: Questions on CTS-V Highway Performance



Formula57
03-29-09, 10:50 PM
Hello All,

:welcome:

I'm new to the forums and close to buying a CTS-V. I have a couple of questions:

1) I went on a test drive in a new CTS-V with 400+ demo miles. I was able to take it on the highway. The salesman said "punch it." So, on the long entrance ramp the speedometer easily passed the 100 mph mark. Perhaps my expectations were too high, but there was a noticeable strong vibration I did not think should be there. I did not feel the vibration at 70 mph. Can anyone else confirm smoothness or lack thereof at 100+ mph?

2) I calculated (and confirmed in real world driving) that my engine rpm's in my Firehawk's LS1 engine with M6 transmission at 70 mph are 1568. At that same speed, I calculated the CTS-V rpm's are 1896 with auto or 2059 with manual. So, two questions:
a) Can anyone confirm my numbers? I didn't get a chance during my test drive because I wasn't thinking about it nor did I care at the time. :D
b) I understand gas consumption is at the bottom of the priority list with this car, but I'm curious why the CTS-V would run the engine speed so much higher in 6th gear when it has so much more power and torque. Why would the LSA would be made to run faster than my "little" ol' LS1? Why is the CTS-V geared the way it is?

Razorecko
03-29-09, 11:08 PM
^ did you take the auto or the manual out for the test drive ?

Formula57
03-29-09, 11:21 PM
^ did you take the auto or the manual out for the test drive ?

I took the auto on a test drive.

As an aside, I don't see any manuals sitting on the lots down here in S. Florida. I did see one once, but it was spoken for before it arrived back in December.

OldDrummer55
03-29-09, 11:39 PM
I took the auto on a test drive.

As an aside, I don't see any manuals sitting on the lots down here in S. Florida. I did see one once, but it was spoken for before it arrived back in December.

Hope you've check out Tony for a great deal on a V2... :thumbsup:

neuronbob
03-30-09, 12:27 AM
I can only comment on the first question. The CTS-V is a lot like my previous RL that it was eerily stable at 100 mph--no vibrations, no muss, no fuss, the engine almost sounds like it's at idle (the RL, being a V6, sounded like it was working hard, and it was, at 3k rpm). I only got it up to that speed once, on the way home from the dealer, it was not intentional, lasted a few seconds, and it scared the crap out of me because I had no idea I had attained that speed.

I don't remember engine speed at 100 mph and I don't plan to find out again until I'm on a track. Sorry!

+1 on checking out Tony since you live closer to his dealership than any of us... :D

jwa999
03-30-09, 12:54 AM
Car never vibrates for me. I hit 100+mph almost every day (steering wheel blocks my view of the speedometer, and i'm sticking to that story). *very* stable, using sport suspension. Have an automatic, but only use the sport automatic at the stop light. Automatic shift points don't work for me. During drive I use the steering wheel buttons pratically always. Don't like it when the engine drops below 1500rpm.
Car is strong in every gear. Still have trouble launching it at a stoplight. In sport automatic, will start the car moving without spin, but then accelerating more, it will start to spin again... But very stable, easy to recover. In manual mode, it will start in 2nd gear very nicely, very strong, helps with wheel spin.

Formula57
03-30-09, 01:27 AM
I can only comment on the first question. The CTS-V is a lot like my previous RL that it was eerily stable at 100 mph--no vibrations, no muss, no fuss, the engine almost sounds like it's at idle (the RL, being a V6, sounded like it was working hard, and it was, at 3k rpm). I only got it up to that speed once, on the way home from the dealer, it was not intentional, lasted a few seconds, and it scared the crap out of me because I had no idea I had attained that speed.

I don't remember engine speed at 100 mph and I don't plan to find out again until I'm on a track. Sorry!

+1 on checking out Tony since you live closer to his dealership than any of us... :D

Yeah - that 100 mph sneaks up on you quickly. With the speedometer needle straight up, you're going 100 mph - in my current car, I'd only be doing 75 mph. It could take time to adjust. ;)

I'll have to check out Tony's deals - thanks for the suggestion. There are a bunch of local dealers with inventory from December, so I've found a bunch of cars $3-4k under MSRP.

