Top Speed

[67coupedeville]

I was leafing through my 1996 Northstar System brocher tonight and it says that the SLS and Eldorado have top speeds of 112 MPH, and the STS and Eldorado ETC have top speeds of 150 MPH.

My question is it the Z rated tires that give the STS and ETC a higher top speed or are the engines governed at 112 MPH on the on the SLS and Eldorado? Will an SLS and Eldorado do 150 MPH with Z rated tires?

Thanks in advance .

Spence

[Greg P.]

The top speeds are electronically limited by the PCM. The actual limit setpoint is determined by what type of tires the car was built with.

[JasonA]

Will an SLS and Eldorado do 150 MPH with Z rated tires?

In theory, they'd be very close. But as Greg said, the vehicle speed is electronically limited, and that speed is determined by the tires the car originally came equipped with. So even if you put Z-rated tires on after the fact, if the car originally had S-rated tires, it's limited to 112 mph. And if it had H-rated tires, it's limited to 130 mph. When the vehicle hits the limited speed, the PCM will start cutting off the fuel to the engine to keep it from accelerating any further.

[CaddyDaddy]

I don't know if this is true, but I believe you could put a PCM from the same year STS into an SLS and that would change the speedlimiter. Might not be a wise idea, But how often do you go above 112 mph?

[JasonA]

I don't know if this is true, but I believe you could put a PCM from the same year STS into an SLS and that would change the speedlimiter. Might not be a wise idea, But how often do you go above 112 mph?

I believe that's true for a car 1995 or earlier, but it might not be. I know you can't do that with a 1996 or newer vehicle, with the OBD-II. Heck, XMS can't even crack the computer code to program in their supercharger!

[timokon@yahoo.com]

FAstchip stops at 95, but for 95 or before, it's a great option, if you have the rubber (and suspension, the place, AND THE ABILITY / EXPERTISE) to support the speed.

Tim

[bigfoo]

If someone loaned me the equipment to mess with the code, i'd be happy to break it

[CaddyDaddy]

I believe that's true for a car 1995 or earlier, but it might not be. I know you can't do that with a 1996 or newer vehicle, with the OBD-II. Heck, XMS can't even crack the computer code to program in their supercharger!

What is XMS?? Maybe I code use this to crack my code.

[JasonA]

XMS is the outfit that designed and engineered the physical supercharger. They then found out, after building it, that they apparently can't "break in" to the Cadillac computer code to make the supercharger play well with the engine. I've heard all that through the grapevine...maybe someone else knows more details.

[bigfoo]

maybe I'll call them up and see if i can help

Anyway it's a lot more than just bolting something on. you also have to re-do the pcv and egr system and any other intake related things because the intake will no longer be negatively pressurized (vacuuM)

[JasonA]

Anyway it's a lot more than just bolting something on. you also have to re-do the pcv and egr system and any other intake related things because the intake will no longer be negatively pressurized (vacuuM)

Correct. If you caught a bit of sarcasm in my response referencing their project, I was merely surprised that they went through the ENTIRE engineering process, conducted pre-orders, and even have prototype systems running, but they can't "complete the sale" if you will. I guess I would have assumed that they'd have made sure before setting out that all obstacles would be easily tackled. I realize that designing a project like this from scratch is an enormous undertaking, but computer programming is not insignificant, and falling short at the 90% stage because you can't crack the code...just seems odd to me.

[MARK 99STS]

Jason,

I talked to Bob at XMS and he said another company was working on a super charger for the CTS and have not been able to crack the code after working on it for three months.

Bigfoo,

You might want to give Bob a call at XMS if you know anything about hacking into computer code as I know he is very frustrated at this point.

[bigfoo]

I already emailed him If I crack the code, i expect a big discount on the supercharger :>

[MARK 99STS]

I hope somebody can crack the code as I have been waiting on that super charger for 2 yrs now. Desperately want to get into the mid to low 13's at the track.

[bigfoo]

Hehe.. well I'll put a little time into it. If it's a money maker I can put al ot of time into it I wish I could even get your time without a superchgarger.. you must be very lucky, or have an extremely fast 0-60 foot time

My next mod is to cut out everything in front of the cat and replace with better stuff.. the pipes are all weird and not bent very well etc..

