DrTurbo

I have been looking around on this forum for a while and found some pretty useful info. I'm ready to get involved.

I am a former Garrett turbo engineer with lots of previous experience with Miatas and turbos. My wife and I have been hot lapping our 99 Miata with NASA for 5 or 6 years now and have had a blast. Miatas are great track cars right out of the box the way Mazda created them. But, after five years with R-compound tires and some racing beat sway bars on a completely stock drive train, we are ready for some more power. Time for a turbo. I am hoping to gather the wisdom of this forum to find out what works best. Hope you guys (and gals) can help.

By the way, I don't just plan to poach info without contributing. I engineered and built a complete custom turbo system for my FD Rx-7 so I have a wealth of experience to bring to the table. Let me know if I can help anyone out.

Thanks,

Dan

y8s

iTrader: (8)

you're late/we've been expecting you. jay kav is around here somewhere too.

welcome to miatayourjob.net

Rafa

iTrader: (22)

WOW!

This Board keeps getting better and better!

Now, if you'd be so kind to post your location below your avatar and post some pics of your car.... or ban!

JKav

iTrader: (1)

Yeah, Dan's RX-7 is pretty badass.

But what's this? I'm the third reply to a "Hi, I'm n00b" post and nobody's flamed him yet? Weak.

y8s

iTrader: (8)

he was humble and didn't ask a stupid, obvious question. what is there to flame?

oh and he's got cred.

JasonC SBB

Cool. Here's a Q.

Does the GT2860 really have a massively more efficient turbine than the GT2560? (as per the Garrett site).

JKav

iTrader: (1)

Nah, put the screws to him. I insist.

JKav

iTrader: (1)

JC, the peak efficiency is higher. Those turbine maps aren't very useful IMO since they don't have speedlines. Or efficiency, other than the peak. That, and it is very hard to map a turbine repeatably (hint).

But seriously, let's get to flaming Dan.

sixshooter

iTrader: (12)

Welcome, sir.

Now post some Miata pics and add your location to your details.

I'd like to see the FD pics as well.

Sit down and stay awhile...

JasonC SBB

OK I'm dense, what's the hint?

Oh, Dan better answer the question.

patsmx5

iTrader: (16)

I took it the hint was that the maps aren't set in stone as it's hard to repeat and get the same numbers. Gives you a limited idea about the turbine I'd suppose.

Oh have I got a good question for a turbo smart person- Does a little bit of "flutter" hurt anything? My GT3271 will flutter at low boost before the BOV opens. Does that matter?

Oh yeah, NEWB, read the faqs and stickies before you start asking about ebay turbo kits and how many boost you can run.

speed_racerx

welcome sir, hope you enjoy your stay

levnubhin

iTrader: (30)

Or ask questions like "how much boost can my built motor take" without telling us what turbo you plan to use.



Excelllent question Pat, mine does the exact same thing sometimes.



Welcome aboard DR, +1 on pics of the FD.
__________________
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote

DrTurbo

Thanks for the warm welcome (except JayKav).

Rafa, I'll get my details info updated tonight - please don't ban me until I get a chance to do something really annoying.

JC, unfortunately, I have to agree with JKav's answer to your question. The turbine maps they post on the Garrett site are not of much use. The are a rough curve fit through the peaks of the speedlines. Peak efficiencies and flows do give some point of comparison but what really matters is properly matching the turbine to the compressor. Without going through that exercise, you don't know where the turbine will really operate. The maps on the site only provide "best case" operating conditions.

For those who are interested, I will post pics of our Miata and my FD very soon.

m2cupcar

iTrader: (5)

Yes, welcome. To validate your identity please answer the following.

Q: According to Garrett, under what circumstance should a restrictor be used with a journal bearing turbocharger?

DrTurbo

I am not aware of any restrictor requirements for a journal bearing turbo but a restrictor is recommended for ball bearing turbos if your oil pressure is above 60psi.

DrTurbo

Pat, the flutter you are hearing is compressor surge. This is an oscillation of flow through your compressor when it is throttled as the intake closes. The durability concern associated with surge is that the flow oscillation can put a large oscillating axial load on the rotating group which must be reacted by the thrust bearing. This can be very hard on a journal bearing turbo which used an hydrodynamic thrust bearing. If the thrust load is enough to collapse the oil film, you get metal-to-metal contact which causes thrust bearing wear. This is typically not a concern for ball bearing turbos since the ***** react thrust load. That said, mild surge like what you are describing is typically not problem even for journal bearing turbos. Sorry for the long winded answer - I'm a detail guy.

patsmx5

iTrader: (16)

Thanks for the explanation. As for oil restrictors... I'm running a .070" restrictor on my GT3271. I don't have a "real" oil pressure gauge, but I'd imagine it's around 60 or so at cruise and 90ish by redline. If these numbers were correct, would a restrictor be warranted? Or even better: Would a restritor hurt anything? I've seen a lot of people run a restrictor on journal bearing turbo that had premature oil seal problems in the past that they contributed it to not using a restrictor.

m2cupcar

iTrader: (5)

pass (according to garrett guidelines)

I am curious like Pat regarding higher oil pressures. I can't see the harm with higher pressure in a journal bearing. It seems that the more oil the bearing gets, the better- providing it doesn't cause seal issues.

pbmiata

Dr. Turbo! With a name like that you can expect to get a few tech questions! I'm really looking forward to you future posts.

Welcome!

I wonder- has anyone with the Doctor's background ever evaluated one of those China chargers I keep hearing about? I mean, really took one part and evaluated the tollerances, metalurgy, design of the vanes etc. and compared it to the Garrett?

It would be pretty neat to have a (turbocharger) engineer's perspective.

Dr. Would you be willing?