What/why exactly does boost creep occur with a free flowing exhaust?
09-26-2003, 03:19 PM
#11
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too big a what?
I wouldn't think you could really go too large a wastegate (well, within practical reason). the wastegate is shut until it sees some pressure signal to open it.
Lag comes from the spool time on the turbo. You get lag when your exhaust gasses don't build pressure against the wastegate quickly enough to keep the turbo spooled.
Think of it this way - I have ten angry people trying to get through a door, and it only opens if all ten of them swipe their card key. If the door is made of paper (small wastegate), and those people are pushing to get through, they'll shove it open and go through (and you get boost creep, as the wastegate is ineffective). If I make that door larger and out of steel (bigger wastegate), I have a door that can only be opened if those ten people come up and swipe a card key. In each example, they queue up at the same speed (which means your turbo spool time is the same in each case).
The size of the door really doesn't matter, but how strong it is does.
This example obviously doesn't cover all of the possibilities, but it gives you a basic idea.
Keep the questions coming though, I'll be happy to go into detail about any of this.
Lag comes from the spool time on the turbo. You get lag when your exhaust gasses don't build pressure against the wastegate quickly enough to keep the turbo spooled.
Think of it this way - I have ten angry people trying to get through a door, and it only opens if all ten of them swipe their card key. If the door is made of paper (small wastegate), and those people are pushing to get through, they'll shove it open and go through (and you get boost creep, as the wastegate is ineffective). If I make that door larger and out of steel (bigger wastegate), I have a door that can only be opened if those ten people come up and swipe a card key. In each example, they queue up at the same speed (which means your turbo spool time is the same in each case).
The size of the door really doesn't matter, but how strong it is does.
This example obviously doesn't cover all of the possibilities, but it gives you a basic idea.
Keep the questions coming though, I'll be happy to go into detail about any of this.
09-26-2003, 05:02 PM
#14
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I think you mean it is how strong the spring in the actuator is not the wastegate itself.
This was a HUGE issue on the 2g eclipse, which could not hold more then 10psi even with the vac line removed from the wastegate actuator.
09-26-2003, 06:16 PM
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Those heated seats sure do feel good sometimes.
I am a fly fisher and there has been more than one October or November evening when I've come off the water with my legs and *** numb from the cold water and night air. Planting the ***** and buns into a seat set on (and I quote) "who needs a man" hot sure takes the edge off.
09-27-2003, 02:16 PM
#16
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Actually, it wasn't the actuator so much as...
the lame blow off valve that came on those cars stock. It leaked a ton.
If you modified the pivot on the wastegate actuator, you could get it to hold up to 18-19psi or so, but at that point the little T-25 was only blowing hot air anyway.
If you modified the pivot on the wastegate actuator, you could get it to hold up to 18-19psi or so, but at that point the little T-25 was only blowing hot air anyway.
09-27-2003, 10:08 PM
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The stock BPV was good for 15psi max, the stock wastegate actuator
could not hold more then 10psi solid even with the vac line removed. I replace both those stock part with a 1g stock bpv and a HRC upgraded actuator, my T25 has been running at 17-18psi for some time now. Too bad the stock T25 now needs to be replace since the seals are leaking, not too bad for 155,000 miles on it.
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