Just thought I would share this as it may help others down the road....

My recently single turbo converted fd blew up after a month of driving it.

Compression on the engine prior to conversion was

First rotor

93psi
95psi
90 psi

Rear rotor was

89psi
91psi
93psi

At 247 rpm stone cold

All seemed good to go for a few years yet.

After a month of driving and with a tune running 15psi the car was behaving very well indeed.

I took the car out and whilst in second gear and accelerating with about 50% throttle down a hill I heard a bang and the engine shuddered at which point I pulled over and she died.

Compression test once back in the garage showed

Front rotor

105psi
107psi
99psi

Rear rotor

0psi
0psi
0psi

She was toast

Boost was in around 6psi is at the time and the engine was warmed up fully.

I opened up the keg yesterday and found the rear rotor was destroyed.

Two apex seals were destroyed

Chunks were embedded in the rotor and the housing has 3mm deep gouges in it for the most part all the way around. The rotor apex seal slots were bent and deformed and were an absolute mess.

On inspection I found ( for what appears to be a relatively new build in Japan where I bought the car from ) a lot of wear to the bearings. I fact some of the worst I have ever seen.

I inspected the rotors and noticed that the rotors are completely different.

One is stamped A and one is stamped G.

The g one has all kinds of light weight machining carried out to it whilst. The front rotor looks stock.

I always had vibration from the engine but out this down the the solid motor mounts that were installed but on reflection this could have been attributed to it also.

I have no idea why they used these rotors at all. I assume it was a quick build just to sell the car and they just used whatever parts they had laying around that looked serviceable.

Long story short I'm now into a full rebuild and need irons, housing and rotor plus a build kit.

Charlie.

 

Yeah, I just read somewhere youre supposed to stay within 1 letter of each other. Sorry for your loss.

 

Yeah, I got spoiled with a heavy, but balanced 8.5:1 rotating assembly in my TII. No problems with 8,500 or 9,000 rpm rev-limit (except housing/apex seal wear from 3mm seals so I put it back down to 8,000rpm).

I tried 9,000rpm rev-limit on FD with stock Mazda engine (lighter 9:1 rotors) and it didn't last long before a rotor contacted the side housing and stuck a side seal down.

I am expecting to see rotor weights at least 2 letters apart when I take that motor down.

FD will get a dynamic balance and the rev-limit will stay at 9,000rpm (it was really nice for stretching 2nd and 3rd gears in the auto-x, hillclimb, kart track racing I do).

I might have to pick up a set of newer FD rotors as I hear they had a larger side clearance from the factory (racing class only allows rotating assy. balance).

 

Yeah my engine was a 99 and the rotor looks completely different. It has machining work done to it from factory.

After a varsol bath today I found the front cover was cracked to an unbelievable level too. I have no idea how it is still one piece!

Check out my Instagram for the pics of the tear down.

@scotiatint

 

Those cracks on the front cover are normal and is reusable. The engine detonated and blew and is unrelated from the rotors being out of balance, that would only cause bearing wear since it wouldn't be on the extreme side.

thewird

 

It just doesnt make sens as to why it would detonate though.....I wasnt pushing it at all and the AFR were all within spec.

My target vs actual afr was spot on at around 13. What else could cause det to that level to cause this?

I was tracking the car the week before and it was working great. Bad fuel?

 

Could be timing, intake temps, or trailing split.

 

Agreed,

Timing was good. I had just set it up inline with the adaptronic manual.

Intake temp was solid at 34*C

Trailing split was unknown at the time as I couldn't see the data....

 

According to haltech, anything under 10* split in the boost areas is safe.

But after going back and reading your thread, it looks like its from mismatched rotors. Like i said earlier, your supposed to stay within 1 letter of eachother.

You basically have the heaviest rotor (A) matched with a very light rotor (G).

I think it only goes to E though. Can you post pics of the letters you found?