Starfox07

Did the DIY compression test today. 3 strong pulses from the front rotor, and only 1 from the rear rotor. I really don't know what could have caused an apex seal failure in a relatively unstressed engine with 130k original miles. I can't help but wonder if it was caused by foreign debris...

I'll know better when I pull the engine and take it apart. She gave me 6 years of good service, but I'm still sad.

I am now on the hunt for a stockport S4 or S5 six port keg, so if anybody has one or knows of anybody with one, PM me please!

Sgt.Stinkfist

iTrader: (6)

sorry for the bad news but a S4/S5 6 port is a pretty worthwhile engine in a first gen, so consider it a silver lining of a dark cloud.


Whatcha gonna do with the -SE keg?

Starfox07

Not sure what I'll do with the SE engine. If the front half is good, I may sell it.

Starfox07

After reading a few things, I think my pre-mixing noobness might have killed my engine.

I had run the car out of gas tuning the carb, so I grabbed a 5 gallon tank from my shed and filled it with about 4 gallons of 87 octane gasoline. I then proceeded to mix in 16oz of oil (was being lazy, simply did a 'oh, half the bottle should be good!') with that 4 gallons, which gives an absurdly rich premix ratio of 8:1. I've read a few posts that claim that running an overly rich premix can lower the octane level, relatively, of the fuel and cause detonation. The posts I read said this would adversely effect turbo cars mainly, but I may have just proven that an overly rich premix can kill an n/a engine as well.

It's clearly an apex seal that broke, and apex seals mainly break from detonation, correct?

If this did happen, it was clearly a case of me being a complete and total toolbag, but I think it could be a lesson for us all. Be thoughtful out there fellow RX-7 owners, the Wankel Rotary punishes thoughtlessness quickly.

What do you guys think?

elwood

iTrader: (1)

I think it more likely that an apex seal or a couple of side seals are jammed down in their grooves from carbon buildup. I went overboard with premix a long, long time ago, and I managed to jam a side seal. I don't know if there's an effective way to free them without disassembly.

Starfox07

Could it really have jammed at 6500rpm? I mean it was instantaneous.

KansasCityREPU

iTrader: (9)

I thought detonation was caused by having too much of an octane level. My guess is that the extra oil caused more carbon.

Try fogging the engine and working the seals. I bet it comes back. I would at least run it just to check before taking it apart.

Starfox07

Fogging the engine? Please elaborate.

84stock

iTrader: (5)

Ditto, worth a try

Ghooble

iTrader: (1)

I was pretty sure detonation was from a lower octane than required which causes it to predetonate inside the engine, the higher the octane=less chance of detonation IIRC.

But I thought having more oil in the gas raises octane slightly due to oil not being as readily combustible as gas.

t_g_farrell

iTrader: (1)

I would go with the stuck seal theory as well. At 120K my original stockport 12a has seals that
stick if the car is not run for over a week. First startup in this case will only have one rotor firing
and lots of backfires until I can rev it a bit and the seals pop out, then its fine. Symptoms of age
on a rotary.

I would delay the engine pulling and see if you can get the seals to work. Another thought is
to drop the headers and do a visual on the apex seals and see if they look broken or stuck.
That way you can verify if its a broken seal or not.

Jeff20B

iTrader: (13)

I bet I know what happened. A seal broke due to age. The GSL-SE engine lasts almost forever but it will eventually succumb to high mileage and wear. The apex seals are probably worn down to around 5.5mm and should have been replaced at 7mm which is minimum spec.

Like I said the GSL-SE lasts almost forever hence the reason it can live way beyond the 7mm limit. The metering oil pump is superior compared with the 12As which are oiled through the carb nipples, same as early 13Bs with hitachi carbs. Both suffer similar apex seal and rotor slot wear, but the GSL-SE does not.

Go ahead and tear it down. Measure apex seal height in both rotors and tell me whether I was correct or not.

elwood

iTrader: (1)

Oil in gasoline reduces the effective octane rating, which may be counterintuitive. I would guess that the carbon buildup caused by excessive oil might be a bigger problem than the lower octane.

DriveFast7

iTrader: (1)

I've run a horribly rich motor to the point carbon buildup made compression seals stick. And have run way too much premix which does the same thing but much quicker. This may be your situation. Low vacuum cause compression seals are not sealing all the way. Decarbonized it with WD-40, carb cleaner, or Amsoil Power Foam and that fixed it and it's back to pulling hard to 8000rpm. No ****.

I bet the spark plugs are very black, sooty and smell of gas. If the plugs look like that, the rest of the combustion surfaces do too.

