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Tune with a downpipe.....why?

turbodog

By turbodog
in Logan's Run

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BAC5.2 Grand Master

BAC5.2

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I'm sorry Turbodog, I'm not interested in playing your little "changing rules" game. Whether or not you choose to believe me, and however you choose to misinterpret my responses is none of my concern. I am most certainly not interested in writing out the fundamentals of fluid dynamics in crayon for you either.

 

You'll have to forgive the occasional typo, I'm responding via my iPhone.

[URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard
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SeeeeeYa Mentor

SeeeeeYa

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While I've long known that adequate WG flow was necessary to prevent boost creep, and why, it wasn't until this thread, and BAC5.2's explanation of the siphoning involved that I now see how boost spikes happen.

 

Not all threads provide a learning experience.

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turbodog Rising Star

turbodog

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I'm sorry Turbodog, I'm not interested in playing your little "changing rules" game. Whether or not you choose to believe me, and however you choose to misinterpret my responses is none of my concern. I am most certainly not interested in writing out the fundamentals of fluid dynamics in crayon for you either.

 

You'll have to forgive the occasional typo, I'm responding via my iPhone.

 

Discussion of catless = changing rules? Oh, sorry about that. Are we not allowed to talk about exhaust cutouts either? Because that's a 3 ft pipe after the turbo. Far too different.

 

I'm sorry, but you've really gone off the reservation with this whole flat plate = better boost control. Again, I do understand the concept of perpendicular flow siphoning action, but there's just no way it makes enough of a difference here.

 

Prove or retract. Maybe you could work up a CFD model for us.

 

If anything, I would claim that with the flat plate, the wastegate gases re-enter the main exhaust stream at a 90 degree angle, causing the turbine to see significant back pressure - which has been the traditional explanation about why this flat plate is no good for power. Maybe it is good for boost control? This is new to me.

 

I'm confident though that a ported wastegate and bellmouth flow better that any stock location configuration

 

Regardless, this thread needs to go back on topic. Does anyone actually believe that a flat plate downpipe provides better boost control vs. a belmouth? Would we be safe installing a flat plate downpipe with a single high flow cat? Would we see gains?

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turbodog Rising Star

turbodog

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While I've long known that adequate WG flow was necessary to prevent boost creep, and why, it wasn't until this thread, and BAC5.2's explanation of the siphoning involved that I now see how boost spikes happen.

 

Not all threads provide a learning experience.

 

It's not every day we get to bask in the glory of BAC5.2's brilliants. ;)

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BAC5.2 Grand Master

BAC5.2

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Discussion of catless = changing rules? Oh, sorry about that. Are we not allowed to talk about exhaust cutouts either? Because that's a 3 ft pipe after the turbo. Far too different.

 

Bringing up different A/R's, different turbine housings, now changing between catless and catted. Everything you can do to steer the discussion away from a relatively simple question ("do you need a tune") in order to try and loophole your way out of not knowing what you are talking about.

 

I'm sorry, but you've really gone off the reservation with this whole flat plate = better boost control. Again, I do understand the concept of perpendicular flow siphoning action, but there's just no way it makes enough of a difference here.
As a matter of fact, YOU jumped the generalization wagon when you made an assumption about my line of logic (which, as I pointed out, I was NOT indicating).

 

The topic was "do you need a tune for an aftermarket DP". My reply was yes, and I discussed (correctly) why you do (unpredictable boost control) and also discussed (correctly) why a bellmouth causes boost-creep in an otherwise completely stock vehicle.

 

Prove or retract. Maybe you could work up a CFD model for us.
Sorry, I won't do your Fluids homework for you. You keep saying "prove or retract." How about I don't. I proved my knowledge in front of a committee of advisors, and an audience in a packed conference room when I successfully defended my thesis. You quoted Wikipedia (without citation). I've got absolutely nothing to gain by breaking out crayons to draw you a pretty picture of gas flow.

 

If anything, I would claim that with the flat plate, the wastegate gases re-enter the main exhaust stream at a 90 degree angle, causing the turbine to see significant back pressure - which has been the traditional explanation about why this flat plate is no good for power. Maybe it is good for boost control? This is new to me.
Nowhere have I claimed that a flat-flange DP is better for making power, or is a better performer in general. If power is your goal, putting an aftermarket downpipe on the car without tuning is not the way to get it.

 

I'm confident though that a ported wastegate and bellmouth flow better that any stock location configuration
No one is saying anything different.

 

Regardless, this thread needs to go back on topic. Does anyone actually believe that a flat plate downpipe provides better boost control vs. a belmouth? Would we be safe installing a flat plate downpipe with a single high flow cat? Would we see gains?
I do believe that, everything else completely stock, a flat-plate DP (like that HKS) would show significantly decreased tendency to spike, and would be generally "reliable" on an otherwise stock vehicle. I would not, however, recommend it for some of the reasons I discussed. A drop in post-turbine pressure from the increased pipe diameter WILL impact intake air flow.

