slowmedown;1350592 said:
Nope! And what's your logic behind one recirc bov and one non recirc bov?
Antisurge/Ported Shrouds
- Thread starter Doward
- Start date
Nope! And what's your logic behind one recirc bov and one non recirc bov?
In this pic of my billet turbo you can just barely see the port line. It is just above the smaller set of fins, but below the larger ones.
My BOV is adjustable and I was able to only put a small amount of spring pressure on it so it opens and vents low boost very easily, but still holds 24psi without leaking.
My BOV is adjustable and I was able to only put a small amount of spring pressure on it so it opens and vents low boost very easily, but still holds 24psi without leaking.
Doward;1320125 said:
There are several runs on SF where non surge covers make more power. If you think about it it makes perfect sense, the turbo can only flow so much, if you induce a leak (surge port) the air will leak through there and less flow reaches the engine.
I'll look later tonight. But garrett states that you'll have a minor impact on efficiency.Doward;1350877 said:
tekdeus;1350949 said:
I would say less then 5%, more in the 2-3 range.
With small turbos there is no reason to run a ported cover. But if you have a larger turbo, it (having a ported cover) would out weigh the benefits of a non ported cover however.
I'm not sure where the 7m starts running into surging problems. My 1jz with a 67 would surge just a tad in 5th ~ 4000 or so.
in response to the video:
i don't understand it. what are they doing throttle wise just to make it surge like that? They said they closed the bovs to ensure that they were not a factor, but that in itself is the factor to me. If the excess air cannot be released then of course its going to surge like that.. i'm so lost. :1zhelp:
i don't understand it. what are they doing throttle wise just to make it surge like that? They said they closed the bovs to ensure that they were not a factor, but that in itself is the factor to me. If the excess air cannot be released then of course its going to surge like that.. i'm so lost. :1zhelp:
Supra_Villan;1351666 said:
It's really simple man...don't over analize it! That particular turbo is pumping more air then the motor wants...therefor the pressure wants to excape and it only has two places to go....either the motor takes it or the air backs up and forces itself back out the turbo....
The other type of surge is when the throttle closes and all that fast moving air and pressure bounces back and reverses travel towards the turbo....which is why gas motors have bypass valves, blow off valves, and or some crazy badass shit antilag system that routs that air into the exhaust mani....
The ported shrouds let you force even more air in as it has en escape route for air....the turbo sucks it back in ofcourse as to not create a boost leak.
Poodles;1352090 said:
Which is why I told him to not over analize...yes there will be a point where it just won't be able to breath anymore air and proceed to chop air causing massive turbulance ect....
Another way to explain this would be why helicopter can't hover for prolong periods very close to the ground as it causes a massive vortex and the blades just start chopping instead of "flying".
Poodles;1352686 said:
It sure is, with steady state. Note how rpms shoot up to 4k (held by the dyno even at WOT), and then boost builds. Look closely at the start of the video, you can see the a Dynapack attached to the rear hubs. They even say it in the text "On Load, On boost..."
The turbo spools fine for a bit before the charge starts stacking up, it's the chirping that is surge.
Great find however, I've never heard it so clearly.
Interesting how in the video, the surge slammed the boost from 20psi to 15psi in an instant, and caused dips in power to show on the dyno graph.
I believe the turbo in the video did not have an antisurge housing. This is why they make turbos with antisurge/ported shrouds
marcusgnf;1353062 said:
I believe the turbo in the video did not have an antisurge housing. This is why they make turbos with antisurge/ported shrouds
