Does anyone else find it funny that people prefer the turbo over the non turbo because it has better gas mileage? Usually turbos are preferred for the power gains over non turbos but that just doesn't ever seem to be the case with the Sonics. I'm sure a lot of this has to do with the economic problems we all have but never have I seen this big a swing of mileage over power.
Turbo power vs mpg
- Thread starter MCa23
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cmoore2004
New member
I thought the 1.8 was ridiculously slow and then drove a Cruze with the 1.4T. Night and day difference. The MPG being better was a bonus.
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RichieRocket
New member
Hi MCa23, I definitely wanted the 1.4T for the fuel economy. I'm not hot-rodding it, I have my motorcycle to go fast on. For me, the Sonic is a toy hauler and commuter.
We are used to turbos being sized big for max hp, however that means the big turbo has lag and can't provide boost at lower rpms. The 1.4T turbo was sized on the small side to minimize lag and give good boost at low rpm's for good low-end torque, but it can't build top end power as a big turbo. The 1.4T is rated at 148 ft-lbs from 1850 rpm (with automatic tranmission), from 2500 rpm with 6-spd manual...
Older turbos also had to have lower compression ratios, so they had bad efficiency when running off-boost like when cruising on the highway. Nowadays the variable valve timing can change the 'effective compression ratio' to improve off-boost efficiency.
We are used to turbos being sized big for max hp, however that means the big turbo has lag and can't provide boost at lower rpms. The 1.4T turbo was sized on the small side to minimize lag and give good boost at low rpm's for good low-end torque, but it can't build top end power as a big turbo. The 1.4T is rated at 148 ft-lbs from 1850 rpm (with automatic tranmission), from 2500 rpm with 6-spd manual...
Older turbos also had to have lower compression ratios, so they had bad efficiency when running off-boost like when cruising on the highway. Nowadays the variable valve timing can change the 'effective compression ratio' to improve off-boost efficiency.
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I got it for Both... For this application (a little pep with more focus on mpg), I think Chevy did a good job of sizing the turbo for the 1.4 engine. I was very impressed that they chose to improve torque delivery rather than just higher HP numbers that can be printed in marketing material. I originally test drove the 1.8 Sonic and thought it was adequate but didn't have much more for sprints... I had to test drive the 1.4T cruze and compare it to the 1.8 cruze to get some sort of idea of how it felt. The dealer didn't have 1.4T Sonics on the lot.
I've generally driven either v8's or i4 with turbos or superchargers with a manual transmission. Its what I'm used to and a turbo sonic was the best fit for me in this class of vehicle (my first sub-compact).
PS> this isn't the first time that turbo's were specifically used for efficiency. I'm happy that turbo's have become more popular the last 10 years or so.
I've generally driven either v8's or i4 with turbos or superchargers with a manual transmission. Its what I'm used to and a turbo sonic was the best fit for me in this class of vehicle (my first sub-compact).
PS> this isn't the first time that turbo's were specifically used for efficiency. I'm happy that turbo's have become more popular the last 10 years or so.
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I may be a little biased as I own a 1.4 turbo, but if you are on the fence the turbo is definitely the way to go. Chances are, the car will be financed anyway, so the $700 premium will hardly be noticed up front, and it will pay for itself at the pump before the car is paid off anyway. This little 1.4 is a mini-torque-monster. It has loads of usable torque across a wide powerband, and I think in most daily driving situations you are going to be in the lower end of the powerband anyway, which is where the 1.4 really shines over the 1.8. I bought mine for the fuel economy, and I dont see how you could be in the market for a subcompact if fuel economy isn't one of your top priorities anyway. I am very pleased with mine, and I'm sure my smile will only get wider when my trifecta tune gets in (another reason why I bought the Sonic, and the turbo in particular). I am under no illusion that my Sonic is a racecar, and I don't treat it like one, but it is a real joy to drive. If power and mpg arent enough, the 1.4 is built in the USA, while the 1.8 is built in Korea (something I did not realize until I was looking at window stickers on the lot). I'm sure plenty of owners are happy with their 1.8's, but it was never a contender for me.
LS1notFOUND
New member
the turbo happens to be a win/win....however the fuel economoy boost (highway mpg anyway) is most likely due to the 6 speed, a 6 speed manual with the 1.8L would've nice to drop the RPMs from something less than 3000 at upper cruising speeds....however it doesn't have the power to enjoy that OD gear very well
Aldakoopa
New member
LS1notFOUND
New member
actually thinking about it, while cruising the 1.8 might have more down low as the 1.4 is isnt in boost at that point. I should note I have yet to find myself in a situation where downshifting is required to maintain speed while on the highway...but this is pretty flat this way in NC, wait till i venture through the backwoods of upstate NY later this month.
