AMS1000 operation for dummies

[Alky V6]

I thought I'd start a 'thinking out loud' thread to share ideas on boost controller operation, initial setup strategies, experiences, tips, and various racing boost rise strategies.

I've just installed an AMS1000 boost controller. This is a very popular unit at this time, but it's got me a little confused.

What I need is a layman's description of how to use this controller without, and especially with CO2.

First, without an external pressure source. The unit using manifold pressure as the control pressure. My question is, do you build the boost ramp rates and psi target numbers to match exactly what you wish to occur with the intake manifold pressure? I realize there are other factors such as whether the turbo can boost pressure as quickly as you might wish and the spring pressure being used in the wastegate, but do I have the programming part of it right?

 

[GNBRETT]

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[Alky V6]

OK. Looks like everyone is in the same life boat as me, and wanting to be rescued first. We'll just have to think this one out ourselves then. Nothing new to me. Let's get started.

Let's start with the simple scenarios, and we'll work up to the monster setups later.

An average street/strip GN/T-type with a relatively quick spooling turbo, but wanting to limit boost for street gas circumstances. We'll pick 18 pounds boost. No auxiliary wastegate control pressure is being used (no CO2), just manifold pressure. We are using an external wastegate with port connections above and below the wastegate diaphragm. Right now, we'll keep the port connections open to atmosphere. In this situation, the spring weight, that is in the wastegate pushing on the diaphragm to keep the wastegate valve closed, is the only thing controlling boost rise and level, so the tension of this spring is very important. We end up playing with spring tensions and the limited adjustment of our spring choice, afforded by the screw and locknut on top of the wastegate to arrive at our preferred boost level. What can we expect the boost rise rate to be like? What is boost creep and why does it occur? What sort of variables in our simple system affect these circumstances? Come on guys. A little help here.

 

[Alky V6]

What can we expect the boost rise rate to be like?
What is boost creep and why does it occur?
What sort of variables in our simple system affect these circumstances?

Boost rise would not be as quick as possible with a relatively quick spooling turbo. We do have the wastegate spring set relatively heavy because we are not using any assist from manifold pressure above the w/g diaphragm to help the spring keep the wastegate valve closed. But, with exhaust back pressure building and working on the w/g valve and against our chosen spring pressure, we can expect the wastegate valve to crack open and relieve some of the exhaust back pressure that is needed by the turbine housing to spool the turbo. This occurs before our boost limit of 18 psi has been reached, slowing the rate of boost climb up to our limit boost number.
We could clamp the wastegate down harder by cranking in on the adjuster or changing to a heavier spring. That would cause the wastegate to 'crack' at a later time, and would quicken the boost rise rate to our target 18 psi. The problem being now that the boost would ultimately be limited to a higher boost level than our target, due to the higher spring pressure we have in the w/g.

Boost creep is caused by the wastegate not having the necessary flow capacity to relieve the required amount of exhaust energy to slow the turbine wheel enough to maintain a target wheel speed and hence boost level. It may well be that the wastegate could have the flow capacity necessary, but the plumbing before and/or after the w/g could be restrictive. With the stock w/g setup, you commonly hear of people increasing the size of the hole in the turbine housing feeding the internal w/g. The reason is, that hole is not allowing enough flow through it to relieve exhaust energy flowing to the turbine wheel and the turbine wheel overspeeds for your paricular boost target and you get boost rise above the target level. That's boost creep.

I know. Boring stuff for most of you. I just feel I have to get this basic stuff out of the way. I'm sure newbies will appreciate the effort.

 

[TURBO 6]

Boost will rise until the exhaust pressure is higer than spring pressure. You already knew that. The "ramp" will be a boost spike then an immediate drop in boost.
Boost creep will become prevalent (sp?) when the WG becomes a restriction and cannot flow enough to keep boost at the desired level. You knew that also.

 

[Alky V6]

Boost will rise until the exhaust pressure is higer than spring pressure. You already knew that. The "ramp" will be a boost spike then an immediate drop in boost.
Boost creep will become prevalent (sp?) when the WG becomes a restriction and cannot flow enough to keep boost at the desired level. You knew that also.

Yes I did. I just want to get some basics out of the way. Thank you for contributing. Feel free to add anytime.

Now let's add manifold pressure control to our wastegate. What options open to us? A little more control? How does manifold pressure above or below the w/g diaphragm affect our control of the target boost level and the rise rate to it?

