Maybe that's what's wrong with me. I always feel exhausted. I tried working late to shorten the night but I quit making good decisions about 11pm. Might have the bite the bullet and get on an early schedule again. Well, enough hijack...
turbos, wastegates, and blow off valves.
- Thread starter IDIoit
- Start date
im the same way, about 10 pm i am useless... i go into the shop and put in 4-5 hours before my employees come in @ 8:30, i cant get nothing done when there here.
except for office crap! i have a big pile of paperwork to do today, but i ran most the jobs myself, so i know i made money...
jobs that i dont do, i almost make shop rate, but im not losing my ass either. and well, i dont have to do them.
i would go nuts if i was on the production line again.
except for office crap! i have a big pile of paperwork to do today, but i ran most the jobs myself, so i know i made money...
jobs that i dont do, i almost make shop rate, but im not losing my ass either. and well, i dont have to do them.
i would go nuts if i was on the production line again.
whiteboyslo
FNG
As has been mentioned, diesels don't need BOVs because there is no throttle plate. Throw all the air you want down a diesel engine. Until you add more fuel with your right foot, it's not doing anything but pump it through.
Wastegates allow you to use turbo designs that spool up quicker without the worry of creating too much boost or spinning the turbo at too high of a RPM. Upside is the boost is much more immediate, especially at lower RPMs (relative to non-WG turbos), plus it regulates max boost for you. With a non-WG turbo, a bit more R&D has to go in to making sure the turbo won't create too much boost once it's really cranking. Downside to a WG setup is it's a smaller housing, meant to spin to higher RPMs with less air flowing through it. So, if you start messing with the WG or the WG fails, you run the risk of basically overclocking the turbo and causing premature failure.
BTW, not all Sidewinder (aka Banks 2nd gen) systems are WG. WG was an option. I have a non-WG Sidewinder setup in my truck.
Mike
Wastegates allow you to use turbo designs that spool up quicker without the worry of creating too much boost or spinning the turbo at too high of a RPM. Upside is the boost is much more immediate, especially at lower RPMs (relative to non-WG turbos), plus it regulates max boost for you. With a non-WG turbo, a bit more R&D has to go in to making sure the turbo won't create too much boost once it's really cranking. Downside to a WG setup is it's a smaller housing, meant to spin to higher RPMs with less air flowing through it. So, if you start messing with the WG or the WG fails, you run the risk of basically overclocking the turbo and causing premature failure.
BTW, not all Sidewinder (aka Banks 2nd gen) systems are WG. WG was an option. I have a non-WG Sidewinder setup in my truck.
Mike
did anyone state the 12# unofficial cap on boost is to save the head bolts?
aint a bov like an wastegate in principle?
or the jake/pac brake is literally the coolest way of slowing a rig down using the engine rather than the clutch or brakes?
but sensible driving habits usually get ya farther down the road.
check out the differences between gated and non gated turbo's,,, I think the wg 093 is not much better than my ole ng banks for hauling power just quicker outta the hole...fwiw
aint a bov like an wastegate in principle?
or the jake/pac brake is literally the coolest way of slowing a rig down using the engine rather than the clutch or brakes?
but sensible driving habits usually get ya farther down the road.
check out the differences between gated and non gated turbo's,,, I think the wg 093 is not much better than my ole ng banks for hauling power just quicker outta the hole...fwiw
Heide264
Full Access Member
Nutshell: Think of a wastegate as a variable geometry turbo. It lets you keep the turbo in it's 'design range' and at a suitable efficiency throughout a wide range of operating conditions.
Long:
A turbo moves X volume of air (CFM, for example) at Y pounds of pressure (psi, for example). Different turbos prefer to move 'more air' at lower pressures or vice versa. It's a large common misconception that 12psi on turbo X is representative of 12psi on turbo Y... The important part is how much air the turbo is moving for the engine to 'injest'. This seems relatively simple, but its complicated and involves necessary trade offs. The trade offs are more of an issue the further you go from an 'ideal operating circumstance'... for example over a wide range of air flows or drive pressures such as in a gas car with a wide rev band.
