1.2 bar tune question
10-28-2016, 12:24 PM
#16
My guess is that simply looking at the map of a k16 does not tell the whole story as that map does not take into consideration the added inefficiencies associated with the installation on a 996, plumbing and IC restrictions, etc. As such, real world efficiency is probably closer to 1.0 rather than the theoretical 1.2 bar depicted on the map. And I stayed at a Holiday Inn last night...
10-28-2016, 01:00 PM
#17
Unless you are 100% certain that K16's can only efficiently go to 1.0 bar, the following statement that you made is misinformation: "If you are truly stock with K-16's, then 1.2 is too high". There is no ambiguity there. When someone does an internet search and your post comes up, they may take your statement as fact. If you want to pass along what you have heard on the internet, you should say something like, "I have heard that K16's are not efficient past 1.0 bar".
I have heard very good things about Kevin@UMW and I have little doubt that he is a great tuner. He seems to be on the more conservative side tuning-wise, so maybe he would rather not push a set of K16's to their limit, or would rather run K16's at a higher efficiency level than ~65%. But saying that K16's are not efficient past 1.0 bar is simply not true when looking at the KKK graph. It is easy to see that very soon after 1.2 bar, the efficiency of the turbo drops like a stone, not 1.0 bar.
And you say this is only theoretical and does not always apply in reality? Ok, so maybe the temp is not always ~68F outside and people can be at a different altitude... The only argument here would be to challenge the validity of the information, but to me it looks pretty legitimate.
As to differences between different cars, during such a discussion it is of course assumed that the car in question is in good working order. Thanks for the offer to help, but I don't think I need it. Variances between one 996TT and another (and between different K16 turbos) are very small, otherwise all cars would have custom tunes tailored to them from the factory.
The first link you posted also uses the same K16 turbo map as a reference and comes to the same conclusion that 1.2 bar is the maximum efficient boost pressure, barring gross temperature/altitude variances. The second link you posted comes to the same conclusion except for supermono who doesn't sound like they know what they are talking about and 996TT_STEVO who posted a very similar brief statement to your initial one above with no supporting evidence, and that directly contradicts the KKK turbo graph information.
Dan
Dan
You surely realize the graphs posted are at best an average of the data collected from the "engineering runs" of the KKK turbo (head in the oven, feet in the freezer, on average you feel fine). They do NOT take into account variation. I do not want to get into an internet war with you, but your conclusions and extrapolation of the results of those graphs is also incorrect and you should state that in your post. The graphs are theoretical and don't take into account variation of components, ambient conditions, assembly, etc. I just don't want someone to read your post and think the theoretical maps relate to their situation, get a tune to 1.2 and have catastrophic results.
RANT OVER!
cheers,
Statman
Last edited by wross996tt; 10-28-2016 at 02:07 PM.
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10-28-2016, 01:28 PM
#19
Three Wheelin'
I am really curious as to how folks are seeing greater than 1.0 bar sustained with stock wastegates. While I have seen my car 'spike' to 1.2 with my 100 octane tune, it's typically 1.0 flickering to 1.1 and my stock wastegates are very well adjusted.
10-28-2016, 02:43 PM
#21
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One way to see what your engine is capable of producing in terms of boost is to be in a higher gear and lower RPM (for example 3rd gear at 20000 RPM) then going WOT up a hill/incline.
10-28-2016, 03:14 PM
#22
Three Wheelin'
10-28-2016, 03:28 PM
#23
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I'm not saying that my EVOMS Stage II 996 Turbo will hold 1.2 bar from it first being indicated all the way to redline, because it won't. The length of time it will hold 1.2 bar depends I think on several (or more) factors.
Have you done a higher gear/lower RPM WOT pull uphil? The results will obviously not establish what boost the car will always produce in all situations, but it will indicate what the peak boost is and it will give you a general idea whether or not that boost is a spike or is somthing that can be sustained for some period of time.
Have you done a higher gear/lower RPM WOT pull uphil? The results will obviously not establish what boost the car will always produce in all situations, but it will indicate what the peak boost is and it will give you a general idea whether or not that boost is a spike or is somthing that can be sustained for some period of time.
10-28-2016, 03:30 PM
#24
Race Car
Wow, this is getting ridiculous. Some people you just can't get through to. They will continue to believe in what they believe, no matter what kind of information is presented to them. I have to multi-quote so I don't get into political trouble...
OP is asking whether or not his 1.2 bar tune is safe.
First you say it's too high, suggesting it is not safe. Wow, how did you know that? Did you analyze his data logs? OP must be freaking out right now. And then, "AFAIK, K16's are only good to 1.0 bar". To me that sounds like you are pretty sure about what you say even though you inserted AFAIK into the middle there - a statement of fact, then a step back, nice. And don't rag on me for bringing in efficiency of the system, you brought that up first, look it is in that first quote, last sentence, you know, the one with AFAIK in it.
