weaklink

OK...at idle my car has these "pulses" in the exhaust. Slower than the ones in 93blackfd's video, but of course my idle is about 850 compared to his 1500 in the video. The pulses disappear when the idle is above 1000 or so (as in when the car is cold). Seems to drive smoothly. Power seems about the same too. Peak knock is around 19 or so. Starts easy warm or cold. Maybe a little vibration at idle with the pulses. These are definately new. Vaccum is down from -16 to about -14. Got into some big boost on accident with the cold weather 1.29 kg/cm^2 and the symptoms started thereafter. Someone suggested maybe a sticking side seal. Does this require a rebuild?

RxSeven1

iTrader: (2)

do you have a PFC?

weaklink

of course...mods in sig

rx7raca

Yes if your side seal is stuck or w/e you need to take apart the motor, but i dont know how you would be able to know if it was that or not. I would try a compression test, see what happens, might be just a vaccum leak. If compression is good, try to find a vaccum leak, and if that doesnt work, then you got me.

One question, can you post or show me where to get 93blackfd's vid, i never got to see it.thanks

VagaBond-X

iTrader: (3)

its right here

https://www.rx7club.com/showthread.p...hreadid=269567


lol it was on the front page of the 3rd gen section, otherwise with the thread, i cannot help much cuz i'm not a guru at rotaries, i knwo my fair amount and still learning

weaklink

if there was a cracked or blown apex seal would it cause knock? at idle? at boost?

7-sins

hehe sounds exactly like my car...





well that was before I took the motor apart

weaklink

Well....what did you find?

P'cola FD

If it is a sticking side seal, you can try the good old ATF trick:

Put about a quater of a cup of automatic transmission fluid into each rotor housing through the leading plug holes, put the plugs back in, (with the circuit opening relay pulled) crank the engine over a few times, and then go away for a day or two, come back and crank her up, run the crap out of it to clean the ATF out, assure your neighbors that nothing is on fire, and see if your problem is fixed.

First thing first, check your compression. If the compression is good, then that probably isn't your problem. Oh, and always change your oil after the ATF trick.

weaklink

Thanks for the reply Danny. I was going to ask about the atf trick. I might try that. I was wondering...how does a seal get stuck anyway? I have heard that with 3mm if the rotors are not clearanced properly the seals can "float" . I also have heard that at high boost the motor twists (the reason for dowel pinning). I was thinking that if either of these two things is the reason my seal got stuck, pinched, or whatever, then ATF would not help.

weaklink

Regarding the compression test...the only place I know to take it is the Mazda dealer....

7-sins

Probably sticking apex seal. The rear rotor had a **** load of carbon... pics.... https://www.rx7club.com/showthread.p...5&pagenumber=2

All seals which came out were in usable condition

120psi on the front even and 100 on the rear even last time I checked, it slowly got worse though.

But it was exactly like you are describing. When it was cranking it was even skipping like a broken motor. My vacuum dropped a little at idle. The car still had power though above 1000rpms.

Try the ATF/water trick posted above, I wish I thought it was a carbon problem before I took it apart. After the compression test though I pretty much knew it was comming apart.

Good luck,
Chris

rx7raca

Go to pepboys, advanced auto, or any rice boy city store, and buy a compression tester. No sense in making the motor worse by driving it to mazda(if it is blown). They are no more than 20bucks. Very easy to use. If you need help on how to use one, just ask...you can pm if needed.

weaklink

ok do you test leading, trailing, or both?

93BlackFD

seals stick from carbon buildup...sad but true

only way to prevent carbon build up is to get tuned and/or run water injection

7-sins

To test just pull out one plug, L or T, disconnect fuel or what have you. Have a friend crank the car and watch the needle pulse. You’re looking for consistency and also no difference than 20psi from the front rotor readings and rear readings.

93BlackFD

i check with the leading plug

i believe mazda manual says to use trailing

Snook

iTrader: (12)

93BlackFD what exhaust is on your car man? is that the greddy sp or what?

you have a totally straight through exhaust im guessing? Just wondering if it is the sp cause mine doesnt sound like that at all...not the idle because of your ports i mean the sound

93BlackFD

yep, straight through

not sure which greddy it is, i thought it was the power extreme

http://www.mazdatrix.com/e93-95.htm

you tell me, that's where it came from

steve@gotham set me up with his "secret" exhaust ports

maybe that's the diff?

Snook

iTrader: (12)

no, that looks like the greddy sp

can you confirm this though?

If it is theres no way in HELL im taking out my borla xr1 from the midpipe...Thats whats making my car sound awesome.

P'cola FD

Typically, 13b-rew engines don't get dowell pinned unless you're making sick power. My guess if you just overboosted is either a stuck seal, or a cracked apex seal. Only way to find out is to get a compression tester from your local parts store, check the compression, if it is low on one rotor, or low on two chambers of one rotors, then try the atf trick, and then test again. If it is your motor, then you can take a trip to Florida and I'll teach you how to fix the bastard.

Sesshoumaru

iTrader: (1)

u lose compression on 2 bounces if it's a apex seal and one on a side seal.

93BlackFD

it's the power extreme

jantore

Have u checjed your spark plugs. Mine died after a hard track weekend. They where totaly burned upp and all black. Changed them end the engine was fine.

I have a movie of the car, when it had the strange sound. Will try and get it on a server so u can hear it.

JT

weaklink

Yes I changed the plugs right away, hoping for a quick easy fix. No such luck. Funny thing is I never had knock over 69 on the the day in question and usually it is never over 19-21. WB 02 is and was pegged at <10.5 at WOT. I guess I will try to get a hold of a compression tester. I have driven the car several times since then, but it stays the same. Incidently I had filled up that day and premixed 8oz instead of 4 because I was going to turn the boost up to 1.2. I thought maybe I had a clogged injector, so I ran a tank of clean premium through, but no change.