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Old 05-22-2002, 05:12 PM   #1
FuJi K
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Lightbulb Subaru's high torque numbers.

Does anyone know why subarus have a good amount of torque produced from their engines? It has like the same amount as a 2.5L V6 if not higher.

I know why but i just want your thoughts. I'll answer back a bit later after a few replies.

Thanks!
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Old 05-22-2002, 05:18 PM   #2
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2.5L uses diesel



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Old 05-22-2002, 05:31 PM   #3
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Sorry, had to do it Maybe it's because EJ25 has a large bore compared to the stroke?

Route to guess: Much torque but a only a decent amount of power. The torque is applied on a shorter lever than with bigger stroke engines - the force goes on a shorter curve than with the longer stroked engines. On the other hand power is proportional to work which is proportional to the distance where the force had been applied. At the same RPM range less work is done therefore.




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Old 05-22-2002, 05:31 PM   #4
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Its just displacement mostly. A 2.5L 6 will have more reciprocating mass and taht'll eat away at torque. Honstly, any 6 less than 3.0L is really only a 6 for smoothness, and would be bettersuited as a 4 for performance. IMO at least.

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Old 05-22-2002, 08:46 PM   #5
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i dont really see whats so special about subaru's torque numbers.

1. subaru, 2.5L 166 lbs-ft
2. Nissan, 2.5L 180 lbs-ft
3. Mazda, 2.5L 160 lbs-ft
4. BMW 3-series, 2.5L 175 lbs-ft
5. BMW, 3-series, 2.5L 181 lbs-ft
5. jaguar, 2.5L 180 lbs-ft
6. land rover, 2.5L 177 lbs-ft
7. BMW m3, 2.5L 174 lbs-ft
8. mitsubishi, 2.5L 163 lbs-ft
9. honda, 2.4L 162 lbs-ft

Last edited by SubyRacer; 05-22-2002 at 09:01 PM.
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Old 05-22-2002, 10:36 PM   #6
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Quote:
Originally posted by SubyRacer
i dont really see whats so special about subaru's torque numbers.

1. subaru, 2.5L 166 lbs-ft
2. Nissan, 2.5L 180 lbs-ft
3. Mazda, 2.5L 160 lbs-ft
4. BMW 3-series, 2.5L 175 lbs-ft
5. BMW, 3-series, 2.5L 181 lbs-ft
5. jaguar, 2.5L 180 lbs-ft
6. land rover, 2.5L 177 lbs-ft
7. BMW m3, 2.5L 174 lbs-ft
8. mitsubishi, 2.5L 163 lbs-ft
9. honda, 2.4L 162 lbs-ft
Ok, I think what he might be saying, also has to do with when the torque is on tap. IIRC the RS gets a buttload of torque at just 2.5k rpms, hitting peak at 4k (its VERY broad), compared to other 2.5L motors that the torque comes in later on.

What honda has the 2.4L?

-justin
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Old 05-22-2002, 10:52 PM   #7
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the new CRV.
and still BMW's 2.5L reach peak at around 3500rpm, and dont drop off nearly as hard as approaching redline as the EJ25. and the dynos ive seen of the new SE-R putting out 150lbs-ft at the wheels at just 2500rpms! sure the RS has a lot of low end punch for a 4 banger, but its nothing special really.

Last edited by SubyRacer; 05-22-2002 at 11:00 PM.
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Old 05-22-2002, 11:42 PM   #8
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oh yea i forgot to mention, our nice low end torque. That's what i meant, sorry.
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Old 05-23-2002, 01:54 PM   #9
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As for those engines with higher torque numbers, I believe almost all of them use some sort of variable valve timing and lift to achieve that, which the EJ25 doesn't have.
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Old 05-23-2002, 02:11 PM   #10
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ok now for my input.

IMO, the reason our Subarus have a nice low end torque is because of the longer intake manifolds that we have on the H4's. Am i right? And plus our displacement.

But i really think that Subaru's nice low-end torques are acheived from the longer intake manifold tubes.
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Old 05-23-2002, 03:55 PM   #11
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has anyone ever heard the term "there's no replacement for displacement"? I believe the whole reason the 2.5RS is making so much torque is just because of the displacement. Feel free to disagree with me on this and argue my point if there's a lot more to it than just that. But you do have to admit that the displacement plays a big part in that role.
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Old 05-23-2002, 05:52 PM   #12
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As a general rule, Torque is a result of leverage. Longer Stroke = Leverage. The 2.5L of the EJ25 is the result of both good bore size, and a fairly long stroke.

Think about a diesel engine. They generally have large torque numbers. Most of them have a very long stroke compared to the bore size (under square). This is the reason for the torque.

Think about it this way. You have a regular 3/8 drive socket trying to undo a bolt. But you can't budge it. You can't get enough torque on the short 6" handle. So you put a breaker bar on the socket. Now you have 2 feet of leverage. You are not any stronger... But the leverage advantage of the breaker bar has increased the torque.

