What is the M3's biggest weakness?

[Envyscorpio]

Originally Posted by wooderson

I'm gonna go out on a limb here and speak for the lack of torque crew in this thread and say that the lack of torque we are refering to is NOT in reference to passing a mini van on the highway.

OK fine... in that case my M needs more torque too. That is why I kept the 520. Whenever I feel the M3 needs more power I just hop into the 520 for a couple days.

[swartzentruber]

I think the tuning of the D modes for the DCT could have been a lot better, as it downshifts too slowly, and upshifts into 7th far too quickly. I've tried some of the higher D modes, and it seems they mostly just want to hold the gear longer before shifting, but don't solve my other issues. I find it ludicrous that the gas savings for EPA rating could have been that signficant to make it worth programming the DCT to shift into 7th at 40, and I can't imagine it's good for the engine. Personally, I only notice the "lack of torque" issue that so many complain about when running in the D modes. Shifting manually, shifting more like what a typical 6MT driver would do, it always feels like it has plenty of power.

[sin911]

There are a few weak points of the car: weight, low end torque (below 3,500 rpms) and brakes.

I don't go to the track anymore so none of these really affect me. But as my past experience hast taught me weight is the biggest enemy. If the weight of the car was leas the power to weight ratio would increase and even though the torque figure would be the same the car would automatically accelerate faster, therefore our problem would be solved.

The brake issue is being resolved with the next M3/4 but I wish they would have fixed it with this generation. Oh well...

[Richbot]

It cares too much

[Sapper_M3]

Originally Posted by Richbot

It cares too much

[klammer]

Originally Posted by Richbot

It cares too much

No shit! Perfections an illusion!

[MartyM]

The driver

[OC3]

Originally Posted by MartyM

The driver

Damn, you beat me to it.

[BMRLVR]

Originally Posted by bruce.augenstein@comcast.

Since we're talking about what happens out here on the actual planet, the fact of the matter is that in actuality, what happens when you lengthen the stroke is that you reduce the rod-length-over-stroke ratio - unless you want to put aircraft warning lights on the deck height. Sure, you can raise the piston pin, or even go with offset pins, but those practices bring their own problems.

OK, reducing the rod length/stroke ratio is a mixed blessing. First (and as you've said), you pull the piston off top dead center more quickly, giving a stronger early signal to the intake, thus leading to better cylinder filling at low rpm. In addition, you mechanically take better advantage of the short-lived cylinder pressure spike, because due to increased rod angularity, you reach max energy conversion into torque by enabling a 90 degree angle between the rod and a line drawn from the crank throw to the crank centerline earlier in the powerstroke. Presto! More torque.

As revs rise, however, and the engine moves toward max VE (and above), rod angularity starts to hurt you, because you are generating more friction due to increased side loads on the piston. In addition, those low-rpm benefits erode, because you begin to take advantage of the intake and exhaust resonances along with more optimum cam timing. At high rpm, "short" rods (in relation to stroke) just hurt you powerwise, eating up those low-rpm torque babies, and more.

Agree on all of this but rod to stroke ratio has much less effect than some people will have you believe. 9/10 engine builders will tell you that they pay little attention to R/S ratios in the grand scheme of things. Basically they are going to build an engine and pick a stroke, bore, heads......... And way down the list they may look at the R/S ratio to check if it is close to where they would like it to be while keeping the piston pin in a good position. This desired R/S ratio is generally 1.5 or greater depending on the max RPM of the engine.

Originally Posted by bruce.augenstein@comcast.

At a guess, 99 out of 100 M3 owners would be pleased by having peak torque upped by 11% while leaving peak power alone. Not theoretically pleased, but from behind the wheel.

They may be pissed if it was necessary to sacrifice the overall torque curve to obtain this 11% increase you speak of. It isn't all as easy as you make it sound. Another thing that you also have to consider is they made the S65 ULEV compliant and emissions sometimes are negatively affected by what makes the most torque per litre. Lots of things are taken into consideration by manufacturers when building a production engine...... Not just peak torque and horsepower output.

Originally Posted by bruce.augenstein@comcast.

Again, completely disagree.

Have you checked out the exhaust headers on the S65? They are not only works of art, but IMO they are the primary reason why the torque peak is at an artificially low 3900 rpm on this engine. Those long runners are optimum for low-rpm exhaust tuning, while the rest of the engine seems to be designed for high-rpm greatness. If they tuned those runners for a higher-rpm resonance, you'd need even less underhood space, while gaining torque because the exhaust tuning benefits occur at a more "natural" rpm, dictated by the rest of the design.

