should boost drop through revs

[paul-murphys]

hi everyone got a quick question should boost drop the higher the engine revs? mine peaks about 21 holds at 18-19 then drops down to 12-14 an tried this in 2nd 3rd an 4th gear. it holds at 18-19 till about 4000 rpm. ive checked for boost leaks but cant see nothing.i cant see how it would hold during some revs an drop at others? wouldnt be boosting less cause the higher tempertures would it??


thanks

 

[lordgibbness]

Smallish turbos can't usually sustain boost at high revs. You'll need a bigger turbo if thats a priority

 

[rikwheeler]

Running stage 2 revo and my peaks about 21 then holds all the way through the revs at 20.
Never had it drop at all until I change gear. Never tested it near the red line though

 

[DannyC87]

sounds pretty normal mate; the K04 is a bit weedy at the top end and can't sustain boost; a FMIC might help a bit by reducing intake temps; but otherwise it is big turbo time

 

[jwfcms]

its usual as the turbo is is using the pressure so it will drop, gauges are a bit missleading. get it checked out to make sure no faults, cheap for split hoses, who did your remap?
mine peaks up to 25 psi when i put my foot down in third doing around 30-40 mph it like loads up and then holds boost but when going through the gears, 1 st 2 nd 3rd it uses the boost faster and only peaks to 23aprox and goes quickly down to 21 and holds then 15 at the redline

 

[paul-murphys]

remap done by amd. on motorway i can put foot down an boost goes to about 18 an peaks at 19 then drops again. so its normal to lose boost on the k04 cause its a small turbo. is there no way of holding the boost for longer. will fit my fmic in week or so an see if makes any difference, its makin me feel like the cars slow :-(

does everyones boost drop on the normal k04? unless got a fmic?

jwfcms what rpm does your drop down?

 

[slim20vt]

dosent sound right to me mine peaks at 20 psi,drops of to 16 psi depending on weather road surface and weather traction control is on or off if its on, its normal for the car to drop boost levels between shifts,ie ecu controling traction its trying to get your max performance by tweaking brakes power traction so on.......................but sounds to me like you might have a small maf problem.if its only just started doing this then there is a fault looming.
generally boost leaks will zap boost on every gear change all the time might be worth plugging code reader to see if the ecu have logged anything.but would be intresting to switch mafs and see what it is like..hope this helps

 

[lordgibbness]

slim, if you check out any torque curve from a rolling road I'm almost certain you will see the torque reading is much lower at high revs (over 6000rpm).

 

[paul-murphys]

dosent sound right to me mine peaks at 20 psi,drops of to 16 psi depending on weather road surface and weather traction control is on or off if its on, its normal for the car to drop boost levels between shifts,ie ecu controling traction its trying to get your max performance by tweaking brakes power traction so on.......................but sounds to me like you might have a small maf problem.if its only just started doing this then there is a fault looming.
generally boost leaks will zap boost on every gear change all the time might be worth plugging code reader to see if the ecu have logged anything.but would be intresting to switch mafs and see what it is like..hope this helps

so what rpm does your boost drop off at? i will see if can get someone to do logs. i had traction control off. i got no lights on dash up??

 

[diggerbucket]

No idea what the boost figures would be, but my LCR with a Revo Stage 1 goes nuts at about 3k and drops off above 5.

 

[lordgibbness]

Yeah, the torque curve is a good representation of the boost level...

 

[paul-murphys]

had it rr other week an got told torque was low. i think was 270 but will at p torque said thats low. i cant see why my boosts dropping. would a fmic defo help? got one to fit just need to do it.

 

[jwfcms]

front mount keeps the intake temps lower, and frees up the airflow a bit. But if you have a problem you need to sort it before you put the cooler on really.

You could have a boost leak from a pipe or cooler so if you replace your cooler and some pipes and check the pipes that you leave on for splits, double check them as they can be hard to see. could be your divertor valve, have you got a 007p with a yellow spring? thats your first step. check the TIP to see if its collapsed and closing up the air intake or check for splits.

Get it diagnostic checked or vag com'd to see if there are any sensor faults coming up.

Log your airflow and see what you are getting. Close to 190 200 should be about right id think. any figures way below would indicate the MAF is on the way out, change it and you will see a instant increase in performance.

A faulty sensor or boost leak could cause this or the diverter valve, if you dont have a 007p already then would be a good idea to get one and if you do, get it serviced.

Boost will tail off to the end of the revs though so if its holding boost to high revs then droping off its probably normal, get it checked out by your remap place/ seat specialist and they could check it out and run some logs to see whats going on.....

 

[jwfcms]

and the torque does seem low.

 

[paul-murphys]

what should a stage 1 torque be? i have a 007 an works fine last time i checked it, i dont understand why have boost low down revs but higher up the revs it drops off. it happens in all gears. wouldnt a faulty maf bring up fault code an light on dash?

 

[ibizacupra]

hi everyone got a quick question should boost drop the higher the engine revs? mine peaks about 21 holds at 18-19 then drops down to 12-14 an tried this in 2nd 3rd an 4th gear. it holds at 18-19 till about 4000 rpm. ive checked for boost leaks but cant see nothing.i cant see how it would hold during some revs an drop at others? wouldnt be boosting less cause the higher tempertures would it??


thanks

you are describing the small turbo being out of puff at the higher revs..
higher revs consume more airflow, and the smaller turbo cannot maintain its pressure and flow at that level.. its max'd out

 

[paul-murphys]

so how come some people hold boost all way throught revs even though got same turbo. Its pushing 260. Thought there out off puff at 280.

 

[jamiebennett81]

so how come some people hold boost all way throught revs even though got same turbo. Its pushing 260. Thought there out off puff at 280.

what have you got to prove this?

your RR curve should be smooth till around 5500-6000rpm which is when I believe for a k04 is pretty much maxxed out

if there is a sudden drop or the graph is all over the place then there are leaks. If your graph is fine and smooth then no problem (theoretically)

couple of ways to check is to log the requested Vs actual boost and see if the two are meeting throughout the rev range and also log the air flow to ensure the MAF is operating correctly....as this can acount for a big drop in performance

get some logs done!

EDIT: What induction kit are you running?

 

[paul-murphys]

its a pipercross mesh kit. i got car rolling roaded at 2 places over 6 months an pulled 256 once an 259 another time, torque was 260-270 on both runs graph was smooth i thought, an thats what was told. i thought would be induction kit cause the hot air its drawing in as i have no cold air feeds apart from standard one to airbox?

 

[jamiebennett81]

its a pipercross mesh kit. i got car rolling roaded at 2 places over 6 months an pulled 256 once an 259 another time, torque was 260-270 on both runs graph was smooth i thought, an thats what was told. i thought would be induction kit cause the hot air its drawing in as i have no cold air feeds apart from standard one to airbox?

cold air feed is a must, but you need to see what the MAF is reading