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Old 09-29-2010, 07:08 PM   #1
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Default Twin screw with BOV (no trolls or dumb asses)

Going to try to have a real supercharger post for once and looking for input from the local engineers and smart people.

problem and back ground:

mp62 on my car does not have the response i would like. the lower the rpm the worse. if i'm at idle (1k) and stomp on the peddle i can watch the boost gauge, it goes from ~40kpa to 100kpa and sits there for about a sec and the car sounds like it's about to die then boom boost starts to build. if the car is at a higher rpm it does the same thing but boost kicks in faster but still to slow.

why this happens:

throttle body is on the back of the blower so when it's cracked open it take time for air to get form there to the intake and pressurize the fmic and pipes.



looking for how to get the best results, don't want to disable the bypass valve and just install a bov with the thottle body back on the intake as that would make the blower at 11psi when ever to car is running making a lot of heat and ware on the car, enough to end it's life way sooner then it should.
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Old 09-29-2010, 07:15 PM   #2
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Yah but then the supercharger is compressing air all the time and would probably get hot as ****.
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Old 09-29-2010, 07:19 PM   #3
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Quote:
Originally Posted by jeff_man View Post

looking for how to get the best results, don't want to disable the bypass valve and just install a bov with the thottle body back on the intake as that would make the blower at 11psi when ever to car is running making a lot of heat and wear on the car, enough to end it's life way sooner then it should.
Then why bother? Having a fmic and long piping, there is always going to be some lag for **** to get going. It's a lot of volume to pressurize.
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Old 09-29-2010, 08:14 PM   #4
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Originally Posted by Full_Tilt_Boogie View Post
Yah but then the supercharger is compressing air all the time and would probably get hot as ****.
that's if you remove the bypass and why i don't want to go that rought

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Then why bother? Having a fmic and long piping, there is always going to be some lag for **** to get going. It's a lot of volume to pressurize.
i have a tdr fmic with short pipes, there is a lot less vol then most fmic. and why bother doing anything?

most turbo cars have better thottle response because they are always pushing air towards the intake so there is always so volume of air in the pipes. on y set up there is a lot less because the bypass is keeping the air out of the blower making boost lag and slower throttle response.
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Old 09-29-2010, 08:31 PM   #5
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Why not do the dual throttle body mod that every is going to and add a recric valve. This will restore the throttled volume back to normal.
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Old 09-29-2010, 08:48 PM   #6
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Why not do the dual throttle body mod that every is going to and add a recric valve. This will restore the throttled volume back to normal.
not epicly cool enough and to many extra moving parts for a race car. looking for NA type throttle response and doesn't think the duels will give that.
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Old 09-29-2010, 10:36 PM   #7
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Yah but then the supercharger is compressing air all the time and would probably get hot as ****.
Not only that, but you need large enough bypass to pass all the air the blower is pumping (if you don't do dual throttle bodies), else you'll be blowing hose clamps off all day long...or blowing jb welds in my case.

The bypass works fine on turbo cars since you're just relieving the diminishing volume of compressed air when the throttle plate closes. If you close the throttle plate at 6krpm with an MP62 and a standard bypass valve, it's a recipe for blowing **** apart.
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Old 09-29-2010, 10:45 PM   #8
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Originally Posted by cymx5 View Post
Not only that, but you need large enough bypass to pass all the air the blower is pumping (if you don't do dual throttle bodies), else you'll be blowing hose clamps off all day long...or blowing jb welds in my case.
tial q bov move a **** load of air, more then enough to keep from making to much back press.

my first thought was leave the bypass but run the vac line to the intake side instead of off the blower and adjust or make it so it never 100% closes (or opens, which ever is the one that keeps the psi from building), replace tb to intake side and add a bov.

so now you have a bov letting the air you don't need out, the blower is pushing enough air to keep a good amount of presser in the fmic to charge the pipes and get air in the motor the sec i hit the gas and the bypass mod let the blower not get over worked and wont cut air completely anymore.
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Old 09-29-2010, 11:13 PM   #9
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have you thought about running your TB back in the stock location and put the dummy on the blower? doing this youll need a BOV.

we have a local running a mp45 with stock TB location and the dummy on the blower, that car responds so quick and runs like a scaulded dog!
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Old 09-29-2010, 11:20 PM   #10
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I personally haven't looked at the pump curves or bov relief rates, but I'd imagine you could get that information pretty easy. It shouldn't take much work to size everything up for that setup. The supercharger whine really isn't bad, but relieving all that air to atmosphere gets annoying to the point you just want to mash the throttle all the time.

