fisheye

i have an 85 rx7 with a 13b. supposedly it has a bridgeport on it, but im still trying to figure out just what that is. when i got the car, it did not run due to an amature trying to adjust the float levels in the carb. i tinkered for a while and got it running. long story short, where i am at now is the car backfires through the carb at about 4000 rpm during acceleration. it only does this when in neutral seeing as how it has lost enough power that it wont hardly get to 4 grand under a load. i have cleaned the plugs, and tinkered with the timing a bit, but i still cant get rid of the backfiring. i beleive it is coming off of the front rotor, because when the ac is on, if i unplug the the plug wires for the back rotor, it dies but if i do the same for the front rotor i get almost no change. please help me, im one dead end away from an anurism.

fisheye

oh yeah, it has a racing beat intake and holley 650 double pumper chokeless race carb. please forgive my ignorance to rotary terminology, as this is my first rotary, and coming from a primarily deisel background, well, lets just say im learning alot.

LizardFC

iTrader: (1)

If it had a bridgeport, you'd know it. It's not a mod you do on a daily driver. They usually idle very loud and rough at 1500 or so with the signature "brap" sound. They also produce a lot of power high into the powerband, beyond the redline of a stock motor.

If your motor doesn't have a large port such as a bridgeport, then that carb is way too big. Tell us everything you know and can observe about the car and we'll try and help.

fisheye

When I first got the car running, I was amazed at how much power it made. By comparison to my old 93 camaro, the lt1 had torque all over the rotary, but the rotary pulled just as hard as the lt1 from about 5000 on up to 7000. The catalytic converter plugged up on me, and that's when all my problems began. Initially I thought the engine was toast, but after trial and error adjustments, it has started to come out of its funk. It idles pretty rough, and when the engine is not under a load it sounds great. However, as soon as the engine is under a load, I get backfires through the carb. I'm just abou at my wits end.

fisheye

I'm going to get new spark plugs and give that a go. The cap and rotor seem to be in good shape, and they wouldn't be here for a week if I ordered them today. Guess we will see if this helps or hinders.

LizardFC

iTrader: (1)

Is the cat still clogged? That'll cause exactly the symptoms you're experiencing, and on a ported motor the problem will be much more pronounced. They really need to breathe. Although I highly doubt the motor is ported... it wouldn't have a cat at all. Bridgeports practically require a straight-through exhaust. I think someone was yanking your chain honestly.

Rotospeed

iTrader: (8)

Are all your coils working ? Some picks of your car/engine bay could help

fisheye

I knocked the guts out of the cat. The guy I got it from had the exhaust unhooked pre cat and ran it that way. I just changed the plugs, an it got worse. I don't think the front rotor is making any power at all. If I pull either trailing plug wire I get no change in rpm, and the trailin coil arcs at the wire boot to the front wire on the coil. If I pull the leading plug wire to the front rotor no change in rpm, the leading wire to the back rotor it dies, and no arcing at the coil. I will upload pics in just a few minutes if that will help.

fisheye

just uploaded a hand full of pics, the album name is 85 rx7 (bridgeport?) AFU.
by the way, thank you to you all for your kindness and willingly sharing your knowledge. it is appriciated greatly.

fisheye

i was told this was a 6 port 13b. i dont know that this has any bearing on my issues, just trying my best to convey all the information i have available.

ztfdrake61

This is a key development that points to an electrical issue, check the coils, plugs, and wires, because you get most of the power from the leading plugs, the trailing are mostly for emisions and many owners run their 7's without trailing plugs at all

fisheye

About the coils, if I replace them, do they have to be a stock replacement or rotary specific? Or can I use a pair of good ol msd blaster 2 coils? Also, if I were to do a compression check, would it matter which plug port I use? Thanks ztfdrake

BeenJaminJames

Sounds to me like you might have blown a seal or two...have you checked the compression? As you may know, there's a special way you have to check the compression on a rotary, since there are three combustion chambers for each rotor. Here's a link to the best write-up I've yet to see on how to check compression. http://www.aaroncake.net/RX-7/blown.htm Hope this helps, Ben

EDIT: Any ol' coil will work, if it's a good coil.

fisheye

Thank you BeenJaminJames, I just got home from work, and I plan to try the audible test shortly. That article was a tremendous help.

fisheye

Sounds like a blown end seal to me. Its on the front rotor. Can I replace the end seal on one rotor without tearing into the rest of it or am I looking at a complete rebuild?

BeenJaminJames

By end seal, do you mean side seal or apex seal?? A blown apex seal will affect two sides of the rotor, a side seal will affect one side. Sorry to tell you but you are looking at a complete rebuild, however depending on the condition of your housings it might prove to be somewhat simple. I've replaced single seals before in cases where the others were in good condition--but you still have to dissassemble the whole motor. Rotary engines are usually dissassembled from the rear, although I suppose you certainly could open up just the front if you were careful. The bad thing is untill you tear the engine down you wont know what your housings are like. How much have you spun the motor over since the seal went out? Check out Aaron's rebuild video, it's fairly informative. http://www.youtube.com/watch?v=ijJeUk_GqiI Good luck, Ben

fisheye

Its been spun around a lot. Looks like this one is toasted.

BeenJaminJames

Sorry to hear that, well if you find yourself looking for a new engine, or help and advise rebuilding the one you've got, just let us know. Hope you get her going soon, Ben