Limiting boost without changing pulleys
 

I want to find a way to limit boost without changing pulleys.

Being that I am waiting on parts to finish my WI, I have been tuning the car without any sort of cooling whatsoever. If I stay out of the throttle, I can get the car to drive descent. As soon as I run it up to full boost (13.1psi), I get to the point where I can cook eggs on my intake manifold (245*F)

Now if I could limit the boost to 7-8 psi, I could come up with a safe tune without WI. I would like to have a map like this just in case something happens to the WI at the track. I hate to loose a whole weekend because a WI part failure.

Way to make this happen....

I need to either provide a way for the boost to vent or limit the amount of incoming air to prevent being able to make the boost.

I am thinking the easiest solution is going to be welding an adjustable blow off valve to the manifold. Or will it be easy enough to just install a pressure regulator into one of the 1/8 NPT ports already on the manifold.

Do you think this will work? Has anybody else done this already? I'm not a fan of reinventing the wheel.

Wastegate that bitch

What charger setup are you using.

Coldside MP62. FFS kit (kinda)

LOL Just reading a thread on this on TideWaterRacing.com Check it out. Good info and links.

Post is about 1/2 way down page 2.

http://www.tidewaterracing.com/forum...212#post333212

PS: I done this before made more heat than its worth, but read up on it.

pressure switch to an orifice. BAM! done.

Corky put something like that on the new MOAB (ex Ubercharger) - to always spin it quick and uses a valve to relieve the extra boost (kindof like a wastegate on a turbo but working in the intake manifold).
I guess any standalone with EBC would be able to have the tables set to control it


http://www.bellengineering.net/Images/P1232878.JPG

http://www.bellengineering.net/Images/P1222824.JPG

The intake will get pretty damn hot as the supercharger is still doing the work to generate that much boost. I'm only running 5psi and I hit those temps you mentioned.

Looks like we both need to intercool or use WI ASAP! :)

Cheers

I have thought about this also. I have an uber, so my plan was to put a wastegate in the charge pipe pre intercooler. No sense in cooling air we aren't going to use. Any of you turbo guys have an old, wouldn't have to be big, wastegate?
How does the wastegate work differently than a blow off valve? Sorry for the noob questions but I am a supercharger guy.

How do you control when the wastegate opens?

I found this yesterday....http://www.musclemustangfastfords.co...all/index.html

It's worth reading. They do exactly what I want to do.

Although, I think Mike's comment about heat is very valid. I know he tried a similar application on a Mustang built for going fast in a straight line. My application is a little different. I am wondering if the additional heat is going to make the reduction in boost a null point. The blower will be heating the air that same way reguardless of whether I am bleeding off the air or letting it flow through. A little hot air or a lot of hot air?

I think my setup lends itself better to this solution. The Uber adds less heat under load than the MP62, I have an intercooler, and will vent the hot air prior to the intercooler so I only have to cool what I am using.

My thought is to get the benefit of the flow lower in the rpm range but not exceed the pressure goals on the top end.

I am still curious about the differences between the BOV and the wastegate for this application. Is it just that the BOV won't cycle quickly enough to maintain a steady pressure? Is there more control on the wastegate?

Not quite. The Eaton doesn't compress the air internally, it just moves it, the compression mostly happens in the intake manifold. And that compression in the intake manifold is what creates a lot of heat. If you bleed off air and lower the pressure, the temperatures would be lower. Check the temperature increase from the MP62 at 5 psi boost vs 10 psi boost - at the same supercharger rpm there is a big difference in how much heat is generated and how much power is needed to turn the blower:

http://www.magnusonproducts.com/images/mp62g2.jpg

I can't imagine a controlled boost leak being good for the blower going to be asking it to do a lot of extra work for nothing.

I don't know that much about blowers, but don't they have a bypass valve already built into them? So you aren't building boost at idle? couldn't this be controlled via a boost referenced valve?

A clutch on the pully would do the trick, starts slipping at a preset RPM.

Also keep in mind there is a difference between a vacuum actuated butterfly valve and a solenoid valve. The butterfly valve can limit the cross-sectional area at any pressure reference, the solenoid will be on/off (bang bang system) unless you use something like an EBC that isn't simply on/off.

If you set your SC clutch to disengage at say, 8 psi. What happens when you're cruising between 7+ psi? The clutch will keep engaging/disengaging as the pressure fluctuates around the threshold...not recommended.

I understand you're running MS. Is the tuning MAP or AFM based? if you bleed air after it's been metered, wouldnt it be a nightmare to tune? just thinking out loud.

MAP, so it shouldn't be an issue.

People still have AFMs?

AFMs, heck I have two of them, one stock , one Rx-7, both in a box to sell eventually.

MAP for the win.

How about restricting the airt before the SC, shit even before the TB. Try a restrictor plate that will flow up to your desired limit.

Just brain storming....

That's why the throttle body is before the supercharger for roots blowers.

But a plate like a air filter that just does not flow well. You would still need TB to modulate the throttle.