I could really use some input here. My engine lost compression and I need to figure out what went wrong so it can be corrected. At the time it went my engine was rebuilt, and only had 4,000 KM on.



I have attatched pics of my Mazda OEM seals. Take a look at the pics, and tell me what you think. The engine builder was not certain as to why the engine lost compression or what caused it.


http://www.mediafire.com/?qzhjnjathjl
http://www.mediafire.com/?jmnmjfhdrwo
http://www.mediafire.com/?uhmtwelmmzv
http://www.mediafire.com/?o1coidkon4j

I know my car went lean while it was being tuned. After several pulls on the dyno, my car lost fuel pressure causing it to go lean.

Here is a thread I started a little while ago when it first went lean. I was trying to figure out what caused the problem but still have not got an resolution on that.

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/stock-fuel-pump-made-denso-873510/

My list of mods are in my signature

Any help would be great.

 

How lean? How much power were you making? What was the apex seal clearance? Looks like the apex seals were too tight in their grooves at the tip of the rotors. Were you monitoring oil temperature?

 

what was the symptoms befor it blew ?

 

I can not answer most of those questions the only one I can is the HP. My car was being tuned on a mustang dyno. With stock twins turbos my car made 290HP (15psi). Because I swithed to the BNR's I was hoping to get around 330HP @ 16psi. My last run was around 315 before it went lean.
I think the engine went because the of the fuel problem. I still do not know what caused my fuel pressure to drop off. I have since picked up a KG fuel system (lines, FP regulator, 1600 injectors), a fast IAT sensor, and I am thinking of replacing my fuel pump just case. Even though I have a WI kit I am going to pick up another one so it can be tuned with the AI. I also plan on ceramic coating my UIM,LIM, and my down pipe.
I have been doing lots of searching over the past few weeks and have found some threads that said they blew because of back firing, a short in the wire harness.

Obviously I do not want to have another rebuild, and now I am scared as ****. This has been my dream car for a long time, and I don't want it to blow again. I know they are not bullet proof but this is too much.

there are sooo many reasons why these engines can go. I'm just hoping to find them and address try my best to take care of them.
Please keep the ideas coming.

 

A lot of people like the 2mm RA Super Seals. They can warp in some situations, but truly they don't break... I am currently reusing a set of these RA seals after rebuilding a motor that had experienced severe detonation multiple times. Some claim that they wear housings faster. This is debatable. Broken apex seals destroy housings, so take your pick.

I'd replace the engine wiring harness, or at least examine it very carefully. Also pressurize the fuel system (use the diagnostic connector) to check for any small leaks.

 

I'll fill in a little....

The engine didn't blow in the common sense of the term. The seals were not broken or chipped. They had abnormal wear on the top part of the seal where it no longer provided a flat edge for a perfect seal and thus the cause of the loss of compression.

The lean-out conditions were varied from 11.5-12.0 AFR. It would only lean out when the fuel pressure was dropped so it was directly associated to that. Each time it leaned out, the knock sensor would pick up a little bit of knock before the throttle was let off.

1Revvin7, that was one of my theories when I looked at the engine disassembled but I don't have enough experience in these things.

Double_J, could you take some pics that show the wear on the top part of the seals as well?

I relinked the images for better access to members...






thewird

 

Place the apex seals top edge to top edge and see if there is a gap shaped kind of like a football. If so, if the apex seals where new when installed in this rebuild it would suggest inadequate lubrication which would most likely be a failing or failed oil metering pump.

As a side note, you should always run a little 2 stroke oil in the gas when ever you increase injector size.

Hope this helps,
Dan

 

The apex seals are slightly curved but difficult to see with the naked eye except for the bit of wear on the edge. You can shine light through on a mirror. This was another theory that we had and 2 reputable engine builders had suggested the same thing (to add some 2 stroke oil). But neither were 100% sure on the cause and thats why we wanted to hear what the community thought on the matter as we obviously do not want this to happen again.

thewird

 

This is also what came to my mind as I was reading this thread.

Guys, premixing is *very* important on modified cars.....

 

I suspect an oil metering/lubrication issue or the exhaust port was not properly beveled. If you went lean and detonated you would most likely have broken the stock seals. Also, how were the seals clearanced?

 

heck, I'll raise you one. Premixing is important on all rotary cars. Modified or not. Premix, premix, premix.

 

We recommend premixing on every motor we build at the shop. Remember the stock omp system was designed for stock power levels. With more power/boost, heat, pressure, and wear all increase significantly. The extra lubrication helps counter this.