I don't know what you're running for computer, but this is where the benefits of not metering that air come into play.

WonTon, I believe that's what we're discussing...
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Old 09-29-2010, 11:21 PM   #11
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I wouldn't knock duals (one extra moving part...that I think even a race car driver could mechanically handle) without reading some of the threads. They should give back pretty much the stock throttle response since you have the preblower TB cracked feeding the intake tubing (IC, piping) so that the stock TB has air to munch when it opens. When I dynoed my base hotside SC car (no IC, so minimal throttle volume) there was a car with the setup and IC. The dyno operator noted better response with the duals and IC over my stock hotside. So take is as you want (I don't know the scale for your epic cool meter).
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Old 09-29-2010, 11:57 PM   #12
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Add meth injection then load up on timing
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Old 09-30-2010, 12:28 AM   #13
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Quote:
Originally Posted by WonTon View Post
have you thought about running your TB back in the stock location and put the dummy on the blower? doing this youll need a BOV.
that kinda the whole post of my post

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Quote:
Originally Posted by Staffah View Post
I wouldn't knock duals (one extra moving part...that I think even a race car driver could mechanically handle) without reading some of the threads.
i'm not very good at reading and all i have to say is a twin screw with no tb on the back sounds bad ***

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Add meth injection then load up on timing
car will still have 1 sec of boost lag when it goes from vac to 0psi, sits there then jumps to 5 psi.
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Old 09-30-2010, 12:34 AM   #14
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i missed in the post above mine bout the TB! mahbad, and i aint no ****** troll!
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Old 09-30-2010, 01:07 AM   #15
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Try the duals, you'll like it.

Go 3" on the MP62 inlet.
How much boost are you running? (Me=only 6psi)
I have no BOV and no restrictor in the bypass allowing it fast response and the overpressure blows back through the bypass past the cracked open throttle.

Throttle response is back to stock - I had to relearn shifting on the car after getting lazy with the (slight) boost lag.
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Old 09-30-2010, 01:41 AM   #16
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Originally Posted by BarbyCar View Post
Try the duals, you'll like it.

Go 3" on the MP62 inlet.
How much boost are you running? (Me=only 6psi)
I have no BOV and no restrictor in the bypass allowing it fast response and the overpressure blows back through the bypass past the cracked open throttle.

Throttle response is back to stock - I had to relearn shifting on the car after getting lazy with the (slight) boost lag.
11 psi, planning on getting a 3" dummy body for the blower
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Old 09-30-2010, 11:42 AM   #17
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Quote:
Originally Posted by jeff_man View Post
11 psi, planning on getting a 3" dummy body for the blower
It'll be loud, loud loud.

I really think you should give duals a try but obviously, your call.
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Old 09-30-2010, 11:50 AM   #18
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I run duals. Throttle response is OEM.
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Old 09-30-2010, 11:53 AM   #19
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Quote:
Originally Posted by jeff_man View Post
most turbo cars have better thottle response because they are always pushing air towards the intake so there is always so volume of air in the pipes. on y set up there is a lot less because the bypass is keeping the air out of the blower making boost lag and slower throttle response.
I think it has more to do with compressor efficiency and general dynamics of how a turbonatronicator turbonates...a turbo can fill a chamber faster than a twin screw hand dryer. When your checking account feels better, I'll take you for a lap or two.

I have a Bosch BOV you can have...and I think the single t-body w/a TiAL Q is the most simple to build and maintain. It is the way. Your car is loud enough that you won't notice it...unless it produces the "Brown Note."
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Old 09-30-2010, 12:28 PM   #20
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Ask Doppelbanger what he did with his old setup. IIRC it worked good
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