Question on air consumption

[urBan_dK]

Originally Posted by CanAutM3

Agreed that RAM air will improve volumetric efficiency, but never back to 100%. At 270km/h, the dynamic pressure is about 3.4kPa (0.5psi), which is about a 3.4% pressure increase (standard atmosphere is 101.3kPa), not enough to bring back VE to 100% IMO.

The M3 intake however does not benefit from the full RAM effect due to the opening on the hood. I think RAM effect on the M3 is mostly used to avoid heat soak in the intake tract.

I tend to agree that the intake design doesn't allow for the RAM effect. However, I think an estimate of 80% VE peak is low. We should be approaching 100% for this highly tuned motor. If we had a MAF reading the intake volume of air would be trivial with some data logging.

[BMRLVR]

Here is the math to figure out airflow at a given RPM

REQUIRED AIRFLOW (scfm) = 2.723 x HP x BSFC

This math will allow you to figure out 100% VE airflow of an engine.

100% VE AIRFLOW (scfm) = DISPLACEMENT (ci) x RPM / 3456

[CanAutM3]

Originally Posted by urBan_dK

I tend to agree that the intake design doesn't allow for the RAM effect. However, I think an estimate of 80% VE peak is low. We should be approaching 100% for this highly tuned motor. If we had a MAF reading the intake volume of air would be trivial with some data logging.

I could see volumetric efficiency getting closer to 100% at peak torque RPM.

But at max RPM, not so sure

I am not an expert, just going on gut feel...

[CanAutM3]

Originally Posted by BMRLVR

Here is the math to figure out airflow at a given RPM

REQUIRED AIRFLOW (scfm) = 2.723 x HP x BSFC

This math will allow you to figure out 100% VE airflow of an engine.

100% VE AIRFLOW (scfm) = DISPLACEMENT (ci) x RPM / 3456

All we need now is the BSFC at 8400RPM WOT for the S65

[///M Power-Belgium]

Originally Posted by CanAutM3

That number sounds optimistic as it implies a volumetric efficiency close or higher than 100%.

Can you link the source?

The ///M test that i have read last year...i can not find it again .
But on this 2 pages you can read it also...but you will need Google translate or look the number 17,000 liter per minuut !!!
http://www.badchix.com/modules/fun/a...=rating&rate=5
http://www.autozine.nl/text/558.html

[M3PO]

Originally Posted by CanAutM3

If we stay with the 80% volumetric efficiency assumption and figure that the engine runs about 15% rich at WOT, that would equate to about 1.7 liters of fuel per minute at 8400RPM WOT.

Note: these are only approximations to provide a ballpark figure .

I calculated 0.97 lpm from my experience on the track so that makes sense.

Originally Posted by CanAutM3

Agreed that RAM air will improve volumetric efficiency, but never back to 100%. At 270km/h, the dynamic pressure is about 3.4kPa (0.5psi), which is about a 3.4% pressure increase (standard atmosphere is 101.3kPa), not enough to bring back VE to 100% IMO.

The M3 intake however does not benefit from the full RAM effect due to the opening on the hood. I think RAM effect on the M3 is mostly used to avoid heat soak in the intake tract.

+1

[bruce.augenstein@comcast.]

Originally Posted by urBan_dK

I tend to agree that the intake design doesn't allow for the RAM effect. However, I think an estimate of 80% VE peak is low. We should be approaching 100% for this highly tuned motor. If we had a MAF reading the intake volume of air would be trivial with some data logging.

Coupla things -

As far as ram air goes, I remember an article from a number of years back wherein the designers/runners of a Bonneville streamliner were queried in regard to the NASA ducts they used for intake. At the time, the NASA design was considered to be the most efficient intake (probably still is), and these guys said they basically got back to ambient air pressure after subtracting surface friction on the way to the engine inlet.

In other words, although ram air is somewhat effective, it isn't a big deal, as already stated in this string.

As far as volumetric efficiency goes, it's rare for a street engine to reach that goal when you consider air filters, intake tubing, exhaust tubing and mufflers. Still, it's possible, but I would say that in order to reach that goal, you're going to have to stack the deck in regard to intake and exhaust tuning that matches the specific rpm where the torque curve naturally peaks anyway. In that case, you have a shot.

But the S65 is the antithesis of this type of tuning. You have the intake tuned for high rpm, and the exhaust tuned for much lower rpm. This gives the engine its signature flat torque curve, but doesn't offer the torque bulge that might signify 100% VE.

In my experience something around 80% VE might be available at the power peak, but probably no more.

Probably a bit more than 80% at peak torque, but not a lot more, because I am pretty much convinced that the torque peak on this engine is "artificially" low, dictated by those long exhaust runners.

Bruce

[Denk]

I'm surprised that the M3 doesn't have an Air Guzzler tax.

