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Old 11-12-2011, 11:21 PM   #426
Phatron
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Originally Posted by reid-o View Post
If you have a way when you do the final tune, can you check back pressure?
Just like to see more than just dyno results. I understand if this is not possible
do u have other egbp data to compare to? i think i've only seen that data posted up once by someone.
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Old 11-12-2011, 11:40 PM   #427
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Quote:
Originally Posted by Phatron

do u have other egbp data to compare to? i think i've only seen that data posted up once by someone.
The idea is just to compare the ratio to the intake pressure. Yes I heave ratios from my evo.
The value is meaningless
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Old 11-12-2011, 11:42 PM   #428
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It became useful at high pressures to determine whether the compressor was capped or the turbine was capped. I'm curious how the small runner twinscroll does at high pressures. I'm wondering if the smaller runners are contributing to the fast spoo. We will see as the pressure goes up.
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Old 11-13-2011, 12:01 AM   #429
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how is the data used? can you just post some of your numbers and ratios? and conclusions drawn? you can pm if you want, unless others are interested....

For this turbo, once it stops adding airflow.....you dont really have a choice to change wheels or housings....so there is only one option, move up to the 8374. Or is it possible to make a Franken EFR like a 8370 or a 7674?

Is there something that egbp adds that you dont see when looking at MAFv increases and EGT data?

Some shop just posted up a VF turbo dyno sheet and claims the turbo is maxed at 16.5 psi....and we all know thats not true....you can jack the lowend boost up to 26-28psi and pick up tons of low end tq compared to 16.5 psi.....so what is their EGBP data showing that makes them claim that you cant make more power over 16.5 when its been proven a billion times that you can pick up tons of tq?
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Old 11-13-2011, 12:40 AM   #430
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Quote:
Originally Posted by Phatron
how is the data used? can you just post some of your numbers and ratios? and conclusions drawn? you can pm if you want, unless others are interested....

For this turbo, once it stops adding airflow.....you dont really have a choice to change wheels or housings....so there is only one option, move up to the 8374. Or is it possible to make a Franken EFR like a 8370 or a 7674?

Is there something that egbp adds that you dont see when looking at MAFv increases and EGT data?

Some shop just posted up a VF turbo dyno sheet and claims the turbo is maxed at 16.5 psi....and we all know thats not true....you can jack the lowend boost up to 26-28psi and pick up tons of low end tq compared to 16.5 psi.....so what is their EGBP data showing that makes them claim that you cant make more power over 16.5 when its been proven a billion times that you can pick up tons of tq?
Ill try to dig it up, but generally boost and egbp should follow less than 1:1. If you're using speed density you won't see airflow so as power rolls off as pressure rises you can check to see if the ratio rises 35psi boost with 30ish egbp. If you raise the pressure and the egbp increases at a different rate then you can begin to derive causes. I recall playing with a 35r when the gt wheels were new and wondering if I could run a bigger compressor on the same turbine. Egbp rose linear with boost pressure which to me meant that the compressor was maxed but not the turbine still had head room. Freeing up the exhaust or playing with a larger header would have done nothing.
Do you need it to tune? No
Does it help to derive cause yes. Egts are affected by air fuel ratio so the egbp just adds another data set
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Old 11-13-2011, 04:27 AM   #431
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Good discussion!
Your example with 35 psi boost and only 30 psi back pressure seems a little far fetched? My limited experience is that even a ratio of 1:1 is very hard to reach. Not sure what others experience is with this?
My former DOM3 (30R with the small-ish 8cm turbine) had a 1:1,5 boost t back pressure ratio and could not hold boost steady up top.
Quote:
Originally Posted by reid-o View Post
Egts are affected by air fuel ratio so the egbp just adds another data set
My gut feeling is that a higher EGBP ratio also leads to a higher EGT with climbing boost/rpm: my current much larger turbine runs much lower EGT at the same AFR and same boost...
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Old 11-13-2011, 07:47 AM   #432
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Originally Posted by Phatron View Post
how is the data used?
egbp vs map can be very useful if you have options to change wheels and housings. It will tell you where to go next in the pursuit of whatever you are after (spool vs top end). Most don't bother to measure it directly though. They just rely on dyno info.

