I am considering buying a MY09 CTS and have test driven both a CTS with and without the DI engine. The model with the DI was in the second demo. After going through the same road course, I felt that the "standard" engine was the more powerful of the two. I find this strange. I know the DI engine with accept regular gas but does this translate into lower HP with the knock sensors adjusting to the lower octane fuel? The salesperson informed me that all of their demos use regular (87 octane) fuel.

I am not new to performance sedans. I currently drive a MY07 Lexus IS350 and had a MY06 Infiniti M45 Sport and MY03 BMW 530i (sport & Dinan). Except for the Infiniti, the power didn’t really develop until after 3k rpm’s. I just didn’t feel it with the CTS. Both models were Automatic with the AWD.

I know that it is a heavy vehicle but, again, I would expect better pickup with the DI engine.



Regards,
NHman

It's very simple.
You buy the one with the "normal" engine and I will run you for 1/4 miles.
You win, you get my car.
I win I get your car.
OK?

What I won't do......
I won't run you for 1/8 mile as I suspect that they will be pretty close.
Off the line they are about equal.
It is in the upper ranges that you feel the difference.

What to do if you can't feel the difference?
Buy the normal one.
You apparently don't visit 5000 rpm and above enough to make the DI worthwhile.
There is no stigma attached to the "normal" engine.

4000 pounds with 275 pounds of torque does not equal good off the line performance.
If you want to be impressed, take it out on the interstate and cruise at 100MPH and then just nail it.

I don't know. As a have very little experience driving a stock DI car (approx 9 miles), I can't really offer my opinion. As far as a DI with a Magnaflow cat-back, it feels pretty damned "spirited" to me. It does not feel like that torque is propelling 400 lbs.

how come went i put the gear in N, then slam on the padel and it goes up to 4000 rpm max?
the other day i tried to accelarate my DI on highway enterance (45 degree slop) and suddenly lost respond for about 1/4 second (prehaps i gave too much oil and the car wasnt warm up yet) but later i try to accelarate it.. it just didnt go fast.. this is the first time i tried to accelarate faster than i normally wanted. does it has something to do with the TC system even on straight road? do i have to turn it off for power?

Not being rude, but if you were serious about flooring it in neutral, it is to protect the drivetrain from you side-steping the clutch and neutral-dropping from 7000 RPM.

As far as the loss of power for a quick moment, I noticed it too, but I am chalking it up to the fact that the engine has such an incredibly odd torque curve. (See Fire and Ice's post "3.6DI gains 31rwhp")

It's very simple.
You buy the one with the "normal" engine and I will run you for 1/4 miles.
You win, you get my car.
I win I get your car.
OK?

What I won't do......
I won't run you for 1/8 mile as I suspect that they will be pretty close.
Off the line they are about equal.
It is in the upper ranges that you feel the difference.

What to do if you can't feel the difference?
Buy the normal one.
You apparently don't visit 5000 rpm and above enough to make the DI worthwhile.
There is no stigma attached to the "normal" engine.

4000 pounds with 275 pounds of torque does not equal good off the line performance.
If you want to be impressed, take it out on the interstate and cruise at 100MPH and then just nail it.

Southern, I find your comment on "visiting 5000 rpm and above enough" to be interesting. My present vehicle lives in the rpm range from 3500-6800. I thought this would be the case with the CTS with the DI engine but it didn’t seem to have a lot of power. The demo had 2k miles on the odometer. So the engine should have been sufficiently broken in. Therefore I wondered if the fuel quality could’ve been a factor. I have heard that regular fuel is an acceptable grade but is premium preferred? If so, the impact typically will affect timing which will lower the HP and overall performance. This would provide me with a good explanation as to the perceived advantage of the base engine over the DI.



Regards,
NHman

I read an article in one of the auto mags this week that compared the performnce between the base and the DI engines. They said the difference in 0 to 60 and the 1/4 mile wasn't significant (.1 or .2 seconds?) They said the only difference they saw were in the 30 to 60 mph acceleration (DI engine significantly faster) and the base engine got one more mpg around town. So if you are looking for transportation and not all out performance, the base engine would be fine.

Not being rude, but if you were serious about flooring it in neutral, it is to protect the drivetrain from you side-steping the clutch and neutral-dropping from 7000 RPM.

As far as the loss of power for a quick moment, I noticed it too, but I am chalking it up to the fact that the engine has such an incredibly odd torque curve. (See Fire and Ice's post "3.6DI gains 31rwhp")

ic..

what about the TC?

275 ft/lb of torque in a 400lb car ain't much. When that torque doesn't peak until 5200rpm it just magnifies the problem. The non di motor t.p. is 2100rpms lower, and therefore feels stronger down low. My 95 lt1 z/28 had 275hp and 90% of the torque available at 1700rpm. The camaro felt much faster than my 320hp '99 cobra, which had a much higher (rpm) torque peak. Of course at 5200rpm the lt1 was done pulling, the dohc mustang was just getting busy at 5000rpm. I wish the cts had an optional n.a. v8, it would alleave any doubt in my little brain. And, NO I'm not buying the pontiac instead.

Another thing to consider is the "block learning" state of the car. Modern powertrain controllers will adapt to your driving style. A new car vs. a car with 2k miles may feel different even if they're optioned the same. While this adaptation won't affect the power/torque of the car, it will affect your perception of how the car feels to drive. Things like throttle tip-in, transmission shift points, etc. could explain why the two demo cars were so close in the way they felt.

I can't answer the fuel question except to say that GM says that the engine is designed to run on 87 octane.
I know that "most" adaptive engines will run fine on 87, but better on 91 or 93 octane.
My Murano (With the 350Z motor) is like that. It's not a lot, but it does run demonstrably better on 93 octane (Premium in Florida).
It does this by constantly adjusting the timing.....
I assumed that the DI (at least.....and maybe the non DI also.....) would do this.....
But GM says no.

I test drove both Non-DI (first) and then DI.......I remember coming back and tossing the keys to the salesman and saying "now THAT's my car!" .