wastegate actuator question (boost problem)

[Jay]

Hello,

For several years I had some problems with boost on my ibiza and i recently decided to try to solve them, but i need some help.

My specs are revo stage 2 with all the stuff needed (4b fpr, larger downpipe, ...) and a forge FMIC.

The most recurrent problem is a requested boost which is not matched at "high" rpm (after 5000), a relatively low maf values (don't really go a lot above 150 g/s), and bad RR results against others ibiza same day same roller (and sometimes with less modifications on some of the others cars).

I have visually checked for leak (found nothing), changed the MAF, tried with a known to work N75.

At the moment :

- the achieved boost is well above requested at mid-range (nearly 1.4bar when 1bar is requested)
- but under at high rev (max 0.7b when 0.8b is requested).

If i remember correctly my wastegate actuator rod screw has been messed up some years ago when testing for a solution, and is not in the default position (changed to add pre-load on the spring).
I think it can explain the really high difference between requested and achieved at mid-range, but if i put it on default position the difference at high rpm is really worst.


Today i decided to down the boost using my sps3, electrically unplug the N75 and take out the car for a ride to check what is the maximum boost (determined by the WG actuator spring setting if i'm right).

Here is a log of block 115 :

rev/min		Req Boost	Boost		Relative boost
		
rev/min	 	mbar	 	mbar		psi
2160		1600		1040		0,44
2320		1590		1170		2,32
2480		1580		1300		4,21
2680		1560		1350		4,93
2880		1530		1350		4,93
3040		1520		1340		4,79
3240		1520		1340		4,79
3400		1520		1340		4,79
3600		1520		1330		4,64
3800		1520		1320		4,50
3960		1510		1330		4,64
4160		1510		1320		4,50
4320		1500		1310		4,35
4520		1500		1300		4,21
4680		1480		1290		4,06
4880		1470		1280		3,92
5040		1450		1280		3,92
5200		1440		1280		3,92
5360		1430		1280		3,92
5520		1420		1270		3,77
5680		1400		1260		3,63
5840		1380		1240		3,34
6000		1360		1240		3,34
6120		1340		1240		3,34
6280		1330		1230		3,19
6400		1300		1220		3,05
6520		1290		1220		3,05

First question is : what is the default pressure at which the actuator spring is set ? I though it was 4 psi ?

Second question is : am i right in thinking the boost should be quite constant above the entire rev range, and that i may have a weak spring in my actuator ?

And the final one :

if it's not the actuator what can it be

Thanks for your help !!

PS: sorry for the bad english writing.

 

[ibizacupra]

5-6psi is normal static pressure of actuator

the turbo often will not make requested boost at top end. It is not a fault just the limitation of the hardware. Other things which can contribute to the spike are the type of N75 used... 'J' valves or ECS Race valves do the same thing

150g/s is'nt great and if it is the same on a known new working MAF, is related to the turbo's ability to flow air... (it could be worn out) - Have you tried a known new working maf to compare readings?

 

[Jay]

5-6psi is normal static pressure of actuator

the turbo often will not make requested boost at top end. It is not a fault just the limitation of the hardware. Other things which can contribute to the spike are the type of N75 used... 'J' valves or ECS Race valves do the same thing

I'm using the standard N75.

The fact is i'm quite sure the wastegate actuator rod screw is not on default position and is set to add load, i have to check but without that the max pressure attainable after 5400 was hardly 0.6-0.7b bar which at that time seemed low to me.
I remember that after having played with the rod there was a boost spike, i think the current one comes from here.

does anyone know where the screw should be on the rod ? or have a photo ?

I know the k03 is not good at keeping pressure at "high" rpm, but after having stage 2 and all stuff my boost has always been lower than others ibiza i checked (which was able to have 0.8b where i had 0.6-0.7). I even think a standard cupra R was able to have better boost than mine.

150g/s is'nt great and if it is the same on a known new working MAF, is related to the turbo's ability to flow air... (it could be worn out) - Have you tried a known new working maf to compare readings?

At this time i don't know anymore someone from which i could lend a working maf, but i will try to find one.

I have another question : may a leak somewhere around the exhaust manifold explain the turbo is not flowing as much as it could/should ?

I had a k03s in a box for 2 years now, but never put it on car as i need to find someone (don't have capabilities nor access to a car hoist) and i was afraid of doing more harm than good mounting it before having solved my problem (in fact i have k03s, exhaust manifold, tip , forge wg actuator).

Think it's time to

 

[-=Rob=-]

150g/s is'nt great and if it is the same on a known new working MAF, is related to the turbo's ability to flow air... (it could be worn out) - Have you tried a known new working maf to compare readings?

Hmmm, I'm also getting 150gm/s on my K03 too, I thought that was around right for K03? Perhaps this depends on the induction method mind you? What are you running? For comparison I'm running a smoothed airbox, green panel and large cold air intake.

Also, what are your boost / timing setttings?

 

[Jay]

i'm using a green dynatwist kit, but at this moment taking air from the engine bay not from the front (doesn't change so much).

i think i can it 150g/s from lb6 or maybe lb7 but after it doesn't really go up alot.

concerning timing i'm currently using 6 but i can go as up as 9 without CF going over 3


i forgot another question concerning the actuator, i've read the standard position is when you can see 12-14 threads from the end : i would just like to be sure i have understood what people mean by the "end" :

is it the side which is connected to nothing ?