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Are you sure the cams aren't different? I thought I recalled them saying that they could make cams that produced more torque, or more power, but not both, which is the advantage of the new cam phasing ability on the next gen northstar (everyone else has had cam phasing for years now). Maybe it was just exhaust, but I was under the impression that there was an internal difference.

Scott
 

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Gen I Northstars are all the same. Gen II like the ones coming in the XLR and SRX will have variable cam technology. This is actually old news. Other manufacturers have been using it for a couple years. It allows one engine to benefit from multiple cam shaft profiles, which means good bottom end AND good top end.
Ain't technology a wonderful thing?
 

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i heard the difference between the 2 is due to more aggressive cam timing.


there are other difference between the two such as gear ratio, center console but main reason for the power difference is the cam.
 

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To be honest, I've heard that the engines are the same from some some people, and that they're different from the aspect of the cams from others. I've just never checked it out for myself.
I'm likely to believe they ARE different since they have their own VIN designation. One phone call to the dealer would certainly solve the issue. If the cams are different, the parts dept. would be able to tell you.
If it IS just the cams, then modifying the SLS to STS spec would be FAIRLY easy. I would warn anyone that hasn't done this type of work on a Northster to find out more about the procedure. There ARE some special tools needed, and you DO require some specialized knowledge.
 

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There's also some differences in the programming of the ECM and you must also take into consideration the gear ratio differences.
 

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The Touring variants (STS, DTS, etc.) have the L37 Northstar...the others have the LD8 Northstar. Discounting the new RWD blocks with variable valve timing, the two engines are exactly the same with one different -- the intake valves' camshaft profile. Higher lift and duration on the intake valves. This produces 25 more horsepower and 5 fewer lb*ft of torque.

Other differences in the vehicles is PCM programming and transaxle ratio. The L37 cars are mated to a 3.71:1 final drive and the LD8 cars have a 3.11:1 final drive. Other than that, the cars are the same. Same intake systems, same exhaust systems, etc.

Note that each engine has its own torque curve, and is matched nicely to that final drive ratio. In other words, if you put an L37 engine into an SLS, the result would not be as amazing as you think. The L37 makes less torque (and less horsepower across most of the rpm range) than the LD8...couple that with the SLS's 3.11 final drive, and you'd have worse performance than what you started with. Likewise, sticking in a 3.71 final drive transmission into an SLS (or DHS, etc.) wouldn't give you fantastic performance either because the engine would rev up faster than it's really designed to breathe at -- it would lose its breath as it revved up to fast.

They really are installed as a total package and changing one particular thing (like the cams) without addressing anything else will really turn your performance downhill.
 

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That's more or less what I was gettin' at but I was in to much of a rush to go into one of my famous marathon posts!
 

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Katshot said:
Gen I Northstars are all the same. Gen II like the ones coming in the XLR and SRX will have variable cam technology. This is actually old news. Other manufacturers have been using it for a couple years. It allows one engine to benefit from multiple cam shaft profiles, which means good bottom end AND good top end.
Ain't technology a wonderful thing?
One thing to note about the Cadillac system is that it can vary the cam timing on BOTH the intake and the exhaust camshafts. No other manufacturer has this on their engines to my knowledge. I think Caddy is a first there.
 

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jadcock said:
One thing to note about the Cadillac system is that it can vary the cam timing on BOTH the intake and the exhaust camshafts. No other manufacturer has this on their engines to my knowledge. I think Caddy is a first there.
i think vtec-i already does all that with sort of on and off switch mode.
There are quite a few cars that uses variable cam system.
 

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Devil_concours said:
i think vtec-i already does all that with sort of on and off switch mode.
There are quite a few cars that uses variable cam system.
Yes they use a variable cam system, but it only adjusts the valve timing on the intake valves. The exhaust cam is a fixed deal, like a conventional engine.

The new Northstar has two separate sets of variable timing mechanisms (well, four in total). There's a separate timing mechanism on EACH camshaft, meaning that both the intake and the exhaust cams' timing can be adjusted on the fly. This is not the case with any other vehicle.

However, I think BMW has everyone beat already. Their premium V8 and V12 engines use no throttle blade. The way they throttle the engine is by varying the LIFT on the valves -- so the engine is "wide open throttle" all the time, but if little air is required like at idle, the valves just crack open. I think that's pretty slick.
 

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jadcock said:
Yes they use a variable cam system, but it only adjusts the valve timing on the intake valves. The exhaust cam is a fixed deal, like a conventional engine.

The new Northstar has two separate sets of variable timing mechanisms (well, four in total). There's a separate timing mechanism on EACH camshaft, meaning that both the intake and the exhaust cams' timing can be adjusted on the fly. This is not the case with any other vehicle.

However, I think BMW has everyone beat already. Their premium V8 and V12 engines use no throttle blade. The way they throttle the engine is by varying the LIFT on the valves -- so the engine is "wide open throttle" all the time, but if little air is required like at idle, the valves just crack open. I think that's pretty slick.
irc, i-vtec does control exhaust well as intake.
 

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I couple years ago it was true that everyone was just varying intake. But now almost everyone is adding exhaust variability. BMW has "Double Vanos." I forget what everyone else calls it, but it's getting to be pretty commonplace. A lot of them are starting to vary lift now. BMW does that. Porsche does it with the 911. I think Honda even has a variable lift system in some car now. Don't worry...caddy is far from first with this system. That doesn't mean it won't be the best though. :)

Scott
 

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Discussion Starter #16
Thanks for the clarification between the two engines, seems like they are close to being the same. Why would Cadillac waste the time offering both?
 

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Ray89 said:
Thanks for the clarification between the two engines, seems like they are close to being the same. Why would Cadillac waste the time offering both?
or the same reason you used to be able to get different versions of 305s in firebirds. its more prestigious to drive the nicer one.
 

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There are a few reasons the 300 hp version is offered.

1) Marketing is a big reason. You need to have that high horsepower number for "brochure racing". The numbers mean a lot to some people, even though they may be meaningless in the real world.

2) The STS/ETC/DTS engine, the L37 engine...even though it makes less power and torque across the band than the LD8, it still performs better in the upper rpm range -- and because of the 3.71:1 final drive, should ultimately win in a drag race.

The LD8 engine makes more torque and power down low than the L37 does -- making it a perfect match for a large luxury car...and it returns great mileage. The LD8 is in fact the original design Northstar. Cadillac felt the need for the L37 to get that magic 295/300 horsepower figure...when paired to the 3.71:1 transaxle, it's a good drag racer.
 

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I think that Jason needs to check his figures. The L37 engine does NOT make less power and torque across the band. It makes MORE power and LESS torque. Plus the power band is only 400rpm higher. The comment about the L37 being "a good drag racer" is a little off-base as well. Horsepower may sell cars but torque wins the races. If it weren't for the rather substantial boost in gearing, the STS/ETC would be getting SMOKED by that base models with their "less powerful" engines.
I think your first comment was MOST accurate, it's about marketing.
 
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