Why 4 > 6

[Hopman]

A truck engine should have it's torque down low, say between 1,000-2,500 revs. Besides, that's where the torque should peak anyway, because that's about the revs where you should be in the highway.

 

[Great_Big_Abyss]

A truck engine should have it's torque down low, say between 1,000-2,500 revs. Besides, that's where the torque should peak anyway, because that's about the revs where you should be in the highway.

Okay, but why would you want peak torque when you're cruising on the highway? And if that were the case, there would be absolutely no point in shifting past 2500 rpms. For example, my engine peaks at 3000 rpm. Past that, my motor actually feels kind of breathless, so I rarely go past 4000 rpm.

The ideal situation is to have torque peak very low, but then to remain at about the same level until close to redline.

That, btw is what variable valve timing (such as Honda's VTEC) does.

Small engines make their peak torque at very high rpms, and are gutless at low rpms. VTEC optimizes valve timing and lift to flatten the torque curve so that you get good torque numbers at both low and high rpms.

Conversely, large engines make a lot of torque down low, but can lose steam in the higher rpms. valve timing would have an effect here, by giving your higher rpms some usefulness.


At one point, BMW was experimenting with infinitely variable valve timing. Instead of using cam shafts to open the valves, they were using solenoids. They could open/close the valves as much and when they wanted to. I think they had problems with reliability, though.

 

[adsm08]

Okay, but why would you want peak torque when you're cruising on the highway? And if that were the case, there would be absolutely no point in shifting past 2500 rpms. For example, my engine peaks at 3000 rpm. Past that, my motor actually feels kind of breathless, so I rarely go past 4000 rpm.

The ideal situation is to have torque peak very low, but then to remain at about the same level until close to redline.

That, btw is what variable valve timing (such as Honda's VTEC) does.

Small engines make their peak torque at very high rpms, and are gutless at low rpms. VTEC optimizes valve timing and lift to flatten out the valve timing so that you get good torque numbers at both low and high rpms.

Conversely, large engines make a lot of torque down low, but can lose steam in the higher rpms. valve timing would have an effect here, by giving your higher rpms some usefulness.


At one point, BMW was experimenting with infinitely variable valve timing. Instead of using cam shafts to open the valves, they were using solenoids. They could open/close the valves as much and when they wanted to. I think they had problems with reliability, though.

Ford is working on that with the v-8s. The new tritons have the VCT systems.

 

[Great_Big_Abyss]

Ford is working on that with the v-8s. The new tritons have the VCT systems.

Are you saying they're working on the solenoid valve timing? It's a good idea. That way, you could probably get a torque curve from any engine that's as flat as a table. BTW, porsche uses variable vane turbos on their 911-turbos to achieve the same effect.

Nothing beats a mechanical link for reliablilty, though. Crankshaft to chain to camshaft to valve stem. There's just so many things that can go wrong with electronic components....I've never one hundred percent trusted them.

 

[adsm08]

no, they are working on the non-solenoid variable valve timing system, like the V-tech or the Escort system. The 5.4s have it and so do the mustang 4.6s.

 

[85_Ranger4x4]

The Colorado's 3.7L I-5 makes:

242 hp @ 5600 rpm
242 lb-ft @ 4600 rpm
Redlines @ 6300

My 4.0 SOHC makes:

207 hp @ 5250 rpm
238 lb-ft @ 3000 rpm
Redlines @ somewhere around 6500 rpm.

So I have substantially less horse power at a slightly lower rpm, but I have about the same torque at a substantially lower rpm. Torque is the number that matters here, and more torque at lower rpm is better.


BTW my truck has enough torque that i can put it in low-range and just idle over pretty much anything. Try doing that with a little 4-banger.

My measily 115hp at 4600 and 150 lb-ft at 2600 RPM is enough for my little truck in 4x4L. The big problem is that it becomes a crutch for the lack of power and I can't do much without it (like clean my 235/75-15 mud tires)

Are you saying they're working on the solenoid valve timing? It's a good idea. That way, you could probably get a torque curve from any engine that's as flat as a table. BTW, porsche uses variable vane turbos on their 911-turbos to achieve the same effect.

Nothing beats a mechanical link for reliablilty, though. Crankshaft to chain to camshaft to valve stem. There's just so many things that can go wrong with electronic components....I've never one hundred percent trusted them.

'03+ Powerstroke diesel have VGT's, they work great now that they have improved the fuel, otherwise they would stick when babied.

no, they are working on the non-solenoid variable valve timing system, like the V-tech or the Escort system. The 5.4s have it and so do the mustang 4.6s.

They currently have VCT, but I think it is only a two stage mechanical system at the moment. F-150's got it in '04, and the Mustang and F-250/350 in '05. I am pretty sure that the base 2V 4.6 in the F-150 doesn't have it though.

 

[Will]

The Colorado's 3.7L I-5 makes:

242 hp @ 5600 rpm
242 lb-ft @ 4600 rpm
Redlines @ 6300

My 4.0 SOHC makes:

207 hp @ 5250 rpm
238 lb-ft @ 3000 rpm
Redlines @ somewhere around 6500 rpm.

So I have substantially less horse power at a slightly lower rpm, but I have about the same torque at a substantially lower rpm. Torque is the number that matters here, and more torque at lower rpm is better.


BTW my truck has enough torque that i can put it in low-range and just idle over pretty much anything. Try doing that with a little 4-banger.

The problem with looking at the peak torque--the Colorado is pretty strong down low despite them using their 4,600rpm figure.

Here's the Ford 4.0:

And since it was mentioned, the little Honda VTec 3.5, which easily beats the other 2 in low rpms:

 

[Fx4wannabe01]

The colorado is still available with the 3700 I-5...they didn't axe it. Also, that engine makes more power/torque than my 4.0 SOHC, albeit at higher RPM.

Poster you quoted or commenting on was talking about the 4200 I6 in the trailblazer.....

 

[Funnyman141]

my little 2.3 did pretty good pulling my 95 olds (had a blown motor and stuck brakes) even though the o2 sensor and timing were out of wack. It barely ran at idle but when it started pulling it motivated the olds pretty well.

 

[Great_Big_Abyss]

And since it was mentioned, the little Honda VTec 3.5, which easily beats the other 2 in low rpms:

That's VTEC in play right there!

 

[Tractorman]

I love the turbo volvo engines. you rest your foot on the pedal and it spools up and gets you running at 85 before you even notice.

As for the chevy I-5 making the power at high RPM, most chevy engines hit their peak near red-line. The D-max engines are about half worthless because even though they put out more torque at peak than the Powerstroke they do it at about 2850 RPM when they have a 3100 red-line. The 6.4 makes its peak torque around 1900-2100 giving it a much higher rated tow capacity.

End result, Ford can tow more because it can get more weight started off.

Wrong on the Duramax. Peak TQ on a DMax comes at 1600 RPMS.