CorgiSteve

I have an 84 GSL-SE with a header and free flow exhaust (no convertor). As with all rotaries, it smells of gas (children say "what stinks!!").

Questions:
- I am wondering if I put a hi-flow cat on, will it reduce/eliminate the smell?

- Will the oil injection of the rotary foul a cat? If so, how does Mazda get around it for the Rx7/Rx8?

- Anything else?

Thanks Steve
1984 GSL-SE

Kentetsu

What kind of gas mileage are you getting? The strong gas smell could be due to a bad temperature sensor causing the computer to run with "the choke" on all the time. This would also make the exhaust smell pretty rich.




.

CorgiSteve

Gas mileage isn't bad - 21mpg combined and up to 30mpg on the highway.
Idle is smooth and it runs smooth and strong tthrough the RPMs.

Steve

SPENT-IT

iTrader: (15)

Gas fragrance additive.

http://www.speedwaymotors.com/Fuel-F...4-Oz,1656.html

Imagine all the people sniffing your exhaust....

I know what smell you speak of.
You may need to drop your gas tank and have the inside steam cleaned. When you have it out and cleaned have it coated inside. It will save you headaches in the future and keep the possibility you injectors getting gummed or clogged from rust. After all it is a older car.

I have a 86 that sat sometime before i bought it.

What happens is the gas will kind of gel/varnish and stick to the gas tank and it stinks.
Every time you add new gas it it eats at the gel/varnish and is a constant STINK.

CorgiSteve

I don't think it is a gumming issue. I just had the injectors serviced and the pre-test showed they flowed at 99%. The car is stored every year for the winter.

The smell has always been there for as long as I can remember (owned it since 1987). It is just a gassy smell (smells like rotary is how some describe it).

Steve

SPENT-IT

iTrader: (15)

No I didn't say gummed injectors was the issue.

I said in more words it may be a problem with old gas.

Like you just said you store it for the winter so that means it sits with old gas. Over time it can get a gel/varnish coating inside.

But if you say it's just pure exhaust gas smell then that's just the price of owning a rotary.

j9fd3s

iTrader: (3)

yes, provided the air pump and air control valve are still there. they actually do most of the work

the oil injection amount is so small its not a big deal.

CorgiSteve

Air pump and air control valve have been removed (normal process when installing a header and removing the cat).

Steve

Kentetsu

Okay, then that explains the strong smell. Now, how is it entering the car so that you would even notice it? Well, there is a seal around the tailight that tends to go bad, and then it kind of sucks the exhaust fumes into the car while driving. Might want to check it out.

But to fix the issue itself (strong smell of gas in the exhaust) you would either have to reinstall the missing emissions components, or modify the fuel map to lean it out.

j9fd3s

iTrader: (3)

you can run a header +cat with an airpump and it'll be as clean as it was stock.

actually even putting the air pump back on, should help.

we tested it once on a t2, with air pump and cat, it did 182 PPM of unburned HC's (hydrocarbons, unburned fuel)

with no cat it did 2000ppm HC's

with no cat no airpump it was like 3000.

with no air pump but with a cat they are usually in the 500ppm range

CorgiSteve

Thanks for the info.

To be clear, when you say reinstalling the air pump, you also mean to reinstall the air control valve, correct?

CorgiSteve

Also, would any hi-flow cat from a muffler shop be OK or is a special one required due to the high temp of the rotary exhaust?

Steve

j9fd3s

iTrader: (3)

yep!

um in CA (california!) we're supposed to use the CARB certified one, but if you get to pick, pick the biggest one you can find. the smaller the core the more restrictive its going to be.

82transam

iTrader: (18)

Damn those are some high numbers! I ran my 12a FB through inspection without a cat once and the HC's were in the 600 range.
I had my T2 FB inspected last year and with the air pump and cat on there the HC's were around 40 lol, runs cleaner than my daily driver Accord does.

To the OP, I would definatly run a cat, you can't even smell my cars at all once they are warmed up.

LongDuck

As the other guys have mentioned, this is part of the 'rotary experience', but there are a few things you can look into to try and cut down on excess fumes.

The SE's are fuel injected, and sometimes those high-pressure fuel lines can get dry and brittle over time. Any fuel leaks under your hood will be sucked right into your interior side vents and in your face because they draw air from the high pressure area right in front of your windshield, which is also directly behind the hood gap. Check your engine bay for fuel leaks and get those fixed up first. Secondly, be sure that rubber dam seal is in good condition at the top of the firewall edge of the hood - it blocks the oil and gas smell from getting to your interior air vents.

As to the exhaust - it depends on which header/presilencer you've installed as to whether you can re-install your air pump and ACV. I have a Racing Beat -SE header and presilencer, and the presilencer has the U-shaped bung for the '6'-ports which is also connected to the ACV along with a flow control valve. When driving, the airpump is still in place, and still pumping fresh air into the presilencer, even though there's no cat in there. Not enough to get you through emissions testing, mind you - but definitely helps to bring in fresh air to react with any unburned fuel in the exhaust.

Based on your stellar fuel mileage, I wouldn't think running overly rich is your problem.

Somebody also mentioned that the rear tail light surround seals often get old and crusty and develop holes. Once this happens, the exhaust fumes filling that static air 'pocket' behind the car will get drawn into the cabin space. Remove your tail lights and you'll see the foam rubber seals located here. If they turn to powder when you touch them - there's part of your problem. Using stick-on foam window sealer and RTV, you can get these seals back in good working order, cut down on the exhaust smell, and also save your lungs and brain from CO2 poisoning over time.

Good luck with it,

j9fd3s

iTrader: (3)

if you can play with the fuel mixture, IE a stock carb, ive seen 12A with airpump/acv blowing into the exhaust ports run clean enough to pass WITHOUT the cat

my FC did like 9ppm, which is cleaner than my mom's 2003 mercedes, it did like 20 or something.

CorgiSteve

Thanks for all the input. The fumes are not getting into the car, it is just the smell when you are beside/near the car, or the windows are open.

Steve

CorgiSteve

One more question.

My emissions equipment was removed over 20 years ago, but I still have the air pump and air control valve in my garage.

There is a pipe from the air filter to the air pump and one from the air pump to the air control valve - no problem. Where does the other pipe from the air control valve go? It has what looks like an in-line airfilter on the pipe.

Does it feed back into the intake manifold? I have a blocked off pipe on there.

Thanks Steve

LongDuck

That 3rd pipe that you mention, if it's roughly the same diameter as the Air Pump feed pipe coming from the Air Filter Box, then it's the bypass hose which goes into what looks like a miniature muffler. That takes the 'overflow' air from the Air Control Valve and routes it back up toward the front of the car, but not into the airbox - it's just to route the air out of the ACV when it's not needed.

Don't ever try and remove that mini-muffler from the ACV bypass line, by the way! It really is a muffler inside, and without it, the Air Pump sounds like an open header when the ACV bypass opens up! It's REALLY loud - I thought it sounded cool for about 10 seconds until I revved the engine, and then realized it was un-Godly loud and put the mini-muffler back on it.

Also, if you're running the Racing Beat header and Presilencer, you can still run the ACV and Air Pump as they were designed - the Air Pump then just pushes fresh air into your Presilencer (which does nothing), but does allow for the air path back to operate the '6'-ports. That mushroom-looking thing in the air feed tube for the '6'-ports is a one-way valve; one way from the Air Pump/ACV to what would normally be the catalytic converter. HTH,