So I was informed by a guy that knew the previous owner of my car that the turbo was making a whining noise and sounded like a supercharger.

What's this an indication of?

He keeps telling me to get an s5 Turbo because its way better, but I see no reason to if I can port the wastegate on this one and use it.

Rotary >Pistons

 

Could be a bearing doing out, they definitely aren't supposed to whine. s5 turbos "flow" better, the wastegate is better and the manifold is better. But you could just swap hotsides and manifolds and be the same. Otherwise s5 and s4 turbos are exactly the same.

 

A bad bearing would require a complete rebuild wouldn't it?

I'm still not sure what the best route to take is as I'm trying to save money by using what I have.

Wondering if I should-
A) get this one rebuilt
B) buy an s5 turbo/ex manif that doesn't need a rebuild (which is a gamble imho)

Rotary >Pistons

 

Bearing play allowing one or the other wheel to contact the housing (axial or thrust), or damage to the compressor wheel blades that makes them "chop" the air.

 

Rebuild > Taking chances on another 25yr. old turbocharger.

 

You're the expert here on helping with save money while keeping a safe reliable setup.

What do you think is my best option?

Rotary >Pistons

 

OK guess I didn't have to ask rotaryresurrection that one.

I know bnr does rebuilds, I don't really know anywhere else.

With the problems it has, would it be considered a rebuildable core?

What would've caused it to have these bearing problems?

Sorry if I ask lots of questions. Its how I learn.

Rotary >Pistons

 

Having not seen it in person, I can't say yes or no. But, as long as the blades look intact and the housings aren't destroyed then usually yes. Whatever can't be re-used will be replaced. I just had one rebuilt and after needing a new compressor wheel total build was $405 from a local shop. at that price you may consider an upgrade from BNR for a couple hundred more. Either way, it will be cheaper in the long run to get one rebuilt than continue replacing old worn out ones as they fail IMHO.

 

Used s4 turbo for $75-100 that's in hopefully better condition than yours and go on with life. S5 turbos are nice but they are harder to find and command twice the money, and either one can make basically the same power since they are the same turbo except for the turbine housing.

 

If there is any blade damage to either compressor or turbine wheels, then it's not rebuildable (at least, not without those same parts harvested from another HT-18 turbocharger). For it to make a loud whining noise it seems like a wheel would have to be rubbing against something on one end or the other (most likely the compressor).

I've also had bad luck with rebuilds/hybrids in the past (although admittedly I never used BNR). The hybrids I had built for me were done by a shop in Nashville called "Turbo Auto" and he was rebuilding the stock turbos and putting on bigger compressors. From what I could tell it was the worst of both worlds...slower spool than stock, but still restricted power output less than a full T4 turbo setup. I also had problems with the turbos leaking oil, smoking, and the nuts coming off the compressor wheel and letting the turbo destroy itself while running.

Really the stock hitachi turbos (FC or FD) are not really meant to be "rebuilt". There are kits that exist to rebuild them that come with bearings and seals, and I've rebuilt a few. But the bearings and seals are only half the issue. Sometimes there is compressor or turbine wheel/shaft damage. Sometimes there are cracks or other wear in the bearing housing. Often there are major cracks in the turbine housing internal scroll. These things see SO MUCH HEAT and they are SO OLD that they do not make good candidates for rebuild in many cases.

The "proper" way to refresh a turbo is to buy a brand new CHRA (center housing rotating assembly) from the manufacturer, and install your original housings onto it. But I believe you can't do that with the old hitachi turbos, and they don't use standard garrett type parts that are available today.

I know for the FD's, BNR had to resort to using other turbo parts that are cheaper and more readily available today, and machine the stock housings to accept them. This allowed for new CHRA's but still retains the stock housings for original fitment on the car using all the original manifold and plumbing.

I don't really know what he does for FC's. They're not usually quite as bad off as FD twins, but I'd bet he still has issues finding enough good parts to build a nice stock turbo out of.

 

Most of the really nice condition turbos I've seen go for $250 , guess I'll have to keep a lookout.

I still kind of want to get it rebuilt though because I'm worried I'll buy another and have it be bad too.

Rotary >Pistons

 

Are you positive it's the turbocharger? Try taking the belts off, run it for a few seconds, shut it off. If the noise went away, you found your issue. My front water pump pulley was whining pretty bad making the same noise. I thought it was a bearing or something going bad as well

 

The way I look at it I'd rather put $1000-1200 into a full brand new T4 turbo setup than $500-650 into a rebuilt stock turbo. I can't see putting any actual money into a stock turbo setup.

 

I don't have a lot of money so I'm trying to keep the car close to stock power level and eventually Max out the power of the stock turbo.