 

[Quick6'n'-K.C.]

That thing is insane!

AMS1000.com Home: Content / content / AMS-1000 Spec

 

[Alky V6]

Boost will rise until the exhaust pressure is higer than spring pressure. You already knew that. The "ramp" will be a boost spike then an immediate drop in boost.
Boost creep will become prevalent (sp?) when the WG becomes a restriction and cannot flow enough to keep boost at the desired level. You knew that also.

Here's one of those variables that could change the boost rise rate with the wastegate acting as a simple pop off valve. Which it is when the ports above and below the w/g diaphragm are simply opened to atmosphere.

Exhaust back pressure.
Not every engine/turbo combination creates the same ratio of exhaust back pressure to manifold boost pressure. A turbo engine that has a high exhaust to boost pressure ratio would have the w/g crack open much sooner before the target boost level than one that has a low exhaust to boost pressure ratio. If I'm not mistaking, typical GN exhaust back pressures with typical combinations run around 2 or more:1. I've been taught here that a ratio of 1.5:1 is a good ratio when your looking for low power losses due to exhaust back pressure. And, 1:1 or better is the holy grail.

 

[HighPSI]

Threads like this show why it's important where you buy your boost controller from. You're off to a good start :smile:

 

[Alky V6]

A wastegate, when setup as a simple pop off or poppet valve, will tend to have a pressure spike as the valve is opening to control boost. Why is this?

The speed that a particular turbo is building boost can be too quick for a heavily weighted or undersized, borderline sized w/g to react to. The turbine wheel has some inertia that has built up during the spool up and now we want to all of a sudden slow it down, or stabilize the speed of it right at our target boost. Not going to happen with a 'dumb' poppet valve. There is no mechanical brake to the turbine wheel. It's kind of like steering a slow moving boat. If you want it to turn, you'd better start initiating the turn sooner than you need it to happen.
The w/g must be able to anticipate the quick boost rise and start controlling turbine wheel speed sooner with a quick spooling turbo to avoid overshooting the target turbine wheel speed and hence boost level.

 

[Alky V6]

Threads like this show why it's important where you buy your boost controller from. You're off to a good start :smile:

Thanks Cal.

I've always wondered why it's so hard to find good tuning information for boost controllers. Too many tuners keep it to themselves. I'm hoping to break the trend here.

I realize I may be giving out racing secrets here, but I'm just not the kind of guy that likes to keep secrets. I like to see the information get out, people put it to good use, and watch the competition at the track that comes from it.

I hope if you catch something that doesn't sound right, you'll straighten me, or anyone else, out on the subject. Thanks in advance.

I like to figure things out for myself too much. Too a fault, I'm sure. I just enjoy the learning process too much to give it up. For those that just want it to work correct, right now, without having to fuss with it, you want to search someone out that has a lot of experience with the device. Cal is that person.

 

[Alky V6]

A wastegate, when setup as a simple pop off or poppet valve, will tend to have a pressure spike as the valve is opening to control boost. Why is this?

The speed that a particular turbo is building boost can be too quick for a heavily weighted or undersized, borderline sized w/g to react to. The turbine wheel has some inertia that has built up during the spool up and now we want to all of a sudden slow it down, or stabilize the speed of it right at our target boost. Not going to happen with a 'dumb' poppet valve. There is no mechanical brake to the turbine wheel. It's kind of like steering a slow moving boat. If you want it to turn, you'd better start initiating the turn sooner than you need it to happen.
The w/g must be able to anticipate the quick boost rise and start controlling turbine wheel speed sooner with a quick spooling turbo to avoid overshooting the target turbine wheel speed and hence boost level.

For the wastegate to control turbine speed quick enough to prevent a spike above the target boost level, it must open before that point, in anticipation of the target boost level, and must open larger than a heavily weighted spring will allow. You're trying to quickly adjust the momentum of things that are occurring, which requires a little over reaction on the part of the wastegate valve. A dumb poppet valve cannot accomplish this task.

 

[Alky V6]

I think I've worn that point out enough. Let's move to adding manifold control pressure to the picture.
Taking a break. Be back later.

 

[norbs]

Sorry to interfere, but this is an important point to bring up, before the average buick owner wants to use this as a normal boost controller. The ams-1000 can;t be used for continuous boost control without the use of an activation input +12volt. If you keep the activation active the solenoids will pulse continously wearing them out, with contstant clicking. The only solution was to use a hobbs pressure switch set just slightly below the spring pressure to activate the ams-1000. If anyone has a better solution for this, please let everyone know. Now Don you can continue......

