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not a twin-pipe but I was surprised to see another big 4" SMB and it's noticeably different from mine so here it is compared to HKS.
My SMB is LHD-only as it doesn't have the steering column squished area, expands to 5 inches then 4 inch (100 mm) pipe until the last couple inches where it tapers to a 3.5 inch (90 mm) flange. Exhaust is 3.5 inch from then on.
So flow area of the 4" (100mm) section would be 7854 sq mm and tapers to 3.5" (90mm) 6362 sq mm
SMB has some top quality stuff. I have a high flow cat I bought from them like 15 years ago, still going strong.
I think to get the best out of a downpipe having an expansion chamber type setup makes a huge difference. Going large on the downpipe will pay off in any power level. Also the JDM downpipes seem to flow just as well as the US ones. even with the funky top to clear the JDM steering rack. Personally I prefer that design since it's a straight shot to get to the 4 nuts holding the downpipe on with a ratchet, you don't have to do 1/8 of a turn on a rear bottom nut slowly to get it off.
So turns out there is a laser cleaner locally that will take small jobs. I just dropped off the downpipes for cleaning. He did a test spot while I was there and it's just amazing. The surface corrosion just vaporizes. Will post pics when I get them back. I wish I had taken a video.
Dale, do you have any pics of your O2 sensor? I'm going to send one off for JetHot coating and will have a bung welded on before sending. But my engine is out of the car without turbos on it so can tell where the clearance needs to be. Any chance you have a picture and distance in relation to the lower flange that connects to the midpipe?
Check out post #20 in the thread I tagged for pictures of placement. Between 3 & 9 o’clock on the inside of the collector. Thread is M18 x 1.5 for the bung.
Unfortunately, the rear mount blocks you from doing it any further reward. I believe yours is like most I’ve seen which are missing the mount. So you could go further back towards the flange. Of course you could always put a bung on the other side of the connection in the midpipe or cat piping. Doing that will start to get into the trans crossmember area making the degree angle more critical. I run the banzai mount and it takes up more room than the oem one. Here are some pics of the downpipe installed that I found years ago when searching. You can have a better visual and figure out what would suit your particular set up better.
So turns out there is a laser cleaner locally that will take small jobs. I just dropped off the downpipes for cleaning. He did a test spot while I was there and it's just amazing. The surface corrosion just vaporizes. Will post pics when I get them back. I wish I had taken a video.
Dale, do you have any pics of your O2 sensor? I'm going to send one off for JetHot coating and will have a bung welded on before sending. But my engine is out of the car without turbos on it so can tell where the clearance needs to be. Any chance you have a picture and distance in relation to the lower flange that connects to the midpipe?
The further down the downpipe, within reason, the better. O2 sensors last longer and stay more accurate when exposed to less heat. This is according to an old friend of mine I trust.
Mike
Now that they are cleaned off. Can definitely tell a difference in manufacturing (not quality related, mainly superficial).
maxim/autoexe/Mazdaspeed is tig welded and it is beautiful. Knightsports is clearly mig welded and not as pretty. Maxim also has the JASMA tag, and a Maxim tag. No markings on the knightsports as far as I can tell.
Maxim Maxim Maxim tig welds. They look this nice on every weld on the pipe. Knightsports tig welded
1985-
Yumex Corporation was established to develop and produce exhaust systems as a partnership between Hiroshima Press Kogyo, Mazda, and Calsonic Kansei Corp.
