Was doing some research and a friend on Facebook suggested this modification. I want to run a 2.87 pulley with my current Vortech setup for more torque earlier, but not for more power/boost past where I already am at with the 3.12. This mod does just that, bleeds off the extra pressurized air at a predesignated amount of PSI. Please see the link below.

http://www.928motorsports.com/parts/...mitervalve.php

I also searched the Site and found no post pertaining to this at all. Is anyone using this with their Vortech/Prochargered Z? Seems like a great mod! Any input would be much appreciated. Thank you.

 

I've seen this before somewhere...

 

i think there was one for sale on here a couple years ago. It passed between like 6 people and no one ever used it cuz it was a waste of time. Its basic math to determine boost levels with various pulley combos because its directly tied to impeller rpm. I modeled every pulley and cog combo when I had my vortech and the gains under 4-5000 are very small. you are talking about 1 or 2psi difference by going to a 2.87 at low rpms.

You can do it as well. Log you current setup. determine what impeller speed is needed to make what boost (ie 50,000rpms make 4psi, 55000 make 6 psi etc). That will always be constant because you are not changing your supercharger.

Once you have that curve, you can change your pulley sizes to see how that changes your impeller speed. impeller speed = boost levels.

Super simple to model and figure if gaining 2 psi is worth hundred of dollars in parts and fab.

 

You could do what everyone in the ls world does and run a restrictor plate in front of the vortech inlet. Same priciple and works really well.

 

This would be useful if you're too lazy to downshift to get above 3500rpms and want to pull on that SRT-4

 

Thanks for the responses, guys. Thats what is great about the forums, opinions from different prospectives. Looks like the cons outweigh the pros on this one. Im just gonna pick up the 2.87 pulley and quit being a wuss. I will just ask upon retuning to remove more timing up top.

 

I used the 928 blv when I upgraded my blower to an SI and 2.87. At around 5500 rpms before the valve I was almost 440hp and 403trq. The torque already peaked but the hp was climbing high. Decided to throw one of these on and capped the power at 11psi, 436/403. Worked great for my setup.. About a month later or so, I started my built block and sold it..

 

Thats great, man. Nice numbers with the previous setup, Thats actually around where I wanted to have my PSI capped at also in combination with the 2.87.

 

You can use the BOV for the same function.

Tee a ball and spring MBC into the BOV's vac line. It will not affect operation in vacuum, as it acts like a check valve in that direction, but it will limit pressure in the top port of the BOV. The result is that there will be a force differential between the top of the diaphragm and the bottom of the valve face that will open the valve above a given pressure. I've been running a setup like this since I put the S/C on.

I'm not sure why you guys think you need a separate valve for this.

 

Hey man. I need some clarification on your theory that only S/C rpms determine psi. That will be the case when you are only logging psi vs. S/C rpms at redline. But will that be the case throughout the entire rev range, since the engine will be moving less volume, and you will be getting the S/C into its efficiency range earlier? I noticed a significant increase in TQ from around 3000 rpms to redline every time I increased S/C rpms or changed impellers. That was worth the swap to me because I enjoy driving my car hard, but I did not want to shift at redline any time I want boost (shoulda went with a turbo, I know that now, and I did).

So I researched this same setup to build more-boost earlier, but limit the psi to try and protect the stock motor. 90% of the Vortech searches were taking me to Mustang forums, where you can find mixed reviews that go into great detail. Some were using a restrictor plate or wastegate and MBC as mentioned earlier (I did not know you could use your BOV too). But others said it was snake oil, because peak cylinder pressure occurs at peak TQ in a well tuned engine. So as long as you have zero pre-detonation due to running out of fuel system or cooling efficiency, the most stress your rods are feeling is at peak TQ (somewhere in the middle of your rev range depending on engine design). Therefore, there was no reason to limit boost, just peak TQ. Then concentrate on your tune, cooling, and fuel system. The rods are the wildcard, how strong are they on the stock motor? OldmanZ has set the bar pretty high. Just do whatever he is doing.

I am no engine builder, so please correct me if I'm wrong. This is all Internet research, not hands-on experimenting.

 

Jaxter, str8dum1 is talking about at WOT and is just basic info. The gear ratio, created by the pullies, determines Blower Speed. Intake, Piping, Intercooler, Air Filter and Exhaust System all have an effect on Total WOT Boost.

No need for a Boost Limiter, plus you have a built motor. Crank Up the Boost.

Don't make it so complicated.

 

I ended up going with a Fluidampr to spin the blower faster, I mentioned this in my progression thread. Oldman, thank you again for your help. I will retune to rev to 7k rpm after its installed.

 

Yes. I make things complicated. But I think you misread what I wrote.

I don't have a supercharger to turn up anymore, so I have no dilemma.

I was questioning Str8's theory on 1-2 psi being beneficial or not to midrange power. I enjoyed the added midrange from pulleying-down more than I enjoyed the top-end bump.

And next I listed a theory why limiting boost at redline may not be adding any sort of safety-factor. Just keep increasing S/C RPMs until the torque is as high as one is comfortable.

 

where can i get that calculator ?

 

The calculator is on the Vortech webpage.

Here's the link.

http://www.vortechsuperchargers.com/page.php?id=33511

 

thank you
search owned me

 

If anyone decides to do this, do some searching and find a fleabay Chinese waste gate for like 60 bucks. When you get it, take it apart, and check to make sure it is working properly (no binding, make sure it seats etc). If it doesn't seat right, you can make it seat right with some type of putty and or sanding. But mainly check that the diaphragm works and the main stem moves freely. Then order a proper spring from a legit waste gate that will fit and if needed a new diaphragm. Even if it doesn't seat perfectly this will work. Hook it all up and for less than half of what the 928 piece costs you can have a boost limiter.

 

Why use an additional valve? Just use the BOV to limit boost. It's easy.

 

I'd imagine it has to do with the fact that they run recirculated bypass valves and MAF's. By actually dumping it to atmosphere the maf never see's any extra air.

 

Yea I figured it was more work/complicated doing it this way, upon reading about it I "Thought" it was a great idea for me. Maybe someone else will benefit from this thread's info with their car.