I certainly have checked out the S65 headers and I do agree with you on the fact that they are works of art but they are definitely not the reason why the engine has it's torque peak at 3900 RPM.

The headers have proven that they flow extremely well at outputs that are much higher than OEM, for example stroker motors and SC'ed cars are running these and aftermarket headers have showed no substantial change in the output of the engine. That would lead me to believe that they are not tuned for strictly low RPM torque since that would be compromising the high RPM performance of the engine........ Besides, they are not even a long tube design, they are a short-medium length header that is equal length. Look at the primaries from cylinder 1 and 5, they are not overly long, all of the other bends in 2,3,4 and 6,7,8 are just there to make all of them equal length. Compare them to many other long tube headers on the market and you will see what I mean.

Originally Posted by bruce.augenstein@comcast.

Again, we're talking about torque per liter, not power, and I began some of this back-and-forth by stating that if BMW had only matched the S54 torque-per-liter output, they'd have an even better engine, making for an even finer eye-popping drive.

Be honest, now. Are you insisting that raising the torque by 11% on this engine while keeping the same peak power at 8300 would somehow make for a less capable and exciting offering?

Bruce

I am sure if BMW could have matched the torque per litre without compromising the rest of the design they definitely would have. As I have mentioned above there are many things to consider when designing a production engine so have faith that they brought everything to the table with this one that they thought they could. Yes they probably could have made more torque per litre but I think that they didn't do this as a result of many other factors that are beyond us.

[bruce.augenstein@comcast.]

Originally Posted by BMRLVR

...I certainly have checked out the S65 headers and I do agree with you on the fact that they are works of art but they are definitely not the reason why the engine has it's torque peak at 3900 RPM.

The headers have proven that they flow extremely well at outputs that are much higher than OEM, for example stroker motors and SC'ed cars are running these and aftermarket headers have showed no substantial change in the output of the engine. That would lead me to believe that they are not tuned for strictly low RPM torque since that would be compromising the high RPM performance of the engine........ Besides, they are not even a long tube design, they are a short-medium length header that is equal length. Look at the primaries from cylinder 1 and 5, they are not overly long, all of the other bends in 2,3,4 and 6,7,8 are just there to make all of them equal length. Compare them to many other long tube headers on the market and you will see what I mean.

I certainly agree that the runners are not overly long - they're just as long as they need to be to enhance torque in the high 3000s - low 4000s area.

They are in fact a ton longer than the intake runners, which are designed to provide high rpm cylinder filling.

Look, I'm not talking about flow capacity. I'm talking about the natural resonance of these individual pipes. You know. The time necessary for the exhaust pulse (pressure wave) to reach the collector, and the inevitable vacuum wave that travels back up the pipe to the cylinder head. If that vacuum wave hits the exhaust valve as it is just opening, the pressure wave out of the exhaust port/valve begins to empty into a partial vacuum, thus making for a more efficient flow.

The pipe length combined with the speed of sound constant dictates the engine speed at which this resonance is most effective.

Same thing on the intake, except in reverse.

My position is that the relatively long exhaust runners build torque at and around 3900 rpm, while the much shorter intake runners build torque at high rpm. These two factors are one of the keys to a long, flat torque curve.

Originally Posted by BMRLVR

I am sure if BMW could have matched the torque per litre without compromising the rest of the design they definitely would have. As I have mentioned above there are many things to consider when designing a production engine so have faith that they brought everything to the table with this one that they thought they could. Yes they probably could have made more torque per litre but I think that they didn't do this as a result of many other factors that are beyond us.

Agree on everything.

Originally Posted by BMRLVR

Definitely........ The torque curve of the S85 is much peakier than the S65, serves to show that in order to flatten the the torque curve of the S65 they compromised on specific torque output.

Yes. And my position is that enhanced flow at 3900 rpm makes for more torque there, but that the rest of the engine would tend to have a more "natural" torque peak a fair bit higher in the range, so if you had a shorter exhaust runner length, you'd enhance torque in an area where the engine naturally wants to peak, thereby enhancing the torque bump even more.

Oh. Was that a run-on sentence? Sorry.

Bruce

[CanAutM3]

Originally Posted by bruce.augenstein@comcast.

