VaporTrail

So, a very simple question

how do you determine wastegate size for a particular setup? Is there a formula that I've missed somewhere all these years?

Etylorcen

What do u mean size? Size of the spring?

ezark

i think he is referring to : 35mm , 40mm, etc.

VaporTrail

exactly

Arturbo

You know that is a very good question. I remember the Tial 35mm was used on so many high hp cars in the late 90's and I never really knew why a larger wg was needed. I mean if the manifold design is good, then why use a large wg? I do not know the answer to this..

art

Flamenco-T

35mm, just because it's cheaper, plus manifold with 35mm flange is cheaper as well, but then again, that's asian philosophy hehehehehe

JK John , I have no idea....

I am as clueless as the Riced up TRD'ed Celica dork that came in to my work on daily basis...

Stan

VaporTrail

well thank you for the bump. Somebody must know

lucas569

i thought the 35mm tials could go up to 18psi? dunno where i got that from, but from what im thinking the a bigger wg would perform better/effectively at higher boost levels, kind of like the bigger orifices of the aem fpr.

btw im just talking out my ***, but it makes sense to me.

VaporTrail

Tial has springs for up to 1.5 bar last I checked...so that cant be it

Mase

damn it.....you got me thinking way too much on this one. Give me a day, I'll have a reason.

Arturbo

Im assuming it has to do with pressure and how much a wastegate can release per squared inch. But mase, lets do think about this one and maybe would both can come up with something.

art

MackSpeed-616

ok, well if thats the case, 35mm>1.5 bar

Kamin

you know i was thinking the same thing last night wondering if i need a 40mm one..
huh..
bump.

DSF

Hehe, I just Viren for his recommendation. Of course usually that's a bad idea because I end up buying more parts

Mase

Give me a little time, Im going back to jville and going to the Jags vs Bucs preseason game today. But im sure it has to do something with pressure vs flow.

RGAZ

How about this:

As the displacment and rpm of the engine is increased, the cfm available to turn the turbine increases and as the boost reaches equilibrium the WG must be able to bypass a larger amount of flow to prevent boost creep. Thus a larger opening is required.

Sound feasible?

Randy

Mase

Thats a good start

CovertFI

the more hp you produce the more waste you will produce. i would assume the 35mm will handle up to about 400 anthing over that will require a larger wg. you can also figure it out this way if you are some MIT grad in machinacal eng. figure our how much your engine can take in and how much it can exhaust, then figure out how much exhaust gasses it will take to bring your turbo up to your target boost, and then figure out how much waste you have. you will want a wg what will flow a large around of exhaust gasses at a low pressure, if you get a higher pressure comming out of your wg then boost spikes can be expected.

if any one sees any thing wrong with this (other than spelling) please correct me

ricodemus

I'm with that. Bigger is better here, as the larger wastegate has the ability to release the excess gas faster, preventing boost spike better than the smaller wg.

Farnsrocket

I was thinking about this a week ago...I am glad someone posted this. I agree that a bigger WG will allow more excess to leave faster and prevent boost spikes........the question I have is what is the max hp my 35mm Tial handle?

Ash J. Williams

bingo, randy! think of it as the size of the turbo, both small and big will do a certain PSI, but the bigger one will do it more effeciently. smaller WG will cause boost creep. my opinion is to go with the biggest one you can and get spring PSI you want.
stan

Mase

I wouldnt say thats the best solution, Give me a couple days, ill have a good post coming.....unless art beats me

92SiTurbo

i have a tial 35mm and the other night i hooked up my profec B boost controller and turned it up to almost 1 bar. Car was running good then all of a sudden it was like i hit a wall at 5,000 rpm. It started doing it the next day but at 4,000 then at 6,000. I disconnected the boost controller and ran it through the wastegate which was about 5psi and runs very strong. I'm wondering if maybe something to do with wastegate or if the spring is not the right size. Sorry if this has nothing to do with the topic. I just want to be able to run more boost.

Arturbo

Feasible, yes. But there is more to it. there has to be some sort of formula that can be derived by displacement, cfm, pressure, and the diameter of the wastegate. Now i have something I can kill time with at work.

art

Mase

Even though I should be in bed. I couldnt let Mr Arturbo outshine me first....so here is a little something to get the ball rolling (mind you its 4:28am my time) :

Maybe some variables of importance:

PE = Turbo Inlet Pressure (the pressure in the turbine housing, essentially exhaust back pressure)
PI = Intake Manifold Pressure (the boost pressure)
AD = area of wastegate actuator diaphragm
AV = area of wastegate valve on turbine housing
FS = force of wastegate actuator spring on diaphragm (pushing wastegate closed)
FV = force on the wastegate valve due to PE
FD = force on wastegate actuator diaphragm due to PI

Formulas:

In order for wastegate to open: FD + FV > FS , where F = P/A and A = PI*(d2/4)

There are more assumptions, but dont wanna list right now. im tired, I just had to put out something cool before arturbo beat me

This in now way is a fact.....just diggin up some ideas.