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Forced Induction Turbo, Supercharger, Methanol, Nitrous


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Old 09-05-2018, 11:37 AM   #603
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Originally Posted by Irace86.2.0 View Post
What would be the cost to gas mileage by removing it? Would there be consequences in any other way? Would there be improvements?
I am not sure. I can see throttle response being a bit more immediate, but that is already a strength of a PD supercharger. That I can tell, all of the OEMs that have used these types of superchargers have included the bypass valve. I've owned a old '90 Thunderbird Supercoupe that had the Eaton M90 (factory). It also has the bypass valve. In fact, Fords literature at the time indicated that the bypass valve was there to reduce/eliminate the parasitic drag of the blower when not under load thereby maintaining competitive fuel economy to the regular motors. Without the bypass valve I can see a huge vacuum being produced on the back side of the throttle plate when snapped closed at high RPMs. I don't know if there would be any negatives to that, maybe MAP sensor out of range?

I know Harrop is experimenting with using the bypass valve as a type of "boost bleed" in conjunction with a flex fuel kit (higher boost on E85, lower on gas), but I'm also sure that they are not defeating the low load "open under vacuum" operation to do so.

You can probably simply pull (and plug) the vacuum line from the actuator to test how the car reacts.
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Old 09-05-2018, 12:03 PM   #604
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The bypass valve is also there to reduce surging of the compressor. Without it the vacuum at the inlet of the compressor would surge when the throttle plate snaps shut. It's the same reason a blowoff valve extends the life of a turbo.
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Old 09-05-2018, 12:38 PM   #605
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The bypass valve is also there to reduce surging of the compressor. Without it the vacuum at the inlet of the compressor would surge when the throttle plate snaps shut. It's the same reason a blowoff valve extends the life of a turbo.
I haven't read that specifically, but it could play a part. The major difference is that a turbo is on the front side of the throttle plate and pressure "backs up" against the throttle plate and "rebounds" into the turbo. Where a PD supercharger is behind the throttle plate and "lives" in vacuum when the throttle is closed.
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Old 09-05-2018, 01:13 PM   #606
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Don't remove the bypass valve. You'll be making boost at idle if you do. You won't have part throttle, it'll just be boost all the time. It'll be bad for the engine and bad for the supercharger.
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Old 09-05-2018, 01:25 PM   #607
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Thanks guys. All that is what I figured, but I thought I read someone had removed the flap to test something.
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Old 09-05-2018, 01:27 PM   #608
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Harrop TVS86 Owners Thread

Quote:
Originally Posted by PhyrraM View Post
I haven't read that specifically, but it could play a part. The major difference is that a turbo is on the front side of the throttle plate and pressure "backs up" against the throttle plate and "rebounds" into the turbo. Where a PD supercharger is behind the throttle plate and "lives" in vacuum when the throttle is closed.


A pure vacuum exerts as much force as 14.7 psi of boost. It's the same situation, the loads are just reversed.
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Old 09-05-2018, 06:22 PM   #609
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My car dry (no gas, passengers, cargo, trunk stuff) is 2750 lbs.

Mods:
Half roll cage
Harrop SC kit
2 oil coolers
Brembo Club Racer 350mm big brake kit
Brembo GT rear big brake kit
17x9.5 TE37
heavier varis bumper (its about 3x the weight of the stock bumper)

The SC kit can't be THAT heavy...
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Old 09-06-2018, 12:47 AM   #610
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Quote:
Originally Posted by sw20kosh View Post
My car dry (no gas, passengers, cargo, trunk stuff) is 2750 lbs.

Mods:
Half roll cage
Harrop SC kit
2 oil coolers
Brembo Club Racer 350mm big brake kit
Brembo GT rear big brake kit
17x9.5 TE37
heavier varis bumper (its about 3x the weight of the stock bumper)

The SC kit can't be THAT heavy...


Stock car = 2775
- 6gal gas (36lbs) = 2734
- trunk stuff (31.2lbs) = 2702.8
- Volks likely saved ~10lbs = 2692.8

So between all the weight adders you only added ~60lbs. The half cage and supercharger are probably responsible for most of it (let's say 80%). Roll bar might be 20-30 lbs, so the supercharger comes in at about the same. That could mean this setup is significantly lighter than the Edelbrock which is often quoted at 80lbs (60lbs difference when installed, accounting for removed stock parts)
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Old 09-06-2018, 01:16 AM   #611
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http://www.ft86club.com/forums/showp...3&postcount=25

I weighed everything minus the coolant, but the 2.5L equals 5.5lbs, so everything is like 65’ish pounds plus or minus five’ish.

I also checked out the front vs rear (my car is on a Eibach Pro Kit), and the front isn’t noticeably different than before, but it might be slightly different. I just can’t tell without talking myself into seeing something that might not be there.
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Old 09-06-2018, 03:48 AM   #612
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I also checked out the front vs rear (my car is on a Eibach Pro Kit), and the front isn’t noticeably different than before, but it might be slightly different. I just can’t tell without talking myself into seeing something that might not be there.
Just got a corner balance. F:R is 57:43.
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Old 09-06-2018, 10:48 AM   #613
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Just got a corner balance. F:R is 57:43.


Meaning the front needs a plate or no?
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Old 09-06-2018, 11:35 AM   #614
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Originally Posted by PhyrraM View Post
I haven't read that specifically, but it could play a part. The major difference is that a turbo is on the front side of the throttle plate and pressure "backs up" against the throttle plate and "rebounds" into the turbo. Where a PD supercharger is behind the throttle plate and "lives" in vacuum when the throttle is closed.
Quote:
Originally Posted by Yoshoobaroo View Post
A pure vacuum exerts as much force as 14.7 psi of boost. It's the same situation, the loads are just reversed.
I think it's still a slightly different situation. In terms of the pressure ratio (P1 + work = P2), the "rebound" pressure occurs on the P2 side of the turbo and the P1 side of a PD blower without a bypass. In the case of the turbo, it's a damaging force originating on the P2 side of the turbo shaft. In the case of the PD blower, it's altering P1 which should harmlessly lower P2 if it's assumed the idle air feed has been adjusted correctly to not choke off the blower (which is a different scenario than a damaging momentary spike in pressure). It's still a bad idea as johan pointed out.
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Old 09-06-2018, 01:19 PM   #615
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I think it's still a slightly different situation. In terms of the pressure ratio (P1 + work = P2), the "rebound" pressure occurs on the P2 side of the turbo and the P1 side of a PD blower without a bypass. In the case of the turbo, it's a damaging force originating on the P2 side of the turbo shaft. In the case of the PD blower, it's altering P1 which should harmlessly lower P2 if it's assumed the idle air feed has been adjusted correctly to not choke off the blower (which is a different scenario than a damaging momentary spike in pressure). It's still a bad idea as johan pointed out.
The other important thing the BPV does is allow the blower to not be doing work. I.E. keeps the temperature of it down.
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Old 09-06-2018, 02:02 PM   #616
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The other important thing the BPV does is allow the blower to not be doing work. I.E. keeps the temperature of it down.
Yep, leaving the only power consumption by it as the small frictional losses from free-spinning.
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