Cause of too much carbon buildup?? Guru help please. warning long question!
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From: Austin, TX
Cause of too much carbon buildup?? Guru help please. warning long question!
89 TII had 120k on it when I got it for a grand 
Rebuilt engine (me personally) only reused rotors and intermediate housings inside engine. After couple of months did dyno runs ( pics in my garage) ~170RWHP..all looks good.
~5000 miles later now.....engine stops producing power while going down road. I think somethings gone caput (have autocrossed and otherwise not been nice during this 5k after breakin period) so I pull engine today.
Testing reveals stuck, broke seal on rear rotor. 1 good 2 weak compression pattern. Pulled motor today.
Looking in exhaust ports and spinning her over there seems to be to much carbon buildup inside engine for just 5k miles. Seals are all fine but all gummed up with crap.
OK question time.
What are the most likely causes of excessive carbon buildup?? overactive OMP, O2 or other sensor leading to incorrect mixture & wrong temp in engine, ....... At a loss here.
TIA for the help.
Alan
Rebuilt engine (me personally) only reused rotors and intermediate housings inside engine. After couple of months did dyno runs ( pics in my garage) ~170RWHP..all looks good.
~5000 miles later now.....engine stops producing power while going down road. I think somethings gone caput (have autocrossed and otherwise not been nice during this 5k after breakin period) so I pull engine today.
Testing reveals stuck, broke seal on rear rotor. 1 good 2 weak compression pattern. Pulled motor today.
Looking in exhaust ports and spinning her over there seems to be to much carbon buildup inside engine for just 5k miles. Seals are all fine but all gummed up with crap.
OK question time.
What are the most likely causes of excessive carbon buildup?? overactive OMP, O2 or other sensor leading to incorrect mixture & wrong temp in engine, ....... At a loss here.
TIA for the help.
Alan
Refined Valley Dude
Joined: Oct 2001
Posts: 2,283
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From: Kitchener, Ontario (Hamilton's armpit)
I wouldn't speculate on the carbon in your motor since I haven't seen it. But I will offer this, and urge you to learn it, live it, love it and do it.
Do you have pics yet of the goo inside the motor?
Do you have pics yet of the goo inside the motor?
Originally posted by hypntyz7
Personally Im a fan of redlining any car I drive (that isnt being broken in from a rebuild or just had a used engine installed that week) once per driving session, be that once per day, once per week, or 5 times a day.
Now, about this maintenance debate. I am personally a fan of water injection. Not the type turbo guys run to keep intake temps down, but the type you do in your driveway as a maintenance procedure. Find a vacuum line or lines (teed together) that feed both the front and rear rotors, grab the throttle and rev the engine up to 4k or so, and dip the hose in a jug of water and let it drink. The water gets pulled in, hits the rotors and turns to steam, and takes carbon (slowly) with it.
If you're starting with an original/old used engine, Id do this 3-4 times weekly for about a month to clean as much as you can out. I'd also do 2-3 gallons per treatment. From then on, once per month. IF Im maintaining a rebuilt engine, I do this once per month or once per thousand miles to keep everything clean inside.
I have torn down engines where I had previously done this treatment, and they are always very clean, if not carbon-less altogether. The water treatment, along with straight premix, would result most likely in a rotary engine that lasted over 200k miles as the rule, rather than the exception.
Personally Im a fan of redlining any car I drive (that isnt being broken in from a rebuild or just had a used engine installed that week) once per driving session, be that once per day, once per week, or 5 times a day.
Now, about this maintenance debate. I am personally a fan of water injection. Not the type turbo guys run to keep intake temps down, but the type you do in your driveway as a maintenance procedure. Find a vacuum line or lines (teed together) that feed both the front and rear rotors, grab the throttle and rev the engine up to 4k or so, and dip the hose in a jug of water and let it drink. The water gets pulled in, hits the rotors and turns to steam, and takes carbon (slowly) with it.
If you're starting with an original/old used engine, Id do this 3-4 times weekly for about a month to clean as much as you can out. I'd also do 2-3 gallons per treatment. From then on, once per month. IF Im maintaining a rebuilt engine, I do this once per month or once per thousand miles to keep everything clean inside.
I have torn down engines where I had previously done this treatment, and they are always very clean, if not carbon-less altogether. The water treatment, along with straight premix, would result most likely in a rotary engine that lasted over 200k miles as the rule, rather than the exception.
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From: Austin, TX
Thanks for the info...I'd read that earlier tonight and am considering trying it if I can get the damn thing started again.
No pics yet....loaned out camera this weekend.
Thanks again,
Alan
No pics yet....loaned out camera this weekend.
Thanks again,
Alan
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From: Austin, TX
No premix, replaced oil seals, Just got replacement O2 sensor right before she died....replaced today......was one of my thoughts.....shitty gas mileage...
probably running rich but wanting to make sure there's not also something else I'm overlooking...I'd like to not have to do this again.
Thanks,
Alan
probably running rich but wanting to make sure there's not also something else I'm overlooking...I'd like to not have to do this again.
Thanks,
Alan
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From: Austin, TX
Looked good on the dyno but that was WOT and not normal daily driving.
Also, any recommendations for cleaning this crap out....powerfoam etc. Engine is currently hanging from hoist in garage.
Alan
Also, any recommendations for cleaning this crap out....powerfoam etc. Engine is currently hanging from hoist in garage.
Alan
I came, I saw, I boosted.
Joined: Apr 2001
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From: Windsor, Ontario, Canada
In my experience, I've noticed that 7's driven short stop/go distances, ie city driving, will carbon up too much.
The same thing happens with a 7 that is NOT going into closed loop o2 sensor feedback, due to anything defective in the feedback system (not just o2 sensor).
An engine can have dangerous amounts of carbon in a year if the o2 sensor is gone, AND you are only doing city driving.
Carbon build up can lead to many things- Stuck seals, Carbon lockup, and detonation due to glowing carbon.
Guess what?? A good old italian tuneup really works on these engines!
I do primarily city driving, and get a lot of carbon.
The best thing to do is to fill up on 94 octane, dump a few bottles of fuel injector cleaner in, and go for a 6 hour highway trip going as fast as you really can.
If I havn't done this in 6 months or more, my mileage can go up by 10 MPG after blowing everything out!!!
Too bad it costs 50 bucks (CDN) in gas.. but it's fun going for a cannonball run once in a while.
The same thing happens with a 7 that is NOT going into closed loop o2 sensor feedback, due to anything defective in the feedback system (not just o2 sensor).
An engine can have dangerous amounts of carbon in a year if the o2 sensor is gone, AND you are only doing city driving.
Carbon build up can lead to many things- Stuck seals, Carbon lockup, and detonation due to glowing carbon.
Guess what?? A good old italian tuneup really works on these engines!
I do primarily city driving, and get a lot of carbon.
The best thing to do is to fill up on 94 octane, dump a few bottles of fuel injector cleaner in, and go for a 6 hour highway trip going as fast as you really can.
If I havn't done this in 6 months or more, my mileage can go up by 10 MPG after blowing everything out!!!
Too bad it costs 50 bucks (CDN) in gas.. but it's fun going for a cannonball run once in a while.
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