DaveGS4

iTrader: (2)

Has anyone put in the aftermarket 71° TRD Thermostat for their GS400 / GS300? If so - any noticable differences?

I know mods of this type aren't readily apparent, but serve more to keep your engine cooler and better able to produce power when needed as it runs (doesn't add HP).

I'm not sure how efficient (or even what temp) the factory Lexus thermostat is... Not sure if it simply cycles open and closed, or if it meters the water level too.

http://www.toyota-trd.com/en/strt/thrmstut.html


Comments from anyone using one?

roenick7

It lets the water flow @ a lower temp, rather than the water flowing at a higher (OEM) temp. Keeps things cooler for a bit. Lexus dealership charges 88.00 to install. Steve sent me Tom's and it was the wrong one Tom's doesn't have a gs400, ONLY TRD, found out after they pulled out the old one Steve Gantz sent me my $$ back and paid for the failed install.

Good Luck

VVT-i

The factory thermostat is setting to open between 80-82 C (176-184 F). TRD open sooner for the high temp. and high RPM during racing or engine with higher RPM. I don't think it's gonna hurt anything.
You can DIY on this. Just drain the coolant from the radiator drain at the bottom of the radiator. You'll need to drain only 1/2 of a gallon because the thermostat housing is on the top part of the engine. Unless you want to completely flush the cooling system then they're 2 more drain holes on the side of each cylinder bank.
Just remove 3-12 mm nuts from the housing.
Install the new thermostat with new gasket.
On the thermostat itself you will see a little pin(nipple), make sure the pin is straight up.

MrSypher

I got the Tom's on mine.. I just put it in like 3 weeks ago.. I don't notice a difference but I guess it's working and keeping things abit cooler...

///MDex

Is it possible to run too cool with this?

I mean, I like the idea, but the engine does need to be at a certain temp to operate at prime efficiency / power.

Does a cooler engine temp mean more power? During the summer, yes, I know.

Can anyone shed light on this?

VVT-i

The TRD thermostat open sooner for the high RPM engine to keep it cooler, but I don't think it will gain anything. I think it good in the race track. It will effect emission a little bit by lowering the temp of the engine in everyday driving.
There's 3 major gases that need to be control right now, Hydrocarbons(HC),Carbon Monoxide(CO), and Oxides of Nitrogen(NOx). By lowering the engine temp will reduced the NOx, but will increases the HC and CO. The GS400 is designed for Low Emission Vechicle(LEV) and the 430 for Ultra(ULEV), if I'm not mistaking. The thermostat designed to opened around 180 or little bit more. By open it sooner will effect some of the emission and may be the engine will not reach it normal operating temp. But for our GS and the way we drive, the engine will reach the normal temp or beyond at no time..

Mean Gene

Actually, a thermostat is designed to help an engine REACH it's operating temperature faster. It remains closed until the coolant reaches the temperature setting of the thermostat at which time it opens. Once it's fully opened it's not that much restriction within the cooling system. Years ago ( uh, oh - another senior moment!! ) we would just remove the thermostat entirely to provide maximium cooling flow ( high compression V-8's with lots of camshaft ) but it would take forever to get some heat in the winter!!:eek: Not sure if that's still the case with today's HVAC automotive systems but might be something to be aware of. Lingenfelter won't go below a 160 degree thermostat in his Corvettes because of the operating range parameters of the ECU. The Lexus factory setting is 82 degrees Celsius & should close fully at 40 degrees Celsius ( 104 degrees Fahrenheit ). Emission control mentioned by VVTi is an excellent observation. Don't most of us have the "butt warmer" heated seats??

///MDex

M/G, good point.

The other side to that coin, that I learned while building up my 74 Ford Bronco (they usually had overheating problems) was that guys would install low temp thermos in them, they would open fully, then stay open, so the coolant as always moving so fast, it never had ample opportunity to exchange / loose the stored heat it contained, therefor, the temps would eventually spirial out of control.

Our solution then, was to install new, bigger, more efficinet radiators constructed from aluminum.

Two different worlds here since that 302 heated up like in 2 minutes, but thought I'd offer my spin.

