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      07-18-2013, 05:50 PM   #1
wheelj81
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Tuning the N54 in high altitude

Hey everyone! I'm new here and I wanted to start a thread just for those of us in the mile high club. I'm in Denver and I've just recently bought a Cobb AP. I've installed the Stage 1 Sport map and have no other mods other than a dual cone intake. Can everyone share your experiences and even the horror stories of tuning in high altitude?

My boost is regularly at 15 psi or so up here and scares the crap out of me with this 91 octane we have to run. I don't have easy access to E85 either.
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      07-18-2013, 09:12 PM   #2
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Originally Posted by wheelj81 View Post
Hey everyone! I'm new here and I wanted to start a thread just for those of us in the mile high club. I'm in Denver and I've just recently bought a Cobb AP. I've installed the Stage 1 Sport map and have no other mods other than a dual cone intake. Can everyone share your experiences and even the horror stories of tuning in high altitude?

My boost is regularly at 15 psi or so up here and scares the crap out of me with this 91 octane we have to run. I don't have easy access to E85 either.
My concerns exactly! Due to our gas and altitude i am trying to figure out how best to tune and mod differently
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      07-19-2013, 01:09 AM   #3
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In short bursts you don't need to be nervous. I use Cobb's ATR software here in Colorado to run 18psi or so peak, and falling to about 14psi at redline. 91 octane or E85. I just run a much different timing map for E85. But I don't run full throttle for more than 1/4 mile at a time. If you're concerned, sticking with Cobb's OTS maps works fine. But I really like E85.
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      07-19-2013, 07:12 AM   #4
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Originally Posted by Carl Morris View Post
In short bursts you don't need to be nervous. I use Cobb's ATR software here in Colorado to run 18psi or so peak, and falling to about 14psi at redline. 91 octane or E85. I just run a much different timing map for E85. But I don't run full throttle for more than 1/4 mile at a time. If you're concerned, sticking with Cobb's OTS maps works fine. But I really like E85.
How long have you been running your boost that high?
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      07-20-2013, 12:21 AM   #5
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Close to that since Cobb Stage1+ came out. 18+ since ATR came out.
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      07-20-2013, 06:51 PM   #6
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Close to that since Cobb Stage1+ came out. 18+ since ATR came out.
Since you've been using ATR and I'm new this. Is there any way to reduce some of the turbo lag? I feel like at 3k the turbo kicks in like a beast. I'd like to get a little more low end. I'm not tracking it so a bumping the around town power is what I'd like to do.
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      07-20-2013, 07:09 PM   #7
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You'd have to take some logs, but I've found that what I thought was lag was usually a timing issue where timing was being pulled when I first got full boost due to being near or over the target load. The hardware itself should not be laggy at 3k, even at high elevation. If it really is lag you have an issue with boost control or leaks.
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      07-20-2013, 10:00 PM   #8
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My logs look pretty clean. I'm not seeing a lot of timing corrections at all. And I've got no codes for boost leaks. Something else I need to look for?
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      07-20-2013, 11:40 PM   #9
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It's not about timing corrections due to knock. It's about all the timing getting pulled down hard by the ECU when you are close to or above the requested load. It will show up in your final timing values but not as a correction. And you can leak quite a bit before you get a code for it. So you'll have to investigate which one it is. I'll look at a log if you post it showing boost and timing.
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      07-21-2013, 04:05 PM   #10
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Here are a couple logs. The longer one had a few pulls with various gears. Mostly 3rd and 4th since I was on the highway. The second was a pull from 0-60ish. 1st and second gears. Let me know what you think! And thanks!

