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ATI Supercharger - Surge Valve


SVTCobraGuy

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Are there better alternatives to the Pro-Flo surge valve setup that comes with the ATI Procharger kits?

 

Does this setup cause any delay in building up boost?

 

Seems like it is taking longer than it should to build up boost. It doesn't get crazy until around 4000-4500rpm.

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Well...crap. I bet the 4.6 DOHCs are worse than a SOHC too. So, you have the same surge valve setup on your Stang too (dumps the boost when the manifold goes to a vacuum)? What would happen if I got rid of the surge valve and just put a popoff valve to limit to max boost? Kaboom?

 

Originally posted by BDHG940:

Get used to it :), same thing with my car. Under I would say 3000rpm, it really doesnt feel anything special. Just have to keep the motor up in the rpm's a little more now.

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Originally posted by SVTCobraGuy:

Well...crap. I bet the 4.6 DOHCs are worse than a SOHC too. So, you have the same surge valve setup on your Stang too (dumps the boost when the manifold goes to a vacuum)? What would happen if I got rid of the surge valve and just put a popoff valve to limit to max boost? Kaboom?

 

The purpose of a bypass valve (or "surge" valve) is to eliminate pressure between the blower and throttle body at idle and part throttle (vacuum) conditions. Eliminating it would cause driveability and idle issues (backwash through the MAF).
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If you get on corral.net, there is a company that advertises on the top of the page. If you wait a second, there will be a new billet aluminum by-pass valve that they sell. Pretty badass, I was thinking of getting it.
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Thanks, I think I am slowly grasping this concept.

What ensures the bypass valve closes efficiently as boost builds? Doesn't the engine have to reach a high load/vol. eff. before the valve even begins to close? Trying to get SOME lag out of the car building boost. Any tricks? Am I turning this into rocket science smile.gif ?

 

Originally posted by rl:

The purpose of a bypass valve (or "surge" valve) is to eliminate pressure between the blower and throttle body at idle and part throttle (vacuum) conditions. Eliminating it would cause driveability and idle issues (backwash through the MAF).

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Change your gearing smile.gif

 

Pumped volume of the charger increases with square of compressor shaft speed. So if you look at graph of engine RPM vs boost, it will be an upward sloping curve. You could be making 2psi at half redline, and full boost of say, 5, at redline.

 

The surge valve opens late, and should be open at Idle. As soon as you exceed atmospheric pressure (what a N/A car would be limited to) and create positive, pressure the valve shuts. Basically you have to wait for you charger to spin up to a speed where it creates boost.

 

You could try a smaller pulley, BUT you will spin the blower faster, creating more heat, and may throw more heat into your intake charge than desired, killing your higher end efficency. If your setup cannot handle the incresed boost (fuel, motor), than your kinda stuck

 

Are you aftercooled?

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Yep, she's got a 2-core intercooler after the supercharger. I understand what you're saying about boost curve of a centrifugal supercharger. Cool, makes sense. Thanks.

 

I'm just trying to eliminate the bypass valve as a source of lag. That would be cool to spin the supercharger faster and maybe put a relief valve to limit boost.

 

Did change the rear end from a 3.27 to 3.73.

 

Originally posted by Helicoiled:

Change your gearing smile.gif

 

Pumped volume of the charger increases with square of compressor shaft speed. So if you look at graph of engine RPM vs boost, it will be an upward sloping curve. You could be making 2psi at half redline, and full boost of say, 5, at redline.

 

The surge valve opens late, and should be open at Idle. As soon as you exceed atmospheric pressure (what a N/A car would be limited to) and create positive, pressure the valve shuts. Basically you have to wait for you charger to spin up to a speed where it creates boost.

 

You could try a smaller pulley, BUT you will spin the blower faster, creating more heat, and may throw more heat into your intake charge than desired, killing your higher end efficency.

 

Are you aftercooled?

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Kewl, I'll check it out. Thanks for your help!

 

Originally posted by BDHG940:

Someone over on Corral has been working on a boost controller for centrifugal superchargers. Haven't really checked up on the thread lately, but you might try over there.

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Keep in mind some things when you spin the blower faster. Turbos and superchargers have efficiency ratings to them. They will create "boost" but the power adder may become more inefficient. This means that the more volume it would produce would be negated because the compressed discharged air is marginally hotter. So what you would gain at low rpm (say 3500-3800) would have an inverse effect on your high end (6000-7000 {I can’t remember how much your motor revs too}). You would bypass the air, but the air would still be hotter, killing some of your top end power.

