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jgkurz

Turbine size matters

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2 hours ago, rossman said:

Your issue sounds similar what big-phil experienced back in 2009 except you aren't hearing the turbo flutter as he was. The solution, as recommended by Tony D was to go with a .82 turbine.

 

 

 

 

Thanks for the the link from 2009. It certainly seems to apply here.  I even commented haha.  I think I'm going to swap in a .82 exhaust turbine after I check for the obvious issues. I was worried about spool so I went with the .63. My guess is that the new (larger) compressor is choked earlier than I expected. Looking at the dyno graphs, the engine goes worse as early as 3K RPM. My hope is that the .82 get's me back to my older dyno results plus a bit better. 

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1 minute ago, Bernardd said:

Call Jeffp about a .82 turbine housing.  He might have one for you.  Have you verified that your blowoff and wg are not opening?  While I didn't do testing on the dyno with my old setup I went through a similar issue with a stage 3 .63 vs a .82 exhaust housing.  The .82 took about 300 more rpm to achieve max boost but the power difference was very noticeable.  I can't remember my trap speeds but it was obvious that the spool vs power wasn't significant enough to keep the smaller housing installed.  The smaller housing also made the engine more sensitive to detonation.  That was my experience.  

 

Hi Bernardd, I have been stubborn about keeping the .63 due to spool but I think it's time to make the change. The dyno shop I work with wants to tap my exhaust manifold to check back pressure, which would prove all this scientifically, but that adds even more cost and time. My turbine is a Tial v-band setup. Is that what JeffP uses?

 

I have not checked my BOV and WG because they seemed to be working as they should. My Tial 44mm wastegate has springs that put me at 13psi with the boost controller off. It is controlling boost well until 22psi. I am bleeding boost after the "stonewall" occurrs. Boost is super stable until then.

 

How would I check my BOV? Just increase BOV spring pressure and run it up to max boost again?

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16 hours ago, Gollum said:

Worth reading for the technical gems that are easy to pick up, even if it's not your engine platform:

 

https://www.perrin.com/blog/post/garrett-gtx-turbo-comparo-part-2

 

A great piece of it:

 

 

 

 

I read through the Perrin link again and it is interesting for sure. Notice the Dynapack dyno is showing flywheel HP and TQ which is different. I initially saw his GTX3582R with the .63 turbine housing reach 497hp so I figured I'd be able to make 455hp again with my old L28. WRONG! His 487 is flywheel. My 455 is rwhp so not the same. 487 crank hp will be in the neighborhood of 414rwhp if 15% drivetrain loss is used. 

 

The weird thing about my issue is that the new GTX3576R is worse all around, not just top end. If it was just worse at top end I'd be super confident that the .63 was the issue. I am going to try a .82 but I also may have boost leak issue that needs to be resolved although I have no idea where.

 

On a postive note. if the .63 housing is indeed choking the HP as low 3000rpm there may be significant gains possible across the whole RPM range with the larger .82 housing. I call it pent up demand. Just a theory at this point. 

 

 

 

 

tech_turbo_gtxgtx3563v8219bar.jpg

Edited by jgkurz

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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.

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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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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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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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