Uncontrolled Boost???

[andys2]

OK here's a newbie question.....

I have an EJ20 with a VF10 and a boost gage. My pressure sensor port broke of so now I have no feedback to my ECU for boost control.

1) Is there some kind of default duty cycle to protect agains overboost? Without that sensor is the wastegate supplied with pressure or is the solenoid closed all the time?

2) If the solenoid is closed and I have no 'extra' pressure to open the wastegate how dangerous is the VF10? I mean it self requlates at some point - I think. Will I get enough creep to damage someting? What's a dangerous boost pressure? I have the knock sensor - how much protection is this?

[DLC]

The stock wastegate spring on a USDM turbo would open between 6-7 PSI, far below what it would run otherwise. If your wastegate is working properly, it doesn't need anything to prevent it from overboosting.

[BAC5.2]

If the wastegate is shut, the turbo will continue to spool for quite some time, probably stopping around 25psi. That's far to much psi.

Watch your boost gauge. If it goes over what it did before, then let off the gas.

If the solenoid is broken, connect a hose from the outlet to the wastegate can. That will allow the turbo to only run wastegate boost.

Without a hose, you will break something very quickly. Ask DZX about that. His friend blew a hole in his motor.

[Richard]

If you don't have any kind of upgrades to the fuel system and lean out, you're really asking for it. Detonation is very, very bad. I wouldn't run much more than stock +3 lbs. All you need is one good oops and your motor's toast.

[andys2]

Ok, thanks for the info.

I'll run this next rally on stock boost but I have already started my big boost controller.

The plan is to add two more injectors the top of the manifold. One for fuel and one for cooling water. With a bit of luck this mixture will be distributed evenly to the four cylinders - or else........

I have started a design for a very crude controller that has two inputs: MAP and O2 sensor and three outputs - boost solenoid, water injection solenoid and fuel injection solenoid. Of course the basic idea is to control boost pressure. However, the unit will have a crude control loop to protect agains lean out conditions. At low boost the protection won't be so agressive but at boost pressures of 15PSI and above the controller will proabably be a real fuel dumper. Oh well, it's easier to by fuel than pistons. I'll careflly monitor what's going on with a wide band O2.

The idea is to make the controller cheap, simple and easy for anyone to build. Oh and it also has to be very, very, very, very effective.

So, stay tuned and thanks for the help so far. This board is very helpful.

[andys2]

I tried the car out tonight. Not bad not bad. With the solenoid connected but the MAP sensor port broken the car spools up to about 6psi. With the wastegate disconnected it spools up to about 15. I havent't really done a long pull - just a second gear jaunt up a small piece of road. Still, it seems to taper off at 15. Maybe it'll go to 25 but I don't quite no how - nor do I want to see it.

My intercooler pump is broken (siezed maybe?) so I guess there'll be more power with a cooler charge. Anyway, 15PSI was pretty OK. Lots of wooshing noises to be had

BTW the universal BBFE (big boost fuel enricher) thing I am working on only needs MAP and TACH inputs. Wide band O2 would only be necessary for accurate tuning.... I'm new at this stuff.

[Richard]

Sounds interesting. Keep us posted.

[andys2]

Took car to work this morning. Don't use plastic zip ties on the intter cv boots. zip tie broke and puked goop all over my down pipe. Holy smoke show.

6psi on no intercooler seems to work ok. I'm scared to turn it up with no IC pump. What do you guys think?