Some Piston Pics..

[chrisman]

hi guys,, for the guys who havnt heard,, we have noticed that on one of the forged pistons has had some of the piston burn away..
i dont want to worry people, mainly because it was probably our fault.. but i do want to share our experience with what happened in our case..
we still have compression in the cylinder,so,, the piston has not failed--but this is something to look at..
its cause is still speculation,, it most likely is an injector that is not injecting as much fuel as the other inj.. so i will be checking/flow testing all of the injectors..
anyway,, i/we did cosider to remove these "sharp edges" from the pistons before we installed them.. but,, because of the near perfect balance from ross,, we decide NOT to undo thier work by removing the material in question.. ALTHOUGH-on the original toyota piston,, toyota did see fit to remove the same "sharp edge" on thier piston..and, i have previously removed similar shrp edges on other pistons to avoid getting "hot spots" that could cause pre ignition..
anyway,, hers a pic of the orig toyota piston--it may be a little tough to see,, but you can see where toyota removes a little material--right by the valve reliefs on the edge of the piston..by the way,, the piston next to it is a cosworth piston for a 2jz--suprisingly the pin hole dia. and piston height are almost interchangeable--also, the bore is alsmot the same,, and there are 2jz pistons you can get with an 87mm bore.. all very interesting..

 

[Zuffen]

That's interesting.

I looked at that fine piece of material when I first opened my piston set and thought it looked a little too thin to stand up to much work.

Do you plan on removing it from all the pistons?

 

[chrisman]

yes,, i dont mind taking the pistons out.. it wll give me a chance to look everything over.. we are planning on turning up the boost, pulling some timming, and getting some bigger numbers.. im figuring that the rods will handle 700-750.. we will see.. knowing rdm,, he will want to try and get even more hp--but i dont think the rods or trans could withstand that much hp for to much time.. but,,?
we have one more set of pistons for the corrolla--i will also remove this from those, which i havnt assembled yet..

 

[rdm20fan]

I think the quality of the piston is just as good as any. I wish ross would have followed davids piston, mold a little better, and removed this material, as in the stock toyota piston.

 

[Lextreme II]

Ouch Bob... i will contact Ross about this.....

 

[chrisman]

remember-- i dont want to worry people about these pistons.. the pistons damage in this case was probably from an injector not flowing as much fuel as the rest--BUT-- this pic does show the first signs of what will happen to these pistons at extreme temps..

in other words,, if i were to use these pistons in a race only vehicle-under severe conditions, i would definately remove the thin material in question because a hot spot on a piston can cause problems..

 

[rytherwr]

Remove sharp edges

I believe very strongly in relieving all sharp edges on pistons for the obvious reasons.....looks like a lot of sharp edges on those pistons with huge potential for hot spots causing detonation. Smo-o-o-o-o-o-th them babies out....:veryhappy

 

[rdm20fan]

I believe very strongly in relieving all sharp edges on pistons for the obvious reasons.....looks like a lot of sharp edges on those pistons with huge potential for hot spots causing detonation. Smo-o-o-o-o-o-th them babies out....:veryhappy

I agree. Chris & I thought about relieving it originally, but Ross had those things balanced to some crazy tolerance of one another. I wish they had balanced them with the edges removed.

This did only happen on one piston, so an injector may have been flowing less then the others.

Wish is didn't happen, but what can you do? atleast this give you guys who haven't installed the pistons yet something to look at before installing your.
as if you didn't have enough to worry about! :bigeyes:

 

[rytherwr]

Yes, Sir, and believe me, I appreciate. Still in the process of putting everything together on my 2uz and this is good stuff to know. I think I have it a little better than the configuration of the piston tops you have as there aren't any thin areas on my 2uz's as there are on yours and I smoothed out the other stuff. Pictures at 'Coating Internals' under Engine Modifications thread by Lextreme. These are after I had them smoothed and coated....you can see a pretty big difference between them. Many thanks for keeping us up to speed.



Wayne

 

[Zuffen]

I was looking at my stock pistons on the weekend and noticed the nice sculptured section where Toyota had removed that piece of material.

I never quite understood why Ross needed a bondo sample of a piston when an actual piston would have removed any risk of inaccuracy?

 

[chrisman]

yes,, those sharp edges can become a problem..i also wish they would have removed them--only because i will remove them myself..

but i want to mention again that what happened to that piston was our fault--or rather a faulty injector.. none of the other pistons had the same symptoms.. the sharp edges on the piston were the first part of the piston to fail.. BUT, thats how making a fast car is.. you keep fixing the "next weakest link" in the chain.. in other words,,"things will break" and eliminating weak points will allow you to make more and more power..
and-hopefully,, what i learn, or my experiences will help guide people..
one thing ive learned from this is that even though your tunning your car for a good AF ratio--doesnt mean that all the cylinders are working equally.. i will flow test all the injectors i put in a serious car from now on..especially used injectors.. there is no reason to take a chance on getting a piston hot..

also.. i was able to get the engine apart a little more over this weekend,, and looked at the used bearings that we had used..they still looked great,, and i see no signs of detonation anywhere..quite a nice surprise..

 

[rdm20fan]

Chris, If Ross had relieved the piston, the bad injector would have caused a lean condition, and probably blown out the head gasket (which all happen) but do you think the piston would have survived, and be able to be reused rather then us needing to reorder a new piston?

i was able to get the engine apart a little more over this weekend,,

Listen to this guy!
Get any help did ya?
Do it all yourself did ya?

Throw me a fricken bone here!

 

[WDoherty]

rdm20fan, do you have a dyno sheet posted for the car?

 

[rdm20fan]

I'm pretty sure chris has it. I think he posted it in a thread. I'll look for it, and try to repost.

 

[SC400TT]

Bob, did you check with ROss about the possibility of them grinding off the edges of the new sets to anyone that wants to send them back for that purpose? They could then re-balance them to high tolerance...If so, cost to do so and time?


Ryan

 

[rdm20fan]

rdm20fan, do you have a dyno sheet posted for the car?

Found one.