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Discussion Starter · #1 · (Edited)
so i saw a commercial for the 2009 suzuki sx4 just now. it showed it with a cape and a lightning bolt sticker on the side. it said it was better and thousands less than the mini, and that not only does the sport trim level start at $16,434, but it comes standard with navigation. i was thinking let me just check the engine specs first. i go to the website and see it comes with the same size engine as the si, but only 143 hp! i'm like ok maybe it's really light, let me check the 0-60. it's over 10 seconds! how the hell can you insinuate the car's a mini killer when it takes over 10 seconds to hit 60, and only has 143 hp?

there is one odd spec though, the 143 hp sx4 has only 3 less torque than the si. and it's odd how it has 136 torque at 3500 rpms, and the si has 139 torque at 6100 rpms, but it's the same size engine. why is it like that? i know there's a lot that goes into making the torque curve what it is, but that's a huge difference. what are the main factors that make the torque curve what it is, given the same size engine? the sx4 can go to at least 6000 rpms, so it's not like it's peak torque is at 3500 because it doesn't rev very high. and yes, i know, peak torque is usually down low or in the middle, to which i would say, then why is the si at 6100?
 

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Discussion Starter · #3 ·
i suppose the answer could be that the si has a bore/stroke of 86/86, and the sx4 is 84/90, which means it has longer strokes, which creates more torque down low. but is 86/86 really that much different than 84/90?
 

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there is one funny spec though, the 143 hp sx4 only has 3 less torque than the si. and it's odd how it has 136 torque at 3500 rpms, and the si has 139 torque at 6100 rpms, but it's the same size engine. why is it like that?
Because

(Torque x RPM) / 5,252 = Horsepower

Higher-revving N/A engines by nature don't have high torque. To have more torque, you'd have to increase displacement or have forced induction. If you plug in the Si's numbers the torque value has to be low, since the RPM is very high.
 

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so i saw a commercial for the 2009 suzuki sx4 just now. it showed it with a cape and a lightning bolt sticker on the side. it said it was better than the mini, and that not only does the sport trim level start at $16,434, but it comes standard with navigation. they said it was thousands less than the mini (understatement).

i was confused how a car over $10k less than the mini could rival it. i was thinking let me just check the engine specs first. i go to the website and see it comes with the same size engine as the si, but only 143 hp! i'm like ok maybe it's really light, let me check the 0-60. it's over 10 seconds! how the hell can you insinuate the car's a mini killer when it takes over 10 seconds to hit 60, and only has 143 hp?

there is one funny spec though, the 143 hp sx4 only has 3 less torque than the si. and it's odd how it has 136 torque at 3500 rpms, and the si has 139 torque at 6100 rpms, but it's the same size engine. why is it like that? i know there's a lot that goes into making the torque curve what it is, but that's a huge difference. what are the main factors that make the torque curve what it is, given the same size engine? the sx4 can go to at least 6000 rpms, so it's not like it's peak torque is at 3500 because it doesn't rev very high. and yes, i know, peak torque is usually down low or in the middle, to which i would say, then why is the si at 6100?
if i'm not mistaken its got a much longer stroke than the si. shorter stroke length = more useable rpm range = less torque. the sx4 prob redlines at 6000rpm. no diff than my srt. its got a 4.5in stroke... and to think there are guys that put stroker cranks in these things to make them 2.6's.
 

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no one can rival the N/A hp/liter ratio of honda, our cars are making like 100 hp per liter lol
No one can rival it?

Nissan would disagree there. Until the Japanese-spec S2000 they had the highest N/A horsepower/liter engine on the planet. They produced a 1.6 liter engine (SR16VE N1) that made 197hp which means over 132.1 hp/liter. The JDM-spec S2000 barely beats that out and that car came out a few years afterwards.

There are cars other than Honda that have achieved 100hp/liter, and that's not even getting into Mazda's rotary engine which is the hp/liter king.
 

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There's a lot of variables that influence the torque curve. You've got bore/stroke ratio and manifold shape like others have said. You've also got the chamber shape, valve lift and intake/exhaust valve overlap, etc...

In the design of the SX4 engine, they probably weren't as concerned with peak hp numbers as everyday driveability. They probably figured that most people that drove that car would spend most of the time below 4000 rpms, and thus why they decided to put peak torque around 3600 rpms.

143 hp out of a 2.0 really isn't that bad. The old Sentra SE-R only had 140 hp out of 2.0 liters.
 

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In the design of the SX4 engine, they probably weren't as concerned with peak hp numbers as everyday driveability. They probably figured that most people that drove that car would spend most of the time below 4000 rpms, and thus why they decided to put peak torque around 3600 rpms.
Also there is a design for manufacturability. They probably realized they could cut costs designing an engine the way they did while still hitting their target market.
 

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Discussion Starter · #19 ·
Because

(Torque x RPM) / 5,252 = Horsepower

Higher-revving N/A engines by nature don't have high torque. To have more torque, you'd have to increase displacement or have forced induction. If you plug in the Si's numbers the torque value has to be low, since the RPM is very high.
well, look at any other engine that's around the same size, but with a sub 7k redline, and you'll see it still has 135+ torque. the si is where i learned exactly what people are talking about when they say hp is a poor way to define speed/power. i found out through the si that alls it takes is a high redline and you automatically have a good amount of hp, but that's a horrible way to get a lot of hp, because that means you have nothing down low. the problem is, i don't think they really have high-revving high-torque engines, because high-torque requires longer pistons, which is bad if you want a high redline. at the opposite end though, an engine with a 4k redline and lots of torque would require like 10 gears.

longer stroke + smaller bore = lower redline and peak torque at a lower rpm.

Also intake manifold design dictates even further where peak torque is at.
if i'm not mistaken its got a much longer stroke than the si. shorter stroke length = more useable rpm range = less torque. the sx4 prob redlines at 6000rpm. no diff than my srt. its got a 4.5in stroke... and to think there are guys that put stroker cranks in these things to make them 2.6's.
the si has a bore/stroke of 86/86, and the sx4 is 84/90, but is 86/86 really that much different than 84/90?

I'm thinking they might be talking about the base Mini. AFAIK, it's nothing great in performance. Probably close to an R18 Civic considering the Cooper S is close to Si performance.
the base cooper still blows the sx4 away by 2 or 3 seconds in the 0-60, and it only has 118 hp. the cooper s has the same engine, but it's turbocharged. how a turbocharged engine in a sporty car only has 172 hp, i don't know. i know the mini probably only weighs a ton, but still, why not get a 200 hp engine in there?

143 hp out of a 2.0 really isn't that bad. The old Sentra SE-R only had 140 hp out of 2.0 liters.
i must be mistaken, because it sounds like you're saying that 143 isn't bad, but 140 is.
 

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well, look at any other engine that's around the same size, but with a sub 7k redline, and you'll see it still has 135+ torque. the si is where i learned exactly what people are talking about when they say hp is a poor way to define speed/power.
Torque also doesn't tell the whole story though. If torque was all that mattered, the SX4 should be just as fast the Si. It isn't.
 
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