I had to zip the files because I couldn't upload them in native .csv format.
Attached Files
File Type: zip datalog5.zip (151.8 KB, 19 views)
File Type: zip datalog6.zip (10.0 KB, 17 views)
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      07-21-2013, 04:30 PM   #11
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Interesting. Mostly your timing looked as expected, but heat soak was taking its toll in the multi-gear final run. There were some times when you got boost fast even in lower gears, but that first and second higher gear pulls in the long file was bad...around 2.5 seconds to get full boost going from 2500-3200rpm. To me that's laggy for stock turbos and it wasn't timing. Since it's not doing it all the time I doubt it's a leak or a restriction. I wonder if one or both of your diverter valves has a leaky spot in it that you only hit sometimes? I have a similar problem lately and am wondering the same thing for myself. It would also be possible for one of the wastegates to not be completely closing sometimes, but that seems unlikely in my case since the dealership went through my system and replaced one turbo recently. Oh yeah, one other thing, the vacuum hoses that feed the vacuum canisters that run the wastegates might also be a possibility. I'm not aware of any other possibilities.
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      07-21-2013, 04:44 PM   #12
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Thanks for taking a look. Any thoughts on trouble shooting?
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      07-21-2013, 04:48 PM   #13
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On a simpler single turbo vehicle it's pretty easy to use Home Depot plumbing parts and an air compressor to pressure test the intake system and it's almost always worthwhile because it would probably catch potential diverter valve and vacuum hose issues. You might be able to do that on our systems but you wouldn't be able to use much pressure assuming you connected to the intake hoses where the air filter box connects to them. It's better when you can connect directly to the turbo inlet.

As far as the wastegates go I'm not sure if it would be worth the effort to try to get to them and apply vacuum to the actuators and actually see if they move as expected. If it's my wastegates it probably won't get fixed until I get new turbos :-).

Last edited by Carl Morris; 07-21-2013 at 04:48 PM. Reason: would->wouldn't
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      07-21-2013, 05:38 PM   #14
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Ok thanks for all the insight. You've been very helpful. One last question/thought. Do you think getting a pro tune would help or hurt in this situation?
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      07-21-2013, 05:44 PM   #15
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Assuming you're talking about PTF they do some to know more than pretty much everybody else about the tricks to getting things as good as possible. So yes, if you want to improve part throttle behavior and that sort of thing, assuming they understand how it's different at high elevation, they can improve your tune. But I'm skeptical a tune will help your lag issue. During the really laggy log your WGDC was at max and it wasn't helping. They can add more duty cycle but I don't think that will shut the wastegate any further.

I personally don't want a locked map from a pro tuner, though. Once I get something the way I want, I want to be able to understand it and help other people with it and make maps for various concentrations of E85 from it, etc..
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      07-21-2013, 06:21 PM   #16
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Another thought. Could it be that my intake needs a walnut shell blast? Might that be slowing it down?
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      07-21-2013, 11:47 PM   #17
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Some people benefit from that, but it's not going to solve the lag issue. If you're a DIYer the first thing would be to replace the vacuum lines to the canisters and if that doesn't make any difference think about replacing the diverter valves.
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      07-22-2013, 02:28 AM   #18
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I feel your pain and I'm only at 4K feet - so, they don't sell 93 here either.

I'm running JB4 with a fixed boost map (17psi max) on E85 mix. It's helped a lot. Now that summer is here, I'm having to deal with extreme IAT, though. I don't know which is worse. Very frustrating...
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      07-22-2013, 11:51 AM   #19
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Quote:
Originally Posted by Carl Morris View Post
Assuming you're talking about PTF they do some to know more than pretty much everybody else about the tricks to getting things as good as possible. So yes, if you want to improve part throttle behavior and that sort of thing, assuming they understand how it's different at high elevation, they can improve your tune. But I'm skeptical a tune will help your lag issue. During the really laggy log your WGDC was at max and it wasn't helping. They can add more duty cycle but I don't think that will shut the wastegate any further.

I personally don't want a locked map from a pro tuner, though. Once I get something the way I want, I want to be able to understand it and help other people with it and make maps for various concentrations of E85 from it, etc..
PTF should have some maps for elevation as we flew them out up here last year for a hands on tuning session and they tuned quite a few cars up here.
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      07-31-2013, 03:45 PM   #20
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Hey guys. I just picked up a 08 535xi and looking to do some tuning. I am pretty familiar with tuning as I had a twin turbo mustang I built and tuned myself, but totally new to the BMW scene. I am in the Denver area if anyone wants to chat or get together.

Sean
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      08-09-2013, 05:35 PM   #21
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In loveland CO on the way up to estes park they sell race gas. Its off the main highway by that lake. Ive seen 104 and higher octane there. Check that out may help.
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      08-15-2013, 04:33 PM   #22
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Sean,

I have a 2008 335xi in the Denver metro that's pretty tuned... let me know if I can be of help.
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