boost control, overboost protection

[stace]

I assume I can use the misc, boost control for overboost protection while trying out my new ebay waste gate right? Just set it to something like 18psi. what are the precentages for?

[hakcenter]

I assume I can use the misc, boost control for overboost protection while trying out my new ebay waste gate right? Just set it to something like 18psi. what are the precentages for?

PWM duty cycle for the stock boost controller / any PWM controlled boost controller you put on those wires.

[stace]

Im using manual boost controller, so i guess that whole section dosent even matter for me. So how do I creat an over boost pretection?

[hakcenter]

Your over boost protection is the waste gate.

If you limit boost on the charging side, the turbo is still going to overspin. Only way to prevent over boost is with maybe a fail safe waste gate, or some of those weird boost limiters.

http://www.928motorsports.com/parts/boostlimitervalve.php

In any regard, funny to find ForceFed86 somewhere else talking about the same thing.
http://www.theturboforums.com/smf/turbo-tech-questions-only!!!/pressure-relief-valve-for-over-boost-safety/

[stace]

I thought ecmlink had a overboost that altered timing or fuel when the boost cut was reached. I was wrong, but I guess AEM does.  The best aftermarket add-on Ive seen is a solinoid that shuts air off to the BOV so that the overboost pressure opens the BOV but it costs $200

I was thinking, could I use the stock boost solinoid for the boost cut, inline with the BOV and set the boost cut percentages to close the solinoid if the Wastegate fails and I over boost?  Could that be done?

[snapc33]

Megasquirt has a over boost protection that is pretty much just another rev limiter over X psi.  Set it to a low RPM and if you over boosts it will cut the motor out.  I have used it a lot to protect from more boost then anticipated when adjusting manual controller that always isn't always predictable when you up the boost. 

How easy would this be to implement Hak, just another leg up on others.

[stace]

Thats what I was thinking, a rev limiter based on an adjustable psi.

[hakcenter]

So everyone wants to get rid of fuel cut, but now people want boost cut ? 

Do-able just by tricking the motor into thinking its over-reving.

[stace]

ya, but overreving wont be effective, cause boost spikes cause by failing wastegates happed at mid rpm ranges. If my wastegate diagpram rips apart. its gonna happen at like 12psi ut shoot up to what ever psi my motor can take before it explodes...way before it would hit any rev limiter. 

The supra forums, use a hobbs switch on their coil pack, so that when the boost hits a undesirable level the hobbs switch cuts the power to the coil.

If I could set the timing to cut at a adjustable boost level, then that would work. I could do it with the fuel,using the VE maps but I wuld think starving the motor from fuel at 6000rpm and 20+psi would be bad.

[snapc33]

So everyone wants to get rid of fuel cut, but now people want boost cut ? 

Do-able just by tricking the motor into thinking its over-reving.

Lol

Stace:
I'm pretty sure if you set your rev limit to 2500 rpm and wire you waste gate shut, you would have a hell of a time over boosting.  So a limiter set to 2500 come on at a psi level would shut it down pretty quick

[hakcenter]

ya, but overreving wont be effective, cause boost spikes cause by failing wastegates happed at mid rpm ranges. If my wastegate diagpram rips apart. its gonna happen at like 12psi ut shoot up to what ever psi my motor can take before it explodes...way before it would hit any rev limiter. 

The supra forums, use a hobbs switch on their coil pack, so that when the boost hits a undesirable level the hobbs switch cuts the power to the coil.

If I could set the timing to cut at a adjustable boost level, then that would work. I could do it with the fuel,using the VE maps but I wuld think starving the motor from fuel at 6000rpm and 20+psi would be bad.

What part of

Do-able just by tricking the motor into thinking its over-reving.

doesn't make sense ? Lol, it'll cut fuel cause it thinks its over an rpm limit. Very simple ideal.

[snapc33]

The supra forums, use a hobbs switch on their coil pack, so that when the boost hits a undesirable level the hobbs switch cuts the power to the coil.

How about use the fuel pressure solenoid to trigger a relay that cuts power to the coil over a set psi.  Then you would have ignition cut.

[stace]

but i dont know how to trick the ecm to think its over reving?

And I myself dont really want to play around too much with my coils, Im running a 92ecm with 90 coils on a 2g head. I consider myself lucky it even fires!

Im thinking if I can get the boost solenoid to act as a open/close valve instead of a pulse by changing the percentages of the boost cut, then I will use it to open the BOV boost source to the atmoshere, allowing the IC air to push open the BOV.

If I were to cut fuel, could I just drop all the VE tables values past say 20psi to 0 so if im running 16psi and my wastegate fails, it cuts fuel at 20psi.?

[hakcenter]

but i dont know how to trick the ecm to think its over reving?

And I myself dont really want to play around too much with my coils, Im running a 92ecm with 90 coils on a 2g head. I consider myself lucky it even fires!

Im thinking if I can get the boost solenoid to act as a open/close valve instead of a pulse by changing the percentages of the boost cut, then I will use it to open the BOV boost source to the atmoshere, allowing the IC air to push open the BOV.

If I were to cut fuel, could I just drop all the VE tables values past say 20psi to 0 so if im running 16psi and my wastegate fails, it cuts fuel at 20psi.?

Could drop the VE values ya. I've never tried 0 x 0 multiplier to see if injector pulse width goes to zero.

Boost solenoid is strictly PWM no way to really change that besides adjusting the percentages. 0 to 9 million.

I like the FPR idea the most honestly. Wire a relay to the FPR that connects the power to the coils main wire. Then just set a code to drop it over whatever rules you want, including but not limited to boost pressure.


Dumping the boost pressure, isn't necessarily a good idea, the turbo is just going to over spin even more to try to pick up the lost pressure. You don't want to be able to drive through a safety that you setup, you want to know it happened ie rev limiter type.