Compressor Surge.

[sonofsam 5]

Anyone like to hazard a guess at why this has starting happening?

I know there is a small amount of adjustment on top of the DV, via a couple of nuts.

have fiddled, but it makes no difference.

It is a second hand el cheapo single piston one, so maybe it is bust, lol

 

 

Sam.

[Mikey S 29 1 Cars]

Anyone like to hazard a guess at why this has starting happening?

I know there is a small amount of adjustment on top of the DV, via a couple of nuts.

have fiddled, but it makes no difference.

It is a second hand el cheapo single piston one, so maybe it is bust, lol

Sam.

 

have you revved it up with your head under the bonnet? is it opening and closing ok? also check that the airfilter hasnt come loose as i had a 200sx where it had fell off and you could hear it down the inlet pipe.

Edited March 19, 2007 by pugger

[sonofsam 5]

Yes, and I can see the piston moving up and down.

Now you mention, yes I have been playing with the air filter pipes lately, that

could well explain it, cheers for the reply mate

[Mikey S 29 1 Cars]

no problemo!

[jim21070 2]

Surge What level of boost are you running then Sam? More than standard I assume if you are running into surge

 

Are you recirculating or dumping to atmosphere?

 

Have you a compressor map for the turbo? It would be most interesting to do a few calculations to see how near to the surge line you are under various conditions.

[sonofsam 5]

Surge in air going back into the blades and being heard as a kind of chopping noise,

what was commonly thought of as wastegate chatter, but thats in another thread altogether,lol

 

Atmo DV and Standard boost still Jim.

[Mikey S 29 1 Cars]

before i removed my xm turbo lump you could hear that surging back through the airbox. the majority of turbo cars do it, its just you cant here it cause the airbox muffles it right down.

[Henry Yorke 269 3 Cars]

Surge in air going back into the blades and being heard as a kind of chopping noise,

what was commonly thought of as wastegate chatter, but thats in another thread altogether,lol

 

So run that wastegate chatter one by me again Sam!!

 

Where abouts is the dumpvalve in the inlet tract? My chatter/surge came when the DV was disconnected. It went when connected. Is the DV pushing out hot air. Can you feel it blow hard?

[tom_m 0]

have you got a boost gauge on it Sam, is the dump valve actually releasing teh pressure when you lift off?

[pdd144c 0]

My chatter/surge came when the DV was disconnected. It went when connected.

 

It will do. When the DV is working the boost comes out of the valve, when it's not the it has to go somewhere when the throttle is shut so it forces its way back out of the turbo, hence the noise.

[jim21070 2]

before i removed my xm turbo lump you could hear that surging back through the airbox. the majority of turbo cars do it, its just you cant here it cause the airbox muffles it right down.

 

Indeed you do. If I really give mine some beans it is very easy to hear and for the very reason pdd144c says. I'm not overly sure if this is true surge or compressor stall.

 

Sam, I'm not too wise (yet) on DVs but I presume you're using manifold vacuum to open it. Are you taking the vacuum from the manifold side of the throttle butterfly? If taking it from the other side (Ported Vacuum) there often won't be enough to operate the DV reliably or quickly enough.

 

I'm considering fitting a DV to mine. I have to persuade my son to let me have a cast-off from his 200SX for an experiment or two.

Edited March 20, 2007 by jim21070

[inferno 1]

sam u need a diaphram type dump valve, like one from a fiesta turbo. they look like a mini ufo with loads of holes round them. sounds like u may have a twin piston, ull only see one piston without opening it up, and there beter suited to something like an MFI car, where fuels mechanicly metered and not done on a MAP senser.

 

i had the same on my zx, minimal ptshhh noise and a bit of fluttering. put a diaprham on and it worked great. nearly as loud as the zorst too lol.

[sonofsam 5]

have you got a boost gauge on it Sam, is the dump valve actually releasing teh pressure when you lift off?

 

Yes have boost gauge fitted, in place of the standard oil pressure gauge in the clocks

It's not releasing the pressure, and I can't feel any air coming out of the DV as a rev the throttle up and down... plus it doesnt make any woosh noise at all

Can defiantely hear the surge/stall coming through the filter also, and checked all the pipes leading onto the turbo and they are all sound and done up well.

 

Inferno I thought the diaprahm ones were prone to splitting, and I did buy this one as a single piston DV ( for cars with MAP), but as I said it was cheap and off evilbay,,..

 

Time for a new one then?

 

Jim, I have taken the vacuum fead to operate the the dump valve from the spare nipple on the side of manifold after the TB.

Edited March 20, 2007 by sonofsam

[bales 1]

Surge What level of boost are you running then Sam? More than standard I assume if you are running into surge

 

Are you recirculating or dumping to atmosphere?

 

Have you a compressor map for the turbo? It would be most interesting to do a few calculations to see how near to the surge line you are under various conditions.

 

 

Just as a bit of an aside and slightly off topic, compressor surge is another one of those terms that is used in the slightly wrong situation, which is what Jim is thinking of.

 

I think what most people think of compressor surge is when you back off without a dump valve and the air reverses when it hits the throttle and gets "chopped" up by the compressor hence the chattering noise.

