BMW M3 Forum (E90 E92)

BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   M3Post - BMW M3 Forum > E90/E92 M3 Technical Topics > Engine, Transmission, Exhaust, Drivetrain, ECU Software Modifications
 
PYSPEED
Post Reply
 
Thread Tools Search this Thread
      06-03-2009, 11:43 PM   #23
dcstep
Brigadier General
 
Drives: '09 Cpe Silverstone FR 6MT
Join Date: Nov 2008
Location: Colorado

Posts: 4,927
iTrader: (0)

Garage List
2009 M3  [4.00]
Quote:
Originally Posted by gemini330zhp View Post
Did you get the Dinan Exhaust in addition to all your mods?

If you're asking me, I've got the Active Autowerkes Signature exhaust, Dinan throttle bodies, Dinan 4.10 final drive, Dinan stage one suspension, Dinan chip, UUC SSK and I'm waiting on a filter, I forget which one, but they all cost and look the same and get good reviews.

I recommend the FD, spring set exhaust and UUC without reservation. The throttle bodies and chip are not working at high altitude and the only positive so far is the increased rpm and top speed with the chip. I'm playing with fuel and octane, which is causing me problems at altitude. You guys at sea level may get much better results.

Dave
__________________
dcstep is offline   United_States
0
Reply With Quote
      06-04-2009, 03:22 PM   #24
Finnegan
Major General
 
Finnegan's Avatar
 
Drives: Sapphire Black/Black Z4Mc
Join Date: Oct 2008
Location: At the track..or wishing I were at the track

Posts: 6,439
iTrader: (17)

Quote:
Originally Posted by dcstep View Post
BTW PG, what do you think about my octane issues? These are all low or no ethanol fuels (under 10%). First I tried 105 octane and lost significant hp and 100 octane is still losing, but I'm not sure how much yet. Do you think the high altitude and low atomospheric oxygen, combined with the higher flash point may be what's losing power vs. the gains you experienced at sea level??

What do you think of my plan to mix a little E85 with 80% 91-octane?

Dave
It's not just low atmospheric oxygen that's the issue. It's the compression of the engine. When the altitude increases the compression of an engine effectively drops. Simply put you're not running 12:1 at that altitude. That's why you can get away with lower octane fuel at altitude--you find 85 octane in high altitude areas but never at lower altitudes where the lower octane could cause detonation.

The engine cannot maximize power the way it can at sea level and power will always be reduced unless you add an S/C or turbo. There's just no way to have the compression at a level that will give you max power (or anywhere near it). The extension of this may be that the tune buys you smoothness and higher RPM but very little performance gain as there just isn't enough oxygen or effective compression ratio available to use those optimized settings.

Note: What I'm saying is not true with turbo engines as the turbos are going to work harder and will keep the compression ratio constant--or even overboosted if tuned--so you can get better performance at high altitude via tuning/octane in that case. FI engines are a huge plus at attitude (even back in WWII we used superchargers to keep engines at full power at high altitude--a plane w/o a S/C was at a huge disadvantage in ceiling capability). The N54 engine and other FI engines have a significant advantage at altitude--no way around that. As I understand it a turbo FI rather than S/C FI is going to have the ability to fine-tune adapt (keep boost target) while an S/C is pretty "locked in" due to direct connection to the engine for driving the compressor.

Now as to whether the extra octane over what's required is going to hurt performance--that I do not know. But since you're not running any kind of FI it's not going to help you.

Last edited by Finnegan; 06-04-2009 at 04:03 PM.
Finnegan is offline   United_States
0
Reply With Quote
      06-04-2009, 03:30 PM   #25
J08M3
Major General
 
J08M3's Avatar
 
Drives: 2011 M3 COUPE
Join Date: May 2008
Location: NEW YORK

Posts: 6,012
iTrader: (8)

good explanation
__________________
J08M3 is offline   United_States
0
Reply With Quote
      06-04-2009, 11:35 PM   #26
CanM3
Private
 
CanM3's Avatar
 
Drives: 2008 JB M3
Join Date: May 2009
Location: Calgary, Canada

Posts: 82
iTrader: (0)

Quote:
Originally Posted by Finnegan View Post
It's not just low atmospheric oxygen that's the issue. It's the compression of the engine. When the altitude increases the compression of an engine effectively drops. Simply put you're not running 12:1 at that altitude. That's why you can get away with lower octane fuel at altitude--you find 85 octane in high altitude areas but never at lower altitudes where the lower octane could cause detonation.

The engine cannot maximize power the way it can at sea level and power will always be reduced unless you add an S/C or turbo. There's just no way to have the compression at a level that will give you max power (or anywhere near it). The extension of this may be that the tune buys you smoothness and higher RPM but very little performance gain as there just isn't enough oxygen or effective compression ratio available to use those optimized settings.

