Modified Stock Air box and had some interesting results...
 

1994 touring. Performance wise its all stock. I have some interior effects, stereo, boost gauge and water temp. Next week gettting a downpipe. Ok.


I removed my stock intake today and cut a 3 X 6 hole in the bottom of the box. I removed the foamy stuff near the radiator edge. Then I removed the plastic that is in the nose of the car where the oval opening for the radiator is (this plastic blocks airflow from getting under the hood). I put the box back together and drive it. I am now getting 1 lb extra boost on my gauge and my engine runs cooler when driving highway. Usually when driving my car is around 1/2 way, if I had my fan on it may be slightly below half. Now since I mod my airbox when the car is moving its always below half way. I swear I am not imagining this, What are your thoughts on this?

What does your butt dyno say? Also, I assume you are using a K&N drop in right? Did you have the stock paper filter before you cut holes?

I have the K&N drop in w/o any holes in the box. I can't notice any difference between paper and K&N. So, I am curious to see if you think it's worth it?

I did not dyno the car. I am basing it on my boost gauge. I definately shows 1lb increase in boost. Also, I am still using the stock paper filter. The K & N Dyno's at 1-2 HP difference from what I read. Not a big difference.

Re: Modified Stock Air box and had some interesting results...
 

I was thinkin about doing this mod, however i was wondering what is this plastic that you took out? I thought that it was better if you close all the holes around the radiator so that the air has to go through radiator and not around it.

The best way to eplain it, if you are facing the nose of your car and you see the front bumper you will see the opening for the radiator, its a long oval opening between the places where the fog lights go. Now you will see on each side you have a black piecs of plastic, kinda shaped like a wedge. I guess its like 6 or 7 inches by 5 or 6 , kinda odd shaped. I removed the one on the left of the car. that lets a ton of air under the hood. There is no way that the air is going to get hot from the radiator when you are moving.

I've removed the plastic nose pieces too, and I have modded the airbox, mainly per the Robinette instructions. In cool weather conditions, I was spiking past 12, sometimes 13 psi and hitting fuel cut off after this mod. I have a downpipe. It seems that my ECU eventually learned a few things and has gradually compensated for the extra boost, though I still show an 11-8-11 pattern all the time now.

Yeah, the ass-dyno says it is a noticeable difference, hell just the sound of the rush of air into the box is pretty cool! Having these mods with the automatic tranny is pretty wild at times....once past that initial "huh?" that happens when you stomp the gas, pretty much all hell breaks loose....just keep that go-pedal mashed and let the car take care of itself and it is a FUN ride! The boost comes up, falls for just a sec, and comes back HARD and just stays on hard until you back off the gas.....fun, fun, fun!

Remember that the stock temp guage has no bearing on reality. It is middle or overheat only! I cut some holes in the air box when I had the stock one and ran some pips from the front of the car into the box and seemed to run cooler.

I disagree. I do agree that it is not good enough to use as your only gauge, but I can tell you that mine does react differently depending on how hot it is, etc. When I am idling, I go to 1/2 mark, when I am on highway I go below 1/2 mark. I had a problem once and my temp went 3/4 of the way up. The problem is you have NO time to react when it starts to rise. I have an autometer also.

what does the autometer water temp say...is it cooler simce the airbox mod?

you've convinced me.........im gonna go do that airbox mod now :D

I just love the line "once past the intial "huh?"" Only an auto owner could fully appreciate the "huh?" factor. I'm a manual owner, and just the thought of it cracks me up.

Those plastic pieces force the air through the radiator. If you remove them the air goes around taking the path of least resistance, leave the plastic pieces there, Mazda put them there for just that reason. The air box mod sounds good though.

just a point to ponder upon: the stock setup of the rx7 allows only air from the radiator into the air box. the air that comes out of the radiator is really hot. at least on my rx7 it is. why is that? why did mazda design it that way?

that rectangular plastic thing that connects the radiator and the air box, if you remove it, you can increase your boost by 1psi aswell. i had that setup untill recently when i purchased the apexi intake. but my car was completely stock, except for a superdragger exhaust, and i was seeing a 12-10-12 pattern with that plastic removed.

Que? Do you mean the intercooler? The stock setup has a scoop in the nose that feeds air up into the plastic intercooler/airbox deal. The crossover that is in the front top on a stock car feeds the air box but it comes in from the same spot. No air from the Rad goes into the stock air box.

:D

It's quite unique, but is really only bad from a dead stop.
From ANY sort of a rolling start there IS something magical about just stomping one pedal to the floor and holding it there.....