PS - For other interested parties, the reason a longer stroke doesn't add torque while maintaining the same displacement is that even though you have a longer moment arm to deliver force to the crank, this is offset by having a narrower piston, meaning you have fewer square inches for combustion pressure to push against, reducing total force. Bore and stroke make for a net sum game in this context as far as torque is concerned.

I was about to post this, but you beat me to it

Great "in between" discussion going on in this thread. Very informative.

[bradleyland]

Originally Posted by bruce.augenstein@comcast.

PS - For other interested parties, the reason a longer stroke doesn't add torque while maintaining the same displacement is that even though you have a longer moment arm to deliver force to the crank, this is offset by having a narrower piston, meaning you have fewer square inches for combustion pressure to push against, reducing total force. Bore and stroke make for a net sum game in this context as far as torque is concerned.

So glad to see this here. The belief that mechanical leverage is the source of greater torque in long-stroke engines is a hard one to kill. Here's a straight up formulaic approach for anyone interested in the maths:

http://ktmmad.com/2013/01/18/bore-an...epower-part-2/

[thedge9]

Originally Posted by lenzm3edan

Gas mileage, I-drive and that shitty 6spd shifter. Some complain about torque but I think it's a perfect balance for a high reving V8 that has a main purpose for track.

Gas mileage, LOL

Originally Posted by M3RD

I too respectfully disagree with Vic311, the gear box on the m3 is nothing like it when I compare it to the smooth shifting of our still running strong e28 545is having 5 gears. Shifting the 535is is as smooth as it gets, nothing like the e92 m3 and I drove two MT m3's before I switched to the DCT. Something happen between BMW's MT between 1987 to 2011 - 2012.

Yes, I believe they switched from ZF -> Getrag

Originally Posted by ersin

Single biggest weakness: lack of oil dipstick.


Cheers.

+1

Originally Posted by sensi09

A 2000 LS400 has a 4.0L V8 with 300ft-lb of torque lol.

If you're talking about 4.0 and smaller, there's plenty of Porsche engines that come to mind with an equal amount of torque or more.

I'm sure there are plenty of truck engines that fit this bill as well.

The question that should be asked is, why not use a bigger V8

This is true, but these engines dont have the same redline or throttle response

Originally Posted by Nati Beastcat

^This

I want more torque! I don't get to drive my car around the track so I guess I'll never know the limits of my car according to some....... I have a Toyota highlander with 4wd and a speed odometer that reads to 140 mph. I Don't plan on driving it off the top of dune at 139 mph so i'll probably never know its limits either. Traffic light to traffic light I want torque! AMG type torque! I want to roast my tires off if I feel like it with little effort.

is that so bad?

Its not bad, its just not an M3, just ask J. Clarkson. And he loves the AMG C63

Originally Posted by Transfer

Well I guess everyone is going FI with the next M. Better get rid of that NA E9x M3. What a downer of an engine!




Have fun with your turbo'd torque ya frickin weirdos.

Love it

Originally Posted by BMRLVR

You did not find me any engines that had considerably more torque than the M3 V8 at around 4.0 Litres. I was not talking about equal numbers, I was talking about wayyyy more...... There aren't any that is why....... The GT3 RS and RS 4.0 are two of the few engines that have considerably more torque in an equal displacement category. Otherwise the M3 makes good torque for it's displacement, not the torquiest but above average for sure when it comes to torque per litre.

The reason why the engine wasn't built for absolute maximum torque was that some compromise had to be made to port design and cam choice to achieve the broad torque curve that the engineers wanted out of this engine. This is illustrated by the fact that it has one of the flattest NA torque curves out there for a production engine!

Finally, the reason for not going with a larger displacement engine was that M wanted a high revving engine with the S65. As engine displacement increases the mass of internal components inevitably have to increase as do bearing journal diameters to deal with the extra forces generated by the added mass of components and higher forces that are a result of this. The problem is that heavy components do not want change direction as easily (When the pistons reach TDC and BDC and then reverse their direction) especially at higher engine speeds and larger journal diameters result in extremely high linear bearing speeds at the bearing surface. So in order to build an engine that turns 8K+ and has to last more than a few hundred miles smaller displacement is necessary, unless you start using exotic metals and extremely expensive components that aren't sensible for series production.

^What he said, enough about I need more torque, you need to buy an AMG and stop your whining

Originally Posted by robotk

Personally, I wouldn't want to (potentially) sacrifice this motor's rev characteristics for mid range grunt. Weight loss would achieve your goal, I think, and also improve handling and economy to boot.

