NLR

put a 5 psi spring in the wastegate and mount in to the compressor piping. It will open at 5 psi

ayousef

thats exactly what were debating, im being told that a 5PSI spring on a wastegate in the compressor side will open at 10PSI etc...

chriswtx

iTrader: (5)

thats right...a 5psi spring in a wastegate used with a supercharger on the compressor tube will open at around 10psi not 5psi...

NLR

LOL!!!.... If its got a 5 psi spring it in and your getting 10 psi the gate is either to small or is in a poor location . The biggest mistake made is just putting the wastegate where ever it fits. Practical location with very poor gate priority leads to the inability to flow the required amount of air to keep boost down. Wastegate size is important as well. Example: Putting a 38mm gate on a 30 psi supercharger application and expecting it to maintain 5 psi is ridiculous . To add to this having the gate mounted 90 degrees to airflow is a joke as well. Wastegate valve face should be facing oncoming airflow just like in a exhaust situation.

Shearer

Sebastian is correct.

Also have to throw this out there. The one guy in this thread is using a cheap China-Bay gate. Are you certain that is a 5psi spring in the gate?

SMOKINV8

iTrader: (6)

IMO, you guys are arguing over semantics here. Wastegates aren't made with superchargers in mind, so springs for them are rated as to how they perform on a turbo kit. A "5 psi spring" doesn't actually open at 5psi of pressure, it opens at the time it would produce 5 psi on a turbo setup.

No experience with a wastegate on a supercharger here, just theorizing. Seems like several people in this thread had instances where rated springs opened at double the pressure.

NLR

A wastegate will open when there is enough pressure on the lift side to overcome the spring. Doesnt matter if its on a turbo or a supercharger. Its a valve thats mechanically controlled by a spring and overcome by pneumatics.


Chances are those people either had too small of a wastegate or it was in a very poor location or the spring was actually a higher rating than they thought. This is not science fiction. Its fact.

ayousef

I wanna beleive what you say is right, but this is how im thinking:

5PSI in the intake manifold, the spring in a turbocharged car opens, the gases that go through the exhaust are much more than what just came from the intake manifold, there is the mixture of fuel/gas and alot of crap which means that INDEED a spring thats made to open at 5PSI of manifold pressure (FITTED ON THE exhaust of the car), is not meant to open at 5PSI if it were on the intake side.

But I hope what you';re saying is right though.

chriswtx

iTrader: (5)

correct...on a turbo setup for the wastegate to hold and open at 5psi it needs the spring to be able to hold 10psi of exhaust pressure, then when you see 5psi of intake pressure the boost pressure for in intake is used to help open the gate....remember on a turbo setup there is about double the psi of exhaust pressure as in the intake and the wastegate springs have to be able hold that exhaust pressure to make boost...

Shearer

To use that as a blanket statement is wrong. Exhaust pressure to intake pressure is dependent upon many variables(engine size, turbo choice, boost pressure, rpm, yada yada yada).

Wastegate spring rates are rated on how much pressure it will take to actuate the valve. The larger the valve diameter the less pressure it will take to actuate the valve for a given spring. It doesn't matter if it's on the exhaust, intake, or plumbed into your garden hose. Pressure is pressure.

sho-me speed

iTrader: (55)

So you are saying that a 5lb spring in a wastegate that is located on the exhaust side is 5lbs at the WG and not at the manifold? That doesn't make any sense as the pressure on the exhaust side is almost always greater than that of the pressure in the intake so using your theory 5psi at the WG would only net you somewhere in the 2.5 - 5 psi range at the intake depending on you pressure ratio of your particular set-up.

Shearer

Yes it is rated at the wastegate valve. Why would a manufacturer rate a spring for a given pressure based on a system they have no control over(intake)?

Have a look here...
http://www.tialmedia.com/documents/w3_tial_38_sp.pdf
It says assuming a 1:1 pressure ratio. Remember you words "almost always". I don't think I've ever seen a turbo engine at a 1:1 pressure ratio(or higher) at 5psi or 10psi intake pressure.

NLR

your thinking into it way to much...I am right. Trust me...I control the power on the quickest and fastest vehicles on the planet!

sho-me speed

iTrader: (55)

Good!!! So now we are getting somewhere. The WG will work on a supercharged application as designed because the spring is rated at the WG. On a turbo application most guys will actually have a larger spring than say a 10lb (ex.) because the pressure ration is not 1:1

The guys above arguing that the turbo wastegate would have to be doubled seem to miss the point that you typically run for example an 14lb spring in order to get 8-10 psi of booost because of the pressure ratio.

The suoercharged set-up will allow the WG to act as designed because the boost seen in the intake piping will be the same as what is seen in the intake (where everyone reads thier boost levels at.)

Louis

iTrader: (7)

Wow, Sebastian made it on here!! cool! What ever NLR says, its the truth, period. That dude is the man!!

sciff5

iTrader: (1)

Wow with a recommendation from Louis like that I already trust what NLR says. So in your professional opinion NLR do you think that adding a wastegate to a centri charged system actually creates more area under the curve and possibly faster track times?

I would think on the wastegate controlled lower pressure setting the blower will reach max psi quicker creating more area under the curve up untill that point and then from that point on in the powerband you would see more parasitic losses than without a wastegate control because your expending more power to spin the blower faster without additional air being fed into the engine.

Would love to know

The only guy on this board who has this setup (that I know of) I dont believe has gone to the track with it to test it out and feels that a 5psi spring will actually yield 10psi.

Louis

iTrader: (7)

I, personally, have no experience, but common sense tells me you can make more boost quicker, and then use the gate to control peak boost

Where Seb comes in is trying to control the big F2/F3 cars out of the hole, where they make 30+ psi, but cant put it to the ground off the line just like any other car.

2 different ideas and goals really. On the street, area under the curve makes the car more fun, at the track, too much of a good thing can be bad

ayousef

ive been thinking of this since soo long, but this is what im worried about:


imagine you want to maintain 5PSI throughout the RPM range, and make boost very low in the RPM range, you pulley the supercharger up to an extent it would boost to say 12PSI at max RPM (if it did not have a wastegate).

scenario1: 3rd gear pull from low-rpms, vehicle makes boost, and boost is mainted and regulated via the wastegate.

scenario2: driving at 55MPH, you downshift into 2nd, 5000RPMs, you MASH the throttle, the car will boost INSTANTLY before the wastegate has time to react, and all it would take is a fraction of a second at that high-boost level to blow ur engine up.

its different on a turbo set-up too, turbos no matter how small, give the WG ( through spooling and/or lag) enough time to work.

I might be mistaken, I HOPE I AM.

sciff5

iTrader: (1)

Prob need to get a good wastegate. I dont know if those synchronic wastegates are any good or just marketing BS but they have some vids on youtube of their response time and they sure seem to be able to actuate way faster than I could ever shift.

EDIT: Found the vid
http://www.youtube.com/watch?v=UBNTWoPe8yc

ayousef

its not about shifting really, its about you starting a race at a very high RPM, where the blower would normally do say 15PSI of boost, but you want that restricted to 5PSI, the blower would INSTANTLY boost to 15PSI, waay faster than the time it would take a wastegate to react to this change.

I think its very risky, BUT interesting.