Can an increase in WG spring induce surging?

[S2central.net]

You can't be hearing surge on a K24 are you ?

Agreed that MAF will reflect higher output voltage in cold air for the same volume passed over the sensor - it has temperature compensation and will result in higher air MASS as cold air is more dense. This higher load indication will have an effect on fuel & timing maps, but there is temperature compensation maps for that also.

On the turbo side of things... the MAF signal doesn't define the target boost level - its the throttle position... But if the temperature compensation maps are setup funny then it could be asking for higher boost in cold air...

Weird.

[GazzaG60]

it is normal to push more boost in a higher gear with a bigger turbo.

however usually a bigger turbo wont hit and drop off. itll hit and hold.

does the boost control map on motronic incorporate any speed sensor elements?

i would expect hit and hold or hit and increase but not to drop away in 3rd and not in 4th. if it was same in both then id say its how its mapped.

on a subaru i mapped with a apexi controller i saw 1.1bar in 1st, 1.6bar in 3rd, 1.95 in 6th. a huge t04r that the 2.35 engine.

on mine i dont see my full boost till 3rd really. but itll keep rising all the way if i ask it to.

if in doubt fit a boost controller i say. electronics with only one purpose in life. not a jack of all trades a master of one.

[S2central.net]

does the boost control map on motronic incorporate any speed sensor elements?

I'm not aware of such a thing... but it wouldn't entirely surprise me if I eventually found such a thing one day... None of the maps in the turbo chip announce themselves in what I'd call normal Bosch fashion - like in the motor chip - all this mysterious Motronic stuff its enough to drive you mad - or make you buy an aftermarket boost controller instead - LOL...

[GazzaG60]

the speed thing is the only idea i had. i couldn't see how this could be a mechanical issue.

i dont know anything about motronic paul. never spent the time to look into it and maybe dont have the skills or equipment.

the reason fo my theory is such

1. hold 3rd gear together under extreme boost, accel.
2. make the difference in acceleration less between 3rd and 4th to make a smoother more consistant drive.
3. third in general gets pushed harder than 4th and 5th due to the speeds attainable and full boost at 6-7k third is high injector and engine load. lots short-shift 4th 5th and 6th on the road

a theory but maybe big hairies.

[A80Avant]

i only managed to do a quick test this afternoon.
I changed the N75 valve to a new one,and retightened the hose that goes from the N75 to the wastegate.It seemed that the wastegate end was loose(dont know how that happened)

on a 3d pull the boost did climb to 1.7bar again,but now at least it didnt drop lower than 1.55bar at the redline with the wastagate spring fully unscrewed(so im not sure if that had actually been 0.4bar on mechanical boost but visually from the screw i can say that it wasnt far off.

I will try an do some more tests tomorrow as well and if i have time try to see if all other wastegate clips are ok...
difficult when you have to dismantle half the engine to reach certain areas...

i can visualise the VEMS coming....

[Rusty]

If it was leaking at the WG pipe then that'll not help matters

[A80Avant]

indeed! it wont!

but nevertheless,it is still far from the requested.... at least now i wont have to tighten the screw all the way down! hehe

[S2central.net]

If its building boost quickly from low revs and its holding onto 1.5bar at the redline then all it needs more boost in the mids is more WG duty cycle... Assuming everything else is mechanically good.

[A80Avant]

well,as you see i dont have too much time on my hands during the week and by the time i get back i dont have too much light either.But i will try to see if the other 2 hoses that go to the wastegate are secure and not loose.

Other than that,if that is what is needed then that can be arranged.However i will still test the motronic against a same car to see if the symptoms are similar there,as apposed to mine.

[A80Avant]

I did another test today(short one again)

the wastegate spring was holding 0.4bar up to 5500rpm then went to 0.5bar and finally to 0.6bar as i hit the rev limiter.

on these specs,i got 1.55bar on 3d gear on the redline and 1.6bar on 4th gear.

1.5turns on the wastegate spring later,i got 1.6bar on 3d gear and 1.7ish bar on 4th gear.

So im pretty much back to normal but with much less spring manipulation.I will have to take the headlamp off and retighten all the clips again,and hopefully the breather hoses will arrive before i leave on Saturday for me to install the catch tank....
At least that will keep the new N75 clean(as well as the MAF),until the VEMS arrives that is