Stiffer wastegate spring with a homefry?

[Animal Mother]

I've done a great deal of searching on this and had a few peoples comments but now I want a general consensus. I want to make it clear that I am not "second guessing" those that have already made comments to me about this, it's just that I have heard conflicting ideas on this subject.
Also, there is no definitive statement that I can find re. this subject.

So, should you/can you use a stiffer WG spring with a homefry or other modded ECU?
Whether it be a 1.7, 1.8 or 1.9 bar spring.

[terrybullwon]

Search wastegate bolt, or nut on wastegate also N75 or wgfv as this is important.

This is the same effect you just adjust the preload on the spring to force the gate to stay shut at higher values. You could remove it and test it off the car to see where it opens.

[Rusty]

Tried to adust this on my ABY but it's fully wound in so there's no more adjustment available.

[4WheelDrifter]

Homefry is designed for a stock spring, so leave alone or get a remap IMHO.

[HPmuirt]

Tried to adust this on my ABY but it's fully wound in so there's no more adjustment available.

So what is the difference in feel when driving (response to WOT as well as max boost seen) between fully wound in and stock (fully wound out?)

Cheers n

Si

[Rusty]

Si, as far as we could tell it was already fully wound in from the factory.

[S2central.net]

If you want to preload the WG with a stiffer spring then go ahead. It could do a few things for you:

1 - Reduce spool time and lag by the extra mechanical assistance on the WG

2 - Improve throttle response thru the gears

3 - Potentially raise a fault code if the spring is so stiff that the ECU has to exceed the adaptation limits on WGFV timing to achieve target boost. Honestly haven't tested that to have a clue how much is too much

4 - Higher mechanical boost reduces the safety margin in times of trouble... Lets say the ECU detects excessive knock (from rubbish petrol) and decides to turn off boost regulation (ie disable the WGFV) then you fall-back to max boost of spring pressure. This is 0.4 boost (1.4bar absolute) which is pretty safe. If you stick a 2bar spring in there then you could run to 1bar boost in that mode with crap fuel and have higher risk of doing some damage.

If in doubt, leave it alone, but by all means experiment with a stiffer stock spring or dabble with a stronger one if you wish to feel the difference. On a K24 turbo I wouldn't go any higher than 1.8bar spring due to the failsafe thing - 0.8bar boost on redline is about the limit for K24. Dunno if 1.8bar spring raises a fault code... Only one way to find out.


Paul

[Rusty]

Where do you get stiffer springs from?

[S2central.net]

From thy bay of all things commercially available

Or 034, Dahlback & others

[Animal Mother]

3 - Potentially raise a fault code if the spring is so stiff that the ECU has to exceed the adaptation limits on WGFV timing to achieve target boost. Honestly haven't tested that to have a clue how much is too much

4 - Higher mechanical boost reduces the safety margin in times of trouble... Lets say the ECU detects excessive knock (from rubbish petrol) and decides to turn off boost regulation (ie disable the WGFV) then you fall-back to max boost of spring pressure. This is 0.4 boost (1.4bar absolute) which is pretty safe. If you stick a 2bar spring in there then you could run to 1bar boost in that mode with crap fuel and have higher risk of doing some damage.

If in doubt, leave it alone, but by all means experiment with a stiffer stock spring or dabble with a stronger one if you wish to feel the difference. On a K24 turbo I wouldn't go any higher than 1.8bar spring due to the failsafe thing - 0.8bar boost on redline is about the limit for K24. Dunno if 1.8bar spring raises a fault code... Only one way to find out.

Paul,

So the homefried ECU should adapt to and be able to handle an uprated spring to an extent.

I suppose it could be fine tuned to a point to where it just misses the adaption limit, by using trial and error then?

I think it is worth a go. Will just have to stay on top of keeping the engine in good condition to avoid it going into safe mode.

Where do you get stiffer springs from?

HERE


I wonder if we can get a group buy going with him? I'd give it a go.

[Animal Mother]

Homefry is designed for a stock spring, so leave alone or get a remap IMHO.

Is it Paul? Maybe you can confirm this as I thought you changed the map sensor. Or is this a seperate matter?

[Rusty]

20 notes for a spring... that's fairly steep but then tuning stuff always is.

[merlin's S4]

In my experience the stiffer spring will also increase your max boost as Stu (4wheeldrifter) says. If you see 1.4bar of boost with the stock spring which is set at say 0.6bar, then increasing the spring preload to 0.9 will raise your max boost to above safe levels! Hence why you should have the car mapped to suit whichever spring you choose to use.

[Rusty]

It's only dangerous if the spring is set higher than the minimum boost of the map at WOT so for a Homefries that's about 0.8bar so a 1.8bar absolute spring is the most you want to go for. If you went for 2 bar then the boost would be higher at the top end and the ECU will throw a fault as it thinks the WGFV has stopped working proper like. Should mean that the boost comes in stronger than with the 1.4bar item but I suppose it's no as safe but then Audi did rahter like things to be safe and we spend time and money making them more fun...

[S2central.net]

Nope - ECU uses WGFV control to achieve the desired boost level for a given load point. Its not as simple as a stiffer spring giving extra boost... It reduces the WGFV regulation necessary to achieve the target.

The ECU will adapt the WGFV to suit the car and adjust automatically for age and stuff.

True that a big step change in WG spring could result in higher than desired boost as the WGFV adaptation has limited scope... and you'd get a fault code at that point. Thats why its necessary to get a custom map with a funky WG spring if you wish to get best out of it and stay within adaptation limits.

On the homefry its a trial and error thing right now as I've never had the occasion to try out different WG springs.

This has NOTHING to do with MAP sensors either.

Paul