Throttle Body Insulators

Here I will document the progress made on the throttle body insulators. Everything will be listed in reverse order so the newest news is always at the top.


     The other night I went and started testing the insulator. The first step was a spirited 10-15 minute drive around town. This warmed the car up to normal operating temperature. I then drove home and measured the temperature of the throttle body and three points on the intake manifold. You can see the points below.

     The results were as follows:

     Ambient Temperature - 50F
     Throttle Body Temperature - 122F
     Point #1 - 115F
     Point #2 - 106F
     Point #3 - 96F

     After taking my measurements I went out and drove some more to make sure the car was really at the correct temperature. I then remeasured the temperatures and got nearly the exact same numbers.

     I then installed the insulator. This was a simple process and even with taking pictures only took about 20-25 minutes. Everything sealed up just fine on the first shot. So it was time for another drive. This time I did the exact same thing. I went for an even longer drive this time though to ensure the car was fully warmed up. I then took these measurements:

     Ambient Temperature - 50F
     Throttle Body Temperature - 122F
     Point #1 - 104F
     Point #2 - 98F
     Point #3 - 89F

     Initially, I was very disappointed. After that I started thinking why didn't the temperatures drop further? I have a few ideas. First off this car is plagued with an EGR system. This recirculates hot exhaust gas back into the intake manifold almost right where point #1 is. That of course is going to add heat. Another idea is just that the engine bay is very warm. The majority of my warm up running around was done at an average of about 30 mph. This doesn't allow a lot of airflow into the engine bay. The heat soak from the hot air under the hood is also heating up the manifold. Of course there is the heat comming from the other end of the intake manifold. That inevitably will heat up the manifold fairly well. I will probably do some testing with both for kicks. The last possibility is that the insulator isn't working and heat is going right through it. This obviously isn't true as the temperature did drop.

     Now for a little hypothetical math. To get an idea of how much horsepower this has made I'm basically going to estimate to the best of my ability. In the intake manifold insulators I dropped the flange temperature 52. This returned an estimated 20 drop in intake air temperature. For the throttle body insulator I'll just use the same ratio since I have nothing else. The insulator here dropped the flange temperature 11. I'm going to guess here that the air temperature is dropping at the same ratio as before (20/52 = 2:5). This would mean that the insulator will drop the intake air temperature about 4.2. Now its known that decreasing the air temperature 5 makes it 1% more dense, thus producing 1% more power. We'r e very close to that. 4.2/5 = .84%. That is my estimate for how much power this modification will produce. Nothing amazing by far, but actually very close to what I thought it would produce initially.


     This update will encompass the progress I've made in the past few weeks. I finally got some time to get templates made for each of the common throttle bodies that are used on the E-series engines. SO I got the templates together and started drawing these things up in CAD. This is what I have come up with. There is the 45mm version on the left and the 50mm on the right.

     These designs are pretty final. The 45mm version would be used on the 3E-E and 2nd gen 5E-FE. The 50mm version would be used on the 4E-FTE, 1st gen 5E-FE and 5E-FHE. Fairly straight forward. If you have done the 1st gen 5E-FE throttle body stop onto your 3E-E you would then use the 1st gen 5E-FE insulator.

     But, theres more. The other day I decided to actually go ahead and make one of these insulators for testing. This 45mm version will be fitted to my 1996 Tercel and testing will be done.

     If you followed my testing done on the intake manifold insulators I'll be doing less testing on the throttle body insulators. The equipment I have for measuring horsepower increases isn't the most accurate measuring device in the world and I think that it would have a hard time differentiating between the small increase I plan on these making. What I will be doing as far as testing will be measuring intake manifold temperatures in a couple places to see what kind of temperature drop this insulator will provide. But, that is for another update. Here is a picture of the 45mm prototype.


     This modification was bought up during the intake manifold insulators project. So now that it is done I can get some time to work on this. I don't expect amazing results from this, but if its any good at all it should be worth the price, which should be fairly low.

     These insulators will differ some from the intake manifold insulators. First off they will be made of a different plastic. This new plastic can not tolerate quite as high heat. However, there is no need to worry, it will hold up more than adequately. The throttle body does not get nearly as hot as the head. This in turn lowers the material cost considerably. The second change is that these insulators will be a little thinner than the intake manifold insulators. This is to accomidate the shorter studs and bolts that hold the throttle body to the intake manifold. Again, I am trying to make this modification a bolt on type. You know, something you can just take an hour or so and do with an afternoon's worth of time.

     At this point there is also the idea of developing throttle body spacers as well. These differ from the throttle body insulators in that they are much thicker. In fact they will most likely be over one inch thick. These have two benefits. First, they will block almost all heat radiated from the throttle body. Second, they increase the volume of the intake manifold's plenum. Having a larger plenum tends to shift the powerband higher into the rpm range and thus frees up horsepower at higher rpms. There are drawbacks to this however. The factory studs would need to be replaced as well as using new bolts. Theres also the problem of the throttle cable mount and moving it an equal distance. Theres also the possibility of problems with vacuum tube length. All this will be looked into should I decide it will be worth it to go this route.

     So first off, the throttle body insulators will be made for at least the 3E-E and 2nd gen 5E-FE. Those are the engines I have avaliable to myself, and I will be using them on my cars. If there is interest in making them for the other E-series engines I will definitly look into it. Also, if there is further interest in the throttle body spacers I will start looking into that as well. At this point I have already ordered and recieved material for the throttle body insulators, and hopefully I'll have time to make a prototype soon.

     If you have any questions, comments or anything email me at

     And of course, we couldn't leave without at least one picture! So here it is... the material. I selected black as you will actually be able to see this insulator and it came in a couple colors. It should blend in nicely for a stealth mod... I really didn't want anything that would stick out.