newschool72

iTrader: (12)

Im about to start working to reaching my desired max boost and I am just wondering if there is any correlation between duty % and increased boost achieved , or is it completely different for every setup ?
I seem to have a lot of back pressure/inner cooler loses. Im starting with a 10 lbs spring, but only getting mid 6s at the intake manifold. Im using the Innovate SCG-1 boost controller and it has an over boost safety (as well as a lean fuel safety ), so Im not too concerned with overdoing the %, but I dont want to get crazy with it either.
As a general rule ( not holding anyone to their comments or advice ), what % of duty would you start at if you have 6.7 lbs of boost and want to get up to around 11-12 psi ? It kinda iffy doing road tests around here, so Id like to make a significant difference from the get go, so I dont have to tear up the streets around here several times to get dialed in and get the sheriff all wadded up !

MM98

iTrader: (13)

Is this the set up in your sig? If so, what size is the exhaust AR & what wastgate are you running?

newschool72

iTrader: (12)

Its the same engine and car , but Im running Fitech EFI and a GT45R CXracing Chinese special turbo now. The exhaust AR is 1.15 and Im running a Turbosmart HyperGate 45mm WG. Its an 80mm compressor with thee same trim as the Garret GT4508R (80mm/108mm) Thanks for the fast response.

MM98

iTrader: (13)

I wouldnt think you'd have back pressure issues with that turbo & low of boost. To answer your question, the % will vary from set up to set up & would try going in 10-15% bumps in high gear.

newschool72

iTrader: (12)

Ive looked at everything I can except a leak test on the hot side to try and find a pressure leak. I cant hear any leaks on the hot side. The cold side is air tight up to 15 psi. With the 10 lbs spring, it goes to 6 lbs almost instantly , then tapers off into the 5 psi range as rpms get up without any input from the controller. Well , the lines are hooked up to the WG, but Ive had the controller kick in pressure set at 12 psi, so it wouldnt get involve. Just to get the base pressure before getting into the WG duty tuning. I do have the waste gate dangerously close to the hot side merge and that might have been affecting the spring some , I guess. I fabbed up an aluminum heat shield that I have between the merge and the WG now, but it didnt seem to change anything. Its a head scratcher.

MM98

iTrader: (13)

Might check the spring that's in the gate & verify its actually a 10lb spring. Also, how do you have your wastegate & controller solenoid configured?

newschool72

iTrader: (12)

The spring started to open just under 9 lbs as best I could tell when I checked it. The controller is set up like TS says to for higher back pressure setups......top port on the waste gate goes through the solenoid, then to a tee that goes to the turbo compressor housing and to the lower WG port.

MM98

iTrader: (13)

Thats how I have mine set-up as well. With a 12lb spring in my gate, I will see right at 10lbs with the controller off. Ive read 2lbs of pressure loss is pretty common on the ebay coolers. Lets say your at 9lbs on gate pressure with a 2.3lb drop through the cooler, might be about right. But thats just my thinking & assuming youre running an ebay intercooler. Also you will see lower pressure with the reference line going to the turbo housing vs the intake.

newschool72

iTrader: (12)

I would have thought you would see higher pressure at the turbo since it hasnt been through the piping and IC at that point. What am I missing ?

MM98

iTrader: (13)

The wastgate sees the pressure from the turbo pre cooler & opens. So the gate opens at 10lbs & that pressure is being pushed through the cooler, some of which is lost before reaching the motor. If you reference from the intake, the gate wont open until the pressure in the manifold is met, 10lbs for example

newschool72

iTrader: (12)

Gotcha !! I will change that tomorrow and see what its boosting to before I start WG tuning. Thanks for the help

stevieturbo

It is the same answer every time. Given there are many variables, it is a case of trial and error.

The only one thing that should be universal, is your plumbing configuration should be such that low boost = 0% duty, highest boost = 100% duty.

Lsxford

iTrader: (6)

Theres is also backpressure pushing against the face of the valve. So if it started opening on a bench test at 9psi then with the engine running with back pressure on the valve face and the pressure drop through the cold side youd prob be around 5-6 psi

chejos13ls1

iTrader: (4)

So i'm having pretty much the problem as the OP, same boost controller/gauge combo. Im running a 8.8 spring and im only seeing about 5psi at the gauge. I also have the feed for the gate before the intercooler. Im going to switch to a port on the intake manifold too see what's up.

Sleeperls

What's your desired boost level? From what I've read once you get around that 80 90 percent, change the spring and get it back down.

Sleeperls

Also I'm weird I like to use turbo reference for the gate and them the map to see loss across the system etc.

No matter how good you are your gunna see some loss.

kingtal0n

iTrader: (1)

duty cycle is rated against time. So if the vacuum line is at 100% duty then its always open, always connected. Just like an injector at 100% is always open.

Duty cycle at 0% is completely closed. The injector is closed, the vacuum line is closed.

So when it says 50% DC that means the vacuum line (or injector, or whatever) is open 50% of the time.

chejos13ls1

iTrader: (4)

I see what your saying , but Innovate makes it looks like the opposite. They say to increase the duty cycle in increments of two until you reach your target boost. And then they say to adjust the gain for "quicker response at higher boos levels" that's where i got lost.

newschool72

iTrader: (12)

I get the part about the gain. Some turbo systems will show boost reduction at higher rpms, from back pressure against the valve I assume. Once you get your peak boost dialed in , you can add "help" to the controller with the gain feature to keep the boost from tailing off as back pressure increases at higher RPMs. All it does is increase the duty cycle as the RPMs go up.
When I posted the thread I was hoping for some insight to a good starting point on duty %, because I don't have any idea how much duty % it takes to increase my boost level by approx. 5 lbs, or probably more accurately by 75%. If I start at the recommended point by Innovate (4%) and increase it by 2% each run, I'm gonna need a rebuild before I get to my target boost if I need 40% duty or more !

dburt86

iTrader: (2)

typically, you will only get about 2 times ur sping pressure the way you have your controlled plumbed. 2- 2.5 times most likely.

That being said, they usually dont act that linear. Meaning if the most boost you could physically get out of a 10psi spring was 20psi, 50% DC doesnt necessarily mean 15psi

I typically start in open loop, and just start with 20% DC. Most times, it will barely raise the boost, but from there you can start adding 5-7% and see what it does.