Note: What I'm saying is not true with turbo engines as the turbos are going to work harder and will keep the compression ratio constant--or even overboosted if tuned--so you can get better performance at high altitude via tuning/octane in that case. FI engines are a huge plus at attitude (even back in WWII we used superchargers to keep engines at full power at high altitude--a plane w/o a S/C was at a huge disadvantage in ceiling capability). The N54 engine and other FI engines have a significant advantage at altitude--no way around that. As I understand it a turbo FI rather than S/C FI is going to have the ability to fine-tune adapt (keep boost target) while an S/C is pretty "locked in" due to direct connection to the engine for driving the compressor.

Now as to whether the extra octane over what's required is going to hurt performance--that I do not know. But since you're not running any kind of FI it's not going to help you.

Dont get me wrong, and I dont mean to sound like a di*k....but your explanation is wrong.....
A cars compression ratio is fixed, its determined by swept volume, piston configuration, cylinder deck height......
What you are talking about is volumetric efficiency, that is to say how well that fixed volume is used.
At higher altitudes, the air is 'thinner' there is less o2 available, so the VE is decreased. The use of forced induction packs the cylinder, increasing the VE....this will increase the cylinder pressures, but trust me, the compression ratio is a fixed ratio, it does not change...but cylinder pressures change constantly....
The only advantage a turbo has over a Supercharger is the turbo is utilizing a waste stream (the exhaust) to charge the cylinders...it uses a little mini gas turbine, same principle as a steam turbine, just on a much smaller scale. The turbo 'works' as hard at sea level as it does at high altitude, the thing that changes is the waste gate position, less boost required, more air is bled off thru the waste gate.
I much prefer supercharging to turbocharging....there is a bit of a tradeoff as there is a bit of a parasitic element to supercharging, but they are so much more reliable. Turbo's run at extremely high temps, require zoomy metallurgy, require an extensive oiling system, very sensitive to downstream pressure changes, then the infamous turbo lag, not present in supercharging.
At full throttle, a supercharger and a turbo charger would both put out max rated boost......as mentioned before this would be dependant upon waste gate or bleed valve settings.
So, dont mix up compression ratio and cylinder pressures, they are two totally different things.......
CanM3 is offline  
0
Reply With Quote
      06-05-2009, 02:35 PM   #27
Finnegan
Major General
 
Finnegan's Avatar
 
Drives: Sapphire Black/Black Z4Mc
Join Date: Oct 2008
Location: At the track..or wishing I were at the track

Posts: 6,439
iTrader: (17)

Quote:
Originally Posted by CanM3 View Post
Dont get me wrong, and I dont mean to sound like a di*k....but your explanation is wrong.....
A cars compression ratio is fixed, its determined by swept volume, piston configuration, cylinder deck height......
What you are talking about is volumetric efficiency, that is to say how well that fixed volume is used.
At higher altitudes, the air is 'thinner' there is less o2 available, so the VE is decreased. The use of forced induction packs the cylinder, increasing the VE....this will increase the cylinder pressures, but trust me, the compression ratio is a fixed ratio, it does not change...but cylinder pressures change constantly....
The only advantage a turbo has over a Supercharger is the turbo is utilizing a waste stream (the exhaust) to charge the cylinders...it uses a little mini gas turbine, same principle as a steam turbine, just on a much smaller scale. The turbo 'works' as hard at sea level as it does at high altitude, the thing that changes is the waste gate position, less boost required, more air is bled off thru the waste gate.
I much prefer supercharging to turbocharging....there is a bit of a tradeoff as there is a bit of a parasitic element to supercharging, but they are so much more reliable. Turbo's run at extremely high temps, require zoomy metallurgy, require an extensive oiling system, very sensitive to downstream pressure changes, then the infamous turbo lag, not present in supercharging.
At full throttle, a supercharger and a turbo charger would both put out max rated boost......as mentioned before this would be dependant upon waste gate or bleed valve settings.
So, dont mix up compression ratio and cylinder pressures, they are two totally different things.......
No worries--this is a better explanation and it uses the right terms (volumetric efficiency). And yep, that's what I meant by "compression effectively drops" (probably conceptually sort of okay) but the language was sloppy. Not so much confusion as imprecision and sloppiness. Fair enough and perfectly okay to jump in and make corrections and this moves us all in the right direction (precision, less ambiguity).

Back to the OPís issue, do you concur that at altitude a tune isnít going to offer much improvement (or as much as at sea level) with a N/A engine, and if so, is FI probably the best (although not cheap) option to compensate for altitude related performance issues? What about the question of 100 octane seeming to cause worse performance than 91 octane in this application?

