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DIY Stock Intake Mod

39859 Views 90 Replies 34 Participants Last post by  foreverkidd
Hi Guys,

Well, I got to thinking about the stock dual stage intake and figuring out a way to keep fender side intake opening open all the time. In case you didn't know, the fender side intake opening is closed until around 3600rpm, which is when it opens up, thus resulting in the now infamous and much beloved "IS-F Roar". As you can see from the picture below, all I did was just pull off the vacuum hose from the actuator and plug off the other end with a vacuum cap. Now the "IS-F Roar" comes on around the 2300rpm, and to me atleast, there seems to be a bit more power down low...which makes since because now the engine can breathe a bit better down low with both intake opening being open all the time. The only downside would be if this throws off the air/fuel ratio's from stock. I don't think it will drastically, but I'm not sure. Anyway, try it out and let me know what you guys think. Oh yeah, no check engine light either! Have fun...Darshana S...

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no VAC plug necessary

In other news, the vac plug is not necssary at all. You can simply unplug the solenoid. Since it is not a critical system, there is no current sense on it. Works great :p

After looking at the intake system it is my conclusion that the factory macroni pipe is not restrictive at all. Even the damping mechanism is very minimal. I think I did figure out what can be improved...and that is the airbox/ram air. I will keep you gys posted and start a thread once I get further along. Feels good to get into the engine bay again and tinker

I would highly advise against this modification. The problem with the IS-F is not down low (where I have reached sixty in 4.2 seconds numerous times) and where there is an abundance of power on tap early but rather after 5,000 rpm's where we have seen torque curves drop off significantly, and where both intakes are fully open. Voiding your warranty to hear the often talked about "whoop" 1,000 rpm's sooner is simply idiotic, and something I would expect from Chevy iroc or Ford mustang owners!

IROC- Itailian Retards Out Cruising
you are not going to void a warrantee for a system that is not in the "metered" airflow path. This is all prefilter airbox modifications. I took the whole thing apart last night and this is nothing worse than what an open element filter will do.

The fact of the matter is that this is exactly the type of thing that Lexus puts in to preserve luxury. Its just a trap door that opens the filter to the engine bay (not even the fender.)

What is your technical argument?

I thought about doing that initally also, but I wasn't sure if it would trigger a check engine light so I decided to "fool" the system into thinking that nothing was disconnected. But I don't know too much the stock ECU (I don't think anyone does) to know whether that stock airbox plug does more than just control the secondarly intake flap...hopefully it doesn't also have some part to play in the air fuel ratios?? I doubt it, but I was just playing it safe by doing the vacuum cap mod rather than disconnecting the connector. But anyway, do you notice a difference in the throttle response also?...Darshana S...
Throttle response, possibly. The only to way to know is to do a few runs on the Gtech and average the findings. The A/F ratios are purely calculated based on the hot wire sensor and MAF in the intake tube just after the filter. you could not base anything off of an inprecise flap opening and closing on the front side of the filter. I will post pics later.
OK I should have a cross for the filter in a dry high flow drop in from Amsoil. I will confirm next week.
great Dean, keep us posted, I will take pics of the stock airbox fitment when I get my amsoil dry filter.
Guys I did it this morning and I'm never going back to normal, love what it did to the car, as far as I'm concerned they should have sold us the cars this way, and yes no engine light yet, hope never.
Thanks a million Supraman16.
Just out of curiosity, how did you come up with the idea.
People you have to try it, it took me 20 sec.
If you read my comments you can just disconnect the solenoid connector and it will achieve the same thing. :) No tape required

unplug the connector on this guy...done.
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Hi Guys,
I'm glad you like this mod. I've had it done now since I originally posted up this thread and I have yet to find a negative effect from it. Gas milage is the same, the sound is incredible...even more so in combination with the JoeZ exhaust I recently got, and more importantly, a bit more noticible power in the low end. However, the only thing I have found out and want to advise everyone one against is getting a drop in air filter, like a K&N filter...DON'T DO IT...with or without this mod! I had the K&N filter and it felt like it was making more power initially, but then it went away...likely when then ECU adjusted to it and the MAF got contaminated with the air filter oil. I started having really poor gas mileage and this promted me to put back the stock filter (along with the fact there was a thread on CL about how the K&N filter as causing problems to other members IS-F's). But yeah, I've had this mod for awhile and still nothing bad that I have experienced...Darshana S...
PS. I have mine done the original way...with the vacuum cap rather than disconnecting the solinoid. I didn't want any water or debris getting into the open connectors.
Yeah teh K&N and MAF do not get along. That is why the amsoil filter was my choice. Completely dry and easy to clean. So far just turn 8K on the clock and no looking back.

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