My Rebuilt Engine has Gone Again aaaaaaaagh

F

frank20bcosmo

Member
:
eunos cosmo type s 20b
Bad News

after having just completed 380kms after the 20B went in for it's first service after running the motor in it has gone bang !!!

It was boosting up having just overtook another car and I got a terrible groaning vibration it felt like the prop shaft had just lost a UJ joint and that was it.

I am absoloutely gutted,, I have not got any spare cash at the moment to get it done I just paid out over $6k a year ago and here we are 2,000 kms later and we are having to do it again, the motor runs but it is very sick sounding like it is running on 2 rotors or less

I am falling out of love with rotoaries this is my first one and the engine has gone twice now
but I love the car so when I get it sorted I have got to find out what is causing it to do this
I could understand it if I was thrashing it everywhere or drag racing it,, oh well anybody want to be a kidney !!!

Frank
 
Have you had a compression test yet Frank? Hopefully it is something like a broken igniter... fingers crossed.
 
mate i feel for you paying for this twice already and it having to consist of all the parts. same builder? they should give you some form of warranty on the engine they rebuilt.
I got 1 year 20,000k's without even asking for it.
what seals did you get.

I"d make him fix it especially if it's happened twice.
that just isn't right and you shouldn't have paid the second time let alone a third.
this is a rotary specialist rite?
 
Hi Berty

been really busy at work so not been on the forum for a while

No I have not had a compression test done on it yet as the builder is over 160 kms away so once I take it in it will be staying in to get done.
I could try to do the comp test myself but I don't want to mess with it just in case it is far less serious than it seems and I make it worse

Hi 13B, I only have had the engine rebuilt once not twice, christ if this was the third time I think I definately would call it a day, the warranty was made invalid as I had him fit a boost controller when it went in for it's first service after the break in period
 
not as bad as i thought i guess.
may i suggest not using mazda seals or any that are known too chip. also adding 2 stroke when you add petrol. whilst keeping the omp, i believe it goes a long way in longevity of the engine and drastically reduces rebuild costs if ever needed.
that's my opinion anyway
 
Frank,

I would like to know few things about this engine.

1. Does your builder have experience building 20B?
2. What parts were damaged from original 20B and what parts were used and replaced?
3. Find out what parts are damaged from this time around.

I say this because most likely faulty parts could of been used and same parts are failing again. Also, pending mods, you might be blowing these motors via lean fuel or something not related to engine short block... ie bad injectors or timing.

Best is to find out what was wrong before and also what is wrong with it now to correct all the issues. If you went with respectable and experienced builder, he/she should be able to show you what had happened during break down. I always recommend seeing yourself during break down of these engines...
 
13bcosmo said:
not as bad as i thought i guess.
may i suggest not using mazda seals or any that are known too chip. also adding 2 stroke when you add petrol. whilst keeping the omp, i believe it goes a long way in longevity of the engine and drastically reduces rebuild costs if ever needed.
that's my opinion anyway
Click to expand...

My opinion varies slightly to this..

I have mix feelings about pre-mix.. 20B on a cosmo runs super rich (10mpg) on street driving. I am a believer of OMP and its almost better to tab the OMP and run fresh oil vs. adding 2cycle to your fuel tank. That being said, I'm not again 2 cycle.. I do think for high stress engine, 2 cycle will give additional protection. The problem is that sometimes using 2 cycle on high mileage car could lead to stuff breaking down in the fuel tank and causing clogging of your fuel filter and lessen the flow of your fuel. If you were to pre-mix, I would change the fuel filter shortly after and also becareful about using fuel additive to clean injectors.
 
I have only premixed from a fresh engine i'm completely unaware of my tank condition. is that a major concern.
have kept the omp and only using 40ml to 10litres.
extra protection and because of my harder seals.

by tab you mean something along the lines of a rotary aviation adapter?
I looked at those but they're for omp deletion correct? and only can be set to use 100ml per 10 litres. I was chasing one for ease of adding petrol...

i will be sure to take notice of the fuel filter and injectors.
their cleaned by my mechanic every service.

i do know that my car had issues before i bought it with injectors they would have been replaced.

thanks for the heads up.
 