Assuming that the EFR's are pure match sets and that there won't be future options for mixing and match is shortsighted. Assuming solid product acceptance, I'm sure there will be more A/R options to come, as well and wheels. That will make egbp/map matching easy.

1:1 isn't uncommon for a race motor. Its very rare for a street motor. I haven't measured this yet on a Subaru (been on the list of things to do), but I wouldn't be surprised if a 2.0L with a VF is in the 2:1 territory and a 2.5L with a TD04 is closer to 3:1. Those are guesses, so don't take it to the bank.
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Old 11-13-2011, 02:02 PM   #433
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Dom thanks body, just came back from Vancouver cold as **** and people can’t drive there for ****......

As far as the actuator i finger tight the screw because i though we will get **** loads of boost, so it can be tighten allot more, or we can always swap the spring if needed. The boost climbs up so fast it’s like I’m on stock turbo, I need some more miles put in before the tune, stay tuned!
Read the manual, there is supposed to be some amount of preload on the rod for minimum boost and you add preload from there to go up.
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Old 11-13-2011, 02:12 PM   #434
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right now 10 psi is perfect for engine break in, why the **** should i need more?
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Old 11-13-2011, 02:43 PM   #435
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Quote:
Originally Posted by thefoos

egbp vs map can be very useful if you have options to change wheels and housings. It will tell you where to go next in the pursuit of whatever you are after (spool vs top end). Most don't bother to measure it directly though. They just rely on dyno info.

Assuming that the EFR's are pure match sets and that there won't be future options for mixing and match is shortsighted. Assuming solid product acceptance, I'm sure there will be more A/R options to come, as well and wheels. That will make egbp/map matching easy.

1:1 isn't uncommon for a race motor. Its very rare for a street motor. I haven't measured this yet on a Subaru (been on the list of things to do), but I wouldn't be surprised if a 2.0L with a VF is in the 2:1 territory and a 2.5L with a TD04 is closer to 3:1. Those are guesses, so don't take it to the bank.
I picked a number offhand and was referring to a DSM. The point is still valid.
The egbp is not as popular a data set because subarus don't push as much pressure. But the intake egbp ratio is a common data point for people that tune evos and supras. It doesn't help with the actual tuning process but becomes important to determine the part upgrade process. I understand why tuners don't go through the effort to log this. The last thing they want is to have a data that points to the parts they recommended as being limited.
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Old 11-13-2011, 11:58 PM   #436
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i defiantly love the way the build turned out, I’m driving around town in 5th gear 40 mph at 2500 rpm and the car has no problems even going uphill. Just hit 500 miles mark on the engine!
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Old 11-14-2011, 01:58 AM   #437
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Still, I'm looking forward to the results in this thread. The EFR turbos have some great technology and I really hope they can iron out the supply problems and other issues that are cropping up. The more technology we have to choose from, the better off we all are.
Well said! Manufacturer innovations = more choices for consumers!
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Old 11-14-2011, 11:13 AM   #438
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i defiantly love the way the build turned out, Im driving around town in 5th gear 40 mph at 2500 rpm and the car has no problems even going uphill. Just hit 500 miles mark on the engine!
you better call the shop and get on the schedule for a tune buddy!@!@@!!
this weeks mostly filled up already. saturdays still open though
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Old 11-14-2011, 11:52 AM   #439
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Originally Posted by Beetspeed View Post
Your example with 35 psi boost and only 30 psi back pressure seems a little far fetched? My limited experience is that even a ratio of 1:1 is very hard to reach. Not sure what others experience is with this? My former DOM3 (30R with the small-ish 8cm turbine) had a 1:1,5 boost t back pressure ratio and could not hold boost steady up top.
great post walter - you are definitely on the right track. The "ideal" setup of higher intake boost pressure than exh manifold pressure (as you mentioned: 35psi intake and 30 psi exhaust) is referred to in the engineering world as a "Positive Delta-P". Not at all far-fetched and acheving this is common with many of our turbokits. The egbp or emap measurement is actually a far more important metric than most will appreciate. If the intake pressure is *higher* than exhaust pressure -> the compressor wheel is turning the engine over (literally). A properly setup twinscroll kit with good engine prep will be right in this ballpark

your former dom3 turbo was wayy out of the ball park becuase it was a little itty baby turbine wheel with a big compressor wheel - mismatch turbos look great on dynos but thats it

