AMS500 and boost limit on the stock spring

[WSLN 6]

I was wondering how high the boost can go using the stock 7psi spring in my wastegate (Turbosmart 50) , controlled by my AMS500.
I have adjusted the second stage from 17 to 23psi, but no change in final output as it sits at around 225kpa.
Should I just install the extra spring, or is there usully more room to go?

 

[Bent6]

Depends on what you are using for reference pressure to the AMS - manifold or CO2/Nitrogen. If you're just using manifold, you probably will only be able to get around 15-18# with a 7# spring assuming your wastegate is large enough for your application - lots of variables come into play such as backpressure, ambient temps, etc. The general rule when using manifold pressure as the reference is to run as large of a spring as you can stand for your minimum booost level in order to get the most control. If you use CO2 or Nitrogen you can go as high as you want regardless of the spring size. FWIW

 

[Louie L.]

Depends on what you are using for reference pressure to the AMS - manifold or CO2/Nitrogen. If you're just using manifold, you probably will only be able to get around 15-18# with a 7# spring assuming your wastegate is large enough for your application - lots of variables come into play such as backpressure, ambient temps, etc. The general rule when using manifold pressure as the reference is to run as large of a spring as you can stand for your minimum booost level in order to get the most control. If you use CO2 or Nitrogen you can go as high as you want regardless of the spring size. FWIW

X2

 

[WSLN 6]

Thanks, good info!
I am just using manifold pressure, so that makes sense. The wastegate is 2", ambient temps were around 67 deg.

 

[Bent6]

As a rule of thumb when using manifold pressure as your reference, take your target max boost and divide it by 2 to get an idea of what spring you need in the gate. IE - If your target is 23#s you will probably need around a 10-12# spring in the gate. As long as you can live with a minimum boost of 10-12#s this will give you the most control using manifold pressure. Just make sure your gate can handle the flow - if it overshoots the target or can't hold the boost steady without creeping, you need a bigger gate.

 

[DukeGN]

I'm getting a TS gate as well, and I'd be interested to know if you stick with the 7lb spring or go bigger (and if so how big). More generally, what kind of spring pressure do guys generally use for manifold setups that will only see the street? Do you use a bigger spring and keep her shut longer b/c you're usually not messing with a launch?

 

[WSLN 6]

That will be my plan.....it comes with 2 springs, a 7 and a 11 I think.

 

[WSLN 6]

I put in the larger 11# spirng, and now can get boost to about 20psi or 235-240kpa with a setting of 27psi on the ams500.
How high can I go on the controller to make a difference?

 

[Bent6]

That sounds about right. The AMS can only apply as much pressure to the gate as it has available from the manifold reference. Think about it like this - you have an 11# spring meaning you can make theoretically make 11-12#s of boost on spring alone before the gate opens. This means there is only going to be 11-12#s of manifold pressure available for the AMS to apply to the top of the gate so you've got your original 11-12#s PLUS the 11-12#s the AMS has available to use giving you around 22-24#s MAX boost - this isn't an exact science as there are many varaibles such as ambient temps, turbo backpressure, gate efficiency, etc that will affect the actual boost levels but you get the idea. You can turn the AMS up as high as it will go but it is still limited by the available amount of reference boost from the manifold. This is why most racers use a light spring and CO2 to give them the most range of control.

If you want more than 20#s, try putting both your 7# and your 11# spring in your gate - I'm not familiar with the springs on a Turbosmart gate but if one will fit inside the other like on the TiAL gates this should give you a MINIMUM of around 20#s of boost and will extend the range of the AMS to higher than you will ever need to go - around 35#s potentially. If you can't use both springs I would suggest getting a 13-15# spring which would give the AMS a range of about 25-28#s off manifold pressure - this is a good compromise for most manifold applications as long as you can live with a minimum of 15#s.

FWIW - I usually run a 12# spring on the street with my AMS controlling off manifold pressure. This gives me a range of about 14#s up to around 24-25#s. When I go to the track I switch it to a 5# spring and CO2 so I can launch off the brake at 5-8#s and go to whatever boost level I want from there. Good luck!

 

[WSLN 6]

Thanks, I will try the inner amd outer spring, should do the trick. So much for launch control.....lol
Maybe I should get into CO2.....

 

[WSLN 6]

Set the AMS to 0's on all settings, slow ramp. Put in both wastegate springs, solid 26psi no knock......
Yeeeehaaa!

 

[oldtimer]

Set the AMS to 0's on all settings, slow ramp. Put in both wastegate springs, solid 26psi no knock......
Yeeeehaaa!

Sean,

it looks like you won't need my ride anymore

George

 

[Boost231]

Great post. I was wondering The same thing but I thought you would still get more control using manifold pressure. I guess I need to order a new spring for my tial v44. O well guess I will have to launch the car harder

 

[WSLN 6]

I guess I will have to order a 15psi one, or get into C02 to get any kind of control back. I was planning on running mid 20's 1st/2nd then scale it back using the third gear switch as a trigger for the second stage on the ams.

 

[3.8vsix]

I guess I will have to order a 15psi one, or get into C02 to get any kind of control back. I was planning on running mid 20's 1st/2nd then scale it back using the third gear switch as a trigger for the second stage on the ams.

I may also have to order a spring for mine also. Did you take your wastegate off to change the spring or did you leave it on the car? I also have a bwr setup like yours. I hate to take all that back loose just to put a spring in. It looks as if you can do it on the car??

 

[WSLN 6]

Easy to do....just take out the 6 or so allen screws that hold the top on the wastegate and the spring will pop out. Putting in the double spring was a 2 person job just to be safe.....

 

[3.8vsix]

good to hear you can do it while on the car!

 

[Boost231]

Make sure you keep pressure on the gate when taking the bolts out. Its under a lot of pressure and will strip the bolt holes very easy or take your head off.