you've got nothing but time on your hands, go ahead and give it a whirl and let us know how it works out.
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post #329 of 343 (permalink) Old 10-29-2015, 11:00 AM
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Keeper,

Thanks for the feedback. Much appreciated. The issue of cold water from the bypassed heater circuit suddenly recirculated into the cylinder is a valid concern.

However, I don't think it is a problem. The coolant temperature coming out of the engine is around 210F . By the time, the coolant cools off in the radiator and goes back into the engine, the coolant temperature would have probably drop by half (let's say ballpark 100F). On the other hand, the water in the heater circuit, when not recirculated will never drop below ambient (let's say 70F). There is no way that kind of coolant temperature delta can hurt the engine.

Anyway, as an additional safe guard, we can add a temperature sensor in my electronic circuit to only override coolant re-circulation if ambient temperature is above 70F. Besides, I like the heater to work in the winter.
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post #330 of 343 (permalink) Old 10-29-2015, 12:03 PM
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mavster,


Hmm, passive aggressive!

If the new hose modification leaks all the coolant while you are driving across the desert, Is that fail safe? If a system has 2 failure modes (e.g. valve stuck open or stuck close) and one mode has a higher probability of occurrence than the other, does that make the system fail safe? I can go on and on.

In engineering, unlike marketing, fail safe has a very exacting meaning. The question is what do you mean by fail safe? You claimed, twice, the mechanical bypass solution is fail safe. In engineering, it will take a bit more than that.

Look, for what it's worth, here is the punch line. No decent engineer will claim these solutions, when considered as a whole, is truly fail safe. Think it over.
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post #331 of 343 (permalink) Old 02-16-2016, 05:49 PM
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https://www.lotustalk.com/forums/f313...ass-mod-79637/

found a servo actuated valve that works without additional wiring


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post #332 of 343 (permalink) Old 02-16-2016, 07:24 PM
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Upgrade clamps

I have had the Tony Wa heater bypass modification for a long time. But, the worm drive clamps that came with the kit kept working loose every few years, even though I wrenched them tight (heating and cooling cycles tend to work worm clamps loose - a common problem with coolant systems). So, I replaced them with Oetiker clamps about three years ago, and no leaks since.
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post #333 of 343 (permalink) Old 07-31-2017, 07:01 AM
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Old thread, but I finally bypassed my heater core last week - but at the engine like a few here have done. The problem I have with bypassing the heater core up front is that hot coolant is still flowing through the heater lines just below the dash. If you drive at night or on a cloudy day, just feel how hot the corners of the dashboard are once the coolant is up to temp. It's this additional heat that bakes the adjacent vent tubes, further heat soaks the dash, and ultimately reduces A/C cooling. Bypassing at the front is only keeping the HVAC box cooler - it's not preventing your dash vents from baking due to the adjacent coolant lines.

I installed a simple, but rugged inline ball valve between the engine and heater feed. This is way easier to service than fixing loose clamps buried under the front clam. By blocking at the engine and having no flow through the heater lines, my coolant now hits operating temp about 5 minutes faster thanks to the t-stat opening sooner. The radiator still does its job and my coolant temps peaked at 190 this weekend in lower 90s ambient temps, which is the same as before. This still isn't hot enough to trigger the recirculation pump upon shutdown, but if I ever hit upper 190s, then I'll just open the valve and let the pump do its job.

How's my A/C? The A/C is definitely colder and doesn't heat soak after 15 minutes like before. I didn't record numbers before this mod, but I'd safely say the A/C blows at least 10 colder during long drives! Some of that improvement is also from insulating the outer vent arms with Reflectix. The dash will still bake on sunny days, but at least the insulation barrier cuts back on thermal transfer to the long vent feeds. The two inner vents don't have as much surface area as the outer ones, so I left them alone.
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post #334 of 343 (permalink) Old 07-31-2017, 07:26 AM
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I forgot to add that the factory insulation on my HVAC duct was worthless! I applied two layers of reflectix which may be doing the most benefit for negating A/C heat soak.
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post #335 of 343 (permalink) Old 07-31-2017, 01:14 PM Thread Starter
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I haven't really looked at this thread in years (Elise sold several years ago), but got a notification that there had been a response to the thread. I don't disagree with the statements that blocking the heater hose flow to the front of the car will make the AC work some better. But as many have stated, you've now changed the designed coolant flow to the engine by blocking a path of circulation directly back into the engine (into the head as I recall, but time has passed....). The ballcock valve approach was done several years ago by another member (and maybe more than one) and lots of discussion ensued.

As usual, I will say that I am the authority only on my own opinion and there are certainly lots of ways to look at this. I will say with certainty that looking at a temp gauge of the aggregate coolant output temperature of the engine can be very misleading as an indicator to distinct internal temperatures in various parts of the motor. You could be cooking the head due to no flow in that critical area while the block stays in normal temp range as indicated on your gauge. It would sort of be like not bleeding coolant at the highest point of the system. You could have hot pockets.

On the other side, your engine could warm up differently from cold than originally designed. Does it matter, maybe, I don't know, but its different..... Might make it pollute more while warming up, but only testing would say so.

When I did the original bypass system, I was unwilling to risk routing the coolant thorough the engine in any other manner from which Toyota designed. My thinking was and is is that they (Toyota engineers) are way smarter than me and also that the Elise is asking more from the engine that Toyota originally intended, so it seemed appropriate to minimize the changes by keeping the circulation path standard (hence the three way valve in the mod). The coolant still flows in the normal path to the engine, just the heater core is bypassed.

