Wastegate Spring Adjustment

**Rusty** · 29 March 2009, 15:38

OE should give 1.4 bar absolute (0.4bar gauge) when the N75 is unplugged. If the cap has been messed about with then the spring pre-load should be about 20mm from the top face to the top of the adjuster from memory.

**Andyh-R6S** · 29 March 2009, 15:57

Thanks Andy,

OK then. I now have a standard top cover fitted (Never been touched) and with the MTM P1 software, if you assume a standard spring if fitted, if I rotate the preload adjuster on the wastegate top cover though one complete revolution, would that equate to say '0.1 bar' (Abs) or more or less? What I am trying to get at is, is it better to fit a known new higher spring load to the unmolested top cover? And through others experience, what spring would be a good match for the MTM P1 software, etc. (I assume there will be trade off between getting the N75 going first rather than the wastegate? And am I correct in assuming that the wastegate should operate first and the last resort is the N75?)

Surely there will come a point where the spring preload has increased to a point where it would be simpler to fit a larger spring?

Regards,

Andy H.

**Rusty** · 29 March 2009, 16:09

If you're having problems then you really want to get it all back to stock. If it's a stock turbo then you should have no problems with a stock WG spring running 1.4bar abs. If it's still not running right then that would indicate that there are other problems that need to be addressed, if it's not a stock turbo then there's another factor that needs to be taken into account.

No idea what the rotation to pressure increase ratio is, you need to get a gauge on it.

**A80Avant** · 29 March 2009, 17:15

i tried various combinations with some wastegate springs i had made.I must say that there is improvement as to how boost is reached,but then again,wastegate spring stiffness is always combined with N75 valve duty cycle.

The only thing i havent managed to understand yet( must be the N75 duty cycle map i have) is how it is possible with a OEM spring that is so pressed to reach it's coil bind area(almost totally compressed) as revs rise on acceleration, im able to reach the boost profile that the N75 should have when connected, BUT when i replace the spring with a stiffer one and unwind the screw totally to have a stable constant mech.boost all throughout the rev range,i get to reach my exceeded boost cut off point when i connect the N75.

For example:

OEM spring: wound down, : mechanical boost: starts off at 0.4bar,climbs to 0.8, 1, 1.2 and goes up to 1.5bar as revs climb! ON this type of mech.boost,when i connect the N75----> i get the proper boost profile i should on my map.

OEM spring: on OEM setting: mechanical boost: o.4bar constant all throughout the rev range----> When N75 connected, i get the usual 0.2 to 0.3bar less than what the boost map describes.

Stiffer spring: 0.7bar mechanical boost all throughout the rev range. When N75 is connected the overboost shoots gradually more than 2bar and i get a boost cut off.

now why this is happening,im not sure... Perhaps the stiffer spring is making the overboost go more than 2 bar due to the specific duty cycle values at that point(hence it needs different map).

it is just very odd that i can run my OEM spring really wound down,and still be able to get the N75 operational,while when having a spring that gives only 0.7bar of mech.boost it cannot work with the N75....

**Andyh-R6S** · 29 March 2009, 17:34

Hmmm, where can I get a totally standard NEW (not second-hand) spring from in England that is not going to mean replacing all of the wastegate?
It might be the case that the spring in my wastegate is not standard (Totally unknown.) but I would like it to be, to match the virgin wastegate cover. Then I have a good starting point, as I have always assumed that the ‘MTM P1’ software needed a standard wastegate spring! (Although the RS2 manifold and big exhaust and the 200cpi cat’s I had fitted might have screwed the MTM parameters up slightly but I would have thought it would have not been a huge difference.)

I better flog something off and have a custom MRC remap done!!!

**Rusty** · 29 March 2009, 17:36

Measure the wire diameter and number of coils and then find someone who can confirm that is the correct OE spring.

**A80Avant** · 29 March 2009, 17:37

im not sure about the MTM P1 map of S2,but on the RS2 it definitelly uses only the OEM spring

i wanted to do the same thing with mine and bought one from ultimot.de. Not england,but the only one i could find with OEM spring spec to sell.

**Andyh-R6S** · 29 March 2009, 18:24

Yep, that’s what I will do.

I will have the spring that is fitted out and measure the uncompressed length and the number of coils next weekend and see if the there are any identification markings or paint on it, then post it at the end of this thread.

I do have another wastegate in my garage but that is where I got the virgin wastegate cover from to remove the Frankenstein version it previously had and although that has a spring installed I do not know really what spring is either, so I will measure up both. (Tagging the one in my car just in case I put the other one back in!)

But I am interested to know the length and coil data for a standard 97 Ur S6 wastegate spring if anybody has done this research before?

Regards,

Andy H.

**A80Avant** · 29 March 2009, 18:30

i can post a picture(i think i already have,if not ill try to find one) with the OEM spring i got from ultimot. It is very slim and soft.

**Andyh-R6S** · 29 March 2009, 18:45

That would be great.

Many thanks.

Andy H.

**newsh** · 29 March 2009, 22:01

Here you go, posted it for A80 Avant just the other week.

Stock Wastegate Spring

**s2_bo** · 29 March 2009, 22:56

Just out of interest, where is the best place to buy a stiffer spring?

Wastegate Spring Adjustment

Wastegate Spring Adjustment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment