To be honest, the OP has no idea what he’s doing and it’s changing completely daily even though the car was supposed to have been torn down last week. Though having said that, the original post of this thread says GT or Tial turbos. Some of the highest powered Tial 770 cars (the biggest turbo Tial offers for the B5) have been stock pistons (Gearhead dyno’d 676whp, and D-shot dyno’d like 666whp IIRC), and there have been plenty of GT turbo’d B5 S4’s with stock pistons. If, at the end of the day, the OP actually makes 700+whp (though his clutch setup will slip well before being able to put down near that power, ask me how I know), I’ll buy you a steak dinner. Also, if you see my post #26, the only time I mention a specific horsepower I say 500-600whp, like 99% of the Tial builds make. If I were to personally build a motor that I was going to go well over 600whp, I’d almost definitely replace the pistons, if it were me. If I was going less than that, I wouldn’t replace the pistons, as the stock Mahle’s have proven to be reliable, and by keeping the stock pistons it takes out some of the other human factors that can make an engine build go bad (ie. you just have to hone the cylinders and replace the rings, rather than rely on the engine builder to correctly bore the block while keeping in mind correct piston-wall clearance etc). Of course, a competent engine builder shouldn’t have any issues either way, but for me it’s more of a ‘the less things that have the potential go wrong the better’, which keeping stock pistons accomplishes (on top of being cheaper and proven reliable).
OK, so if you were building a car to the OP’s (ever changing and very fluid) expectations, you would upgrade the pistons.
Granted this is a very odd thread/build all around. It has changed from ‘I have 770s’ to ‘what turbos should I get’ to ‘I’m getting something secret’.
Will be interesting to see if it ever runs. Wonder which car will be running first…this one, or guruman.
If I were building a car with the hardware listed in the original post of this thread (the original post doesn’t list a power level, it lists hardware [“GT’s or Tials”]), I would not worry about replacing the pistons. The stock ones would likely be fine in that scenario.
Just a quick update. I’m waiting for my coated pistons from 034 Motorsports. Once they’re ready the rebuild can begin.
JHM…what are they doing?
Sounds like RS6R
I told them what my goals are and they’re taking it from there. I would have paid double for pistons if I could have had them sooner. I know I’m being impatient but I’m getting so tired of waiting for this project to begin. Tomorrow is three weeks without my car now. Next time I’ll definitely buy a block and have it rebuilt instead of doing what I did here.
You are in for a world of hurt if 3 weeks bums you out.
I agree with this. Seems CV gave enough information to start a new conversation or to possibly look into a direction that people are not looking. Also if your pulling out the rods I agree it might be time to just do the pistons on pure principle. When your 100% over the stock whp I’m thinking it might not be a bad Idea to look at a piston or to investigate the proper piston for that hp level.
It just seems not much has changed in the B5 world since I left. People seem to be all over the place with there conclusions and theory debates.
While I certainly don’t know where the stock pistons give out I do agree that we might want to start to ask more questions before we feel comfortable at any level
Damn 034 is doing stuff for the B5’s now? Seriously JHM and 034 have been good shops for years. 034 has been the leader in the 5cyl game for a long time. I would feel comfortable with there suggestions and directions.
3 weeks with absolutely nothing done wouldn’t bum you out? I gave them a list of parts to buy for the rebuild - three weeks ago. They could have ordered the parts, had them shipped and started working on the engine by now. Instead - absolutely nothing has happened. That’s why I’m bummed out. Unreasonable?
lol
these builds never seem to be done on schedule. I think that’s what he was inferring. 3 weeks is nothing. 3 months is nothing.
At this point I’ve almost forgotten about the car. I’m working on a new business endeavor and the Audi is now on the back burner - in my mind. When it’s done, it’s done. Still, I’d like to see at least SOME progress every now and then.
Ask him how long his car has been down since he’s owned it ;D
New conversation and direction that people aren’t looking, what would that be? Aftermarket pistons? There have been aftermarket pistons for the B5 for probably close to a decade now. As for conclusions and theory debates, it’s interesting you make that statement in this thread, considering we’re going off of actual experience not any type of theory (as Jared said, he’s personally built over 20 motors and I cited some very high powered cars that successfully ran stock pistons [and I’m personally running stock pistons in my own GT build, though not high power yet]). If there’s particular aspects of the stock piston that are in question, other than ultimate strength, I’d love to have that conversation, but it appears that no one is wanting to.
Make no mistake, I’m all for being inquisitive and “question everything”, but it’s not like we’re breaking new ground here. Stock pistons have been used successfully in more big power builds than I can remember, and other than ultimate strength and possibly a different compression ratio (if one is looking for a different CR), I don’t see where any of the aftermarket pistons for the B5 have improved on the “design” of the stock piston. As Jared noted, from a metallurgical standpoint, the stock pistons are actually better suited than some of the aftermarket pistons.