REBOCK140

I have a 1991 mazda RX7 convertible Non Turbo in mint condition with a racing beat header, presilencer, catback system. How much horse power can I expect to gain if I install a custom made cold air intake???

dean23

not a whole lot. its more depending on how the weather is... i think of it like this. youir engine bay is almost always the same temp, but the outside air changes every day. in the summer when air is hotter, you wont get much of a difference, unless traveling at high speeds, but even then the charge temp doesnt drop that dramatically. in the fall when air temp is cooler, the charge will be more dense, creating more hp. so its not going to be a set number. theres way to many variables to consider.

Evil Aviator

See the above post, plus...

The stock intake system already pulls in ambient air. The only way to improve on the stock system is to decrease pressure, not temperature. Pressure can be improved some by simply installing a drop-in high-flow air filter (I recommend K&N). It can also be improved further by installing a custom intake tract. The first part of the tract is commonly called a Cold Air Intake (CAI), which is rarely designed properly. If you really want to reduce pressure, you would need to install a rather expensive racing individual throttle body (ITB) system and custom manifold. And FYI, porting and/or polishing or "upgrading" the throttle body to a larger one isn't going to do jack for a street car.

The HP gain associated with upgrading intake components depends on the car's starting HP and components, and the gain is based on many factors, not a fixed number. That is why parts vendors always say "up to x amount of horsepower", because if they install the item on an 800hp engine it may yield an increase of 20hp, while that same part would only yield 1hp on a 100hp engine.

To answer your question, a poorly-designed CAI will usually reduce your car's peak hp by about 3-5hp. A well-designed CAI will add about 2-5 peak hp.

"Mint" condition means exactly like new, in original condition, unmodified, and uncirculated (absolutely no wear on any part). Sorry, your car is hardly mint.

REBOCK140

Well excuse me. I meant like new condition. Im sure that it looks nicer than yours does. Look at my profile there is a picture of it. It was just repainted a black metallic.

texFCturboII

iTrader: (17)

wow, what a jackass reply! These people are giving you valid information and you respond by saying your seven is better than theirs!!! Get yourself a stand-alone ECU so you can get rid of your AFM, ta-da! Less intake resistance, more powa! Then worry about a CAI, regardless unless it's done properly (rarely is) it's gonna do more harm then good.

Evil Aviator

There were no new 2Gen RX-7's painted black metallic. Therefore, your car is NOT like new condition. Strike two.

As for which car looks nicer than another, that is really more of a personal preference. I think it is good that each car owner has a little different opinion of what looks good. However, everybody knows that black is the best color.

ericgrau

iTrader: (1)

6-7 HP. Based on both someone's real world comments and my own estimates (below). You'd get more after other upgrades, since it is a percentage of your current power.

Power is proportional to air density. Air density is inversely proportional to absolute temperature. Absolute air temperature, Rankin, is temp in degrees fahrenheit + 460 (absolute zero is -460F). So if you go from 120F to 80F, that's 580R to 540R, or a 7.5% increase in power.

If you mean a cone intake, you'll gain a couple horsepower but probably lose more from the warmer air it's sucking in.

Josh13B

The stock box on a RX7 works against the air inflow, any (good) new air filter / CAI would show an increase in HP.

It will only be a few percent, but it will mean that there is less restrictions on the air coming in, and more air will be able to enter the engine.

NZConvertible

Drop-in filters are a waste of money. The pressure drop though a clean stock paper filter is so small that even if a "performance" filter substantially reduced it, the actually increase in performance would be practically unmeasurable. Nearly all the pressure drop through the airbox if caused by the box itself, not the filter. Plus it takes ~10 years of reusing the filter to make it cheaper than buying stock replacements.

Evil Aviator

Ah yes, NZ living in turbo land yet again, lol. The original poster has stock NA engine, in which case a drop-in air filter will work well, and the performance increase will be measurable (but not by much). However, you are correct with respect to the TII engine, which will have nearly 50% more airflow volume through the filter.