A good example is my little 2.5L rice burner that I drive every day (2011 Subaru STi). While I can have the stock turbo build up to 25+ psi in the manifold at 3,000RPM and about 20psi at 6,000RPM, the turbo is too small and 'runs out of breath'. Once the engine starts injesting more air in the 3-6kRPM range, the turbo is moving more air volume than it can efficiently. Turbo inefficiency leads to excessive EGTs and normally premature engine/turbo wear (and my wallet being bent over). When air heats up, it spreads out and there are fewer air particles per volume - the air is less dense, albiet at a higher pressure. Less air particles means less air to combust. In summary, the best power for that little turbo in my setup is around 23psi at 3,000RPM and only 14-16psi at 6,000 RPM. There are a huge amount of factors in there, but the bottom line is that turbos are only efficient in certain air flows at certain drive pressures.
The ideal situation for a turbo charger is really an airplane engine or a generator. Generators run at one speed. They always move the same amount of air. You find a turbo that fits that criteria at its peak efficiency. Done. No need to release any pressures. It just goes and runs nicely. Next in line are big diesel trucks with low rev bands. Fairly ideal candidates. Not too wide of a range of operating conditions. Lastly, gasoline cars. Not only does gas explode under high pressure, but their wide rev band makes it difficult to select a turbo that is efficient over the entire range.
So back to the original question.... Turbo's, wastegates, and BOVs.
I think the BOV has been covered. It releases air form a pressurized intake tract after a throttle blade (which doesn't exist in old diesel trucks) shuts it in. There are some differences of opinions, but my general opinion is that if you have a journal bearing turbo, you should have one. Ball bearing turbos, save the cash as you'll need it after buying one.
Now the wastegate is what needed the background info. If you size a turbo out for the airflow at the redline of your engine, life is good. The turbo will be happy once it spools up and efficient. However, you are 'giving up' the power on the table you could have throughout your rev band. Normally, you size the turbo a bit smaller depending on your goals and intended use. The main idea being that a wastegate just routes exhaust gas away from the turbo turbine... hence spinning it a bit less and making less pressure in the intake manifold. This is hugely useful so you can keep a smaller turbo in its efficiency range at redline, instead of running it at higher pressures where it is generating excess heat. This can be dangerous to your engine internals AND cost you power, as the hot air under higher pressure may actually contain LESS air mass than cooler air under lower pressure.
If you guys are interested in this at all, I do all my own tuning to my 2011 STi and am an engineer and can do a few write ups on some topics. I have wrote up a few small articles related to boost control and the pros and cons of a few things for some Subaru boards. I wouldn't mind writing up a few articles to help you guys out in that sense considering the help you guys have given me mechanically.
Long:
A turbo moves X volume of air (CFM, for example) at Y pounds of pressure (psi, for example). Different turbos prefer to move 'more air' at lower pressures or vice versa. It's a large common misconception that 12psi on turbo X is representative of 12psi on turbo Y... The important part is how much air the turbo is moving for the engine to 'injest'. This seems relatively simple, but its complicated and involves necessary trade offs. The trade offs are more of an issue the further you go from an 'ideal operating circumstance'... for example over a wide range of air flows or drive pressures such as in a gas car with a wide rev band.
A good example is my little 2.5L rice burner that I drive every day (2011 Subaru STi). While I can have the stock turbo build up to 25+ psi in the manifold at 3,000RPM and about 20psi at 6,000RPM, the turbo is too small and 'runs out of breath'. Once the engine starts injesting more air in the 3-6kRPM range, the turbo is moving more air volume than it can efficiently. Turbo inefficiency leads to excessive EGTs and normally premature engine/turbo wear (and my wallet being bent over). When air heats up, it spreads out and there are fewer air particles per volume - the air is less dense, albiet at a higher pressure. Less air particles means less air to combust. In summary, the best power for that little turbo in my setup is around 23psi at 3,000RPM and only 14-16psi at 6,000 RPM. There are a huge amount of factors in there, but the bottom line is that turbos are only efficient in certain air flows at certain drive pressures.
