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Old 10-15-2013, 06:24 PM   #1
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Default What happens when you fit too big a compressor wheel?

I am thinking of converting my td04L-13t to a 19t is this too big in relation to the turbine? what happens when you increase the size of the compressor without increasing the turbine will this lead to any problems do I need to port the wastegate or is that just for boost creep?
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Old 10-15-2013, 06:48 PM   #2
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is this the 3 bolt inlet subaru 13t? if so, I've seen some pretty cool results from this upgrade (though on a subaru, not a miata). Basically you give up only a couple hundred rpm worth of spool, but pick up a healthy chunk of torque and quite a bit topend power. something like 30-50 torque if I'm not mistaken. if you do it right and have it balanced, and have the engine to support it (you'll wanna really crank up the boost to see good power increase)
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Old 10-16-2013, 03:42 PM   #3
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Yes the 3 bolt one. Fitting a 19 in place of the 13 compressor wheel is quite a jump would you not end up with a bit of a mismatched turbo. If the turbo is compressing more than its able to flow through the turbine would that not result in something unwanted?

Last edited by delcbr; 10-16-2013 at 04:42 PM. Reason: Damn predictive text
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Old 10-16-2013, 03:48 PM   #4
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Quote:
Originally Posted by delcbr View Post
Yes the 3 bolt one. I thought fitting a large compressor and keeping the turbine standard would be is matched it must hurt it more than losing a few hundred rpm spool.
huh?
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Old 10-16-2013, 04:43 PM   #5
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Edited my last post.
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Old 10-16-2013, 05:08 PM   #6
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Mis-matched as in how? Laggier? Sure you'll probably give up a couple hundred rpm worth, but should pick up a healthy chunk of torque.

I guess it comes down to what your reasoning and goals are with this upgrade
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Old 10-16-2013, 05:21 PM   #7
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What I am compressing into the engine has got to come out through the turbine and into the exhaust. So if I am putting in far more air than before surely the turbine won't be able to cope. Will it over spin, will it create excessive boost pressure and heat if the turbine can't flow the increase in air would porting the waste gate help? You see where I am coming from now?
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Old 10-16-2013, 05:21 PM   #8
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I had a TD04HL-15g that I threw a 19T wheel and housing on. Didn't affect spool too much and didnt take too long to hit 22 psi. Probably one of my favorite turbos that I ran. Although my 15g had a slightly larger exhaust wheel then your 13t so results may vary.
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Old 10-16-2013, 05:25 PM   #9
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Quote:
Originally Posted by delcbr View Post
What I am compressing into the engine has got to come out through the turbine and into the exhaust. So if I am putting in far more air than before surely the turbine won't be able to cope. Will it over spin, will it create excessive boost pressure and heat if the turbine can't flow the increase in air would porting the waste gate help? You see where I am coming from now?
you're WAYYYY overthinking this lol

you're talking about a baby 19t compressor here, not some mammoth 76r or something.

I doubt you'll choke that turbo up with a 1.8L, but even if you somehow do, all that will happen is a bit of boost taper near redline.
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Old 10-16-2013, 05:28 PM   #10
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Ok thanks your probably right
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Old 10-17-2013, 10:06 AM   #11
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Wastegate understanding fael?
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Old 10-17-2013, 01:37 PM   #12
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the 19t change is common in the suby world. I came from that world and have buddies that have tried it out. it works. like 18psi said, youre way over thinking it.
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Old 10-17-2013, 02:07 PM   #13
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I fitted a larger 60mm compressor to my T2554 turbo making it a T2560

It basically shifted the peak torque and power further up the rev range. Peak power therefore increases as the torque is shifted.

I read somewhere you usually try to keep the diameters of comp and turbine within 25% of each other but this isn't a hard and fast rule as the pitch has a bearing too.

It WILL increase lag a far bit.

On mine a 6mm increase in comp diameter shifted peak torque by about 500rpm

The larger comp will increase load on the turbine so it may even spin slower, its best to improve exhaust breathing to help with turbine gas flow..
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Old 10-17-2013, 02:13 PM   #14
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Fun fact: 08 wrx's actually come with this compressor wheel (or something very similar) stock on their td04

IF its good enough for subaru, then.......
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Old 10-18-2013, 11:53 AM   #15
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Quote:
Originally Posted by 18psi View Post
Fun fact: 08 wrx's actually come with this compressor wheel (or something very similar) stock on their td04

IF its good enough for subaru, then.......
Yup, 02-07 WRX are td04L-13t, 08 is td04L-19t. The L is the turbine wheel size, the td04 bit is the center housing, and the 19t bit is the compressor wheel. There are also H and HL and STS turbine wheels, STS is the only after market wheel and its lighter and has less inertia than the other wheels while flowing more than the HL (the biggest stock wheel size) and supposedly spooling better than the HL. There is only a 6cm turbine housing for the td04 in the subie fitment.

In order to put the 19t wheel into a turbo that originally came with a 13t wheel you will have to machine the center housing to clear the 19t exducer. This is why I just bought a 08wrx turbo that had a VERY BAD DAY (looks like the compressor nut spun off while the engine was running) for 40 bucks. I'm going to be buying a 19t standard subaru compressor cover and billet 19t comp wheel, STS turbine and shaft and a rebuild kit and slapping that bad boy together. I'm thinking it should reach 300hp in this setup and I'll have pretty much the only td04 with an STS turbine wheel in existence because they literally came out like 2 weeks ago in this size, no subaru people know how to work on cars, and no one is going to pay $900 to buy one completely together because they could just get a 16g instead.
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Old 10-18-2013, 02:26 PM   #16
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Quote:
Originally Posted by Leafy View Post
no subaru people know how to work on cars
I mean, 18psi seems to know his way around a car or two..

He did have an auto Corvette though so...


Also, why not just VF48 instead of ths swanky td04-19t you're building? I don't know how much money you'll have into a billet comp wheel, STS turbine, and rebuild kit, etc. but it sounds like for about the same money you could have a VF48 that will easily make 300whp and be a whole lot less work. What's all this extra work going to get you? 300rpm better spool?
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Old 10-18-2013, 02:35 PM   #17
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Quote:
Originally Posted by Efini~FC3S View Post
I mean, 18psi seems to know his way around a car or two..

He did have an auto Corvette though so...


Also, why not just VF48 instead of ths swanky td04-19t you're building? I don't know how much money you'll have into a billet comp wheel, STS turbine, and rebuild kit, etc. but it sounds like for about the same money you could have a VF48 that will easily make 300whp and be a whole lot less work. What's all this extra work going to get you? 300rpm better spool?
Should spool a little better than the vf, and now I'll have more or less a new turbo for a little bit more money than buying some unknown mileage vf. I also kind of just want to rebuild a turbo for the sake of rebuilding a turbo.
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Old 10-18-2013, 02:44 PM   #18
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LOL oh yeah, us subaru people don't know a thing about cars
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Old 10-18-2013, 02:59 PM   #19
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Quote:
Originally Posted by 18psi View Post
LOL oh yeah, us subaru people don't know a thing about cars
Hey, what soap should I use to clean my wrx?

Ask your tuner.
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Old 10-18-2013, 03:02 PM   #20
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Ok fair enough, but at least that usually leads to a bit less hacked cars.

*edit: back on topic. here is a buddy of mine's 2005 wrx with the 19t wheel td04 and some other goodies

car moved out with the quickness

and another
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