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jgkurz

Turbine size matters

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8 minutes ago, 240Z Turbo said:

doubtful your surging on this turbo and not hearing or feeling it.  The surge ports don't work well on that turbo and it would be audible as well as show up in the dyno graph.  Having run the GTX3076r, GTX3576r, and GTX3582r(current) on my 2L EVO it definitely seems something is off with your setup.  You would need to stick a speed sensor on the turbo to understand where you are on the map and it would also answer any doubt about surge.  On the GTX3576r I made 505hp@wheels 33psi tapering to 31psi on 93 pump and 1.01ar Vband TS, 460hp@wheels 30psi on 93 pump and 1.06ar T4 TS, and 573hp@wheels 37psi tapering to 33psi on 110L and 1.01ar Vband TS.  Since I log turbo speed the turbo was riding the choke line on the 573hp@wheel dyno pass so I gave it everything it had. 

 

The GTX3576r has the same turbine wheel as the old school 35r, but new billet compressor wheel so it actually flows more than the old 35r.  This turbo flows ~64lbs/min so not gonna support 600hp@wheels on a accurate dyno unless your drivetrain loss is ~40hp.  The fact that your pushing it past 22psi and not seeing a difference suggests you have a restriction in your system.  Also, the .63a/r is small for a 2.8L so likely part of the problem and in general I don't like running open scroll because you sacrifice too much spool and gain little on the topend, but I do understand it is not an easy option to run a TS on the L28 due to lack of available manifolds.  I saw ~400rpm loss in spool when going from 0.63 to 0.82 on the EVO, but gained ~35hp on the topend when I used to run an open scroll setup with the GTX3076r. 

 

Also, on my initial TS setup I lost no spool and gained ~50whp when swapping from the GTX3076r to the GTX3576r so turbine size does matter.

 

Excellent info James. Thank you. That EVO has to be a handful at those power levels. It's amazing the drivetrain doesn't fly out of the car. You probably don't remember, but my car was built with much of your advice. You guided me through several build questions on email and over the phone. It's been a LONG time. I think you had your yellow 240 back then. The only thing I regret on my engine is my choice to run low compression. Oh well. I can just run more boost. 

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Great info 240Z Turbo!

 

One thing I'd point out though, is that I generally prefer to look at NA power levels to gauge where an engine lands in it's recommended displacement window. Though the gtx3576r is suggested by garret to fit 2.0 to 4.5 liters, you need to figure out where your engine lands in that window to better solve which turbine AR to run. Like how the evo is a GREAT engine design, and wouldn't struggle to flow 200hp worth of air NA. By contrast, a 200hp NA L series is a pretty hot street setup, requiring basic head cleanup, a good intake, exhaust, and cam combo. Some nissan L heads can flow a LOT more with good port work, but that's not the majority of us here. So though 2.8 liters, it likely ends somewhere in the low to mid range of "NA Breath" for this turbo. But I agree, that .63ar is likely a touch small for the engine. I think we all agree this should be making closer to the same power as the other turbo though, so something seems off.

 

But once whatever is "off" is fixed, it's likely this compressor is going to land close to the last turbo before being turbine energy limited.

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2 hours ago, jgkurz said:

 

Excellent info James. Thank you. That EVO has to be a handful at those power levels. It's amazing the drivetrain doesn't fly out of the car. You probably don't remember, but my car was built with much of your advice. You guided me through several build questions on email and over the phone. It's been a LONG time. I think you had your yellow 240 back then. The only thing I regret on my engine is my choice to run low compression. Oh well. I can just run more boost. 

 

Just so you know I have my GTX3576r on the shelf and plan on running it when I start building the 71 240Z I purchased last year.  Just saying that I don't perceive any issues with that turbo making power on an L-series motor.

 

500hp@wheels feels quick and 573@wheels pulls really strong, but no issue to control as the car is AWD.  I have to say it is fun jamming the gears at that power level and revving the engine to 9K.  When you do the 2-3 shift the car still pulls like a freight train in 3rd gear with no signs of slowing.  Haven't run the GTX3582r past 34psi on pump 93 yet so I don't know how much more power it will make.  My GTR put down ~705hp@wheels on 93 pump and ran 10.2@138 on the same pump gas tune, but running race gas.  The GTR doesn't feel like its got 700hp@wheels because its a big/heavy car so it is deceptively smooth at that power level.

