turbos, wastegates, and blow off valves.

in the never ending quest to learn as much as i can,
i was on garrett's homepage the other day reading about turbos and what not.

if i understand it correctly, we use a wastegate to bleed off unwanted pressure on the exhaust side.
how much pressure is really "unwanted"?
my 093 only produces 10 psi. if i disconnect the WG what pressures would i see?
what problems will occur?

also.
ive never seen a diesel with a blow off valve.
to me it seems like we would want a blow off valve, more than a waste gate!

any insight?

All I can really answer is if you disconnect it you can probably see 15+ PSI. I'm also interested in the other questions.

ill have to give it a shot today......
see what kinda pressure it will push

ive never seen a diesel with a blow off valve.

Most all big rigs that have an exhaust brake on them have a blow off valve.

I'm going to take a stab at this so please dont beat me up too bad if I'm wrong. From the reading I have done, as you said the waste gate bypasses a portion of the exhaust as determined by the amount of boost pressure. I don't think the hypermax turbo was wastegated. The 093 and the second gen banks were. I believe the reason for a blow off valve is to prevent over boosting off throttle. Think drag car doing a burnout... a quick burst of throttle the turbos spool up and then you let off. The turbine is still spinning and compressing the air as the throttle is closed but there is no place for it to go so you get a big pressure spike that will pop the intercoolers. I guess in the case of the diesel, there is no throttle blade to stop the boost from building up so no problem. It just gets stuffed in the cylinders.

BOV arew used on gasoline engines because they have a throttle. when you suddently close the thorttle there is a pressue spike in the cold side, the BOV will dump that pressure, preventing the "turbo surge sound", of air slowing down the compressor blades. Real ******* bearings.
I am not familiar with big rigs, however it would make sense witht eh exhaust brake, as you restrict the total amount of gasses leaving the engine, making it harder to charge air to be pushed in-this would act "like a throttle". \
You can hear turbo surve on pulling turcks after their big pull, you hear the Too too too too sound. So much mass is being pushed thru at high rpm-you cut the fuel and the engine slows down, that large amount of charged air will push back on the compressor. a BOV would be good in this sitation as well. However alot of these turcks have relief housings, which acts in a similar manner to diver tthe air to atmosphere versus thru the compressor blades.


fancy omne

more traditional one (my hx35 has this)

OLDBULL8 said:

ive never seen a diesel with a blow off valve.

Most all big rigs that have an exhaust brake on them have a blow off valve.

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laserjock said:

I'm going to take a stab at this so please dont beat me up too bad if I'm wrong. From the reading I have done, as you said the waste gate bypasses a portion of the exhaust as determined by the amount of boost pressure. I don't think the hypermax turbo was wastegated. The 093 and the second gen banks were. I believe the reason for a blow off valve is to prevent over boosting off throttle. Think drag car doing a burnout... a quick burst of throttle the turbos spool up and then you let off. The turbine is still spinning and compressing the air as the throttle is closed but there is no place for it to go so you get a big pressure spike that will pop the intercoolers. I guess in the case of the diesel, there is no throttle blade to stop the boost from building up so no problem. It just gets stuffed in the cylinders.

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Makes sense to me.

IDIoit, don't be your username and pop a HG because you were "trying something"

ahhhh throttle stops/butterflys on gassers..... i didnt think about that
and it all makes sense!
i dont think ill ever install an exhaust brake on my rig, i can always downshift and scatter my ZF5

sherwin johnson said:

Makes sense to me.

IDIoit, don't be your username and pop a HG because you were "trying something"

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HAY MAN ITS MY TRUCK!hahahahhaah

I AM A PROFESSIONAL IDIOT!!!!!!


its all in the interest of learning, the more you screw up the more you learn!!!
ive already tried adjusting the WG arm, but didnt see any positive results.
perhaps i should wait till i have a spare engine ready to go before i start experimenting...

IDIoit said:

i can always downshift and scatter my ZF5

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Say it ain't so! Don't be that guy!

gives me a reason to buy a set of head studs tho lol

Yeah how's your "preemptive strike" build a-goin' for ya?? You mean you've been doing other stuff?????

i still havnt found a core.
ive been searchin tho!
give me a break! ive done ALOT of work on my truck, and still alot more to do.
to be honest, my new 7.3 will be in the same catagory as my pontiac 472.
ive been collecting parts over the past 5 years, spent over 7 grand on it! lol
ive got everything for it but a cam, and machine work... but im saving up to either get a new set of heads, or to have mine ported to flow 350+ cfm.
id do it myself but i dont have a flow bench.

my WMO project will most likely be next before the new moose monster(if i can call it that without getting castrated by Mel) lol

IVE BEEN DOING LOTS OF OTHER STUFF!!!!
power windows in the 87,
69 dodge charger
building a 410 FE engine for my boat,
and 60 hours a week at work!
not to mention taking care of the prego woman!

IDIoit said:

power windows in the 87,
69 dodge charger
building a 410 FE engine for my boat,
and 60 hours a week at work!
not to mention taking care of the prego woman!

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Do you sleep??

yes sir... from 10 pm till about 4 am.
if i sleep any more than that, i feel as if im hung over....

i need to get this SOB done... starter should be in today

screw headers on dead or dying go cart engines!