Midpipe question
 

I am running a downpipe,stock cat ,and rb catback with my airpump.I would like the extra hp that a midpipe will supply,but i dont want the gas smell.Can i keep my stock airpump with a midpipe? would the gas smell be less noticable?

the cat is what filters out the nasty exhaust smell. remove it and it will smell badly no matter what.

Thanks, i had hoped that more air forced into the midpipe might lessen the gas smell,no midpipe for me.

Yup, a midpipe will definitely smell things up. A nice high-flow cat should give you similar power gains and keep the fumes down.

metallic substrate cat in a mid pipe

Just had my Random Tech. 5" dia. stainless substrate "very high flow" cat installed. I had a mid-pipe and, yes, it smelled like a 50s/60s car! Now it smells like a cat equipped car (kind of an "ash" smell ;-). No power loss that I can discern. Will do sound tests tomorrow (I have readings with the mid-pipe in place).

The Random Tech cat is very well made - all stainless, not really thin wall. I'll post pics. tomorrow if you don't mind me "hijacking" your thread.

and really tho how many people care about the smell

If u move forward the smell wouldn't be that bad

any over boost problems with the midpipe in at all?

do you have to run the airpump with a hi flo cat?

I have gotten used to the smell. But my wife recenty rode in my car and she said that her eyes were watering:D

For the cat to function correctly, you need the secondary air supply. I'm guessing you don't have to pass emissions if you were running a mid-pipe...


Hehe, that sounds familiar! My eyes teared up and my nose burned every time I had to sit on the grid in the racecar. If I just sat in the car with it running for any period of time, I smelled like gas for the rest of the day! ;)

so what are you guys using in terms of boost control whom also run midpipes? right now I just have a power FC and I dont have the midpipe installed yet so

port the wastegate and get a boost controller, got mines done and i;m luvin it

First, no I never had loss of control of the boost with the midpipe, though the car always either had the PFS PMS or now the Apex'I PFC. You would probably have to adjust the duty cycle on the PFC if you went from the stock cat to a mid-pipe or the "very high flow" Random cat, but it would probably also depend on what cat. back system you have. My wastegate is not ported.

Once again, I have a stainless downpipe, had a midpipe, now the Random 5" dia. cat, and an HKS Superdragger cat back (it may be the original Japaneze version, more restrictive than later ones). The midpipe that was in there was poorly made - it was off angle by a few degrees such that the Superdragger tip touched (and melted) the rear valence. The Random cat. was properly made and fits perfectly, centering the tip in the valence cutout.

Second, the Random cat. is a "modern" or "state of the art" cat, that is, a two stage unit with both platinum and rhodium. It isn't supposed to need the air pump, in fact it comes without a nipple for air. They offer the nipple as an option.

We'll see how long it lasts without air, as I don't have an air pump anyway. Oh, and no, my idle is just fine, now that I have the Apex'I running the engine. :)

David,

one thing I did notice is that my car is running a little different idle and driving wise with the midpipe installed. It seems the idle has dropped back down to 750 (i know thats right but i like a 1k idle :)) and it just seems a little different. I'm going to adjust the boost back to lower levels on the PFC as well

Really? I didn't know the newer ones don't need air. I got a Random cat several years ago and it had the air inlet pipe. Hmm, if it works well enough to pass emissions, that's a strong argument for removal of the air pump.

Once again, I have a stainless downpipe, had a midpipe, now the Random 5" dia. cat, and an HKS Superdragger cat back (it may be the original Japaneze version, more restrictive than later ones). The Random Tech. cat element is constructed of a spiral stainless steel strip with the catylist coated on the stainless. Random refers to it as a "super high flow" cat. The insert in the picture is of the element, and the whole thing was shot in the hatch, if you're wondering how big it is. We (Maurice and I) had the "bung" installed for the O2 sensor so the sensor would go straight up between the transmission and the body - this is for a "tuning wideband" sensor - Maurice has one - just incase we want to tune the car. The unit should come with a plug for the bung.
https://www.rx7club.com/attachment.p...d=119774&stc=1

Now, with the above in mind, I measured the sound level at idle and at 100 km/hr, using a sound pressure level meter, "C" weighted, at the drivers right ear.
Before cat. - idle - 85 dBA 100 km/hr - 95 dBA (way too loud)
Cat installed idle - 83 dBA 100 km/hr - 92 dBA
Still loud, but that's about a 1/2 power reduction. Outside the car it dropped about 5 dBA!

If you're wondering how to get this cat it costs about US $490 delivered in the US, including installation kit (gaskets and bolts). It comes in two pieces as seen, with a really impressive stainless "U" clamp - my muffler shop charged me $80 Can. to install and they welded the two pieces together on the car so it fits perfectly (no chance of missalignment). I had them do it because I hate working under my car as I only have 18" or so when it's on jackstands! I got it from Canzoomer (RX-8 parts supplier), e-mail Maurice at maurice@harddata.com for info.

The only difference I notice between this cat and the mid-pipe is the sound level is lower and the smell is gone :) . Oh, and I'm no longer afraid to scoot around town using open throttle once and a while as it doesn't scream "I'M OVER HERE OFFICER" anymore! ;) It has a really nice "burble" now, no raspy sound anymore.