What to kill

[Razor]

Ok..making a safety device..what circuit could be killed and the motor be brought down in RPM's safely without losing total power.

Idea is for NOS,alky,propane whereas if under high boost and ya lose the adder..you can bring the motor down..kinda like a rev limiter.

I'm thinking TPS be brought to 1.5 volts via a relay with a simple voltage divider..that ought to cut the fueling and timing.

How bout the MAF..bring that one down to 2.5 volts..looking for ideas..aside from killing power to the ECM..

interrupt the crank sensor? until boost is at a safe level?

thanks guys..making a better mousetrap

Julio

 

[BoostKillsStres]

As far as I've seen in the code, TPS has no effect on timing only LV8 and RPM in the main timing table so that would only cut fuel which would lean the car out with still having full timing...don't think that would be a good option. Good idea, crank signal interrupt would be my guess but only every other pulse so things don't load up. Maybe a boost seloniod reduction to pull and limit boost but I know the sol is a modulated voltage so a complex controller might be needed then what do you do, trigger it for a time period or some type of alky/propane pressure switch or something.

Also, pulling MAF is going to only pull fuel, again the engines at full boost and will go lean.

 

[Razor]

Boost selenoid is an easy thingy..PWM supply to it..done..

But that wont bring down a car at WOT..it will reduce boost which is a start..

Playing with the crank pulses is a tricky thing..since injectors timing is done by this sensor. And wouldnt want misfiring injectors..back to the cutting the fueling.

How bout bringing down ecm voltage? to 9 volts

I can make the circuit..just need ideas..

Thanks Mark..

 

[boostcreep]

I remember reading how someone killed the power to the fuel injectors for like 3 seconds or so, just enough time to lift your foot off the gas. Seemed to work pretty good that I recall....


Nick

 

[BoostKillsStres]

OK, so we don't want to mess with fuel and boost DC% to 0 would only limit boost to whatever the WG spring was set to and if someone isn't using the full stock setup aka tuner style or external gate that won't help anyway. Maybe you should research exactly how the EST sensor works as maybe you could interrupt fire there or maybe at the ign module.

I figure spark is the only thing you really want to play with for this. I kinda like the boost DC% to 0 as if the car falls on its face and you look over and see 12-14 psi your going to know somethings up.

 

[TurboBuickSix]

How about making the ECM see knock sensor signals that don't (yet) exist,therefore cutting boost and timing???

 

[BoostKillsStres]

Dave, I like that idea, good one. One thing to remember if this method is tried is that most chip gurus handle knock retard recovery and incidents via their own parameters so this probably won't function the same in everyones TR application so some external adjustability would probably need to be incorporated into the device.

 

[Razor]

Well anything put to the knock input will show up on your scan tool big time. a signal could be injected into it for a brief that shows 30 degrees for example..wonder what 30 degrees would do timing and fuel wise..

The top end limiter on our cars cuts fuel off. Afraid that cutting fuel off at high boost is a bad thing..probably will work..just wanted something to take the Huff out of it.

Be nice to get an electric gate that would bleed off all the boost..kinda like an electric blowoff valve..that may be another idea..connect an air selenoid to the up pipe for instance that could flow some volume...as soon as the safety hits..Poof release the pressure.

 

[TurboBuickSix]

Originally posted by BoostKillsStres
Dave, I like that idea, good one. One thing to remember if this method is tried is that most chip gurus handle knock retard recovery and incidents via their own parameters so this probably won't function the same in everyones TR application so some external adjustability would probably need to be incorporated into the device.

I was thinking burning a chip that works with this idea too.Improving on GM's method of knock control might be the way to go ..maybe not??

 

[BoostKillsStres]

Dave, I know what you mean, I've thought about the same thing in burning my chips. Its kind of a catch 22, you want to pull a little power out if knock is experienced but then again if you have the car tuned perfectly any knock you see should be minimal and you shouldn't need to pull any power out....decisions..decisions...

 

[Dan K]

If you want to keep the retard tables to your "normal" values...is there a way that you can have the ECM pull more timing if the knock count goes higher?

I'm pretty sure that on an LT1 knock retard is based off of knock count and when the knock count jumps a lot quickly the ECM will pull more timing than it would have if the knock count was only going up a couple of counts in the same time period.

 

[BoostKillsStres]

No count based retard that I've ever seen in the code. We've got your basic retard attack and recovery rates and burst knock retard with boost solenoid DC reduction.

There does happen to be a max retard before lowering DC which is set to 14.9 in teh BBKJ stock chip and allows for 12.5 reduction in DC for knock and PE. So, maybe if I understand it correctly you could set MRBLDC to something low like 5 degrees and set the the DC reduction very high and it might just do the trick but I'd like to see someone with a ECM bench test to make sure.

Or I guess I could set the MRBLDC to 1 degree and set the DC reduction to something nuts like 90 % and make a little knock happen to see what the boost on the car did...might be something to play with...thanks for the thought.

 

[Eric Stage I]

The Buicks have knock counts also. The amount of "new" counts per cycle (through that particular code) is multiplied by the knock attack rate to give you spark retard. The code is in the $E5FC-$E658 area.

Eric

 

[Razor]

So if ya make an oscillator circuit matched to the knock frequency..inject that in..that ought to pull the car down? I guess the amplitude of the signal dictates the severity of knock displayed.

I know my turbosix tuner you can make alter the recovery rate...but that doesnt make it easy for everybody.