wastegate hole size vs. spoolup

[1987BuickGrandN]

i've herd people say...

spoolup is affected by wastegate hole size.

why would the wastegate hole size affect spoolup???

if the wasegate is completely closed durring spoolup

and open durring a set manifold pressure (to relieve gas/pressure/decrease or maintain boost)

why would having a hole thats too small affect spoolup??

i could see how having a hole thats too small and not allowing enough gass to pass through/still creating thrust(i.e. boost creeps/manifold pressure still increases)

but...not spoolup

am i correct in this assumption?

also...

if i have an adjustable wastegate

as boost increase.... the wastegate rod will push further out and uniformly/steadily open the wastegate...as boost increases

if this is the case

an ideal situation where the wastegate is completely closed durring spoolup cannot be achieved

hence the need for an electronic boost controller or wastegate silenoid (as implamented in the GN)

i.e. to open the wastegate (all at one time, not incramentially) after spoolup to alleviate excess manifold pressure

 

[strikeeagle]

You sort of answered your own question.

There are lots of ways to control boost. Buick chose a particular way, perhaps less sophisticated than is available in the aftermarket.

Depending upon the level of sophistication, the wastegate may not be entirely closed during spool-up.

In a perfect world, the wastegate would remain closed until the desired boost level is reached, and would then pop open and hold the desired boost level - rock steady.

In the real world we're dealing with a very dynamic situation, which we are trying to control with somewhat cheap, someone rudimentary hardware.

Spool-up is affected by wastegate size to the extent that the wastegate is open during spool-up and different size wastegates have their own associated dynamics. Analogy - ever pump up a bicycle tire using a gas station compressor? Well, it's not quite the same dynamic as using a hand pump, is it?

 

[1987BuickGrandN]

Thanks for the reply.

I think i get the basic concept.

I just bought a reatively large turbo im trying to minimize spoolup time

"Spool-up is affected by wastegate size to the extent that the wastegate is open during spool-up"

is it possible to eliminate the wastegate from opening at all durring spoolup? i like ideal worlds!

i dont see why an electronic boost controller couldnt keep the pressure on the wastegate actuator low enough so that the rod doesnt extend and the wastegate stays closed durring spoolup

then afterspoolup ...at desired manifold pressure start regulating the wastegate actuator to control manifold pressure.

Thanks,

Bryan

 

[Adrian87]

Seems like that's how it should work!! Someone tell us what's up! You're on the right track, keep going!

 

[1987BuickGrandN]

Adrian87:

your setup looks very similar to mine

i have an art carr 9" 3200 stall non lock up converter

a PT61 P-Trim instead of a 62

ATR 3" dual exhaust

Im shopping for a front mount intercooler and injectors to finish off my combo

How do you like those 57s??

Bryan