Questions about 1998 Deville Northy

[The Fred]

Well,

I love 1990 and 1991 Cadillacs..

Especially the Sevilles.

The problem is that the 4.5 / 4.9 don't have enough guts to them.

Plenty of low end but not much after that.

The clincher was when a huge dodge truck with only a 318 blew off my doors yesterday.

(Not that I make a habit of racing - but I would like to imagine that a dodge truck could not blow off my doors. For goodness sakes what if I was chasing someone or what if someone was after me?)

So I am considering a 1997 - 1999 Deville

Questions:

1. How big of a real difference is there between the base and Concours

(275hp for the base Deville and 295-300hp for the Concours?)

2. Is the Concours able to exceed 112mph?

3. How can a guy uncripple one of the 112mph cars?

4. Do all Northies not have alot of low end power?

5. How difficult is it to install an exhaust cutout on there?

6. What is a good way to get up above (well above) 300hp with these?

Again,

I am not a speed demon type of maniac over here and usually drive town like a half dead old man but when I want to get on it I want the darned thing to perform. And I want to be able to chase down or escape anything out there.

Thanks,

The Fred.

[KHE]

I have both a SLS and a STS (275 & 300 HP) and they accelerate approximately the same - at least my "butt dynomometer" can't tell much of a difference.

If the Concours had Z-rated tires when it left the factory, then it won't have a speed limiter. The only way to remove the 112 MPH limiter on the base cars is to have the PCM reflashed with the VIN of a car with Z-rated tires. No dealer will touch that for liability reasons - thank the trial lawyers for that.

The Northstar engine is already producing over 1HP per cubic inch - Mark99 installed a supercharger but he spent big bucks.

[The Fred]

I've heard of the PCM many times..

Some sort of control module is it?

Is it similar to flashing the bios on a motherboard where you can end up screwing the thing all up to hell?

Can you just simply replace the PCM with one from a junk automobile and sell the old one for about the same money you spent?

[Ranger]

PCM = Powertrain Control Module. It is the Northstars brain.

[GreenMachine]

in referance to your number 4 about the northstar not haveing low end-grunt. Well I know my 275 pulls stong off the line, no problem getting here going up to highway speed and beyond

[Bruce Nunnally]

1. How big of a real difference is there between the base and Concours

(275hp for the base Deville and 295-300hp for the Concours?)

The final drive ratio is different also, which contributes to acceleration in favor of the higher hp version, at the cost of fuel consumption.

2. Is the Concours able to exceed 112mph?

I think the Concours got a 130 mph limiter as I recall, if ordered originally with speed rated tires, but may have gotten the 155 mph limiter.

3. How can a guy uncripple one of the 112mph cars?

Covered above. So be clear, the cars are not crippled, but are limited to the speed that is safe for the tires they came with.

Yes, you can reprogram the powertrain control module, but only with a Tech II ($3K) and the Dealer PCM calibration disks/info. It would be very difficult to find a PCM from a car of the same year and model and options but different speed rating and swap them.

4. Do all Northies not have alot of low end power?

The Northstar has good torque, but does make a lot of hp at relatively higher rpm vs traditional Cadillacs. It is actually making more power than the older models at relatively low rpm, especially in hp/pound it carries.

The taller final drive of the performance versions does help get the engine up the rpm range faster.

5. How difficult is it to install an exhaust cutout on there?

Exhaust mods are the easiest way to get some extra power.

6. What is a good way to get up above (well above) 300hp with these?

A great way to get over 300 hp in a Cadillac Northstar is buy the new CTS-V (400 hp/$51K), Supercharged STS-V (469hp/$77K) or XLR-V (440hp/$100K).

For a lot more than 300hp in a Cadillac, I would shop for a 96 Fleetwood with the LT1 engine/260hp and add a supercharger (+100hp), shop for a 2004 CTS-V with LS6 engine at 400 hp, or a 2000+ Escalade and add a supercharger. The Escalade is surprisingly quick; a 2007 model does 0-60 in around 6.5 seconds.

