danl
20+ Year Contributor
- 886
- 274
- Apr 8, 2002
-
Severn,
Maryland
Having recently gotten back into the DSM game I was disappointed to discover the OEM thermostat is no longer available. The main reason for running an OEM thermostat is that it had a larger opening than aftermarket thermostats, theoretically allowing more coolant flow when required.
The 1990 FWD in my profile came with a Stant rated at 180F. I ordered a "Super" Stant to replace it and when it arrived, it was a re-boxed Motorad. Looking into this further, they are now the same company. Doing testing in boiling water both these thermostats did not open to what I subjectively would call a sufficient amount. I was also looking for a larger diameter opening, like you would find in an OEM Mitsubishi thermostat. Below is the "Super" Stant, which says Motorad on it.
I was on the hunt for a thermostat with a large opening, but they all looked like the Stants. I discovered that Tama/NTC is the OEM manufacturer for a lot of Japanese engine manufacturers. Looking at pictures of an OEM mitsubishi thermostat and the Tama CATALOG, you could see some models with similarities with the 1g thermostat (pictured below). The Tama website showed THIS as the replacement for a 1G. It is not the same look as the original, however most important to me was the diameter of the valve in the thermostat. It is 4.4mm larger than the Stant valve opening. Calculating the surface area of both using Pi x R^2 = gives me 2222mm^2 surface area for the Stant opening and 3018mm^2 for Tama, or 35% larger. The Tama valve appears to have a longer stroke when tested in boiling water, but it was difficult to measure accurately. Finally the Tama one shrouds the valve opening less than the Stant, where you can see the stamping at the opening interferes with flow. Will all this make a difference? I have no idea because I don't know what the water pump flow is at different engine speeds. I don't see a downsize of a larger opening though.
If you are interested in trying a Tama thermostat, the part # is W52-88B for an 88C/191F model and W52-82B for a 82C/180F model. I tried substituting different numbers for the 82 and 88 in the part number but was not able to find lower temp ratings in stock. You can find the 82C model in 80's honda goldwing motorcycles, 80's toyota cressida's, honda preludes, etc. The 88C model was pretty ubiquitous, you can just search for the Tama brand thermostat for a 1G through Napa. I purchased an 82C model from Napa, their part# ATM 1542903, cross referencing to a mid 80's Toyota Cressida.
Of note it appears Tama may be the OEM for some of the engine bay sensors in a 1G. https://www.tama-e.co.jp/omrop2016_180329/top.html
The 1990 FWD in my profile came with a Stant rated at 180F. I ordered a "Super" Stant to replace it and when it arrived, it was a re-boxed Motorad. Looking into this further, they are now the same company. Doing testing in boiling water both these thermostats did not open to what I subjectively would call a sufficient amount. I was also looking for a larger diameter opening, like you would find in an OEM Mitsubishi thermostat. Below is the "Super" Stant, which says Motorad on it.
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I was on the hunt for a thermostat with a large opening, but they all looked like the Stants. I discovered that Tama/NTC is the OEM manufacturer for a lot of Japanese engine manufacturers. Looking at pictures of an OEM mitsubishi thermostat and the Tama CATALOG, you could see some models with similarities with the 1g thermostat (pictured below). The Tama website showed THIS as the replacement for a 1G. It is not the same look as the original, however most important to me was the diameter of the valve in the thermostat. It is 4.4mm larger than the Stant valve opening. Calculating the surface area of both using Pi x R^2 = gives me 2222mm^2 surface area for the Stant opening and 3018mm^2 for Tama, or 35% larger. The Tama valve appears to have a longer stroke when tested in boiling water, but it was difficult to measure accurately. Finally the Tama one shrouds the valve opening less than the Stant, where you can see the stamping at the opening interferes with flow. Will all this make a difference? I have no idea because I don't know what the water pump flow is at different engine speeds. I don't see a downsize of a larger opening though.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
If you are interested in trying a Tama thermostat, the part # is W52-88B for an 88C/191F model and W52-82B for a 82C/180F model. I tried substituting different numbers for the 82 and 88 in the part number but was not able to find lower temp ratings in stock. You can find the 82C model in 80's honda goldwing motorcycles, 80's toyota cressida's, honda preludes, etc. The 88C model was pretty ubiquitous, you can just search for the Tama brand thermostat for a 1G through Napa. I purchased an 82C model from Napa, their part# ATM 1542903, cross referencing to a mid 80's Toyota Cressida.
Of note it appears Tama may be the OEM for some of the engine bay sensors in a 1G. https://www.tama-e.co.jp/omrop2016_180329/top.html
