Carbon Build up?!?!
06-23-03 | 03:13 AM
#1
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From: Oklahoma
Carbon Build up?!?!
Looking into buying a '91 N/A with 38k miles-- great looking car. He told me that he cracked an apex seal because of carbon build up in the engine. Supposedly you are supposed to take it up to 8,000RPM every once in a while to clean out the carbon... is this true? Also, the reliability on these cars, are they good? This one has a little over 200HP with the upgrades he has done. I'm also looking into buying a Porsche 944 Turbo -- Convince me otherwise! Thanks!
I am selling my 2002 Mineral Grey mustang, check it out!!
Driv300
I am selling my 2002 Mineral Grey mustang, check it out!!
Driv300
06-23-03 | 12:40 PM
#3
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From: Oklahoma
I know, but with the upgrades it will be up to the Turbo II's performance level. The 944 Turbo has terrible reliability anyways, and I can't find a low mileage Turbo II! Please respond guys, about the Carbon build up!! Auction ends in 5 HOURS!!!
Thanks,
Troy
Thanks,
Troy
06-23-03 | 12:42 PM
#4
dont plan on driving it anywhere with a "cracked" apex seal.
i wouldnt pay more than 900 CDN for an rx7 with a blown apex seal (unless it came with a microtec/haltec EMS or something)
i wouldnt pay more than 900 CDN for an rx7 with a blown apex seal (unless it came with a microtec/haltec EMS or something)
06-23-03 | 01:24 PM
#6
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Joined: Feb 2003
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From: Winnipeg Manitoba, Canada
There can be carbon build up, but the idea is to bring the RPM's up once in a while (6500 RPM) to prevent it from getting out of hand.
If an APEX seal is gone your looking at a rebuild though.
If an APEX seal is gone your looking at a rebuild though.
06-23-03 | 01:37 PM
#7
Former Moderator. RIP Icemark.
Joined: Apr 2001
Posts: 25,896
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From: Rohnert Park CA
Heavy or excessive carbon build up is actually more from poor quality gas and oil being used in the motor, and while yes the rotary engines should be taken up to the redline regularly (not occasionally), there really has been no proof one way or the other that high RPMs burn off the carbon. Some carbon build up will happen in every motor, no matter what (unless massive water injection or the like is used).
the high RPM idea is more a keeping the apex seals loose and free issue.
When a rotary is babied (or as in your case, sits too much) gunk tends to build up in the seals, which doesn't let them flex like they should, or compress properly when they need to. So when it finaly does get started or run hard, the apex seal springs are not flexing like they should and the apex seal breaks or fail to seat properly
Now it is not unheard of to have a large chuck of carbon fall off a rotor face, and damage a seal, but IMO it is fairly rare. I am sure some of the more regular engine builders can either back me up on that or dispell that thought.
But in the case of what you are buying it is simply more that the driver was a bone head and didn't drive the car enough, and the motor sat way too long.
It will need a full rebuild with a bad apex seal.
Without an actual list of mods I would also be skeptical that he is really out at 200 HP, since the engine only puts out 160 HP stock.
the high RPM idea is more a keeping the apex seals loose and free issue.
When a rotary is babied (or as in your case, sits too much) gunk tends to build up in the seals, which doesn't let them flex like they should, or compress properly when they need to. So when it finaly does get started or run hard, the apex seal springs are not flexing like they should and the apex seal breaks or fail to seat properly
Now it is not unheard of to have a large chuck of carbon fall off a rotor face, and damage a seal, but IMO it is fairly rare. I am sure some of the more regular engine builders can either back me up on that or dispell that thought.
But in the case of what you are buying it is simply more that the driver was a bone head and didn't drive the car enough, and the motor sat way too long.
It will need a full rebuild with a bad apex seal.
Without an actual list of mods I would also be skeptical that he is really out at 200 HP, since the engine only puts out 160 HP stock.
Last edited by Icemark; 06-23-03 at 01:45 PM.
