Volkswagen Passat Forum banner

1 - 20 of 26 Posts

·
Registered
Joined
·
109 Posts
Discussion Starter #1
I was considering running the passat with no dump valve to see what the differences are, plus i'd like to get that wastegate chatter!

Would i be in danger of surge at the compressor / breaking blades when running 13psi on a K03?

I think the Bailey dump valve increases lag rather than reduce it !!!!
 

·
Registered
Joined
·
776 Posts
Short answer is yes - you will surge the compressor every time you flop the throttle closed (no flow = surge on a centrifugal compressor). I don't know about blade damage (I only have direct experience with damage on big turbos, like the ones with 30" impellars!). The diverter or blow off valve is designed to keep the compressor flowing above min or surge flow.

Others on here have had good luck with moving the diverter right next to the throttle body for improved throttle response. Try here: http://www.passatworld.com/forums/showthread.php?t=161837&highlight=relocation
 

·
Registered
Joined
·
2,335 Posts
If you're low on boost a DV might not be neccesary. On higher boost when you release the gaspedal while shifting the throttleplate will close trapping boost between the throttleplate and turbo-outlet. When trapped boost cannot escape it will stall the compressor and leave you with more lag than before. If the boost can escape through the DV (signal line is vacuum) the compressor will continue spinning thus minimizing lag.

It would help if not all boost is diverted but only the stalling boost.

You can damage the compressor side on high trapped boost, I would skip the idea. Some lag will always be part of your engine.
 

·
Registered
Joined
·
776 Posts
dutch-mountains said:
If you're low on boost a DV might not be neccesary. On higher boost when you release the gaspedal while shifting the throttleplate will close trapping boost between the throttleplate and turbo-outlet. When trapped boost cannot escape it will stall the compressor and leave you with more lag than before. If the boost can escape through the DV (signal line is vacuum) the compressor will continue spinning thus minimizing lag.

It would help if not all boost is diverted but only the stalling boost.

You can damage the compressor side on high trapped boost, I would skip the idea. Some lag will always be part of your engine.
You'll still get surge at low boost, it just isn't as destructive to the blades on the compressor (lower boost = lower energy during flow reversal = less stress on blades)

The ideal DV would only divert just enough flow back to the compressor to keep the flow above the surge region but that is a whole different ball game to try to manage.
 

·
Registered
Joined
·
109 Posts
Discussion Starter #6
modifiedA4 said:
im sorry, but this is a dumb idea. :crazy:
Why? Some cars do not run DV'S as standard?

A DV can sometimes cause more lag than no DV depending on the boost level you run! :crazy:
 

·
murdered out Jetta, er, B5 Passat
Joined
·
11,168 Posts
I have an old school Benz with a turbo on it and it doesn't have a DV. It has HUGE turbo lag! I hate driving it!
 

·
Registered
Joined
·
3,482 Posts
bostaph said:
Why? Some cars do not run DV'S as standard?

A DV can sometimes cause more lag than no DV depending on the boost level you run! :crazy:
a DV or a BPV is there to save your turbo from self distructing. :banghead: most, if not all turbo powered cars have in some form or another a way to relieve intake tract pressure when the throttle body abruptly shuts.

...and if turbo lag is really bothering you, need to learn how to drive a turbo powered car :rolleye:
 

·
Registered
Joined
·
776 Posts
modifiedA4 said:
a DV or a BPV is there to save your turbo from self distructing
And here is why - when you flop the throttle closed, the turbo flow drops as the pressure between the turbo and the throttle plate builds up. Eventually, the turbo blades can't add enough energy to continue to push air into the pipe between the turbo and the throttle plate and the flow reverses through the turbo. Eventually the pressure drops far enough that the turbo can push air forward again and the flow direction through the turbo changes back to normal. This cycle of back and forth flow will continue until something changes (i.e. you stomp on the throttle or all the compressor blades fall off the turbo so it can't build pressure).

The destruction is usually caused because the thrust bearings aren't designed for the thrust caused by the flow reversals and the turbo casing and compressor blades become your new thrust travel limit.
 

·
Registered
Joined
·
3,482 Posts
Petra Passat said:
The destruction is usually caused because the thrust bearings aren't designed for the thrust caused by the flow reversals and the turbo casing and compressor blades become your new thrust travel limit.
or the 180 deg cyclical shock to the turbine shaft, over time, at high temps, causes a fatigue failure in the shaft. *snap* there goes the shaft.
 

·
Registered
Joined
·
3,482 Posts
bostaph said:
Dont patronise me :thumbdown

I've had blown motors for years
i'm sorry. You asked for advice, which you got. Solid, correct advice warning of turbo failure. You discount this because "other cars run without DVs" in your quest to reduce lag.