Ok, let's define efficiently in this context. Considering that an old roots supercharger is ~60% efficient at best, a set of K16's running at 65% efficiency is pretty darn good, especially considering their max efficiency range is ~75%.
If you really have this kind of experience, you should know that using engineering data and theoretical models to back up a hypothesis is much better than believing someone who said something without any material evidence. How can you argue that a model from engineers that designed and built a turbo is a worse source of data than word of mouth from a tuner (however talented) that said so?
Is this a serious question, or just a needless deflection? Do you really want me to tell you why? There are about 20 reasons why Porsche decided to keep the boost at 0.7 and I think we both know what they are, so I am not going to start talking about it here.
Wow, with all your experience I cannot believe you would type stuff like that, to discount an engineering model with such ease. Do you think the stock program in all 996TT ECU's is different? If manufacturing variances were as large as you suggest, each car would have to have a custom tune from the factory. How do you know a 777 will fly with the wings it has? There are engineering models showing it will, but for all you know the manufacturing variances in different wing manufacturing batches could be so large that the plane would not take off. You make it sound like no matter what kind of test data you have, you can never be sure of the next copy of something you have manufactured because it could be too different from the original.
Wrong, they take into account ambient temperature and atmospheric pressure. There's the variation of components again... maybe a brand new K16 out there can only boost to 0.6 bar, and no more due to its components. You do know what kind of precision is required to machine a turbocharger impeller and its housing, right? Assembly, are you really being serious? Maybe Herr Hans left a bolt loose when doing the test 
Wouldn't it just be easier to say, maybe you were right and I was wrong. I know that won't happen. We could go round all day (this is my last post in response to this topic), but the bottom line is that I have some pretty convincing evidence to support my case, and you have word-of-mouth from sources who did not manufacture the turbo, simple as that. Did you hear, someone said that it is going to be dark for 15 days in November this year! If you don't have some kind of evidence to back up your argument, why respond...
To the OP - the safety of your tune has nothing at all to do with the fact the boost goes to 1.2 bar, but to do with the tuning program itself. The best thing to do would be to get with a tuner, pull the ECU program and have the tuner analyze it. They may also ask for datalogs of the car while running to ensure the tune is safe. Anyone who tells you it is not safe solely due to it boosting to 1.2 bar without any other data is just guessing.
Dan
OP is asking whether or not his 1.2 bar tune is safe.
Ok, let's define efficiently in this context. Considering that an old roots supercharger is ~60% efficient at best, a set of K16's running at 65% efficiency is pretty darn good, especially considering their max efficiency range is ~75%.
And to your knowledge, how many turbos were tested (of the entire population manufactured)? Where were they tested? On a bench or in a closed system? Were the testes replicated? What was the measurement error? I can show you graphs for the performance of thousands of products...anyone can make a graph. Without context, the graph ha little utility to those of us dealing with the turbo in OUR CARS.
So you can look at data and decide if it is legitimate? You apparently don't even question the precision of the measurement devices. That is quite a talent. In my line of work you would be a multi billionaire with that capability. Perhaps you should consult with Samsung on their Galaxy Note 7...imagine all of the data those engineers created only to find their theoretical models didn't work in the real world.
So you can look at data and decide if it is legitimate? You apparently don't even question the precision of the measurement devices. That is quite a talent. In my line of work you would be a multi billionaire with that capability. Perhaps you should consult with Samsung on their Galaxy Note 7...imagine all of the data those engineers created only to find their theoretical models didn't work in the real world.
You have data to support the amount of variation between 996TT's or their components? To say it is small is completely unsupported by data. Having worked with fortune 100 manufacturing and design companies including aerospace for 35 years...my experience regarding material, manufacturing & assembly, measurements systems, etc. is that variation is quite a bit larger than you suggest. Perhaps you should restate your claim and say something like "I have no idea how much variation there is between cars and therefore can not comment on the applicability of the theoretical graphs to your car".
You surely realize the graphs posted are at best an average of the data collected from the "engineering runs" of the KKK turbo (head in the oven, feet in the freezer, on average you feel fine). They do NOT take into account variation. I do not want to get into an internet war with you, but your conclusions and extrapolation of the results of those graphs is also incorrect and you should state that in your post. The graphs are theoretical and don't take into account variation of components, ambient conditions, assembly, etc. I just don't want someone to read your post and think the theoretical maps relate to their situation, get a tune to 1.2 and have catastrophic results.
