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Old 07-18-2022, 05:21 PM   #1 (permalink)
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Electronic / MAP Thermostat Control Retrofit

Countless studies and significant OEM adoption has shown that higher engine coolant temps help increase highway cruise fuel economy, but introduce increased risk of detonation under high loads when combined with high cylinder pressures; for this reason the major auto manufacturers have adopted electronic thermostats that can increase engine temps at lower speeds and engine loads and decrease them when more performance is required.


Electronic / MAP-controlled thermostats have been adopted by Audi, BMW, Ford, GM, Volvo, and Volkswagen and they can be controlled by modern aftermarket fuel injection ECU like Holley, Motec, etc... (Most OEMs just use a 3D map consisting of Load %, Vehicle Speed, and Coolant Temp and then send a PWM control signal appropriate for the particular thermostat.

See Mahle Paper: ww.mahle-aftermarket.com/media/local-media-north-america/pdfs-&-thumbnails/catalogs-and-literature/thermostats/mo-2-1013.pdf

-I don't have enough posts on here so I can't post this as an actual link; sorry.


I'm interested in leveraging my GEN1 SBC's Holley HP EFI system's ability to have a custom MAP table generate a PWM output and potentially control an existing electronically controlled thermostat that's been installed inline in the engine "coolant out" radiator hose.

I'm having a difficult time getting details on inlet and outlet sizes for these things and how the bypasses work, and the ideal signal that's required to control them.


I have a LOT of eco modding improvements in my 1979 Corvette, but I'm not looking to make this a "build thread", I'm just looking to explore this idea with other potentially like-minded eco modders.



I am aware that Davie's Craig in Australia has used their electronic water pumps and controllers in a similar PWM control strategy that alters the speeds that the water pump spins at to accomplish the same goal, but I prefer a traditional mechanical water pump for a LOT of reasons, not the least of which includes reliability and increased engine coolant system pressure (most OEMs seem to agree with me, too).



Adam

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Old 07-18-2022, 08:30 PM   #2 (permalink)
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Instead why NOT a set of controlled flaps in FRONT of the radiator to open close on command PLUS you could really run hot like 220/250 for highway and then run very cool for power.

Plus blocking all of most of the air into the radiator and engine chamber is also said to help MPG... Not sure how...

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Old 07-19-2022, 05:54 PM   #3 (permalink)
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Quote:
Originally Posted by racprops View Post
Instead why NOT a set of controlled flaps in FRONT of the radiator to open close on command PLUS you could really run hot like 220/250 for highway and then run very cool for power.

Plus blocking all of most of the air into the radiator and engine chamber is also said to help MPG... Not sure how...

Rich
Mostly because if I could find the right electronic thermostat and it's signal requirement, I KNOW I could make that work.

I agree about the idea of running something like grill shutters could be superior as you'd get aerodynamic benefits, too, but I have no hope in my ability to fabricate a custom one up or to be able to properly control it on my car.


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Old 07-19-2022, 06:11 PM   #4 (permalink)
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Quote:
Originally Posted by racprops
Plus blocking all of most of the air into the radiator and engine chamber is also said to help MPG... Not sure how...
All the air that passes through the radiator is subjected to the clutching fingers of interference drag until it finds some way out.

Quote:
I agree about the idea of running something like grill shutters could be superior as you'd get aerodynamic benefits, too, but I have no hope in my ability to fabricate a custom one up or to be able to properly control it on my car.
Simplest install I can imagine would be a sliding shutter with a choke cable control. My VW Dasher had such a thing [minus the cable control], gone by the time I got the car and I can't find a picture.

No idea on the custom MAP table.
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Old 07-19-2022, 06:16 PM   #5 (permalink)
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racprops if newbvetteguy used an electric active grill block instead of the electric thermostat I dont think it would work as it takes quite some time from when grills are opened to coolant temp dropping compared to the time it takes to open the thermostat.

Consider that when the driver floors the zoom zoom pedal the goal of opening the thermostat is not to immediately cool the coolant. its to dump that heat into the radiator so the whole cooling system drops in temperature virtually instantly.Otherwise with your idea the engine may overheat before the radiator can cool down the coolant.

According to the paper op linked the electric thermostat is more than just a regular thermostat with computer control. It has a wider range, it will flow better than a standard thermostat. It also responds faster. I.E may close when DFCO is occurring before coolant temperatures begin to drop.

My questions to OP are as follows:
1. Have you considered the easier route of trying to find/modify a conventional thermostat to operate at a higher temperature? Its a much simpler middle ground between doing nothing and an electric thermostat.
2. Have you considered things like a warm air intake?
3. Have you thought about how you are going to modify the ECU to prevent the radiator fan from turning on?
4. Have you thought about how you will modify the ECU to account for retarding ignition timing and cam phasing(if applicable) as the engine knocks. will your software detect this?
5. what kind of fuel are you running? is it a high grade?
6. instead of trying to fit an electric thermostat why not go on amazon and search "electric ball valve" and plumb that into your radiator inlet hose. seems much simpler. I don't have enough posts on here so I can't post this as an actual link.
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Old 07-19-2022, 06:32 PM   #6 (permalink)
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I think you should first try to measure the difference with a blocked radiator. I know my car seems to use more fuel at 180F vs 200F, but that is probably because the ECU is mapped so that it prioritizes warmup.
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Old 07-19-2022, 06:35 PM   #7 (permalink)
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Now this is getting interesting for me as well.

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Old 07-19-2022, 06:39 PM   #8 (permalink)
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Older Chevy's use to have a stove pipe a small pipe from the header to the air intake with a thermo valve/flapper so on cold mornings it would cut off cold incoming air though the air cleaner intake and have suck hotter air right off the exhaust manifolds.

Perhaps this idea can be updated for more HOT air for MPG??

Rich
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Old 07-20-2022, 07:37 PM   #9 (permalink)
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Oh I had something like that once. I put a thermostat bypass on my coolant system. On a real hot summer day it would bring engine coolant temps down to around 160F. I would use it on stop and go traffic and when towing before I started a hill climb.
You can get up to a 205'f thermostat for common applications, some times it's part of a "cold climate package".

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