MAP vs MAFS, Recirc vs Atmospheric, BOV vs no BOV

[Daniel1458]

kelaog and tokes, thanks, got the point.

I just newer heard about "over spinning" turbos. I never thoughts that for turbos it "IS" a problem.

[kelaog]

kelaog and tokes, thanks, got the point.

I just newer heard about "over spinning" turbos. I never thoughts that for turbos it "IS" a problem.

It's not the spinning necessarily that is the problem. It's just they aren't designed to operate efficiently at that speed. Therefore they overheat and break down, or just can't tolerate the force and snap shafts.

Heat kills everything, more speed = more heat. :P. Hey but in an ideal world your setup would probably work more efficiently at regulating boost pressure. It's not a bad idea, just not practical in the real world.

[GTR-Dad]

Exhaust backpressure is your enemy. Compressing more air volume than you need to is your enemy. Spilling air _after_ it's been compressed increases both. Spilling exhaust you don't need moves both parameters in the right direction.

Good on ya for trying to think of better ways to do things. It's how improvement and breakthoughs happen.

Cheers,
Dan

[kelaog]

I guess what could work is having almost a recirc valve venting air opposite ways to the turbo to be used as a method of slowing down the intake propeller... :P Wouldn't this in theory work as a way of controlling boost and turbine speed? Probably less effective than a waste gate but "an option" not a good one though haha :P

[christdeyoung]

So if you didn't run a BOV, would this mean that you should shift fast every time?
Does a BOV still add reliability to a modern turbo?

[Velders]

As far as I know, if you have no BOV the faster you shift the better. This is because without a BOV when the throttle plates are closed a pressure wave resonates between the throttle and the turbo compressor. Each time the wave travels back to the compressor some of the built up pressure is lost. So when you shift quickly less pressure is lost, therefore you will have less lag. Now if you are just driving normally shift as fast or slow as you want cause you don't really need instant boost going to Safeway (in theory ). Now someone should correct me if I'm wrong but I believe thrust bearings (typically older style turbo) are quite efficient at spooling quickly, but they don't enjoy rapid direction changes. Ball bearings don't really care. But the only compressor surge that is really bad for a turbo is on load, off load surge isn't a big deal. IMO

Surge under load:
http://www.youtube.com/watch?v=nCj6Spwl1CU&feature=fvst

[christdeyoung]

Thats crazy!
So if a fella wanted to cheap out and not buy a BOV for my GT40R, should I be slapped repeatedly?

[Velders]

Personally, I would be just as cheap and not bother with one. The GT40R is a ball bearing turbo anyway, so I think you would be fine. I just finished trashing the whole stock BOV system on my GTR for when my build is done. I have R34 N1's also ball bearing. Hell Wingnut got rid of the BOV system on his GTS-T with a stock turbo, and I'm pretty sure he is also running it around 1.2bar. Not sure how long he has been running this setup but it seems to be holding up pretty good anyway.

[NismoS-tune]

Wingnut's gts is gone now. -1 gts +2gtir

[Velders]

Hahaha where did it go!?