inline 6 vs. V6?

[PowerMac4Ever]

Originally posted by: Wadded Beef

Originally posted by: PowerMac4Ever

Originally posted by: drunk7daysaweek

Originally posted by: Wadded Beef
I've always assumed straight 6's were better since they are mostly in higher end cars like supras, bmw's, and skylines...but what makes them better? or are they?

I cant believe u mentioned supra in the same sentence as BMW

Agreed, the Supra was more expensive and far superior to any straight-six BMW 'back in the day. It's not fair to compare different classes of cars like that.

ehh...m3 anyone?

Well to be fair the E46 was released well after the Supra stopped being imported to the US.

 

[Zenmervolt]

Originally posted by: 91TTZ

Originally posted by: sao123

Inline engines have a longer stroke than the compact v configurations.
Any freshman who has had a first year physics course knows that a longer arm turning a radial device has more torque than a shorter arm.

And anyone who is past a freshman level education would know that you are wrong. First of all not all I6 engines have a longer stroke than V6's. You can give an I6 a long stroke, or you can give it a shorter stroke. There is nothing inherent in the I6's design that dictates that it must have a longer stroke than a V6. My Nissan's V6 has a longer stroke than Nissan's I6 in the Skyline. Bore is about the same, but their I6's stroke is shorter.

Also, that's been a point of contention forever in the domestic circles. You had people who believed that when they stroked their engine, it was the longer stroke itself which gave them the added torque. Others disagreed and believed that it was strictly the increase in displacement from stroking it that gave them more torque. They pointed out that if you increased the bore size to deliver the same displacement as you'd get if you stroked the engine, you'd have the same amount of torque. As a benefit, you can rev the engine higher if it was a larger bore to stroke ratio. If you stroke a 350 to 383 ci, you get more torque. But it's not because you gave it a longer stroke, it's because you gave it more displacement.

You do get more torque at low RPM at least from decreasing the bore and increasing the stroke. I.e. two engines with identical displacement but different bore/stroke ratios will have different torque curves, with the engine with the longer stroke having more low-RPM torque. Of course, this is also due to the fact that the smaller bore means smaller diameter intake ports which increase the velocity of the intake charge which is itself a boon to low end torque while restricting breathing at higher RPM. So technically having an undersquare design will yield more low-end torque at the expense of high RPM abilities, whereas an oversquare design will have better high RPM characteristics and less low-end torque even if both engines have the same total displacement.

ZV

 

[91TTZ]

Originally posted by: Zenmervolt

It's true that most I6 engines have a smaller bore and longer stroke, but that is not something that is necessarily inherent in the inline arrangement, so you cannot use it as a rationale for believing that an I6 has more torque than a V6 by default.

ZV

Agreed, and I'd like to throw in an example.

Let's compare 3 different engines:

The 300ZX V6's bore/stroke is 87.5mm x 83mm

The Supra I6's bore/stroke is 86mm x 86mm

The Skyline I6's bore/stroke is 86 x 73.7

With these 3 examples you can see that not all I6's need to have a long stroke. It's not inherent to the design. You can choose to have a longer stroke, or you can choose to have a shorter stroke. The 300ZX has a V6, and has a bigger bore than stroke. The Supra I6 is square, having a stroke and bore of the same size. But then the Skyline illustrates that some I6's have a much smaller bore than stroke. They chose to give that I6 a short stroke so they could rev it higher, and while its bore is roughly the same size as the 300zx's, the stroke on that I6 is much shorter.

 

[91TTZ]

Originally posted by: PowerMac4Ever
[
You say you hate Fast & Furious yet you use it to help make your point? wtf...

Anyway, I6 >>>>> V6, in terms of sound.

Yes, I didn't like the movie. But I used it as an example because it shows that the producers felt that the Z's V6 had a more pleasing sound than the Supra's I6. The Supra has a steady drone to it which doesn't make it sound good.

 

[91TTZ]

Originally posted by: Vic

Engine sound is almost entirely dependent on exhaust port, header, and exhaust design, and the number of cylinders... not engine configuration itself.
You know the unusual Subaru boxer sound? That's because of Subaru's factory unequal length header design. If you put equal length headers on, it sounds just like a Honda I4. I have seen it, heard it, and am completely serious.

I disagree. Engine configuration most definitely has an influence on the exhaust note. You're not going to find headers that makes an engine with 2 banks sound the same as an engine with only 1 bank. Headers don't work that way. With 1 bank you can get a scavenging effect from all the cylinders in the bank, while with a V engine the bank is half the size and the headers will obviously be designed totally different.

 

[JulesMaximus]

Straight 6 is better balanced. V6 is an inherently unbalanced design and needs counterbalances so that it doesn't vibrate itself to pieces. The reason the V6 engine is so popular though is that it is a much shorter package than a straight 6. You couldn't put a straight 6 in a FWD car which is why there are so few straight or inline 6 cylinder engines. From a manufacturing standpoint it makes sense to use one engine design in many different vehicles to save on development costs and manufacturing costs. Look at the Nissan VQ35. That engine is in 4 different Nissan cars/SUVs and at least 3 different Infiniti cars.