 

Higher compression is nice and my EVO is 10:1 and most built GTR engines are in the 9:1 to 10:1 range even running pump 93.  However, the fact that you run low compression is not necessarily bad and just look at TimZ and his 7.5:1 monster making in the 700hp@wheels range on E85.  I think that was his old compression and suspect he still runs low compression, but he might chime in and correct me on that.

 

If you want to understand the turbine restriction you can put a port on your exhaust manifold to measure Exhaust Gas Back Pressure before the turbo.  Off the top of my head you want to be in the 1.5x boost range and if you measure post turbo on the downpipe you ideally want to be in the 1psi range, but slightly higher is likely also fine.  Maybe you can post a log shot of your AFR, boost, and timing curves as a function of RPM.

 

Also, the dyno results you posted, are they a direct before/after of old turbo vs new turbo with no other changes or did you make changes?

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Looking through the spec sheet.

 

This is a 3L motor using the stock L28ET manifold. 

 

T3 flange at 0.63 on a 3L seems really quite restrictive. 

 

Another thing that would make sense to me is if you are loosing compression in a cylinder that would definitely drop you down quite a bit of power. 450 to 380 is almost 1/6, and boosting at that levels might not be surprising. 

 

A compression test or at least pulling the plugs might reveal some basic insight as to the motor health.

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40 minutes ago, seattlejester said:

Looking through the spec sheet.

 

This is a 3L motor using the stock L28ET manifold. 

 

T3 flange at 0.63 on a 3L seems really quite restrictive. 

 

Another thing that would make sense to me is if you are loosing compression in a cylinder that would definitely drop you down quite a bit of power. 450 to 380 is almost 1/6, and boosting at that levels might not be surprising. 

 

A compression test or at least pulling the plugs might reveal some basic insight as to the motor health.

 

 

I did a full leak-down and compression test recently just prior to the turbo upgrade. All cylinders checked out. I do need to check the plugs as well. I have ordered my new .82 housing and will report back as soon as it is installed and re-dyno'd.

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5 hours ago, 240Z Turbo said:

 

Just so you know I have my GTX3576r on the shelf and plan on running it when I start building the 71 240Z I purchased last year.  Just saying that I don't perceive any issues with that turbo making power on an L-series motor.

 

500hp@wheels feels quick and 573@wheels pulls really strong, but no issue to control as the car is AWD.  I have to say it is fun jamming the gears at that power level and revving the engine to 9K.  When you do the 2-3 shift the car still pulls like a freight train in 3rd gear with no signs of slowing.  Haven't run the GTX3582r past 34psi on pump 93 yet so I don't know how much more power it will make.  My GTR put down ~705hp@wheels on 93 pump and ran 10.2@138 on the same pump gas tune, but running race gas.  The GTR doesn't feel like its got 700hp@wheels because its a big/heavy car so it is deceptively smooth at that power level.

 

Higher compression is nice and my EVO is 10:1 and most built GTR engines are in the 9:1 to 10:1 range even running pump 93.  However, the fact that you run low compression is not necessarily bad and just look at TimZ and his 7.5:1 monster making in the 700hp@wheels range on E85.  I think that was his old compression and suspect he still runs low compression, but he might chime in and correct me on that.

 

If you want to understand the turbine restriction you can put a port on your exhaust manifold to measure Exhaust Gas Back Pressure before the turbo.  Off the top of my head you want to be in the 1.5x boost range and if you measure post turbo on the downpipe you ideally want to be in the 1psi range, but slightly higher is likely also fine.  Maybe you can post a log shot of your AFR, boost, and timing curves as a function of RPM.

 

Also, the dyno results you posted, are they a direct before/after of old turbo vs new turbo with no other changes or did you make changes?

