For those of you interested, I ran an 'experiment' this past weekend to see how much exhaust emissions the street exhaust puts out compared to stock cats. The systems are as follows, then the results from 2 tests. These are on my 84SE (187k miles) with the mods in my signature line, run on consecutive weekends at the same test station for consistency;

1) Street Exhaust; K&N Filter, CAI/RAM, Racing Beat Header, RB Presilencer, Air Pump installed and operating, Powerpulse rear muffler.

2) Stock Exhaust; K&N, CAI/RAM, Stock exhaust manifold (no heat shields), monolithic converters x2, Catalytic converter, AP installed and operating, Powerpulse rear muffler.


.................................................. ........Max Limit...Street........Stock
HC (Hydrocarbons in Grams/Mile)......2.40...........4.19...........1.21
CO (Carbon Monoxide)......................20.00.........39.10 .........7.20
NOx (Oxides of Nitrogen)...................3.50...........3.14... ........1.35
Both times passed the 'Mechanical Tests'...

The Street Exhaust test was performed on a 'wing-and-a-prayer' that it would pass the mechanical tests, and it did. Apparently the guys at the test station don't know that my big, chrome RB Presilencer isn't a catalytic converter. Probably helped that the A/P was still hooked up and the air bypass tube is there to run the '6'-ports. Obviously, the Street system failed the output tests, however, and was run 3 times with 3 failures.

The Stock Exhaust, with all other things being equal, certainly does it's job effectively, dropping the results on everything to about half what the legal allowance is for this car.

Don't tell anyone, but I'll be swapping the Street system back in this next weekend to regain the lost horsepower. Though much quieter, the stock system lacks both torque and high-end horsepower that's obviously missing when you're used to driving this car every day. HTH, and has been interesting,

 

That's some good info. Thanks for taking the time.

I'm very interested to see the differences in HC going from stock cap and rotor ignition to a direct fire leading igniton which sparks both plugs together every 180° (like DLIDFIS etc). My nose could tell a difference, but I wonder what the actual numbers would be.

I'd do the test myself, but all my rotaries are too old.

 

Engine pics please.