Scary N/A moment
 

Tank fulla fresh 89 octane, clear onramp, let's wind the engine out...

Over 7000rpm, engine suddenly starts knocking and GIANT CLOUD OF BLUE SMOKE out the back. Gingerly accelerate in 2nd, more knocking and smoke. Uh-oh. Walk a rotor bearing?

Smoke clears up. Limp it home. Good oil pressure, no more smoke, no ugly noises, but not taking it over 4000rpm either!

Open the hood. Oil all over the dowel area of the rear rotor housing/end housing.

Who wants to guess what I did and why?

Cracked the rear plate ?

my gsl-se used to do that when it ran out of fuel up top... it only put up with that abuse for 2-3 years

Re: N/A uh-oh ....
 

A bit of a long shot , but I would guess maybe damage or spun stationary gear bearing. If it lets go and turns it blocks oil supply gallery to that bearing and that oil pressure will squish out elsewhere (the path of least resistance).I have seen this twice on RX7 12A's on the front gear .

Note: I've driven it roughly 250 miles since then.

It's a weird one!

Here's a hint... it's been roughly 4,000 miles since my last oil change.

dowel area? Means its either leaking from the dowrl pimln o ring or the oil filter/pedestal.

Your still driving it so I'm guessing oil came loose and shorted the plug wires on the rear rotor?

U blew out the o-ring on your oil filter.

^ i'm with T-von.

The oil was three quarts overfull due to fuel dilution. Or at least, it was when I changed it today. I drained seven quarts out of the engine.

At high RPM, it all backed up the filler tube, at which point it sprayed out of the filler cap all over the back half of the engine, and pumped through the breather tube into the throttle body, causing lots of oil smoke and detonation.

Oil pressure is up from 60psi at 3000 to 90psi, which is what the regulator's at. Wonder how much of that oil was gasoline?

overfull due to fuel dilution? what does that entail?

Glad you figure it out the effect, peejay. Now what was the cause? Running a little rich? Or worn seals again?

I knew what it was the moment I saw the oil all over the back of the engine. I knew the oil was overfull (about 3-4" above the full mark, where's that in an assembled engine?) and was planning on a change this weekend anyway... the car just decided to get a "SHAME ON YOU" lick in before I did it.

Better not be worn seals :) Everything in the engine was new or extremely low mile and all the tolerances are at the tight end of spec.

But it won't run cleanly any leaner than 12.5-13:1 under any conditions but over 80kpa (basically, going uphill in a high gear) and 90% of the time it's misfiring, anyway, what with all the burpity brap-happiness, so it's ripe for fuel dilution...

It's not just street vehicles, they developed a quick oil change setup for IMSA enduros the the late 70s.

always something interesting when YOU make a thread, Peejay.

Peejay do you have OMP or premix? I've gone over my oil changes in my fd back in the day and never had that sort of problem. My car was stock of course.

I apologize. My next thread will involve "I yanekd out teh rats nest and now my car wont run WTF" or how about "I want to make 300whp N/A what mods to the Nikki do I need to make ? I have Wanli tires and a black interior if that helps"

Or maybe a thread on which wax is the best.

t-von: I've only premixed for the last 14 years because I never had an RX-7 with a working pump! The fuel dilution only is an issue on the more aggressively ported engines, I never experienced this with a stockport or street port engine.

Nice.

:) stuff your apologies, sir. I rather an intact space-time continuum. now that you've seen the error in your ways, I expect you will take the appropriate action - one of the threads you listed PLUS a "will the FD engine bolt to my N/A transmission"-thread. minimum! do it and you and I are okay. do it not and I will PM every member of this board and tell them that you're secretly working on an actual 6 rotor swap. you have been warned ....


on a serious note though (and this is simple ignorance on my part) I guess I got in the habit of associating fuel dilution with flooding and forced induction. now you're saying bridges (and I will assume peripheral and semi-pp as well) will experience this phenomenon. my question is: is it simply just the difference in fueling requirements stretched over time (4000 miles in this particular case)?

Have you ever taken a good audio recording of a bridge/peripheral engine at idle, and slowed it down a lot?

What you hear is six pulses, then six blank periods of time (sometimes you can hear the weak puffs, if it's good audio) followed by six more pulses... You can calculate the engine speed by how fast the brap is. 1600rpm is about the same as the middle part of Master of Puppets :D

So the engine fires on all six faces, then misfires on all six faces. When it's misfiring, the engine is still getting fuel, it's just not a combustible mixture.

Can you say "recipe for fuel wash"?

Now figure how much time is spent idling at stop lights... idling at stop signs... idling in traffic while doing the Neutral-4th-Neutral-4th shuffle because you can't drive at 30mph steady state without hammering the drivetrain apart... brapping on the highway when not under load...

That's a lot of unburned fuel!

And the times when it IS firing all the time, it's a rich mixture anyway.

Do stockports and street ports have issues like this? Hell no! They always run smooth as silk and you can cruise them at 16:1 down the highway and still have stable combustion. With the "ITB"s I was able to knock my cruise mixture as lean as 13.5:1 but there's still an occasional lean hiccup every now and then, maybe once every couple minutes or so. It'll run at 14:1 cruise but it runs unhappily enough that it actually needs more fuel for the same road speed, so I dial it back to 13.5ish, which is a nice compromise between best fuel economy and reducing fuel wash.

I wonder sometimes what I could get away with if I could play with negative split timing. I hear interesting things about that, but it's not possible with my setup. For now, I just turned my idle down to 800rpm and live with not having any power brakes unless I rev the engine a few times.

wow. I guess when you put it like that, it all makes sense. I never thought of any of it, but considering that my one and only attempt at a race-oriented port never quite got off the ground, I guess I had no real reason to give it much thought.

I will have to try that recording idea you mentioned. sounds like it would be cool.

if you ever feel inclined to try your hand at the negative-split thing you mentioned, I think I have an unmolested Rx-8 timing map somewhere amongst my files. maybe it could be a loose guide so you wouldn't have to work from scratch. i can send you a copy if you want (as long as i really have it - sometimes my mind lies to me).

Very interesting into about the fuel wash Peejay. :bigthumb:

We need to compare dipsticks, You smell mine and I smell yours.

When I use fuel scent, my oil smells like vanilla for the next two changes :)

if you know what you're listening for and the engine is running slow enough, ie idle, you can kind of hear it.

if you crank any rotary over without fuel, it goes DUB DUB DUB DUB, kind of a big bass noise. when the chamber fires it goes BRAAP

so if you listen carefully, its braap-dub dub, braap dub dub , combustion in a bathtub...

haha lol i did the same thing a couple months back, hadn't done a oil change for 6 months, but from using premix when i fill it up plus fuel getting in the oil, it came right out the breather valve from the filler neck.i didnt get ant knocking or blue smoke, did the oil change and good to go.

note! old oil was like water when i changed it.
glad you didnt blow the motor.

i love that some one else feels my driving experiance on a bridge ported motor.