Couple/few questions I've had

[mrblotto]

I know I know....I could google the answers, but I would miss all the 'personal' responses lol

1. Why are header pipes all goofy, going up and down and around before they merge into the 'main pipe'? Can't they just go straight into the main pipe without doing all the bending and curving?

2. Why are the exhaust pipes on diesel trucks waaaaaaaay larger in diameter vs. gasoline ones?

3. While sitting in traffic/at a light, I'll notice that on some SUV's / trucks, the rear shocks are.....dammit...I cant remember the term (I've had a few). One shock will be in FRONT of the rear axle, and the other one will be BEHIND the rear axle. What's up with that?

I guess that's all I have for now

 

[slashbinslashbash]

1) It has to do with timing. The cylinders all fire at different times, and ideally you want the exhaust pulses to enter the main tube in an equally spaced-out manner instead of having some of them "collide" and cause a pressure peak.

 

[LTC8K6]

1. IIRC, they want them to be the same length?
2. Higher compression ratio means more air flow?
3. Just different suspension type / design?

 

[NutBucket]

2. Bigger displacement (over 6L) means more air is leaving the engine compared to your average gas engine. Plus, they're all turbocharged so having the least restrictive exhaust possible allows for more efficiency.

3. A bit speculative but it may be to help combat axle wrap, even if just a little.

 

[radioouman]

For 3, the axles turn in different directions. Viewed from that driven wheel, one axle is turning CW and the other is CCW. The shock placement is used to prevent tire hop by reducing twisting of the axle.

 

[96Firebird]

For number three, the word you're probably thinking of is staggered. This type of setup reduces wheel hop on leaf spring vehicles.

 

[slashbinslashbash]

1. IIRC, they want them to be the same length?

Equal-length is usually better for the performance of the engine, but there are trade-offs in packaging efficiency (equal-length is usually bigger),weight (both of which can affect the performance of the car as a whole, e.g. if suspension, steering, or other components have to be moved due to the bigass exhaust headers; and added weight is always the enemy of handling), and cost.

http://www.vikingspeedshop.com/equal-length-vs-unequal-length-subaru-exhaust-manifolds/

 

[Bartman39]

2. Why are the exhaust pipes on diesel trucks waaaaaaaay larger in diameter vs. gasoline ones?

Couple of different things... First off the turbo needs a free flowing path to exhaust the gases coming from the engine... Next is the heat needs to be expelled from the turbo also and a large exhaust pipe will also help this issue (water cooling is only a part of the cooling)...

Plus it looks cool...