School me on blow off valves...
12-24-2013, 01:04 PM
#41
FormerVendor
And I may have missed if someone touched on the subject but I would always run a bypass valve pre-intercooler. Having it after is just going to be pre-heating the intercooler core.
12-24-2013, 02:08 PM
#42
9 Second Club
If the valve seals at low boost it should do the same at high boost. (No reason it would be more likely to leak at high boost because of the aforementioned difference in diaphragm vs valve area). Only reason for leakage would be a damaged seat/valve or ruptured diaphragm which would cause leakage at any boost level.
So you could potentially have a few psi more boost pushing on the valve face, compared to pressure via the intake acting on the diaphragm.
12-24-2013, 02:31 PM
#43
FormerVendor
However with diaphragm area approaching 2x valve area in most cases it would take quite a restriction for it to make a functional difference. (and at that point of course it would be better to correct the restriction rather than run a stiffer bypass spring)
12-24-2013, 04:10 PM
#44
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The higher the spring pressure, the quicker the valve will close, and the quicker you'll transition from vacuum to boost.
So for example, with a 2lb spring, at lets say 3000 rpm, it might require you to be at 40% throttle before the vacuum of the motor drops enough to close the valve and start to build boost. Granted, it might be only 1-2psi at that rpm, but 1-2psi is a lot more airflow than -1 to -2psi if the valve were open. Now with a 4lb spring, and the same 3000rpm, it might only be 30% throttle before the valve closes and you go from -3 to -4 psi to the same 1-2psi of boost since the blower is still spinning the same rpm, and moving the same amount of air.
So if you want more low end throttle response, I'm guessing going with a higher tension spring will help it snap into a positive airflow scenario. I'm figuring that the tuning will need to be adjusted as well since the parts of the VE table at different rpms will be different, so keep that in mind.
So for example, with a 2lb spring, at lets say 3000 rpm, it might require you to be at 40% throttle before the vacuum of the motor drops enough to close the valve and start to build boost. Granted, it might be only 1-2psi at that rpm, but 1-2psi is a lot more airflow than -1 to -2psi if the valve were open. Now with a 4lb spring, and the same 3000rpm, it might only be 30% throttle before the valve closes and you go from -3 to -4 psi to the same 1-2psi of boost since the blower is still spinning the same rpm, and moving the same amount of air.
So if you want more low end throttle response, I'm guessing going with a higher tension spring will help it snap into a positive airflow scenario. I'm figuring that the tuning will need to be adjusted as well since the parts of the VE table at different rpms will be different, so keep that in mind.
12-25-2013, 07:15 AM
#45
12-25-2013, 07:25 AM
#47
12-25-2013, 11:15 AM
#48
Thanks. that makes sense to have one on each side of the intercooler. But I have also seen guys with 2 of them right before the throttle body. I know ECS uses the Tial QR and they build some awesome stuff, so that is probably the route I will go. Where do you race? E-town? I usally go to Island but would love to hear that setup in action.
12-25-2013, 02:54 PM
#50
Thanks. that makes sense to have one on each side of the intercooler. But I have also seen guys with 2 of them right before the throttle body. I know ECS uses the Tial QR and they build some awesome stuff, so that is probably the route I will go. Where do you race? E-town? I usally go to Island but would love to hear that setup in action.
They lent me Q's and QR's plus a few springs so I could find the combo I was looking for. Good guys over there.
I race @ E-Town, Atco, and Cecil.
12-27-2013, 09:12 AM
#53
Well, I was always curious if I had any boost leaks, and I sure do. My IAT sensor is leaking badly, as well as the proflo. I need to do some testing and exploring today to see why the proflo is leaking as bad as it is, but honestly, at this point, I'm planning on going with a TiAL Q, so I'm not sure it's worth the effort to figure out. My IAT sensor has been on my to-do list to change as well since it reacts so slowly. I see very little change at all doing a full pull from ambient, with or without the meth turned on. So it's accurate, but just reaaallllllyy slooooow.
Here's my boost leak discoveries:
I'd bet that's a solid 1-2+ psi loss at higher rpms, which could be the reason I saw the nose over above 5000rpm on the dyno.
Here's my boost leak discoveries:
I'd bet that's a solid 1-2+ psi loss at higher rpms, which could be the reason I saw the nose over above 5000rpm on the dyno.
12-27-2013, 10:32 AM
#54
9 Second Club
What are you actually sealing against ?
ie, it's pressurised from where to where exactly ?
Weird the valve is leaking, as long as the seat is good and there is boost and spring pressure on top, it should be sealed.
ie, it's pressurised from where to where exactly ?
Weird the valve is leaking, as long as the seat is good and there is boost and spring pressure on top, it should be sealed.
12-29-2013, 10:07 PM
#55
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12-29-2013, 11:20 PM
#56
So you are saying the lighter the spring, the faster you will get into boost? Your supercharger has one job compress air. The only way to make boost is to allow compression of air, and not expelling air to atmosphere. The sooner that is done, the quicker you can build on that. Please explain why you think waiting on a lighter spring to close the diaphragm in turn spends less energy building boost?
I have such a light spring in mine because I dont like the constant sound of the bov and never want my compressor in surge.
12-30-2013, 10:13 PM
#58
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Compressors are work consuming devices, ie, they require power to drive them. If you decrease the amount of work they are doing (in this case by lowering the pressure ratio they operate at by having a big boost leak (the bov open)) you thereby increase the difference in power generated by the turbine and the power required by the compressor the whole system has a greater imbalance and will accelerate faster. You basically skate up the right side of the compressor map while the bov is open and move back to the left once the valve closes. This allows the turbo to accelerate up to speed faster. In theory at least.
I have such a light spring in mine because I dont like the constant sound of the bov and never want my compressor in surge.
I have such a light spring in mine because I dont like the constant sound of the bov and never want my compressor in surge.
12-31-2013, 06:49 AM
#59
for the love of god please stop using turbo interchangeably when talking about a supercharger. it's two entirely different induction mechanisms. a compressor map is usually based on compressing air and building boost. you won't be skating up any compressor map until you get out of vacuum. you essentially have a hair dryer when releasing to atmosphere.
12-31-2013, 07:53 AM
#60
for the love of god please stop using turbo interchangeably when talking about a supercharger. it's two entirely different induction mechanisms. a compressor map is usually based on compressing air and building boost. you won't be skating up any compressor map until you get out of vacuum. you essentially have a hair dryer when releasing to atmosphere.
So with that aside, you are correct you will have exactly a hair dryer (high flow, low pressure) until you close the valve increasing pressure the turbo sees. The difference is the time it takes to do it this way versus normally climbing through the map. A supercharger wouldnt care as its not time dependent.
Last edited by Atomic; 12-31-2013 at 08:05 AM.