Quote:
Originally Posted by Beetspeed View Post
My gut feeling is that a higher EGBP ratio also leads to a higher EGT with climbing boost/rpm: my current much larger turbine runs much lower EGT at the same AFR and same boost...
the reason a high EGBP ratio causes high EGT is because of the extreme reversion caused from the egbp pushing exhaust gasses and unburned hydrocarbons back into the cylinder (not just air/fuel/spark).

Quote:
Originally Posted by reid-o View Post
The egbp is not as popular a data set because subarus don't push as much pressure. But the intake egbp ratio is a common data point for people that tune evos and supras.
really this should be monitored on all types of engine setups and turbo configurations - its the ultimate measurement of how well the system as a whole is working
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Old 11-14-2011, 02:34 PM   #440
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Originally Posted by Full-Race Geoff

great post walter - you are definitely on the right track. The "ideal" setup of higher intake boost pressure than exh manifold pressure (as you mentioned: 35psi intake and 30 psi exhaust) is referred to in the engineering world as a "Positive Delta-P". Not at all far-fetched and acheving this is common with many of our turbokits. The egbp or emap measurement is actually a far more important metric than most will appreciate. If the intake pressure is *higher* than exhaust pressure -> the compressor wheel is turning the engine over (literally). A properly setup twinscroll kit with good engine prep will be right in this ballpark

your former dom3 turbo was wayy out of the ball park becuase it was a little itty baby turbine wheel with a big compressor wheel - mismatch turbos look great on dynos but thats it

the reason a high EGBP ratio causes high EGT is because of the extreme reversion caused from the egbp pushing exhaust gasses and unburned hydrocarbons back into the cylinder (not just air/fuel/spark).

really this should be monitored on all types of engine setups and turbo configurations - its the ultimate measurement of how well the system as a whole is working
Normally subaru tuning doesnt max out pressure ratios so there's really little need to look at trends in egbp as the focus is to achieve mbt at a moderate pressure ratio especially on pump.
Maybe if we changed strategies and lowered compression ratio and pushed 30psi it would become a bit more common.


Glad you're liking your setup bariga!
Anxious for results too
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Old 11-14-2011, 02:39 PM   #441
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Quote:
Originally Posted by Beetspeed
Good discussion!
Your example with 35 psi boost and only 30 psi back pressure seems a little far fetched? My limited experience is that even a ratio of 1:1 is very hard to reach. Not sure what others experience is with this?
My former DOM3 (30R with the small-ish 8cm turbine) had a 1:1,5 boost t back pressure ratio and could not hold boost steady up top.

My gut feeling is that a higher EGBP ratio also leads to a higher EGT with climbing boost/rpm: my current much larger turbine runs much lower EGT at the same AFR and same boost...
Since egt is affected by a/f and timing it's not a static data set so it's hard to use it to derive cause.
But I always laugh when tuners say things like choked up top based on a torque curve or that the hot side is too small. How can you possibly know based on outcome data without controls in place? They're just guessing at that point. Sorry for the thread jack
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Old 11-14-2011, 04:09 PM   #442
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But I always laugh when tuners say things like choked up top based on a torque curve or that the hot side is too small. How can you possibly know based on outcome data without controls in place? They're just guessing at that point. Sorry for the thread jack

that's where you are incorrect. WGDC is a big indicator of the back pressure and how choked up a turbo is at any point, not just up top.

Many of you have heard these cars first hand where the EWG barks during a pull instead of being a smooth roar. Barking by itself is not the indicator, but barking at high boost is. It shows you that the wastegate is spending more time shut forcing exhaust through the turbine. It shows that the turbo is being asked to make too much boost for the turbine setup. If you aren't bypassing a lot of exhaust to reach your target boost, you can't possibly be positive delta-p. I don't need EGBP to know this. However, you can't tell if you ARE at a positive delta based on that; just that you are NOT.

