wesmanw02

Hey all

I'm hoping to get a 2006 or 2007 Cobalt SS S/C, and I was just curious about how the car is on the highway in terms of gear ratios and such.

I can't stand when cars have really short O/D ratios, like our '03 Honda Civic. Even in 5th gear, it really screams at 70MPH - something like 2700RPM. You have to give it half throttle just to keep the car going

So what kind of RPM's do all you SS S/C owners push on the highway, like between 65-80MPH?? And do you ever find you have to downshift back to 4th in order to pass at highway speed, or can you just keep it in 5th??

I'm just curious. I know the SS has nice low-end power, but I'd just like to know how much grunt its actually got

Thanks in advance.

MarcS

I have taken it on the highway a few times, but have not paid much attention to the TAC. It does lose most of it's kick in 5th at 70-80 mph however.

The SC makes great low end power but when it comes to high speed manuvers you need to shift to 4th.

hatrickstu

iTrader: (1)

i drive on the highway alot in mine, it has about 2700 miles on it. you dont need to shift down to pass, plenty of power. 3rd redlines at 100 and 4th at 120, if you are going 70 or so then it will glue you to the seat if you nail it in third, and same for 4th. If you just need to make a semi fast pass or what not then 4th has plenty of power. for a regular pass it has plenty of power in 5th between at 65. if i remember correct it is turning around 2800 at 85 or so. it isnt loud at all though. Keep in mind the peak horsepower RPM level is 4400 i think, not sure on that one though.

JamesBrown

Ya, I believe I'm at about 2500 rpms going 80mph on the freeway in 5th. Never kicked it down to speed up or punched it in 5th so not sure about the power.

CobaltSS132

Actually i think 5th gear at 80 is 3000 rpm, i could be wrong but i usually pop it in 5th and hit 80 then flip on cruise control, and i remember the rpm being 3000

And if ur going to pass some1 going slower then you, then you wont need to down shift it has enough pull to get you to 90-100 n half throttle in around 3 seconds or so. if u really need power just go to 4th and you will fly.

And ya the supercharger isn’t so great for high end power, mostly torque and low end.

But it is relatively loud if u compare the stock exhaust to any other cars.

codyss

I see alot of posts from SRT-4 guys saying the SS/SC has no high end horsepower and no high mph speed. I myself think this car is more potent from high speed rolls. This thing plian out screams on the highway.

MarcS

It's a good high speed car, but it needs more power on a high speed roll in my opinion. That's just me. I like to be pinned to my seat full time

Nightcrawler

I just confirmed this morning.. It's about 3000RPM on the button at 80mph as good as my eyes can tell me while still keeping my eyes on the road!

That's better than my '99 Z24. That hits 3000RPM at 70-75 I think.

3fo893013L

Ok, the SS has great top end power as well.... don't let any one fool you. I can pull 100mph in 3rd gear before my shift. In 4th I can go up to 120 before having to shift. That if you go ***** out.

I've raced an SRT-4 that has three people in the car and I had my girlfriend in my car. We were dead even from a 20mph roll (both stock) we were dead even till I missed 5th gear at 120MPH.

1st 20MPH (shift to 2nd)
2nd 60MPH (shift to 3rd)
3rd 100MPH (shift to 4th)
4th 120MPH (shift to 5th)
5th ???MPH (All Done for Fun)

This car has top end power too.

zinner

Well both 4th and 5th gears are over drive, so you don't have to worry about high engine speeds on the highway.

It's not going to be at V6/8 levels simply because thats not where an I4 makes it's power.

I find myself cruising in 4th gear a lot on the highway between 50-75. I only go into 5th when I want good gas milage or don't need much pep.

JapEatr

iTrader: (9)

i can do almost 33 mph in 1st
even with the ac on it will still pull in 5th, look at the boost gauge next time cruis control is on
you can feel the acceleration when it hits boost just to correct itself on the speedo

zinner

Yep I can't feel any difference with the A/C on in this car. In previous 4 cyls you could feel the car lurch a bit if you flipped on the A/C.

jester

3000 rpm is around where my cutlass supreme sits at 80 as well but its the same transmission as every other GM car the 4 speed auto.

wesmanw02

Thanks for the replys guys, sounds like the gearing is pretty good.

One more question along the same lines - do you guys by any chance know at what RPM the engine goes from Vacuum to Boost?? I'd guess between 2500- 3000 RPM, but I've never driven one, so I'm not sure.

