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Bonneville GXP/ Northstar Powered Cars Discuss your Bonneville GXP and/or any other Northstar powered Olds or Cadillac... Including the 3.5L Twin Cam V6 (Short Star ) 4.0L and 4.6L Northstar V8's. Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 01-26-2010, 09:34 AM   #1
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Default Cooler Thermostat...Good idea? / Bad Idea?

Anybody know if the factory (since we can't seem to have them changed) PCM program settings will accept a 180* thermostat without causing any SES lights?

I'd like to get the temp down from the 195* it is currently.

All of my past vehicles seem to get better gas mileage and more power with a cooler stat.

Anyone tried it on the Nortstar?

Thanks,
Ken
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Old 01-26-2010, 11:00 AM   #2
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The Northstar PCM will alter settings to keep the temp @ 195-200. I think you will only accomplish wrecking performance and end up wasting gas. Your other engines did not have a PCM with so many ways to tune on the fly. It will alter timing/fuel~curve to get what it wants. And if it can't, it will try it'* hardest to do so and you will get codes thrown.
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Old 01-26-2010, 11:13 AM   #3
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This whole PCM limitation thing is getting REALLY annoying.

I did think of something else that I would like to explore. In the Cadillac forums, they have been discussing the use of an LS1 PCM to run the Northstar.

I have a little different idea.

I verified the Grand Prix GXP uses the same physical style of computer as the Bonni. (Different part number but same physical appearance and connector style, meaning a programming change, not a wiring change)

My question would be if the programming for a N* could be combined with the DOD (Displacement on Demand) programming from the GP GXP?

Could you immagine if we could not only improve the performance of the N*'* like they do for the '00-'03 and '06+ applications, but include DOD programming for a HUGE improvement in gas mileage.

The N* is already capable of running with dropped cylinders. It uses a severly detuned version of cylinder dropping for "camel" mode in the Cadillacs. (engine can be run 50 miles at 50 mph with NO coolant in the system).

The injectors are controlled individually as are the spark plugs (coil on cylinder).

GM'* already worked out the programming, now all we need is to find someone capable of putting two together.
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Old 01-26-2010, 11:30 AM   #4
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I cant help you on the computer swapping, but if you can find the engine temperature sensors and. . . i think. . .. add resistance to signal a higher temperature to the computer, then you could lower the overall temperature of the motor.

But I agree with Venom, with the N* it will hurt more then help.
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Old 01-26-2010, 11:39 AM   #5
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Quote:
Originally Posted by Kersh View Post
This whole PCM limitation thing is getting REALLY annoying.

I did think of something else that I would like to explore. In the Cadillac forums, they have been discussing the use of an LS1 PCM to run the Northstar.

I have a little different idea.

I verified the Grand Prix GXP uses the same physical style of computer as the Bonni. (Different part number but same physical appearance and connector style, meaning a programming change, not a wiring change)

My question would be if the programming for a N* could be combined with the DOD (Displacement on Demand) programming from the GP GXP?

Could you immagine if we could not only improve the performance of the N*'* like they do for the '00-'03 and '06+ applications, but include DOD programming for a HUGE improvement in gas mileage.

The N* is already capable of running with dropped cylinders. It uses a severly detuned version of cylinder dropping for "camel" mode in the Cadillacs. (engine can be run 50 miles at 50 mph with NO coolant in the system).

The injectors are controlled individually as are the spark plugs (coil on cylinder).

GM'* already worked out the programming, now all we need is to find someone capable of putting two together.
If you can figure out another PCM to run the northstar, by all means let us know. I'm pretty sure there are a LOT of people here who would love to tune their cars themselves.
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Old 01-26-2010, 11:52 AM   #6
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It is really annoying but not something thats suddenly going to have a easy/inexpensive fix.

It isnt the computer, it'* the memory thats burned into the ROM. The program is finely tuned and so many variables that work with each other. Because of the finesse and dependency of how the sensors work with each other, altering anything is going to put it into a tizzy. Dealers can't even alter the program. If a PCM falters, you replace it.

Your not going to run our LD8 with a LS1 PCM unless you can replicate the original program and have vast engineering/computer knowledge to reset all sensor interactions as you start tweaking. People like Chrfab of Cali, or Mallet Cars can fix you up with a Magnetti Marreli PCM and do such. I spoke to Mallet years ago. Drop the car off for 2 weeks with 5 g'* in hand and they can fix ya up.

DOD is a bad idea for aluminum blocks, which has been pointed to by many as a primary cause of localized heat and head warpage and snapped head bolts common to pre 2004 NorthStars with DOD.

The limp home mode is not a "severly detuned" version of anything. It uses ignition and fuel controls programming like DOD, but from there they go totally different paths. The limp home mode program is in fact much more complicated and allows 4 opposing cylinders, switching off alternately with the other four to fire one cycle, flush air without spark/gas the next. On a side note here, I have talked to several GM Service Techs, one Manager, who say more than half the engines run in the limp home mode suffer moderate to severe head damage anyway. They just never run right again.
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