Waste gate adjustment?

[Dragon Humper]

The turbine and impeller never change direction or slowdown or any wierdness like that. The amount of inertia in that assembly turning at 80,000 rpm is incredible. What is happening is the slug of charged air in the system is "springing" and the time that the air changes from the spring out to the recoil cavetates the exducer (not the inducer) for a split second and creates a small sonic boom. That is why it doesn't cause any damage. The fins are very short and thick in the exducer area.



Jon.

[Cuami]

That mild compressor surge (flutter sound) still does some damage, as from what I understand the rotating assembly (CHRA) is violently slowing down and accelerating again.

The worst form of compressor surge is at higher rpm that can damage engine, turbo, for example on a Skyline -

http://www.youtube.com/watch?v=nCj6Spwl1CU

The purpose of the BOV is to recirculate the air so it goes back through the turbo, which allows the turbo to maintain the rpm during a shift, so when get back onto throttle the hesitation (turbo getting back up to speed as more rpm = more boost with a turbo) is eliminated or reduced. This can be measured / checked on a hub dyno with transient hp. That's what the Synapse BOV does really well and there's no lag when back onto throttle (just like it was at factory), the engine, car just accelerates (increases the transient hp).

The stock MAF setup is a draw through MAF setup which needs a reciculating BOV, so once air behind MAF is reduced or increased, the ECU has no idea that it has.

With MAP setup it takes it from the MAP sensor on intake manifold, so any change in amount of air in intake piping can be detected at intake manifold, compensated by the ECU which results in a steady idle, etc.

On some American made engines they run both map sensor at intake manifold, draw through MAF setup.

The other MAF setup is the blow through MAF setup with MAF inbetween intake manifold, intercooler (using a Ford Racing MAF that's rated at 700hp which stock ECU can run).

That would be a more in depth explanation of what a BOV does as a whole and is some really good info... But that dyno run is an absolute worst case scenario. Many turbos are equipped to handle themselves without a BOV (I.e. Anti-surge tech)... But I can't say to what extent since I haven't tested their limits.

That said, I personally wouldn't risk thousands of dollars by not running a BOV... Especially if I'm running high boost and/or revving high in the rpm range.

That Ford MAP/MAF combo is a great idea... I'd have to look into that some more. Are you saying that the skyline's stock ECU can handle this setup?

[Skym]

That Ford MAP/MAF combo is a great idea... I'd have to look into that some more. Are you saying that the skyline's stock ECU can handle this setup?

It's a MAF option in Nistune tuning software with Nistune installed inside stock ECU (makes the older stock ECU retuneable / reflashable like most new car stock ECU's).

The Ford Racing MAF has a weld on adaptor plate (can buy them in America) for mounting MAF sensor into intake piping. The size of intake piping is important too, as the FORD Racing MAF is supposedly really sensitive to slight changes in air and is fitted to big diameter intake piping. It's the MAF Ford Racing use on supercharged V8 engines.

Here's a blow through (can be seen around 1:14) Ford Racing MAF setup (stock ECU with Nistune) with RB20DET in America and engine has cams, front facing intake manifold, etc -

https://www.youtube.com/watch?v=k2cREcerhyk