Just curious, because I've heard that if you can stay out of boost in most F/I cars, it really helps with fuel efficiency (like around town and such). Of course when you want the power, all you have to do is take the RPM's up until you hit boost

Nightcrawler

I'm not sure, but if you watch the boost gauge.. it seems to always try and figure out what you're doing. Regardless of RPM's, when I step on the gas to any degree, the boost gauge kicks into positive boost immediately.. if it's only a small thorottle increase, it will quickly fall down and let me accelerate or cruise without boost.

If you you keep increasing throttle, it stays boosted. I don't think I explained this too well, but essentially it seems to predict if you're actually accelerating, lightly accelerating, or just cruising. It seems to work very well. I drove 50 miles both in city and highway today and I can keep it from boosting almost 100%(bar the initial brief boost response from any throttle increase) of the time if I want to.

I really like this design. It seems very smart for gas mileage and still keep power on demand. The power is there immediatly if you need it, and it's flexible enough that you can essentially control when the car boosts to some degree. I'd say that's one reason we have seen on here the gas mileage is VERY sensitive to your driving habits. I drive a little less spirited than most on this board. I've used half of my first tank of gas am at 25mpg already. That's pretty high for the first tank. That includes stop and go traffic, some idling warm up time in the morning, and varied engine RPM's I've been careful to try and keep the RPM's varied during break in. So I'd say my results are pretty darn good so far. But I could be judging prematurely.

redrocket

You are thinking of a Turbocharger!
A Supercharger is different and both were designed for different reasons,
with defferent performance output and efficiencies. I will try to keep this short.
Superchargers are driven from the crank, which in some circles is not efficient (road racing, indy cars, grand prix, etc.) as it takes power from the engine to turn the supercharger. Engines that run most of their lives at high RPM flow a huge amount of exhaust. This is where the turbo shines as it is driven off the exhaust gasses (efficient). However, it must spool up (increase its RPM) to create boost, which it gets from exhaust gases. Superchargers constantly create boost and increases with engine RPM. It is less efficient but is instant. The SS from what I've read does bleed off boost. There is another post here that explains the bleedoff process. This what Nightcrawler is seeing on the gauge. Turbos were designed for HP, superchargers for torque. Example: a turbo on an SS would be a dog, as the 2.0 has very little torque naturaly asperated, which it would be until the turbo spools up to boost rpm. However boost from the supercharger is created at all rpm's and creates the torque in the lower rpm range that the engine can't.
The supercharger will boost from idle.
A Turbocharger may not boost until 2000 rpm.
In this day and age these lines have slightly blurred,.

Gas Mileage - as with any performance car, the mileage you get is related to your foot. I also was at 25 mpg. Made a few 120 mph runs and it dropped to 20.

wesmanw02

No need for the explaination man, I'm very familiar with engines, turbos, and Superchargers and how they all work

As you said, the S/C is constantly spinning at the same speed of the engine, so theoretically its always making boost. However, my question was along the lines of when it actually makes enough boost to overcome natural engine vacuum. So basically at what RPM the boost guage moves past "vac" and into "boost".

Now if what you're saying is that it goes right into boost off of idle (under throttle), then I see what you're saying. However, if the car is roling at 1K RPM in 2nd and you punch it, its physically impossible to create immediate boost , since the RPM's have hardly changed. Unless of course the boost is there and its just being held back or bypassed by the BPV.

Please elaborate if possible - I'm rather knowledgeable in this stuff as I mentioned, so I'll be able to follow what you are saying

Nightcrawler

'Unless of course the boost is there and its just being held back or bypassed by the BPV.'

This is what it appears to be doing. I'm fairly certain it will still register a little bit of positive boost. I've accelerated from 1500RPM several times and I believe it still shows a bit of positive boost. I will give 1000RPM a try later today and report back.

PyroSS

the car is kind of designed with a economy person in mind with power when needed. which is why 4th and 5th gear has a lil bit of power and it should sit low on the RPMs when going speed limit. designed with economy in mind. thats why they have very lil HP. say 205HP. if you shot up to 300+ your gas mileage will shoot down. i've taken it to about 130 and backed off in a dealer test car. has power in the high speed area. but as to actually take the car past 140 since it's supposed to top at 145. is a lil uneasy for me. seeing its a FWD car and all. i've taken my VR-4 AWD up to 170 and it a huge rush. but the steering is really touchy. just watch it with the corners and bumps above 130 and 140. it'll get a lil rough. hate to see someone smash their beautiful car. my VR-4 did 90MPH at 3k RPM and 120MPH at 4k RPM and 165MPH at 5600RPM. above that i can't remember. my redline is 7 grand. good Gas mileage on the high way. and from the number the cobalt SS/SC as high speeds about 100-120 seems to get good gas mileage.

codyss

Anyone whos says the SS/SC has no top end is shifting into 5th at 50mph and flooring it.

olddude

Well, you are about to get a bit more knowledge. You are confusing absolute PSI and PSIG (gauge). You are also forgetting how vacuum is created in an internal combustion engine. Vacuum is the measure of resistance. At idle, with your throttle closed (aside from what is needed to maintain enough air to support combustion), it is relatively difficult to suck the needed air as the throttle plate is a restriction. Vacuum is as high as it will get. When you open the throttle, the restriction lessens and measured vacuum will decrease (even though you are actually moving more air) Anyone with a n/a vehicle and a vacuum gauge can tell you this.

