Why is the E9X M3 so bad on gas?

[serranot]

Originally Posted by TVMA Doc

VTEC (Variable Valve Timing and Lift Electronic Control)...the name itself implies that it has ALWAYS had variable timing. Even the original VTEC (if I'm not mistaken, it was on the 1990 Integra) had variable timing.

It's variable, but only to the extent that the second cam lobes altered the timing. Technically, it worked as advertised; you basically had two different cam profiles because you had two sets of lobes on the cam.

The downside is that you either had one cam profile or the other; nothing in between. So, instead of having one cam that was a compromise across the engine's operating range, you had two compromises. Better than one, but not as good as, say, three, or four, or . . .

[thekurgan]

Originally Posted by aus

It's really not a big deal anymore now that people know about it. These were first generation motors that had this issues and there's an easy "fix" which is a catch can. The walnut cleaning can be done for around $350 (LTBMW) now too. A 15% increase in power and mileage would put the S65 at 475 HP and 19mpg overall (assuming 17mpg overall). Even without a catch can, I'd pay $300 every 50,000 miles for that engine. Even if it was a 10% improvement, I'd be very happy with it.

There was a pretty good article in Road & Track last month about this and the manufactures are now aware of this issue and designing engines to take this into consideration. It's also an area where GM/Ford see to be ahead of the Europeans in since they seem to not have this issues as much and in the article, a few engineers mentioned that they took this into consideration when designing DI engines.

.

I seriously doubt many know about this until they see a dealer, fork out some cash (post warranty) for plugs, coils and, eventually ... "ooooooh, I think I know what it is" says the tech.

Not me brother ...

1. I'd be thinking about the buildup so much that I'd want to have it done too often
2. If it's not something I can potentially DIY, I don't want it.


Anyone wanting the nextgen M3/M4 will have DI, so they can be plenty happy.

[aus]

Originally Posted by brisance

Is there any way for you to scan and post the relevant article online, maybe in a new thread? Don't want to go off-topic here and risk the wrath of the moderators, but I'm interested in this. Thanks.

I'm still looking for the issue. The wife cleaned out my magazines. I looked on the site but there were too many hits for "direct injection" search.

[thedge9]

Originally Posted by swamp2

Some decent replies here and some total crap as well...

It all comes down to engine character. That is the root cause.

Let's examine a steady cruising speed just to keep it simple. The primary losses (other than lost heat, which doesn't count as to the engines rated power anyway) are aerodynamic, drivetrain losses and tire losses. These all depend on speed as well. To keep the vehicle propelling forward the losses are just overcome and then you have no acceleration, i.e. velocity is constant. It is a total amount of power (cruising power) that is required to balance the losses. That power can come from high torque and low rpm or low torque and high rpm. You can guess which will offer the better fuel consumption as it is then all about rpm (of course for a given fixed displacement). It is a natural compromise in engine design one "typical" M3 type of engine is low displacement, high power, low torque, high redline, this is a racing style engine (no perhaps not at all levels of racing but surely at the elite levels such as F1), the other say a Vette is high displacement, lower power (relative to displacement), high torque, low redline. In an engine such as the latter one the power to just match all of the cruising losses as a given speed is achieved at low rpm. The rpm is even low enough to offset the fuel efficiency advantage that comes with a lower displacement. The drivetrain losses are also lower due to lower rpms (tire and aero losses are identical though if the same size tires and same body).

The gearing argument basically vanishes when you look at things from the perspective of power. Yes the two engine styles have different gearing but they do naturally to match the engines characteristic torque curve and redline.

What you get in exchange for this compromise is indeed the type of engine that "begs" to be driven hard and rewards you when youu do.

In other words we have an Oversquare engine.... Let the joyous sounds of 8000+ rpm wash away every delusion of MPG.

[swamp2]

Originally Posted by thedge9

In other words we have an Oversquare engine.... Let the joyous sounds of 8000+ rpm wash away every delusion of MPG.

While that is not a terrible summary of the situation, it does not fully convey what is happening in detail. Oversquare in itself is simply an overall feature of a total design philosophy rather than a direct cause. Although not likely, one could imagine a low rpm high torque oversquare design. I certainly concur on the last sentence!

[bimdo]

what bad gas mileage? i just got 250 miles on half a tank...

until i realized i forgot to reset the trip od after the last fillup.

[Poppin Fresh]

Because M mode On all the time and Aftermarket exhaust = beautiful engine/exhaust sounds and downshifts

[bruce.augenstein@comcast.]

Originally Posted by swamp2

Some decent replies here and some total crap as well...

It all comes down to engine character. That is the root cause.

