No Boost at all....need help

[andyg plym]

it shouldn't be.

cut down a paintbrush and use it to cvlean the maf wires. use some carb cleaner or similar.

a turbo is mechanical so it should boost regardless as long as you are getting gases to it. this does sound mechanical to me.

i am making the presumption that the car doesn't cough, splitter, miss or coug out black smoke. what does an af gauge tell you. do you see plenty of fluctuation of tracking stoich. then when going to the map do you see it hit rich minus 1 light or so?

issues with lambda usually result in missing around the time when the transition to map occur or about 2 minutes after startup. initial start is not lambda controlled usually as the probe needs to warm up in order for it to find stoich. its usually downhill from there
if it runs smooth and revs ok it should boost. if it feels normal id still be saying turbo and getting gas to it. id expect cam timing being off would rear its head as lumpy running or something.

it barely idles at all,cold or warm, constantly drivin wiv foot on accelerator even under brakin,no smoke at all. you can hear it suckin in air just before dv wooshes.

[andyg plym]

I still reckon its a boost leak, or a non spinning turbo, lack of oil to the turbo perhaps?

put newer turbo on and now just boosts to 0.3 bar but it struggles badly. new oil in and tubo now in uprite position

[Acidburn]

when you say barely idles is it definately on all 5 cylinders (i.e. not sounding like a scooby)

all the plugs tight, boots not damaged etc

[andyg plym]

when you say barely idles is it definately on all 5 cylinders (i.e. not sounding like a scooby)

all the plugs tight, boots not damaged etc

yes all sweet wen you hold it at 1200rpm, sounds fine, never misses. could a dirty maf caked in oil and in a wrong location cause above problems?

[Knight Rider S4]

A quick way to work out if it is mechanical or electrical fault is take the yellow and green wire off the N75 valve and earth it ..by doing this you bypass the ecu and go mechanical boost via the wastegate ...If it doesnt boost you know you are looking at a mechanical /pipe/intercooler problem and if it does it is something electrical i.e sensor..

[andyg plym]

A quick way to work out if it is mechanical or electrical fault is take the yellow and green wire off the N75 valve and earth it ..by doing this you bypass the ecu and go mechanical boost via the wastegate ...If it doesnt boost you know you are looking at a mechanical /pipe/intercooler problem and if it does it is something electrical i.e sensor..

i ran wivout n75 connected and didnt get mechanical wastegate boost ie 0.4

[Knight Rider S4]

You need to earth the green and yellow wire for it to work with the N75 still connected..try it and see...I thought i had a issue with my 3B as it was only boosting to .8 bar (standard) was told it had been mapped which it hadnt so i did this to see if there was something up with the turbo ..went to 23psi after doing it ..so it told me that the chips in the ecu were crap or still standard

[bigdan]

If mechanical boost is 0.4 bar... and your boost gauge reads less than this, then either you are loosing boosted air, or the turbo is not compressing enough air in the first place?
However, IF the turbo was compressing enough air then surely you should get at least 0.5 bar? according to your pressure test?

we manaed to do a pressure test and couldnt find any obvious air leaks although we only went upto 0.5 bar (boost guage registered 0.5)

So, this leads me to wonder whether the turbo is getting sufficient exhaust gas to compress the air. you say timing is correct, and wastegate works freely so i assume that it is not stuck open. the turbo is known working....

got a larger zorst manifold on (in prep for rs2 turbo)

cant help but wonder whether the exhaust manifold gasket is fitted correctly or is it the correct gasket?, i.e not obstructing exhaust ports and thus stopping sufficient exhaust gas passing the turbo and also causing excess back pressure on the engine hence the idling trouble?

Might be of no help at all, but something different to think about?

My way of thinking is that, never mind your maf's and n75's, in a healthy mechanical system, when the engine exhausts, a healthy turbo must spin and thus compress air, and as long as this air is not lost it will build up to 0.4 bar before the wastegate spring is overcome and turbo speed is regulated.

maybe its past my bedtime....
Dan

[GT500]

Try your fuel pressure. do a test.
Just my first thought...

[andyg plym]

If mechanical boost is 0.4 bar... and your boost gauge reads less than this, then either you are loosing boosted air, or the turbo is not compressing enough air in the first place?
However, IF the turbo was compressing enough air then surely you should get at least 0.5 bar? according to your pressure test?

So, this leads me to wonder whether the turbo is getting sufficient exhaust gas to compress the air. you say timing is correct, and wastegate works freely so i assume that it is not stuck open. the turbo is known working....

cant help but wonder whether the exhaust manifold gasket is fitted correctly or is it the correct gasket?, i.e not obstructing exhaust ports and thus stopping sufficient exhaust gas passing the turbo and also causing excess back pressure on the engine hence the idling trouble?

Might be of no help at all, but something different to think about?

My way of thinking is that, never mind your maf's and n75's, in a healthy mechanical system, when the engine exhausts, a healthy turbo must spin and thus compress air, and as long as this air is not lost it will build up to 0.4 bar before the wastegate spring is overcome and turbo speed is regulated.

maybe its past my bedtime....
Dan

dan, i wonder if a k24 is upto a tubular manifold? i reckon its an ebay special manifold,like you say maybe a block in it?

[newsh]

I'd say Dan is spot on here. It seems mechanical.
Another thought, increase in flow can affect the amount of pressure given by the turbo. When the bigger valves and porting were done to the Treser urs they had to fit a much stronger wastegate spring to acheive the same boost. Maybe the manifold you have there is not ideal for the K24 or is routing too much pressure through the WG. How about fitting a stronger spring or winding the spring down to see if boost increases?

[andyg plym]

could be summat to try, rs2 turbo was on before and apparantly was fine

[bigdan]

I think you could be right there. Maybe the tubular manifold, being of longer tract does not deliver enough exhaust gas pressure to spin up the turbine of the k24 turbo, therefore the newer turbo who's bearings are in better condition will spin up easier, and this is why you have noticed a slight gain in boost pressure? Or, as you say maybe its a dodgy ebay special!!?

Either way, if it was me, my next port of call would be to take the new manifold off and inspect it and refit the stock manifold (if you've still got it) and see if the fault persists. What have you got to loose!

hope this gets sorted for you soon!

Dan

[GazzaG60]

it should idel ok though.

even if you disconnect the pipe from turbo to IC or at the throttle bodie it should idle ok and hold. the engine is sucking after all at this stage.

i have had similar. im not 100% what it was but it was one of these

1. bad sensor pickup from the VR. thats intermitent though if it does.
2. seal around the plastic scuttle panel gone. this means water leaks into near the fusebox. water in ambda wires for same reason. wd the full area. not on probe or in any engine bits though WD kills probes.

when it did the lumpy thing id have to fight to keep it running. i believe it was affecting v in the probe.

id still expect boost from the tubular to k24. nowhere near a good balance but you gotta start somewhere.


im thinking was therer any other potentials. ill try to remember.

basically the car would run on all five but would be lumpy all the way. it wouldn't rev either. no boost due to bad running. i could set off from home and 2 minutes later it would start to stumble. this is on the vems too. i had just had my tubualar rewelded and so some wires had been moved. some were in the rain tray including my 2nd wb02 sensor plug.

[AUDIS2avant]

The new EM will NOT effect this, only more lag nothing else.
So i would be looking for maybe stuck idle control, if constantly open more air will come in back the throttle lid and effect the idle AND normal driving, but not full throttle tho.
And check wiring to tps lambda and MAF too as this is the sensors normaly that controls the idle and driving mixture.
Have you checked the plugs?