MrSypher

Both you guys are the *****... I'm 100 times more knowledgeable now than I was 2 years ago thanks to you and ClubLex...
Always helpful and inciting... Thanks.

tomtnc

My post assumes that the goal here is to cool the intake charge and gain hp/tq based on the principle of colder intake charge = potentially more power.

Through past experience (i.e. often flying by the seat of my pants trying anything to gain an extra hp or two), I've found lower temp thermostats can come in conflict with ECU operating parameters. If my memory serves me correct, I had an experience where a "low-temp" thermo came in conflict with an ECU-controlled electronic cooling fan. I know very little about the Lexus ECU cooling system parameters so maybe some of the gurus here can address that issue.

Outside of cold air induction, I've found effective (and safe) modifications with regards to intake charge "cooling" to be:

1. Red Line Water Wetter. Check out the Red Line Products page for technical info. As an engineer, I can attest that the thermodynamic principles and 'claims' made by the manufacturer of this product are sound. I have used (and seen it used) it in both street/race EFI and non-EFI applications but it seems to benefit significantly modified (higher compression, forced induction) early-model vehicles with inefficient cooling systems more than anything else.

2. Phenolic Intake Spacers. Helps to reduce heat transfer from the block and heads (combustion chambers where the heat is generated) to the intake manifold (intake charge pathway). Excellent information with regards to phenolic spacers can be found on the Outlaw Engineering page.

Hope this is informative.

LexCiting

I am using the TRD Thermostat because of my Twin Turbo application on my GS. I was told that even if your stock Thermostat is rated to open at 185 degrees, it doesn't start your fans going until your engine temp reaches closer to 200 degrees. I have actually had a Lexus diagnostic gauge hooked to my car, and taken it for a chill drive, and saw that the fans did not come on until the engine temp reached almost 200 degrees. The TRD thermostat is rated at 160 degrees, so that means it will start the cooling process at around 175-180 degrees. If you don't have a aftermarket addition such as a supercharger/turbo application, it is overkill, IMHO. I was also told that if you live in an area where the temp reaches below 50 degrees (winter), then you wouldn't want to install it on a stock car, because it will keep your engine from running at its peak, or so I have been told....

Lee

MrSypher

Lee, What if you have boost and live in a place where it gets below 50??? My car is getting boosted this Spring and I already have the Aftermarket Thermostat on.. Atleast for this winter it's ok, right??

LexCiting

Yes, that would be ok. When SRT had the Lexus diagnostics tool hooked to my car during they were testing/tuning, it was amazing to see how quickly the engine got over 200 degrees during boost, and how slowly the fans took to react, and start cooling the engine. Thats why they went with the TRD Thermostat. I didn't realize everything the stock ECU tracks, and monitors (Oil Temp, Iginition degrees, Spark Plug firing, coolant temp, All kinds of fluid pressures/temp, engine adjustments, fuel adjustments, etc) I would definitely let my car warm up gradually if you are in a colder climate with a "real" winter. That way you allow everything metal to expand at a constant rate. Also think about swapping out your stock cooling fans, depending on your application.

Lee

///MDex

To what? Bigger ones? Any recommendations? Wouldn't it make more sense to lower the point at which the OEM ones activate?

Great info BTW. I wish we could see this data while driving; quite interesting.

LexCiting

I would swap them to Flowedyne fans(sp?), or some brand like that. You benefit in two ways: 1) The stock fans weigh more than aftermarket ones 2) The aftermarket fans blow more volume of air into the engine bay. SRT checked the time it took to cool the engine from 200+ degrees with both the stock, and aftermarket fans with the TRD Thermostat. The aftermarket fans cooled a lot quicker, and in less time. Personally, if I didn't have 2 turbos to cool, the stock fans would do just fine. If you look under my Twin Turbo review in the engine section, and check out the pics of my car with the hood up. You can see the two fans mounted to the radiator.

Like I said before, if you are stock, or mildly modded, I wouldn't worry about the thermostat, and definitely not aftermarket fans. But, if you are thinking about turbos/Superchargers/NOS then I would definitely think about things to keep my engine & parts cooler, such as oil cooler/tranny cooler/fuel cooler/radiator swap/intercooler/heat shielding/160 degree TRD Thermostat/aftermarket fans/changing to synthetic motor oil, etc. The list can go on, and I maybe getting off the topic....