With regard to engine speed on the highway, I gave figures for 70 mph, which should be easy enough to check - even for those still breaking in their cars! :)

Formula57
03-30-09, 01:30 AM
Thanks to all the replies on the lack of vibration at 100 mph so far. Now I know not to buy a demo car (or at least the one I drove)!

vperl
03-30-09, 01:45 AM
Hope you've check out Tony for a great deal on a V2... :thumbsup:

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Rain in Spain
shoe is blue

jvp
03-30-09, 04:53 AM
b) I understand gas consumption is at the bottom of the priority list with this car, but I'm curious why the CTS-V would run the engine speed so much higher in 6th gear when it has so much more power and torque. Why would the LSA would be made to run faster than my "little" ol' LS1? Why is the CTS-V geared the way it is?

Those are a lot of questions that can essentially be answered by your last one: it's all about the rear end gearing. The manual V is running with 3.73s in the rear end, which, unfortunately, means the car is going to be spinning at higher RPMs at highway speeds than other GM performance cars (Corvettes, F-bodies, et al). This is the primary reason for the V's atrocious highway mileage.

Why HPVO decided to have the V geared like that is anyone's guess. Performance. Engine characteristics at lower RPMs. Any number of possibilities. You'd have to ask an HPVO engineer (if you can find one).

jas

OldRoadDawg
03-30-09, 10:58 AM
You'd have to ask an HPVO engineer (if you can find one)

Just saw one of those guys the other day.

odla
03-30-09, 02:43 PM
where i n south fl are you i test drove a blk on blk m6 a few weeks ago.

Luna.
03-30-09, 02:51 PM
Why HPVO decided to have the V geared like that is anyone's guess. Performance. Engine characteristics at lower RPMs. Any number of possibilities. You'd have to ask an HPVO engineer (if you can find one).

jas

I asked the same question and was told that it's primarily about the weight of the car.

The V isn't a "light" car like the Corvette, hence, the gearing has to be appropriate for its weight.

Seemed reasonable to me...

trukk
03-30-09, 05:04 PM
I asked the same question and was told that it's primarily about the weight of the car.

The V isn't a "light" car like the Corvette, hence, the gearing has to be appropriate for its weight.

Seemed reasonable to me...

I always wondered why they just didn't make 6th a bit taller to compensate.....there must be a reason there.

-Chris

jvp
03-30-09, 05:14 PM
I always wondered why they just didn't make 6th a bit taller to compensate.....there must be a reason there.

That move is a money-saving thing. Just use the same transmission as they do on their other 6-speed manual cars. Perfectly understandable.

The use of the 3.73s is what I question. The damn car has so much low-end grunt that even with the automatic's taller rear end, it would still get up and move.

But... oh well.

jas

Formula57
03-30-09, 10:23 PM
where i n south fl are you i test drove a blk on blk m6 a few weeks ago.

I'm in Broward. I haven't tried any Miami dealers, yet. At which dealer did you drive the M6?

Formula57
03-30-09, 10:34 PM
I asked the same question and was told that it's primarily about the weight of the car.

The V isn't a "light" car like the Corvette, hence, the gearing has to be appropriate for its weight.

Seemed reasonable to me...

Thanks. That does seem reasonable, but I wonder why they couldn't have more of an overdrive in 6th. I also wonder what's the most gas they could save by doing so, anyway?

There isn't cylinder deactivation at cruising speed, is there? I haven't read that anywhere but thought I'd ask.

Fubar75207
03-30-09, 11:06 PM
Additionally, the demo was a little low on miles. It seems like my car was just starting to get it's power curve right at 1k miles and it felt even better at 2k. fyi

Formula57
03-31-09, 12:29 AM
Additionally, the demo was a little low on miles. It seems like my car was just starting to get it's power curve right at 1k miles and it felt even better at 2k. fyi

Are you saying your CTS-V vibrated less over time?

Fubar75207
03-31-09, 09:56 AM
Not at all, I have never noticed a vibration in my car. The demo I drove had about 2500 miles on it so it was basically broken in. When I picked up my car it seemed less responsive and willing to accelerate than the demo. After 1k miles my car got noticeable better.

Again, I have no relative information regarding the viration... sorry.

Luna.
03-31-09, 03:18 PM
I always wondered why they just didn't make 6th a bit taller to compensate.....there must be a reason there.

