IMB951

Well, since my dad got this Turbo S, I really need to know precisely how it works if we are going to start tuning it!! So, I have all the basics of a 951 turbo system - where everything is located and such - its quite a maze of piping down there!! It's been a while since I've had my hands on an 8 valve car, much less a Turbo, so will one of you Guru's lay it down for me, 951's have the wastegate coming off the side of the headers, which relieves excess boost pressure right?, but ive also heard that most german turbo cars also have a diverter valve, now is that the same thing?! Then I hear about a blowoff valve with all the ricers, but are they all essentially the same device?!!

Also I regularly see what looks to be a wastegate on the side of the hard intercooler plumbing on a beefed up 951 engine picture....?!

Fishey

http://wwwrsphysse.anu.edu.au/~amh11..._off_valve.htm

Also the thing you see on the hard pipes is a BOV and its always located on the Hotside intercooler pipe (as to release pressure faster)

ninefiveone

On a 951, it's a diverter valve, not a BOV.

IMB951

lol, im still confused...

jsonnen

Yep you sure are..... Do a search and you will find all the answers you seek.

FSAEracer03

The BOV and DV act to release the build up of intake pressure when the throttle is closed and the spooling turbo is compressing air in there. This is to prevent breaking off the throttle plate and blowing it into the engine! The difference between the two is that the DV, like the stock unit on a 951, recirculates the pressurized air through the intake in a cycle to keep a quick spool up when the throttle is opened up again (i.e. after a shift). The BOV simply vents the air to the atmosphere, creating that WISHHHH sound you might hear on modified WRX's and such.

The wastegate is a pressure activated port in the exhaust before the turbo that opens up when the intake pressure reaches a certain point to prevent the turbo from overspooling and killing your engine.

As for the vacuum routing, that's basically impossible to describe in one post and w/o pics. I'd do a whole bunch of research before diving into tuning a turbocharged engine. Good luck with it all, however, and feel free to PM me if you want more info.

-KR

MM951

DV recirculates back into the intake and is best for MAF cars. Prevents the rich condition on shifts.

BOV vents to atmosphere, giving that PHHSSH noise (and my BOV is LOUD -- turbo xs RFL - rfl stands for "Real ****ing Loud" and I dont know if i will like it)

The wastegate limits boost. On most turbo cars its mounted on the turbo.

BOV/DVs are there to prevent the compressor from stalling, because when the throttle plate closes air rushes BACK to the turbo making go backwards for a second (at least tries to) and that can KILL the turbo. Also helps it spool faster between shifts with a DV/BOV.

superloaf

Yeah, I understand the difference between BOV, DV, and wastegate. The question I have is regarding BOV versus DV--wouldn't a DV be better since it recirculates while a BOV just vents the boost, losing all the pressure where you need it most: at the head? So are the WRX's whishing away good boost for a cool/annoying sound and therefor losing HP?

Fishey

no... because there is a limit to how much pressure you can effectively "recirculate" (spelling is bad when drunk)

IMB951

Thanks for the replies! It seems I have alot to learn! I plan on doing alotttttttttttttt of searching before diving into the first mod...but for now, its fixing the boosting problem, hence why I was inquisitive about what regulates it. My dad's turbo isn't boosting correctly at all, so I think we need to check all these valves first.

FSAEracer03

The actual boost "regulator" is the wastegate.

"The wastegate limits boost. On most turbo cars its mounted on the turbo.

BOV/DVs are there to prevent the compressor from stalling, because when the throttle plate closes air rushes BACK to the turbo making go backwards for a second (at least tries to) and that can KILL the turbo. Also helps it spool faster between shifts with a DV/BOV."

That's also a good point. Ian, our cars, however, have a separate wastegate. Instead of being internal, it's routed after the collector flange of the headers on the exhaust gases' way to the turbine housing.