 

The drop in post-turbine pressure could still (and likely would) cause boost to come on TOO quickly, moreso than the ECU can safely or reliably handle (enrichment delay could cause lean conditions during spool). That'd cause knock, which in turn would rob power and degrade potential longevity.

 

If it's gains you want, spend your money on tuning the car properly (even if it's just boost parameters to maintain stock-like reliability).

 

Now I'm REALLY done with this thread. I can see no end to your attempts at argument, and it is obvious that you have no interest in actually learning the answer to your questions. You simply want to argue, and I'll no longer have a part in that.

[URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard
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bigjweb Mentor

bigjweb

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Dude look at it like this: Your car comes with a tune that is optimized for XYZ. THe ECU can makes changes based on certain variables that are pre-determined for different conditions. When you change something that significantly alters the way the motor functions, such as the way a turbo boosts, the way a motor functions under those same circumstances becomes different. Now the motor cannot make adjustments accordingly if extreme things happen because it was not programmed to do so. Something has to give.
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Penguin Grand Master

Penguin

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There is no convincing argument for tuning due to an aftermarket downpipe, uppipe, or anything else. You can control lean running conditions with a manual boost controller, and a good quality blow off valve. The engine computer is more than capable of learning the new conditions and running safely.

 

ECU tuning is a complete scam to make dip shit with a lap top and OBD II port some money. Usually they do a bad job and blow up cars.

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turbodog Rising Star

turbodog

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Bringing up different A/R's, different turbine housings, now changing between catless and catted. Everything you can do to steer the discussion away from a relatively simple question ("do you need a tune") in order to try and loophole your way out of not knowing what you are talking about.

 

As a matter of fact, YOU jumped the generalization wagon when you made an assumption about my line of logic (which, as I pointed out, I was NOT indicating).

 

The topic was "do you need a tune for an aftermarket DP". My reply was yes, and I discussed (correctly) why you do (unpredictable boost control) and also discussed (correctly) why a bellmouth causes boost-creep in an otherwise completely stock vehicle.

 

Sorry, I won't do your Fluids homework for you. You keep saying "prove or retract." How about I don't. I proved my knowledge in front of a committee of advisors, and an audience in a packed conference room when I successfully defended my thesis. You quoted Wikipedia (without citation). I've got absolutely nothing to gain by breaking out crayons to draw you a pretty picture of gas flow.

 

Nowhere have I claimed that a flat-flange DP is better for making power, or is a better performer in general. If power is your goal, putting an aftermarket downpipe on the car without tuning is not the way to get it.

 

No one is saying anything different.

 

I do believe that, everything else completely stock, a flat-plate DP (like that HKS) would show significantly decreased tendency to spike, and would be generally "reliable" on an otherwise stock vehicle. I would not, however, recommend it for some of the reasons I discussed. A drop in post-turbine pressure from the increased pipe diameter WILL impact intake air flow.

 

The drop in post-turbine pressure could still (and likely would) cause boost to come on TOO quickly, moreso than the ECU can safely or reliably handle (enrichment delay could cause lean conditions during spool). That'd cause knock, which in turn would rob power and degrade potential longevity.

 

If it's gains you want, spend your money on tuning the car properly (even if it's just boost parameters to maintain stock-like reliability).

 

Now I'm REALLY done with this thread. I can see no end to your attempts at argument, and it is obvious that you have no interest in actually learning the answer to your questions. You simply want to argue, and I'll no longer have a part in that.

 

Actually, you're the one who pushed this thread off topic, let me refresh your memory:

 

http://legacygt.com/forums/showpost.php?p=3964605&postcount=34

 

It must be nice to feel superior to everyone else because you picked up a Ph.D. Congratulations! Someone disagrees? Well they're just wrong, beneath you and clearly not worth your time......please excuse me if I'm not impressed.

 

I know full well what I'm talking about, and have completely understood every hypothesis you have presented. Doesn't mean I have to believe you. Thanks.

 

Back on topic - YOU ABSOLUTELY DO NOT NEED AN ECU TUNE TO RUN AN AFTERMARKET DOWNPIPE SAFELY. Nothing in this thread so far has proven this statement wrong. Boost control otherwise can be adjusted for stability by other means - this has been my understanding for MANY years. Please prove this wrong

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turbodog Rising Star

turbodog

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ECU tuning is a complete scam to make dip shit with a lap top and OBD II port some money. Usually they do a bad job and blow up cars.

 

^This, to a limited extent. People are FAR too trusting of who they let modify their ECU's tuning.

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seabass07 Grand Master

seabass07

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Spoken like someone who has no clue about tuning. While there are many people just out to make a buck, there are plenty of people who know what they're doing that give up massive amounts of information for free. That is the best thing about the Subaru community IMO.
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