FAST XFI BOOST Control finally some results!!

[turbobitt]

For best control, I would strongly recommend putting the sensor as far from the solenoids as you can and as close to the wastegate as you can get it. This is even more critical with an AMS system

Agree, Another task added to the list.
Allan G.

 

[norbs]

Allan, what's your opinion of using a 0-50 psi sensor instead of a 0-100 psi sensor would you get a better response to boost control?

 

[turbobitt]

Allan, what's your opinion of using a 0-50 psi sensor instead of a 0-100 psi sensor would you get a better response to boost control?

Hmm, Don't really know. If it changes the scaling values for the boost control settings then its hard to say. I don't know the control stratagy but I would ask myself if by increaseing the resolution by 2X, would it increase the response time since it may fool the controls by making smaller incremental changes ??

Allan G.

 

[turbobitt]

Changed the location of the Analog 8 sensor to get a cleaner signal and hopefully better boost control. Drilled another hole in the wastegate figuring that it will act as a big accumulator and dampen the solenoid pulses.

Allan G.

 

[kidglok]

thats exactly where the ams1000 recommends the sensor be placed

 

[norbs]

Looks good, I may have to mount my gate in the same location, I wonder how your 100hz wastegate psi logs will look now?

 

[norbs]

I also have another technical question, if we have a single gate that is too small 42 mm in my friends case, and we add another gate on the x over both with 7 psi springs, we are getting a max boost of 20 psi could we get more boost with 2 gates? As each gate will just have to crack open a bit to maintain boost? Also could we assume our boost duty cycle be cut in 1/2?

 

[turbobitt]

I also have another technical question, if we have a single gate that is too small 42 mm in my friends case, and we add another gate on the x over both with 7 psi springs, we are getting a max boost of 20 psi could we get more boost with 2 gates? As each gate will just have to crack open a bit to maintain boost? Also could we assume our boost duty cycle be cut in 1/2?

Look at it this way, If the backpressure is the same, it will tend to push the gates open the same amount regardless. I don't have any experience is dual gates but I would ask if it would be benificial to stage the opening of the gates with using different springs ?

Allan G.

 

[turbobitt]

Looks good, I may have to mount my gate in the same location, I wonder how your 100hz wastegate psi logs will look now?

When I was relocating the sensor, I was looking at the original mounting area where it was tee'd off the solenoid valve. I was telling myself what a stupid idea that was. Guess some things become more obvious afterwards !!!!!!

Below is a Dash log of the same WG pessure trace on the same run. Compared to the XFI log, this trace has drastically larger swings in pressure(about 10 PSI). As Norbs has eluded to, this is due to the faster logging rate of the Dash compared to XFI.

Just another benifit to data collection !!


Allan G.

 

[norbs]

I would like to see a new trace with the relcocated sensor......you need to go back to the track! Anyway I read this on the LS1 board about dual gates, do you agree with this theory?


Now, you need a minimum surface area of wastegate valve to flow enough gas to actually control the speed of the turbocharger. If you split that surface area between multiple gates, you can make each smaller so there is less pressure pushing on each spring per PSI of backpressure. You can then install lighter springs that will actuate with less boost (lower minimum boost) and stay shut to a higher backpressure (higher max boost).
__________________

 

[HighPSI]

Smaller gates tend to have smaller diaphragm's. So the backpressure vs boost control pressure ratio isn't much diferent when using a smaller gate. If you are fighting backpressure pushing the gate open with as 100 psi sensor/control pressure you are running the turbo way past its efficency range. If you don't want to use CO2 to control your gate, I may have an alternate solution. Several years ago, we used backpressure to the control solenoids on Phil McGloin's car with great success.

 

[TurboBob]

you mean use turbine pressure to feed the solenoids and wastegate balance pressure?

What a cool idea....

Bob

 

[norbs]

Smaller gates tend to have smaller diaphragm's. So the backpressure vs boost control pressure ratio isn't much diferent when using a smaller gate. If you are fighting backpressure pushing the gate open with as 100 psi sensor/control pressure you are running the turbo way past its efficency range. If you don't want to use CO2 to control your gate, I may have an alternate solution. Several years ago, we used backpressure to the control solenoids on Phil McGloin's car with great success.

Interesting idea, but what about the 1600 degree temperature of the air, did you use a cooler on the lines somehow?

 

[HighPSI]

Initially we were concerned about the temps, but it never became a problem. We ran a pretty long line to feed it just like when reading backpressure. Very little will actually reaches the gate and the amount passing through the solenoid is pretty minimal

 

[turbobitt]

Initially we were concerned about the temps, but it never became a problem. We ran a pretty long line to feed it just like when reading backpressure. Very little will actually reaches the gate and the amount passing through the solenoid is pretty minimal

What about corrosion and/or deposits ?
Allan G.

 

[norbs]

What about corrosion and/or deposits ?
Allan G.

Could we not use some kind of in-line filter?

Something like this?

http://www.ebay.com/itm/Nupro-Swage...ultDomain_0&hash=item3a763da9ec#ht_500wt_1415

 

[HighPSI]

You guys do what you want. I was just trying to offer some assistance to a problem I thought Norb's was having on some else's car. It looked like he was about to add expense and complicate things by adding another wastegate TO INCREASE BOOST?!?!?!?!.

Keep in mind, the exhaust isn't flowing to the wastegate. When the solenoid is closed, it is just compressing the air in the line going to the solenoid. Once the solenoid opens, the exhaust will climb up the line toward the solenoid and compress the air going to the wastgate. The only time exhaust is flowing through the solenoid is when the solenoid is dumping out of it's exhaust port. If you are using open loop boost control the added flow could damage the solenoid and may not work (haven't tried that yet). But, closed loop using Analog 8 should work just just fine.

 

[norbs]

I have some new data, we decided to run the boost with the lower line(constant manifold pressure unplugged) our minimum boost is now about 18 psi at and max about 28 psi with a 9 psi spring, without any co2. Here is the latest results. We are still having some very slight creep, but I can fix this with more I GAIN, I am hoping. Notice the duty cycle pulling down trying to compensate for the boost creep. I have a little post on PID settings to help you understand it better.

http://www.cpgnation.com/forum/general-p-i-d-info-boost-7262.html

 

[HighPSI]

I have some new data, we decided to run the boost with the lower line(constant manifold pressure unplugged) our minimum boost is now about 18 psi at and max about 28 psi with a 9 psi spring, without any co2.

So you are using backpressure without boost assist to open the gate.. Another option would to be to just run a stronger spring if you didn't want low boost control. A minimum boost of 18 psi is going to make for some mean launches! Have fun

 

[norbs]

So you are using backpressure without boost assist to open the gate.. Another option would to be to just run a stronger spring if you didn't want low boost control. A minimum boost of 18 psi is going to make for some mean launches! Have fun

Correct, but I've ordered a 4 port solenoid so this should allow us to tune between 9-27 ish psi on the same spring. We won't be able to launch at the higher boost, well maybe we will see.........I;ve posted a visual pic of whats going on I still see it creeping, going to add more I GAIN maybe another 5 numbers up.