You surely realize the graphs posted are at best an average of the data collected from the "engineering runs" of the KKK turbo (head in the oven, feet in the freezer, on average you feel fine). They do NOT take into account variation. I do not want to get into an internet war with you, but your conclusions and extrapolation of the results of those graphs is also incorrect and you should state that in your post. The graphs are theoretical and don't take into account variation of components, ambient conditions, assembly, etc. I just don't want someone to read your post and think the theoretical maps relate to their situation, get a tune to 1.2 and have catastrophic results.
Wouldn't it just be easier to say, maybe you were right and I was wrong. I know that won't happen. We could go round all day (this is my last post in response to this topic), but the bottom line is that I have some pretty convincing evidence to support my case, and you have word-of-mouth from sources who did not manufacture the turbo, simple as that. Did you hear, someone said that it is going to be dark for 15 days in November this year! If you don't have some kind of evidence to back up your argument, why respond...
To the OP - the safety of your tune has nothing at all to do with the fact the boost goes to 1.2 bar, but to do with the tuning program itself. The best thing to do would be to get with a tuner, pull the ECU program and have the tuner analyze it. They may also ask for datalogs of the car while running to ensure the tune is safe. Anyone who tells you it is not safe solely due to it boosting to 1.2 bar without any other data is just guessing.
Dan
10-28-2016, 04:32 PM
#25
Three Wheelin'
To the OP - the safety of your tune has nothing at all to do with the fact the boost goes to 1.2 bar, but to do with the tuning program itself. The best thing to do would be to get with a tuner, pull the ECU program and have the tuner analyze it. They may also ask for datalogs of the car while running to ensure the tune is safe. Anyone who tells you it is not safe solely due to it boosting to 1.2 bar without any other data is just guessing.
Dan
Dan
10-28-2016, 06:58 PM
#26
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A few facts.. The compressor wheel in STOCK K16's is actually a K24 compressor wheel. The stock compressor wheel will NOT have the ability to sustain 1.20 bars or greater to Redline thru 3rd to 6th gear. If you are in 4th gear at 140 mph and greater the boost spike at 1.2 bars at 4200 in second gear will never appear due to the gear splits at 5500 to 7000RPM's in 5th and 6th gear..
Tuning might allow for a 1.2bars boost request, but actual boost output in a sustained setting/run will not appear.
Sure one can produce a 1.25 pressure level with tuning (never say never) but you are outside of this compressor wheel map over 4800 engine RPM's when talking about those pressures. You are just turning the turbochargers into a heat pump/blow dryer. On stock intercoolers it's foolish. Engine knock retard is increased, and if the tuner kept the factory safe guard in place>> Boost will be reduced and timing will be reduced when the temp reach the set point temperature limits..
Installing efficient intercoolers will mask this effect for a specific amount of time.
A boost spike in the RPM range to 1.2 bars can occur briefly.. Boost, sustained at those levels to Redline in ALL gears does not make sense. Log your intake temps and see what happens.
Tuning might allow for a 1.2bars boost request, but actual boost output in a sustained setting/run will not appear.
Sure one can produce a 1.25 pressure level with tuning (never say never) but you are outside of this compressor wheel map over 4800 engine RPM's when talking about those pressures. You are just turning the turbochargers into a heat pump/blow dryer. On stock intercoolers it's foolish. Engine knock retard is increased, and if the tuner kept the factory safe guard in place>> Boost will be reduced and timing will be reduced when the temp reach the set point temperature limits..
Installing efficient intercoolers will mask this effect for a specific amount of time.
A boost spike in the RPM range to 1.2 bars can occur briefly.. Boost, sustained at those levels to Redline in ALL gears does not make sense. Log your intake temps and see what happens.
10-28-2016, 07:00 PM
#27
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also, the rest of the log data should include Intake air temps, ignition angle and individual cylinder knock retard, and engine load. And for boost control, Requested Boost, and N75 duty cycle..
10-28-2016, 07:27 PM
#28
10-28-2016, 07:28 PM
#29
Three Wheelin'
Not sure if you're referring my logfile snippet or in general.
But I think we're on the same page, as I don't claim my car holds 1.1 or 1.2 bar for very long--back to my original comment about the spike. And again, I'm just curious as to how others can really see more than 1.0 sustained given the mechanical limitations of the wastegates.
by 4900 rpm it's down to 14.5psi (1bar, correct) and continues to taper to 13psi by 5500ish with IATs in the mid 80s at peak boost climbing to mid 90s by 5500.
Sambo built me a safe 100 octane tune, I think we went through 3-4 revisions to really dial it in. In no way shape or form would I run this tune on crappy 91 pump gas. Car runs great, is very, very consistent and has excellent midrange torque.
10-28-2016, 07:32 PM
#30
Three Wheelin'