M0J0

A supercharger helps you no more than a NA motor since the amount of air forced in is static because it is on a belt. The only way to change it is by changing the size of the pulley. This is why I am thinking about doing a tune/pulley mod to get back that 95HP. Turbochargers should make up for most of the O2 loss, but there will be considerable turbo lag.

smacky

Wow, that's up in the mountains. Didn't it would be nearly doubt Mile High.

M0J0

Yea, it will be quite an adjustment of driving. I am going from an M3 at sea level to a Q7 at high altitude. I am going to give it a month or so before I void an engine warranty for 90hp. The nice thing is engines rarely have issues. I have never had one in my lifetime. Knock on wood.

gsobol

That would only be true if the SC was undersized to provide limited boost pressure. 3.0SC utilizes both clutch plate and waste gate to regulate boost pressure. You are right, there is no way to spin the SC faster to produce more boost quicker (on oem pulley), however if the system is up-sized in the first place, it will bleed off excess boost at sea level, but will keep waste gate closed at altitude still providing you with some boost therefore outperforming NA motor. Both systems SC or turbo suffer from the problem of reduced available air at low RPM, however SC can deal with it a bit quicker (initially) since it's directly tied to engine RPM, turbo relies on the volume and speed of the exhaust gasses which are also affected at lower RPMs. Now, when you get to higher RPMs, turbo wins hands down since it can spool up at higher RPM and therefore can recover or achieve designed boost pressure. In order to achieve that with SC motor, it would have to be designed with high altitude operation in mind (such as aircraft engines), but that makes operation at sea level tricky as the engine would be over-boosted and it would require large waste gate.

Having said all that. I'm not sure how over, under or properly sized SC is in the 3.0 motor. Looking at some power curves and when bleed valve opens up it looks like the system does have some extra boost capacity. However, since it's roots type SC, so only about 40~50% efficient, I'm pretty sure there is a significant % of power loss at altitude, but I don't think it's as drastic as you think. Yes, there is no way to recover the lost power without some mechanical upgrades, or NOx. However any changes that would help you at altitude, could hurt your motor at sea level. So all in all, hey you were right, turbo would have been better in your case and location :-)

I love this theoretical discussion, but to be perfectly honest, the only way to know for sure is to put the car on the dyno at sea level and then at altitude. Anything else is pure speculation.

DB22

smacky

Double Mile High's elevation

smacky

I think I have read users say that the RaceChip won't trigger anything to void the warranty. If you go in for service, take it out, but if it throws codes, can't you just clear them with an OBD reader?