Engine technology thread.

[bambbrose]

Originally Posted by Dimman

Factory cars are coming with widebands these days?

Nearly all new cars are wideband.

THe civic vx had one in 1992.

[OrbitalEllipses]

Originally Posted by Dimman

Factory cars are coming with widebands these days?

I believe the Mazda 3 does. IIRC, German cars generally do too.

[Ryephile]

Originally Posted by Dimman

Factory cars are coming with widebands these days?

I'm sure arghx7 can comment much further, as he's definitely an encyclopedia of OEM powertrain equipment knowledge, however the engines that use OEM WBO2 off the top of my head that I have personal experience with are the '07+ MINI, '07+ BMW N54 and beyond valvetronic turbos, GM LNF, VW FSI & TSI. Of course, all of those are modern DI boosted, but still, they're all "last gen" engines at this point.

Originally Posted by bambbrose

Nearly all new cars are wideband.

THe civic vx had one in 1992.

I get what you're saying, that WBO2 isn't anything new, but I wouldn't say nearly all new cars have them. Curiously, the VTEC-E from back in the day used WBO2 for lean-burn to get the awesome fuel economy, however such implementation today would miserably fail emissions testing.

There are a boatload of average engines out there made on the main premise of being cheap, cheap, reliable, and then cheap. I can't say I'm too surprised the FA20 doesn't have WBO2, since it's naturally aspirated, however the direct injection aspect implied to me they would belly-up for the extra control for that sort of precision capability the GDI offers.

[SkullWorks]

I am very surprised that there is no WB O2 present, if that is indeed the case there will be both power and economy left on the table, readily extractable with, fuel and timing control, whatever that may end up being....

[Ranatsu]

There are no Subaru's that come factory with a WB02 that I am aware of. I'm not 100% on the 2012 Impreza/Forester/Outback, but something tells me they are using the same narrowband setup.

[SkullWorks]

Originally Posted by serialk11r

A lower rod length increases the speed of the piston around the bottom of the stroke, and around the top. It increases the speed around the middle of the stroke.

Fixed your text in BOLD added in blue

http://photos.motoiq.com/MotoIQ/Tech...istonvel-L.jpg

Picture makes it pretty clear, STOLEN from Motoiq.com article on Long Rod SR20VE

[bambbrose]

Originally Posted by SkullWorks

Fixed your text in BOLD added in blue

http://photos.motoiq.com/MotoIQ/Tech...istonvel-L.jpg

Picture makes it pretty clear, STOLEN from Motoiq.com article on Long Rod SR20VE

Correct.

TDC and BDC have velocity of zero, instantaneous acceleration is zero, but Jerk is max, right? It is the Jerk that causes the damage.

With Jerk at max, and velocity low, there is a higher chance of breaking the oil barriers that protect.

Long rod has same Jerk as short rod, as long as crank is the same. Infinitely long rod has same jerk as short rod, as long as crank is the same.

The only thing that changes is the side loading because the angle of distribution of the forces.

[serialk11r]

Yea I ignored the middle because acceleration is low there. Sorry whichever post that bolded text came from had another typo again, oops.

[bambbrose]

Originally Posted by serialk11r

Yea I ignored the middle because acceleration is low there. Sorry whichever post that bolded text came from had another typo again, oops.

Acceleration is zero at TDC, BDC, and the middle right? So it is essentially a full sine wave within the 1/2 wave of velocity.

Acceleration is max at the midpoint between TDC and the middle, aka 1/4 of the way up and 1/4 of the way down?

[Want.FR-S]

As I tried to understand the benefit of using long or short rod, I found your explanation was confusing so that is why I clarify it.

We are here trying to learn something from this site. Since this is the technical section I would expect the information posted here is technically correct, and thus the nitpicking. If I offend you in some way, I apologize.

BTW, the tangent circles means two circles tangent on a single point. In your explanation about the crank and rod circles, they only tangent at TDC and BDC, and you know it for sure. I would like to point that out since those circles are not always tangent. Nothing more.

[Want.FR-S]

Originally Posted by bambbrose

Acceleration is zero at TDC, BDC, and the middle right? So it is essentially a full sine wave within the 1/2 wave of velocity.

Acceleration is max at the midpoint between TDC and the middle, aka 1/4 of the way up and 1/4 of the way down?

Hmmm... velocity is zero at TDC and BDC. The position of the piston is like a full sine wave.

The maximum velocity is reached between TDC and 90 degree and also between 270 degree and TDC, closer to 90/270 degree rather than TDC. In the wiki example with 2" stroke and 6" rod, the maximum velocity is reached at 73.xxx degree.

Correct me if I am wrong on this....

EDIT: just to clarify: with a infinite long rod, the graph of acceleration becomes like a cosine/since wave. Here is the graph from MotoIQ as well:

http://photos.motoiq.com/MotoIQ/Tech...vtpFm&lb=1&s=A

Look at the light-blue line for theoretical rod length of 10,000 mm (10 meter long).

[SkullWorks]

No Jerk is less with a Longer rod because it is accelerated slower away from TDC,

Piston velocity is MAX at the mid point in the stroke, that's where the lever arm is moving closest to perpendicular, the closer to infinite the rod length the closer to perpendicular,

[SkullWorks]

I think the maximum acceleration happens around the 73.xxx degree but max speed is right at mid stroke

[serialk11r]

Originally Posted by Want.FR-S

As I tried to understand the benefit of using long or short rod, I found your explanation was confusing so that is why I clarify it.

We are here trying to learn something from this site. Since this is the technical section I would expect the information posted here is technically correct, and thus the nitpicking. If I offend you in some way, I apologize.

BTW, the tangent circles means two circles tangent on a single point. In your explanation about the crank and rod circles, they only tangent at TDC and BDC, and you know it for sure. I would like to point that out since those circles are not always tangent. Nothing more.

It's fine, I was just bothered because there's no point in continuing to nitpick after the terms were clarified.

The reason I mention tangent circles is that while the 2 circles are not always tangent, the distance between them (along a perpendicular axis) is equal to the distance between the centers of the tangent circle (circle the rod makes at BDC) and the circle at any other crank angle. Do you understand what I mean?

bambbrose, the velocity at BDC/TDC is 0, but since acceleration is the 2nd derivative of the position, the acceleration is greatest at BDC/TDC.

The point of maximum acceleration should be at TDC always. Max speed depends on the rod:stroke ratio, but it's somewhere around "mid stroke".