 

hotter air = -power

colder air = +power

 

I would talk to ATI or an aftermarket company to see if you can get a smaller pulley and not change things around to much. My guess is that it come with the smallest pulley that keeps things safe. Rob could probably comment on this.

 

HTH.

 

Originally posted by SVTCobraGuy:

Yep, she's got a 2-core intercooler after the supercharger. I understand what you're saying about boost curve of a centrifugal supercharger. Cool, makes sense. Thanks.

 

I'm just trying to eliminate the bypass valve as a source of lag. That would be cool to spin the supercharger faster and maybe put a relief valve to limit boost.

 

Did change the rear end from a 3.27 to 3.73.

 

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Limiting boost by bypassing it to the atmosphere is a horrible, horrible idea. You end up with a hotter air charge, and more work to spin the blower harder all for the same boost, you would lose a LOT of power.

 

How much boost are you running? The true safe-ish limit for a stock 4 valve car is in the 12psi rangen if tuned correctly.

 

The bypass is held shut with a spring, vacuum overcomes this spring to open it. at 0" of vacuum the valve is closed 100%, as boost builds it equalizes on both sides of the valve and the spring keeps the valve shut.

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Originally posted by rl:

Limiting boost by bypassing it to the atmosphere is a horrible, horrible idea. You end up with a hotter air charge, and more work to spin the blower harder all for the same boost, you would lose a LOT of power.

Question for you:

 

A little of the topic, but what is bad about venting to the atmosphere? If the system is designed to do so and the MAF is after the by-pass valve?

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Originally posted by BDHG940:

Question for you:

 

A little of the topic, but what is bad about venting to the atmosphere? If the system is designed to do so and the MAF is after the by-pass valve?

A wastegate on the compressor side of a supercharger system is what I am referring to. Its a bad idea. The more pressure the blower creates the hotter the air charge, and in many cases to further out of the efficiency range of the compressor you get. Spinning the compressor faster requires a great deal more power to be used from the crankshaft. Now think about what is going on. Say you have a system running at 8psi, you add a 8psi wastegate to the compressor side, and a pulley for 16psi. Yeah, you'll get into boost very fast (the compressor is spinning faster) but after the wastegate opens and you begin to vent pressure (it would take a BIG wastegate mind you) you're now running a hotter air charge (less timing) and spinning the compressor faster so its using MORE power from the engine. But your still seeing that same 8psi. In this case you would make SIGNIFIGANTLY less power than if the car was simply pullied for 8psi, the ONLY benefit being the increase in pressure at lower RPM's.
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I have a ATI D-1SC if you go to vortech's website something that is really reccommended is the racing bypass...it is a very good thing to get because procharger is very bad at blowing seals because of all the pressure buildup in the self contained setups... they are around $221.00 buxks but it is VERY well worth it.
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RL, I understand what you're saying. Basically, the low end benefits of overdriving the supercharger are not worth the heat and boost relief problems at high end. I've noticed some people adamant about this pursuit have custom controllers and special "iris"-type valves on the blower intake side.

 

Thanks for the explanation. I will probably not attempt any endeavors in this area.

 

What is your suggestion on the bypass valve setup? Is bypassing to atmosphere a good idea to combat backwash from the ATI setup? Was thinking about a Lightning 90mm MAF as well. Would a larger MAF eliminate some backwash? Any comments are greatly appreciated.

 

Originally posted by rl:

A wastegate on the compressor side of a supercharger system.......

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Cool, I will check out. How is your ATI bypass system setup? Does it dump the boost to atmosphere or back to the inlet side of the charger?

 

Originally posted by little devil98gt:

I have a ATI D-1SC if you go to vortech's website something that is really reccommended is the racing bypass...it is a very good thing to get because procharger is very bad at blowing seals because of all the pressure buildup in the self contained setups... they are around $221.00 buxks but it is VERY well worth it.

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Get an SCT MAF when they become avaiable again. Its a Lightning maf with MUCH more range, you'll damn near peg a Lightning Maf (I just about am). If you convert to draw through (DONT use anything other than a Pro-M procharger or univer MAF in blowthrough) recirculate the bypass valve at least a foot behind the maf, or as far away as possible. Try to keep some straight pipe after the MAF as well. Dont vent to the atmosphere unless you are running a blow through and the bypass is before the meter.
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dumps to the atmosphere... they have racing bypass ones and then they have the mondo race bypass ones. i will be getting two of the mondo ones...just cause of all the heat and pressure..not blowing these seals again...(HOPEFULLY)

if you need any help or anything just im me..be glad to help out. hope it all works out for you!

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