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First Drive: Chevrolet Cruze 1.7 VCDi (0-62 in 9.4 sec.)

9970 Views 33 Replies 17 Participants Last post by  Skraeling
First Drive: Chevrolet Cruze 1.7 VCDi ( UK Hatch: 0-62 in 9.4 sec.)

IN AN effort to keep pace with the ever-improving engine efficiency in rival compact hatchbacks, Chevrolet has developed a 1.7-litre diesel for its Cruze......But fortunately it’s not just tuned for economy at the cost of driveability. When brand new it feels noticeably restricted and needs at least 1,000 miles to loosen up enough to show its full talent, but at that point it pulls strongly through all six gears thanks to a healthy 128bhp and 221lb.ft of torque.The Cruze itself isn’t a heavy car and feels livelier than its 0-62mph time of 9.4 seconds suggests once it’s got some miles under its belt. Well-chosen gearing is partly to thank, and even top gear isn’t too long to overwhelm the engine. The car sits at 2,000rpm at 70mph, which isn’t as low as it could be for outright fuel economy but it’s tractable without needing to change down....

(Keep in mind this was the hatchback version tested in UK)

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First Drive: Chevrolet Cruze 1.7 VCDi - Yahoo! Cars
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Since I am in the engineering field, I figure I should probably throw in my 2 cents to this debate.

Torque is measured in lb-ft (or N-m for metric). So picture this: if an engine produced 100 lb-ft of torque and had an outer wheel diameter of 12 inches, then the force that the wheels apply to the pavement would be 100 lbs. If the outer wheel diameter is 24 inches, then the force would be 50 lbs, and so on. Torque is a measure of how much force the engine can apply to the tires.
more torque = more force = higher acceleration.

Horsepower is a measure of the power of the engine. Power is work over time. So an engine with more horsepower can produce more work in the same amount of time than an engine with less HP. This does not really affect acceleration too much, but it has everything to do with speed. At highers speeds, aerodynamic drag becomes a big factor in performance. An engine with high brake horsepower (bhp) has the ability to produce more work in order to counter these increased aerodynamic forces, meaning the car can go faster.
more BHP = more work = higher top speed.

My easy way of remembering this is:

Torque overcomes inertia, horsepower overcomes drag.
 

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It's also geared to let the engine wind fast. When the S2000 first came out, reviewers complained that they had to rev it to 6-7k to get any kind of acceleration out of it. Just even off a stop light.
Yeah, I drove it and a Z3 (ex-girlfriend's parents cars). The Z3 felt a LOT quicker, even though the S2000 would kill it in a race. Plus, I was scared to rev the S2000 to 7000 RPM with her dad in the car. :D

Honestly, I'd much prefer torque for everyday driving. Probably why I bought a Cruze instead of a car with more HP. Though I would prefer more "move-it" motivation on the highway. Hard to have both with a small turbo engine - it's usually either one or the other.
 

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Very simplistic way I have defined Horsepower: HP is the speed at which the available torque is applied.

Thats why as long as you have a high HP number the car will be fast, it can apply its real power(torque)quicker.

Diesels have tons of torque & little horsepower thats why they are usually slower accelerating. Once you increase the horsepower of a diesel, its a whole different machine. There are many 10-13second 1/4 mile duramax diesel trucks out there with mods done. Lowest output duramax is 300HP/520TQ. The newest high output one is 395HP/765TQ, stock is beginning to be fast.
 

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you cant compare a diesel to a gasser in terms of torque. My 2500hd is relatively quick, but will outrun a diesel with a similar peak power output. These boosted diesels have a totally different power output than a gasser...8.1L of gas motor with 600 ft lbs will walk all over 600 ft lbs of diesel. This somewhat applies to gassers too, esp since our boost is a product of exhaust gas heat. Its just not AS noticable, but its still there.

Keep in mind that a duramax running without boost would likely be in the 250 ft lb range...which is why, until load and exhaust heat build, they are slow as ****. 250 lbs pushing 7000+? eeek...
 

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8.1L of gas motor with 600 ft lbs will walk all over 600 ft lbs of diesel.
Mind you an 8.1 would have to be pretty tuned up to be putting out those torque numbers (600ish). You wouldn't really be comparing apples to apples then now would ya?. Take for instance, a stock 8.1L (340hp/455tq) vs a stock LBZ (360hp/650tq). Hard to get a 30% torque increase out of a gasser without some boost :p
 

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BlackBelt2025 said:
Since I am in the engineering field, I figure I should probably throw in my 2 cents to this debate.
I'm all ears!

BlackBelt2025 said:
Torque is measured in lb-ft (or N-m for metric). So picture this: if an engine produced 100 lb-ft of torque and had an outer wheel diameter of 12 inches, then the force that the wheels apply to the pavement would be 100 lbs. If the outer wheel diameter is 24 inches, then the force would be 50 lbs, and so on. Torque is a measure of how much force the engine can apply to the tires.
more torque = more force = higher acceleration.
Not bad so far, but no mention of the car's gearing which multiplies the engine's torque up to 20x or more depending on the car.

