To run an external wastegate, wouldn't it be better to place it in the up pipe before the turbo instead of in the downpipe? I'm planning on building a larger downpipe and running an external gate, but have not seen it in the up pipe, but that would be where i would think it should go. Any thoughts. Sorry if its a noob question, but every downpipe i've searched that uses an external wastegate is off the downpipe itself.
External wastegate question
- Thread starter 8AV8OR2
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gate has to be off the exhaust side to stop the turbo from making the boost , common is off the wastegate hole in the turbo exhaust housing (along side the downpipe outlet) but for larger turbos the housing hole can be too small to control boost so they take it off the passenger header before the turbo
bovs go in the upipe to lessen backsurge after boosting when the throttle blade is slammed shut
bovs go in the upipe to lessen backsurge after boosting when the throttle blade is slammed shut
sorry, i should have mentioned its for a hot air car, the up pipe i was referring to is from the passenger header to the turbo.
like this? this is my new setup.
i cant give you the whole picture its my little secret. 
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id like to put a bov on my 79, i assume it'd work the same on a carb/turbo car? most aftermarket valves ive found come with a flange, i just need to have it welded into the up pipe? should i wory about it ading alot of heat to the underhood area? can i dump into the fenderwell?
gnbooster87
its only a six
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like this? this is my new setup.
common bro its still a hot air it cant be that fast that you should keep it a secret
its just my little project thats all. i will post more pictures when i see the car.
like this? this is my new setup.
Pretty much what I was thinking myself. Could you send me a pic of the whole thing, I'd like to see it and I won't tattle on ya.:biggrin: The only diff is I was going to move the wastegate a little closer to the turbo.
79Ghost, you can't put a BOV on a carb/turbo without risking fire. A BOV goes in the presure side of the intake so you'd blow fuel out when it popped.
Not a good idea for sure.i will send you a picture sometime
Be waiting on it.:biggrin:
i understand. but... the wastegate, is to relieve pressure when you get off the gas, cant you relieve the pressure before the turbo to serve the same point? i dont want to vent the pressure after the turbo because , your right, it has gas in it. will venting before the turbo serve the same purpose as after? im more curious than ready to start cutin and weldin.
dr_frankenstein
Mad Scientist
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the wastegate opens and closes while the engine runs to maintain a certain amount of boost. it either opens and bleeds excessive exhaust pressure off, or stays closed to build exhaust pressure. It doesnt nessacarily relieve pressure when you let off the gas. This all happens on the hot side of the turbo, the turbine.
On A carbed turbo system, as charlie stated, there is a flammible mixture under pressure after the turbo- but before the turbo inlet is where the carb plenum is located, this area is under vacuum, so adding a BOV is going to ruin your metering signal and cause a huge lean spot because your relieving vacuum, not pressure. This is the cold side of the turbo, the compressor.
hope that helps, PM me if you have other questions.
:biggrin: A.j.
ok so theres a hot air side and a cold air side, right. on the hot air side, before the turbo is where i would bleed off pressure using a bov/wastegate, right. thats why you say the bov bleeds off exhaust pressure?
I dont want to belch fire every time i get off the gas, i Know i cant vent the intake charge. it kinda went without saying, but thanks for your concern Charlie. I dont even know where could i put a bov on the cold side of the turbo? its a busy area!
I dont want to belch fire every time i get off the gas, i Know i cant vent the intake charge. it kinda went without saying, but thanks for your concern Charlie. I dont even know where could i put a bov on the cold side of the turbo? its a busy area!
OK, we'll try this again. To use a BOV you only want to get rid of excess AIR not air/fuel. Since you're a draw through turbo there is no place on the car where there is no fuel in the system. If you put one on it, it needs to be between the turbo and the intake and when you vent you'd have to blow it into the exhaust for safety. Interesting way to create a back fire but it wouldn't be pretty.
As far as a wastegate is concerned it doesn't blow excess presure when you get off the gas, it relieves the presure as the engine rpm increases and the turbo increases in boost level. This keeps the turbo from producing to much boost and killing the engine.
A BOV and a Wastegate aren't the same thing. Think of a BOV as a presure release kinda like the the one on a water heater. If the heater is getting to hot the valve pops and releases the presure to keep the tank from blowing up. A BOV allows for the excess presure of you getting of the gas to escape and vent to the atmosphere to prevent the presure from reaching the turbo. On a carb/turbo you'd have to put the valve in the turbo neck to achieve this and then vent compressed air/fuel mixture. A wastegate is used on the turbo to allow the turbo to reach a specified presure and only that presure. Depending on which wastegate you have on your car (there are 2 different ones for carb/turbo) will depend on how you reach the specified presure. One is normally closed and is used in most of the carb/turbo set ups but in 81 GM decided for better economy to have a normally open one and it sucks performance wise. Now that it's clear as mud come to the before black section and do some reading and ask some questions there.
Sorry about the hi-jack guys.
T- Type Tim
Vice Chairman
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here is my setup.... yes i know the downpipe is not bolted on... i'm still waiting for my front spings to come in so it does'nt hit the upper a arm like it does here with the cut springs...... i'm going to probably put a turn down on the wastegate pipe and get it chromed when i'm not so busy.....no secrets withheld here
