Hey,

I would like some valuable option from some of our Rotary builders out there. I really hate the word guru since it's so played out by none guru, if you've put together more than 10 rebuilds, please chime in.

I purchase a used Pettit Racing streetported motor with about 5k miles on from a fellow member. The specs are brand 2 new rotor housings, 3mm seals, streetport, and the the standard stuff that goes with Pettit rebuilt.
Well, I pick the motor up a few days ago from a shipping terminal, it was shipped in a wood crate. When I got home I performed the poor man compression, you know, the three compression chugg per rotor. Both rotor had a nice even chugg when I did the test.

Today, I degrease the external part of the motor and see what I was really getting. I notice that on both rotor housing, there were buttons that said"void if remove" is this part of Pettit anti tempering seals?

I also cleaned out the intake and exhaust ports of some carbon build ups. I used some mineral spirits as a cleaning agent. When cleaning the front rotor exhaust port, I notice that on one of the rotor face, there was a good size dent on the rotor! Yes, I freakin dent on the rotor face. The dent is located between the apex seal and the combustion chamber area(the concave part of the rotor).



Same dent but different lighting.


http://s215.photobucket.com/albums/cc43/FD3S/

As you can see, the rotor has a dent that is about one inch long by 3/4 wide, there are no external marking/gouging/scratches? I have never seen this before! Was Cam at Pettit aware of this during assembly? It looks like that it would create an uneven combustion since it's adding some volume to the rotor face?

I do trust the seller, since he was willing to use an escrow for this transaction, and numerous e-mail and phone contacts. i will not reveal his name at this time because he's been contact about this irregular situation and he will be contacting Cam about this rebuilt.

 

That is a standard rotor

 

If this is a standard rotor, how come the other faces does not have this indent?

 

that dent is caused by a detonation or a severe ping.(the rotor is hollow under its faces)

i doubt they would have reused a rotor like that, but i suppose its possible.

 

the exhaust port does not look like it has been ported. is that just me. or am i wrong.

 

Yes, the motor is ported. If it's detonated, wouldn't the apex seal be damage or broken off. There's not sign of damage to the seals....

 

That is a fully stock rotor, I would be amazed if the other faces didnt have the "dent" as this "dent" is what makes a rotor high or low compression, if the other rotors did not have this indent it would be seriously high compression and also very unbalanced.
Every rotor that has ever left Mazda destined for a 10A, 12A, 13B, 20B or even 26B rotary engine all have these chambers on each face of the rotor. Because you cannot change the size of the displacement of a rotary (13B-26B is 654cc per rotor/housing) like boring out a piston engine. They use low compression rotors for Turbo engines and high compression rotors for N/A engines, the size or depth of the indent of the rotor tells you what type it is, smaller indent is higher compression for example.

 

Remeber that 3mm seals are more tolerant to detonation than 2mm seals. Also it it is hard to see what "dent" you are talking about other than the stock rotor concave on each face.

 

I understand that all rotor ever produce has a working chamber,and that chamber is located in the middle between the apex seals. This dent is located between the apex seal and the chamber. Plus the working chamber is much larger than this and has a exact or well define edge on it. The woking chamber has a dent that goes up and down between the seal while this one goes across the rotor and about 1 inch long.

"void if remove" seal

What is "501"


Can I please get some real builder to chime in on this.....

 

Are those the autolite spark plugs? I didn't know those work on a rotary? I can't see the dent so describe the dent as in measurement.

 

Yes that is a pressure dent from a detonation incident. That does not preclude reuse of the rotor, but some builders frown on it. It depends on how pronounced it is...it really won't change how the engine runs whatsoever.

And yes, that is pettit's version of "streetporting" the exhaust if you call it that...stock opening edge, stock width/sides, and extended D shape closing by about 1-2mm at most. Their intake porting, from what I have seen, consists of somewhat smoothing the factory castings and that is about it, not really changing the port shape/size whatsoever.

I would get those autolites out of there before use.

I would run it as-is provided there are no broken seals etc. You will never even know that it is there.

 

Thanks for responding to my S.O.S, call, and your words means alot. The dent is about 1/8 deep at the center of the dent, where the lighted and darken part is. As I've said, there are no gouge marks on the dent. The dented area in question look like it streched a bit, meaning the rotor natural machining lines (up/down lines) of the rotor looks streched in, meaning weaken rotor wall?

