UrS4boy

On Sat. Mar. 11th, our Vancouver S-car club had a dyno day at Rocket Rally Racing in Squamish BC. Since I organized it, I was the first car on the dyno. I was running the 1.9 bar WG spring (for about 3 weeks) and had turned it out quite a bit (1.5 threads showing). However, my dyno runs were not that good. The boost kept spiking at close to 30 psi (relative). The ECU kept trying to adjust but in the end, it really could not do it properly. End result 269 whp (1.25 factor = 336 chp). See the graph below.


While some of the other cars were running, I decided to swap back to the stock WG spring and re-run. The improvement was dramatic: 289 whp (360 chp) - which is about right. See the second graph.


Now I really like the feel of the 1.9 bar spring on normal driving. The suggestion was I should install a manual boost controller to limit the boost to 26 psi with the 1.9 bar spring.

Feel free to discuss.

escargot

And now with this evidence I'm happy I'm not running it.

spiralsmurf

i bet the boost solenoid just can't keep up anymore. Given that we all have old springs, most of us probably have old N75s. Autospeed an electronic boost control kit that works with any boost solenoid out there.

spiralsmurf

i like it, i build boost much faster and it requires less throttle

Only-Emre

I never get an overboost condition with my spring, perhaps there is something else off there.

VR_Life

with WG spring. Maybe it's the rate of change ?

Here's my zip-tied MBC-in-parallel kludge.

<img src="http://pictureposter.audiworld.com/58573/img_3008.jpg">

<img src="http://pictureposter.audiworld.com/58573/img_3011_medium.jpg">

cpayne

I mean...I would suspect the car under WOT at say 2000 RPM is requesting FULL boost up to say 5800 RPM or so where it would start to crack the Wastegate to reduce boost. Now if the car is NOT requesting full boost at low RPM's then it makes sense...otherwise I dont get it.

Up top I understand how it holds the boost longer and higher..especially if the stock spring is being overwhelmed by back pressure and causing the WG to open prematurely. Also if the ECU is requesting for it to back off boost and it cant because the Spring is holding the WG shut...the boost will hold longer. Cant say if that is good or not...really the concern would be if the car is going lean...as it doesnt expect this sort of boost at X RPM.

Sloooo4esT

mines been sitting on the table for a month, not gonna touch it without a boost guage

urS4guy

Its that phenomena known as WG Creep. Yes, it is from a horror show. Let's say you've got an RS2 turbo equipped car that is at full on boost about 3200 rpm. As this car approaches 3200 rpm the ECU starts signalling the WGFV to start opening the WG so that you don't have a spike in boost. When that signal is sent and how aggressive the signal might be is what causes the WG Creep or premature opening of the WG. This provides a nice taper to the boost curve without a spike.

Different SW parameters with things like boost, fuel and timing all have an influence with or without the spring on how much or little creep will be involved. That's why different SW bundles and turbo combinations react differently.

During my RS2 manifold days, I ran 2 WG springs, a 2.0 bar and another tucked inside the first and an Apexi fully programable boost controller with pressure lines to the top and bottom of the stock WG. Along with all the flow work on the intake, charge air and exhaust with the Garrett 57 trim, I was able to get that badboy to full boost at about 3400rpm. There is no way I could have achieved that without the double springs and the boost controller. When Pete Tsai was working with me to teach the Apexi AVC-R and set-up the boost corves he asked me when I wanted to achieve full boost. I kind of laughed and said, "Pete, ask it for full boost at 2000 rpm. There's no way it can deliver given the size of my turbo and the inadequacies of my EM/DP." He set it up that way and I was able to get that full boost at 3400 rpm.

Jason C

same here, I've have one in a box for years