Difference between 175 hp on I4 and 175 hp on V6/I6?

[buymeabmwm3]

Its all about personal preferences anyways. There are so many factors to weigh on engine characters, torque, hp, configuration, displacement, manufacturer. Best way is to go out and sample engines to see what things you like. I wwould never buy anything other than a german I6, some poeple swear by turbo 4s and others would only take a big american V8.

[burly]

Well, I stated that I was making many assumptions. Given only that the originial question asks the difference between an I-4 and a V-6 of equal peak HP, many assumptions have to be made to even carry a discussion. However, in general, it is safe to assume that the V6 is of greater displacement than the I4 and that the I4 is not turbocharged. If these don't hold true, then the conversation is even more complex and a direct engine to engine comparision would have to be made.

As far as driveability and curves go, thats what I was getting at, that the power/torque curve has more effect on the driveability than the peak power. That is the reason I compared the two engines that I did. The power curve on the I4, while peaking at a similar number as the V6, has a much steeper power curve that is high RPM biased. The V6 has a flat curve that is more center biased. If I had the graph, it would be a much easier explanation.

In other words, if you really want to compare the two, we need the specific two engines in the comparision, and the cars they are in.

[Steel]

By the by, the only V engine that is naturally balanced is a V12, because it is basically comprised of 2 I6's next to each other, since I6's are naturally balanced. Boxer engines balance naturally too, buuut that's about it.

[Some1else]

Originally Posted by Steel

By the by, the only V engine that is naturally balanced is a V12, because it is basically comprised of 2 I6's next to each other, since I6's are naturally balanced. Boxer engines balance naturally too, buuut that's about it.

Yup,

I would agree. You can argue all kinds of engine design, and manufactures all day. The fact remains the I6 is the most balanced engine made. Also, because of this, they tend to have the best low-end torque. Just look at F-150’s. The I6 motor has more low-end torque then the V8 (that would be the 5.0 ltr.), same manufacturer, and bigger V8 as compaired to smaller strait 6.

On a side note, I have an 944 2.5 liter I4, and a V6 3.0 liter, SOHC Stealth. Both rated around 160-170 HP. Granted my 944 has balance shafts to counter act the “large” I4 vibration problem, but personally I enjoy the 944 more because it seems to get to the power band faster, and have better acceleration at freeway speeds. But that is my opinion. I have no real numbers on it.

[jhillyer]

Originally Posted by SaabJohan

burly, jhillyer
You're making many assumptions, for all we know the I4 could be the one with the higher displacement. Or perhaps it's the one that is turbocharged.

Maximum power output at high rpm isn't equal to poor driveability. Driveability has more to do with the power/torque curve, and notice that I wrote curve, the values themself are not that important. Then driveability for racing and daily driving differs, most manufacturers of F1 engines will probably say that their engines has good driveability, putting one of those engines in a normal car and give it to a daily driver and he will most likely not agree. A racing engine usually delivers a smooth curve in the upper part of the rpm range and the engine for the daily driver delivers a smooth curve in the lower part of the rpm range.

Most car manufacturers are trying to make cars that during daily driving can be driven with more "pedal effort" as this will reduce fuel consumption.

Nooo, the i4 is supercharged with nitrous, and the i6 in question is really two halves of a flat-6 with water injection.

The potential of turbo is not so relevant when it was not mentioned in the initial posting, and the peak power has already been given. We're not allowed to add a turbo and make 240 (b)hp out of a 175 i4, so set a mental firewall at 175. I'm hoping we can center our comments about the "difference between 175 hp I4 and 175 hp V/I6", and not so much on upgrade equipment.

I agree about your mention of rpm and drivability. Because except for solid-solid clutch engagement, higher RPM (or more working cylinders per crank moment) results in smoother power output. Lower the RPM or reduce the cylinders pumping, and we get more warble in the loaded output.

Besides, we just learned the i6 is really a diesel 13BT peripheral intake rotary with variable compression between 16:1 and 22:1, or maybe not.

[beef_bourito]

i would thikn that the I6/4 would rev higher than the v6 because the V needs to turn 2 camshafts rather than one so less loss to that.
just my sort of informed theory.

[PWMAN]

Originally Posted by beef_bourito

i would thikn that the I6/4 would rev higher than the v6 because the V needs to turn 2 camshafts rather than one so less loss to that.
just my sort of informed theory.

how are you informed??? and by who?
Most V6's are OHV, meaning 1 cam. Only if it's OHC does it have 2 cams. Besides, 90% of 4 cylinders now are DOHC, so they have 2 cams to turn also.

4 cylinders rev higher due to less recipricating mass, otherwise a V engine configuration can rev higher. Example, a 300 straight 6 ford, and a 4.3L chevy V6, the ford can rev to like 4000 RPM and the chevy V6 can rev easily to 6K.
Another example, a V4 motorcyle engine and an I4 honda. Motorcycle-9-10K easy if not more, honda-most only to 7500 but the S2000 engine to 9K(rare exception).
Once again it's only because of recipricating mass that an I4 can rev higher that a V6. Also a larger cubic in engine will generally rev higher anyway, so a V6 will more than likely be more CID.