The stock 1.8t is about as lag-free a turbocharged engine as you can get, so I assumed you didnt know how to drive a tubrocharged car.

Again, my advice is not to remove the DV, instead keep the revs up before shifting, double check your vac lines for leaks, make sure the DV is oriented the correct way, and if you still have lag, replace your aftermarket DV with a 710N.
 

·
Founder of the STFA
Joined
·
8,667 Posts
bostaph said:
Dont patronise me :thumbdown

I've had blown motors for years
You asked a question, you got some answers.

I say go for it. If it shortens the life of your turbo, report back and all of PW will have a definitive answer. Should be easy to eliminate, two 1" OD plugs and a bolt for the vac line. I've used black pipe fittings for the plugs.
 

·
Registered
Joined
·
109 Posts
Discussion Starter #14
ONE8T said:
You asked a question, you got some answers.

I say go for it. If it shortens the life of your turbo, report back and all of PW will have a definitive answer. Should be easy to eliminate, two 1" OD plugs and a bolt for the vac line. I've used black pipe fittings for the plugs.

Yes that is really appreciated, but comments like "you need to learn how to drive a turbo car" i find a bit patronising in the least when put in a certain context.

But thats not important, actually it must be noted that i am NOT on a quest for less lag, i only stated that the Bailey DV causes more lag than the standard recirculating valve for obvious reasons! I am one of the odd people who LIKE LAG, i kid you not! :crazy: :lol: :)
 

·
Registered
Joined
·
625 Posts
imagine what it is like to be in permanent lag(ie the 20v).in britain the car was available with a non turbo-1.6,1.8 or 2.0.all of which are slow as dogs.
i like the fact that you can cruise comfortably out of the fuel sucking turbo too.......
boostaf-you keep thinking mate!!!unfortunately,some folk have been thinking of ways to improve the 1.8t for many years.some on here push the envelope whilst others soak up other peoples findings and become so called internet mechanics.keep on pushing... :thumbup:
asking others opinions can be a great re-source,remember though,that nobody knows you,or your turbo driving history.so often members are totally clueless about how their car works,and 'learning how to drive a turbo' could,in that context,be a relevant answer.
sarcasm does't travel too well on the web........
stu.
 

·
PassatWorld Staff
Joined
·
12,267 Posts
This isn't the first time Mr. Bostaph has asked for advice here, gotten what he asked for, and then basically told everyone to kiss off. This attitude tires me. :thumbdown

If you're not going to respect the sound technical advice that's given here, then prepared to get flamed for it. A technical Internet forum is not the right place for thin-skinned know-it-alls.
 

·
Registered
Joined
·
109 Posts
Discussion Starter #17
Rusty said:
This isn't the first time Mr. Bostaph has asked for advice here, gotten what he asked for, and then basically told everyone to kiss off. This attitude tires me. :thumbdown

If you're not going to respect the sound technical advice that's given here, then prepared to get flamed for it. A technical Internet forum is not the right place for thin-skinned know-it-alls.
???? Wrong side of the bed?
Flame me then.
I'm not thin skinned or a know it all. I do respect the advice given, its much appreciated.
 

·
Registered
Joined
·
109 Posts
Discussion Starter #18
Rusty said:
This isn't the first time Mr. Bostaph has asked for advice here, gotten what he asked for, and then basically told everyone to kiss off. This attitude tires me. :thumbdown

If you're not going to respect the sound technical advice that's given here, then prepared to get flamed for it. A technical Internet forum is not the right place for thin-skinned know-it-alls.
Infact i think that as a moderator you should know better than to write stuff like above. You treat me with complete disrespect also with your remarks, are you going to flame yourself??
 

·
Registered
Joined
·
2,335 Posts
You can use an aftermarket DV with a stiffer spring to hold more boost, do not remove the DV or possible damage to your turbo might occur and more lag will be introduced.

If you want the above just try and plug both holes of the DV and post your results. I just would'nt put the stress on my turbo/engine though.
 

·
Founder of the STFA
Joined
·
8,667 Posts
bostaph said:
???? Wrong side of the bed?
Flame me then.
I'm not thin skinned or a know it all. I do respect the advice given, its much appreciated.

Infact i think that as a moderator you should know better than to write stuff like above. You treat me with complete disrespect also with your remarks, are you going to flame yourself??
Your original thread asked a question and suggested you expected an issue with the mod you were considering. The when people confirm that what you fear may happen, would happen, you argue with them.

Now go disconnect your DV and do some WOT 3rd gear runs. :lol:
 
1 - 20 of 26 Posts
Top