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Discussion Starter #1
I've read that the SC N* has a 9:1 compression ratio, and I'm wondering what's usually a safe level of boost for a factory FI engine?

Assuming the combustion chabers in the SC N* are as efficient as those in an LSx engine, if you put 93 or 94 octane fuel in the car what amount of boost can a 9:1 factory engine usually take? I think the SC N* have a very solid bottom end but I don't know what they're using for the crank, con rods and pistons.

It seems like GMPD built a large amount of dependability into the engine becasue the went from 440HP to about 470HP without a problem, and I'm sure they expect the engine to last for over 100,000mi if it's properly maintained. Do you think it's maxed out at 470HP, or is it good for 500, 550, etc? (the heavy duty 6spd auto are rated @ 500Hp and I think they're rated @ 500lb-ft of torque as well)
 

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The 440 to 470 HP jump was due to the new SAE rating system. That's why the new DTS is rated at 291 HP, not 300 like the older models. With the new rating system, the N/A Northstar lost power!
 

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Discussion Starter #3
caddydaddy said:
The 440 to 470 HP jump was due to the new SAE rating system. That's why the new DTS is rated at 291 HP, not 300 like the older models. With the new rating system, the N/A Northstar lost power!
That's strange, because the NA Dodge Viper V10 picked up 10HP and I think the LS7 did as well. However, neither of those cars are close to the 30HP gain for the STS-V, some of the gain must be attributable to induction and exhaust changes (that's why the XLR-V makes less HP, it's around 443HP).
 

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It does seem to be pretty standard practice to increase boost with pulleys these days.. If the computer can be figured out, I am sure it will be 500hp very soon. Boost with warranty.
 

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Discussion Starter #5
Dooman said:
It does seem to be pretty standard practice to increase boost with pulleys these days.. If the computer can be figured out, I am sure it will be 500hp very soon. Boost with warranty.
I don't know of a tuner that can tune a N* vehicle. I think it's an adaptive program comapred to a closed loop program like the LSx series of engines (I hope the program isn't smart enough to pull timing in order to offset an increase in peak boost pressure.). I'm probably wrong but I know I heard that somewhere.

If we can't mod the computer / tuning what would happen if someone made a small pulley change?

Also, to my fellow CTS-V forum members... I'm going to test drive the STS-V before I make my decision on getting an '06 CTS-V. :getaway:
 

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Discussion Starter #7
caddydaddy said:
I'm so jealous! :crying:
Thanks Caddydaddy.

Also, I just read my post and I realized that it could be misinterpeted. I just wanted to let you guys know that I'm looking forward to test driving the STS-V, and I'll post a review with pics after I get a chance to drive it ( I'll probably buy it ). :thumbsup:
 

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caddydaddy said:
The 440 to 470 HP jump was due to the new SAE rating system. That's why the new DTS is rated at 291 HP, not 300 like the older models. With the new rating system, the N/A Northstar lost power!
Actually, the boost in HP in the STS-V was due to intake changes made before the HP was validated. If it were solely the result of the new test, the XLR-V would have seen a similar jump.

The "300"hp Northstar that was used in the 2000-2005 DTS was always putting out 290hp, while the same engine in the 98-2003 STS was truly acheiving 300hp, due to different intake design. Under the old SAE rules, GM wasn't required to validate the engine in the DTS since it was the same as the STS, hence they marketed it as 300hp. In 2004 when the STS ceased to be, Cadillac had to strap a DTS engine on a dyno, and the rating was officially changed to 290 hp (what it always had anyway).
 

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Tony Orlando said:
Actually, the boost in HP in the STS-V was due to intake changes made before the HP was validated. If it were solely the result of the new test, the XLR-V would have seen a similar jump.
There is very little difference between the "intake" on the STS-V and XLR-V... Other than the different bend in the induction tube front half the rest of the system on the engine itself is identical.


The power difference between the two is due to the more restrictive exhaust manifolds on the XLR-V (tighter packaging in that vehicle) and the shorter oil pan on the XLR-V causing extra windage loss (once again, tighter packaging and the engine is lower in the XLR-V). It has nothing to do with the SAE power test procedures and "intake" differences. Using the old test, there would still be a significant difference between the STS-V and XLR-V power ratings. The intake restriction (from the air cleaner and ducting) is very similar and VERY low on both cars. Same for the exhaust system...within the constraints of the passby noise requirements the exhaust backpressure is very low.


The change in the SAE power test procedures affects different engines in different ways. The comparisons being used are not really valid because normally aspirated engines are affected differently than supercharged engines and differently than intercooled supercharged engines.... You have to understand the specifics of the test procedures for any given engine and application before and after the SAE test procedure was changed to understand whether it will increase or decrease power. There is no single explaination that covers all cases and all cases are NOT comparible.


In general, however, the new procedure will cause a decrease in the advertised power if the manufacturer was "cutting corners" to get a high number....or it will cause an increase in the power if the original power tests were somewhat conservative in relation to what the new SAE test allows.


In the case of supercharged engines with intercoolers the old test allowed the manufacturer to pump ice water thru the intercooler to get a good number...not exactly representative of consumer use. The early power tests with the Northstar were done with hot intercooler circuit coolant to simulate worst case, continuous operation under maximum boost in a hot climate. Correcting for transient acceleration conditions on an 80 degree F day that the new test specifies actually allowed much cooler intercooler coolant and raised the power level significantly for the test which accounts for the change in the power rating from the preliminary numbers leaked out earlier.


