GT2560 - 261 ft-lbs, 272 hp
09-19-2011, 01:15 AM
#21
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That's pretty late for full retard. In my experiments, staying advanced that long hurt my spool a lot. In fact, by staying fully advanced longer I could delay hitting my boost target by 1500RPM IIRC. Whee I guess
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09-19-2011, 03:10 AM
#22
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I wonder if the Blox manifold on my car helps to smooth out the spool-up spike that you see, Jason. Look at the Excel chart - the torque uptake is much smoother with the Blox manifold than it is with the stock manifold.
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09-19-2011, 03:38 AM
#23
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Jason, after looking at your boost vs. RPM plot again, you've got something going on that is hurting spool. 10psi at 3500rpm is really, really slow.
https://www.miataturbo.net/diy-turbo-discussion-14/i-want-your-spool-data-26641/
Put your boost curve into that thread - you are spooling up really, really slowly.
https://www.miataturbo.net/diy-turbo-discussion-14/i-want-your-spool-data-26641/
Put your boost curve into that thread - you are spooling up really, really slowly.
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09-19-2011, 10:20 AM
#24
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It's not hard to do a full retard run
a full advance run
and a few runs in between.
I guarantee more advance below 4000 will improve that spool situation.
Perhaps I *do* need to dyno my car on october 15 to do some VVT data pulls...
a full advance run
and a few runs in between.
I guarantee more advance below 4000 will improve that spool situation.
Perhaps I *do* need to dyno my car on october 15 to do some VVT data pulls...
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09-19-2011, 11:44 AM
#25
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Hmm the post I typed last night didn't show up.
After thinking long and hard, I suddenly remembered the giant O ring in the compressor housing (sealing against the CHRA), has been broken for years. It's in there, it just doesn't complete an entire circle. The replacement has been sitting around for years. So, I have a small boost leak. This maycontribute to the slow spoolup, along with the wrong VVT setting ~ 3200 RPM. I'm glad that Ian's data is there to compare against. Without it I'd have been blissfully unaware of a spoolup problem.
Tomorrow I go in for (left) knee surgery (ACL recon), so it'll be a few weeks before I can drive a stick.
After thinking long and hard, I suddenly remembered the giant O ring in the compressor housing (sealing against the CHRA), has been broken for years. It's in there, it just doesn't complete an entire circle. The replacement has been sitting around for years. So, I have a small boost leak. This maycontribute to the slow spoolup, along with the wrong VVT setting ~ 3200 RPM. I'm glad that Ian's data is there to compare against. Without it I'd have been blissfully unaware of a spoolup problem.
Tomorrow I go in for (left) knee surgery (ACL recon), so it'll be a few weeks before I can drive a stick.
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09-19-2011, 12:43 PM
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09-19-2011, 12:54 PM
#29
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Here's a great way to analyze a dyno plot.
BMEP (in psi) and BMEP per MAP in psi per atmosphere of MAP
BMEP (in psi) = tq (ft-lbs) / displacement (L) * 2.47
BMEP per MAP = BMEP / MAP (in atmosheres)
BMEP per MAP = BMEP / MAP *101 (if MAP is in kPa)
The magic number is 180 psi at torque peak.
This translates to 73 ft-lbs per L per atmo of MAP.
Here's the importance of BMEP
http://www.epi-eng.com/piston_engine..._yardstick.htm
The resulting BMEP/MAP is an indication of VE and correct ignition timing.
In my curve above, the plot from 4000-7000 is VE
The reduced VE below 4000 RPM is due to the the wastegate being closed, TIP is higher to accelerate the turbo shaft.
Last edited by JasonC SBB; 09-19-2011 at 05:50 PM.
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09-19-2011, 01:04 PM
#31
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Jason, after looking at your boost vs. RPM plot again, you've got something going on that is hurting spool. 10psi at 3500rpm is really, really slow.
https://www.miataturbo.net/showthread.php?t=26641
Put your boost curve into that thread - you are spooling up really, really slowly.
https://www.miataturbo.net/showthread.php?t=26641
Put your boost curve into that thread - you are spooling up really, really slowly.
https://www.miataturbo.net/showpost....3&postcount=12
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12-11-2011, 02:22 PM
#32
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Haven't I told you that this isn't correct before, Jason?
Purple line is my first built motor (84mm 8.6:1, BP4W head, GT2871R). Blue line is my second built motor (83.5mm 8.6:1, VVT head, GT2871R) with VVT at full retard.
Now look at the old motor vs. the new motor w/ VVT advanced under 4500rpm (huge low-end gains) and the Blox manifold installed (huge top end gains). VVT is at full retard from ~5000rpm up, just the same as it was in the blue/purple chart - if VVT were causing the top-end gains, they would have appeared in the blue/purple chart - but they didn't. The lighter lines under it are the lines from the previous visit, which was VVT and the Blox manifold at 14psi on 100 octane.
All four torque curves synthesized into one:
See how the torque curve extends flat to 6000rpm on both of the Blox curves, but the torque drops at 5000 on the stock manifolds? Now look at your torque curve - the torque drops at 5k.
VVT does not have any effect on high-end torque - the intake manifold makes that difference, and I've never seen any data to disprove that.
Purple line is my first built motor (84mm 8.6:1, BP4W head, GT2871R). Blue line is my second built motor (83.5mm 8.6:1, VVT head, GT2871R) with VVT at full retard.
Now look at the old motor vs. the new motor w/ VVT advanced under 4500rpm (huge low-end gains) and the Blox manifold installed (huge top end gains). VVT is at full retard from ~5000rpm up, just the same as it was in the blue/purple chart - if VVT were causing the top-end gains, they would have appeared in the blue/purple chart - but they didn't. The lighter lines under it are the lines from the previous visit, which was VVT and the Blox manifold at 14psi on 100 octane.
All four torque curves synthesized into one:
See how the torque curve extends flat to 6000rpm on both of the Blox curves, but the torque drops at 5000 on the stock manifolds? Now look at your torque curve - the torque drops at 5k.
VVT does not have any effect on high-end torque - the intake manifold makes that difference, and I've never seen any data to disprove that.
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