Let's examine a steady cruising speed just to keep it simple. The primary losses (other than lost heat, which doesn't count as to the engines rated power anyway) are aerodynamic, drivetrain losses and tire losses. These all depend on speed as well. To keep the vehicle propelling forward the losses are just overcome and then you have no acceleration, i.e. velocity is constant. It is a total amount of power (cruising power) that is required to balance the losses. That power can come from high torque and low rpm or low torque and high rpm. You can guess which will offer the better fuel consumption as it is then all about rpm (of course for a given fixed displacement). It is a natural compromise in engine design one "typical" M3 type of engine is low displacement, high power, low torque, high redline, this is a racing style engine (no perhaps not at all levels of racing but surely at the elite levels such as F1), the other say a Vette is high displacement, lower power (relative to displacement), high torque, low redline. In an engine such as the latter one the power to just match all of the cruising losses as a given speed is achieved at low rpm. The rpm is even low enough to offset the fuel efficiency advantage that comes with a lower displacement. The drivetrain losses are also lower due to lower rpms (tire and aero losses are identical though if the same size tires and same body).

The gearing argument basically vanishes when you look at things from the perspective of power. Yes the two engine styles have different gearing but they do naturally to match the engines characteristic torque curve and redline.

What you get in exchange for this compromise is indeed the type of engine that "begs" to be driven hard and rewards you when youu do.

I don't take serious issue with what you've said here (except that drive train loss differences due to gearing are minuscule), but from my point of view, the elephant in the room is pumping loss.

The current M3 is geared aggressively enough so that at normal cruising speeds (75-80 mph), you're looking at something near 3500 rpm. It's very smooth there, noise levels are low and you're using minimal travel of the loud pedal to maintain speed (because you're nearing max torque), so there's nothing obvious to tell you that there's a bit of a struggle going on.

At cruise with minimal throttle, each cylinder has to pull down on the intake stroke against a significant vacuum, and that robs power from the cylinder that's firing. Pumping losses may account for as much as ten to fifteen horsepower at highway cruise, and when you figure you only need, say, 35-40 horsepower to overcome the issues you've mentioned, ten to fifteen is a lot to add.

The "solution" to pumping losses is to gear the car down to where the engine is making comparatively little power. That will dictate greater throttle opening to maintain speed, thereby directly reducing pumping losses.

If the M3 were geared so that it would be at around 2500 rpm at cruise, one might realize a highway gain of several miles per gallon.

Of course, it would then be a comparative pig in high gear (like a current Vette), but hey, you give some, you get some.

Bruce

[Da Hapa]

Originally Posted by Real Stig

Why do you care about MPG in an M3?

I don't but I can see why some might.

Efficiency is often an indicator of a well engineered product. I'm not saying that the M3 isn't a great piece of kit, but there's a reason why BMW is abandoning the NA V8 for a twin turbo 6 with the next M3/M4.

Personally, I didn't buy this car for good gas mileage. I am grateful to have a high reving, naturally aspirated V8 connected to a proper, three pedal gearbox. I'll gladly take a realistic 17 mpg in mixed driving over 20-25 for that experience.

[swamp2]

Originally Posted by bruce.augenstein@comcast.

I don't take serious issue with what you've said here (except that drive train loss differences due to gearing are minuscule), but from my point of view, the elephant in the room is pumping loss.

The current M3 is geared aggressively enough so that at normal cruising speeds (75-80 mph), you're looking at something near 3500 rpm. It's very smooth there, noise levels are low and you're using minimal travel of the loud pedal to maintain speed (because you're nearing max torque), so there's nothing obvious to tell you that there's a bit of a struggle going on.

At cruise with minimal throttle, each cylinder has to pull down on the intake stroke against a significant vacuum, and that robs power from the cylinder that's firing. Pumping losses may account for as much as ten to fifteen horsepower at highway cruise, and when you figure you only need, say, 35-40 horsepower to overcome the issues you've mentioned, ten to fifteen is a lot to add.

The "solution" to pumping losses is to gear the car down to where the engine is making comparatively little power. That will dictate greater throttle opening to maintain speed, thereby directly reducing pumping losses.

If the M3 were geared so that it would be at around 2500 rpm at cruise, one might realize a highway gain of several miles per gallon.

Of course, it would then be a comparative pig in high gear (like a current Vette), but hey, you give some, you get some.

Bruce

Drivetrain losses (transmission+differential+axles) certainly are not insignificant in the total power balance, however, those differences from one vehicle to another surely are insignificant.

How are pumping losses different at cruise as compared to WOT? In the latter such losses do not enter the equations for performance/acceleration and that makes sense. Power is determined at the crank with all losses inherent in such figures. So somehow the "accounting" is different at steady state?

Given how steep of a hill the M3 can both climb and accelerate, even in 7th gear, the car does seem to be geared a bit excessively on the performance vs. fuel efficiency side of the spectrum.

[pkimM3r]

Originally Posted by kaiv

:facepalm: You obviously have no idea how either system work so please go educate yourself instead of making such retarded posts

oh gosh stop being so douchey. My BMW possibly can't be derived from something from a shitbox like a Honda. get the fuck outta here.