[M3takesNYC]

where are you throwing around these 80 percent numbers? There is no reason this engine is not easily performing at 90 percent plus VE from peak torque and dissipating a bit by redline. Not sure where you just pluck out 80 percent from

Originally Posted by bruce.augenstein@comcast.

Coupla things -

As far as ram air goes, I remember an article from a number of years back wherein the designers/runners of a Bonneville streamliner were queried in regard to the NASA ducts they used for intake. At the time, the NASA design was considered to be the most efficient intake (probably still is), and these guys said they basically got back to ambient air pressure after subtracting surface friction on the way to the engine inlet.

In other words, although ram air is somewhat effective, it isn't a big deal, as already stated in this string.

As far as volumetric efficiency goes, it's rare for a street engine to reach that goal when you consider air filters, intake tubing, exhaust tubing and mufflers. Still, it's possible, but I would say that in order to reach that goal, you're going to have to stack the deck in regard to intake and exhaust tuning that matches the specific rpm where the torque curve naturally peaks anyway. In that case, you have a shot.

But the S65 is the antithesis of this type of tuning. You have the intake tuned for high rpm, and the exahaust tuned for much lower rpm. This gives the engine its signature flat torque curve, but doesn't offer the torque bulge that might signify 100% VE.

In my experience something around 80% VE might be available at the power peak, but probably no more.

Probably a bit more than 80% at peak torque, but not a lot more, because I am pretty much convinced that the torque peak on this engine is "artificially" low, dictated by those long exhaust runners.

Bruce

[CanAutM3]

Originally Posted by bruce.augenstein@comcast.

Coupla things -

As far as ram air goes, I remember an article from a number of years back wherein the designers/runners of a Bonneville streamliner were queried in regard to the NASA ducts they used for intake. At the time, the NASA design was considered to be the most efficient intake (probably still is), and these guys said they basically got back to ambient air pressure after subtracting surface friction on the way to the engine inlet.

In other words, although ram air is somewhat effective, it isn't a big deal, as already stated in this string.

As far as volumetric efficiency goes, it's rare for a street engine to reach that goal when you consider air filters, intake tubing, exhaust tubing and mufflers. Still, it's possible, but I would say that in order to reach that goal, you're going to have to stack the deck in regard to intake and exhaust tuning that matches the specific rpm where the torque curve naturally peaks anyway. In that case, you have a shot.

But the S65 is the antithesis of this type of tuning. You have the intake tuned for high rpm, and the exahaust tuned for much lower rpm. This gives the engine its signature flat torque curve, but doesn't offer the torque bulge that might signify 100% VE.

In my experience something around 80% VE might be available at the power peak, but probably no more.

Probably a bit more than 80% at peak torque, but not a lot more, because I am pretty much convinced that the torque peak on this engine is "artificially" low, dictated by those long exhaust runners.

Bruce

^ This is also what my instincts are telling me.

I think that the volumetric efficiency ratio between peak torque and peak power should be in the neighborhood of 88%, essentially the torque ratio between these two engine speeds. You would also need to consider the increased friction losses in the higher RPM of the power peak, but it does provide a ballpark figure.

So if we assume 80% VE at power peak, this would mean around 91% at torque peak. Not unreasonable.

[bruce.augenstein@comcast.]

Originally Posted by M3takesNYC

where are you throwing around these 80 percent numbers? There is no reason this engine is not easily performing at 90 percent plus VE from peak torque and dissipating a bit by redline. Not sure where you just pluck out 80 percent from

You could be right here, although I am a little skeptical, given the slightly low torque figure.

As far as 80 percent goes, I have this figure in mind from reading bunches of SAE articles back around 20 years ago while helping to develop a quarter mile (and more) software package.

I concede that things have advanced since then, but so have laws governing drive-by noise standards.

Bruce

[bruce.augenstein@comcast.]

Originally Posted by CanAutM3

^ This is also what my instincts are telling me.

I think that the volumetric efficiency ratio between peak torque and peak power should be in the neighborhood of 88%, essentially the torque ratio between these two engine speeds. You would also need to consider the increased friction losses in the higher RPM of the power peak, but it does provide a ballpark figure.

So if we assume 80% VE at power peak, this would mean around 91% at torque peak. Not unreasonable.

Could be, but as just mentioned I am slightly skeptical because I feel the torque peak is unnaturally low, rpm-wise, and a teensy bit anemic.

Bruce

[kwike92]

lets not study the roots, and lets pick the fruits

[1MOREMOD]

Originally Posted by kwike92

lets not study the roots, and lets pick the fruits

Nice.

[CanAutM3]

Originally Posted by kwike92

lets not study the roots, and lets pick the fruits

Nice and poetic.

As with great wines, the roots and the soil are the source to great fruits

It is a personal thing, but I like to understand where the fruits come from

[kwike92]

Originally Posted by 1MOREMOD

Nice.

Originally Posted by CanAutM3

Nice and poetic.

