Throttle Body

[silverstreak]

Good morning all beautiful day up here in the northeast. On to my question, has anyone seen or heard if there is an over bored throttle body for our cars? I want to get somthing on the intake side of things to compliment my cat back. I'm not overly impressed with the intake options so far, and I'm not sure the K&N filter would offer that much less restriction than stock.

[btavish]

There is guy on the interwebs that offers this service, I stumbled onto the website awhile back and he definitely knows what he is doing and the pricing wasn't bad. Only problem is down time.

[91cavgt]

Here is the big question. Is the stock throttle body restrictive?

I don't think it is and here is why. The 1.2L motor in the Mirage is designed to be fuel efficient. It is also a very small motor that has very good low end torque for it's size. This tells me that the camshaft is designed for good, low end flow and efficiency. So I am willing to bet that the biggest restriction in these cars is not the exhaust, nor the intake, nor the throttle body, nor the exhaust manifold but rather the cam shaft. Changing any of the other parts first will only yield very small power increases.

[Ares]

The point in changing small easy parts is that they are small and easy. If one could gain a total of 10hp with replacing 5 parts, I think it's worth it.

The better question here is: why not start with what's available? Take the stock airbox out and put a filter and straight tube. I also think that changing the tube after the MAF into the TB needs to be changed into something smoother.

[Daox]

Its easy to measure if the throttle body is a restriction or not, you just need a vacuum gauge. If it reads zero vacuum at WOT and max horsepower, you do not have a restriction. If it reads anything above zero, you have a restriction in the intake system in front of where you plugged the gauge into. As you keep moving the gauge forward (toward the intake inlet), you can measure how much restriction each piece is making. Then, you replace the most restrictive part first (largest gain) and see how it effects things by testing again. Unless you do this, you're just guessing.

[91cavgt]

Its easy to measure if the throttle body is a restriction or not, you just need a vacuum gauge. If it reads zero vacuum at WOT and max horsepower, you do not have a restriction. If it reads anything above zero, you have a restriction in the intake system in front of where you plugged the gauge into. As you keep moving the gauge forward (toward the intake inlet), you can measure how much restriction each piece is making. Then, you replace the most restrictive part first (largest gain) and see how it effects things by testing again. Unless you do this, you're just guessing.

Exactly!

[silverstreak]

Some good points have been brought up here. I was really just going by my past experience with replacing them on a couple of my cars. I also saw a spacer for our throttle body on eBay. Any thoughts on that?

[Daox]

Won't do anything. If the OEM could gain a few hp by spacing the intake manifold out another 1/4", they'd have done it.

[91cavgt]

Some good points have been brought up here. I was really just going by my past experience with replacing them on a couple of my cars. I also saw a spacer for our throttle body on eBay. Any thoughts on that?

The point of a throttle body spacer is to increase the intake manifold volume. This in turn should help with low end torque, ever so slightly. However, the low end torque increase is VERY minimal. It's not enough to feel.

[Ares]

The point of a throttle body spacer is to increase the intake manifold volume. This in turn should help with low end torque, ever so slightly. However, the low end torque increase is VERY minimal. It's not enough to feel.

Like I have previously stated: minimal and no gain is different. Our cars need minimal.

But that's just my thinking.

One of these days, I'll benchmark my car, then purchase a whole lot of these little mods, and dyno again.