flyrotary@lancaironline.net Mailing List Archive

The iridium plugs seem like a great idea for longer life and better spark. I want to try them in my 13B Turbo engine. My current trailing plugs (BUR9EQ) get fouled quickly at engine speeds from idle to 3,000 rpm, but the leading plugs (BUR7EQ) do not foul. I was thinking that using the hotter leading plug in both holes would solve the problem.

I know that the factory specs call for a colder plug in the trailing position, but I speculate that the reason is because the trailing plug (in factory tune) fires later, after the mixture is already burning and things have heated up considerably in the combustion chamber. If we are using Tracy’s EC2 ignition/fuel controller, which fires both plugs at the same time, maybe both plugs should have the same heat range.

Bob Rogers

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Tracy Crook
Sent: Monday, December 11, 2006 5:21 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: MSD coils - Plug Fouling... again.

Bob, I didn't even know there was a difference in length. They obviously work OK in the Renesis and since I used them in my 20B (with 13B turbo rotor housings) there does not seem to be a problem there either. The iridium plugs I used do not have the notched shell. They were pulled from early 2004 Renesis engines so I guess NGK made that change later.

I have never tried changing plug heat ranges since the standard plug recommended by Mazda has always worked OK for me. Flying at 7000 rpm (or less) is a lot different than racing at 9500 rpm of course.

Tracy (endless wiring of RV-8 panel)

----- Original Message -----

From: Rogers, Bob J.

To: Rotary motors in aircraft

Sent: Monday, December 11, 2006 3:59 PM

Subject: [FlyRotary] Re: MSD coils - Plug Fouling... again.

Tracy,

I noticed that the sparkplugs for the RX-8 (Renesis) engine have a longer reach for the leading plugs (21 mm) than for the trailing plugs (3/4 inch =19.05 mm). The earlier 13B engines all use a 3/4 inch reach plug. See the attached web pages:

http://www.ngkcom/results_app.asp?AAIA=1192340

http://www.ngkcom/results_app.asp?AAIA=1431319

Does the longer reach of 21 mm create any problem for use in the older 13B engines? If one wanted to run a hotter plug in the trailing position, will the longer reach (and hotter) leading plug work in the trailing plug hole?

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Tracy Crook
Sent: Thursday, December 07, 2006 8:35 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: MSD coils - Plug Fouling... again.

.

I changed my plugs to iridium type (stock Renesis parts) about 210 hours ago and they have been wonderful. Never a hint of 'SAG' but I have run only a few tanks of 100LL during that time.

.