I've never owned a turbo car, the fastest car I had was my na s4 which was probably 140-150 HP to the wheels at best..so needless to say I'll be happy with the power of the stock turbo, plus it'll give me time to adapt to having a turbo car. I don't want a 300whp turbo on there right away.

Rotary >Pistons

 

Like mentioned, you can take your chances with the classified section turbos. I bought my S4 turbo for a whopping $50. Granted, I sent it to BNR immediately because I chose to run an upgraded "stock" setup. But if you can find a deal like I did, it's only $50 bucks to experiment.

Good luck.

 

Which is exactly why I wouldn't put 450-650 into a stock turbo.

 

So, have YOU heard the turbo making any noise?? Getting info from a third party makes little sense.

 

No, car hasn't run since I bought it. I need to get an ecu, afm, and intake-those parts were sold off the car before I purchased it.

I wish I could just buy a brand new stock turbo but I don't believe anywhere sells them.

My brother got a new turbo for his old 91 eclipse relatively cheap, a big 16g . Whatever that is.

I've seen people put a 20g on an rx7 I think but I honestly know very little about turbos that's why I was going to just get the stock turbo.

All I know is all the cheap turbos I see on eBay are likely junk if they're 250 brand new.

Rotary >Pistons

 

If a brand new turbo were available from mazda, I doubt you could buy it anyway. FD twins are around 2800 retail...I can't imagine an FC turbo being less than about 1800.

Usable condition used s4 turbos are not hard to find man, I think you're making this harder than it has to be.

 

I have a bad habit of doing that, I think it's mostly due to how paranoid I am tending to over-analyze everything and think the worst.

Rotary >Pistons

 

Look, I deal with a lot of people, cars, projects, and goals. Let me give you one of my observations:

People go into an rx7 project thinking they're going to build the last/best one on earth, they want to build it once and drive it for 10 years. Well, that's a good mentality to have, but these cars usually do not work that way. Plan for the intermediate term, not the short term or the long term.

If you were to put a brand new stock turbo on, it would probably be worth more than the whole car, but it would not be any more reliable than the same car with an original turbo in decent condition. Think about that for a moment.

You WILL be tearing back into this thing in a year or 2. Trust me. Either you'll want to mod it more...or you'll have some minor repairs or issues to resolve that were unforeseen. Or you'll blow the engine. Or you'll want to paint the turbo compressor. Or you'll find out that you have boost creep and need to port the wastegate. Or...

You get the idea. Don't keep saving and worrying over how to build the thing, while staring at a non running car. Take the shortest reasonable path to get it running NOW, and worry about the other issues as you go afterwards. There is always another "well it would be a good idea to buy this before I build it" and if you keep at it that way (assuming you're not rich enough to buy it all at once) you'll never get it running for the next 2 years.

I would inspect the turbo you have. If you can't see, feel, or hear anything wrong with it, then put it on and fire it up, and see what it does. Worst case you're on the hook for about 2-3 hours of labor to swap to another one later. Take the money you were going to spend on a rebuilt turbo and put it into the engine build or the other parts you need to attempt to start the car.

If the turbo turns out to be bad you can still possibly drive the car gently, or at least start it regularly and work on resolving the other issues that WILL crop up once you get it running. Then you can decide whether to replace the turbo with a rebuilt unit or a used unit, or to mod the car more with a bigger turbo setup.

 

Thank you for your insight, I've been wanting a turbo rx7 for almost 10 years so trust me I'll get the job done.

I just know the difficulty of everything will be higher than it was on my na, but anything can be done if you put your mind to it

Rotary >Pistons

 

Remove the intake piping and inspect the compressor. Check in-out/side-to-side movement. If you can make the wheel contact the housing, the bearings are worn out. If pieces of the wheel are missing, then its obviously time to replace the rotating assembly. This can be cannibalized from any S4 or S5 turbo or you can just use the entire other turbo to make things easy.

Despite the negative opinions in this thread, rebuilding a turbo is not very difficult, and not very expensive at all. A standard Garrett rebuild kit can be used, and then it can be balanced by just about any turbo shop. The grand total will be in the $150-$200 range. Compressor nuts generally come off because people don't use loctite or don't correctly torque the nut.

edit: If the rotating assembly (turbine wheel & shaft, compressor wheel, and compressor nut) end up checking out, then the turbo can be rebuilt without rebalancing. All 3 pieces just need to be marked well before disassembly, and then lined back up when assembled. This means the only thing needed is a rebuild kit, which is less than $100.

https://www.rx7club.com/2nd-generati...hybrid-959045/

 

I had a leaking BOV that made a whining/whistling noise. I thought it may have been the turbo bearing dying but when I replaced the BOV the noise went away. I would check to see if you have a small boost leak somewhere, especially around anything that has a silicone (e.g. FMIC coupler) or rubber gasket.