Now, as to which is better, S/C or Turbo....I'm not going there! That's DCT vs. 6MT territory or worse!

I do have a couple more questions on the S/C and turbo stuff though (Iím not trying to sound like a d*ck here either, just trying to fill in some areas where I'm not certain and learn something):
Does a S/C adjust, via ECU or other mechanism, to keep boost at a target PSI based to some degree on intake air temp, engine temp, fuel quality, throttle position, detonation detection, and altitudeóand does that target change if some parameters would make a ďnormalĒ boost target unsafe under some conditions?

Doesn't a modern (say 335i) turbo setup use the ECU to monitor and adjust the wastegates to achieve PSI boost targets (which can vary) to hit target based on intake air temp, engine temp, fuel quality, throttle position, and altitude, and doesn't it dial back boost if itís unsafe for the engine?
I'm guessing both aren't perfect remedies for high-altitude as the air is thinner (guessing more turbo lag--slower spin up--no sure about the S/C) and it would seem you'd have to spin the turbo faster to achieve the same boost (same with S/C?) since the air is less dense (and there's a point where you'd spin the little guys into pieces).

Given the preference for S/C I take it you're not thrilled with the idea of the next generation of M3 probably being a turbo-based FI approach....
Finnegan is offline   United_States
0
Reply With Quote
      06-05-2009, 02:39 PM   #28
J08M3
Major General
 
J08M3's Avatar
 
Drives: 2011 M3 COUPE
Join Date: May 2008
Location: NEW YORK

Posts: 6,012
iTrader: (8)

CanM3 - good catch on volumetric efficiency not CR
__________________
J08M3 is offline   United_States
0
Reply With Quote
      06-05-2009, 05:58 PM   #29
Radiation Joe
Veni Vidi Vici
 
Radiation Joe's Avatar
 
Drives: '11 JB/BBe-6sp-e90
Join Date: Jul 2008
Location: Macungie PA

Posts: 2,749
iTrader: (0)

Garage List
2011 e90 M3-Sold  [4.25]
2003 RS6 - Sold  [0.00]
2009 e90 M3 - Gone  [0.00]
2003 M3 SOLD  [0.00]
old 2002  [5.00]
Quote:
Originally Posted by J08M3 View Post
CanM3 - good catch on volumetric efficiency not CR
Not a good catch. Volumetric efficiency is unaffected by altitude. Cylinder pressure is what decreases, since the initial pressure (outside the engine) is lower and the compression ratio and volumetric efficiency are unchanged. The same volume (approximately) is pumped, but that volume has less mass than at sea level. Hence, the cylinder pressures are lower. Just thought I'd be a d!ck and point that out.
Radiation Joe is offline   United_States
0
Reply With Quote
      06-05-2009, 07:12 PM   #30
elp_jc
Brigadier General
 
Drives: .
Join Date: May 2008
Location: .

Posts: 4,910
iTrader: (0)

Compression ratio will always be a FIXED number. It's simply a volume ratio between BDC and TDC. You're probably referring to 'effective compression ratio', which is another term to describe the same phenomenon: less volumetric efficiency, and less cylinder pressure at altitude, due to decreased oxygen levels.
elp_jc is offline   United_States
0
Reply With Quote
      06-05-2009, 08:31 PM   #31
CanM3
Private
 
CanM3's Avatar
 
Drives: 2008 JB M3
Join Date: May 2009
Location: Calgary, Canada

Posts: 82
iTrader: (0)

haha, this is a like theory class.......the amount of air an engine can injest is directly proportional to 2 variables, that being mass of air and volumetric efficiency...

The questions about a turbo.....the ECU does control a turbo's output by bleeding gas around the turbo....I think I said air last time, that was wrong..So you are absolutely right, the ecu looks at the parameters and adjusts boost accordingly
CanM3 is offline  
0
Reply With Quote
      06-05-2009, 09:05 PM   #32
Finnegan
Major General
 
Finnegan's Avatar
 
Drives: Sapphire Black/Black Z4Mc
Join Date: Oct 2008
Location: At the track..or wishing I were at the track

Posts: 6,439
iTrader: (17)

Yep. You can certainly learn a lot around here--good stuff! I've gained something just on this thread.

I seem to recall some debate that ran into the merits of equation a vs. equation b using calculus....you never know how far the technical precision of some of these discussions will go!

