The main problem with those engines is that the torque curve has a big bulge at the top end. I remember that the engine in the Celica GTS dropped into the low lift cam when they shifted to second. Also, you have to downshift several gears to get to the power. I normal traffic, when you want to press down and go *right now*, there's nothing there.


I'll add the weight and size of the engine as important too. So yes, I think I can agree that if the Atlas I-5 is less fuel efficient than the Toyota or worse in the other criteria, it will be disappointing overall. The fact that it has one less cylinder bodes well for it, though, in the fuel efficiency department, since more cylinders for a given displacement means more friction, everything else the same (never is). I guess time will tell.

 

Well shat. What are you guys debating then? haha. Let me know when you guys figure something out here then.

 

The Chevy I5 has more peak power than the Toyota V6, but that's not too important. What matters is which one has more useable power and better economy, more reliable, better table manners, etc.

 

"old SAE ratings"? Since when did Toyota follow the old SAE ratings? Yes, the SAE rating method was revised, but Toyota (& Honda) didn't follow the old standards: they used their own, proprietary (& unorthidox, IMO) methods - which is why virtually everybody else didn't suffer the hp drop when the new SAE standards were adopted.

 

In the spirit of beating the dead horse at the glue factory . . .

The Atlas I-5 redlines at over 6000 RPM, so in any sort of acceleration test, the engine would spend most of its time over 4000 RPM, which means that the Atlas may actually do somewhat better than the Toyota even in the "real world".

If what you're looking for is torque/horsepower at full throttle at 2500 RPM (at a fixed RPM, it doesn't matter which metric you use, since you can easily derive one from the other), then you'll want the bigger engine. Note that if you have an automatic transmission, you'll never be at full throttle at 2500 RPM unless you're between 0-10 MPH, as the tranny will downshift.

 

In the "real world" people spend a tiny fraction of their time (if ever) at WOT in a pick up truck.

 

Naaah, I have a couple friends in Chevy Duramax's/Allisons and Ford Powerstrokes chipped up that love to eat ricers, even Mustangs and Camaros.

They get to Wide Open...

We were pulling a really heavy load awhile back (albiet in an older Ford Diesel so not as much power) and ran Wide Open just to hit 70mph (I65 Speed Limit in IN) and had to keep it to the floor the whole way. 3hrs of Wide Open.

 

Sure. By extension, maximum power only matters a tiny fraction of the time (if ever), so what's the point?

 

Power at a given RPM always matters as that affects the overall driving experience. The next question is what given RPM is most important to the average pick up truck driver. I wont' pretend to know the answer to that but I'll go ahead and guess.

That is, afterall, the entire reason why pacer made his typical assumption that since it was a Toyota, it must be peaky in its powerband, and then critisized me for not understanding power 'under' the curve.

 

Right, but if you are not going WOT, then it doesn't really matter so much...

To use the two engines that were discussed earlier...

Toyota: 236 hp @ xxxx rpm, 266 lbft @ ???? rpm
Atlas I5: 242 hp @ 5600 rpm, 242 lbft @ 4400 rpm

Those numbers are for WOT only. It isn't like, when you step on the throttle (say 25% throttle), that when you pass 4400 rpm in the I5, you automatically just hit 242 lbft. Those numbers are the peaks available at WOT.

So, if WOT hardly matters to a person in a pickup (which I disagree with; WOT definitely matters when towing/hauling, and when you get on it to merge, etc. - but in "normal driving", hopefully they aren't hitting WOT constantly), then who cares about an extra 24 lbft of torque available at WOT? Say during your normal drive to work, you never go above 50% throttle. So say you only ever see 120 lbft @ 3000 rpm in the 4.0 V6. It isn't like the I5 can't make that amount of torque at the same rpm. Maybe it takes 55% throttle blade opening instead of 50%, for example. Any driveability/feel issues will come down to throttle progression calibrations (i.e. how far the pedal is pushed to get a certain actual throttle blade opening and corresponding torque). Both engines could be set up so that the same amount of pedal travel gives the same amount of torque (but the throttle blade would probably be open a bit more in the I5 vs. the V6). That is, of course, until WOT is achieved, at which point the Toyota would have an advantage until the upper RPM ranges.

It is only under full throttle at the respective engine speeds that one would ever feel the 242 or 266 lbft.

Anyway, ultimately the peak numbers and the speeds at which they are attained (which is what are shown in vehicle/engine specs) DO matter at some point or another, even in pickup trucks. Full throttle accels, towing/hauling, etc. And, of course, for bragging rights. Otherwise, we wouldn't be in the power/torque war that we are in...

I'm not saying the 4.0 V6 isn't (slightly) better suited for a truck application with more torque available at a lower RPM; it probably is. I only made this post because you commented that WOT is only ever an issue for a tiny fraction of the time. I'm thinking maybe there is some terminology confusion when you are trying to answer teal98, or something.

 

I realize this, but would the resulting power at partial throttle not typically be derived from / closely related to the power at full throttle?

 

Not necessarily. What are you defining as partial throttle, 1/2 way down on the gas pedal? Throttle plate one half open? Does it really matter that much whether you've gone through 40% or 50% of your gas pedal travel to accelerate at a certain level?

I remember my aunt's 1976 Buick Skylark with 231 CI V6 (3.8 liters in modern terms). The throttle linkage was set up to give you a lot of response with a little bit of travel. So if you drove it and never went past halfway, you'd think it was a peppy car. But then when you used the other half, you'd realize it had already been giving all it had

So I don't think you can define partial throttle in any useful way, except by measuring fuel efficiency at various partial throttle horsepower outputs (or maybe NVH, etc.).

 

Yeah I'd tend to guess fuel usage at partial throttle relative to fuel usage at full throttle would probably be a good indicator. Obviously the fuel usage wouldn't be linear with the power output, but it would at least probably be relative.