So I was in the market for an air filter and I go to a racing shop next to my house and the guy tells me not to get a market filter (i.e. K&N, AEM) he says its better to get a custom filter and find a way to fit it, what do you think is better putting the custom air filter in and having to find a way to put it because of stuff in the way?

 

There's nothing wrong with the K&N products. The biggest weakness with the 7's air intake is the snorkle and air box. They're way too restrictive. A high-flo filter in the stock air box will make for an improvement but your best bet is to buy/build a cold air box. I'm in the middle of doing that with a K&N RU-2820 and a custom adaptor that I'm having made locally. It'll look a lot like this...

http://cgi.ebay.com/ebaymotors/ws/eB...tem=1876627608

The air box itself will be fabbed out of Home Depot's finest.

A custom filter sounds expensive...

 

what you went to was a honda rice shop... nobody makes $400 intake pipes for rx7's so don't worry about what he said.. just buy a K&N filter and stick it on the airflow meter.

if you have an 86-88 you'll also need an AFM adaptor. you can get them off the net for around $25

 

I found me a nice APC air filter, for like 20 or was it 30 bucks at advancde autoparts..

 

I see, so that box that says Mazda is an air box, if I removed that and fit on the K&N would that work?

 

What would be best is to have the filter fed with cold air only. If you put the K&N on the AFM and just left you'd have lots of airflow, but it would all be hot air from the engine bay. Not much of an improvement.


Check these out:

https://www.rx7club.com/forum/showth...hreadid=101026

http://www.autospeed.com/A_0779/page1.html

 

So what youre saying is Im better off getting a cool air intake?

 

yep but your going to have to make one your self, there are only airboxes in the market for out cars, which does really get cold air just keeps the hot air out, alittle, if you want to fab a CAI setup then most likey you will have to cut the frame...

 

Or the hood.

 

The funny thing is, people who say "you don't gain anything putting on a cone with all that hot air" have never done so. EVERY RX-7 I've put a cone on (and that's quite a lot, turbo and non-turbo) have made a HUGE improvement going to a cone intake, especially on the top part of the power band.

It's really the best bang-for-the-buck mod you can do.

The cone gets you 90% of the performance, the cold air business gets you the last 10%. Kill yourself all day long making crazy cold air setups - they really don't make as big of a difference as you would think. If nothing else, just build a shield to keep the hot air away from the intake and make a duct to help draw fresh air to the cone, then call it a day.

Dale

 

If your underbonnet temp is 40degC (and it can get much higher) and ambient is 20degC (a mild day), then the underbonnet air is 7% less dense than the outside air. That means 7% less air mass (and hence 7% less oxygen) is entering your engine. That's a very significant difference in the potential of the engine. With a proper cold air feed that difference is measured by the ECU and the result is more power. It's simple physics.
BTW, the improvement from a cold air intake is notoriously difficult to measure accurately on a dyno. For starters, most dyno runs are done with the bonnet up, which will lower the temps seen by an unshielded pod filter, and heat soak is a common problem because of the lack of airflow compared to driving on the road. Never trust dyno results of cold air intakes, only road tests.

 

I agree with NZ...can't really argue with the laws of physics. I'm not a big dyno fan for that exact reason, just because you only make X amount of hp and tq on the rollers doesn't mean that's all you have. Look at the Audi R8 race cars...they reportedly make an additional 15 (or was it higher) hp with the intake design they have when they reach speed (of course that speed is 150mph but hey it's more power)...now that doesn't count for the cold air. Not to mention how can you test the effectiveness of something that works while in motion...if it's sitting still?