The alternative would be a 458 type engine - 4.5 L with 9k redline, 12.5:1 compression ratio and peak torque at 3250. That's a very sweet engine, but it's exotic, expensive and a gas guzzler. For the price range, particularly, the s65 is an awesome powerplant.

We all know BMW will resort to turbos to get crowd pleasing low end power and efficiency. I'll miss NA, personally.

And that is probably why the S65 is one for the Ages

Originally Posted by JJunkins

This thread should be burned. Superman knows no kryptonite!

spoken like a true Fanboy, and I absolutley agree

[thedge9]

Now for my 2 cents

Weight...

But I understand the compromise of modern design and luxury requirements. If this car was built 10 years ago it could be a lot lighter, but alas it would not have the S65 which is a marvel of modern design. So I will take the current compromise.

[BMRLVR]

Originally Posted by bruce.augenstein@comcast.

I certainly agree that the runners are not overly long - they're just as long as they need to be to enhance torque in the high 3000s - low 4000s area.

They are in fact a ton longer than the intake runners, which are designed to provide high rpm cylinder filling.

Look, I'm not talking about flow capacity. I'm talking about the natural resonance of these individual pipes. You know. The time necessary for the exhaust pulse (pressure wave) to reach the collector, and the inevitable vacuum wave that travels back up the pipe to the cylinder head. If that vacuum wave hits the exhaust valve as it is just opening, the pressure wave out of the exhaust port/valve begins to empty into a partial vacuum, thus making for a more efficient flow.

The pipe length combined with the speed of sound constant dictates the engine speed at which this resonance is most effective.

Same thing on the intake, except in reverse.

My position is that the relatively long exhaust runners build torque at and around 3900 rpm, while the much shorter intake runners build torque at high rpm. These two factors are one of the keys to a long, flat torque curve.

I can't argue that it is possible that the engine has an exhaust header that is tuned to maximize scavenging at 3900, maybe they did tune it as such. A person would have to talk to an engineer to find out what the optimum RPM for the header as designed was (or some testing could show it).

One thing I need to clear up with you is that intake and exhaust tuning in the traditional sense on and engine with variable cam timing is not nearly as important as in an engine with fixed cam timing. I am very aware of the use of resonance tuning in intakes and of the use of scavenging to tune exhaust headers. With the S65 both duration and overlap are adjustable so essentially the intake and exhaust length is not nearly as important as in other engines with fixed cam timing. I am thinking that they tried many combinations of intake and exhaust lengths in testing and came up with the best compromise in the torque curve. Also worth mentioning is that not only primary length is important in header design but diameter is critical too....... Too large a diameter and low RPM torque will suffer, regardless of primary length.

The intake runners or header primaries were most likely picked based on the VANOS systems ability to vary cam timing, more importantly the rate. As RPM's rise in the engine and piston speeds increase obviously the rate of VANOS adjustability is going to remain static. I am thinking that the intake and exhaust manifolds are both designed for higher RPM since the VANOS system has less time to vary timing at the higher RPM. In the low to mid RPM range the VANOS system has adequate time to vary the timing to exactly where it needs to be to meet the optimum characteristics of the intake and exhaust runners to obtain near max VE at all times.

I may not be correct but I think that if the engineers designed the exhaust headers to work best at lower RPM the higher RPM of the engine would most likely suffer. If you look at the S54 for example, the header primaries are much longer than the S65 yet the torque peak is higher.

What do you think?

[bruce.augenstein@comcast.]

Originally Posted by BMRLVR

...One thing I need to clear up with you is that intake and exhaust tuning in the traditional sense on and engine with variable cam timing is not nearly as important as in an engine with fixed cam timing. I am very aware of the use of resonance tuning in intakes and of the use of scavenging to tune exhaust headers.

My position would be that variable cam timing can be used to widen the torque bump due to header tuning, so you can in effect make header tuning work over a wider rpm range.

Originally Posted by BMRLVR

With the S65 both duration and overlap are adjustable so essentially the intake and exhaust length is not nearly as important as in other engines with fixed cam timing. I am thinking that they tried many combinations of intake and exhaust lengths in testing and came up with the best compromise in the torque curve...

How does VANOS affect duration? This is new to me.

Originally Posted by BMRLVR

The intake runners or header primaries were most likely picked based on the VANOS systems ability to vary cam timing, more importantly the rate. As RPM's rise in the engine and piston speeds increase obviously the rate of VANOS adjustability is going to remain static. I am thinking that the intake and exhaust manifolds are both designed for higher RPM since the VANOS system has less time to vary timing at the higher RPM. In the low to mid RPM range the VANOS system has adequate time to vary the timing to exactly where it needs to be to meet the optimum characteristics of the intake and exhaust runners to obtain near max VE at all times.