The ideal situation for a turbo charger is really an airplane engine or a generator. Generators run at one speed. They always move the same amount of air. You find a turbo that fits that criteria at its peak efficiency. Done. No need to release any pressures. It just goes and runs nicely. Next in line are big diesel trucks with low rev bands. Fairly ideal candidates. Not too wide of a range of operating conditions. Lastly, gasoline cars. Not only does gas explode under high pressure, but their wide rev band makes it difficult to select a turbo that is efficient over the entire range.
So back to the original question.... Turbo's, wastegates, and BOVs.
I think the BOV has been covered. It releases air form a pressurized intake tract after a throttle blade (which doesn't exist in old diesel trucks) shuts it in. There are some differences of opinions, but my general opinion is that if you have a journal bearing turbo, you should have one. Ball bearing turbos, save the cash as you'll need it after buying one.
Now the wastegate is what needed the background info. If you size a turbo out for the airflow at the redline of your engine, life is good. The turbo will be happy once it spools up and efficient. However, you are 'giving up' the power on the table you could have throughout your rev band. Normally, you size the turbo a bit smaller depending on your goals and intended use. The main idea being that a wastegate just routes exhaust gas away from the turbo turbine... hence spinning it a bit less and making less pressure in the intake manifold. This is hugely useful so you can keep a smaller turbo in its efficiency range at redline, instead of running it at higher pressures where it is generating excess heat. This can be dangerous to your engine internals AND cost you power, as the hot air under higher pressure may actually contain LESS air mass than cooler air under lower pressure.
If you guys are interested in this at all, I do all my own tuning to my 2011 STi and am an engineer and can do a few write ups on some topics. I have wrote up a few small articles related to boost control and the pros and cons of a few things for some Subaru boards. I wouldn't mind writing up a few articles to help you guys out in that sense considering the help you guys have given me mechanically.
All good and valid discussion. We do get sold on the idea that a wastegated turbo is better off the line, and that is partially true. What it really means is that the exhaust housing is sized too small for the engine that it is on. That's a truth. It's done on purpose. But the real reason we have been making turbo's more complicated with elaborate measures is the emissions. Performance comes secondary, and is driven by marketing and fuel economy. But first and foremost, it is for emissions. Wastegated turbo's improve efficiency at lower RPM and reduce exhaust emissions. These wouldn't be necessary if we had aneroids as standard equipment, or drivers with emissions control programming. 
Since 98' almost every turbo made on a production vehicle has been wastegated. That was first and foremost for emissions. Wastegated turbo's have higher amounts of backpressure and higher EGT's, both of which hurt performance and economy. Then we got into VGT's Or Variable Geometry Turbo's, which basically were sized correctly, but had movable vanes to change the geometry of the airflow on the turbine wheel. Those were prone to failure due to clogging from carbon. Now the industry is getting away from that and going to basically two different turbochargers that are hooked up in parallel with a diverter valve. A small non-wastegated turbo for slow speed, and a larger non-wastegated turbo for higher speed. The diverter valve mixes or blends exhaust flow to each to produce the desired boost and desired EGT's under computer control. Naturally, these systems are increasingly complex and getting very expensive.
Since 98' almost every turbo made on a production vehicle has been wastegated. That was first and foremost for emissions. Wastegated turbo's have higher amounts of backpressure and higher EGT's, both of which hurt performance and economy. Then we got into VGT's Or Variable Geometry Turbo's, which basically were sized correctly, but had movable vanes to change the geometry of the airflow on the turbine wheel. Those were prone to failure due to clogging from carbon. Now the industry is getting away from that and going to basically two different turbochargers that are hooked up in parallel with a diverter valve. A small non-wastegated turbo for slow speed, and a larger non-wastegated turbo for higher speed. The diverter valve mixes or blends exhaust flow to each to produce the desired boost and desired EGT's under computer control. Naturally, these systems are increasingly complex and getting very expensive.