The s/c does not turn at the same speed as the engine unless the pulley sizes are the same, but it does increase at a linear rate based on engine RPM increasing. Down low, it does not move much air, but it does move some.


(Using sea level standard conditions) there is 14.7 PSI at all times (same as in your blower, same as everywhere else, so it does no good). A vacuum/boost gauge is usually calibrated to read in PSIG (pounds per square inch gauge) and essentially subtracts the ambient conditions. So you gauge will read 0 at one standard atmosphere. When you spin the blower, even at slow speeds, it will pressurize itself and the intake if you allow it. If it spins fast enough to add 3 PSIG, It is at 17.7 PSI. Now, let us assume for the sake of argument that at 3 PSIG you are running at 10% throttle. It makes no difference, but just as an example. Let us say that that particular throttle opening makes the measurable vacuum drop from the 9.5 psi at idle to 7.5 psi. What does your gauge read? Well, if it is a true gauge, it will read 7.5 PSIG vacuum, (I do not think the CSS gauges are real, I believe they are a calculated value from the TPS, engine speed, air temp, etc.) It would read the 7.5 PSIG vaccum because the bypass valve in the s/c has not been told to allow boost, but the blower is moving enough air to add that much boost if it were allowed to do so. You are just cruising along at 10% throttle so there is no point in adding boost, you want the greatest fuel economy possible, so you shunt the boost away, no real drag from the s/c as there is no load on it, no extra fuel needed.


Now, you whack the throttle open, your measurable vacuum goes to zero, your gauge should flip to zero and the bypass closes, you obviously want power now. The s/c is spinning fast enough at that instant to supply 3 PSI of boost to ambient pressure (14.7 PSI in our example) Your gauge reads 3 PSI(g). The blower has properties that can be specified, when maximum boost occurs, how much air it pushes, etc. I do not have the specs on the CSS s/c, but I would imagine GM has chosen it to provide the maximum boost down fairly low on the RPM range and simply bleed off boost to keep it where they want as it spins up towards the engines redline instead of increasing. So you might have it max out at 3000 RPM (just a guess, no facts to support it.

So, to answer your long ago asked question, if you are below 3000RPM (or wherever maximum boost is first reached by the blower) and open the throttle all the way, you will immediately see your gauge snap from vacuum to positive boost of between zero and the bleed pressure amount. If you open the throttle at a RPM over boost bleed level, it will jump to full boost immediately. Even at 1200 RPM, you will see boost on a true gauge if you open the throttle all the way. That is assuming there is no significant bottle-neck in the intake tract.

You may not see it on the CSS gauge as it does not read true PSIG (from what I have read, it is a calculated value, not measured), but that is how it should work.

You will see varying amounts of boost with varying throttle openings. On a true gauge, if you are moving enough air to boost 10 PSI at 2800 RPM and there is still 7 PSI vacuum at that throttle opening, you will see 3 PSI on the gauge if the bypass valve allows that boost to enter the intake. Closing the throttle at any RPM should shunt all the boost out of the intake and drop the vacuum all the way down to idle levels immediately. Now, if you take the same conditions and go WOT, you will see 10 PSIG right now!

That above is pretty simplifed, but should give an understandable overview.

PyroSS

damn man i know a lot about cars. and a lot about turbo's S/C not so much but man i got lost on what you were sayin. i would read and be like oh ok yeah i know that. then it would drop to like HUH??? then be like ok ok yeah yeah. then. ehh then what the hell???? HUH?? and then i started skimming it. i'll try read it again later but yeah. right now i'm lost. lol. but from what i read and UNDERSTOOD makes sense.

Darksun

I'm surprised no one saw this but im sure 4th pulls a lot longer than 120 mph i've got mine to stretch to damn near 140 mph.
More like between 135 and 138. 5th is horrible for any type of pull trying to top the car out but it has just enough kick that you don't really have to downshift to forth to pass someone in traffic.

RedCobaltSS06

Either way, sounds quick as hell to me compared to my former big ass truck... lol. i'll be so happy behind the wheel if mine EVER shows up...

phxSS

Solution: get a V8