Simple really!
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Old 05-23-2002, 07:41 PM   #13
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The Nissan 2.5 in my G/f's spec-v says it puts out 180lbs of torque but it is so sharp it's hard to stay in the power band. Her car feel dead on the bottom and dead up top. 3k-5k is where all the power is made.
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Old 05-23-2002, 08:39 PM   #14
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Quote:
What honda has the 2.4L?
pretty sure thats used in the CRV
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Old 05-24-2002, 03:08 AM   #15
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Quote:
Originally posted by nitrohuffer
The Nissan 2.5 in my G/f's spec-v says it puts out 180lbs of torque but it is so sharp it's hard to stay in the power band. Her car feel dead on the bottom and dead up top. 3k-5k is where all the power is made.
Well, I know for fact that the majority of the power band for an EJ25 is around 3K-5.5K
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Old 05-26-2002, 06:16 PM   #16
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Probably a dumb question but, could it have anything to do with the horizontal configuration? Because Porsches also make a good amount of torque. Aren't the smaller in displacement compared to others in that class?
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Old 05-26-2002, 09:24 PM   #17
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The fact that the EJ25 is a boxer has nothing directly to do with it's torque numbers. It really is a simple matter of size. Oh yeah, and compression ratio has a very big impact also.

Here is an iteresting fact ya:
Porsche 911 GT2 3.6L Flat 6 twin turbo
Bore x Stroke = 100x76.4mm
6750 RPM redline

Subaru 2.5RS 2.5L Flat 4
Bore x Stroke = 99.5x79mm
6500 RPM Redline

Asside from 2 more pistons, the turbos oh yeah.. 300 more HP, they both have very similar basic dimensions.
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Old 05-27-2002, 02:03 AM   #18
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I wonder if anybody would take the time to do the math: If the 2.5 engine was actually a 3.6 and twin turboed but the horse power per liter was still paralell to what it was at 2.5 liters, what would we be looking at? My head hurts.....
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Old 05-27-2002, 11:50 AM   #19
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I thought that it was due to us having our special "trunk monkey"!!!
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Old 05-27-2002, 12:07 PM   #20
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Quote:
Originally posted by watcher in the sky
I wonder if anybody would take the time to do the math: If the 2.5 engine was actually a 3.6 and twin turboed but the horse power per liter was still paralell to what it was at 2.5 liters, what would we be looking at? My head hurts.....
If the 3.4l made 365 (300 more)
and the 2.5l made the same hp/l
it would make 268hp
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Old 05-27-2002, 01:13 PM   #21
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Well, a 2.5 at 165hp, is roughly 66hp/liter.
at 3.6, it would have to be about 237.6 to stay at 66hp/liter. Then if you twin turbo, I would think that you'd be pushing closer to 300hp, possibly more.

Hmmm...
I wonder about a 3.0 H6 transplant......mmmm turbos...
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Old 05-27-2002, 03:23 PM   #22
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I'm going to replace my 2.5L with a pair of Hamsters on steroids.
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Old 05-27-2002, 07:55 PM   #23
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That, my friend, is pure genious......
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Old 05-28-2002, 02:14 AM   #24
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Actually, I'd say it really has to do with the cam profile and how much air the head can flow at a given valve lift.

I'd say that Scoobies have a short duration/medium lift camshaft with a fairly aggressive ramp profile. But the biggest factor is that the valve diameters are probably fairly small for the engine size. Thus, intake gas velocity shoots up quickly in the lower rev range, atomizing fuel which increases combustion efficiency. This is turn increases the big factor, volumetric efficiency. Because of these low flowing ports, the flow capabilities of the head are quickly reached, way before redline. This is is why power dies off very abruptly at high RPMs, and a larger camshaft doesn't help keep the torque up as much as one would think(without headwork).

The stroke also isn't that long on the EJ25. The B18B1 found in the non-VTEC Integras has an 81mm bore and an 89mm stroke. Although this engine doesn't even come close to waking up until 3.5k RPM, and really only pulls "hard" from 4k-6k RPM with a 6800 RPM redline. This powerband and the 77.7 HP/L are mainly due to the excellent flowing head(which can easily support 300-400WHP with forced induction and not be a major bottleneck).

The configuration of a boxer engine does contribute some to the low-end torque of the EJ25, although it is really a secondary contributor at best. This engine configuration reduces bearing loads on almost every stroke, and those small bits add up, especially in the higher RPM ranges. Engine harmonics are also reduced, which can rob some HP. Case in point, some Honda cranks can flex enough at >9-9.5k RPM that the flywheels can actually contact the block!!! This happens mainly to the non-VTEC engines with larger bearing clearances and no crank girdles. And is a really nice way of creating a yummy hunk of molten aluminium and mild steel.
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