Strong Exhaust Smell Normal with Test Pipe?
 

Hello all. I recently installed a test pipe and I love the feel of the engine, but damn, the exhaust is unrelentingly strong smelling. I have an 83 GSL with stock Nikki, stock rat's nest, air pump installed but not connected to the exhaust (split pipe removed). Car runs great when all warmed up. It will backfire when choked, even slightly, but that's manageable.

So anyone with a test pipe, is the smell just the way it is?

Thinking I am possibly running rich

• I've adjusted the idle speed and mix by the method with the engine warmed up set idle speed to ~750 with the speed screw, then lean it out to stumble and back off a 1/2 turn on the air mix screw.
• My mileage seems low compared to other mentions here in the forum, I'm getting 13 to 15 mpg, lots of short trips around town.

I welcome your thoughts!

Tom

yes, the cat removes the smell, basically. keeping the air pump helps a lot, if the port air part is working.

for mileage, the mile part matters a lot. i took a completely stock and original 1985 GS to sevenstock last year, its an ~800 mile round trip, i think i averaged 25 mpg, this is easily 3-5 mpg more than i've ever gotten from any 12A car before. the best segment was 27 mpg, it was from the top of the grapevine to the central valley, basically its ~100 miles of downhill...

anyways that car had no tricks, engine was original, but tested good. metering pump was bad, so i pre-mixed. it had had the 60k service, so oil, spark plugs, cap and rotor, and air filter were new. mixture was tuned as lean as i could go without misfiring, basically like they tell you in the FSM, or best idle speed, and a little leaner, plugs came out a nice chocolate color. i also ended up resealing the intake, so intake gasket, ACV, and the carb spacer plate thing. the rest of the car was pretty much untouched, it was all in decent shape.

Yes, my wife hates that smell, me on the other hand love it. With my fat nikki I get 24 HWY and about 17 CITY, so yeah you seem a bit rich for whatever reason. Check your float levels to make sure they are in the middle of the glass. Too high and you run rich I think.

Good information. I think all of the OEM stuff is working beautifully, because the factory CAT works great, no backfires and very smooth but with less power. And I completely understand that I'm asking the car to do something that it can't, have clean exhaust without all the emissions equipment. I'll check the plug color and see what I've got.

I pulled the car in last night and as soon as I got in the door my wife mentioned the exhaust smell, it had carried all the way into the house from the driveway, lol.

I've always thought you had a good set up there. I'll check the floats.

I think my middle ground solution will be to install one of the RX7.com high flow cats. I had a good conversation with Ari (he warned me explicitly about the smell with the race pipe) and he mentioned that they've used the high flow cat on cars generating up to 400 horsepower with success. And I'm just a stock port 12A so that should be plenty of flow. And if anybody's curious, the RX7.com high flow cat does use the split air tube.

Thanks!

My wife could always tell when I was driving the rotary car from the smell. When I'd come home late, she would make me toss all my clothes in the wash before I could go to bed.

These things do not run clean. Remember they burn oil on purpose and have always been horrid polluters, which is what famously killed the rotary.

Fuel mileage is directly related to how much fun you're having.

OK, that's quotable.

I've order a Bonez high flow cat from RX7.com, striking the middle ground to clean up the exhaust and keep some of the free breathing compared to stock.

Following up a bit, I've got the Bonez high flow cat and made a small air tube adapter so I can preserve the factory air tube and easily restore the exhaust completely to stock if need be. All of the other exhaust components are factory parts.

https://cimg8.ibsrv.net/gimg/www.rx7...e6cfd2576c.jpg

That is indeed a solder sweated joint between the brass nipple and the steel flange, but I don't think it will get anywhere nearly hot enough to melt it, given the connection to the cat's air tube system is via a silicone hose

https://cimg6.ibsrv.net/gimg/www.rx7...730bd7dfeb.jpg

Here is a comparison of the Bonez cat with the "dry fit" air tube next to the OEM cat from 1983

https://cimg5.ibsrv.net/gimg/www.rx7...24f076ecd5.jpg