Terry'sToy

i'm new here, but i've read alot and i appreciate the technical advice. i posted this in the engine forum(oops). so i'll re-ask my question. i thought i read about a switch that kills the spark to the engine if you were to loose fuel pressure under boost.(this would of course stop that horrible detonation). if anyone can help i would greatly appreciate it. Thanks

Terry'sToy

maybe i'll rephrase that question. can you use a hobbs switch to cut spark if you were to loose fuel pressure? TIA

y2khawk

iTrader: (5)

Don't see why not

You could interupt the 12V supply to the coil packs to effectively cut ignition.

Need to make sure you have enough prime pressure so get spark during crank.

But i don't see why not.

one thing to consider is what happens to a charging coil if you cut power in the middle of the dwell cycle. Does it fire? Will it cause excessive advance? Does it really matter at that point?

Just ideas <img src="gr_stretch.gif" border="0">

Terry'sToy

thank you very much for your help. those are legit concerns. i think that once you drop the primary voltage to the coil, the secondary voltage drops to zero. but if you cut the primary mid way through the dwell cycle, then you would get a partial spark; provided it is at a high enough voltage to jump the gap.

Terry'sToy

you could also put in a manual switch to bypass until you get it started.

y2khawk

iTrader: (5)

Don't see why you couldn't put a manual override in parallel w/ the hobbs. It'd work

You should have enough pressure from the pump prime to enable the switch anyway. But the pump comes one once you crank anyway. So it may result in long cranks, but it'd work by itself.

Not sure what the coils would do, as they are not plain old coils. They do have some control circuit to them.

You'd think they would respond "nicely" if power were lost <img src="gr_stretch.gif" border="0">

Terry'sToy

i do believe you are right with the priming and cranking. as for the coils, where is the circuit? is it visible under the hood? does anyone have a schematic?
Thanks again Harlan. I've been reading about your car for quite some time now. very very impressive. Turbo's are the best, most efficient way to boost. very little parasitic loss.

highgmc

my fuel pressure is between63-68 normally and under boost drops to 58ish, I contacted ati and they said this is ok and normal on the #5 kit.

slow

iTrader: (7)

why not get a second hobbs for 1 psi for the boost element, so you can only cut spark when under boost?

Ryan.

Terry'sToy

terry99ta. thanks for the info. what i'm trying to do is cut the spark if the pressure were to get any lower than that. ie. if the pump were to die.
slow. can you explain this a bit more for me as i qdon't uiet understand what you mean.

y2khawk. so far i've figured that the coils have four wires...one power,one ground,one trigger and the fourth i don't know. maybe someone else can help or has a drawing i could see.

i appreciate all the input. i'm trying to build a system for LS1's and 4.6L mustangs.

sometimes you don't have enough time to look at the fuel press.gauge when you are racing.

slow

iTrader: (7)

wire a second hobbs switch so your "deactivation" circuit will only be activated when your under boost.

have the second hobbs switch in your intake somewhere, so it reads boost, when the intake is under presure, (only when makeing boost) the circuit will close/open activating a relay which when you lose fuel pressure, will pull the power from the coils.

This way, you wont have any problems with the circuit causing problems with starting (although i don't see any problems, as fuel pressure 'should' be full when you are starting, very low injector load, and as long as you allow 1 second between on and start, it should have full pressure in the lines)

if you need any schematics or anything, i can try to give you a hand.

Ryan.

Terry'sToy

slow. excellent idea!! thanks for the help.
i would really like some schematics for the wiring harness that feeds the coil packs.
what do you guys think about maybe cutting the power supply to the coils by interrupting the power in one of the fuse boxes. ie.INJ-1,INJ-2 or PCM IGN or PCM BAT

slow

iTrader: (7)

no problem <img src="gr_stretch.gif" border="0"> glad to help, unfortunately i do not have any schematics for the LS1, i do have a 2000 mustang CD shop manual, and might be able to get some for the 4.6, i can look if you need that info.

I could help with any normal electrical schematics, but it sounds like you have a good knowledge on that subject.

Maybe Harlan might have some info on the coil packs?

Ryan.

y2khawk

iTrader: (5)

Pink wire feeds 12V to the coil packs
Black and brown are grounds, one is power ground and the other is signal ground.

The other 4 are control wires.

interrupting the pink wire will cut ignition on all coils.

Terry'sToy

y2khawk. that's fantastic. that's just what i needed. Do you happen to know where a person can get the wiring diagrams? Dealer maybe??
Thanks agian. i'll post a wiring diagram for this system for everyone to view and give their input.
give me a few days to draw this up as i'm putting my converter in right now and working on a couple of GT's
Or if someone else wants to post a drawing that would be great.

red ws6 99

You can get a wiring diagram for every circuit in the car from a Helms manual, the are fairly detailed.

Gary

Terry'sToy

Thanks Gary. i think i will get one of those. I'm sure i'll use it for other stuff over the years.

By the way... I finished my install of the ST3500 last night at 6pm. I started at 9am and took an hour and a half break for lunch. My buddy showed up to lift the trans out and put it back in. i did the rest myself. I'm very pleased with the results. This car is out of hand a bit. Yahoo.

Terry.