Heide264
Full Access Member
Agreed... to an extent. I would counter that it depends on the engine and it's purpose. In most factory turbo'd gas powered cars, you don't want to size the exhaust housing for full power exhaust flow because you won't have enough exhaust flow for most of your RPM band to produce any added manifold pressure. With small engines, you already need some crazy gear ratios to make a turbo'd car fun to drive and responsive and a large exhaust housing would only add to that.
Also, you may find that you need a wastegate after removing 'designed backpressure' on the engine. I actually had to upgrade to an external wastegate on my Subaru after going with a much higher flow down pipe. The internal wastegate in the turbo just would not vent enough pressure at higher RPMs and the pressures just kept climbing, despite the turbo being wayyyy out of its efficiency. That being said, the turbo on that engine is way smaller than it should be... but a 'proper' sized one may leave a few important engine parts on the road, ha.
I could see both sides of that fence, depending on your use of the truck, the engine, and the gearing of the truck. If it was a generator that only ran at one speed, I think we both agree a waste gate or any other variable geometry turbine would be a silly addition.
Definitely in agreement here.
It comes down to the fact that if you are expecting (or in the case of emissions testing, requiring) a turbo to be in its prime in different operating conditions, say 1000RPM vs 3000RPM, you will quickly find that turbo chargers are not magical devices. You will either need to vary the geometry of the turbo (via a list of options - a waste gate being the easiest but with drawbacks) or switch to a more suitable 'multi' turbo charger system as needed.
you guys are awesome. now all that information, it may take me a day or two, and countless times re-reading everything to let it soak into my thick head...
i appreciate everyones input!
i appreciate everyones input!
As to the gasser talk I agree.
I think mel nailed it!
The first gen banks c-6 was way nicer to long haul with than the 093. 5 gear.( even tho the 6 is why i sold the 88)
I can say my idi. comes outta the hole just fine for my needs, if I load it to 18k gvw its still slow from a stop. The banks and c6 made ya use low to get boost up.
The gasser deal is another ball of wax tho'
Heide 264 has a point for a sparkplug auto.
As fo the vvt turbo ford played with my oldest is a ford master tech And he told me back when they were new about coming up on boost well new then you drove it home.
Just another Reason why ford has had so many diesel trucks ( the epa)
I think mel nailed it!
The first gen banks c-6 was way nicer to long haul with than the 093. 5 gear.( even tho the 6 is why i sold the 88)
I can say my idi. comes outta the hole just fine for my needs, if I load it to 18k gvw its still slow from a stop. The banks and c6 made ya use low to get boost up.
The gasser deal is another ball of wax tho'
Heide 264 has a point for a sparkplug auto.
As fo the vvt turbo ford played with my oldest is a ford master tech And he told me back when they were new about coming up on boost well new then you drove it home.
Just another Reason why ford has had so many diesel trucks ( the epa)
These are the best explanations on turbos I have ever read. 
Heide264, I would enjoy reading any further tech articles you can write on this subject.
Heide264, I would enjoy reading any further tech articles you can write on this subject.
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Heide264
Full Access Member
Most "sparkplug auto" info I know in regards to turbos has come out of diesel based books written by people who have worked on diesel turbo systems most of their life. There are many reasons for that. Just saying... Its all the same basic concepts. Gas engines just show the limitations of turbo charging more readily and make great case studies that people can relate to.
FYI, if anybody is actually interested in this stuff, pick up a copy of "turbo: real world high-performance turbocharger systems" by jay miller. Its a fairly quick read, cheap, and way more coherent than I could be.
