Just got the Dinan ECU tune on Stock M3

[dcstep]

Originally Posted by gemini330zhp

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

[Finnegan]

Originally Posted by dcstep

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.

[J08M3]

good explanation

[CanM3]

Originally Posted by Finnegan

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.......

[Finnegan]

Originally Posted by CanM3

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 OP’s issue, do you concur that at altitude a tune isn’t 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 (I’m 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 altitude—and does that target change if some parameters would make a “normal” 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 it’s 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....

[J08M3]

CanM3 - good catch on volumetric efficiency not CR

[Radiation Joe]

Originally Posted by J08M3

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.

[JCtx]

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.

[CanM3]

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

[Finnegan]

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.

[dcstep]

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:

[dcstep]

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

[jeff4598]

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

[dcstep]

Originally Posted by jeff4598

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