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Discussion Starter #1 (Edited)
I'm looking to replace my 14cm exhaust housing with either a 18cm or a 21cm and a quick spool valve on my 97'. I would actually like to find a way to get the spool valve to open at cruise but can't figure out how. So, I thought that with a big housing even if it stays closed it wouldn't be much different than a GMX or a HX35 at cruise. I welcome others thoughts on this.
 

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Are you using the stock vacuum set up or a mechanical wastegate?
 

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Discussion Starter #3
Housings are non-gated.
 

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Sorry Im not seeing the point of this.

So it reduces the exhaust side input to half. As its half the size the idea that it sends the exhaust in at a faster rate to get the turbo spinning quicker, I have my doubts if this actually translates that way as its still in theory the same kinetic energy.

Either way, so you are saying you would like to have the gate closed at cruise to in theory increase boost?

But you dont need boost at cruise. not at all. If you run 0psi boost at cruise you will still be running lean. You can actually run up to 5000ft (0.85 bar) and still be in the efficiency zone. But at sea level you can easily run 1bar (0psi) and still be at 20 AFR

What is your fuel consumption in mm3 at cruise, the math is pretty easy to calculate required boost at your fuel rate. Maybe you're pulling a 30ft super non-aero dynamic carnival ride at crazy high elevation. I dont know your situation. I just know my K1500 is running very lean at cruise with 1-2psi at cruise.
 

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Seems you would need a outside source that would open the spool valve. Then you would need to undo this when the spool valve is needed. Perhaps a electric solenoid that could force the valve open in cruise mode and deactivate when the throttle is depressed.

Quite sure this would increase economy under cruise conditions.
 

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I think you mean "wouldn't hurt economy" how would adding a valve that has two modes, 50% restriction or no restriction, and leaving it in the no restriction mode. Increase economy? I will give you that it *might* help on low rpm wot to build boost quicker. Maybe. But you Don't want big boost below 1800rpm anyways. You also gain nothing by having boost at cruise, you're actually hurting your economy. The only thing that ever matters is afr air to fuel ratio. Most people agree that 17.5 afr is Max power, some go lower. Low egt is 20-22. Cruise of 110km/h with zero boost (it's actually around 0.5-1psi) I'm running 21.5.
 

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how would adding a valve that has two modes, 50% restriction or no restriction, and leaving it in the no restriction mode. Increase economy? .
By using a low restriction or over sized exhaust housing there is less exhaust restriction. Opening the spool valve will in effect open the exhaust up and the engine will be free wheeling instead of trying to push all the exhaust through one port. Since the vehicle is "cruising" little or no boost is needed.

I relate this to one of those old style water hose nozzles you twist. The tighter you make the water restriction the faster it flows. Draw back is you get less water out of the hose.
 

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As crazy as it may sound a vacuum operated spool valve might be the answer. Using the OEM wastegate solenoid and a little electronic control of sorts you could control the spool valve.( It would be hard to over come the conventional wastegate pod with a solenoid as the spring is quite strong.) The vacuum operated valve could easily be controlled with boost pressure switch and toggle switch on the dash to deactivate the valve while cruising. Guess you seen this here first as I can't find it on the net anywhere. (Thinking out of the box again) For those interested I invented the boost operated exhaust cut out.
 

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I must be missunderstanding, its common, and my fault not yours, trust me, just ask my wife.

I fully agree that a larger exhaust housing will in theory be less restrictive.

What I'm having a hard time understanding is two options

1.) Large exhaust housing, no quick spool valve
2.) Large exhaust housing, quick spool valve in open position

how would option 2 be less restrictive? If you agree that they are both equal, then why have the quick spool at all. In reference to economy at cruise.
 

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the whole point of a QSV is to be able to more quickly spool up a large turbo. The side benefit of being able to open it during cruising is just an extra perk. Most wastegates are just shut until max boost is attained and then it bleeds of the extra exhaust pressure. So by having it wide open during cruise you'll be about as unrestrictive as a turbo can get unless you actually bypassed it
 

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if the quick spool is open, then its basically not there. so it just as non restrictive as if it wasnt there at all. Therfore it does nothing to help with economy. It may help with spooling up quickly as the name states, but nothing to help with economy

btw back to a way back post. I recorded my drive home today. 30mm3 at 1psi = 33 AFR lol, so anyone that thinks boost at cruise is going to help with efficiency isnt doing the math.
 

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Discussion Starter #13
I don't think he's understanding the concept at all.
 

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Discussion Starter #14
As crazy as it may sound a vacuum operated spool valve might be the answer. Using the OEM wastegate solenoid and a little electronic control of sorts you could control the spool valve.( It would be hard to over come the conventional wastegate pod with a solenoid as the spring is quite strong.) The vacuum operated valve could easily be controlled with boost pressure switch and toggle switch on the dash to deactivate the valve while cruising. Guess you seen this here first as I can't find it on the net anywhere. (Thinking out of the box again) For those interested I invented the boost operated exhaust cut out.

You might be on to something here. I believe that this could be controlled with a DB2 throttle position switch so that the valve would open at idle or cruise.
 

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Discussion Starter #15
DieselPro, I'm still banging my head trying to figure this out. If you have anymore input it would be greatly appreciated.
 

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Hey Dixiepc,
Did you figure something out for this? The T4 housing on my S300 is pretty large and I don’t really have any problems with spool, but I also have an automatic, so converter slip allows me to stay over 2000 rpm any time I’m under load – at least in the lower gears. I see you are manual, so the spool valve may make more sense in your case.

As DieselPro indicated, you would likely need an outside source to activate the spool valve at light loads. Does your truck still have the vac pump and solenoid?

I don’t think it would take too much just to actuate the spool valve. A little pump capable of generating 15 psi or so should be more than enough. Then you would need a solenoid. Mcmaster carries some for around $30 to $70 that should work.

Activating it is where I’m still struggling. You could put a microswitch on the pedal linkage. Or tap into the APP wiring with a simple voltage switch. But that wouldn’t work if you are using cruise. With an automatic, we might be able to use the line pressure as an indication of load, but you don’t have that option. Reading duty cycle off of the fuel solenoid would probably work, but I would personally be VERY hesitant to tap into that circuit and I do not know how to design an adjustable switch circuit to work off of duty cycle.
There is always the option of a dash switch. There are lot of guys who want to control everything from the dash – but I hate that option. I would want it to work properly without my input.
 

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Discussion Starter #17
No, I could never figure out how to make it work the way I wanted. I didn't want to use any electronics so I'm going the old school compound turbo way. Still pulling all the parts together for that. I do have a really nice, new quick spool valve that I'd take $300 for though.
 
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