I have a 1988 Mazda RX7 Turbo 2 running a T66@10psi/15psi. At either boost level the car has started to misfire above 5000rpm when under load in either 3rd/4th/5th gear. I'm running stock ignition and this originally wasn't a problem, but started happening when we dyno'd the car after installing a new Aeromotive FPR. (Car on the dyno made one clean pass and had 11.8:1 afr's under boost)

Would new plugs solve my problem? If so should I go with B10EGV's or is there a better plug for my application?

-Rob-

 

If you're not already doing it, think about going for heat range 9 plugs all around.

 

Already did it...

EDIT: I know theres other guys that have to be making 400whp+. What plugs do they use?

I'm planning on 500whp soon. What plugs would that require?

 

Jeez, think about 10.5s? I imagine your plug wires are upgraded already, too. Maybe a capacitive discharge ignition system like a Jacobs FC1000 would help with your problem if hotter plugs don't work.

 

I'm going with the MSD 6A ignition.

I didn't have this problem on the stock ignition for a while.

Does it just sound like I fouled some plugs?

 

Possibly, I would use the NGK Racing Spark plugs.
http://www.rx7.com/store/rx7/fcignition.html
Bottom of the page.

 

28$ for a spark plug is ******* insane.

 

Did you check the plugs to see if they are fouling or misfiring?
If it is the spark plugs, go one step colder.
The B10EV's are the cheap option.
NGK does make a rotary specific 10.5 heat range plug, but it's big bucks - like $30 / each.
Another (expensive) option is to use the Denso Iridiums - $30 / each.

I think the CDI box will probably fix your problem though.


-Ted

 

If I fouled the plugs I would think it was too much heat.

I'm gonna try the 10.5 range plugs and the 6A and see if that fixes my problem

Thanks guys

 

How did you plan on getting 500whp?

 

Okay, and if that doesn't work, you're looking at nearly $30 per plug, either from NGK, Denso, or HKS (Denso with HKS stamped on it). 10.5 should be enough, though.

 

Check your plugs if they're colored bluish/purplish on the threads. If it is, you need colder plugs. The NGK 10EGV's are great plugs for high output engines. Your problem *could* be just weak spark that may need a boost from a CDI box.
I had ignition break up near redline when I dyno'd with comp. upgrade/ turbo. The CDI box solved that. The plugs were fine which were the BUR9EQ in all 4.
I'm using the B10EGV now which require thin walled sockets to install them.
When choosing those "motorbike "plugs, you need to use the "B" which are 14mm plugs. The last 2, 3 letters designate plat. or iridium .

 

I have a fairly long mods list. Only thing stopping me is this ignition problem since the only stock thing on the car is the ignition box.

I dyno'd 352whp in 2nd gear with the misfire. We shut down at 6k because the breakup was pretty severe. (15psi of boost)

EDIT: We did a pull in 3rd gear and shut down around 5000rpm with ~380whp because the breakup was bad again.

 

You should check into those groovy awesome NGK spark plugs.

 

I'll buy the special NGK rotary plugs if they'll solve my problems.

RETed, do you know the part number for the NGK rotary plugs? Should I use those or just go with the Denso's?

 

http://fc3spro.com/TECH/MODS/IGN/plugs.htm


-Ted

 

Stick with the NGK, they always work for me. I change them about every 9 months. I put about 200 miles a month on the FC.

 

i remember someone a while back was talkin about using motorcycle spark plugs or something... anyone have details on that one?