Lost all boost control

Hi Guys,

I have a CA18 in a KE70 Corolla. The vehicle runs on E85 and has EV14 1000cc injectors fitted. The turbo is a Garrett GT2860R and the ECU is a Haltech Elite 1000.

The ECU, injectors and the turbo have all just been fitted.

All the steady state tuning was completed and boost control was being set up. Open loop boost control was all working and set to 125kpa Guage. The BOV mounting failed during a run and the BOV came loose. The mounting was rewelded and closed loop boost control turned on.

Boost now contines to rise until you let off the throttle. I have seen boost spikes to 140kpa guage when boost cut comes in or tries to.

What I have checked.

reset back to open loop no different

reset open loop to zero no different

Bypassed mac valve and connected pressure line directly to wastegate actuator. no differrent

Tie wired wastegate fully open - Boost onset is delayed however we are still seeing 100kpa gauge at 5500+rpm

hose from compressor outlet to actuator is not blocked

Base timng set to 20 degrees.

Cam timing. Correct.

Haltech Map sensor reads the same as the dyno sensor.

Removed Divorced Dump to check for possible blockage in the waste gate ETC. Nothing abnormal found.

Added timing to make sure it was not anti lagging due to low timing. No different. Total timing at 125kpa was set to 20 degrees. No differenet

Wastegate actuator has been checked off the car. It is operating to the specs supplied to me by MTQ

Rechecked dyno logs of the runs. We had boost control at wastegate pressure on the logs, 90kpa gauge then at 10kpa increases above that until around 125kpa.

No visible or audible exhaust leaks betwwen manifold and turbo. It has the stock CA manifold.

WOT lambda is 0.8

Happy to hear any ideas

Darren

"Open loop boost control was all working and set to 125kpa Guage." Got a screenshot of a log showing your boost curve from low RPM WOT up to redline during this period?

It sounds like old fashioned boost creep to me. Install a more restrictive exhaust (install a catalyst, resonator, more restrictive muffler) and you might see it go away. Or switch to an external wastegate manifold ($$).

the fact you're making 100 kpa gauge with the wastegate fully open suggests that the turbo is 'running away' or boost creep.

If you don't mind 'modifying' the turbo I had a customer port his own internal wastegate opening after suffering major boost creep on an ebay purchased GT2871, this brought the boost under full control.

It's either that or you can install exhaust restrictions, CAT's or restrictor plates, or just seal the internal gate and go external as Arghx7 suggests

Please see attached photo of the dyno graphs. The green is of open loop when being set up and the red is after the BOV was fixed.

Green you can see boost control coming in at 220ish and slowly dropping away.

Red you see boost rising a lot earlier and peaking at 245ish before I pulled out of the run.

Unless I am misunderstanding the graph I had control. Changed a BOV and lost all control.

Green line does show an expected response (slow rise, peak, taper off). So yeah, something could have happened.

Can you confirm somehow that the gate is actually opening when you boost the car? You said you have a divorced wastegate dump - can you hear the gate opening? Two ways I can think of are to install a thermocouple (EGT gauge) in the dump pipe to confirm hot exhaust flowing, or install a string potentiometer to measure the linear position of the wastegate arm and confirm it is moving. The string potentiometer functions like the wastegate position sensor on a newer car with electric wastegate.

I can confirm that noise is audible from the screamer and have visually seen the waste gate open to 45 degrees or so when on the dyno.

What I find intersting is the red line which is gate pressure only seems to ramp up quickly like some form of antilag. We are going to remove and black off the BOV and retest.

We also just tested the pressure at the wastegate vs the manifold. A 27 kpa differance was recorded.

Original BOV/fittings were leaking significantly from the start, absorbing more air/turbo shaft power for a target manifold pressure, requiring less exhaust wastegate bypass. You were intake wastegating. You have removed the leak, I assume it is now making more power for boost lower in rpm before running away without the leak? Port your wastegate/add a larger flapper or restrict the exhaust. Intake wastegating/leaks are a lot harder on the turbo and cause higher exhaust temperatures.

This was our thoughts now also, Just for testing we have fitted a restrictor into the dump reducing it down to 50mm.

This made no difference at all to the boost pressures or the graphs. Next step is to port the wastegate or fit and external gate. Still does not make a lot of sense as the turbo supplier claims the gate sizing is correct for this application.

I'd agree with Slides diagnosis - I think you had a problem all along that was masked by a leaking BOV. The graph looks like a classic boost creep situation however this is normally the result of a wastegate sizing/installation issue which you should be able to rule out with a 2860 with internal WG. Is it possible that your exhaust dump design is artificially limiting the wastegate movement?

The issue has been sorted now.

The issue was two fold. The internal wastgate needed to be ported. This did help. Also It was found the amount of timing in the lower part of the map was to retarded and causing an anti lag type effect.

8 degrees was added lower in the map and with porting the boost was back controllable.

Thanks to everyone for your input.