 

Thanks for the comments and re-assurance. The dyno chart is before and after (old turbo vs new turbo). Different dyno's but the same DynoJet model. The fact that the lines match up so perfectly at the starts leads me to believe the data is good. No other changes to the air flow of the engine other than a large 4" inlet to the turbo and a equally large K&N filter. The downpipe is new and all mandrel 3" like before. Here's a pic of the flange we made for the v-band and the new DP. 

 

I'll work on the AFR, boost, and timing graphs. 

 

P.S. How do you shove 34psi in a 10:1 engine on 93 octane?  I know the EVO engines are state-of-the- art but the compression at 34psi would be about 18:1. Just curious how that is even accomplished. I have a friend who gets similar power out of Toyota MR2 engines. Simply astounding your engines stay together.  

 

P.S.S. I am pleased you are working on another Z project. I can't wait to see how it comes together. 

 

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Edited by jgkurz

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Your adapter for the wastegate looks great and you did a very nice job on the downpipe.  Since your graph lines up almost exactly until you hit a certain RPM it would seem to indicate a restriction or a boost leak.  What doesn't make sense is that you car won't make additional boost and we know the pressure is created because of the resistance to flow (restriction).  A turbo speed sensor would definitely give you a better sense of these issues as well as the ability to measure EGBP before/after the turbo.  I see you run the Tech 3, do you have any spare analogue inputs?

 

Coming from my turbocharged 240Z that was running in the low 20's psi range it was a surprise that I was able to run so much boost on the EVO.  33-34psi is very common for the EVO on pump 93 and I have been running it this way for 4-5 years on the same engine.  Keep in mind that I run -1deg of timing at peak torque and ramp it up to +8deg at redline so significantly lower timing than the L-series and my GTR.

 

If you need a larger Tial housing just PM me and I will help you.

Edited by 240Z Turbo

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I believe I said this on another thread but your adapter is a very clever design. 

 

I have a very similar setup as you including a .62 turbine T3 housing but with a first generation GT35R.  I'm thinking I probably have the same issue as you but haven't driven it enough to know.  If anybody has a Garrett GT3576R .82 T3/v-band turbine housing, let me know and I will take it off your hands :).

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Compression ratios are rarely comparable from engine to engine when considering maximum boost for a given fuel.

 

I'd be interested what the IAT numbers were at the manifold though. I bet they weren't ever over 160... At the end of the day, detonation isn't encouraged by compression ratio, but the heat caused by compression. Without in chamber data of heat and various hot spots (which non of us have access to) you'll never predict maximum boost/compression combos. So we're left tuning and guessing based upon our own data combined with others experience.

 

Also, never underestimate what great quench pad design can do. I know in a lot of high performance drag application it's not uncommon to remove quench pads from the cylinder head, but you're talking about 80+psi engines pushing over 300hp/liter... 

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Posted (edited)

Hi all, Just a quick update. I finally got some time to work on this project and made an interesting discovery. I tapped my new adapter between the turbine and the exhaust manifold so I could test back pressure. I used the sensors from the DynoJet to log pre-turbine pressure and intake pressure. The pre-turbine sensor read a full 10psi higher than the intake. I have confirmed that back pressure due to my .63 a/r turbine is the issue.

 

What I find interesting is that this new setup uses the same .63 a/r turbine size as the old t3/4 but makes a lot less power.  It makes me wonder whether they really are the same even though on paper they are supposed to be. Maybe the combined T350 turbine wheel / .63 modified turbine housing on my old turbo flows more than the GTX3576R with the .63. Its really the only explanation I can think of.

 

 The question now is whether I should go to a .82 or 1.03.  I’m sure a 1.03 would be great for peak power but would be miserable to drive on the street.  I am leaning heavily towards a .82.

Edited by jgkurz

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2 hours ago, rossman said:

Thanks jgkurz! As another data point, I seem to remember that bigphil had a similar issue when he was running an l6. What was the fix? .82 turbine.

 

Not fixed yet. Ordered a .83 housing, but still while off from completing the install. I'll be sure to post results when I get the car back on the dyno.

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Posted (edited)
25 minutes ago, jgkurz said:

 

post results when I get the car back on the dyno.