 

[91TTZ]

Originally posted by: Zenmervolt
You do get more torque at low RPM at least from decreasing the bore and increasing the stroke. I.e. two engines with identical displacement but different bore/stroke ratios will have different torque curves, with the engine with the longer stroke having more low-RPM torque. Of course, this is also due to the fact that the smaller bore means smaller diameter intake ports which increase the velocity of the intake charge which is itself a boon to low end torque while restricting breathing at higher RPM. So technically having an undersquare design will yield more low-end torque at the expense of high RPM abilities, whereas an oversquare design will have better high RPM characteristics and less low-end torque even if both engines have the same total displacement.

ZV

Like you stated in the second half of your post, I think it's the smaller valves and increased intake/exhaust velocity at lower rpm's that give the longer stroke design more low end torque. I don't think it's solely due to the longer stroke itself. I've heard a lot of domestic guys also claim that pushrod engines with 2 valves per cylinder have the low-end torque advantage, while DOHC engines with 4 valves per cylinder give up some power down low in favor of a high-end gain. How true that is, I'm not sure.

It also makes sense that if you have an engine that's capable of breathing well at higher RPM's, you're going to cam it differently than if you had an engine that didn't breath well at higher RPM's. Camming it to produce more torque higher in the rpm range will give up some torque at low rpm's.

 

[Zenmervolt]

Originally posted by: 91TTZ

Originally posted by: Zenmervolt
You do get more torque at low RPM at least from decreasing the bore and increasing the stroke. I.e. two engines with identical displacement but different bore/stroke ratios will have different torque curves, with the engine with the longer stroke having more low-RPM torque. Of course, this is also due to the fact that the smaller bore means smaller diameter intake ports which increase the velocity of the intake charge which is itself a boon to low end torque while restricting breathing at higher RPM. So technically having an undersquare design will yield more low-end torque at the expense of high RPM abilities, whereas an oversquare design will have better high RPM characteristics and less low-end torque even if both engines have the same total displacement.

ZV

Like you stated in the second half of your post, I think it's the smaller valves and increased exhaust velocity at lower rpm's that give the longer stroke design more low end RPM. I don't think it's solely due to the longer stroke itself. I've heard a lot of domestic guys also claim that pushrod engines with 2 valves per cylinder have the low-end torque advantage, while DOHC engines with 4 valves per cylinder give up some power down low in favor of a high-end gain. How true that is, I'm not sure.

It also makes sense that if you have an engine that's capable of breathing well at higher RPM's, you're going to cam it differently than if you had an engine that didn't breath well at higher RPM's. Camming it to breathe well up in the rpm range gives up some low rpm performance.

Yeah, there are so many variables for engine performance that it can't really ever be nailed down to just one particular reason. That's one of my fascinations with engines actually. It's so simple in terms of the basic theory, but the interplay of factors is so complex and interesting. In another life I probably would have been an engineer instead of a portfolio analyst, but it's kind of the same situation; simple baseline theory but so many linked factors influencing the ultimate outcome.

ZV

 

I dunno, but my car is faster than your car!

 

[Cruez]

Originally posted by: Vic

Originally posted by: 91TTZ
I think I6's tend to have a droning sound. V6's sound better.

In TF&F (hate that movie) when they wanted engine sounds for the Supra they used a 300ZX for its sound.

Engine sound is almost entirely dependent on exhaust port, header, and exhaust design, and the number of cylinders... not engine configuration itself.
You know the unusual Subaru boxer sound? That's because of Subaru's factory unequal length header design. If you put equal length headers on, it sounds just like a Honda I4. I have seen it, heard it, and am completely serious.

I believe the configuration DOES have a direct effect, because of the firing sequence differences in the different designs... there is quite a big difference in sound comparing a Honda VFR-750 (V4 engine) and a say a Kawasaki ZX7 (inline 4) you can tell the two apart a mile away.

 

[SuperTool]

Originally posted by: SuperSix

Originally posted by: SuperTool
I6 engines have the most number of bearings per cylinder.

Yes, but the crankshafts are MUCH longer - so they can't take as much HP as a V6 crankshaft can.

Torquey, smooth, and HUGE.

/me prefers V6's...

How come some Skylines are putting out 1000hp out of 2.6L I6?
I think inline can take more hp than V6.

 

[OS]

Originally posted by: SuperTool

Originally posted by: SuperSix

Originally posted by: SuperTool
I6 engines have the most number of bearings per cylinder.

Yes, but the crankshafts are MUCH longer - so they can't take as much HP as a V6 crankshaft can.

Torquey, smooth, and HUGE.

/me prefers V6's...

How come some Skylines are putting out 1000hp out of 2.6L I6?
I think inline can take more hp than V6.

I think that guy, his name refers to the grand national. Which is a turbo V6 also capable of 1000+ HP.

see here