10 replies to this topic

[Carl0s]

So, a while ago noticed this: When you brisky acceleration, between ~2000 and ~3000rpm you can clearly feel when the "pull" goes on and off. After ~3k you get nice and steady pull. 

 

I encountered this first time whit the old engine, but didnt bother to give it any attention since i was changing the engine. But, now when it does it whit the new engine, il need to give it a closer eye. 

 

First thing that came in to my mind, is that egr is stuck. When i turn the car off, i can hear the EGR doing the self test loop for few secs. And, ive been driving around the EGR disconnected for the las ~2000km and it did not have any effect. 

 

If you accelerate gently, you wount notice anything out of ordinary, but if you accelerate briskly (like in overtaking) you can clearly feel it. Turbo should be fine, atleast i get steady 1.1bar boost during acceleration. :/

 

 

Any ideas ?

[alexp999]

Are you sure it is not just the mapping of the torque curve or do you mean it is almost juddering?

[Carl0s]

The power out put feels like SIN wave. You can feel it climbing up, then at the peak it starts to decline, and then climbing again. its pretty steady, takes like 1sec to do the "cycle" (from the power to the no power, and back to power). So its not like "snap" power off, "snap" power on, but smooth gaining power - loosing power - gaining power, and after 3k you get steady pull. 

 

If feels bit like when you have cracked boost pipe, it holds untill some point, when it starts to leak (the gaining power, and loosing power cycle) after the preasure drops, it starts to hold again, and regaining preasure. But, this sould be visible on the boost gauge? I get steady boost of 1.0 - 1.1 (tho, somethimes it bounces back and forth between 1.0 & 1.3). And, when i changed the engine, i checked the boost pipes (tho, just spinned them around in my hands and gave em quick view). 

[dreadz]

had same symptoms on my 1.6 tdci. about 4 weeks later the bearings went- loads of play in them!! £1100 lighter now pal- not meaning to scare you but get it checked. pull the pipe off turbo at front and see if you can waggle the insides of the turbo? also check under engine cover and look at injecectors-should be no carbon mess or anything at all

 

 

good luck

[dreadz]

i also initally thought it was split hose etc, but nothing was split/cracked. was scratching my head- untill i got turbo noise!! then i shat myself lol

[Carl0s]

The engine was changed 2 weeks ago. Did the injectors too. Turbo had some radial play, but no axial. 

 

 

EDIT: Hmm.. What kind of turbo noise? Since i can hear some "wshoooooooooooooooooh" sound during hard accelerations, that so far ive considered normal. (not much different what i heard on my mondeo, or what i can hear from my dads Kompressor MB...) :/ 

[dreadz]

sometimes odd squeal noise and had whooshing noises( i thought the wife was trying to describe the turbo whistle) hence why i though split boost pipe etc..then all of a sudden rattling noise in turbo area- then called AA

 

never had whoosing noises in the 1.5 yrs owned- and i have had all sort of turbo cars -so know what it should sound like when coming on boost

[FOCA]

Does this happen in all or some gears? is it worse in some gears than others?

 

Even though the boost appears to be "steady" the boost control systems (actuator, MAF, VNTmech etc  ) goes up and down -

 

eg - you floor the throttle, more diesel gets sqirted into the engine, the turbine spins up, the compressor spins up, makes boost, higher boost pressure travels along the boost pipes, untill it reaches MAF sensor

 

Once the desired boost level is acheived (read by the MAF sensor) the ECU instructs the VNT to reduce boost -

 

This drops the boost pressure level coming out of the compressor, it then travels through the boost pipes/ intercooler untill it reaches the MAF sensor

 

Now, the MAF reads under the desired boost level, and the ECU instructs VNT mech to increase the boost,

 

The whole cycle goes round again, normally you are unaware of the (boost control) system doing its job, and it appears smooth 

 

Sometimes, on a heavily modified car thats not set up right, you get this - its called "boost surge" "boost pumping" etc,  a lot of it is to do with the delay between the compressor and boost sensor (MAF) the "pumping" can be at a high or low frequency

 

 

is it an electronic actuator? is it off the old or new engine?  

