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LC3 rabbit hole

MPRCTCL

Seasoned Member
Joined
Apr 18, 2018
Messages
110
Location
Michigan
My XLR/V(s)
2008 Crystal Red XLR-V
So, I’m down the rabbit hole on this. My buddy has an ‘06 STS-V with the same engine as my V, but…. It’s rated for more horsepower. Has anyone sorted out the story? Was it a marketing thing? Component differences? Yesterday, I spoke with a Northstar engineer, but he’d left GM before the LC3 came about and didn’t have a good idea.

 

mickeytee

Seasoned Member
Joined
Apr 5, 2017
Messages
717
Location
North Atlanta
I think I read one time it was thought the belt drive system on the xlr combined with the exhaust resulted in lower HP. I personally think the supercharger does not turn as fast on the xlr as on the sts. The bigger power steering pump pulley that was sold aftermarket a while back supposedly bumped the HP up on the xlr. I found this from the guys that made the bigger pulley so it seems that was what the found also.


'Good question. Everything internally is the same between the two vehicles. The only differences you have are fuel map, exhaust system, and intake track. The fuel map change can be attributed to the change in exhaust between the two cars. The intake is just routing.

The 26HP is coming mostly from the exhaust (i.e. exhaust manifolds and tuning). The XLR-V exhaust manifold has a wicked kink in it, whereas the STS-V is a little bit better flow wise. We have developed headers for the XLR-V application and the vehicle REALLY RESPONDED WELL!! We did the same for the STS-V and the gains were good, but not as good as the XLR-V application.


p.s. Also there is a slightly different pulley track between the two engines. The XLR-V uses a 2 row pulley system whereas the STS-V uses a 3 row with its own blower belt. Dont want to leave out any details... =)
Hope that helps'
 

Z1.

Seasoned Member
Joined
Apr 11, 2013
Messages
162
Location
Fallbrook
My XLR/V(s)
2006 Raven Black XLR
GM decided to detune the XLR-V's HP a little bit in the ECU calibration for some reason. Table doesn't look as aggressive in fuel to air ratios. Maybe they did this to make though the warrantee period.
 

MPRCTCL

Seasoned Member
Joined
Apr 18, 2018
Messages
110
Location
Michigan
My XLR/V(s)
2008 Crystal Red XLR-V
I think I read one time it was thought the belt drive system on the xlr combined with the exhaust resulted in lower HP. I personally think the supercharger does not turn as fast on the xlr as on the sts. The bigger power steering pump pulley that was sold aftermarket a while back supposedly bumped the HP up on the xlr. I found this from the guys that made the bigger pulley so it seems that was what the found also.


'Good question. Everything internally is the same between the two vehicles. The only differences you have are fuel map, exhaust system, and intake track. The fuel map change can be attributed to the change in exhaust between the two cars. The intake is just routing.

The 26HP is coming mostly from the exhaust (i.e. exhaust manifolds and tuning). The XLR-V exhaust manifold has a wicked kink in it, whereas the STS-V is a little bit better flow wise. We have developed headers for the XLR-V application and the vehicle REALLY RESPONDED WELL!! We did the same for the STS-V and the gains were good, but not as good as the XLR-V application.


p.s. Also there is a slightly different pulley track between the two engines. The XLR-V uses a 2 row pulley system whereas the STS-V uses a 3 row with its own blower belt. Dont want to leave out any details... =)
Hope that helps'
Thanks for the great reply. That makes complete sense. It also helps me stay grounded, I want to do some upgrades, but they are hard to acquire and if the exhaust manifold is the (literal) limiting factor, "more air in" has a very limited potential if air can't get back out.
 

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