-Chris

I asked the same question (great minds think alike :thumbsup:) and, ultimately, I believe that it comes down to what JVP just said...a money issue. Sure, in theory, one can just swap out, say, 6th gear ratios to make it all "balance" out in the end, but that also means that you must spend more money making certain parts stronger, sometimes significantly stronger. The taller 6th gear is, the more stress it's going to be dealing with. To maintain the same level of consistency/reliability, that means you will probably have to upgrade the part, which means more money.

Again, it seemed to make reasonable sense to me, but I'm far from an expert.



There isn't cylinder deactivation at cruising speed, is there? I haven't read that anywhere but thought I'd ask.

No, I do not believe there is a cylinder de-activation system on the LSA

atdeneve
03-31-09, 03:44 PM
Not at all, I have never noticed a vibration in my car. The demo I drove had about 2500 miles on it so it was basically broken in. When I picked up my car it seemed less responsive and willing to accelerate than the demo. After 1k miles my car got noticeable better.

Again, I have no relative information regarding the viration... sorry.


Yeah, I've noticed that with the V1s, as well. And I've broken in more than a couple of em.

You think there's a difference between 0 miles and 1,000 or even 2,000 miles? Granted, the LSA is a considerably different beast, but if it's anything like the LS6s during their beginning stages, wait until you get beyond 5,000 to around 6,000 miles. It really seems to wake up then, in both perceived performance and in it's growl...

JFJr
03-31-09, 04:49 PM
Granted, the LSA is a considerably different beast, but if it's anything like the LS6s during their beginning stages, wait until you get beyond 5,000 to around 6,000 miles. It really seems to wake up then, in both perceived performance and in it's growl... My experience with the LS1's in my two 6-speed C5 Corvettes was that they took 10,000-15,000 miles before they reached full potential in fuel economy and performance. I believe that the LS6 in my 2005 CTS-V "broke in" a little sooner.

Razorecko
03-31-09, 08:27 PM
I generally see the breakin finale at 5-6k miles in terms of larger motors like the hemi. Till than drive it hard and do constant fluid changes.

Caddyscat
03-31-09, 09:00 PM
I went to Branham in Miami on Saturday. They had a loaded Thunder Gray auto. They said they'd do GMS also.

JEM
03-31-09, 09:06 PM
I asked the same question (great minds think alike :thumbsup:) and, ultimately, I believe that it comes down to what JVP just said...a money issue.

I think it has less to do with money than with needing to meet specific competitive performance and 'feel' targets.

It may be that the car lost just enough with the taller gears to fall behind some competitive benchmark (E63?)

Or it may be that it did lose just enough top-gear 'punch' to be noticeable.

And the fact is that those looking to buy the manual transmission in this car are mostly looking to get the most they can get out of it. <2000RPM at 70 is still very tall gearing.

Formula57
04-01-09, 05:44 AM
I went to Branham in Miami on Saturday. They had a loaded Thunder Gray auto. They said they'd do GMS also.

I noticed online they have two black ones with Recaro's. Did you beat the heck out of any of them? :lildevil:

Formula57
04-01-09, 05:48 AM
I think it has less to do with money than with needing to meet specific competitive performance and 'feel' targets.

It may be that the car lost just enough with the taller gears to fall behind some competitive benchmark (E63?)

Or it may be that it did lose just enough top-gear 'punch' to be noticeable.

And the fact is that those looking to buy the manual transmission in this car are mostly looking to get the most they can get out of it. <2000RPM at 70 is still very tall gearing.

After talking to some others (nothing definitive, though), fuel economy was probably sacrificed to a combination of factors (acceleration, reliability, cost), but I tend to believe that performance (acceleration) is probably the main reason.

verbs
04-01-09, 05:15 PM
Those are a lot of questions that can essentially be answered by your last one: it's all about the rear end gearing. The manual V is running with 3.73s in the rear end, which, unfortunately, means the car is going to be spinning at higher RPMs at highway speeds than other GM performance cars (Corvettes, F-bodies, et al). This is the primary reason for the V's atrocious highway mileage.No, it's not the primary reason for bad gas mileage. The difference between the 3.42s in other GM cars and the 3.73s in the CTS-V might be a 1mpg difference at highway speeds. The primary reason for such shitty mileage is the 556hp supercharged engine and a 4200lb car. Also, you failed to mention that the tires of the CTS-V are a good inch more in diameter than the Corvettes and Fbodies, therefore the shorter 3.73 gearing is negated to some extent by the taller tire size.