For a non-supercharged Northstar, exhaust mods plus a 75hp-100hp nitrous setup is an interesting and inexpensive option, but nitrous has unique issues associated with it.

[The Fred]

That sounds fine and nice but nitrous is for kids

PS: 130 is plenty.

[JasonA]

As Bruce said, although the Northstar is a screamer at high rpm, it also makes more power AND torque at low RPM than a 4.1/4.5/4.9L. Look at a few graphs from GMPowertrain:

http://www.jnjhome.net/cadillac/northstar.htm

The LD8 engine (DeVille, DeVille d'Elegance) is cranking out over 250 lb*ft of torque at 1500 rpm, and keeps climbing from there. The 4.9L engine's torque PEAK is 250 lb*ft, at closer to 3000 rpm probably. The LD8 engine is an extremely flexible engine. I can run at 40 mph in OD (about 1050 or 1100 rpm) all day long, up and down hills, doesn't matter. The engine has a lot of low-end torque...but the high-end horsepower seems to overshadow it and the result is a common complaint of a relatively "soft" low-end.

The L37 engine (DeVille Concours) is rated at 300 hp and slightly lower torque. But it has a shorter final drive ratio (3.71 vs. 3.11) to make up for it. Field performance is very close between the two powertrains. Manufacturing and production tolerances can easily overcome the technical performance difference in some cases.

The DeVille and DeVille d'Elegance originally came with S-rated tires from the factory, and thus got 112 mph speed limiters. All DeVille Concours models got H-rated tires and got 130 mph speed limiters. No Z-rated tires on the DeVille, at least not in the 1997-1999 timeframe.

You'll love either version of the Northstar you get in a newer DeVille. I have the LD8 version in my SLS and just love it. I can cruise at 80 mph and still be turning only 2000 rpm with the tall 3.11 final drive and return EXCELLENT fuel economy (20 city, 30 highway). I don't long for the additional 25 horses because, as stated above, the field performance is really too close to call anyway, and you do lose some fuel economy.

You wrote:

"I am not a speed demon type of maniac over here and usually drive town like a half dead old man but when I want to get on it I want the darned thing to perform. And I want to be able to chase down or escape anything out there."

You really need a Northstar engine. It's about the smoothest engine out there from that timeframe, and is incredibly flexible. It'll ease down the boulevard all day long, and ride you around in style. But if you wanna play, it's instantly ready for the task. Short of the extreme end of the scale, like a Corvette or exotic, these are about the most comfortable "fast" cars out there.

[GreenMachine]

^hit the nail on the head with that post

[The Fred]

Good deal there..

I'm thinking about going down to a dealer sale and picking one up.

I don't usually like to do that for a personal automobile - but I can buy two or three at an auction for what they're going for around here.

I like those odds and could always end up with plenty of parts

What if I find a good 93 STS or 94-95-96 Deville?

The earlier Northy is pretty good as well?

(I'm thinking that I might stumble on a lower mileage at a lower price but I do prefer the 97 98 99 look)

By the way - thanks for the informative responses there folks.

It sounds like you really know your stuff there !

[JasonA]

Fred, the earlier Northstars were not mechanically different (for the most part), but did have green coolant from the factory. That's not a bad thing -- but it required more frequent maintenance that many owners may not have done. The Dex-Cool, starting in 1996, only required coolant changes every 5 years/150,000 miles. So you may be "safer" with a 1996 or later model, but that's really speculation, as you can't tell the maintenance history of any car without papers.

The DeVille's body style changed slightly (for the better in my opinion) in 1997. '94-'96 are the same, save for minor trim changes probably. To me, the '97-'99 DeVilles are my favorite contemporary DeVille, followed closely by the new '06 models.

[The Fred]

I was aware of the styling changes but I didn't know they came with old style coolant in them.. I sure do agree about the 97-99 look. I dig the looks of them alot more than I do the 94-5-6