i heard that its recomended, ones daily, what exacly will that do. and also my compression is about 90 psi on all rotors, why some say that low compression will cause engine to blow... thanx alot...

 

The old 'adage' to redline your Rx7 daily is decent advice. It reduces carbon deposits on the rotors. However, 90psi is getting low--so you might want to keep in mind that your engine is nearing the end of it's life-span. Personally, I would take it easy--without being paranoid. Meaning, don't constantly drive like a maniac. There's not a lot you can do to stave off failure from the low-compression... Eventually something will fail.

 

Not true. Please don't spread misinformation like this. Low compression can also easily be a result of slightly sticking seals from carbon sticking. There are first gen engines with over 100k and still with 110-120 psi compression.

 

I got 104k on my original Fd engine and still have good compression. I don't red-line it at all but I do perform regular carbon cleaning 2 times a year. Ask yourself this question? Why red line the engine to clean carbon when you should be using the proper solutions that are designed to do that kind of work at a lower less stressful rpm? Sure red-lining really isn't that bad but it's still more stressful. Plus it will never remove the built up carbon chunks that are already on the rotor faces. To keep your engine carbon free run high quality fuels like Chevron w/techron. These burn much cleaner and by nature leaves less black carbon deposits behind out the exhaust. Also twice a year, rev the engine and spray some carb cleaner down the primary ports intake runner nipples or through the TB. This will clean and desolve the carbon build-up on the rotors and engine. Do a search for carbon cleanings and you will find more info.

 

carb cleaner?, You have done it? how do you know that you r getting carbon out that way?
also i hard something about sea foam, dont know if it relates to cleaning internals from carbon..

 

as far as my low comp, it was my 1st engine rebuilt, i was focused on replacing the waterseal, but not to seals wear, test i did was 3 month ago, i might do it again to see if it went up...but i still dont know why some say that low comp will blown ur engine..

 

Wait... I never said anything about "sticking seals"... And (of course) there could be low-compression from seals sticking--and yes there are 12A's and 13B's with great compression, even with high-mileage... But what misinformation did I spread?

 

Below is your quote again. You made the blanket statement that low compression numbers in the 90's is an indication that his engine is near the end of it's life-span. I was saying not true because the compression numbers never tell the real story if the engine is carbon infested causing possible struck seals.

 

OK you have 14 post an choose to question someones methods who obviously has more experience than you on the subject? Well you know you can get advice from someone else who doesn't have an engine with the high original mileage mine does (good luck on that one). You also have the ability to use the search feature and find that these questions have already been answered. I've been driving rotary powered vehicles for over 15yrs and have been on this forum too long to be spreading un-useful info that doesn't help. You do understand that card cleaner is designed to actually dissolve carbon right? Im not trying to be an ***, but nubes questioning the actual experience from someone who has done it do rub me the wrong way.

 

I have taken apart lots of motors, some were run like mad revving the carp out of them
(to the point of spinning bearings)
and others were driven by people who never drove hard at all and they all appeared
to have about the same amount of carbon on the faces.
I would say just drive the car and don't worry about carbon
matt

 

Matt why would you say such knowing that having less carbon keeps the seals from sticking, therefore keeping up the compression? Well I say Mazda should have implemented some kind of carbon cleaning procedure in their owners manuel. I granny drove my 1st gen too the point that it actually carbon locked. Sure this is something that can only happen with a high mileage carbon infested rotary that has been sitting up of months on end like mine did with 150k. I just know my engine wouldn't have failed had a done some sort of carbon cleaning maintenance on the engine when I was driving it. Also my cheap my fuel choice didn't help things either. Anyways, when I broke the engine down everything was well with-in spec so I know it would have lasted much longer had I at least done some cleanings here or there.

 

the carbon wasn't your problem it was the down time that caused the problem.
the down time allowed the carbon to soften and fall off, as long as the motor is
run often it will not soften and fall off in big bits.
doing the "cleaning and or better fuel" might not have made any difference at
all, you will never know.
I would love to see a motor that's had "carbon cleaning" done, pull it apart and
look to see if there really is a difference or not.
like i said i have pulled lots apart and seen them all about the same inside.
I really don't think that there is much you can do to remove carbon from the
rotor faces, other than manual cleaning (motor apart) .
my 2 cents
matt

 

I understant that Matt but, the end result was that the carbon still killed the engine. Here are pics of how bad it was.






