White Knight II

s4 TII - stock turbo w/ ported wg, full RB exhaust, walbro 255, rtek 2.0, blitz BOV, autometer boost gauge

Hi there, I'm wondering if this thing is working right... first of all, I've got a vac line running from the UIM to the map sensor. The vac line for the BOV and the vac line for the boost gauge are both teed into that line. Also, the gauge doesn't seem to be calibrated; when the car's off, the needle is off to the left (~1-2mmHg). I'm wondering now if it's always off to the left (while idling, boosting, etc.) or does it give a correct reading as soon as it gets a signal?

Then, after the car is warmed up, it reads 20mmHg at idle. If I start driving and go really easy on the throttle, the gauge will start reading towards 10mmHg and I'll hear this click. I assume it's the BOV because I'll get a "pssshhh" if I let off. But I never made any boost? The gauge was still reading to the left of 0 when I let off. Is this possible? To hear the BOV when the gauge is showing vacuum? When I let off and the car is decelerating, the gauge reads somewhere around 25mmHg.

One more observation: while boosting, the needle starts at 0 and rises slowly to 7-8psi before I shift. It doesn't shoot up to 5 and slowly creep to 7-8 (I still have creep) like I would expect; it's very linear. Gauge not keeping up or could this be a wastegate issue?

Thanks in advance.

SpeedOfLife

iTrader: (16)

the stock BOV works on vacuum from the intake, so unless it's broken or hooked up wrong it will vent properly no matter what your gauge says. also, I think the stock gauge is basically pegged at 20* to the left, do you mean 250+mmHg?

*whatever units it's scaled for to read vacuum, I forget at the moment

What you mention later sounds like creep, and that will certainly be helped if you port your wastegate more or introduce more restriction into the exhaust. The first of which is more preferable, of course. Apparently the RB exhaust flows pretty well so this isn't too surprising. Search for Aaron Cake's writeup on porting your wastegate, the biggest aides are making a HUGE port and then welding a bigger flapper onto the arm instead of being limited by the tiny stock flapper lid.

Also, it's known that the stock boost gauges are often inaccurate. Mine is, too, when I read about 2 psi of boost I'm actually around 5, and it reads low through the whole range. It sounds like yours is doing about the same thing. The 0 mark is where the needle will rest when the ignition is on but the motor is off.

evileagle

iTrader: (1)

Autometer mech gauges are crap. Every one I have ever used is off.

Also, the BOV will open at less than 0 on the gauge. This is normal.

White Knight II

awesome, thank guys, that's what I needed to hear. I might try to pick up another gauge sometime; I just wanted to make sure it wasn't TOO much off. And thanks SpeedOfLife for the suggestions on how to stop boost creep. The wastegate is ported to the max and I'm running a completely stock intake and it STILL creeps.. oh well. I was just wondering why it's so linear and thought the gauge may be slow. But I think it may be a combination of the size of the ic piping and a disabled twin-scroll system or maybe my wastegate is stuck open? I dunno..

SpeedOfLife

iTrader: (16)

it looks linear because that's how the boost builds when creeping. what happens is you build full boost then the wastegate actuator sees boost still climbing (it's also vacuum actuated) and opens the wastegate all the way. trouble is, if you aren't flowing enough through the wastegate the intake pressure will slowly build, it usually won't just spike real fast like if you have a bad BOV (I think that's one way to get a fast boost spike...)

White Knight II

hmm.. I guess I'm still not getting it. I thought it should quickly boost to ~5psi while the wastegate is closed. Then, when it starts to see over 5psi, the wastegate opens to release the excess gas. But since it doesn't flow well enough, I should start seeing boost creep. In other words, it should quickly boost to 5 and then slowly start to creep. It basically looks like it's "creeping" from 0 to 7, 8, 9, whatever..

SpeedOfLife

iTrader: (16)

Oh I see what you mean. It climbs steadily from 0 to 8 with no notable change in rate around 5 psi. In case you don't know for sure you have a stock wastegate actuator you should check, it's possible it was replaced or maybe even the spring inside the stock unit was changed... The other more likely scenario is that, despite not being able to tell by how your car boosts, it's creeping and it just needs to be addressed. With an Rtek 2.0 though I thought you'd be fine boosting at 8psi, or does it climb higher or stumble around 8psi?

White Knight II

No stumbles and it only seems to go to ~8psi in 3rd gear before I hit redline.. I'm not sure what it would do in 4th though.. go higher most likely.

SpeedOfLife

iTrader: (16)

It's hard to say for sure since you don't have the stock fuel cut responses anymore. If your wastegate doesn't have a larger than stock flapper that's probably what you should do so you can port it out more. It certainly can't hurt anything and will tell you more about this issue once it's done.