Suzuka_Joe

Absolutely. Unless you're dead set on running really low boost to get out of the hole or keep traction in low gears at WOT, I would run a spring size equal to your normal pump gas tune. I run 15psi on pump gas and recently changed from a 7psi to a 14.5 psi spring. Boost comes in somewhat faster and a lot harder. Hell, I turned my boost controller off because I don't need it on the street now.
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this might have been covered in here but why does it work again? I'm not doubting you. i'm about to go swap in my 11.6psi spring set i have. ( i have all springs ftw)

s2knoob89

Played around with this today and it really does makes a big difference. Boost comes on much harder.

GrandMasterKhan

This thread makes me happy. Can't wait to get mine setup.

siadam

With it spooling sooner, will this throw off your tune ? Cause it to lean out a bit?


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wadzii

If your maps are setup right there will be a table that compensates for boost, so the boost level should not have any effect on your afr

spectacle

There's a lot that goes into fully understanding this.

If your target is 14psi and you have 11psi springs in now, putting in the 14psi springs will improve boost response at that level, compared to a traditional, flat duty cycle boost controller. The reason for this is wastegate springs (with no controller) open up progressively. An 11psi spring set probably starts to crack open around 7-8psi, then open up the gate fully by 11psi. This behavior is the same when you move up to the 14psi spring, just from around 10-11psi when the gate starts to crack open. When you add a traditional, basic boost controller, it mimics the same behavior (cracking open before target) but applies pressure to the top of the gate to delay the spring from compressing, which allows you to run higher boost levels. The higher the spring pressure, the stiffer the spring. A stiffer spring is harder to crack open (obviously), so backpressure on the exhaust side will have a harder time pushing on the valve (opening it prematurely), which the boost controller has to fight against to keep you at the target boost level. Remember, the vacuum source on a wastegate at the side port comes from the intake side of the turbo. If your exhaust pressure is greater than your intake pressure, the exhaust pressure will push the gate open prematurely at the valve. Your exhaust wheel size, housing, and exhaust size in general will all have an effect on this. The more backpressure you have, the harder it will be to control boost.

With the advanced options in AEM and some other ECU's, you can tailor the boost response to come in harder or softer by dialing in how much and when the controller applies duty to the top of the gate, but its very tricky and you have to know what you're doing. The fastest response possible is to hold the gate shut until the last possible second, then openining it enough to maintain target. But, there's physics involved that dictate how fast this can happen mechanically, before you even get to the boost controller. Holding it shut too long will cause it to miss target and overboost...opening it too soon will not achieve the desired boost pressure. You have to take (through trial and error) the response time of the gate into consideration and figure out how much duty cycle will be be needed to maintain target at that specific moment. This method is best described as a controlled spike, and will surely get you sideways on the street in the lower gears (ask me how I know).

So in summary, the closer your wastegate spring is to your target boost level, the easier everything is. You can manipulate the response characteristics via a boost controller, but that can only take you so far with a smaller spring before backpressure acts against you. The best way to know if your wastegate (and system in general) is working correctly is to turn the boost controller off and datalog some pulls. If the boost comes up to target and stays flat through redline, dialing in the boost controller will be relatively easy. You might be surprised at what you find though.

siadam

So under the Adv Boost tab in the AEM v2, you just adjust the Boost Error Duty table, to reflect what is show in this thread, do you have to turn on the boost feedback under the options box?

It says boost switch input:switch is always off, then has a boost switch target, and a fuel cut load.

siadam

bumpy.

Suzuka_Joe

I'd like to know as well. s2knoob89 where you at?

s2knoob89

Only table your messing with is the Boost Error Duty table. Start with one of the tables that Wadzii gave us and go from there. If its setup too aggressive it will overshoot your boost target so make sure your boost cut is setup and turned on. I have found that it makes the boost control more sensitive to temperature change also.