Seriously? What would rpm have to do with VANOS' "need for speed" to alter cam phasing?

Originally Posted by BMRLVR

I may not be correct but I think that if the engineers designed the exhaust headers to work best at lower RPM the higher RPM of the engine would most likely suffer. If you look at the S54 for example, the header primaries are much longer than the S65 yet the torque peak is higher.

At some other rpm than the resonance range, you just lose the resonance. Second order resonance is miniscule.

My perusing of S54 exhaust manifolds shows shorter runners.

I've given you my thoughts on the discrepancy between intake and exhaust runner length on the S65, and why this is so. So give me your thoughts on why this is so. You think this is an accident?

Bruce

[CanAutM3]

Originally Posted by bruce.augenstein@comcast.

My position would be that variable cam timing can be used to widen the torque bump due to header tuning, so you can in effect make header tuning work over a wider rpm range.

How does VANOS affect duration? This is new to me.

I would have thought that exhaust and intake resonance RPM are independent of the camshaft timing... my understanding is that getting the benefits from resonance is mostly dependent of the runner length and how the exhaust valves (or intake valves) close and open relative to each other. The closing and opening of the valves is dictated by the physical design of the camshaft. The timing of the overall camshaft would not have an impact on when the individual valves close and open relative to each other. One could argue that varying the intake vs exhaust overlap could be done to optimize resonance, I would however tend to believe that overlap would mostly be tuned to optimize the flow for the given RPM rather than for resonance.

Now, if the duration would vary, the resonance could be leveraged over a broader RPM band. But I don't believe that Vanos has the ability to change the duration.

[Powerbeast]

Weight and MPG

[BMRLVR]

Originally Posted by bruce.augenstein@comcast.

My position would be that variable cam timing can be used to widen the torque bump due to header tuning, so you can in effect make header tuning work over a wider rpm range.



How does VANOS affect duration? This is new to me.

I am pretty sure The camshaft phasers in the VANOS system on the newer BMW engines have the ability to adjust the cam while it is on the ramp....... Since the cam is changing position while the valve is open it is affecting duration. This is one of the reasons why cams show relatively small gains on the S65 and S85

Originally Posted by bruce.augenstein@comcast.

Seriously? What would rpm have to do with VANOS' "need for speed" to alter cam phasing?

The VANOS phasers on the S65 have a rate of adjustment of 360 degrees per second. As RPM's climb higher there is less time to adjust the camshafts (since combustion events are happening at a higher rate) therefore you want to tune the intake and exhaust to work best near higher RPM. The reason for this is that you want the amount of cam adjustment required to open the valves at the proper time to meet the resonance wave to be minimal since there is less time to do so.

Originally Posted by bruce.augenstein@comcast.

At some other rpm than the resonance range, you just lose the resonance. Second order resonance is miniscule.

You don't lose the resonance, the valves just open at the wrong times for the resonance wave to have an effect. In an engine with VCT the intake and exhaust valve timing is varied so that the resonance wave is not used at a specific RPM but rather over a wide range of RPM's

Originally Posted by bruce.augenstein@comcast.

My perusing of S54 exhaust manifolds shows shorter runners.

Yeah they sure are shorter........ I was thinking of the primaries on the headers on the S50B30 euro engine like in my 94 Euro M3..... And even they are probably not longer but are close to the same length of the S65. Torque peak on that engine is 236 Lb/Ft at 3600 so not a good example to prove my point anyway.

Originally Posted by bruce.augenstein@comcast.

given you my thoughts on the discrepancy between intake and exhaust runner length on the S65, and why this is so. So give me your thoughts on why this is so. You think this is an accident?

No I am sure there is no accident in the runner length as I am very sure there was extensive R&D and engineering to obtain the final product.

Everything you say is correct and with a proper thought process. My only argument is that I don't think that the header design is the single thing that moves the torque peak lower on this engine. I feel that the intake and header design was a compromise to get a torque curve that stayed flat almost till redline with the help of a sophisticated variable cam timing system.