0verb00st

My GTU is black, didnt it come black out of the factory?

On a different note, Corksport has custom intake piping and filters.

Evil Aviator

If your GTU has a paint code of PZ, then it came Brilliant Black (non-metallic gloss black on a white primer) out of the factory. If it has a different paint code, then it was repainted. There was no metallic black.

I guess you also know that black is the best color.

MmSadda

iTrader: (2)

Actually, I believe it is common knowledge that paint code K8 is the best color; it's the darker S4 silver (gun-smoke metallic)

MmSadda

iTrader: (2)

oh, and Evil Aviator knows his ****. he's right. don't argue.

except about the best paint color

iceblue

lol I don't even argue with him and I like to argue you learn more.

but today is a rare day. White is the best color! All sports cars should be white or race sticker car. Oh but with black interior! mmmmmmm sexi

Don't forget the mad uber cool noise you get from that fabulous fairest metal NOPI intake kit. That noise has to be some type of HP.

dean23 - I like you I have the same steering wheel in my Miata drift car.

brokenRED7

white FC ftw

V8slayer

ahh man, dont come on the forum ask advice for a stupid question and then dog him for giving you good info on it he was just trying to help. do ask a question if you are not going to like the answer

FirebirdSlayer666

iTrader: (3)

Brilliant Black, Tornado Silver Metallic, Formula White(with black trim) best colors in that order LOL. I was going to build a cold air box for my 89 GXL but decided I'm just going to buy a drop in K&N and save myself the hassle. The FC is supposed to be my lazy car(daily driver) and I'm not supposed to put so much time into it but I can't help it LOL

NZConvertible

That makes no sense. The NA and airboxes are identical, but the Turbo engine flows a lot more. That means the filter causes less pressure drop on an NA than on a Turbo, and hence any improvement will be proportionally smaller. Why would a lack of turbo will make a drop-in filter work better?

Anybody considering a drop in filter should read this first:

http://autospeed.drive.com.au/cms/A_2232/article.html

iceblue

Hmm well I have some personal documented evidence that showed quite a bit of improvement with a drop in filter. boosted application as well.

All these articals are so poorly tested and application specific they should be read with a bucker of sea salt.

Evil Aviator

No, I think that article trumps all. Using pure logic, the fact that some guy found no measurable pressure difference between a dirty and clean air filter on his Toyota proves that a drop-in K&N air filter offers absolutetly no improvement for an RX-7. My bad.

It does improve the flow a bit, but at higher airflow levels the NA-sized intake tract really dosn't work that well, and the easily-replaced TID isn't designed very well.

Er, I mean it is all part of your imagination, and it actually does no good. Didn't you read the article? You are getting sleeeeepyyyy.... when you awake you will replace your actual experience with teh intahnet... and black is the best color.... you are getting sleeeeepyyyy.... all your base are belong to us....

NZConvertible

So post it up. Make sure you describe the test procedure, measuring instrument, before an after readings, etc.

Actually that website has posted five or six articles that tested pressure drops through various points in the intake system of a variety of engines, with testing carried out before and after modifications to the system.

Testing with done with either a water manometer or a magnehelic pressure gauge, both very accurate test instruments. Measurements were taken at the same rpm (usually redline) at WOT. Typically the pressure drop through the filter was around 1"H2O, and in every single case this was a small fraction of the total pressure drop through the system.

For example, the total pressure drop from the intake to the TB on a 1.6L MX-5 was 17"H2O, with only 1.2"H2O pressure drop through the filter (~7%). On a WRX, the total pressure drop from the intake to the turbo inlet was 50"H2O, with only 1"H2O pressure drop through the filter (~2%).

RotaMan99

I found this a couple weeks ago on NoPistons. Measuring the restriction of a FRAM air filter and without the filter.

http://www.nopistons.com/forums/inde...1&hl=manometer

Even though there are variables that could make this test not so great, its still interesting. Our stock intake system is actually not that bad. I found another thread, I gata find it again about our AFM's pressure drop.