 

But what it is I think Jim is reffering to is the surge line on a compressor map, and when you operate at above and to the left of it you are in a very unstable zone where the air flow can surge and do weird things and stall a turbo instantly and break blades and stuff.

 

I work a lot with big centrifugal slurry pumps at work so am always looking at these maps, and have seen the damage that running a pump outside its operating range can do.

 

As Jim says it would be interesitng to look at the compressor map for the standard turbo and see how far off the surge line you are at when running with a pr of 2 at low revs, bet it cant be that far off.

[sonofsam 5]

Interesting, cheers for that Bales. Plenty of compressor maps for T25's on da net

 

So is it safe to say im suffering compressor stall, as my car is very laggy at the moment

 

Thinking of going for a Forge single piston atmo valve, heard the diaphragm ones, a bit loud, lol

[bales 1]

Interesting, cheers for that Bales. Plenty of compressor maps for T25's on da net

 

So is it safe to say im suffering compressor stall, as my car is very laggy at the moment

 

Thinking of going for a Forge single piston atmo valve, heard the diaphragm ones, a bit loud, lol

 

Is yours still running standard boost Sam? I was going to run mine without a DV as it will be on standard boost for a while and it sounds good

 

Is yours noticably laggy as I always thought the fact that pug decided not to use it on some models must mean that it can't have a huge effect on lag especially as it runs such a small exhaust housing anyway.

 

If its the case that it is laggy i may have to may think about fitting a DV.

 

Also I guess that it probably is running a bit more than 7psi anyway even with the standard settings just because of all the flow restriction you have removed from both the inlet and exhaust systems and with a better IC.

 

I always wonder what power these engines run in a 205 as no-one on here (that I have read about) has been on a rolling road, they must be about 160 ish bhp easily if you have a full 2.5" exhaust and all the inlet is shorter and with less bends etc.... everyone quotes 150bhp but it must be more realistically - and the only 205 turbo I have been in felt a hell of a lot quicker than 150 ponies would suggest

 

Has anyone with a xu10cjte ever had an....ahem.....play with an mi16 205? bet it would be pretty close!

[sonofsam 5]

Yes, Im still running 0.5bar, want to get it all working spot on first before the chip goes in.

Realistically reckon you gain about 5hp with a decat, cant see it being much more TBH, but alas I have

no proof

 

Some 406T's came with a recirc DV, there was a post about that a while back

I personally couldnt give two hoots if it beat an Mi16, thats not what it's all about

But I do remember Fuqa or could of been V1ride saying it was very close, but I think

Increased torque makes it feel more quicker than it actually probably is!

Thats all that should be said on that topic, in this thread, thankyou please

[jim21070 2]

Bales, thanks for an excellent description of surge and compressor stall. It is very hard to find good, coherent and understandable definitions anywhere.

 

Yes I was thinking of the surge line you see on compressor maps. I'll go off and find some maps and run through a few calculations. It'll be valuable information given how improving breating can change the turbo operating paramaters.

 

As regards lag, I run it in a totally standard Xantia and lag is not very evident at all. In fact, you'd be hard pushed to know it is a turbo most of the time. I must agree though that it feels like more than 150BHP in the way it propels a very heavy old Xantia along. I think it is the good torque it produces that really makes the difference.

[pee vee 1]

Leave it chattering like All the rally cars do

 

used to Love it on my cossie !!

 

 

also, surge is something quite different to what you describe

 

If it Chatters when you are Accelerating and making peak boost... then you have 'surge'

[inferno 1]

surely a flat throttle shift map would eliminate the 'surge?!'

[jackherer 543]

I personally couldnt give two hoots if it beat an Mi16, thats not what it's all about

But I do remember Fuqa or could of been V1ride saying it was very close

 

I've driven a couple of standard Mis alongside Richs (Fuqas) turbo and they're pretty comparable so its mainly down to who gets traction first.

[bales 1]

surely a flat throttle shift map would eliminate the 'surge?!'

 

 

Yes if you are talking about the reversing of the air due to there being no DV, or No if you are reffering to compressor surge in relation to the pressure ratio and operating conditions of the compressor.

 

(If you set your ecu to do this without retarding the ignition just to cut it to individual cylinders like a rev limiter then it is called afterburn - a form of anti-lag)

Edited March 20, 2007 by bales

[sonofsam 5]

Thought I better update this, have removed the broken DV and blocked all necasary ports

and the lag has disapeared So maybe the DV was leaking from the manifold side?

who knows, but Im surely glad it's all working again now how it should, doubt I'll fit another DV

till the chip goes in, as the chopping noise is quite appealing at the moment

 

Thanks for everyones help, and look forward to seeing your calculations Jim

[jim21070 2]

Thought I better update this, have removed the broken DV and blocked all necasary ports

and the lag has disapeared

 

Excellent News Sam!

 

 

look forward to seeing your calculations Jim

 

I have one of those rare evenings that I can call all my own so I'm off shortly to pore over an Excel spreadsheet and look at some.

 

I may be gone some time

[inferno 1]

sam get a diaphram DV if you want another one. but i agree, chatter rules. why not fit an external wastgate and screemer pipe too?!