I took these screenshots from an old ISF manual (our flap opens at 2800rpm). It seems that the purpose of this dual-stage intake is to minimize noise at low rpm.

 

For those who are in Canada/Ontario - I bought a Doorman vacuum cap kit, 5 pieces from Amazon, for $15; if you need a couple of caps, drop me a PM with address and I will drop them into an envelope for you. Free for my IS500 buddy. Coming on Wednesday so I plan to install them same day and will report back. Sounds like a no brainer mod.

 

Put the caps on, indeed now the noise is uniform across rev range at the bottom and a lot better experience.

 

Any negatives to having the flap open all the time? Running hotter? lower mpg?

 

To be honest, I think it’s inconclusive. I’ve seen posts were nothing happened and posts where the performance was affected. It’s one of those try it out and see scenarios.

 

0 impact in daily driving.

 

This "Mod" is as old as the hills - first tried out back in 2008 in the ISF. And no, performance does not improve, in fact it's a negative:

https://www.clublexus.com/forums/is-...ntake-mod.html

Lou

 

You keep bring uo this ancient post where one user last 2 tenths and 2mph in the 1/8th mile drag race. There are so many factors that go into a drag race and heat soak could absolutely be a factor. Every other user in that thread posted that the car felt smoother and that the audio being more consistent was worth the mod.

That was my biggest reason for it, the intake being silent then experiencing the sound flipping on like a light switch once you cleared a specific RPM was infuriating. Now the sound of the engine is directly related to my right foot.

There's no reason for peoole not to give it a try for themselves as its a simple vacuum cap to try it. If they dont like it switch it back. No reason to try and scare them away from giving it a shot based on one ancient post.

 

Scare users away Doing that mode is not dangerous, never said it was. It's just, IMHO, sort of silly when performance is reduced. However, if you like it - More Power to you - NJOY😋

Lou

 

To clarify, the sole purpose of this modification is sound. It offers no performance enhancements or decreases.
Nothing changes but the sound, correct?

 

If there's any power loss at all it's below 2,800rpm as that's when the valve just opens anyway. How much performance driving are you doing under 2,800 rpm anyway?

 

I did the plug blockoff and the sound at lowend is improved.
Didn't notice a single bit of change to the feel/response. Nothing at all.

 

unplugged mine and i like the sound!

 

Yeah, that's what it's about really...just a "better sound" at the lower RPM before
"trap door" was opened. When I get mine I'll try it out. Thinking I'll like it too.

 

I'm glad I found this thread, looks like I have sizable targeted audience here.

Why bother to go through all of these mods. I have these specialty pills that you can drop in the gas tank which will improve your vehicle's horsepower and its fuel economy. It'll sound awesome, too!