BlackBelt2025 said:
Horsepower is a measure of the power of the engine. Power is work over time. So an engine with more horsepower can produce more work in the same amount of time than an engine with less HP. This does not really affect acceleration too much, but it has everything to do with speed. At highers speeds, aerodynamic drag becomes a big factor in performance. An engine with high brake horsepower (bhp) has the ability to produce more work in order to counter these increased aerodynamic forces, meaning the car can go faster.
more BHP = more work = higher top speed.
WHAT? Did you just say power doesn't affect acceleration "too much", but has everything to do with speed? ARE YOU SERIOUS? Sorry dude... you post here claiming to be some sore of Subject Matter Expert and then spew this stuff? I hope you brought a flame suit 'cause you're about to get BURNED.

Power has EVERYTHING to do with acceleration AND speed. Torque has EVERYTHING to do with acceleration AND speed. Power and torque are intertwined, relative and dependant on each other in a car's engine. YOU DON"T GET ONE WITHOUT THE OTHER. If you want more power output you either need to make more torque, make the same torque at a higher engine speed, or some combination of the two.

BTW, torque is measured, horsepower is not. Horsepower is calculated based on the measured torque output and the known engine speed. A horsepower rating is nothing more than a convenient number allowing people to quickly compare the MAXIMUM OUTPUT of two different engines.

WRT turbodiesel engines, I don't care if it makes ONE MILLION ft-lbs of torque, if it's a 200 Hp engine it's a 200 Hp engine and will only do 200 Hp worth of work, whether it's accelerating a vehicle, turning a generator, pumping water out of a mine or turning the soft serve mixer at DQ.

What nobody here is talking about is the SHAPE of the TORQUE CURVE. The shape of the curve can and will have an affect on the AVERAGE POWER OUTPUT when the VEHICLE GEARING is taken into account. When we accelerate (through the 1/4 mile for example) we need to change gears if we want a good launch and to still be accelerating through the traps at the end. Cars usually redline (cut off) after their peak power has been reached. Why? So that when you shift gears the engine speed doesn't drop too far away from the POWER PEAK. Operating the engine in the meatiest part of the power curve (just before and after the power peak) keeps the engine operating at it's highest AVERAGE POWER OUTPUT.

A small power dense engine (read: small, high reving, variable cam timing, etc.) tends to have limited torque but caries that torque high up into the RPM range. This results in a relatively flat torque curve and a corespondingly straight line power curve with a fairly sharp "peak". The sharper this peak the greater the power drop when shifting into the next gear for a given % of RPM loss (gear spacing). This is why extremely tight gear spacing is used on many race cars; it helps them keep their average power up during gear changes.

A larger less power dense engine of the same peak power has a more traditional torque curve with a peak in the middle and a gentle roll of on either side. This results in a much broader power curve around its peak and keeps average power output higher during gear changes. For a given overall engine/vehicle speed ratio (both engines redline at the same vehicle speed in the same gear), it will also feel quicker due to the "hump" in the middle of the torque curve. If the vehicle weight is the same between both cars, the one with the larger engine will accelerate faster. If they both have the same aero drag and are optimally geared to redline at top speed, top speed will be the same (at terminal velocity there is no acceleration and engine RPM is held steady at the power peak, which is the same for both cars).

Another thing hurting the small high reving engine is inertia. To help overcome the lower torque output of the smaller engine, super short gearing is used in the lower gears. This means that the rate of engine acceleration is quite high and the inertia of the crankshaft, flywheel and cluth assemblies will limit the car's acceleration in lower gears. Sometimes this inertial effect is so high that, by the seat of the pants anyway, the car will appear to accelerate just as hard in 2nd gear as it does in 1st. Lower inertia parts will help this situation, but less inertia can only go so far before it starts costing big $$$.

I've only just scratched the surface here... The reason most forum posters can't get this information right is they A) usually don't fully understand the topic and B) don't have the time or patience to go through it in sufficient detail. Both of which are reasons that most people shouldn't bother "trying" to explain it in the first place!!!

It's too bad you're getting the brunt of this frustration, but of all the garbage posted in this thread (there's a lot of it) you're the only one who claimed to be some sort of "professional" before misleading and confusing people.

If anything I've written here doesn't look right to anyone, it's either because I have not explained it clearly or you are reading it wrong. This is all based on physics, not my opinions.

BlackBelt2025 said:
My easy way of remembering this is:

Torque overcomes inertia, horsepower overcomes drag.
Icing on the cake! LOL!
 

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I figured some smart @$$ would make that argument :) , that's why I wrote it the way I did:

Blue Angel said:
Power and torque are intertwined, relative and dependant on each other in a car's engine. YOU DON"T GET ONE WITHOUT THE OTHER.
"in a car's engine"

I'll one-up you and say that there's residual torque left in pretty much any fastener on the car without even putting a wrench on it! :)
 

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I have. LAAAAAAAAAAAAAAGGGGGGGGGG...unless you're driving it hard like it's meant to be driven I suppose. Hard for me to drive around town above 3000+ RPM though; I'd just feel like a douche trying to attract attention to my loud car.
with a bigger turbo comes bigger lag, nature of the beast. And yeah i could never drive it like I stole it around town either. Though you dont need to heh.

with no exhaust my wrx was as quiet as the cruze... made me sad. They sound really nice too.
 

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Which goes back to what I was saying...can't have both low end an high end power with a small turbo motor. Unless you use an innovative setup like Ford/BMW with essentially a low and high pressure turbo in one!


Sent from my Autoguide iPhone app
 
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