wastegate actuator questions.
- Thread starter cody c
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because blow-off valves are to keep the pressurized volume of air between the turbo's compressor wheel and the intake valve (pressure built up by the turbo's compressor wheel) from stalling the compressor wheel. when the carb or throttle body's throttle plate suddenly closes (when you let off the gas), it traps the pressurized volume of air between the now-closed throttle plate and compressor wheel, stopping it same as a water wheel would stop if the water it was pushing couldn't head down stream anymore. compressor wheels don't like being stopped suddenly (stalled), and stalling eventually (or sometimes more immediately) breaks them.
a normal diesel engine doesn't have a throttle plate to regulate the volume of air that comes in, as diesels don't care (within a wide range, anyway) how much air comes in, as long as it's enough...a diesel's speed and power is regulated strictly by the amount of diesel fuel injected, so they don't need a throttle plate. put another way, gasoline has to have a certain fuel/air ratio to run at all, but diesel fuel will burn about the same with a wide range of fuel/air ratios. in a gas motor, the throttle plate regulates the amount of air allowed in, and an amount of fuel proportional to that amount of air is added to that air. in a normal diesel, the motor is allowed to suck as much air as it can for a given rpm, and the fuel is injected COMPLETELY INDEPENDENTLY of how much air is coming in, because the air fuel ratio just almost doesn't matter. no throttle plate means no compressor stalling (well, much less likely and of less severity), so no blowoff valve needed.
now, a 3B (and it's the only diesel I've heard of that does this) has a throttle plate, which is used to generate a vacuum signal much as a carburetor does, which is uses to regulate the amount of fuel injected much as a carburetor does, though not in the same way(dunno why Toyota/Bosch decided to do that, probably as a way of regulating fuel to actual load better, given a no turbo configuration).
so, a turbo on a 3B would benefit from a blowoff valve after all, to keep the compressor wheel from stalling and eventually failing.
oh, yeah...also, even if the compressor wheel would stand the repeated stalling, stalling means you're stopping the compressor wheel from spinning, so you'd have to re-accelerate the compressor wheel every time you got on the gas to make any boost, which contributes to turbo lag.
Steve
a normal diesel engine doesn't have a throttle plate to regulate the volume of air that comes in, as diesels don't care (within a wide range, anyway) how much air comes in, as long as it's enough...a diesel's speed and power is regulated strictly by the amount of diesel fuel injected, so they don't need a throttle plate. put another way, gasoline has to have a certain fuel/air ratio to run at all, but diesel fuel will burn about the same with a wide range of fuel/air ratios. in a gas motor, the throttle plate regulates the amount of air allowed in, and an amount of fuel proportional to that amount of air is added to that air. in a normal diesel, the motor is allowed to suck as much air as it can for a given rpm, and the fuel is injected COMPLETELY INDEPENDENTLY of how much air is coming in, because the air fuel ratio just almost doesn't matter. no throttle plate means no compressor stalling (well, much less likely and of less severity), so no blowoff valve needed.
now, a 3B (and it's the only diesel I've heard of that does this) has a throttle plate, which is used to generate a vacuum signal much as a carburetor does, which is uses to regulate the amount of fuel injected much as a carburetor does, though not in the same way(dunno why Toyota/Bosch decided to do that, probably as a way of regulating fuel to actual load better, given a no turbo configuration).
so, a turbo on a 3B would benefit from a blowoff valve after all, to keep the compressor wheel from stalling and eventually failing.
oh, yeah...also, even if the compressor wheel would stand the repeated stalling, stalling means you're stopping the compressor wheel from spinning, so you'd have to re-accelerate the compressor wheel every time you got on the gas to make any boost, which contributes to turbo lag.
Steve
cody c said:
- Thread starter
- #23
so the blow off valve is to protect the turbo from a sudden stall, not to regulate boost or turbo speed which is probally the wastegates job. but do you think that a blow off valve might protect from to much boost pressure and stalling by itself without a wastegate?
precisely. blow off valves aren't normally used for boost control...not being an engineer involved with designing turbo boost control systems, I can't really comment on WHY they aren't used for that, but on the street, they aren't. if I had to guess I'd say that they probably don't do a very good job of it. dunno about racing...
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theSherpa said:
Probably because a blow off valve will be quite noisy (the excess pressure is vented externally of the intake) as opposed to a wastegate which keeps everything sealed up;. But I don't see why a blow off valve wouldn't work fine as a protection against overboosting, and would be much easier plumbing-wise than retofitting a wastgate.
- Thread starter
- #26
just went to napa and mopac and searched ebay, this is what i can tell you : blow off valves on ebay start at $10, mopar $150, napa doesnt have em, wastegates at mopar start at $350 ebay again a little better price wise and napa doesnt have em. second: aparently the blow off valve does use vacume pressure from the throttle body "past the throttle body valve" to help open it. like a push and pull effect from either side of a diaphram although its more of a spring loaded piston, and so this can mostly be activated when you would take your foot off the throttle in a gasser, creating vacume to help open the blow off valve. if all blow off valves are built this way i doubt it. but the aftermarket ones at mopar do.
i think im not gonna install the wastegate or blowoff valve for a while, i'll get the turbo installed and see what the pressures and temps are and if theyre too much ill find a wastegate.
third if you sheared 6 studs 4x4ing on the weekend like i did napa has em for less than $3 and chrome acorn style nuts for about the same whereas toyota is over $11 a piece. finally i got the 2.5" flowmaster hushpower 2 exhaust at mopar for $175 cad. now i just gotta find the time to install all the crap. by the way i had a look at an old 3b block and how the oil moves throgh the oil galley, it flow from the pump to the filter and from their it splits to the front and to the back not from the back off the block forwards.
i think im not gonna install the wastegate or blowoff valve for a while, i'll get the turbo installed and see what the pressures and temps are and if theyre too much ill find a wastegate.
third if you sheared 6 studs 4x4ing on the weekend like i did napa has em for less than $3 and chrome acorn style nuts for about the same whereas toyota is over $11 a piece. finally i got the 2.5" flowmaster hushpower 2 exhaust at mopar for $175 cad. now i just gotta find the time to install all the crap. by the way i had a look at an old 3b block and how the oil moves throgh the oil galley, it flow from the pump to the filter and from their it splits to the front and to the back not from the back off the block forwards.
theSherpa said:
I second the noise issue. They let of a huge phllssssss noise everytime.
They are more of a dump valve, and not really a moderated(variable) device.
You are going to need a wastegate. Either way the hole below the turbine discharge will have to be blocked.
Have you looked for the other pieces for it? From a wreaking yard....
- Thread starter
- #28
i was thinking of cutting some plate and getting a 90 degree piece of pipe for the drop. the plate would block the bypass and then id weld a flex joint to the bottom of elbow. i guess it cant hurt to call a couple junk yards though to see if they got something. by the way is your merkured 3b rolling now? im curious to see what the power difference is that im gonna get out of it.
filter looks same as mine.
no my truck isn't running yet.
nice gauge set up !
One of the biggest pains in the arse is the heater lines. As you notice in your pics they all have to be reloctated.
I am not done relocating yet.
no my truck isn't running yet.
nice gauge set up !
One of the biggest pains in the arse is the heater lines. As you notice in your pics they all have to be reloctated.
I am not done relocating yet.