[CanAutM3]

Originally Posted by BMRLVR

I am pretty sure The camshaft phasers in the VANOS system on the newer BMW engines have the ability to adjust the cam while it is on the ramp....... Since the cam is changing position while the valve is open it is affecting duration. This is one of the reasons why cams show relatively small gains on the S65 and S85

Are you suggesting that the Vanos adjusts the timing of the camshaft multiple times (up to 8 times?) for every camshaft rotation? That would be 560 times per second at 8400RPM. If it is the case, that is be pretty darn amazing .

Originally Posted by BMRLVR

You don't lose the resonance, the valves just open at the wrong times for the resonance wave to have an effect. In an engine with VCT the intake and exhaust valve timing is varied so that the resonance wave is not used at a specific RPM but rather over a wide range of RPM's

If the Vanos has the ability to adjust timing multiple times per rotation, I see how this could be done. I am however a bit sceptical that the Vanos has the speed and precision to be able to do that...

[bruce.augenstein@comcast.]

OK, we're so far down in the weeds now that I am quite sure other readers think we're so anal that we had to've been potty trained at gunpoint.

Originally Posted by BMRLVR

I am pretty sure The camshaft phasers in the VANOS system on the newer BMW engines have the ability to adjust the cam while it is on the ramp....... Since the cam is changing position while the valve is open it is affecting duration. This is one of the reasons why cams show relatively small gains on the S65 and S85

Think about what you're saying here. Say the cam is advancing, so when that begins, the valve begins opening sooner - but it also closes sooner. Then for each revolution, the valve opens that teensy bit sooner, but also closes that teensy bit sooner - until cam advance stops while the valve is on the lobe. For that single revolution (and only when assuming the valve is riding the lobe at that point), duration fractionally changes.

This hardly counts as a change of duration.

Originally Posted by BMRLVR

The VANOS phasers on the S65 have a rate of adjustment of 360 degrees per second. As RPM's climb higher there is less time to adjust the camshafts (since combustion events are happening at a higher rate) therefore you want to tune the intake and exhaust to work best near higher RPM. The reason for this is that you want the amount of cam adjustment required to open the valves at the proper time to meet the resonance wave to be minimal since there is less time to do so.

In-gear rise of revs is so stupendously slow (compared to a cam phasing rate of 360 degrees per second) that the phasers could intermittently take a refreshing nap every so often while adjusting cam timing during an rpm-rush in first gear. In high gear, they could enjoy a good night's sleep before the need to move again. There is essentially no difference between low-rpm and high-rpm "need for speed" as far as cam phasing goes.

(Speaking of phasers, wouldn't it have been great if just once, Captain Kirk had said (when visiting a hostile planet) "Set phasers on extra crispy!"

But I digress.

Originally Posted by BMRLVR

You don't lose the resonance, the valves just open at the wrong times for the resonance wave to have an effect. In an engine with VCT the intake and exhaust valve timing is varied so that the resonance wave is not used at a specific RPM but rather over a wide range of RPM's

Yeah. Should've said you lose the resonance benefit, but othrwise we're saying the same thing - and that is that using intake and exhaust resonance in conjunction with VANOS can give you more effective resonance tuning - not less.

Originally Posted by BMRLVR

No I am sure there is no accident in the runner length as I am very sure there was extensive R&D and engineering to obtain the final product.

Everything you say is correct and with a proper thought process. My only argument is that I don't think that the header design is the single thing that moves the torque peak lower on this engine. I feel that the intake and header design was a compromise to get a torque curve that stayed flat almost till redline with the help of a sophisticated variable cam timing system.

Then we're in agreement.

Bruce

[BMRLVR]

Originally Posted by bruce.augenstein@comcast.

OK, we're so far down in the weeds now that I am quite sure other readers think we're so anal that we had to've been potty trained at gunpoint.



Think about what you're saying here. Say the cam is advancing, so when that begins, the valve begins opening sooner - but it also closes sooner. Then for each revolution, the valve opens that teensy bit sooner, but also closes that teensy bit sooner - until cam advance stops while the valve is on the lobe. For that single revolution (and only when assuming the valve is riding the lobe at that point), duration fractionally changes.

This hardly counts as a change in duration.

The phaser can advance or retard the cam while on the ramp of the lobe so that can change duration. It is actually very cool to watch camshaft angles via the cam position sensors on an engine with VCT. We had the opportunity to do this in one of my technical training courses in engine control systems!

Originally Posted by bruce.augenstein@comcast.

Then we're in agreement.

Bruce

For sure!

It is nice to have a conversation/debate with someone who is on the same page! I have thoroughly enjoyed this discussion so far!