Turbo Internal Mods

rodavo · Post by **rodavo** » Fri Jul 01, 2005 6:56 pm

Anyone know if it is possible to modify the internals the the Piazza's turbo to gain some more grunt. I was thinking maybe larger turbine wheels or a ball bearing upgrade or something like that. Anyone know??

Rodeobob · Post by **Rodeobob** » Wed Aug 24, 2005 4:25 am

I bought an RHB5 off a guy last week. Its a Subaru one with the Piazza exhaust housing on it. Well i actually got both, ive got whats left of the Piazza turbo with the subaru exhaust housing sitting on it. The Piazza one doesnt look to be in too bad condition so i might take it down and see how much to reco or reseal it.

Comparing the Subaru one to the Piazza turbo its got a bigger compressor wheel by the looks of it.
The Subaru exhaust housing hits on the Piazzas wheel and wont bolt up.

That poses the question.
If you got a Subaru RHB5 core an put a Piazza's RHB5 turbine wheel on it, using the Piazzas exhaust housing and the Subarus inlet would you get a better turbo.????

Keep in mind that the compressor wheel is fixed to the shaft. The Subaru uses a 3 bolt flange to mount to the manifold.
And that the Subaru had a bolt on flange for the compressor inlet which is a way better setup than the Piazzas rubber squish doo hickey.

Might be interesting to explore.

Cheers. bob.

GeminiCoupe · Post by **GeminiCoupe** » Wed Aug 24, 2005 9:24 am

But is it a cost-effective excersize and will the performance gains be feasible? I think thats the main problem this poses.

Reconditioning turbos generally costs around 1k, include machining of the housings to accept the larger wheels [eg. the comp wheel off the liberty] and the cost goes up slightly. For all that, you would still be using an outdated compressor wheel design. While it might make some gains it probably wouldnt be worth the increase on lag.

Unfortunately for Piazza enthusiasts more power/boost lies in a different turbo. The Garret T28, especially in S15 ball bearing SR20DET trim seems to be the perfect hypothetical match.

Nick-

Rodeobob · Post by **Rodeobob** » Wed Aug 24, 2005 2:22 pm

Im not so sure about how the wheels and housings are matched in the RHB5 turbos. Id have to find out. By that i mean can you buy wheels individualy. Or do you have to buy a core. Can you buy an bits for the core, seals and bushes/bearings etc.

(i just remembered that i had it the wrong way around the shaft is fixed to the exhaust wheel.)

What i meant was

A Piazza spec exhaust wheel and shaft and a std Piazza exhaust housing. Bolt on a Subaru spec compressor wheel and compressor housing.

Ive got one in the shed the only difference is that it has the subaru wheel in the piazza exhaust and there is extra clearance. It will work and run the car but not as good as it could.

You can buy the Legacy spec RHB5 for about the $200 mark in good condition, ive seen a few on EBay lately. Theorticaly it would be a cheap upgrade provided the compressor being bigger doesnt make it too laggy.

I will take some pics of the two turbos and post em up.

Cheers. Bob.

GeminiCoupe · Post by **GeminiCoupe** » Wed Aug 24, 2005 7:17 pm

I think im begining to follow what you mean now, basically its fit the bigger comp wheel and compressor housing off the Liberty onto the Piazza rear right? Failure to do it this way would mean modifying the manifold and dump pipe and at that stage im not sure it would be such a good "budget" alternative.

Id still be inclined to use a Garret turbo though. T03's can be had for as cheap as 250 in good condition. It will give a shitload of lag but the top end rush would be unbeatable. T28's arent exactly expensive either, round the 400 mark for a good one. Only downside is the cash outlay to modifying the manifold and dump.

The IHI VF series off the WRX STi's could be a good performance alternative...

Nick-

Bugle · Post by **Bugle** » Thu Aug 25, 2005 12:41 am

Skyline RB20 ballbearing turbos are the best

Actually feel a kick when boost comes on, and no lag at all..

