Boost Limiter Valve

[Lextreme II]

Here is something you guys been waiting for. This acts as an wastegate for supercharger. This little thing can make centrifugal boost comes along sooner. Instead mas psi at redline, you can select max psi at 3000 rpm or whatever. Perhaps this is a good equalizer to compete with turbo boost.

Boost Limiter Valve

 

[-Nemesis-]

Yeah we were looking at those before, kc95... bought one of the earlier versions though I don't know if he used it.

 

[Lextreme II]

This little toy does sound interesting and if it work properly this should give you massive full boost at very low rpm. Once example would be the Procharger P1SC with the Fish. At 3.4" charger pulley will yield around 6-7 psi. Lets assume a 2.5" pulley yield 16 psi (1 psi per .1") and the BTL is set at 6 psi. You would reach your desire boost (6 psi) at half of the rpm. In this car assume 6,200 is redline and 6 psi would achieve at 3,100 rpm. This boost curve is almost like turbo.

 

[Vander]

Is this just for a centrifugal supercharger? Or does it also work with m90, and m112?

 

[spf_lexus]

I remember trying to start a thread on this and got beat down by haters LOL. I love the idea but the limiter must be reliable.. if it fails so does the engine. Engine setup for 7psi boosting 16 "by accident" would spell certain death. Wastegating and elec.. controllers get expensive... only downside i ran into.

 

[Lextreme II]

Is this just for a centrifugal supercharger? Or does it also work with m90, and m112?

Yes this will work on all FI including turbo. However, you dont really need this for turbo application because you have the good old wastegate but it is the same principle. Turbo using wastegate and mechanically it didnt open it would produce very similar distructive results.

Root or twin screw would work as long as you can make an outlet for bleeding.

 

[cribbj]

SPF I don't know that anyone was "hating" on you about this, but you have to realise there's no "magic bullet" to do what you want with no downside. With any belt driven supercharger, if you adjust the drive ratio to get lots of boost down low, then use a device like this to blow off the excess boost up top, there are a couple of things you have to realise:

1) Most PD superchargers have an upper RPM limit of 13,000 to 14,000 RPM. If you setup your drive system so you have an engine/SC drive ratio of greater than 2:1 to get all that lovely boost down low, and you decide to go past 7K RPM with your engine, then you run the risk of wrecking your SC by overspeeding it.

2) The next mistake would be getting a bigger SC than you need and just spinning it slower, and bleeding the excess boost off up top. By doing this, you're consuming more power (with the bigger SC) to make the same amount of boost that a smaller SC would consume, so you may net less to the rear wheels anyway.

The fundamental problem I see with this Boost Limiter valve is that it wastes energy the SC has already taken from your crankshaft, because it's bleeding it off to the atmosphere.

A better design IMO, would be an adjustable bypass valve that would partially unload the SC above a certain boost pressure. These types of valves are often called "unloader" valves for air compressors or "recycle" valves for big gas compressors, because they can regulate the output of pumps and compressors without wasting as much energy as a bleeder valve.

I'm going to try to limit/regulate my topend boost by using the standard bypass valve on my SC setup. Once we get the engine internals all sorted out, and it's making the power it should, then we'll start looking at ways to do this, and other things.

 

[-Nemesis-]

A better design IMO, would be an adjustable bypass valve that would partially unload the SC above a certain boost pressure.

Isn't that essentially what this limiter valve does? From what I gather it's like a basic wastegate, so once boost hits the predetermined level the excess is bled to the atmosphere.

I know you can use wastegates as boost limiters on centri blowers, these valves are essentially cheaper more simple versions.

I think i'd rather know my BPV is open at vacuum and closed at boost, then let another device control boost. But there's always the option of restricting air intake to control boost as I brought up in another thread, another interesting option that doesn't mean wasted CFM efficiency.

 

[cribbj]

Nope, the operation of the wastegate is completely different than this.

The wastegate diverts exhaust either into the turbine of the turbocharger, or out the tailpipe.

This boost limiter is more like a pressure relief valve, above a certain level, it's going to relieve the pressure.

I'll knock up a schematic or two and will post later if our pic posting is working again. It'll be much clearer with a schematic.

 

[-Nemesis-]

Yeah I understand what a wastegate is in a turbo application, but there's heaps of talk out there about using them on centrifugal blowers. I 'think' this thread is aimed at the centri ppl?

You use the wastegate post charger and it will bleed excess pressure, can even use boost controllers then. Opens up a new world with centri's...

Here's one link

http://www.musclemustangfastfords.c...gal_supercharger_wastegate_install/index.html

 

[spf_lexus]

Cribbj-Understood on overspinning but it should not overspin... period. This is a daily driver... no way i'm raising my redline either. My reasoning is that this has a max impeller speed of 65,000rpm, with a efficiency ceiling of 14psi before drop off and a total max boost of 20psi. Now I know the SC will spin faster at full boost... once air is being bled off but it still will not come ever near that danger zone, 14psi working range w/ a 20psi operation ceiling? That seems pretty strong. Now I originally thought of using a 18psi pulley but thats too drastic.... now a 12psi pulley like David said would effectively cut down on lag offering 7psi (max boost) as easily as 3K-3.5K.