I certainly would appreciate it!  Do you know if going from .63 to .82 moves the exhaust v-band relative to the T3 flange?  I assume it does.  If so I may have to modify my down/wastegate pipe when I eventually get there.

Edited by rossman

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36 minutes ago, rossman said:

I certainly would appreciate it!  Do you know if going from .63 to .82 moves the exhaust v-band relative to the T3 flange?  I assume it does.  If so I may have to modify my down/wastegate pipe when I eventually get there.

 

Yes, the downpipe needed to be completely re-fabricated. Like you, I hoped it would be a simple flange change but it was not in my case.

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Posted (edited)

Hi all, I finally got time to install the new .82 housing and dyno test. To close out this thread I wanted to post my results. The new Garrett GTX3576R finally was able to produce 467hp and 496ftlb on a DynoJet chassis dyno. The .63 housing maxed out at 404hp and just under 400ftlb. Boost was 23lbs. The boost lag worsened a fair amount with the larger housing. The boost did come up far smoother which was a positive effect. Also, the old turbo with the small turbine housing use to come up on boost quick which was fun, but it would also reek havoc on clutches. 

 

Here's the interesting thing about my upgrade. The old T3/4 hybrid made 451hp and 467ftlb at 27psi WITH a .63 turbine housing and quick spool. My new EXPENSIVE turbo did make more power at a lower boost, but was it worth it over a traditional T3/4 journal bearing? Not really. I started with a .63 housing on new GTX3576R, but it caused 10psi of back pressure and only made 402hp. The old turbo made 451hp with a .63 turbine. The 16hp gain with the GTX3576R wasn't worth the trouble given the boost lag. My cylinder head and intake are near stock which is certainly limiting my engine. Notice the peak power is at 5400rpm. All-in-all, 550hp at the crank is pretty good for an old L28.

 

 

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Edited by jgkurz

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Not worth it? You're hard to please!! Notwithstanding the mystery issues on the GTX .63 hotside, you now have virtually the same boost threshold as your old turbo with a huge, almost 40 lb*ft gain, all while running 4 psi less boost!

 

To compare apples to apples as much as you can, you really should run 27psi on your new setup and see what happens. I bet the difference will be huge.

 

BTW, journal vs. ball bearing differences are not that huge in terms of absolute power. Transient response should be better though, especially coupled with the more modern wheel design.

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Posted (edited)
43 minutes ago, bradyzq said:

Not worth it? You're hard to please!! Notwithstanding the mystery issues on the GTX .63 hotside, you now have virtually the same boost threshold as your old turbo with a huge, almost 40 lb*ft gain, all while running 4 psi less boost!

 

>>Yeah, more power on less boost is always good but the cost to do this project was crazy expensive. Having a part custom CNC'd on top of an expensive BB turbo added up to big $.  The $/hp just didn't work out well. To some degree that is the nature of any car project. I like the car and it is fast so it's all good. 

 

>>I think the GTX hotside issue can be attributed to the Tial housing. Their .63 visually looked smaller than my T3/4 .63 housing. I should have taken that cue. 

 

 

Quote

 

To compare apples to apples as much as you can, you really should run 27psi on your new setup and see what happens. I bet the difference will be huge.

 

>> I may test 27psi some day, but I will need to beef up my valve springs. My Crane springs are 90# at the seat so only 63# if I run 27psi. I think my peak RPM of 5400rpm may be caused by weak valve springs. That and a near stock head and N42 intake.

 

Quote

 

BTW, journal vs. ball bearing differences are not that huge in terms of absolute power. Transient response should be better though, especially coupled with the more modern wheel design.

 

 

>>I have learned this as well. A journal turbo from a quality manufacturer is still a great option.  Thanks for all your comments!

Edited by jgkurz

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One of the interesting things the Audi BT guys are doing is putting a 4" expansion section on the downpipe. This really results in a drop in Exhaust back pressure.   Quicker spool and higher WHP. They are transverse mount, so limited by space.  But even a shortish ( 12" ) expansion pipe made a noticeable difference.

 

I suspect a 4" downpipe on an L-6 then taper to 3" or 3.5" exhaust would certainly help. 

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