I have an 82 12A that is stock except for a RB header, presilencer, muffler. This problem was also present with a stock exhaust.

On full throttle acceleration, I feel one or two pops through the gearshift lever on the way to red line. I had thought this was maybe something binding in the driveline, but now I'm wondering if the engine is pinging.

What does pinging feel like in a rotary? I messed around with the timing a while ago, but the car still passes emissions. I never feel the pop except at full throttle.

The u joints are good, and the clutch/PP have very few miles on them. Anything else to check?

Thanks

 

im probably WAY off, but is it when you let off? it might be back fire? but im sure you know what that is, so im probably wrong.. i have no clue, just trying to help

 

What kind of pops? Backfires on the way to redline heaven could be an ignition problem. I just started to get a bit of a stutter as I go above 6K at full throttle, going to track it down today, I hope it's not igniters. As far as I know a ping, sounds just like it says, a high pitched metallic ping.

 

it sounds like gravel according to mike-p, because you just popped the motor, through a seal, choked the chicken, ok i'll stop. very super good chances are you aren't detonating. in a piston engine it sounds like metallic pings and clinks due to the piston striking the cylinder wall as the that is the only way it can slightly move due to the pre-ignition forces. in a rotary, i have no idea. it is so susceptible to detonation that i don't think it could even reach an audible level before you popped the motor. you probably are having bad ignition, running rich and have a holed exhaust, or something else odd that i can't think of right now.

 

in a rotary it sounds like a chattering sound (that can vary in pitch anywhere from a car from the 40s with bad exhaust to snare drum ... those are the best examples i can think of) the engine will rev, but you feel like you just blew an ignition wire or something. some people say they can feel it, but i've never FELT it ... i just heard it when i was having timing issues with the first 13B i built.

 

i thought rotarys were anti detonation because of the larger surface area in the combustion chamber.

maybe its missing. you would feal that through the shifter.

start replacing ignition stuff, it should be replaced anyways.

 

Its higly unlikely you are detonating in a carbed car w/o a turbo.. Detonation is the firing of fuel or the lack of at the wrong time, usually is indicated by a very very lean mixture dude to the turbo injecting air boost...

Some refer to it as a popcorn sound, others refer to it a a chattering sound.. The ones I heard do it sounds like a bad backfire, but inside the motor. The bad thing about detonation is it can happen several 100 times inside the motor at totally the wrong time... Thus detenting the rotor, or worse firing directly on the apex seal.

 

Preignition occurs mainly due to the compression increasing the temperature of the fuel/air mixture to at or past the autoignition temperature. Piston engines are more likely to have hotspots, but I think a sparkplug could also form a hot spot. Remember that the 12A has what, 9.4:1 compression ratio? In Mexico, the VW beetles that they made down there for years had motors that had 7.8:1 compression because of their cheap gas. (Stock compression for a VW in the USA in 1974, last year for the standard beetle, was 8.6:1)

Point is that its possible.

But I'm thinking that what neil is describing is misfiring, not detonation.

 

Yee Haw, 100th post

 

Thanks. I'm not talking about backfiring... it only happens at WOT. There isn't any noticeable interruption of power, and there are usually just one to three pops between 4000 rpm and 7000. It definitely doesn't sound like the chatter you get in a piston motor.

Is it possible something in the tranny/clutch/diff is about to give up? My third gear synchro is a little weak. I drained the tranny and diff gear oil. I found a couple of little chunks of metal on the tranny drain plug. Nothing from the diff.

Neil

 

Pinging can happen if the wrong octane of fuel is used. On some older 8-cylinder cars, it was necessary to run higher octane fuel because they ran hotter.

 

I had this problem, just back off the timing A LITTLE. I was getting too abicous with the timing to get the more power, and clearly going too far will result in pre-igniting fuel. Only occurs at or very near full throttle between 4-7000rpm typically. However, its fair to point out I don't have the weber carb tuned at 100% ideal.

 

neil ~
this pop that you're getting at WOT ... does it kinda sound like the engine is sneezing through the carburetor?

anyways, give it a real good, complete tuneup. set the timing to stock, make sure your coils are firing up to snuff. if it still does it then, then we can explore other things.

and by the way, i think it's normal to see little metal filings on the tranny drain plug, but chunks?????

 

I was able to borrow a timing light - so I'll set everything back to stock this weekend. I'll also check the plugs. I think the coils/wires/rotor cap and button are all fine. If the timing doesn't fix it, I'll start replacing those parts.

Yeah, the tranny has me a little worried. The chunks were about 1/4-1/2 the size of a pencil lead or pen tip. I have a spare tranny lying around, so if it fails, It's not a huge deal.

 

lol, a gear tooth or 2 fell out. is this bad? gotta love having extras. you are sure the other tranny is ok aren't you? that would highly suck goat if you put the other one in and it ****.

 

if your gear teeth are breaking off, i would guess its gonna need a replacing soon lol. especially if the teeth are from a forward gear which takes much more abuse than reverse.