I think this has been discussed in the past, but I didn't see any threads titled with this fix. Anyhow, the Evo 10 MAF hotwire is apparently very sensitive to small amounts of airflow and probably air temperature differences. For those with exposed element (cone) air filters, crappy idle during coast down and when the cooling fans are running (air conditioning, stuck in traffic) is likely due, in-part, to air flow/temperature fluctuations on the MAF hotwire. A good size shield that blocks airflow from the radiator area can make a very big improvement in idle stability.

 

That is the case for the 2008 models. The 2010's don't seem to exhibit the same issue.

 

We include one in our intake kit for the EVO X.

http://www.amsperformance.com/cart/A...-Polished.html

 

I have exactly same trouble. my car is 2008 Evo X GSR and using exposed cone. It has a heat protect board, but still unstable idle ( randomly popping noise and rpm needle swings. )

 

i think the heat shield is a great idea anyway. I am running no more MAf and we still useing heat shield at the cone.

 

from my experience it is pointless to fit all those screens. It's much better to buy AEM box like this http://www.aemintakes.com/search/pro...x?Prod=21-678C , it helped me stabilize idle on several cars and reduce intake temperatures.

 

I planned on getting one for my Primo 3.5" intake but honestly, I have not had any idle issues at all, even with a ported head and kelford -b cams, 1680cc injectors, the car seems to idle just dandy, even with the AC on and 100°F+ outside. My car is a 2008 too, I have the stock air snorkel set to fit over/towards it but I wonder if having a relocated BOV helps or acts slightly as a heat shield since it is right in the path of that fan air.

 

Not really an option on cars that have maxed out the stock maf housing, that AEM one would be maxed out on my setup too.

 

AMS started including them years ago once there were complaints of this. Old news.

 

Interesting. A cardboard shield made all the difference in the world on 3dman1's Evo. Same intake as you. Stock snorkel is not attached though. The unstable idle only happens when the radiator fans kick in, e.g., if he turns on the AC when the motor is cold, idle is ok.

 

Ya I have been shocked how nice it is, even in heavy traffic and hot hot hot days. I've been having some other unrelated issues though, I'll probably post about them once I get some testing time in.

 

I used Aem intake box and fited it with ETS 3.5 inch maf housing with velocity stack. Fits perfectly, will make pictures tommorow.

 

Huh? It's the wiring that's sensitive to fluctuations in heat? First I've heard of that... I thought it was hot air being blown directly into the intake.

My intake is shoved down into the front bumper and I have never experienced this, which makes me think the sensitive wire thing is not the case.

The wire itself is copper and the resistance of copper is nowhere near as sensitive to temperature changes as metals like platinum, which is used in thermocouples/resistance temperature detectors.

Anyways, shove the filter into the bumper and you'll be just fine. Just don't go into water >1ft deep

 

my 2010 does it with a cobb SF. had to use the stock snorkle thing.

 

It is a hot wire MAF. He is saying the air is being blown into the intake and over the MAF metering device which is a hot wire that senses change in temperature to calculate airflow.