would like to do an A/C cutout at WOT or 4500 RPM up. any suggestions on a how to? with the weather getting nice I see more foot in it time while riding with the A/C on. have thought of using a tach w/light. let the light wire trigger a N/C relay to the compressor wire.
Several options, Frank. Best would be to use one of your ecm outputs(can't remember which one you have.. grid? Not sure what rpm based options are available but I'd bet you have plenty of rpm and MAP based adjustments there.. have to check with MSD or instruction manual. Some vacuum operated switches as well.. too many years ago so not sure which brands/part numbers. Also could look at the 700r4 adjustable vac based converter lockup switches.. have used several through the years on those trans and can't see why those wouldn't work if udjusted tighter to only break circuit at lower manifold vac levels. That would be more load based regardless of rpm's and likely better imo. Then there's WOT switches on throttle body or gas pedal. From there you get into OEM cutout relays wired into the clutch circuit.
I talked to MSD and was told the Atomic EFI has no provision for this option. the power gain will be nice but the reason for the cutout is to not spin the compressor to an unreasonable high RPM when engaged... I can get a compressor that's good to 6,000 RPMs but it doesn't state if it's compressor or engine RPM. I'm thinking the compressor to engine RPM isn't 1 to 1.
Ok, then go for the superior adjustable vacuum switch to cut a/c clutch anywhere between 1-6 or 6-22 inches depending on which unit you decide on. I'd go for the 1-6" seeing as that will be more inline with actual manifold vac once you're deeper into the throttle. Can be wired inline to your clutch to be always on(when energized by dash switch) and then will disengage when vac setting is reached when manifold vac drops. Maybe set it around 3-4" to break the circuit? Plus side will be that it's completely rpm independent and based on engine load to give a few extra horses when you're having a little extra fun. And likely that the condenser and ducting will be saturated with cool enough air that the vent temps won't rise very quickly or noticeably unless during extended WOT runs.
......why didn't I think of that...LOL I'm thinking if there is a way to cut the power to the compressor then the fan will still be running. my A/C comes on with the low fan speed. I would have to turn the fan off to kill the compressor....
Can't you just install the vac switch after the fan.. and before the a/c clutch? Shouldn't matter if you have the fan and a/c clutch in series or parralel.. it simply breaks the circuit leading to the a/c clutch when the vac reaches whatever level you set the switch for.
It may not be a problem Frank, but the only thing I'd be slightly concerned about is the load draw/amperage spike going through the switch when the clutch disengages/reengages. Not sure what the clutch itself draws, wouldn't think too much since the OEM wire gauge is nothing huge, and I've only had experience using them on the trans lockup solenoids which are surely very low draw in comparison, but just figured it was worth a mention to maybe check that switches max amp capability. Been quite a few years since I've contacted them, but IIRC Superior had a tech line that was very helpful and might be worth a holler to know for sure to avoid any issues or wasted time and cash. Good luck with it however you decide to go.
thanks ... going to start doing a little looky see tomorrow. talked with my friend David today and he mention the wire size also. would wiring it through a relay be an option?
A Guy on the LS1tech board had a concern with a vacuum switch. he is thinking the vac may come back before I get out of it...then the compressor would kick back in at 5500-6000 RPMs he is suggesting a...micro switch... I'm thinking if I lift at 6000 the micro switch would do the same thing...
I don't see how that would even be possible unless you have a severe restriction in the induction system. WOT should produce 0" of manifold vacuum. Even 2bbl carb or plate restricted roundy round racers rarely ever hit 3-4" manifold vacuum at much higher rpm that you'll ever be spinning yours. And even if it were possible.. all you need to do is adjust the vac switch to a slightly higher vac level.. say 4-5". It is possible the switch would reengage the clutch if you suddenly got out of the throttle, snapped shut, as manifold vac spikes back up. Only other options I know of would be a window switch that uses an adjustable rpm range to cut power(or supply it depending on chosen part#) to a circuit between say.. 4500-6500(set to above your shift points). So off would occur at 4500.. and back on again at 6500. But since you'll never make a 6500 rpm shift it would never actually resupply power to the a/c clutch citcuit. Only reason I didn't mention it in the first place is they are not cheap. Around a 100 bucks for the chipped versions.. over 150 for fully adjustable digitals. Could also set it to power on between idle speed and say 4500 rpm too. After that it would cut power to the clutch. Only other way I know of beyond that would be a shifter mounted manual kill switch.. similar to a nitrous switch.. only reversed to kill power rather than supply it.
