Turbo motor continues to build Boost wile Lifting

[whittlebeast]

The Dump valve BOV worked nearly flawless. The on/off trigger has the following settings.

tpsfuelcut >3
AND
MAP > 105

Right now I have no Hysteresis. I wanted to trigger off TPSdot < -100 but right now the 1.2.1 code does not want to take negative number.

The 3 lb BOV spring should be here later this week. The 10 lb spring that is in there right now is limited at to what I can achieve with TPS based boost tuning. I will be doing more testing when it gets here.

With the BOV trick only, I am dropping from full boost to 100 KPA in .25 - .30 sec after the DE triggers.

A log is posted at http://www.nbs-stl.com/miata

Ignore the AFR and GEGO as the wideband failed wile is was driving. I am using the new CEL feature now to catch that issue. At around 150 sec, I was pumping the throttles to try to fool the system.

Andy

[whittlebeast]

I updated the some of the sketches in this thread.

Check out in the first trace how far the driver had to get out of the throttle to get the motor to stop accelerating hard.

http://www.nbs-stl.com/miata/AccelWhenLifting.png

Compare that trace to this one. Both traces are at about the same zoom.

http://www.nbs-stl.com/miata/WithBOVControl.PNG

It is very comforting hearing the BOV going POOOOFFFffff when you back out of the throttle and instantly the violence quits.

Have fun tuning

Andy

PS, we should have the new motor fired up in the next few weeks.

[muythaibxr]

Andy, I think alot of what you show in that log screenshot is also because of the way you were running boost ctl back then. With a boost controller that reduces its boost target as you lift off the throttle, you should be able to control the behavior there better.

[whittlebeast]

Ken

Once I went to this BOV logic, the driveability of the car was transformed. This is the only way I have ever seen to get the boost well below the spring when the turbo is spooled up. As I recall, the spring in this car is real close to 150 kpa. This motor is ITB so we have to get back to about 15% throttle to get the boost to stop building. We need to get back to about 100 KPA to get the tires to catch when you have them hazed on course.

Bottom line is I have to get from 190 kpa down to near 100 kpa and back to about 190 kpa in about 3/4 sec or you will never catch the car in time. We need to do this with about 1/3 of the throttle travel or you foot will never keep up. For the drag racers, we ran into the same sort of things controlling wheelies.

I have every intent to go to your new boost control logic this season as soon as we sort out all of the typical new motor tuning issues.

Andy

[muythaibxr]

Right, nothing I said precludes any of what you're saying. You should keep the BOV on there as well. But the benefit here is that PID will respond to changes in target as well and get the boost solenoid to the correct duty to hold the boost you're trying to hold at any throttle position.

Ken

[Peter Florance]

Right, nothing I said precludes any of what you're saying. You should keep the BOV on there as well. But the benefit here is that PID will respond to changes in target as well and get the boost solenoid to the correct duty to hold the boost you're trying to hold at any throttle position.

Ken

Although I have not tried this new method, it sure sounds better.
I'd try it, Andy.

[weeblebiker]

I may be bumping a dead thread, but tuning turbo itb is way easier with hooking the map pressure sensor to the plenum pre itb.

That said I am researching blow off valve issues myself, seems I am not creating enough vacuum differential post itb to have good blow off valve control. I get a occasional loud pfffft sound at idle and and quite often at part throttle highway cruise where the pressure differential is 5psi ish. I have read my volvo TD04H-14T turbo has a stock 8lb spring in the bov (called a compressor bypass valve or CBV). I'm considering building a solenoid valve.

[cukali]

The throttle is about 1 to 1. There is no rising rate bell crank involved.

15% could be 40% power or more on some setups. Especially if the ITB's are really big.

Exactly.

I went to a large TB on a turbo setup and had the exact same issue....switched back .

[piledriver]

"WOT" is a rpm dependant construct, ms3 at least has a WOT table for setting up accels.
Even on what is basically a na vw bus motor, at 2k, ~20% throttle provides ~100 kpa.

You almost need a smaller set of plumbing for low/mid power and have the itbs open up under ecu control only near full demand.
(the Subaru or vw "tumble plate" butterflies near the valves also come to mind)

Implementing traction control as well might be a good idea if you are having that much trouble keeping the tires under you.
You will be much quicker around a course if you are not sliding all over the place and not just desperately trying not to stuff it.

Stupid power on tap is surely fun, but not necessarily the fastest way around the cones.

[whittlebeast]

We have since sold off the rotary motor and we are installing an LS1. That should change the torque curves.

Andy

[weeblebiker]

The throttle is about 1 to 1. There is no rising rate bell crank involved.

15% could be 40% power or more on some setups. Especially if the ITB's are really big.

Exactly.

I went to a large TB on a turbo setup and had the exact same issue....switched back .

I modified the stock vw 16v throttle pull and attached it to the itbs. it is more linear. I'm running a small td04h-14T and it is overs pooling with the boost duty @ 100 at idle and partial throttle, causing a wierd pfft noise seemingly randomely. I suspect it is likely the pathetic vacuum generated by 1 itb, not opening the bypass valve at partial throttle and idle. I may have to run with the wate gate a wee bit loose to bleed off at idle and high rpm cruise, maybe try and find a weaker bypass valve spring. then drive the boost duty to 0 with the target table