Last edited:
I actually meant 'tap' not tab... Sorry about that typo.

What I meant is to either tap the stock OMP (FD guys do this and I'm about to do it and going to check the 20B OMP) or go with SOHN adaptors (aviation). This way you are injecting clean oil vs. used burnt oil from the engine. Also, you could run 2 cycle through your OMP system. I also don't recommend using any other apexi seals than OEM for street driven car.

Regarding tank condition and such is because when different types of gas and unknown sedatives build up, it could be loosen by adding of 2cycle. You have to think about it this way, your ecu will inject certain amounts of fuel based on MAF reading and MAP reading. It can not calculate based on fuel pressure nor injector efficiency. Hence if your injectors are blocked or fuel flow is inhibited, then you will lean out. Also, 2 cycle on FD or Cosmo is better vs. 8 in that we have return system.
 
you have given me a lot of food for thought. will have to do some researching.
what are the drawbacks to a clean oil system.
main reason for non mazda is simply because i see them as causing a lot of damage when they do give up the ghost.
what is so great about standard seals, are they continually improving them.
 
I've spoken with some leading rotary engine builders.. including Dr. Francesco Iannetti (ceramic seals Mazda race cars use) told me that for street driven car mazda OEM seals are recommended.

You have to think, Mazda spent great deal of money to develop apex seals. They are made so it causes least amounts of chattering on the rotor housings. But that being said, building a well spec'd engine will last longer vs. poorly assembled engine. Hence you want experienced builder to build it.

Some of the shop made seals are stronger and it might handle bit more detonation as they say it will. But that does not mean your engine will last longer. I would consider some of these "unbreakable seals" only for testing and possibly high HP engines that require regular interval rebuilds.
 
mazda one's took out my rotors housings and turbo's. sure they would have been 15 years old. they even let go when i wasn't behind the wheel which is a rare enough occurrence as it is.
But I'm willing to trial whats in there now. tuff stuff seals. there really isn't much about them online and they have been around for a while. mostly used for drag racing. I'm yet to hear a complaint about them. only time will tell i guess.

I know many japanese tuning companies won't use anything but mazda seals. I just can't be buying everything every time the engine needs to be pulled apart.
 
When apex seals go, either OEM apex seals or other seals, it will most likely take out other components. That being said, not sure why you are loosing so many engines. But statistically, there are far more engines out there with OEM seals with many many thousands of miles vs. other seals. If you are blowing engines, it could be other issues and not apex seal based problem.
 
Hi Mazda Speeder,, sorry for not replying sooner not been on the forum for a while just been very busy with work nothing exciting like working on the car
that was a cheap car but could of been a lot of trouble if the engine was not right but I am sure somebody bought it just for the engine
and will probably sell the car minus the engine.
not done anything with mine due to funds but all being well will get it back to the builder in the new year and see whats gone this time gulp!
 
Last edited:
Hi Herblenny
to answer your specific questions, the engine builder has a fantastic reputation with rotary engines and actually races a rotary on the track and used to race a 20b
he has just built a quad rotor for a customer ina rx7 so I have no issues with his knowledge.
2, the apex seals went on one rotor last time but in my ignorance I ran it for a while so it ended up taking a rotor housing so the seals were replaced on all 3 rotors and it had a new rotor housing, it was also street ported whilst it was out.
3, soon as I get it in and find out whats gone I will be going over to look at it myself and discuss what we need to do to sort it out and try and find out what caused it to go, as I have said to him that I need to know what is going wrong when I know he regularly builds 20b engines with over 480hp,, so something is not right
will keep you posted
Frank
 
Sorry to hear about your engine troubles, Frank! :(

On the plus side...This thread is a winner, great discussion about oil injection and apex seals. In terms of Mazda OEM Vs Aftermarket...My friend who works at the Mazda Dealer often recommends Mazda OEM over Aftermarket for critical parts like filters, seals etc.

As for engine longevity...I think a frequent maintenance routine has the most influence on engine life as opposed to depending on hardcore parts and tricks...Although I have a passion for the exotic / hardcore, I will go for the less exotic yet proven route if it results in long term durability and reliability.
 
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