Then probably msd ignition. I still don't have a good enough intake setup for my K&N cone. I want to cut out the fender so the cone is actually inside the fender well

[JasonA]

I talked to Bob at XMS and he said another company was working on a super charger for the CTS and have not been able to crack the code after working on it for three months.

Amazing! It seems to me that the design charette would/should go something like this:

Boss: "What are our main obstacles?"

Engineer: "Well, sir, probably physically fitting it in the engine bay and hooking it up to the computer. You've got the physical side and the electronics side."

Boss: "Okay, how are we going to accomplish the physical obstacles?"

Engineer: "Sir, we have a very competent and capable machine shop. I guarantee you that we'll be able to package it in the engine bay with room to spare."

Boss: "I see...and what about the electronics?"

Engineer: "I'm not sure to be honest, we've never worked on a Cadillac project before. I'll be in touch with the good folks up at GM to make sure we'll be able to integrate this project with the computer and make it run well."

Boss: "It sounds like we're not too confident on the electronics side. Let's confirm that we can make this thing play well with the computer system on the car before we invest a lot of money into the project and take a bath on this. I don't want to fully develop this thing without making sure we can meet and beat one of the basic obstacles."

But then again, what do I know, I'm just a dumb ol' kid. I say all that with the benefit of hindsight of course, but it still seems obvious to me that you would spend some time brainstorming and planning before setting out on this, and I can't believe that with the current state of this art, they just "forgot" about making sure the computer is programmable!?

[ojaieldo]

Would an XMS chip do anything for a '94 that's already Z-rated?

[bigfoo]

Of course the computer is programmable.. about on the same level that you could change the code on a Cisco router. Think of it this way..

A regular computer, boots up the OS and then boots you into some sort of console, either graphical display or whatever and you can go in and do whatever you want. The computers in things like routers/PCM's and other of 'those type' of devices boots up the OS and there is no graphical interface or anything even remotely like it. The OS has all the settings built in to it and that's it. On the older cars the OS booted and then settings were read from a PROM chip which you could change fairly easily. On the new ones it just boots os from flash and that's it, all the settings are there. Now, I'm not sure if it has a large RAM capacity where it boots the whole os in RAM with the settings in RAM also. If so, one could, after the os already boots, make changes in the RAM areas to where the settings were. Or, one could edit the binary os fine if you could find the settings by major trial an error since you can't decompile it. If we could simply get ahold of the source code for the PCM software from GM, it would be VERY simple to make it do anything you wanted to do (provided the cpu power exists for it). I could make it play a tune on the fuel injectors while using the air pump for some bass and modulating some of the hvac stuff for fun.. wouldn't that be cool.. press a button and the car plays a tune :> We made floppy drives on the computers play tunes by oscillating the head very fast in different frequencies

[KevinW]

We made floppy drives on the computers play tunes by oscillating the head very fast in different frequencies

Hey, if you want something similar to your Commodore 64 and 1541 floppy disk drive, stick to the early '90s and older ECM/PCMs. My '88 Brougham has a 6803.

[JasonA]

Of course the computer is "programmable", but actually writing meaningful code that will work with the rest of the software is obviously another story. I'm sure it's much easier said then done...otherwise it'd have been accomplished by now.

[MARK 99STS]

I wish I could even get your time without a superchgarger.. you must be very lucky, or have an extremely fast 0-60 foot time

I picked my day as far as weather, humidity,temp and pressure for the ideal conditions. I also had slicks on the front and light weight aluminum wheels all around. I had no wheel spin which is where you lose most of your time and yes I am lucky that my car seems a little faster than average.

[Bruce Nunnally]

First, I think that GM went to unusual measures to prevent reverse engineering of the 96+ Cadillac PCM in order to protect the new stabilitrak and similar technologies. These are computer algorithms that provide competitive advantage and were worth some time preventing easy access.

Second, re-engineering firms who is the past had success with the LT1 or LS1 or 4.9L Cadillac PCMs believed that they would have similar success with the Northstar PCM. They made promises and calendar dates that they were not able to keep. So my perception is that when the supercharger project went forward it was with the support and confidence in these expert, professional firms that they would meet the dates they promised. They did not. Not the first, second, or third company that promised.

Third, GM/Cadillac has opted NOT to support third party revisions to the code, perhaps in order to protect the proprietary coding, perhaps because they don't see an advantage to a Northstar performance aftermarket.