It also reminds me to be careful about pontificating on technical items where I might be a bit fuzzy. There's always someone who either knows more or who can explain it more clearly (in many cases both)...which is fine with me. It would suck if bad information were let stand or if you couldn't leave a bit more educated than when you showed up here.
Finnegan is offline   United_States
0
Reply With Quote
      06-14-2009, 07:03 PM   #33
dcstep
Brigadier General
 
Drives: '09 Cpe Silverstone FR 6MT
Join Date: Nov 2008
Location: Colorado

Posts: 4,927
iTrader: (0)

Garage List
2009 M3  [4.00]
When I uploaded the dyno graphs comparing my runs with Dinan thottle bodies, Active Autowerke exhaust and Dinan chip, I had "Smoothing" set at "5" rather than "0" for the most accurate result. The difference didn't change much and the peak hp went up only 1hp. Still, in the interest of accuracy I'm posting the corrected graphs below:
Attached Images
 
__________________
dcstep is offline   United_States
0
Reply With Quote
      06-14-2009, 08:07 PM   #34
dcstep
Brigadier General
 
Drives: '09 Cpe Silverstone FR 6MT
Join Date: Nov 2008
Location: Colorado

Posts: 4,927
iTrader: (0)

Garage List
2009 M3  [4.00]
I reread the thread when I posted the correction in the prior graph and noticed that I promised to post comparisons of 91-octane. I posted comparing the car with Dinan chip, Dinan throttle bodies and Active Autowerke Signature exhaust with 100-octane gas to the stock car with only 91-octane. I was demonstrating that I'd gained 200 rpm in redline.

Also, there was an interim step where I'd installed the throttle bodies and AA exhaust, but didn't have the chip yet, so the graph below has three results, all with 91-octane:
  • Stock -- Blue -- 333 hp 246 ft lbs
  • Exhaust/TB -- 337 hp 247 ft lbs
  • Exhaust/TB/Chip -- 334 hp 244 ft lbs

Sad indeed!!!

Somebody needs to post some Dinan chip results at sea level. I LOST 3 hp and 3 ft lbs. Dinan will pooh pooh my dyno's reliability, but I really don't think that's the issue. I've done 24 or so runs now on this dyno with consistent looking curves. Much of it probably has to do with altitude and failure of ALL the ECU tuners to address the impact of that. (Since all I've found so far are at see level, I guess it's understandable). Looking at my AFR, my dyno tuner is salivating to dyno tune my car, BUT he doesn't have access to software for BMWs and Mercedes. (He thinks I'm missing 15 hp or so that he could extract with the right software).

I couldn't find a Dinan chip on PencilGeek's dyno database, so somebody needs to step up and validate their 6 hp claim.

So, that's where we are...

Dave
Attached Images
 
__________________
dcstep is offline   United_States
0
Reply With Quote
      06-14-2009, 09:26 PM   #35
jeff4598
Lieutenant
 
Drives: 2009 e90 AW/BB lotsa Dinan
Join Date: Jan 2009
Location: new jersey

Posts: 447
iTrader: (0)

O2 not air

Nice discussion about how much AIR the engine gets at altitude but engines don't burn fuel with air they use O2-I think it's all about the lower concentration of O2 in the same amount of air that produces less power at altitude.Alot like people but cars cant make or use extra red blood cells
jeff4598 is offline  
0
Reply With Quote
      06-14-2009, 10:55 PM   #36
dcstep
Brigadier General
 
Drives: '09 Cpe Silverstone FR 6MT
Join Date: Nov 2008
Location: Colorado

Posts: 4,927
iTrader: (0)

Garage List
2009 M3  [4.00]
Quote:
Originally Posted by jeff4598 View Post
Nice discussion about how much AIR the engine gets at altitude but engines don't burn fuel with air they use O2-I think it's all about the lower concentration of O2 in the same amount of air that produces less power at altitude.Alot like people but cars cant make or use extra red blood cells
Air density is one very important factor in arriving at oxygen content of the intake charge. At 5400 ft above sea level, every component of air is reduced per cubic meter of volume, not just oxygen.

It's useful to talk about air and fuel because the oxygen can come from two sources, the air and the fuel. This is one reason I'm going to try the E85 mix (much higher oxygen content than 100% petroleum-based gasoline), because there's oxygen in E85 fuel to make up for the lower oxygen content in the intake air. Without FI and/or the ability to change the AFR (notice they say "air" fuel ratio because the oxygen content is outside the control of the ECU, it can only change volumes not content) I can only work with the fuel side of the mixture.

Anyway, the use of the term "air" is intentional. It's the component we're controlling. The objective is indeed to get oxygen into the engine, but we accomplish that by working with the both the air and fuel.

Dave
__________________
dcstep is offline   United_States
0
Reply With Quote
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 05:29 AM.




m3post
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST