Contour Enthusiasts Group Archives Forums Modifications Duratec Performance No more IMRC for me! (LONG)

Reposted from NECO:

I had a ton of important things to do today... Register for classes, return my MAF optimizer, change the oil in the Corolla, get my wheels rebalanced, take my car in for a paint problem, and get started on a term paper.

Well... I just said ph*ck it, and I started doing something pretty wild instead. I decided that I didn't like having secondary butterflies anymore... so out of nowhere, I started unbolting my upper intake manifold. Keep in mind, that I had NEVER removed it before. Well, it was a lot easier than I thought it would be.... and I didn't break anything.

So there was the lower... I figured that if I was really careful, I could perform this surgery 'in situ' and just remove the two screws holding each butterfly on. Yeah RIGHT. I got 5 or 6 of the twelve screws out and stripped the rest. OK... actually, I only got ONE off and stripped two. Then my friend stopped by, took a few more out and finished stripping the rest for me. Great.

So, I realized that I was going to have to drill the screws out. In order to do that, I would HAVE to remove the lower manifold. Good idea anyway because the lower was mated to the head horribly... it was off by about 2mm, so there was a huge lip in the airflow to heads. That could have been costing me 3-5hp ALONE.

I really didn't feel like removing the fuel rail, so it came off attatched to the lower (and YES, it was the silky-smooth big-bore LIM for late-model SVT's). I squirted some gasoline around when I undid the fuel hose, but removing the lower was otherwise easy except for one wiring harness that went toward the front of the car. My car is so damn low that I could not get my head underneath the car to see where it went. It was the only thing holding the lower in place at that point so I just rested the lower on the front valve cover and went to work. (Yes, I probably should have just removed the fuel rail). I covered the intake ports on the heads with a clean garbage bag and a towel and started drilling. Once I had all the screws drilled out, some dark clouds rolled in and it started thundering. I have a steep driveway, so there was no way that I could push my car into the garage. I closed the hood and my friend, who was being as helpful as someone who doesn't know much about cars could be, helped me cover the car with a tarp, just in case things got really nasty out. (They sure did!)

At that point, I decided it would be a good time to sand and polish the insides of my stock upper as well as I could. Well, once the upper was de-gunked, grinded, sanded, and washed, the rain had stopped and I went back to work. I found that I could leave the IMRC system intact if I only removed the rods and butterflies, but left the rest of the assembly in place. The rod on the front bank has to be completely removed (and have the hole plugged with something), while you should to leave a small stub of the rod on the rear bank in place so the IMRC mechanism can still open and close under the same tension as before. So far, I haven't had a check engine light in three driving cycles.

So anyway... then I put everything back together... which took a lot less time than taking everything apart. I reused all the old gaskets because I'm a cheap lazy *******. Plus, they were in really good shape, since my car is still pretty new.

Driving impressions:

Low-end torque loss was not an issue for me. With an ATX, the torque converter slips a lot below 2200rpms. The more torque you have, the more your torque converter will tend to slip. Around town, my car felt as quick as ever. Throttle response actually seemed better to me. The only time I noticed that my low-end was lacking was when I powerbraked my car and launched. I could barely chirp my front tires, while they used to squeel a lot more (it could just be my Toyo T1-S tires liking the warmer weather). Either way, I don't think it made me any slower, because I just hooked up faster than usual and my car didn't bog down from 2500-3500rpm like it used to. And above 4000rpm, the top-end improvement was very noticable. Butt-dyno says 8-10hp. As an added bonus, the car has louder deeper idle now. The intake sounds amazing too. At low RPMs, it sounds just like it normally did above 3500, except lower and deeper.

(Pictures will be posted tomorrow... they're on my friend's digital camera at the moment.)

Good job, Frank. Let's see the pics!

NECO Thread **updated with pictures**

Clicky for some pictures.

So far it has been 210 CEL-free miles. Suprisingly, power and throttle response from idle to redline feels markedly improved.

Before I go recommending this to everyone I know, I would like to get some input from other people who have done this.... not just people with pinned secondaries or stuck-open secondaries, but members who have removed them the correct way as not to cause an error code and potentially hurt performance.

So far, there is NOTHING I don't like about having them removed. I can't believe I got such nice gains basically for free. Even my gas mileage is good. (click the link MastaMoon posted for more details).

Mine have been out for a year. I like it all around... Especially now with the dual exhaust on the car...

will pinning your 2ndaries throw a cel / error code? i was gonna do this tomorrow night...

Sure will...

geez anything to keep from starting that term paper huh

Thanks for the conversation and information. I plan on removing my butterflies this weekend and now I may remove the rods as well. I am still unclear on how to plug the holes and which holes to plug. I read the NECO post and I got alot of insight, but I still feel a bit unclear. I will change the plugs then too. They will be fully exposed, so why the hell not.

2 weeks, no codes...