Well I do know that my Fd sat up for 3 months this past winter and was never started. When I fired it up, I quickly shut it down after only 30sec to see if it would flood and it never did on the restart. That all happened with 103k on the clock. This is a perfect example of a healthy engine with healthy compression. My 1st gen sat up for the same amount of time and never had any cleanings. It locked up.


Well you may get your wish this summer. Even though my engine is still running great, I'm going to pull it to begin my 20b install. The Fd engine will be pulled apart for a re-freshening with 9.7 compression rotors and set-up for a NA experiment in that 1st gen. I will take plenty of pics and I expect to see very little carbon inside my engine from the previous carbon cleanings. Time will tell.

 

cant really compare a 3rd gen to a first gen, the 3rd gen runs much cleaner, less oil
from the metering pump, leaner fuel mix and hotter, the 1st gen cars with carbs
run stupid rich and the metering pump puts lots of oil in.
the 2nd gens run quite clean as well and i wouldn't expect to see that much carbon in
a 2nd gen unless its been burning diesel.
matt

 

Well that would make some since. Im far from a tuning expert and can see the differences in conditions they both operate. However, I still feel that regular carbon cleanings can only benefit and not harm the rotary engine regardless of what year it was.




Well I saw quite a bit in my stock NA S5 with only 70k when it blew an apex seal. I granny drove it just like my 1st gen shifting at 3k all those miles. This Rx7 also flooded once. It never had any carbon cleanings ever. Keep in mind that I also granny drive my Fd but had the additional carbon cleaning while all of my other Rx7's didn't. The other Rx7 always had hard starting problems and flooded from time to time. Right now, you couldn't flood my Fd even if you tried. Both my S5 and Fd were maintained the same way. Only the Fd recieved the addiditonal cleanings and better fuel from Texaco w/Techron. I can tell a big differance in the way the Fd runs. My ownership experiance tells me this combination works and works extremely well.

 

I bet i could flood it if i tried lol

 

LOL! Good luck

 

Alright t-von, I think we're both slightly wrong:

I was wrong because I was assuming that the original poster had a higher-mileage Rx7 that had gotten to the point of 90psi compression... Therefore it was likely that it was nearing rebuild time.

Since he said that he has a fresh rebuild, it's likely that he cleaned the rotors before putting everything back together. Therefore it's likely that he has no carbon build-up...

 

Carb cleaner... man that’s poisonous.. Have you ever seen a motor pulled apart after it blew a head gasket?... the tops of the pistons are extremely clean, point being you can spray a little water and steam clean the carbon... like water injection

 

Carb cleaner is not designed to be used on throttle bodies and fuel injected cars, it will desolve the special coatings on the aluminum parts.

 

Which aluminum parts are you talking about? Carb cleaner is also sprayed down the carbs of 1st gens which also have an aluminum LIM. Please be more specific.

 

Well actually the water steam clean is what I mainly did in the past. I found that it did more to clean my cat than anything else. But as I said, my engine will be pulled apart soon enough and pics taken. I really can't say when now that my fiancee is moving in with me. Got other responsibilities if ya know what I mean.

 

90psi compression can also be the compression tester the rpm the engine was cranking at etc etc...

compression testers arent reliable enough to judge on the number, you are looking for even bounces

 

yeah me too. ive let engines sit for years, in fields that burned oil when i parked em and had em fire right up.

and as to carbon lock theres a procedure to unlock it, and then they usually run just fine. ive seen carbon lock once, on a 200,000mile gsl-se engine, engine now has 253,000miles on it, doesnt even smoke yet

 

i used regullar piston copm tester, at a healthy cranking... i was getting 90-90-30 on 1 rotor. so i had to MMO treat it over night, loosend up the seals run well now...i did carb cleaner on my motor recently, cant complain i think it runs better..