Rotary Engine REbuilds | Getting it right
Rotary Engine Tear-down process and understanding what went wrong.
The number of FD’s still on the road or in the garage being prepared for road / track use is still very strong. These cars are seeing a resurgence in popularity. If you haven’t driven one, you should.
Here we have a great car that had a motor failure and because of the nature of getting rebuilt motors via online with Covid presents some realities that none of us want or need. There are a few shops that are not doing their best to represent the rotary engine. We strive not to be one of them. If you love the rotary engine, you understand. This is more than the almighty dollar.
This motor came out of a 1992 JDM FD Rx7, yes it is an 1992 model.
First, the customer spent some time with us to understand our mission and take a look at our (very small) shop. The mission is to provide rebuild services to a few, select customers that choose the rotary engine because of its power, lightweight and history. If you are looking for the lowest price, we advise to look elsewhere. We do quality work, with the right parts that meets our standards and expectations. Nothing less.
At first look, this motor was running well earlier this year and the owner said, he heard a click and the power dropped dramatically. I believe this. I have heard apex seals break under load. Years of experience gets you the real understanding of what makes these motors so wonderful. Once you have had a properly built motor and put many miles on it, you can feel, hear and know when something isn’t right. If it feels wrong, do not keep driving it.
These are really tough motors, the sludge found in the oil was also in the cooling jackets. Someone at some point put stop-leak in this motor. Never put this crap in a rotary motor, it will develop ‘hotspots’ and it will lead to your motor blowing up. Not if, but When.
My guess is that this previous owner had a radiator leak and took the easy way out to repair it. The current owner got 2 solid years of driving this car and moved from the east coast to Colorado.
This Yellow Mica Mazda Rx7 is a beautiful car and deserves to be driven well. A lot of factors lead up to motors breaking, including timing, gas in tank, boost pressure, air intake temps (and even fuel and water... a hot motor eats up the built in margin for detonation).
If everything is perfect you can tune above 12:1 at sea level, but from what I see most people with a reliable "street" car running high 10's to low 11's and even lower for track use. Remember, at 5000 feet above sea level, pushing towards detonation must be avoided.
Don't forget that we have to use fuel to cool the long compression chamber of the rotary engine. Using conventional piston thinking is going to get you in trouble.
The reality is that here we are with an engine failure of no fault to the current owner, it is frustrating as the previous owner could have had proper maintenance / repairs and avoided an early retirement for this motor.