EDIT: I'll give it some thought and see if I can draft something up in the near future. Always good to get some good discussions over this stuff going.
little questions big info haha but good info
without typing a book
BOV release pre throttle plate boost pressure from the turbo inter-cooler piping when the throttle plate closes (for shifts or stoping)
ppppppssssssshhhhhhhhtttttt
my greddy on my 2.0 talon is external and sounds amazing
Waste gates are to control boost (and back pressure pre-turbo)! plain and simple.
without the use of a waste gate you loose performance.....why you ask?
Non-wastegated turbo's for diesels are designed with such a large exhaust housing that the turbo cant out spool (for instance with the old banks kits) lets say 10 psi at full load/power. These designs lacks efficiency :/
waste-gated turbos are often designed with exhaust housings smaller than that of a non waste gated to improve spool time by pushing more air through a smaller space spinning the turbine wheel faster quicker. When spool time is improved greater boost levels are reached sooner than nonWG designs. When a specific amount of back pressure or set boost pressure is reached, the gate opens releasing the unwanted excess pressure from the exhaust system pre turbo and directing it (bypassing the turbo) into the rest of the exhaust and out the tail pipe.
Stoping the wastegate from opening and/oor doing its job can and will result in over boosting depending on the size of your exhaust housing and turbo. Some guy on here hit 22psi with his ats i believe? idk if thats a modded turbo but you probably dont want that much boost. Also turbos have efficiency ranges as stated above, once you pass that range (specific cfm at specific psi) you get whats called "boost spikes" your pressure can be all over the board and it will reck your turbo (compressor surge is what this is called).
because of the smaller exhaust housing on the wg'ed design not only do they spool faster but they often push high boost numbers, for example the old ungated banks at 10 psi vs the new gated at 15.
Ive never seen a gas car turbo without a waste gate.
okay boost class is over i gotta go back to work
without typing a book
BOV release pre throttle plate boost pressure from the turbo inter-cooler piping when the throttle plate closes (for shifts or stoping)
ppppppssssssshhhhhhhhtttttt
my greddy on my 2.0 talon is external and sounds amazingWaste gates are to control boost (and back pressure pre-turbo)! plain and simple.
without the use of a waste gate you loose performance.....why you ask?
Non-wastegated turbo's for diesels are designed with such a large exhaust housing that the turbo cant out spool (for instance with the old banks kits) lets say 10 psi at full load/power. These designs lacks efficiency :/
waste-gated turbos are often designed with exhaust housings smaller than that of a non waste gated to improve spool time by pushing more air through a smaller space spinning the turbine wheel faster quicker. When spool time is improved greater boost levels are reached sooner than nonWG designs. When a specific amount of back pressure or set boost pressure is reached, the gate opens releasing the unwanted excess pressure from the exhaust system pre turbo and directing it (bypassing the turbo) into the rest of the exhaust and out the tail pipe.
Stoping the wastegate from opening and/oor doing its job can and will result in over boosting depending on the size of your exhaust housing and turbo. Some guy on here hit 22psi with his ats i believe? idk if thats a modded turbo but you probably dont want that much boost. Also turbos have efficiency ranges as stated above, once you pass that range (specific cfm at specific psi) you get whats called "boost spikes" your pressure can be all over the board and it will reck your turbo (compressor surge is what this is called).
because of the smaller exhaust housing on the wg'ed design not only do they spool faster but they often push high boost numbers, for example the old ungated banks at 10 psi vs the new gated at 15.
Ive never seen a gas car turbo without a waste gate.
okay boost class is over i gotta go back to work
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Heide264
Full Access Member
Hey. I tried to sum up a lot of the info in this thread and throw it in a 'compilation'. It's currently very biased with my opinion, so give it a read over when you have a nice frothy beverage and let me know if you guys have any corrections for it. I figure a bit more of a coherent write up would help out.
http://www.oilburners.net/forums/sh...-in-the-context-of-an-IDI&p=836217#post836217
http://www.oilburners.net/forums/sh...-in-the-context-of-an-IDI&p=836217#post836217
91 7three
Full Access Member
I was under the impression that non wg turbos would make higher boost numbers than a wg turbo just not as quickly. Good info
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