There was a lot of "interpretation" in the test requirements previously that has been eliminated and specified in the new test. In addition, an SAE representative witnesses the actual power tests to certify it was conducted per the new procedure and is representative of what the consumer will experience. This takes a lot of the monkey business out of the rating. European power ratings have required a "witness" for many years. Now the same is required if the manufacturer wants to claim the "certified" power rating.


For what it's worth....consider the fact that the STS-V engine is making well over 100 HP/liter as it comes from the factory. It is NOT going to be easy to get more power out of it as all the "low hanging fruit" has already been picked. The drive ratio for the supercharger is already pretty well max'd out (it already has the "smaller" pulley..) so be careful.... If I was going to go after something for power I would consider a lower backpressure exhaust system as the engine loves to breath......


Consider the fact that the STS-V engine is actually making about 540 HP. It takes about 70 Hp to drive the supercharger at peak output so the engine "only" outputs 469 as measured at the crankshaft. But it is still flowing 540 HP worth of air, fuel and exhaust thru the engine at peak output so as to maintain the 469 at the crank AND drive the supercharger. So....the intake system, the fuel system and the exhaust system is actually being taxed significantly MORE than the 505 HP LS7 engine. Think an exhaust might help....???
 

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Discussion Starter #10
Thanks Chevelle,

Now it looks like a CAIK and a higher flowing exhaust is about all that's left to be done, unless you want to put a ton of money into the engine. It's too bad the N* was shrunk to 4.4L, and the funny thing about it is the Euro engines are now the "tanks". At 4.4L the N* is giving up 1L to the M5's V10 and nearly 2L to Mercedes new V8.
 

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That was really helpful

thanks

The next thing they need to do though is to come down on all the aftermarket tuners ridiculous power claims. I can't tell you how many 400HP Mustangs or Japanese cars that I saw that couldn't even break 13.5 in the 1/4

I saw one RSX that advertised 525HP and ran 13.7

Pleaaasssseeeee
 

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When you see the air intake and air cleaners on the STS-V and the XLR-V you will realize that changing to any commercially available "cold air intake" will slow the cars down....considerably. The systems come with cold air intakes and air cleaner elements that flow considerably more than anything available in a pleated paper or gauze element. The elements are a new technology "power core" that have flow capacity well beyond any pleated element that is twice the size of the power core air cleaner. Both units are ducted straight to cold air so any mods in that area are going to be backing up. Plus, at the extremely high air flow rates there was a great deal of work done to make the MAF operate correctly with no restriction. Modifications to the flow path will cause the MAF to read incorrectly and that, too, will slow it down.

To get those power levels there were not any stones left unturned.

The exhaust still had to meet pass by noise levels, though....so.....

Hopefully the power claims will start to become reasonable with the SAE "certified power" rating. Any power claims that are not certified would be open for question so most manufacturers will adopt them I would hope.
 

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Discussion Starter #13
So a CAIK will be worthless and an aftermarket exhaust will be too loud.... It'll be interesting to see how much smaller we can make the pulley before it goes boom.

Chevelle,
Did you do some of the engineering work for the SC N* (sure sounds like you did)? Could you tell us if the engines internals are capable of handling more than 540HP (before the parasitic SC loss)? Would it just be a matter of using higher octane fuel to avoid detonation due to the increased boost?

Could you tell us what the boost level is on a SC N*, and how much more is needed for 500HP?

Thanks again.
 

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No, but I find out some stuff from a supplier on the project.

I think the boost is around 15 PSI at peak.

I think that the blower on the engine is pretty well maxed out from what I hear. Not sure if it is capable of 500 HP or living with a smaller pulley. I kind of doubt it.

The engine will respond to lower backpressure and very good gas, though. Keeping the intercooler circuit as cool as possible will help, too, so a spray bar on the intercooler radiator will be helpful, especially in hotter weather.
 

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Discussion Starter #15
chevelle said:
...The engine will respond to lower backpressure and very good gas, though. Keeping the intercooler circuit as cool as possible will help, too, so a spray bar on the intercooler radiator will be helpful, especially in hotter weather.
Thanks, There's a Sunoco on my way to work with 100 octane race gas. I think my V runs better when I have some of it mixed in with Mobil 93, so it'll be intersting to see how the STS-V responds (if I end up getting it).
 

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Vrocks said:
Thanks, There's a Sunoco on my way to work with 100 octane race gas. I think my V runs better when I have some of it mixed in with Mobil 93, so it'll be intersting to see how the STS-V responds (if I end up getting it).
Any idea when you will be test driving the V? I'm sure a review would be greatly appreciated by all. :thumbsup:
 

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Discussion Starter #17
ktills45 said:
Any idea when you will be test driving the V? I'm sure a review would be greatly appreciated by all. :thumbsup:
The car is scheduled to be built around December 12th. So there's a chance I won't be able to drive it until early January.
 

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""The exhaust still had to meet pass by noise levels, though....so.....""

So... A good company already making exhaust systems for the CTS And CTS-V would be smart to get the ball rolling.......
 
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