Luna.
04-01-09, 05:26 PM
I think it has less to do with money than with needing to meet specific competitive performance and 'feel' targets.

It may be that the car lost just enough with the taller gears to fall behind some competitive benchmark (E63?)

Or it may be that it did lose just enough top-gear 'punch' to be noticeable.

And the fact is that those looking to buy the manual transmission in this car are mostly looking to get the most they can get out of it. <2000RPM at 70 is still very tall gearing.

I certainly can't say that's not possible, but I would say, if that's the reason, they are morons cubed...

I know that various magazines do a "top-gear" acceleration test and that's often really dubious, if not lame. Few people, if anyone, is going to go for maximum acceleration and leave it in 6th gear... :hmm:

jvp
04-01-09, 06:08 PM
The primary reason for such shitty mileage is the 556hp supercharged engine and a 4200lb car.

Wrong. Completely wrong. At HIGHWAY SPEEDS (read carefully, I think I qualified that enough times...) the engine's torque and and vehicular mass don't come into play much at all. What does come into play is the RPMs at which the engine is turning, and the speed at which the car (with it's fairly poor aero) is trying to cut through the air.

Again, at static highway speeds, vehicular mass means very little. City driving is another story entirely.


Also, you failed to mention that the tires of the CTS-V are a good inch more in diameter than the Corvettes and Fbodies, therefore the shorter 3.73 gearing is negated to some extent by the taller tire size.

Look at the OP, and specifically, the paragraph numbered 2. He calculates (correctly) the RPMs at which the engine is turning at 70MPH. Those calculations take into account the tire size.

It is because of those RPMs that the engine is gulping down fuel, even on the highway.

jas

Richie18
04-01-09, 07:19 PM
Wrong. Completely wrong. At HIGHWAY SPEEDS (read carefully, I think I qualified that enough times...) the engine's torque and and vehicular mass don't come into play much at all. What does come into play is the RPMs at which the engine is turning, and the speed at which the car (with it's fairly poor aero) is trying to cut through the air.

Again, at static highway speeds, vehicular mass means very little. City driving is another story entirely.



Look at the OP, and specifically, the paragraph numbered 2. He calculates (correctly) the RPMs at which the engine is turning at 70MPH. Those calculations take into account the tire size.

It is because of those RPMs that the engine is gulping down fuel, even on the highway.

jas

You are definitely over emphasizing the effect engine RPMs has on highway gas mileage. Drag and engine size/HP have much more effect on highway MPG than rpm does.

By your reasoning we should gear all our cars to be at idle while at highway speeds, obviously though no manufacturer has done that because it just doesn't work that way.

A truck of mine that weighs 5000+ with a 4.6L V8 6 speed and has tall gearing still barely gets 20mpg on the highway, so that considered the CTS-v doesn't get terrible gas mileage on the highway.

The CTS-v manages 19 on the highway, the ZR1 20mpg, even with it's sleeker body and taller rear end.

Also just FYI, the CTS-v does have a unique gearing, they just didn't slap the TR-6060 in there without looking at the gearing, as that is one of the most important things when pairing a transmission with a high performance engine.

poor-sha
04-01-09, 08:31 PM
Not that I'm looking to do this, but has anyone looked to see if they make aftermarket gears that would fit a V2? I don't know enough about the rear end in these cars to know if they are the same gears sets as something else (i.e. F-body, truck, etc.)

Formula57
04-07-09, 12:49 AM
Check out this quote from Motor Trend on the 2010 Ford Mustang GT500:

"Shortening the axle ratio from 3.31:1 to 3.55:1 boosts acceleration performance while lengthening the top two ratios (by 17.5% in sixth) elevates highway fuel economy by 2 mpg, dropping the gas-guzzler tax by $300 (to $1000). "

So, Motor Trend answered my one question: it is very possible to save 2 mpg on the highway by gearing the car "correctly," but now I'm wondering how that would affect top speed runs...

BTW, if the '09 CTS-V got 2 mpg better on the highway, the gas guzzler tax charged would be cut by $900 (not to mention savings on annual gas expenditures).