[Carl0s]

Does this happen in all or some gears? is it worse in some gears than others?

 

Even though the boost appears to be "steady" the boost control systems (actuator, MAF, VNTmech etc  ) goes up and down -

 

eg - you floor the throttle, more diesel gets sqirted into the engine, the turbine spins up, the compressor spins up, makes boost, higher boost pressure travels along the boost pipes, untill it reaches MAF sensor

 

Once the desired boost level is acheived (read by the MAF sensor) the ECU instructs the VNT to reduce boost -

 

This drops the boost pressure level coming out of the compressor, it then travels through the boost pipes/ intercooler untill it reaches the MAF sensor

 

Now, the MAF reads under the desired boost level, and the ECU instructs VNT mech to increase the boost,

 

The whole cycle goes round again, normally you are unaware of the (boost control) system doing its job, and it appears smooth 

 

Sometimes, on a heavily modified car thats not set up right, you get this - its called "boost surge" "boost pumping" etc,  a lot of it is to do with the delay between the compressor and boost sensor (MAF) the "pumping" can be at a high or low frequency

 

 

is it an electronic actuator? is it off the old or new engine?  

 

BOOST PUMPING!! Exacly the term i was looking before i tried to explaing the whole sin-wave thingy

 

The new engine was whitout any accessory, so only block, internals, head and intake. Everything else came from the old engine, and its the 66kw version, that has fixed vane turbo and a wastegate. The actuator for the wastegate is vacuum functioning, but the vacuum comes the vacuum pump via electronic controller. (what is hidden under the HP-pump on the back side of the engine)

 

I think its most notable when you are drivin whit ~2k rpm on 3rd or 4th, and nearly floor it (~80% of max). 

 

The whoosing sound is similar what you hear, when you try to whistle whit dry lips, and you only hear the air movement (that was the closest thing that came to my mind)

 

I think i need to turn on the data-logging on my OBD adapter to get closer look of the boost preasure. Just incase the gauge it self has some lag and cant keep up whit the boost preasure change. 

[FOCA]

How does the new engine differ from the old one - would the new engine have come with a VNT? is it the same CC etc

 

Im thinking the new engine is supplying more energy into the turbine?

 

is the electronic controller for the vaccum on the pumatic actuator connected/ working right

 

it may be possible to run the pnumatic actuator directly from the turbo (without the electronic part) the pnumatic actuator may be set to work at a set boost  

 

Did you know with the fixed vane turbo you can fit a (seperate) adjustable electronic boost controller, so you could turn your boost up/ down as you drive?  

 

Do you want more power or just want it running well/ reliable?

[Carl0s]

How does the new engine differ from the old one - would the new engine have come with a VNT? is it the same CC etc

 

Im thinking the new engine is supplying more energy into the turbine?

 

is the electronic controller for the vaccum on the pumatic actuator connected/ working right

 

it may be possible to run the pnumatic actuator directly from the turbo (without the electronic part) the pnumatic actuator may be set to work at a set boost  

 

Did you know with the fixed vane turbo you can fit a (seperate) adjustable electronic boost controller, so you could turn your boost up/ down as you drive?  

 

Do you want more power or just want it running well/ reliable?

 

 

Its the same engine, 1.6 tdci 66kw version. Old one was -06 new one ~-09. All the numbers match... And ofc, the old one was 14 valve (valvetrain went haywire) and the new engine is 290 000km less driven. 

 

I could assume it works right. During engine braking boost drops to 0, during normal cruising its ~0,3 and when accelerating / driving up a hill its ~1. 

 

Im not looking any extra power atm, just curious whats causing it, and how to possibly fix it. It doesent bother me that much, since you dont notice it on everyday driving. but it still bothers a bit