xr2wishy

iTrader: (2)

hello, this time in a zetec turbo, decided not to compound someone else's thread any more.
basically i've gone from a chinese style t3/t4 to a gt3071r on a 0.63 housing.
it's in a forged zetec turbo setup with mild porting to the exhaust side, area six cams and springs.
since the change, when heading over a BAR i get surge, the only other thing i did was retard the inlet cam a little to combat an awful idle, i haven't touched the exhaust cam, although i do have adjustable pulleys to make life a little easier.

i have some pics of logs i've taken and all i've done in these is vary the gizzmo boost controller a little, these are my findings so far:

the first is on 90%gain 36%duty:


second run on 40% duty 80%gain


third is 45% duty 75% gain


(may have got settings slightly off, but you can see the changes.)

it's on MS so mapping is easily sorted, although the wideband is playing up a little, but is probably sensor on it's way out, just drops coms sometimes.

pani_k

iTrader: (1)

Without taking the topic off on a tangent, can I ask someone explain to me what surge is? I've always read about it on here but I don't know what it is and how you can tell.

xr2wishy

iTrader: (2)

basically the compressor is spinning so quick due to exhaust gas being high, causes the compressor to spin quicker than the engine can consume the air. so causes pulsing where boost builds, then drops and continues this trend till at equilibrium.
or that's how i understand it.

nixon_2wd

I think we both should try with a 0.82 ar exh housing mate

luke19790_3

did it do the same thing on clarke's engine?

GARETH T

It's due to a lack of flow to the turbine, so the turbine isn't producing enough torque to drive the compressor. Compressor slows down rapidly. And a cycle happens of spinning and slowing of the turbo shaft!

xr2wishy

iTrader: (2)

ok, that makes more sense, so i need to get more power out of the engine into the turbo, so look to timing and mapping to get more where i can.

xr2wishy

iTrader: (2)

not that i'm aware of, might not be getting exhaust open quite long enough to get the last bits of gas out. i dunno, cam swinging about to happen to test that theory though.

stevieturbo

Compressor surge is when the engine cannot consume all the air the compressor is generating and the air tries to go back out and you get a fluttering noise, much the same as when you shut the throttle and have no dump valve.

Not what anyone has described this far.

And when your injectors are well maxed out and mixtures very rich at 1.3 bar, why are you even trying to run 1.5 bar ?

And why are you running the gain so high ? That's probably what is wrong. Leave the gain at zero until you have got your boost levels correct.
The gain on most boost controllers blocks the signal until a certain level, so running it too high will see boost oscillation which is what you have. Not surge.

You do not control boost via the gain ! Gain is there to try and improve spool up.

Tune the thing properly !

GARETH T

wouldnt this just raise the inlet pressure (boost) ?

i think you'll find im correct as always LOL

stevieturbo

Compressor surge has nothing to do with the turbine. It may be affected by turbine choice, but the turbine is not making the noise or causing the noise.

And no it will not raise the inlet pressure. It will cause the engine to run badly but it will still run. Boost control will see that boost pressure does not rise, and most engines will simply drive through it, but it will not be doing the turbocharger any good.

GARETH T

you say it has nothing to do with the turbine, that say its effect by turbine choice, come on that just sounds stupid!

i really do understand what compressor surge is, its also happens on gas turbine engines, and these do no have an engine that cannot consume the air as in your statement!

GARETH T

ok lets talk about "same as when you shut the throttle and have no dump valve"

you close the throttle when the turbo is above its boost threshold,
there is a rapid reduction of torque being generated by the turbine.
the compressor desnt have the energy it needs to keep spinning, so its slows down rapidly, but there is still a volume or pressureised air in the intercooler/pipework, this tries forcing it way past the slowing compressor wheel

xr2wishy

iTrader: (2)

alright dudes, well i swung more advance on inlet and more retard on exhaust and been for some runs and seems much smoother.
i'm not convinced it has gone as such though.

i know gain effects how quickly the boost controller reacts hence why i lowered it.
the reason for raising duty is that i don't have an issue below a BAR, so need a little more to help it out.
the duty on the injectors is not a big concern right now, as the wideband is being an arse at the moment so afr's are incorrect but were fine previously (new sensor on order).
so could be running too rich, which will be sapping power possibly. however this has only really come to light today and wasn't an issue before.

there is no fluttering on the compressor as stated, so must be a torque/power issue in the exhaust side.


this is how it was when i went out last, waiting for new sensor now to be sure.

stevieturbo

Which has nothing to do with the turbine.. The compressor is the issue. And of course when at full load turbine size/choice has an effect, just the same as engine size, head, cams etc etc. We dont call it cylinder head surge, or camshaft surge or turbine surge.

