Stage 2 accessport boost and elevation?

[sperry]

Originally Posted by knucklesplitter

I think this is only true for some. If you have a stand-alone boost controller (manual or electronic) or UTEC in closed loop (I think), then your boost builds to whatever the setting is despite the elevation (assuming the turbo can boost that high in that air). Somebody correct me on this if they know for sure, please. I need to drive down to Sac. to see how my UTEC boost varies for myself.

When I was running a MBC (back in the UniChip days), every time I went to the bay area I'd overboost like a madman. But up at altitude I was rock solid at 14.5 psi.

The ECU + stock EBC seems to do a pretty good job of reaching target boost at altitude, but I believe it's at the cost of turbo efficiency. The difference between a cool 14.5 psi and a hot 16 psi is probably negligable, or worse, faster at lower boost if the ECU has to pull timing to prevent knock on a hot motor. Remember, the stock WRX intercooler is pretty small.

And 17.5 psi on a stock WRX turbo! That sounds out of the turbo's efficiency range at any altitude! I hope that's tapering to about 13 psi at red line, or you'll probably end up with a motor like mine: on the floor of a shop somewhere!

[ddub]

How much for the seal? Speaking of boost, 17-17.5psi at 4500ft is probably pretty safe. I know a person who was pushing 19psi with only exhaust. You probably understand that the more boost you pump into your engine, means the more force you are putting on you pistons and seals. So you are defenitly wearing out the engine faster with higher boost, which is why I am satisfied with 14.5 psi at 4500ft.

[GST Mike]

Originally Posted by ddub

You probably understand that the more boost you pump into your engine, means the more force you are putting on you pistons and seals. So you are defenitly wearing out the engine faster with higher boost, which is why I am satisfied with 14.5 psi at 4500ft.

That is only the case if the turbo actually can push more, given the stock turbo size on a WRX it wont be pushing much more than hot air past 16psi at sea level, at 19psi at altitude you might want a catch can installed on the actual turbo....

[cody]

Originally Posted by ddub

How much for the seal? Speaking of boost, 17-17.5psi at 4500ft is probably pretty safe. I know a person who was pushing 19psi with only exhaust. You probably understand that the more boost you pump into your engine, means the more force you are putting on you pistons and seals. So you are defenitly wearing out the engine faster with higher boost, which is why I am satisfied with 14.5 psi at 4500ft.

It retails for $20 shipped. How about $15 and you pick it up. I live downtown reno.

Wouldn't you say that a better gauge of how much extra wear and tear the motor sees is your max power output? I mean, I never really thought that the stock turbo could put "excessive" wear and tear on the engine as long as you aren't detonating or running lean. Any upgraded turbo will push more CFM than the stocker which I think translates to more pressure on the internals. Correct me if I'm wrong.

I've heard anthing over 15 psi on the stock turbo and your just blowing hot air, but that's just one person's opinion. Blowing hot air just means a less Oxygen...not necessarily more wear on the engine right?

[knucklesplitter]

Originally Posted by sperry

When I was running a MBC (back in the UniChip days), every time I went to the bay area I'd overboost like a madman. But up at altitude I was rock solid at 14.5 psi.

Hmmm. Now I'm really curious how my boost will change at sea level with the UTEC. My turbo's not stock, and it's plenty efficient well above 20psi, so a little overboost would be okay prolly. I've had the car for almost a year now and haven't had it lower than 4000' elevation. I've never noticed a boost change going up as high as 10k'. Hmmm, maybe it's time for a spirited run up Mt.Rose Hwy to see what happens.

[GST Mike]

Originally Posted by cody

I've heard anthing over 15 psi on the stock turbo and your just blowing hot air, but that's just one person's opinion. Blowing hot air just means a less Oxygen...not necessarily more wear on the engine right?

The wear would be more on the turbo I would imagine than the engine from the stock unit but the fact that after about 16psi or so it's only blowing hot air is not really someone's opinion it can be proven fairly easily.

[sperry]

Originally Posted by cody

I've heard anthing over 15 psi on the stock turbo and your just blowing hot air, but that's just one person's opinion. Blowing hot air just means a less Oxygen...not necessarily more wear on the engine right?

The problem w/ running a turbo hot is not that you're putting more pressure on the motor's internals so much as you're asking the car not to detonate on a higher temp intake charge.

The hotter the intake charge, the easier it is for the car to pre-detonate when the pistons compress that A/F mixture. That's why we use intercoolers, water/alcohol injection, etc. Gotta get the intake charge as cool as possible, so we can compress as much oxygen as possible to make as much power as possible. If the air is so hot that the car starts pinging, then the ECU has to pull timing to protect the motor, in which case you may be running a ton of boost, but making less power because of the retarded timing.

[sperry]

For those of you that missed the post, take a look at what Mike Shields had to say about tuning their rally car for the Pike's Peak Hill Climb:

http://www.seccs.org/forums/showthre...ght=pikes+peak

There's some interesting info in there about turbo efficiency and altitude.

[cody]

Originally Posted by sperry

The problem w/ running a turbo hot is not that you're putting more pressure on the motor's internals so much as you're asking the car not to detonate on a higher temp intake charge.

The hotter the intake charge, the easier it is for the car to pre-detonate when the pistons compress that A/F mixture. That's why we use intercoolers, water/alcohol injection, etc. Gotta get the intake charge as cool as possible, so we can compress as much oxygen as possible to make as much power as possible. If the air is so hot that the car starts pinging, then the ECU has to pull timing to protect the motor, in which case you may be running a ton of boost, but making less power because of the retarded timing.

That all makes sense, but if you're car is tuned correctly, you should never ping...unless the IC is heat soaked or you get a bad tank of gas.

[GST Mike]

Not sure how you would be tuned for the excessive charge air temps when pushing the turbo that hard though.

[cody]

dunno, the car feels strong and shows no sign of detonation. I wish I had a knock indicater, but I don't.

[Kevin M]

Originally Posted by ddub

18" Rota subzero's, 225/45,
I have a minor exhaust leak from the turbo to DP, that has probably been there since I had it put on. However, It looks like I am getting full boost. Today on my way to work, in 4th gear I hit .1Mpa. Do you think the exhaust leak has any effect on the performance? Since I am reaching full boost, Does that mean I am getting the most HP? Nate said that you could take the DP off and still get full boost. If you took the DP off(no exhaust), How would that effect HP?

18" Rotas? 225/45R18? Damn, that's a taller, heavier combo than stock, and is actually lowering the amount of power you put to the ground unless Nate specifically altered the dyno software settings to compensate.

A post-turbo exhaust leak only makes noise, it doesn't affect performance much, unless it's a gigantic leak that actually reduces backpressure.

[Kevin M]

Originally Posted by cody

if you're car is tuned correctly, you should never ping...

That is correct, however, tuning it not to detonate (or worse, pre-ignite) means less power at higher boost levels. If tuning "correctly" could compensate for pressure ratios outside of a given turbo's efficiency range, there would only be one turbo on the market for every application and we'd all be pushing 45 psi through it and making 500 whp.

[cody]

So then the question is, am I making les power at 17psi than I would at 15 psi, because my tune has to defend against detonation?