I'd decarbonize your engine, what do you have to lose? If anything, if it needs a rebuild there will be that much less to clean.
__________________

Starfox07

I'll give it a shot, but I'm not holding my breath. I hear something spinning around on the rear rotor when I turn it over. Doesn't sound pleasant. Will someone point me to a thread about proper method to decarbonize?

MazdaMike02

iTrader: (4)

Ok there are some posters here who should not post if you don't know what your talking about. Simply put the higher the octane rating the better the fuels resistance to detonation, pre ignition etc.

I really don't think a side seal randomly stuck at 6500 rpm..that's extremely unlikely. But if you really want to decarbonize your engine..buy the Mazda Zoom engine cleaner it works amazing.

t_g_farrell

iTrader: (1)

In that case I would pull the headers and do a visual. It may help lessen the damage
to the housing if somethings loose in there.

wankel=awesome

dont fret! were here to help. I have a seasoned 84 13b with good compression all around up here, youre welcome to it if you can find a way to get it down there.

its original, 108k miles on the clock. has a 12a oil cooler on it, but idk why lol

84stock

iTrader: (5)

If something is rolling around in there (like a broken apex seal), the housing is screwed already, you can't make it any worse.

I would try decarbonizing....

I would also pull the header and feel the seals and rotor edges, there are no diffusers in a gslse so you can get right in there.

snivley whiplash

iTrader: (4)

i had a se high milage engine in in my 7 and did the dell tune. got it correct and low and behold the engine broke an apex seal on the rear rotor. the cause after much analizing, worn apex seal lands in the rotors. so very sorry this happened. From what we have discussed in pm's you have a good tune other than a small primary jet. I do a 70 or larger just to keep the apex seals cool with extra fuel. so let me know when you get set up again and we will go from there.

DriveFast7

iTrader: (1)

If you hear something rolling around in there you should remove the header and just spray some WD 40 down the carb, in the spark plug holes, and in the exhaust ports and turn the motor over by hand until it comes out.

Look in the exhaust ports for damage with a flashlight. Rotate the motor until an apex seal can be seen in the exhaust port. Push the seal in with your finger, it should be springy, push in and come back. Check all 6 apex seals and look in there for damage.

Don't be afraid to use a lot of wd-40, it's a lube to minimize scratching, and it also has mineral spirits which removes carbon. Black nasty snot will come out of the exhaust ports. If the motor isn't blown you can clean it out with Carb Cleaner or Amsoil Power Foam which is bitchin. The mazda Zoom stuff is way overpriced.

What do the spark plugs look like?

dbragg

iTrader: (7)

Don't assume, verify.

If it were me, I would do as suggest here, in this order.

1) Pull plugs to get an idea of combustion chamber status
2) Regardless of visual inspection, clean the combustion chamber
a - I would use Sea Foam, but the previous suggestions are good too
3) Before, after, or probably both I would pull the header and inspect the apex seals as mentioned
4) With the header off, as stated above, definitely look inside the header and engine for loose metal pieces. This is a dead give away and will keep you from wasting time/effort.
5) If you get it back running, do a really in depth cleaning to the internals

During this whole process, I would use a compression tester (modified piston version is fine) to keep solid track of changes in compression from cleaning internals. Sound, pulses, etc. are good for quick and dirty judging, but numbers are better for monitoring progression/digression/no changes.

I hate to hear you are having these problems. Hopefully you can clean it up and get it back running.

Post up your results.

Starfox07

So a little over a year later, I finally had the time to pull the motor. The rear rotor most definitely has a broken apex seal, as seen through the exhaust port:



So here is what I'm thinking, let me know what you guys think.

S5 4 port (or maybe 6 port) keg with my GSL-SE front cover and distributor running premix
Streetport
Long Primary Exhaust
HOLLEY CARB SETUP (I love the look and sound of the Dellorto, but the parts are just too hard to find, and too difficult for me to tune, plus the Holley should be a little more streetable and deliver just as hard up top

Am I missing anything? I think that should be good for around 200whp depending on the quality of the porting.

This means that I'll be selling the 'ol Del (+ two different Manifold options, plus one hell of an awesome throttle setup) so feel free to message me for more info.

wankel=awesome

I have a just finished s4 6 port on the stand in the garage right now... Stock ports, mazda everything...

lmk if thats something like what you're looking for..

MosesX605

I personally wouldn't run a Holley. There's been plenty of good info on the forum regarding the modifications of Nikki carbs, I bet you'd have a really nice runner if you used a hogged-out Nikki on a S4 or SE block.