 

[TURBO 6]

Norbs, you could use the tps aux out on XFI to activate the ams. (thanks Otto)



Don, sorry about that. I didn't know you were posting a tutorial. FWIW I'm helping a friend tune an AMS1k on his DR mustang and am highly impressed so far.
The process unit I run at work is like having a thousand of these controllers, so this stuff is like second nature to me. Dusty knows what I'm talking about.

 

[Robert Wilson]

For the wastegate to control turbine speed quick enough to prevent a spike above the target boost level, it must open before that point, in anticipation of the target boost level, and must open larger than a heavily weighted spring will allow. You're trying to quickly adjust the momentum of things that are occurring, which requires a little over reaction on the part of the wastegate valve. A dumb poppet valve cannot accomplish this task.

I am using the 500 with C02 instead of the 1000 but this would apply to both.
My experience in controlling boost spikes has been this:
If I use no ramp rate from the controller (fastest spool possible), I get about a 2.5 psi spike above target level when going from stage 1 to stage 2. I am sure this would be different for each engine/ turbo combination.
Attached is a screen shot from an old post showing one of my XFI boost logs. You can see the boost spike before settling in on the target level.

After reading some responses in the AMS tech forum, it is suggested by AMS to match the ramp rate setting of you controller to your spool up rate of your turbo to avoid this. I tried this and it works perfectly.

For cars using ramp rates even slower than the spool rate of the turbo, such as big power cars with traction problems, I would not expect boost spikes to be a problem provided wastegate is properly sized.

 

[norbs]

Norbs, you could use the tps aux out on XFI to activate the ams.

Thats a good way to do it for the XFI users, but for the others, the hobb swtich will have to do. Smart thinking.

 

[Alky V6]

You guys are welcome to add to this thread anytime you want.

 

[Alky V6]

I am using the 500 with C02 instead of the 1000 but this would apply to both.
My experience in controlling boost spikes has been this:
If I use no ramp rate from the controller (fastest spool possible), I get about a 2.5 psi spike above target level when going from stage 1 to stage 2. I am sure this would be different for each engine/ turbo combination.
Attached is a screen shot from an old post showing one of my XFI boost logs. You can see the boost spike before settling in on the target level.

After reading some responses in the AMS tech forum, it is suggested by AMS to match the ramp rate setting of you controller to your spool up rate of your turbo to avoid this. I tried this and it works perfectly.

For cars using ramp rates even slower than the spool rate of the turbo, such as big power cars with traction problems, I would not expect boost spikes to be a problem provided wastegate is properly sized.

Very interesting. What turbo, wastegate and spring weight are you using? What pressure is your CO2 regulated to?

 

[Alky V6]

Let's put manifold pressure to the port below the w/g diaphragm. Any pressure here will work in addition with exhaust back pressure against the w/g spring to open the w/g valve. So, if left without any device in this line and manifold boost pressure allowed to freely act against the w/g spring, this will result in a lower boost level than if the port was open to atmosphere. It would be the same as making the w/g spring lighter.

If we wanted to maintain our target boost of 18 psi with this line connected to the bottom port, we would need to make the w/g spring heavier to counter the exhaust back pressure plus the manifold boost pressure acting on the valve and diaphragm.

What really makes this configuration interesting is that now we can control the manifold pressure in this line to start applying some control to the wastegate. If we installed a small pressure regulator in the line and adjusted it to provide a relatively low pressure to the wastegate under boost conditions, the target boost level can be raised since there will be less pressure on the diaphragm working with exhaust back pressure to open the w/g valve. If we allow the same regulator to provide as much pressure as the manifold can deliver to the w/g, then the boost target can be lowered. So now we have a limited range of boost target control that can be accomplished at the driver's seat on the fly.

What if we have a setup where the w/g is cracking too early and causing a slow boost ramp up. We can install a spring loaded check valve in the same line that will only allow pressure to pass to the w/g after a certain pressure has been reached that will open the check valve. This can allow a quicker boost rise to the target, but can easily result in a pressure spike past the target level.

We can also have a computer control a pulse width modulated valve to control the level of pressure sent to the w/g to provide a small range of boost control. This sounds familiar.