Makes a joke of the standard turbos compressor wheel

Rodeobob · Post by **Rodeobob** » Thu Aug 25, 2005 1:25 am

The only trouble i can see with the Subaru Hybrid RHB5 might be a bit of lag. The Piazza exhaust wheel is bigger than the Subarus and that has to spin the Subarus bigger compressor. But it should hold a higher boost, in theory it should hold boost till redline. But aent the injectors ar full cycle at 15psi?? you can get that from the std turbo cant you???

I doubt the difference is that much Bugle but it would be pretty close with the Subaru turbo. But then how big is the RB20's exhaust wheel??? thats what makes it spin up.

I should have some pics up tomorrow night.

Bugle · Post by **Bugle** » Thu Aug 25, 2005 1:36 am

Haven't removed the turbine housing off my old Piazza turbo, blown turbo that one came off didnt come with a turbine. But looking at the outlet hole and the size of the housing it look to be similar size to the RB20 one.
The ballbearings and ceramic turbine would help it spool. It can even get to 10psi just revving it in neutral. Vidlink

Rodeobob · Post by **Rodeobob** » Thu Aug 25, 2005 1:43 am

Ceramics like to spin.

Yeah i figured that it was stuffed coz the shaft poking up thru the middle is supposed to have the exhaust wheel on the other end. lol.

You is a nasty man. lol. Poor free revin Piazza. lol.
Wheres the noise????

Cheers. Bob.

Bugle · Post by **Bugle** » Thu Aug 25, 2005 2:04 am

Yeah snapped the shaft just past the bearing!
Seems to happen a bit with these turbos.. The rb20 turbo shaft is heaps thicker.
It's got noise you might not have the right audio codec installed for it?

Rodeobob · Post by **Rodeobob** » Thu Aug 25, 2005 3:45 am

Nah hang on i might try it with the headphones on again but with em plugged in and the volume turned up. lol.

rodavo · Post by **rodavo** » Thu Aug 25, 2005 10:58 pm

Bugle, is the T03 off an R32 Skyline GTST or is it something else? I have read that the R32 ones are not ball bearing and that they are T28's but I dont know how accurate this is. Do you have any part numbers on the turbo or photos of the housings you could show??

Also, how is the car running with the larger turbo?? That video is awesome, I cant believe how quick that turbo spools up!!! Seems like the engine just wants to rev!!! Does it run lean up high at all, what about in the rest of the rev range? Us Sydney guys have to meet up soon and go for a cruze!! I am sick of not seeing any other Piazza's on the road!

Dave

Bugle · Post by **Bugle** » Fri Aug 26, 2005 12:49 am

Yeah off an R32. Definitely ballbearing pulled one apart after it shat itself from the oil line getting blocked up. Only part number I think on it is "16V" on the compressor housing. They're called a T28 sometimes because I think the wheels and housings are only about the same size as a T28 but it has a T3 flange so most refer to them as a T3.

Seemed to run pretty good but it kept blowing gaskets. Probably because the bolt-on adaptor plate I made has some thin bits between the inside and outside. Going to make a steam pipe manifold before I put the car back together.

Yeha was pretty surprised to see boost revving in neutral, couldn't get any boost to come on with the standard turbo!

According to my jaycar air fuel meter running off the standard oxygen sensor it stays in the rich region up to redline, that's not too accurate though could be way off the optimal ratio. Have to get it checked on a dyno.

Gotta get mine running before i can cruise, waiting on some parts so I can stick it back together.

WA Piazza · Post by **WA Piazza** » Wed Sep 14, 2005 1:24 am

yeh hey guys
With my piazza ive upgraded the turbo to a T03 its not to bad but its pretty good for a turbo that fits straight on. I have even ran my psi on 18 and it sound quite nice but ive just adjusted it back to 12psi its still beats my mates R32 skyline which is pretty good

lol

So if you are looking at upgrading the turbo without modifying the manifold and that its a better buy for turbo.
Oh and ive never really thought of that idea on changing the spools from turbo to turbo. Ull have to keep in contact about that id deffenately like to hear the end result on that.

Cheers guys