I started a thread in the 3rd gen section. I am looking for some help in figuring out what might have caused my engine to go lean, and/or caused my seals to go. When my engine was torn apart there was no conclusive reason for my seals looking like they did. Any help would be appreciated.

https://www.rx7club.com/showthread.p...35#post9688835

 

Maybe it was the 2 mm after-market seals?

 

Some of the communities experienced guys have chimed in. I'm sure lack of additional oil contributed much of the wear to the seals while the brief lean out did not help. It was suggested to add a bit of premix to the gas when the engine was built and Dave thought that might have been an issue as well.

Also I really need to address the fuel situation because if it happens again during a spirited drive it is unlikely I would catch it in time.

On another forum a guy was tuning his 7 and it did the same thing as mine ( did several runs without issue then suddenly went lean ). They thought it was the fuel filter and later discovered it was a wiring issue. It apparently reared its ugly head once the wires got warm and voltage to the pump dropped.

 

Don't dismiss your oil metering pump as the problem. They can and do fail. On the next build you'd be well served by installing a lower mileage (km-age?) pump, or deleting it all together and going full premix.

 

Just to put things in perspective regarding running "lean" on this motor:

Marco was doing the tuning and driving. He is very cautious and keeps a close eye on the AFR ratios. Then he checks the data log for changes to the knock signal. In the 2 runs that went lean, the AFR moved from a steady reading around 11.1 to a high of 11.9 and to 12.1 in the second, confirmation run. Since the condition started during the tuning session, where we were slowly increasing boost, one could assume there were no earlier episodes of going "lean." For what it's worth, the total time above 11.8 AFR was approx .95 sec over the 2 runs.

The engine was rebuilt after that.

 

Mazda has been using 2 mm 2 piece apex seals in all their FD remans and new engines since approx 2002.

No part # with me right now, if you're really curious I can get it from Ray at Malloy.

OEM seals are not that fragile, they did not fail simply due to the AFRs.

Look into OMP failure, seal clearancing, and the condition of the seal grooves on the engine rotors, as well as the exhaust porting. Something is wrong internally, and it's not the seals themselves.

Edit: I just read the thread again, and a fuel pressure deficit at wide open throttle is a pretty huge problem (as all you guys are aware) and something I've never seen before in all my years around these cars. Have you figured that out yet?

 

Last time I ordered Mazda apex seals, which admittedly was several years ago, the old 3 piece part number was superseded by a new part number and all seals going forward were 2 piece. I don't have the part number handy as I rarely have to order apex seals and half the time use Atkins.

The three piece seal is a flawed design and it looks like Mazda figured it out a few years ago.

 

Any pictures of the housings in this engine? Particularly spark plug area?

 

There is nothing wrong with 2mm seals. 3mm seals provide extra insurance in case of something going wrong causing the fuel to detonate. I personally would never use 2mm seals for an engine that's ment for high boost applications just for piece of mind but their really isn't anything technically wrong with them. However, I would advice anyone building an engine planning to run more then 12 psi of boost to really consider 3mm since lets face it, **** does go wrong when modifying 15+ year old cars.

thewird

 

Well, (as tempting as it was) I resisted the urge to join in on the fun and decided to let the dust settle. This was important in showing that Double_J's original post was actually genuine in nature - if it were my car I'd want to know what the heck happened.

First we need to frame this situation with the following facts:

1.Double_J's original request was for the vehicle to be restored to a near-stock level, with perhaps a bit more power.
2.An engine was built accordingly, with a mild street port
3.A PowerFC was installed and the car and the car was macro tuned
4.The original intent was to run the twins at 12psi, a high-flow Denso pump was also installed
5.Boost issues prevented a final tune, which were later resolved with new solenoids
6.Double_J left with a smile on his face, with the understanding that a fine tune was still required; by this point Double_J had accummulated 4000km
7.Beyond this point, further significant modifications were made, which included BNR twins and changes to the fuel system at another shop
8.Attempts were made to tune the car and a significant pressure drop was noticed after a few heat cycles on the dyno
9.At some point and after a number of pulls to a higher boost level, the engine failed

For those who don’t understand how things work, there are workshop manuals with great specifications to follow. For those who do (and actually trained to create such specifications in the first place), it’s actually quite frustrating to read people’s assessment of what might have gone wrong when the obvious is staring you in the face. The fact is that OEM seals DO fail due to air-fuel ratios and they DO warp and that Mazda HAS made great strides in their cast iron formulation and that ductility IS more visible now and....yes...the 2 piece OEM seal HAS superseded the 3 piece....for a reason. I’ve seen warped 2mm seals AND 3mm seals....all OEM. I won’t go into a discussion on failure mechanics of materials, nor into a 2mm/3mm discussion. As was mentioned earlier, those topics have been covered many, many times.[/COLOR]

While we can come up with all kinds of theories, it’s important to note that the engine ran perfectly for 4000 kms. Let’s face it lack of lubrication, improper clearances would have all reared their ugly heads early on – if not, significant evidence would have been found inside the engine. The car was put through a lot prior to the modifications. I firmly believe that if the fuel pressure hadn’t done what it did, the car would still be running on the original engine today.

[COLOR=#000000]The economy is bad for all of us; it would be nice for people to be promoting their (or their associates’) businesses based on merit not by discrediting others.

Darryl

 

I had asked for help in trying to figure out some possible reason for the engine failure. Things like not enough lubrication. Things I learned are.....triple check omp, oil temp gauge, check wiring harness, PREMIX, and the fuel pressure issue, and another forum !

I got 99% of those suggestions from the 3rd gen section. People were actually trying to be helpful!

I have asked for this thread to be erased (not locked) because it has no valuable extra content.

 

Threads don't get "erased" when they get inconvenient, they get cleaned up. To all replying in this thread from this point on, answer the man honestly or your "opinion" and "facts" are going to be deleted once again.

Insist on being a butthead and things will get worse. This, you can count on. This thread is now on my radar.

Mario III

 

butthead - that would be me. My apologies to Joe, Jim and Darryl and the members of the forum. It won't happen again.

I really need to listen to my wife who told me that when I decide to write about something I'm upset about, I should let her read it before pushing the "submit" or "send" button.

 

I don't care what anyone says, it takes a helluvaguy to apologize in public....many thanks, the rare gesture is appreciated.....and you weren't the only "butthead"..

Y'all have a Happy and Safe New Year in Canada.