[pkimM3r]

Originally Posted by serranot

I don't think I explained it clearly. With VANOS, the engine management system can adjust the phase of the cams in relation to the crankshaft, but the cam profile is the same. The same lift, the same duration. It just occurs at a different time in the combustion cycle.

With VTEC, there is a whole new set of cam lobes for the valves to follow. I do think you're correct that Honda also added variable valve timing to the VTEC system. But I don't think it's accurate to say that VANOS is VTEC with variable timing. It's not that at all.

I totally agree with you and everything you said. I was thinking more along the lines of the "idea" behind what it does and not the mechanics of it. Is it not double vanos now? controlled by a computer to do a whole not more?

BTW where is the vtec solenoid in our s65s? I can't seem to find it.

[pkimM3r]

Originally Posted by SYT_Shadow

Huh?

Not at all alike and definitely not a copy. Look at torque curves of the S65 and compare against any other engine...

Yeah, looks exactly like an s2000's....which came out in '99 and redlined at 9000rpm and has 120hp per liter....still hard to beat. and its 13 years old now....oh and btw ....VTEEEECCCCC!!

(stop being so serious ppl jees, I love my m3 just as much as you guys...i do a walk around to make sure no one has touched it and fucking wipe that shit down everytime i get back to the parking lot).

[e92zero]

would changing the diff to a different ratio theoretically improve the fuel economy on the m3? Anyone tried this yet to report back?

P.S. For the record, I am okay with the fuel economy on the M3 for the fun that I am getting out of it before someone tell me to go buy a Prius if I care about fuel consumption.

[imserious]

Originally Posted by pkim1079

Yeah, looks exactly like an s2000's....which came out in '99 and redlined at 9000rpm and has 120hp per liter....still hard to beat. and its 13 years old now....oh and btw ....VTEEEECCCCC!!

(stop being so serious ppl jees, I love my m3 just as much as you guys...i do a walk around to make sure no one has touched it and fucking wipe that shit down everytime i get back to the parking lot).

the s2000 engine was/is an engineering marvel but vtec "kicks in" around 6k to 9k. you have to really fight to keep that engine in the zone.

the s65 "kicks in" around 3.5k to 8k. way more flexible and an amazing evolution of the low displacement, high revving engine.

but yeah, gas mileage not so good.

[pkimM3r]

Originally Posted by imserious

the s2000 engine was/is an engineering marvel but vtec "kicks in" around 6k to 9k. you have to really fight to keep that engine in the zone.

the s65 "kicks in" around 3.5k to 8k. way more flexible and an amazing evolution of the low displacement, high revving engine.

but yeah, gas mileage not so good.

VTEC controller: 4.5k to 9k rpm.

[imserious]

Originally Posted by e92zero

P.S. For the record, I am okay with the fuel economy on the M3 for the fun that I am getting out of it before someone tell me to go buy a Prius if I care about fuel consumption.

My other car IS a prius I guess between the two I'm doing alright.

[pkimM3r]

Originally Posted by imserious

My other car IS a prius I guess between the two I'm doing alright.

thinking of getting a leaf for a second car but a fiat for $99 a month sounds good and the mileage shoudl be decent right?

actually my commute is only 3.5miles one way i should rollerskate it!

[bruce.augenstein@comcast.]

Originally Posted by swamp2

Drivetrain losses (transmission+differential+axles) certainly are not insignificant in the total power balance, however, those differences from one vehicle to another surely are insignificant.

What I wrote was that drive train loss differences due to gearing variation are miniscule.

Originally Posted by swamp2

How are pumping losses different at cruise as compared to WOT? In the latter such losses do not enter the equations for performance/acceleration and that makes sense. Power is determined at the crank with all losses inherent in such figures. So somehow the "accounting" is different at steady state?

There are pumping losses at WOT at high rpm, as well, although they may well be less than at light-throttle cruise. In any event, the engine has to overcome pumping losses in order to deliver a specific output at the flywheel, just as it has to overcome inherent internal friction in order to do so. I've just pointed out how pumping losses rise with light throttle at cruise, thus leading to one of the whys of the current M3's fuel consumption.

Although it's not strictly analogous, one might think of a supercharger the same way. It takes power to run the blower, so that power doesn't make it to the flywheel. The current Camaro ZL-1 and Mustang GT500 both are making more power in terms of max fuel consumption than their ratings, but some of that power doesn't make it to the flywheel.

Wizened drag racers will tell you that you've got to "feed the blower". With pumping losses, I guess you have to "feed the vacuum".

Originally Posted by swamp2

Given how steep of a hill the M3 can both climb and accelerate, even in 7th gear, the car does seem to be geared a bit excessively on the performance vs. fuel efficiency side of the spectrum.

I personally wouldn't have it any other way. Our first M3 (1995) was so much quicker and more responsive out on the highway in top gear compared to my '93 six-speed Vette that it was a revelation.