Power is Power, Right?

[OldIron82]

Ok. If you have a 400hp IDI/Powerstroke/Duramax/3208Cat...( V block ) and you then you have a 400hp Cummins/DT360/C7Cat ( inline 6 ), would they not perform the same? I've been involved in a few conversations with different people with very different opinions and I'm curious to what everyones thoughts are here. The diesel mechanic I bought my first gen 6.9 from got pretty defensive when I said want a dt360 one day because of how stout and seemingly bomb proof they are compared to v8's . He said "no, they blow up too! I've seen 6bt's with rods through the block when people start doing dumb **** with them!" He then spent almost 10 min talking about grenaded 6 cylinders and snapped cranks, etc. I guess I struck a nerve?
I'm guessing the 6's would "out perform" the v8's in the torque department? I've heard from what seems like everyone straight 6's have a huge flat torque curve that 8's can't touch. The only experience I have with that is with gassers. My dad has a 79f150 2wd longbed with the legendary 300 6 with a c4 and that thing just PULLS compared to my jacked up 78 f150 with the 351m. Yes, it has 35's on the wheels but I have 4.56 gears and a NP435 manual tranny.
Will us v8 guys always be second best to the straight 6 army?

OI82

 

[79jasper]

Imo, he may have been on a rant, but he's right.
I've also heard inline torque is better, but can't say I've ever seen proof of such.

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[jaluhn83]

Yes and no. Horse power is the same, but the actual engine power curve and engine reliability is not.

HP is a function of rpm & torque - 400 hp at 6000 rpm and 400 hp at 900 rpm are the same power, but vasty different torque. drivability is going to depend greatly on the shape of the power band - peak hp is only one point on that curve.

Generally speaking, an I-6 engine typically has more low rpm torque due to a longer stroke, and the v8 is a higher rpm shorter stroke engine that makes power more from rpm. I-6 typically also has more main bearings, and is inherently a better balanced engine. But, proper engineering can easily offset those factor, so there is no inherent reason a V8 is better or worse.

Generally packaging reasons are more relevant to the engine configuration - I6 is a long narrow engine requiring a long hood with significant unused space on the sides, while a V8 is going to be shorter and fill that side space better - ie allow a more efficient use of vehicle space and length. Both can be good or bad engines though - depends on the overall design and engineering.

 

[Number21]

No, definitely 400hp is not 400hp. I've spent countless hours researching putting a 5.9 in place of a 6.0. The consensus is, to get the same "performance" from the I6 you need more horsepower than a comparable V8. The V8 revs faster and higher. Cummins red line is super super low. They have a flat torque curve because the engine only runs at a very limited RPM range! Cut the V8 curve off after 2900 RPM and it's pretty flat too.

With that said, a truck with a 400hp I6 might feel slower than a truck with a 400hp V8, but it might tow better. You have to choose between a truck or a race car, neither usually works good as both.

 

[icanfixall]

Any straight 6 or 8 cylinder WILL make better torque no matter what hp you see. Thats the nature of the beast. Look at many of the early semi truck engines. they are a straight 6. Sure we have some V8 engines too but.. More torque for the hp on a straight 6 engine and at much different rpm areas. HP is how fast you climb the hill. Torque is how steep the hill is you are climbing.

 

[Number21]

The big difference when we are talking about pickup trucks is gearing. A million ft lbs of torque at 1200 RPM is cool, but if you only have 3-5 gears, it's not all that useful. In a big truck 10 speeds is considered low. A V8 helps make up for the lack of gears in a pickup truck. An inline 6 with a 3 speed will tow a house, but never be "fast" no matter how much torque it has.

 

[direwulf23]

I don't reckon I'm going to add completely new information, but I'd like to comment.
Horse Power essentially represents how a vehicle pulls itself, or how fast it is. Torque essentially represents how much a vehicle can pull, or how much of a load it can move.
As has been stated, an inline 6 has more low end torque, which gives it excellent towing/ pulling, but not much of a top end speed unless you have more gears that allows it to operate at it's peak efficiency of low RPMs.
For example, I drive a Freightliner straight truck with a Cat C7 and Eaton 9 spd (peak torque @1450 RPM) and my counterpart at work drives a Kenworth with a Paccar PX9 with a 10 spd Eaton (I don't know the specs on this engine). Our trucks have the same rated HP. However, for example, his truck moves faster down the road because he has that one extra gear, at 60 MPH his engine is running 1800 RPM and my truck is running at 2100 RPM, which means my truck is running further out of its "power band". So, when any sort of load is added (a hill) my truck "falls down" harder, or slows down more, and I can't pull a hill at reasonable highway speeds.
On the other side, from a start or when just a matter of pulling, my truck will work just as hard as his, if not even better, but slower.
To my knowledge, all big trucks use the inline 6, but they also have more gears which allows the engine to operate within its maximum efficiency range, power band, across a larger range of speeds.
Umm, sorry for all of the wind.

 

[hce]

My answer to this question of horsepower or torque is to arm yourself with knowledge. Start by learning of Thomas Savery and James Watt.

 

[madpogue]

"Horsepower sells cars. Torque wins races." -- Carroll Shelby

 

[direwulf23]

Everyone gives me confused looks or laughs when I tell them my 79 F350 had a 300 I6. I tell you what, though, I load that truck up and it just goes "chugalug-chugalug" and hauls everything I put in it and attach to it. It's like a diesel gasser. Love the 300.

 

[hce]

"Horsepower sells cars. Torque wins races." -- Carroll Shelby

I would be careful not to take that out of context. Mr shelby seemed to use high winding v-8's. They produced torque, but still a little high strung.

 

[OldIron82]

Wow! Very awesome gentlemen thank you for the plethora of info.

Ok, so next question. If I had a seriously built IDI with say maybe a Omega Moose pump and dt466/Powerstroke sized turbo that was absolutely jacked, and you placed that next to a evenly matched similar powered inline 6...I would guess speaking from a purely "powerband" point of view there is no reason the V8 couldn't pull the same amount of weight the I6 could but just at a lower gear with the RPM's higher?

I guess what I'm asking is at whatever RPM the two engines hit the same maximum torque number they should be neck and neck? Possibly the V8 would just slow down sooner?

 

[direwulf23]

If they produced the same torque they should pull the same weight, I would think. There are several other factors involved in that, but for the sake of argument.
What I think it'd really come down to would be having the gears to keep the engine producing peak power, but yes I think the difference between the V8 and I6 basically boils down the V8 produces most of its power at a higher RPM than the I6.

 

[FORDF250HDXLT]

Everyone gives me confused looks or laughs when I tell them my 79 F350 had a 300 I6. I tell you what, though, I load that truck up and it just goes "chugalug-chugalug" and hauls everything I put in it and attach to it. It's like a diesel gasser. Love the 300.

the 300 is the best gas engine ford ever built.

 

[KZF250]

My '95 Ford E150 with the 300 has been the best $600 ever spent.