[beef_bourito]

by sort of informed i meant from what i've heard on this forum. if you have a v engine with SOHC dont you have one cam on either side. also i thought more moving parts=more power loss. i'm not an expert, as it's probably obvious from my previous posts besides i'm only 15 so i dont have much car experience, but from what i've heard from this forum i thought an I4/6 would rev higher than a V6 because of less moving parts.

[Some1else]

Originally Posted by PWMAN

4 cylinders rev higher due to less recipricating mass, otherwise a V engine configuration can rev higher.
Another example, a V4 motorcyle engine and an I4 honda. Motorcycle-9-10K easy if not more, honda-most only to 7500 but the S2000 engine to 9K(rare exception).

Originally Posted by PWMAN

Once again it's only because of recipricating mass that an I4 can rev higher that a V6. Also a larger cubic in engine will generally rev higher anyway, so a V6 will more than likely be more CID.

Err? You're going to have to pick one. Either the "less recipricating mass", or "larger cubic in engine will generally rev higher anyway"

Sorry, not a flame!

On a side note, most street bikes red line at or above 11,000 RPM, and thus agreeing with your point, "less recipricating mass". This is one case where smaller is better!

[spooleffect]

This is the most over simplified question with the most complicated answer Ive every seen. There are WAY to many factors in determining the answer. Bore, Stroke, Rod Length, Cylinder Arrangment(ie stroke angle), Induction Type, Head Design, Cam Profile, Compression Ration, etc, etc , and etc. There are WAY to many engineering factors to take into account.

This is a horrible question.

I can't even try to answer this question with a really simple answer either. But I will try.

I-6= Will peak 175hp at a lower rpm and have a broader flatter power curve.
V-6= Will need a bit more rpm to mak the 175hp peak and will make good mid range power on the way to that number but it will not produce as much torque as the I-6.
I-4= Will need more rpm than the 6's to make the 175hp number, it will not produce lower power numbers like the 6's but the engine will do better as the rpms climb. It will have a steeper power curve than the v-6 and will not have flat curve of the I-6.

This is assuming all have equally displacment~2.5L, head design, induction, fuel characteristics, etc, and will make 175 peak horsepower. To put it simple each engine is as identicle to the others as it can be. Don't add in yeah but what if remarks. This is just a simple answer to the question

[PWMAN]

Originally Posted by Some1else

Err? You're going to have to pick one. Either the "less recipricating mass", or "larger cubic in engine will generally rev higher anyway"

Sorry, not a flame!

On a side note, most street bikes red line at or above 11,000 RPM, and thus agreeing with your point, "less recipricating mass". This is one case where smaller is better!

Thats not a contradiction. A larger CID engine will have more recipricating mass I.E. larger pistons and crank stroke.

Oh sorry I meant to say larger CID engine will NOT rev as high.

[PWMAN]

Originally Posted by Some1else

On a side note, most street bikes red line at or above 11,000 RPM, and thus agreeing with your point, "less recipricating mass". This is one case where smaller is better!

Most street bikes aren't V4's

[PWMAN]

Originally Posted by beef_bourito

if you have a v engine with SOHC dont you have one cam on either side.

Yes, thats why I specified between OHV and OHC. Most V6's are OHV, and only have 1 camshaft. yes some V6's are SOHC BUT most 4 cylinders are DOHC meaning they have 2 cams to turn also. PLUS a V6 cams are shorter and don't weigh as much(less recipricating mass) as a 4 cylinders cams.

''recipricating mass'' is the word of the day

[VQuick]

I've seen the comparisons here, and it looks like no one is really using motors of the same displacement. That's a big factor in how a motor will behave vs. another.

Since I know more about Nissans than other manufacturers, I'll use their engines as an example. All motors here are 2L.
FJ20DE(DOHC I4):147hp
SR20DE(DOHC I4):140hp-165hp
RB20DE(DOHC I6):152hp
VG20E(SOHC V6):113hp
VQ20DE(DOHC V6):168hp

Now the turbo 2L versions. There is no 2L VQ turbo.
FJ20DET(DOHC I4):187hp
SR20DET(DOHC I4):205-247hp
RB20ET(DOHC I6):144hp
RB20DET(DOHC I6):211hp
VG20ET(SOHC V6):147hp

Here's the 2.5L engines. Same order.
QR25DE(DOHC I4):175hp
RB25DE(DOHC I6):187hp
VQ25DE(DOHC V6):187hp

Now on to the 2.5L turbos. There is no QR turbo.
RB25DET(DOHC I6):276hp
VQ25DET(DOHC V6):276hp

Here's two 3Ls, both V6.
VG30DE(DOHC V6):226hp
VQ30DE(DOHC V6):190-222hp

Just for the heck of it, here's the turbo versions.
VG30DET(DOHC V6):250hp
VQ30DET(DOHC V6):276hp, but probably more, since the 2.5L turbo already produces that much. You know, because of the whole Japanese 'Gentleman's Agreement' and all.

Hope this all helps.

[PWMAN]

Could you give the RPM's those HP ratings are at? How about the torque specs?