[Home | Mail Archive | Join the mail archive | Photo Gallery ]

Mazda Rotary Pickup Forum
you are logged in as
profile | register | faq | search (active threads) | memberlist
Sponsored by:
Index > Engine/Drivetrain > Thread: Cat looks like Christmas under my REPU
Thread: Cat looks like Christmas under my REPU

Posts: 458
posted December 05, 2004 09:45 AM

Cat looks like Christmas under my REPU

I just got a new exhaust put together for the REPU and I am very happy with it thus far. I have a concern about the bright red that it glows after warming up a bit. I have been playing with timing and I rebuilt the Weber but still it glows.
I have a couple concerns, first is the timing. I dont really know if the main pulley is on the right direction or not. It seems that I can rotate the distributor 180 degrees and not much changes. How do I know if I am 180 off or not?

Maybe I need to get smaller jets for the Weber, would a glowing cat be an indicator of too rich or would it mean too lean? Actually, the flame I noticed out the back (through the cat) would probably mean I am running rich?

My tags just expired the end of November and I have been trying like mad to get it running right (clean) for the last few weeks. Anything that anybody can think of would definately be appreciated.

On a positive note, I finally installed the Racing Beat header I have had in my closet the last 2 years. From there I go to 2.5", through the cat and exiting through a Magnaflow 2.5", 27" long, 6" diameter straight through muffler. It sounds pretty awesome. I had it all put together with flanges and a mid-pipe made for, ahem, racing use. Cant wait to hear it like that, should really scream!

        Click here to send Tom93R1 an ICQ message. Click here to add 16640317 to your ICQ list. Click here to visit Tom93R1's homepage. Click here to send Tom93R1 an AIM message. 
View IP (Administrators only)

Posts: 427
posted December 05, 2004 11:17 AM

Glowing exhaust....

means you are lean. I had the same problem trying to time my truck. Pulley was 180 off. Good luck!
1974 Mazda Repu
1986 Yamaha RZ 500
1988 Yamaha YSR 50
1991 Suzuki RGV 250
1992 Yamaha TZR 250 SP
1996 Aprilia RS 250
2003 Ford F-450 6.0 Diesel
2004 Mazda RX8
2006 Yamaha Banshee
2014 18' Eclipse Toy Hauler

View IP (Administrators only)

Posts: 661
posted December 05, 2004 01:45 PM

Dizzy at 180 off is normal 50% of the time (it spins at half e-shaft speed). If the pulley is 180, you'd have a tendency to want to correct it by swapping L1 and L2 plug wires, which would make your ignition retarded by 180 (very late leading). In other words, your exhaust would tend to glow because the fuel would burn there instead of in the engine. A similar thing happens when the leading ignitor dies and you try to run the engine on trailing alone. Again, the retarded ignition causes the fuel to burn in the exhaust system instead of in the engine. Of course this applies to a stock FB ignition system, and you've upgraded yours to direct fire.

On the flip side, if the ignition is working fine and the carb is like super-rich, the engine will run cool, but the exhaust will run hot (and glow).

Tom, are you aware of the thick wire method of finding TDC? Just remove L2 spark plug, poke in a thickly insulated wire and start hand-turning the engine while sliding the wire in and out. You're trying to feel for when one of the rear rotor's apex seals comes down and touches the wire. The thick insualtion won't damage anything, and when you feel resistance on the wire, back the engine off a degree or two and you'll be close enough to TDC on the front rotor so the pulley marks will line up with the pin on the front cover.

If you've ever imagined where and how the rotors are positioned inside a two-rotor engine, you'll see that when the front rotor is at TDC (rotor face is up close to spark the plug holes), the rear rotor's apex seal will be right in between both plug holes. That's why you'll want to back the engine off after the apex seal touches the wire. You'll be within a couple degrees of TDC which is plenty for installing a pulley on any '85 or older engine ('86+ have an offset bolt to avoid this sort of confusion).
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

View IP (Administrators only)

Posts: 1877
posted December 05, 2004 02:09 PM

Good to hear

you got your header on! Now, I wouldn't expect any bits (cat, magnaflow, etc.) not specifically constructed to withstand the extreme heat and pulse to last very long before disintegrating, but... it'll no doubt be a blast, meanwhile!
As regards tuning for the cat --nevermind more generally-- I'd give Racing Beat a call... betch'a they know a few things...

View IP (Administrators only)

Posts: 458
posted December 08, 2004 11:28 PM

Well I got through emissions. A friend had a set of really small jets and I used those. It ran like crap but was amazingly clean. The night before I did that I was idling the truck and noticed a beautiful, dark blue flame at the tip. Very cool! But very hot for the cat, it really glowed good! As soon as I got through emissions I removed the cat and put in my mid pipe. Dont want to burn up my new cat before I even get properly jetted.

I did some research on the weber carbs and jet sizing and it looks like I am jetted for something more than a large street ported 13b. Probably a bit rich for my stock 6-port. I ordered some jets based on other configurations I found, hopefully it will be close.

Right now it is awesome! I never had so much power out of it, and so smooth! The sound of the Magnaflow is better than I had imagined it would be. I highly recommend this one to anybody who is thinking about a new system. It is not very loud at all even with the cat pulled, I still hear my carb over the exhaust when I get on it.

Thanks for the thick insulation wire test. I will try that out this weekend. I also need to redo my direct fire. I went back to stock 83 electronic ignition setup while trying to diagnose other problems.

'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
really loud!

        Click here to send Tom93R1 an ICQ message. Click here to add 16640317 to your ICQ list. Click here to visit Tom93R1's homepage. Click here to send Tom93R1 an AIM message. 
View IP (Administrators only)

Posts: 1
posted March 03, 2006 12:32 PM

I don't remember you doing that wire test! I think you just fumbled with the ignition like a lil chimp for long enough that it worked!
White 87 RX-7 Turbo II

View IP (Administrators only)
All times are PST (US)
Post New Topic    Post New Reply
Rate Topic:
Powerd By: BlazeBoard

[Home | Mail Archive | Join the mail archive | Photo Gallery ]
0.021627902984619 seconds processing time