And xr2. 90% gain is hardly reducing it. Your problem is purely down to bad boost control. Set the controller up properly. Run zero gain until boost levels are set via the valve duty.
Then and only then can you start increasing gain.

And unrelated, why is your battery voltage all over the place ?

nixon_2wd

The compressor is to large for the specified engine. What stevie says is correct. Compressor is not able to generate the small amount of air at the given (wanted) pressure ratio and is forced into surge (stall), hence being to large.

There is no problem with turbine torque, as when over the surge line the compressor is actually overspooling.

Think about right when you are closing throttle you get "turbo chatter". That is surge because the air which has been moved by the compressor dont get swallowed by the engine; this is damaging for your turbocharger as it causes bending moment on your turbocharger shaft and wear out your bearings.

Stu on here described surge pretty well only days ago.

GARETH T

do you think that if we calculated the airflow and pressure ratio onto the compressors compressormap that it would be over the surge line?

GARETH T

http://www.motorsport-developments.c...AF241.tech.pdf

stevieturbo

In this case there is no need. His problem is not setting up his boost control correctly leading to the boost oscillating.. From what he has stated, he does not have compressor surge.

xr2wishy

iTrader: (2)

Can I point out that this very turbo was on a 2.0 Zetec turbo with many similar aspects.

nixon_2wd

Boost fluctuations may be surge you know even if you dont hear it while driving.

GARETH T

Ok so what Is boost?

xr2wishy

iTrader: (2)

with adjusting the cams a little and reducing the gain it is far more stable.
however something seems amiss here, so investigating the wastegate itself, the fluctuation seems odd as does the ability to make any more boost than a BAR.

GARETH T

What's it doing now? How's about piping out the boost controller just for a trial?

Rick

Is this a T2 or T3 housing?

Nash

iTrader: (3)

The gain should never be set higher than the duty, having he gain higher will produce different results each time out.

As said before run 0gain and use the duty to get the desired boost level. Then adjust the gain afterwards to adjust how he boost comes in.

As a rule to run 20psi ish on an EVO the lads are running 40% duty and 10% gain on average. That was on the guide on how to set them up on MLR.

zetecbeast

only T3 on a GT30 I think fella

big_wig_074

Had this exact problem with a mates 200sx, as said reset boost controller to zero, then gradually increase duty to boost required then gradually increase gain so it doesn't surge

stevieturbo

The oscillation is 100% down to improper setting up of the boost control. It is not odd, it is expected the way you have configured it.

Draw a diagram of exactly how you have the boost control system plumbed.

xr2wishy

iTrader: (2)

well i believe there is a tear in the diaphragm in the external wastegate, i blew down the limiting pipe earlier and it didn't resist much, i set the EBC to zero and it's holding 1BAR just fine, no surge very strong power, the cam changes have actually made it pull better too, so worth a bit of effort in that respect, although a little laggier by 100rpm or so.

voltage is mega erratic though, but put some lag factor into ecu to help smooth it's operations out a little. there is an electrical gremlin that has plagued me for a long time, somewhere in the old loom is a problem, but that could be a goose chase and a half.

in the instructions for the gizzmo it said to start the duty low and set the gain as high as possible and in most circumstances this is the highest setting. or words to that effect, so that's what i did and not had issues with surge until this turbo was fitted (obvs a wastegate issue though in this case now).

big_wig_074

As high as possible before surging problems, not as far as you can twist the knob!

xr2wishy

iTrader: (2)

my point was that i never had issue before fitting this turbo, obviously more sensitive with a much bigger wheel and ball bearings to spin on.

nevsrevs

If you do a shearch mate grant baker as done a better version of a set up guide as this is so common on these gizzmo ebc.

stevieturbo

You do not have surge, you've already stated that.

And if there was a tear in the diaphragm you would be getting far too much boost, not too little.

And I suggest you read the instructions as to how to set it up. Because they do not say what you have stated about gain etc.

stevieturbo

Taken from the manual, it's quite clear.

xr2wishy

iTrader: (2)

well i stripped the wastegate, there is a leak, but not through the diaphragm, instead through the shaft connecting to the valve itself.
it is only minor though, still there is an issue, so back to basics with the ebc and make sure there are no other issues.
thanks stevieturbo, as always you know better than anyone else

with the ebc turned off completely it's actually holding boost better, more work to try out at another time.

stevieturbo

There is nothing unusual about a small leak past the shaft. Every wastegate Ive ever tested leaks there, more so the older they are.

Set the thing up properly and as the instructions tell you and it will work. Simple...at least it should be simple.

xr2wishy

iTrader: (2)

simple is how i need it, i just don't understand how it worked well without issue on previous turbos and this one goes on and problems occur, but must be more sensitive than the much lower performing and cheaper units.

GARETH T

So what's surge? Lol