Cruising RPM.

[tainopayute]

I need some advice here. I own a 2013 Chevy Sonic RS. I mostly drive it on the Highway. My average RPM range is about 3,100 at 70 mph. At first I thought that that was normal for this little 1.4, but after driving a Chevy Cruze with the same engine, I noticed that the RPM was 2,100 at 70 mph. That's when I started to worry. So, I did some Internet research and read in various websites that the cruising RPM in the Chevy Sonic 1.4 with a manual transmission should be between 2,100 to 2,500 RPM's when driving at 70 mph. That leaves me with the question, why are my RPM's at 3,100 when I'm driving at 70 mph? And how can I fix what ever it is that is wrong with my Sonic? Can someone please help me with some good information?

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[Rbrown1677]

I believe the RS has a different ratio then the rest. I could be wrong tho


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[Rowdy_Sonic_RS]

It does. He it had different gear ratios in the transmission to give it more torque.


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[Natesriv]

Yeah 2k at 70 hence my 40 mpg

 

[Stew]

Yeah 2k at 70 hence my 40 mpg

Right there with ya! :banana:

 

[tainopayute]

I believe the RS has a different ratio then the rest. I could be wrong tho


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Yeah, that's what I thought but I just wasn't sure. But what threw me off was what I read on the Internet. Here's what I read...
http://www.sonicownersforum.com/forum/general-discussion/170-1-4t-highway-cruise-rpm.html

http://www.edmunds.com/chevrolet/so...est/2012-chevy-sonic-ltz-its-a-six-speed.html

http://m.caranddriver.com/reviews/2012-chevrolet-sonic-ltz-road-test-reviews

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[Rbrown1677]

Yea looks like they did all this with an LTZ that has the differ t ration then the RS. Plus the first one really didn't say or specify which trim level it was.


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[Dogz]

Try cruising at 160kph then worry about the rpm's

 

[tainopayute]

Try cruising at 160kph then worry about the rpm's ����

Try cruising at 99 mph? Can you really cruise at 99 mph without overheating this little engine or worse, blowing it up?

I have hit 99 mph a few times but I didn't try to keep it there for too long because it felt a little unstable and also, I want to get a lot of years out of this little engine before having to do a rebuilt.

 

[carsNskis]

Normal for the RS per above comments.

I drove an extended stretch of Northern Wyoming above 90 (a good 20 minutes worth). Deserted roads, good radar detector and a Golf R leading the chase = lots of cardio. Carried another 250 miles after that run without a hiccup.

Car did fine other than killing my average mpg figure (I was averaging 41 after leaving Colorado, 26 after the high speed run).

I like the close ratio gearing the RS has for city driving, but always feels like it should have a 7th for true highway cruising and mpg. I've thought many times about trying to find someone with a lower trim who wants to swap trans...



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[Dogz]

Try cruising at 99 mph? Can you really cruise at 99 mph without overheating this little engine or worse, blowing it up?

I live out in the middle of nowhere & travel to work & back on country back roads with no traffic. The only things I have to worry about are sheep & kangaroos.
& ducks, I hit a big duck at high speed on the way to work. When I got to work it took me almost 30 minutes to get the duck out of the front grill which is now smashed.
High speed cruising on almost 45C days really puts the car to the test. Engine temp only goes up 2 degrees on my ultraguage, a taller overdrive would be nice though.

 

[The Champ]

I like the close ratio gearing the RS has for city driving, but always feels like it should have a 7th for true highway cruising and mpg. I've thought many times about trying to find someone with a lower trim who wants to swap trans...

Actually, the manual tranny RS is in overdrive in both 5th and 6th gears. 5th gear is .88 and 6th is .74. 1st gear is 4.27, 2nd is 2.35, 3rd is 1.48 and 4th is 1.07.

The automatic is actually a close ratio in comparison - 4.58, 2.96, 1.91, 1.45, 1.00 and .75.

It's the differential ratio of 4.176 is what's making the engine rev so high.

 

[Dogz]

Has anyone here changed the diff ratio in their RS?

 

[tainopayute]

Normal for the RS per above comments.