Does that make sense to you? If not, I can try to rephrase it.
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Old 11-14-2011, 04:41 PM   #443
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that's where you are incorrect. WGDC is a big indicator of the back pressure and how choked up a turbo is at any point, not just up top.

Many of you have heard these cars first hand where the EWG barks during a pull instead of being a smooth roar. Barking by itself is not the indicator, but barking at high boost is. It shows you that the wastegate is spending more time shut forcing exhaust through the turbine. It shows that the turbo is being asked to make too much boost for the turbine setup. If you aren't bypassing a lot of exhaust to reach your target boost, you can't possibly be positive delta-p. I don't need EGBP to know this. However, you can't tell if you ARE at a positive delta based on that; just that you are NOT.

Does that make sense to you? If not, I can try to rephrase it.
Yes I understand. You're simply disputing that the indicator is not the only one but not that the ratio is useless to know.

I wasn't suggesting that it was the only indicator. I was suggesting the meaning implied by the ratio.

Last edited by reid-o; 11-14-2011 at 04:53 PM.
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Old 11-14-2011, 05:18 PM   #444
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Yes I understand. You're simply disputing that the indicator is not the only one but not that the ratio is useless to know.

I wasn't suggesting that it was the only indicator. I was suggesting the meaning implied by the ratio.

ah gotcha.

Knowing the exact ratio is not that important.
Knowing your approximate ratio is good information. So is turbo shaft speed, but that is rarely used as well.

Ron,
when you are running 23-24psi of boost on a VF, you are WAAAAAY negative-delta. You have all but eliminated any scavenging effect that occurs during valve overlap. You are gaining a ton of torque for the same reason NA engines make more torque with some restriction. You are increasing cylinder pressure dramatically and it isn't with boost, it's with exhaust. However, you are using target boost as a method to increase exhaust pressure and force feed the cylinders giving them a starting pressure of 40psi instead of 20psi (estimated numbers based on the amount the ratio changes with increased levels of boost). Even with a smaller amount of air/fuel emulsion entering the cylinders, the higher effective compression ratio is giving you all that torque. The VF turbo IS maxed out. The turbine housing is choked up. On pump gas it's a recipe for failure, but on fuels that hardly detonate you can get away with it; especially with a Subaru. Peak VE on a 2.5L comes in around 4k rpm, add that to the ability to add a few more degrees of timing to get closer to MBT Timing and you can make a butt-ton of torque on a small turbo. It's safer to use a GT3071R (the only real 30R in my opinion) to do it, but the vf can.
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Old 11-15-2011, 01:35 AM   #445
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Almost 600 miles, 10 psi is hauling ass! maybe i should just keep it at 10 PSI
0 oil consumption! MPS +++

Guess what more P&L parts are failing! Fuel rail leaks tiny bit of fuel from NTP thread maybe because they used to much Teflon tape?
First it was the regulator now its a rail, P&L WTFFFFFFFFFFFFF?

Installed new turbo blanket
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Old 11-15-2011, 01:41 AM   #446
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thanks for the update! so when is the next tuning session and what are its goals?
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Old 11-15-2011, 02:02 AM   #447
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Lookin' clean!
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Old 11-15-2011, 10:43 AM   #448
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Almost 600 miles, 10 psi is hauling ass! maybe i should just keep it at 10 PSI
0 oil consumption! MPS +++

Guess what more P&L parts are failing! Fuel rail leaks tiny bit of fuel from NTP thread maybe because they used to much Teflon tape?
First it was the regulator now its a rail, P&L WTFFFFFFFFFFFFF?

Installed new turbo blanket
Where did you source that turbo blanket? I want one too

I've heard teflon tape on gas fittings is a no-no. I use the gasoline safe paste.
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Old 11-15-2011, 11:16 AM   #449
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the consensus on google is that gas eats teflon tape....

dei turbo blanket

http://compare.ebay.com/like/2306263...=sbar&_lwgsi=y
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Old 11-15-2011, 11:29 AM   #450
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I'd like to see p&l motorsporta step in here and back up their product so far it's ****
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