At the end of it, the main heat in the front end and sills comes from the radiator tubes. None of our potential improvements addresses that in a significant way.

Again, it may be fine to bypass this heater circuit coolant path to the engine. You can only know by testing.

Take care
Tonywa

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05 Elise (Stage II, FrankIntake CAI, heater bypass)
04 MINI S (heavily modified)
06 IS350
69 Lotus Elan S4 SE - (orig black badge, weber, etc)
59 Austin Healey Bugeye Sprite (heavily modified, 70WHP)
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post #336 of 343 (permalink) Old 07-31-2017, 02:16 PM
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Welcome back Tony!

Your work has been built upon by others and your contributions are timeless

i agree, stopping the flow is not the way I would go about it. If concerned about heat flowing in the front of the car, I would put a bypass in the back, rather than a shutoff.

I think the biggest source of heat in the dash area is sun, when facing the sun the heat generated by the windshield is ferocious

thanks again
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post #337 of 343 (permalink) Old 07-31-2017, 07:13 PM Thread Starter
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Hello Exigegus,

I agree that the bypass in the engine compartment should give the best improvement in cabin temp and still keep the original coolant routing. I put the original bypass up front for a few reasons - I wanted to go in the A/C evaporator box and insulate as much as possible so I was already committed to working inside the front end, 2) putting the valve up front allowed for getting into wiring harness and vacuum source with the least drama as possible (I really wanted to have control of the valve inside the cabin) and 3) it minimized the possible cold coolant shock (just the coolant in the heater core). I really couldn't tell you if coolant shock is a concern or not if you bypass in the engine compartment. Might be worth someone spending some brain cycles on it by someone.



The sun heating that tiny cabin is a big issue. Big glass and shallow angle.

On a personal note, I have been happy that people have run with the original concept and was blown away by the healthy review and constructive contributions of so many. Just plain cool.

Thanks and enjoy your car. Still the best performance bargain for the buck bar none. It was always so much better than i was.

Tonywa

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05 Elise (Stage II, FrankIntake CAI, heater bypass)
04 MINI S (heavily modified)
06 IS350
69 Lotus Elan S4 SE - (orig black badge, weber, etc)
59 Austin Healey Bugeye Sprite (heavily modified, 70WHP)
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post #338 of 343 (permalink) Old 08-01-2017, 01:00 AM
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Glad to see you back Tonywa28. You created a monster of a thread that is standing the test of time. You raise many of the valid concerns discussed in depth earlier in this thread, some by the late Tim Mullen who is probably thwacking me right now!

I did intend to do a bypass valve in the rear until I saw how little room I had to access the heater return port. Also, seeing how many other engine platforms have people blocking the heater core at the engine without ill side effects was definitely reassuring. Some celicaforum guys did this mod in '04 with no issues (a few even capped the heater ports and deleted the heater core). If mine should cause problems or lead to a head gasket failure over time, then I'll have the evidence to say so. Until then, I'm impressed my radiator is still keeping ideal temps.

The sun bakes the dash at day, but those hot heater lines are also baking the vent arms from below. Just feel how much heat is emitting from those lines under the dash come nightfall. Some say that's the radiator exhaust seeping through the window seal, but I don't buy that. If that was the case, then why is the front-center section of the dash cooler than the sides at night? I can't eliminate the sun's heat 100%, but 3M crystalline does help.
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post #339 of 343 (permalink) Old 08-01-2017, 03:32 AM
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Originally Posted by Tonywa28 View Post
Hello Exigegus,

I agree that the bypass in the engine compartment should give the best improvement in cabin temp and still keep the original coolant routing. I put the original bypass up front for a few reasons - I wanted to go in the A/C evaporator box and insulate as much as possible so I was already committed to working inside the front end, 2) putting the valve up front allowed for getting into wiring harness and vacuum source with the least drama as possible (I really wanted to have control of the valve inside the cabin) and 3) it minimized the possible cold coolant shock (just the coolant in the heater core). I really couldn't tell you if coolant shock is a concern or not if you bypass in the engine compartment. Might be worth someone spending some brain cycles on it by someone.



The sun heating that tiny cabin is a big issue. Big glass and shallow angle.

On a personal note, I have been happy that people have run with the original concept and was blown away by the healthy review and constructive contributions of so many. Just plain cool.

Thanks and enjoy your car. Still the best performance bargain for the buck bar none. It was always so much better than i was.

Tonywa
I actually have a car with your original work! It some digging, but a couple years ago the solenoid failed and I had no idea why my plumbing didn't match the service manual until a found a thread with you and ZTEC. I have been happily running it ever since. I am starting to blow a fuse though, and I can tell when the bypass is no longer working. Definitely one of those "must have" mods.

"Lots Of Trouble; Usually Serious"
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post #340 of 343 (permalink) Old 03-19-2018, 09:00 AM
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Garage
Since some folks have been asking about specifics, I thought I'd share what I bought.

GM Original Equipment 214-329 is the EGR solenoid I got. $27

In order to wire it up, I found this pigtail. I don't know if anyone has mentioned the existence/availability of this part.
GM part number 1P1362 $9 ($5 if you order directly from China)

Digikey CTS Electrocomponents 450T328F103A1C1
I'm using that POT to control the valve. I cut down and filed it to shape. It is long.
That POT has the switch in the right place (left most position), but is normally open instead of closed. $13.50 shipped

To fix that problem with the POT, I bought this relay.
Microcenter 5V Relay Module I'll use the normally closed side of that relay. $5

I bought the Motorcraft YG350 as was recommended in the instructions. $24
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