 

[cribbj]

SPF, your 65K impeller speed isn't the speed the engine is spinning the SC pulley. You also have a gearbox in there that steps up the pulley speed by between 3 and 6 times.

So let's say you have a 2.5:1 drive ratio between your crank dampner and your SC pulley, and you have a 5:1 stepup ratio in your SC, so you're actually spinning your SC impeller at 12.5 times your engine RPM. If you hit 7000 RPM with your engine, your impeller will find itself at 87,500 RPM. Not good........

You need to get on the ATI website and figure out which SC you have and which gear ratio you have in it, and then have a look at the pulleys you're running, and figure out the max engine RPM you can run before your SC starts puking parts.

I don't mean to derail this thread; I just don't want to see you guys wasting boost, when there could be a better way.

 

[spf_lexus]

All i'm trying to state is that my redline is not 7k... so no comparisons needed there. Also these are supposed to be spun fast, if i had NO diverter valve at all I would still be just pushing 12psi... not quite enough to overspin the SC, or bring it out of efficiency. so take that scenario and add a bleeder, all we're doing is dealing with a little parasitic loss thats only coming into play under full boost which outweighs the loss big time IMO.

The thread i posted on earlier w/ the mustang Cobra dyno'ed huge gains by using a very similar setup, with a charger that has a lower rev ceiling supporting lower CFM


lol and outside of ditching our setups altogether and surrendering to the almighty turbo... this IS the only way.

 

[spf_lexus]

Something else I found interesting.... My neighbor's Vortech Honda S2000 is spinning with the same step-up ratio as Kc, (pretty sure) as his is a smaller unit than mine.... spinning a 9,000RPM Honda? With the same(very similar) unit powering 1uz, operating speeds have changed yet performance has not, and his spools much faster than mine and it's not entirely due to not running an intercooler. I need to ask Kc for the exact model but i want to say it's a V-9 or V-7. I have my doubts on the step-up issue issues w/ car's engine speed. Your right tho, if i raised my revs to 7500 then the multiplication could throw the operating speed above maximum.

 

[Lextreme II]

Here are the Procharger Spec: Look for Impeller speed (62,000) and internal step up. For the P1SC the internal step up is 4.1:1

Here is the Vortech Impeller calculator: Punch in the numbers

The Vortech V1: Straight cut spur gearFits engines up to 680 horsepowerMaximum airflow: 1,000 CFM*Maximum boost pressure: 20 PSI *Maximum impeller speed: 53,000 RPMAdiabatic efficiency: 75% **Available with straight or curved discharge. The Vortech V1 internal step ratio is 3.6:1

 

[-Nemesis-]

I would get one to test it out, but it's hard to go ahead when the US$ is half of what it was a few months ago, would cost me almost double.

 

[Lextreme II]

Honestly I wouldn't get the one off ebay. I think it is too small. If it is too small they you will have boost creep. I would get a 50mm or 60mm wastegate where you can also control the boost too manually or electronically. I plan to run 20-25 psi with 15 psi into the engine. So I would get the smallest pulley possible. I think redline at 6,200 for our 1uzfe motor along with Procharge P1SC your max pulley size is 2.05". That will be guideline before over spinning the supercharger. The Procharger P1SC max rpm is 62,000 rpm and Vortech is about 55,000 rpm. With 2.05" supercharger pulley you will be getting very close to 62,000 supercharger rpm during redline (6,200). However, smaller pulley will experience belt slippage.

 

[spf_lexus]

I plan to run 20-25 psi with 15 psi into the engine. So I would get the smallest pulley possible.

What beast will be receiving this treatment Also, is there any way to convert to some type of "cogged" drive belt thats separate from the serpentine? I think a 2.05'' pulley might have some slippage issues? What do you think lex? I want more of a "stepped down" version of yours... possibly 15psi pulley bled off at 7 or 8 psi.



Oh and just wondering, is there any way to upgrade p1sc to use a curved-blade impeller? See all the cool shots of them on the internet but never actually seen this beautiful wheel.

 

[Lextreme II]

Well,

I am working on the 5.2L VVTi SC400 engine at this time. Money been kindda tight so things slow down a little. I am using a 4.7L VVTi 2uzfe iron block and stroking it out to 5.2L with longer rods, offset grinding of the crank along with custom coated forged pistons. The pistons and other parts are done but still waiting for the VVTi engine to arrive. I got a great deal on a 1998 VVTi SC400 engine along with transmission, harness, ecu and security key. This combo will be going into my 1995 SC400. As for fuel management, Mitch P. will be helping me with the AEM setup. I had a big debate on turbo and supercharging in my plan but due to simplicity I will be doing the Procharger P1SC. Why Procharger? Self Contained is first thing that attract me. Secondly, the Procharger has about 8,000 higher impeller speed then Vortech. Thirdly, the Procharger will make more boost at a given pulley size.

From your experience, 3.4" yield around 7 psi or so and seems like every .1" smaller pulley will yield about 1 psi of boost.

 

[spf_lexus]

Well I have to say you are building my dream block I'm guessing to say that VVTi + cams in this case should net even more tq? Your stroker w/ the p1sc is going to drive like a MASSIVE big block(minus weight) lol, You must let me ride shotgun once it's running! It will solidify my plans for 2uz lol.