I do like that the 1.4L is pretty much the unique feature to the US version, and if there was a turbo on the lot when I bought mine I would have bought it.
I do like that the 1.4L is pretty much the unique feature to the US version, and if there was a turbo on the lot when I bought mine I would have bought it.
I think the 1.4 is pretty close to peak torque at cruise rpms (70 mph @ ~2200). I may have a different perception of what constitutes a hill, as I live in West Virginia, but i'm not surprised that you haven't needed to downshift, as a five speed is already downshifted as compared to the six.
RichieRocket
New member
Hey River_Rat, here's some info to add to the discussion:
I put together a speed vs. rpm plot for each gear ratio, so for example
70 mph in 6th gear = 2100rpm, in 5th = 2500rpm, in 4th = 3250rpm
http://www.sonicownersforum.com/forum/t640/
Comparing the 1.8L 5-spd to 1.4T 6-spd, here's a plot I made of the overall gear ratios (including final drive ratio)
http://www.sonicownersforum.com/forum/t170/
Unfortunately, the 1.4T with manual transmission does not get to peak torque until 2500 rpm. the 1.4T with automatic gets peak torque at 1850 rpm.
http://www.sonicownersforum.com/forum/t1488/
I stumbled across this when looking at gmpowertrain website: Powertrain Overview
I also made a power vs. road speed for each gear, see post #23
http://www.sonicownersforum.com/forum/t715-3/
Attachments
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Sonic_rpm_vs_speed_reverse.jpg
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Thanks for adding all of this data to the discussion RichieRocket. I actually had your graphs in mind when making an earlier post, but it's kind of a pain to link to them all and etc. from a phone on a coffee break. With your help, I may end up eating my words before this is all said and done, which is why I put the qualifier "pretty close" in my previous post 
. Looking at your hill climb graph and calculating for wheel torque @2100 rpm, it appears that the 1.4 is only generating right at 100 ft-lbs, not quite as much as I had supposed. I can't seem to find actual dyno numbers for the 1.8 to do an apples-to-apples comparison, but, for now, LS1notFOUND seems to be on to something (so long as we keep it at 2100 rpm).
. Looking at your hill climb graph and calculating for wheel torque @2100 rpm, it appears that the 1.4 is only generating right at 100 ft-lbs, not quite as much as I had supposed. I can't seem to find actual dyno numbers for the 1.8 to do an apples-to-apples comparison, but, for now, LS1notFOUND seems to be on to something (so long as we keep it at 2100 rpm).I'm really really happy with the 1.4 stick shift, And I'm in it for the Mpg, but is everyone happy with the 1.4 using a/c around town? I find it a little baulky if I short shift for mpg. If I rev higher there is no prob. Thoughts? (yeah I can hear you saying, if you into mph why are you using air in town) It gets hot and humid in Ks.
I definitely notice a loss of power while using the a/c. I don't normally use it while cruising around town though. For me, I usually notice the power drain while accelerating on an on-ramp. I'm not really used to a car with good a/c nor am I used to driving a four-cylinder. Most of my experience is with v8's and crappy a/c, so this is new territory for me. Not sure what the implications for fuel economy might be, but I suspect that with as much as it bogs down the engine at low rpm's, it would have a fairly significant impact on mpg.
RichieRocket
New member
Thanks for adding all of this data to the discussion RichieRocket. I actually had your graphs in mind when making an earlier post, but it's kind of a pain to link to them all and etc. from a phone on a coffee break. With your help, I may end up eating my words before this is all said and done, which is why I put the qualifier "pretty close" in my previous post
Yeah, those hp numbers are at-the-wheel, don't know if anyone has the 1.8L dyno plots. Looking at the Trifesta dyno baseline plot (no tune), there is something funny going on below 3000 rpm. The hp ramps up smoothly, it seems like they are rolling onto the throttle until about 2700 rpm. The numbers below 2700 rpm are not at full throttle, so the 100 ft-lbs you calculated is not max torque at 2100 rpms. I'll have to redo the chart holding torque constant down to 2500rpm, then tapering down from there.
http://www.trifectaperformance.com/DynoSheets/2011ChevyCruzeLUJDyno.jpg
To compare the 1.4T to 1.8NA in top gear, I was going to use the hp plots from the gmpowertrain website and debit the crankshaft hp by 15% to get at-the-wheel estimated power. But didn't get to it yet.