As with great wines, the roots and the soil are the source to great fruits

It is personal thing, but I like to understand where the fruits come from

you guys like this one huh? hahaha


no but seriously... lets eat the fruits now...

[M3takesNYC]

How would this compare to the AMG motor? The 6.3l NA motor in the c63? In terms of air consumption?

So is it the high rpms that really require all of that air?

I just still am amazed and I still pop my hood and stare at the S65 engine. I am such a nerd but something is just so perfect about the engine. It is not the most powerful but for 4 litres not much else touches it for hp/litre. 104hp/L is still absolutely amazing and it just is a perfect piece of machinery to me. 8600 redline, ITB, 12:1 compression and just screams.

Is it just me or does anyone actually kind of secretly like the fact it is so bad on gas? Makes it seem that much more performance focused!

[bruce.augenstein@comcast.]

Originally Posted by M3takesNYC

How would this compare to the AMG motor? The 6.3l NA motor in the c63? In terms of air consumption?

So is it the high rpms that really require all of that air?...

Thinking of an engine as a simple air pump, it's engine capacity times 1/2 rpm that determines how much air is needed (at 100% VE). In this case, the 6.2 liter's cubic capacity "advantage" is partially offset by the fact that it doesn't rev as high. Still, it needs about one third more air than the S65 at max revs (7200 in the case of the Merc).

All this assuming equal volumetric efficiency at redline between the two engines.

Bruce

PS - All this talk about how much air is needed got me to thinking about an old car ad I remembered from Pontiac, back in 1964. I had a GTO at the time and have to say it's clearly just a picture of an empty garage and hyperbole - but magnificent hyperbole.

It's here. Scroll up just a bit and enjoy this ad from Popular Science.

[BMRLVR]

Originally Posted by bruce.augenstein@comcast.

Thinking of an engine as a simple air pump, it's engine capacity times 1/2 rpm that determines how much air is needed (at 100% VE). In this case, the 6.2 liter's cubic capacity "advantage" is partially offset by the fact that it doesn't rev as high. Still, it needs about one third more air than the S65 at max revs (7200 in the case of the Merc).

All this assuming equal volumetric efficiency at redline between the two engines.

Bruce

PS - All this talk about how much air is needed got me to thinking about an old car ad I remembered from Pontiac, back in 1964. I had a GTO at the time and have to say it's clearly just a picture of an empty garage and hyperbole - but magnificent hyperbole.

It's here. Scroll up just a bit and enjoy this ad from Popular Science.

The M156 has nearly identical Lb/Ft per litre to the S65 so it may be roughlythe same VE at redline. A quick look at a dyno chart to see what the curve does as it approaches redline.

Here is torque density of a few common NA engines that I cobbled together:
Dodge viper (8.4 liter): 66.6 Lb/Ft / liter
C6 ZO6: 67.15 Lb/Ft / Liter
C63 AMG: 73.6 Lb/Ft / Liter
E90/92/93 M3: 73.75 Lb/Ft Liter
Lexus IS-F: 74.2 Lb/Ft / Liter
Audi RS4/5/R8: 76.5 Lb/Ft / Liter
E46 M3: 80.8 Lb/Ft / Liter
E46 M3 CSL: 84.1 Lb/Ft / Liter

[M3takesNYC]

Wow, when you compare it to other really potent big torque NA motors, the m3s actually have some of the highest torque per litre! Also hp per litre. Really shows you the engineering that went into these engines vs. these other engines are great but they are quite large and power is quite easy to make with a large engine. I love this engine!

[bruce.augenstein@comcast.]

Originally Posted by BMRLVR

The M156 has nearly identical Lb/Ft per litre to the S65 so it may be roughlythe same VE at redline. A quick look at a dyno chart to see what the curve does as it approaches redline.

Here is torque density of a few common NA engines that I cobbled together:
Dodge viper (8.4 liter): 66.6 Lb/Ft / liter
C6 ZO6: 67.15 Lb/Ft / Liter
C63 AMG: 73.6 Lb/Ft / Liter
E90/92/93 M3: 73.75 Lb/Ft Liter
Lexus IS-F: 74.2 Lb/Ft / Liter
Audi RS4/5/R8: 76.5 Lb/Ft / Liter
E46 M3: 80.8 Lb/Ft / Liter
E46 M3 CSL: 84.1 Lb/Ft / Liter

Add the E60 M5 engine at 76.8 lb/ft per liter

[bruce.augenstein@comcast.]

Originally Posted by M3takesNYC

Wow, when you compare it to other really potent big torque NA motors, the m3s actually have some of the highest torque per litre! Also hp per litre. Really shows you the engineering that went into these engines vs. these other engines are great but they are quite large and power is quite easy to make with a large engine. I love this engine!

Power and torque per liter is definitely harder to come by in a big engine than in a smaller one.

Not to put down the S65. It deserves all its awards.

Bruce