Is there a chance that this motor detonated and no one was aware of it? It would seem to me that I would have knock/dentonated hard in order for this to happen? I don't think that I'll be using this motor as it is, since I don't want to risk blowoing it, and causing **** loads of other damages.

What would be the repair cost in part to repair this damage, Pineapple seal kit $200.00, used rotor $?, and machining for 3mm seals $?

Thanks, Jay

 

Perhaps get in touch with Pettit and see if they know the history of the motor. It's very possible that the dent happened in a previous build and they reused the rotor, thus you'd be tearing apart a perfectly good motor.

 

Like RR say the dent should affect how the motor runs. Throw that motor in the car and have fun.

 

Have you used a dented rotor in one of your build before, and what were the out come? Doesn't it add volume to the combustion chamber and a late one at that.
How thick is the rotor material at that spot? I'm just worry that the rotor's aluminum is weaken from the dent and that it might fail during my time with it. Bang and the rotor will cause a huge mess......

 

I still say this is a standard rotor, like this one
http://www.3rotor.com/images/fc_rx7_...a_3rotor_4.jpg

 

I'm sorry for the typo but I meant to said a little dent on the rotor should NOT affect how the motor run.

 

[QUOTE=T2 Tsunami;7957483]I still say this is a standard rotor, like this one
http://www.3rotor.com/images/fc_rx7_...a_3rotor_4.jpg[/QUOTE

Have you ever touched or rebuild a motor in you life?, at lease reread the thread before you respond. The picture that you've link clearly show a normal rotor with a well define edge and chamber(vertically) shaped! The pictures that I have are smaller than the exhaust port and it's horizontal dent.

 

The rotors are cast iron and there is little chance you'll damage it further, unless it detonates on that face again.


Paul

ps. I don't meet you 10 rebuild criteria,

 

Here ya go

 

Normally a rotor measure 3.1x". Is that atleast 1 1/2" dent? If so that the first time I have ever seen one. Throw that sucker in the car and see how it runs.

 

The 89+ rotors are lighter weight than previous 10.5 and 11.5lb versions, but at a price...the material is the same, so they had to be cast thinner to achieve the lighter weight. The only other way to get lighter weight is to change the material to a lighter, more expensive one.

So detonation events can actually force the thin walls inward. IF you are running 3mm seals, this can happen and no one can even know about it, because nothing broke. IF it had been a 2mm motor, there is no doubt in my mind that they would have broken before detonation got this severe.

This is what happened here, a few strong knock incidents but the seals survived so no one was the wiser. Usually the dents are present on about 10-20% of used FD rotors, but they are barely visible at all. This looks like a more pronounced one but it should not hurt anything. Even if it does lower compression ratio slightly, this is not a bad thing, it makes that one face slightly less likely to detonate in the future (IMO). No material has been shaved off or missing, so the rotor balance/weight is not affected.

IF for some reason you won't be able to sleep at night because of this, then you'll need to tear it down and change the rotor. FD rotors go for $150-200 plus milling of $100-125. Then you'll require a new set of coolant seals at about $125, plus labor (if applicable) usually around $500. If it were me, I'd add onto the conservative (aka massaged stock) pettit porting while it was open, likely at a $200-400 cost. I dont know where you're at, but if you wanted to ship it to me I can make it happen for you in a couple weeks' time.

 

Thanks you kevin....There are only one handful of people who's rotary wisdom that I trust. And you are certainly one of them.
I paid $2200 shipped for this engine, and no, I won't be able to sleep if I just throw this motor in. With that said, I'm looking at $200 for the rotor, milling $125, and Pineapple seal kit of $190.00. Total of approx $550-600 for the repair?
I don't think that the seller knew of this problem and I don't see the reason to blame. The detonation might have occur while he had it or before the build I don't know. He said that he'll contact Pettit Racing on monday..

jay

 

i would just throw it in the car and enjoy it, but i do see how you could lose sleep at night...i might just be a bit nervous. hehe

 

bump, im the seller and am 100% sure there has not been any detonation in the 4.5k miles of use the engine has had. The car was wrecked but started and ran perfectly right up until i took the motor out. Ill be finding out more about this tomorrow