We have had this customer for several years and what amazes me is that the majority do not understand the complexities of our hot dry high altitude. Oh, they talk about it and smooth right over the issues that come with running a rotary engine in this climate.I get a lot of 'I understand', this is a post to get under your skin just a little bit. I have no problem poking the bear. My objective is to build motors that last, run hard, fast and start hot/cold when asked.
The motor in question is the one I am finishing up right now in the shop. This customer came to me several years ago after getting tuned by a local professional shop with a dyno. Last year we added improved oil coolers, moved the intercooler and provided needed cooling shielding to get fresh cool air to the radiator, that worked very well.
Heat rejection and the effects of proper fueling is not something that will just be fine. Yes, I am not happy this car came to me with a motor running on only one rotor, was it broken? Yes, we took it apart to find our more and most importantly to find out why it quit running.
This motor has only 5000 miles on it since it was rebuilt with a turbo added.
Let's get into it.....
The motor came out, everything tagged and noted, the first issue I noticed was that the turbo was not being held well on the flange, it was loose, just enough that it would move on its own, but I've seen this before.After a full pull down and the ultrasonic hot and ready, the story unfolded.
There was nothing broken inside, nothing. Just loads of carbon deposits, so much that the side seals, apex seals were stuck. This was due to a bad tune.
Too much fuel and not enough on deceleration to keep the apex seals from overheating. The rotor housings were scored on the edges, meaning that the apex seals were bending under deceleration and digging into the housings.
I cannot stress enough that the tune is the magic that keeps things together under load or does what happened here.
This was also a tune that only made 350 hp, pretty weak considering that this was a EFR 7063 with an AR of .92 internally waste-gated.
Now that we knew what happened and why, the components to make it right. We put in FD rotor housings, these are the best housings for sealing and wear and the exhaust porting was reduced for better flow than the large ones previous. Please note that the rotor spins at ⅓ the shaft speed, so flow at low rpm is very important for feeding a turbocharger.The intake ports all looked good, little polishing and go with it. A new oil pump, oil pan washers, all new seals, springs, gaskets and 0-rings, the motor all back together. now, one last thing.
In Colorado, not one rotary motor with a turbo on it should not be without heat shielding around the intake manifold, fabrication with metal and ceramic heat shielding riveting to hold it together along with the hot side turbo blanket. I have another bit of fab work to add, this shows what it should look like to keep heat away from the intake charge. We will also be adding in heat shielding to the -6 coolant line feeding the turbo.
This should be an absolute mandatory for every car with hot engine compartment temperatures. Adding hot air into your intake means poor performance, reduced engine life and isn't that hard to do. After years at the race track, we have the data to back this up.
Next, we get the motor in, fire it up and allow one of our chosen tuners to do the proper magic, this is going to make a bit more power safely and be a lot more reliable down the road.
Topics: Colorado Rotary Engine shop, 13b, Mazda FC Rx7