Curt’s Gr8t 8 Turbo Build
#601
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For sake of discussion see the below M/E log & v-dyno pairs.
The first first log & v-dyno pair was tight, no leak, and at ~ 12 psi. 370 HP/ 251 lbft
There was likely a small leak on the second log & v-dyno pair, ...but for sake of discussion can we presume the system was sealed tight during this pull. Peak boost was 13.x psi. 314 HP/ 265 lbft
What can you discern regarding the engine nearing flow capacity from these?
.
The first first log & v-dyno pair was tight, no leak, and at ~ 12 psi. 370 HP/ 251 lbft
There was likely a small leak on the second log & v-dyno pair, ...but for sake of discussion can we presume the system was sealed tight during this pull. Peak boost was 13.x psi. 314 HP/ 265 lbft
What can you discern regarding the engine nearing flow capacity from these?
.
Last edited by jcbrx8; 01-09-2020 at 11:21 AM.
#602
Boosted Kiwi
iTrader: (2)
Firstly .... much better to increase the size of the chart so you can see it better (I use the 2.5 times button)
I think you can forget the second chart because of the leak .... the amount that it exceeds the first chart suggests it's more than a small one.
The first chart is showing a leveling out at 7555 and , although it's not reached the point where maf reduces thereafter . I'd still recommend dumping boost there because from there on the amount of exhaust gas carryover is increasing. On a dyno you would probably see power peak a few hundred rpm after that point but for the sake of safety I'd still dump at that point.
I think you can forget the second chart because of the leak .... the amount that it exceeds the first chart suggests it's more than a small one.
The first chart is showing a leveling out at 7555 and , although it's not reached the point where maf reduces thereafter . I'd still recommend dumping boost there because from there on the amount of exhaust gas carryover is increasing. On a dyno you would probably see power peak a few hundred rpm after that point but for the sake of safety I'd still dump at that point.
#603
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...The first chart is showing a leveling out at 7555 and , although it's not reached the point where maf reduces thereafter . I'd still recommend dumping boost there because from there on the amount of exhaust gas carryover is increasing. On a dyno you would probably see power peak a few hundred rpm after that point but for the sake of safety I'd still dump at that point.
#604
Boosted Kiwi
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Yes ....... what I've noticed is (provided the turbo will flow enough) ...the more inefficient the system is ........... the higher in the rpm range you actually reach that point . Your system looks pretty good IMO as it's seeing that point quite early which means you can raise boost and make more torque throughout the range.
#606
Boosted Kiwi
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Yeah .... I didn't explain that too well
Really I just meant that , so long as you cut boost at the right point as discussed, you can keep raising the boost and make a really good power curve. If you don't cut boost or limit the revs ...eventually the engine will blow at high rpm.
With an inefficient system you can actually rev it a little higher at the same boost but will make less power and be stressing the engine and all the cooling systems more in doing so.
Really I just meant that , so long as you cut boost at the right point as discussed, you can keep raising the boost and make a really good power curve. If you don't cut boost or limit the revs ...eventually the engine will blow at high rpm.
With an inefficient system you can actually rev it a little higher at the same boost but will make less power and be stressing the engine and all the cooling systems more in doing so.
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jcbrx8 (08-14-2020)
#608
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Yeah .... I didn't explain that too well
Really I just meant that , so long as you cut boost at the right point as discussed, you can keep raising the boost and make a really good power curve. If you don't cut boost or limit the revs ...eventually the engine will blow at high rpm.
With an inefficient system you can actually rev it a little higher at the same boost but will make less power and be stressing the engine and all the cooling systems more in doing so.
Really I just meant that , so long as you cut boost at the right point as discussed, you can keep raising the boost and make a really good power curve. If you don't cut boost or limit the revs ...eventually the engine will blow at high rpm.
With an inefficient system you can actually rev it a little higher at the same boost but will make less power and be stressing the engine and all the cooling systems more in doing so.
We've discussed some strategies to cut boost. I need to get that done.
Another To Do list is materializing re: electronics:
- Re-plumb EBC control line pre-throttle
- Wire AEM Failsafe boost cut
- Wire boost cut @ 7500 rpm
Meanwhile , I'll limit revs...
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Brettus (01-09-2020)
#609
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Went back and reviewed the "Where Did You Plumb Your BC Signal Line To" thread and can see where pre or post TB can work.
If plumbed pre-TB, the BC alone controls the intake pressure...regardless the TB position.
If plumbed post-TB, a good BOV...set properly...w/recirc is required to do the same job.
While both can work, and I had no issues w/mine plumbed post-TB; I concur simplicity dictates pre-TB s/b superior.
Had to settle this in my own mind...
If plumbed pre-TB, the BC alone controls the intake pressure...regardless the TB position.
If plumbed post-TB, a good BOV...set properly...w/recirc is required to do the same job.
- When the TB is open, intake pressure is governed by the BC alone...similar to the pre-TB config.
- But when the TB is partially or fully closed, the BC sees a differential up to full vac..., the turbo continues to spool and build pressure in the intake..., and this excess pressure, I.e. above target boost, m/b released by the BOV. The BOV m/b recirc'd to avoid jacking w/AFRs. If the BOV or its control lines fail, intake pressure spikes will occur.
While both can work, and I had no issues w/mine plumbed post-TB; I concur simplicity dictates pre-TB s/b superior.
Had to settle this in my own mind...
Last edited by jcbrx8; 01-10-2020 at 06:47 AM.
#610
Boosted Kiwi
iTrader: (2)
I actually spent a **** ton of time playing with this to reach the conclusion I did. Mainly because all the conventional wisdom suggested I do it the other way around. It was about then I started to realise that conventional wisdom isn't always best
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Brettus (01-11-2020),
strokercharged95gt (01-11-2020)
#618
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- =< 7500: 13#
- > 7500: 9#
Last edited by jcbrx8; 01-14-2020 at 09:38 AM.
#621
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Still exhibiting a boost leak on pulls of target boost above 13psi ..., but she managed the below pull tonight: @ 13.6 psi peak...trailing to 12.3 psi, and 380 g/s max @ 7966 rpm.
Pleased..., but still working to eliminate the leak to ease turbo load, and better sustain HP/torque thru the rev range. So, I purchased a new hump coupler for the charge to TB connection. I'll get that installed over the next few days and see if it results in reliably sealing above 13 psi.
Pleased..., but still working to eliminate the leak to ease turbo load, and better sustain HP/torque thru the rev range. So, I purchased a new hump coupler for the charge to TB connection. I'll get that installed over the next few days and see if it results in reliably sealing above 13 psi.
Last edited by jcbrx8; 01-22-2020 at 10:10 AM.
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Rkesh88 (01-14-2020)
#623
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Jesse - My pleasure. Just trying to contribute back to the community... from which I've learned so much...challenges , and achievements
Last edited by jcbrx8; 01-14-2020 at 10:46 PM.
#624
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A spirited drive today indicates she's holding 13.5 psi. I believe that the combination of heat cycling of the coupler and putting a 1/4-1/2 turn on key clamps after each drive... while hot... has resulted in better sealing. Now, I don't want to touch a thing.
On the below pull today boost rise peaked at 13.46, and increased to 13.59 psi thru the rev range. Pretty stoked at this result.
On the below pull today boost rise peaked at 13.46, and increased to 13.59 psi thru the rev range. Pretty stoked at this result.
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Brettus (01-19-2020)