I drove an extended stretch of Northern Wyoming above 90 (a good 20 minutes worth). Deserted roads, good radar detector and a Golf R leading the chase = lots of cardio. Carried another 250 miles after that run without a hiccup.

Car did fine other than killing my average mpg figure (I was averaging 41 after leaving Colorado, 26 after the high speed run).

I like the close ratio gearing the RS has for city driving, but always feels like it should have a 7th for true highway cruising and mpg. I've thought many times about trying to find someone with a lower trim who wants to swap trans...



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I agree with you, a seventh gear would solve the problem with highway cruising in the RS...

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[tainopayute]

I live out in the middle of nowhere & travel to work & back on country back roads with no traffic. The only things I have to worry about are sheep & kangaroos.
& ducks, I hit a big duck at high speed on the way to work. When I got to work it took me almost 30 minutes to get the duck out of the front grill which is now smashed.
High speed cruising on almost 45C days really puts the car to the test. Engine temp only goes up 2 degrees on my ultraguage, a taller overdrive would be nice though.

Man that sucks that you smashed your bumper after hitting a duck but at least you didn't smash your entire car by hitting a kangaroo or a sheep.

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[ScarabEpic22]

Has anyone here changed the diff ratio in their RS?

Not sure, I dont know of anyone but then again I don't pay enough attention admittedly.

I agree with you, a seventh gear would solve the problem with highway cruising in the RS...

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Or just change the last 2 gears to something higher (lower numerically), not sure if possible with the trans as I haven't ripped one apart yet. Would love to have the 6th gear as 5th and then go higher for 6th. Get a cruising gear and still keep the sporty feeling in 1-4.

 

[tainopayute]

What we need is a 7 speed transmission. Back in the early 2000's a 6 speed manual transmission was only found in some sports cars. Now a 6 speed transmission is more common and some spots cars are starting to use a 7 speed transmission, like the new Corvette. Maybe it'll be a matter of time before a 7 speed is more common...

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[The Champ]

I'm kind of going through this issue on my GTO. It has 3.42 gears in the 12 bolt rear end and I'd like to lower my RPM's while driving on the Interstate.

Simple (but expensive) thing to do would be to put a modern 5 or 6 speed manual transmission in.

But I like the stock appearance and have already done a full restoration on my original Hurst shifter.

What I'm currently looking at is switching out the 3.42's for a set of 3.08's and then replacing my original M20 Muncie with an Autogear Muncie M22Z.

This is a wide ratio with a 2.98 first gear (vs the M20's 2.56), so even with the 3.08's gears in place I can still put on an easy smoke show at the stop light (doing the gear ratio math it works out to like a 3.55 rear in 1st).

4th gear is still 1 to 1.

Cost of the brand new M22Z is less than $2000. Swapping the gears about another $500, so about $2500 total.

A Tremec 600 5 speed (or similar) will run well over $4000 by the time you get the new driveshaft, clutch, shifter to make everything work.

With the M22Z, no one will know I've done anything. But I'll be cruising at under 2700 RPM at 70 MPH instead of 3000..

 

[Kingbambino22]

I need some advice here. I own a 2013 Chevy Sonic RS. I mostly drive it on the Highway. My average RPM range is about 3,100 at 70 mph. At first I thought that that was normal for this little 1.4, but after driving a Chevy Cruze with the same engine, I noticed that the RPM was 2,100 at 70 mph. That's when I started to worry. So, I did some Internet research and read in various websites that the cruising RPM in the Chevy Sonic 1.4 with a manual transmission should be between 2,100 to 2,500 RPM's when driving at 70 mph. That leaves me with the question, why are my RPM's at 3,100 when I'm driving at 70 mph? And how can I fix what ever it is that is wrong with my Sonic? Can someone please help me with some good information?

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I have a 2015 Sonic RS auto and when I'm on the highway cruising at 80mph my RPM is right around 3000.

 

[tainopayute]

I have a 2015 Sonic RS auto and when I'm on the highway cruising at 80mph my RPM is right around 3000.

That is why I was first asking if getting RPM,s of 3,100 while cruising at 70 mph was normal in the RS with a manual transmission because other Sonics, like yours, get different RPM's when cruising at highway speeds.

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