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06-23-03 | 02:41 PM
#8
FTD Wanna Be
Joined: Jun 2002
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From: Virginia
:I bought mine from a lady who "never drove it over 4000rpm" as if that was a good selling point. It popped about 10K miles later after lots of autoXing and generally hard driving.
An N/A RX-7 will not reach the hp levels of a TII economically, or quietly for that matter. TII~944T
06-23-03 | 07:30 PM
#11
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From: Oklahoma
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2419480201 -- tell me what you think
06-23-03 | 07:36 PM
#12
nice car! something doesnt add up though..
if it had a broken apex seal, shouldnt it have come up in the description of the vehicle?
secondly, on a rebuilt streetported engine, an apex seal failling from carbon buildup is 99.9% unlikely to happen.
if it had a broken apex seal, shouldnt it have come up in the description of the vehicle?
secondly, on a rebuilt streetported engine, an apex seal failling from carbon buildup is 99.9% unlikely to happen.
06-23-03 | 09:18 PM
#13
Refined Valley Dude
Joined: Oct 2001
Posts: 2,283
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From: Kitchener, Ontario (Hamilton's armpit)
Wanna clean carbon out of your 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.
06-23-03 | 09:50 PM
#15
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From: Oklahoma
Black13B--- The motor had a broken apex seal before the rebuild. That's the reason why he rebuilt it! 21k miles in only 12 years means a lot of sitting time, which has to lead to carbon build up... he broke the seal at 32k miles, rebuilt the engine and it now has 38k on it.
06-23-03 | 09:55 PM
#16
wHiTe kNiGhT
Joined: Oct 2002
Posts: 1,393
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From: ct
this car doesnt seem right at all, you say its needs a rebuilt already? and he jus rebuilt it 6k ago. hmm seems weird to me.
also dont you think you should learn little more than what you know about these cars. learn little be4 you go buying parts for these cars.
also na is no where near capible of the power that a t2 is. think about it. a turbo car or a nontubo car. hmm i wonder which has more power.
if you jus paid 6.6gs for this car and its blown i dont know what to say to that lol thats crazy.
i have to say tho that its mint and looks good. those seats are really nice.
good luck with this.
edit. ok i guess i miss understood what you said now. so is the engine running fine now?
also dont you think you should learn little more than what you know about these cars. learn little be4 you go buying parts for these cars.
also na is no where near capible of the power that a t2 is. think about it. a turbo car or a nontubo car. hmm i wonder which has more power.
if you jus paid 6.6gs for this car and its blown i dont know what to say to that lol thats crazy.
i have to say tho that its mint and looks good. those seats are really nice.
good luck with this.
edit. ok i guess i miss understood what you said now. so is the engine running fine now?
06-23-03 | 10:12 PM
#17
Refined Valley Dude
Joined: Oct 2001
Posts: 2,283
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From: Kitchener, Ontario (Hamilton's armpit)
Originally posted by Driv300mph
How about a rebuilt motor at 32k that has been driven 6k miles? Good info by the way!! Doesn't seem very safe but I don't know much...
How about a rebuilt motor at 32k that has been driven 6k miles? Good info by the way!! Doesn't seem very safe but I don't know much...
I have done this procedure on both my and Black13B's 7s. Neither of us has any complaints, and Black13B reported an immediate improvement in performance.
I have no reason to believe that this would harm any rotary, nor that hypntyz7 would post anything he wasn't 100% sure of (and if he wasn't 100% sure, he'd make that CLEAR.) I'd suggest PM'ing him to ask if he has any remarks about using the water trick on the motor you'll be getting... Be sure to include a link to this thread in your PM.
06-24-03 | 12:44 AM
#18
13B N/A POWA!
Joined: Apr 2002
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From: Everywhere, WRLD
I agree, hypntyz7 would definately not say something he's not sure of. He does have a rotary shop himself to of which has a reputation to uphold so he's not just gonna say something for the heck of it (http://www.rotaryresurrection.com is the place if you wanna check it out ...in case you DO need a new motor you can get it from him for a great price).
Kiyo
...in case you DO need a new motor you can get it from him for a great price).Kiyo
