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Looking for a QC check on my relay wiring. The Holley Sniper EFI has an input and an output for A/C. The input tells the system that the A/C has been turned on. The output cuts-off the A/C when you smash the peddle; default is 65% WOT. Both are ground signals. So, for the input, the system is looking for a ground signal. And, for the output, the system grounds that output wire.
I have an older Vintage Air a/c system. It uses a single wire to engage the A/C compressor clutch. When it's 12V, then the a/c is engaged.
I designed the relay wiring shown in the drawing below. I'm also pasting here a marked-up scan of the Vintage Air wiring diagram.
DOES THIS LOOK CORRECT? (I don't want to fry my Sniper brain)
That will work but you don't need to wire AC input if the tune is good. All it does is bump the idle. I don't have mine in, the out is programmable, I'm at 80%.
That will work but you don't need to wire AC input if the tune is good. All it does is bump the idle. I don't have mine in, the out is programmable, I'm at 80%.
I don't see why you wouldn't use the input. The more info the ECU has, the better it can deal with unforeseen issues/changes in situation.
Up to you, it's not mandatory and all it does is bump the idle based on whatever you set. Again I have zero issues my car runs just fine. AC request shouldn't make your car stumble. Check the holley forums you will get the same advice from Danny and many knowledgeable folks.
And you may not want to waste the input and assign it to something else is a reason why
That will work but you don't need to wire AC input if the tune is good. All it does is bump the idle. I don't have mine in, the out is programmable, I'm at 80%.
Yes, that was I have read on the forums. I figure I'll try using it. If, when I start to wire up the relays, if it starts to seem to klugy or whatever, I just won't do it. It's not necessary. But, I'm just being prepared to be able to do it. As the other poster said, more info for the EFI brain should make things work better.
And you may not want to waste the input and assign it to something else is a reason why
I would love to use the Holley CAN oil pressure gauge sensor data as an input to the Sniper EFI. Are you familiar enough with it to know if that's possible? I'd like to have the system shut down if oil pressure drops below say 5 psi...
I have to check but you don't need the Can to do that. You can take a TBI / TPI oil pressure switch and wire it inline to the fuel pump relay. No oil pressure no gas. It's the poor man method but it's how GM did it from the factory for a long time.
I have to check but you don't need the Can to do that. You can take a TBI / TPI oil pressure switch and wire it inline to the fuel pump relay. No oil pressure no gas. It's the poor man method but it's how GM did it from the factory for a long time.
OK yeah I actually have that now on my fuel pump control circuit. I also have the Ford impact switch. I want to do away with all that stuff. It clutters up the engine compartment.
Up to you, it's not mandatory and all it does is bump the idle based on whatever you set. Again I have zero issues my car runs just fine. AC request shouldn't make your car stumble. Check the holley forums you will get the same advice from Danny and many knowledgeable folks.
And you may not want to waste the input and assign it to something else is a reason why
What I'm about to say only seems to happen when it's 110+ outside in the summer, so keep that in mind.
It has been my experience that without a slight bump in idle speed, when the AC compressor cycles/kicks on, engines can tend to stumble at the stop light. Modern cars (ex: my C5) not only track AC compressor cycling, but also compensate (calculated necessary idle air flow adjustment) for the turn on of electric fans since the momentary spike in amperage load can also cause a stumble.
I have to check but you don't need the Can to do that. You can take a TBI / TPI oil pressure switch and wire it inline to the fuel pump relay. No oil pressure no gas. It's the poor man method but it's how GM did it from the factory for a long time.
But that would prevent the 2-5 second pre-prime function of the fuel pump (unless you wire a separate trigger).
Edit: You could use the oil pressure switch to kill the power to the distributor/coil. No oil pressure = no spark = no run.
Last edited by ChrisLSx; Nov 30, 2020 at 05:12 PM.
Chris - in AZ in that heat yeah I might consider wiring it in too. Factory ECU's measure air via a MAF and are a LOT smarter in those areas vs Holley and using Speed density. Not saying is wrong or right its there for a reason and needed in some cases. I guess the answer is it depends
I looked and the CAN Oil gauge is not compatible with the Sniper out the box. Only HP/Dominator/Terminator lines.
Chris - in AZ in that heat yeah I might consider wiring it in too. Factory ECU's measure air via a MAF and are a LOT smarter in those areas vs Holley and using Speed density. Not saying is wrong or right its there for a reason and needed in some cases. I guess the answer is it depends
I looked and the CAN Oil gauge is not compatible with the Sniper out the box. Only HP/Dominator/Terminator lines.
Just as a clarification:
The factory ECU uses a hybrid MAF/SD function to calculate it's air/fuel. By nature, the MAF is (relatively) slow to respond to sudden changes in air flow (such as abrupt throttle changes, sudden loads from AC or fans, etc.). Instead, the ECU relies on the VE table as the default (even failover) air/fuel. It then uses the MAF to blend/smooth and for steady state (cruising) situations where the air flow is stable and consistent. But yes, the factory ECU does have a lot more info being fed into it and therefore it's smarter in that respect. Racers like to talk about the factory ECU's limitations, but what they see are limitations are just things it was never designed to do (ex: run a wideband O2 or have a multi-step power adder adjustment).
With that understanding, the Holly SD isn't all that different from the factory ECU SD (less MAF of course). The biggest difference I see is that the Holley doesn't seem to have as many customer accessible fine-tuning abilities (when compared to say HPTuners). I feel Holly really choked down the access so the average "Joe Hotrodder" didn't get overwhelmed. Thus why it's got "pre-sets" and is "self-tuning".
Last edited by ChrisLSx; Nov 30, 2020 at 05:33 PM.
Thanks I knew that Was trying not to hijack this thread. I agree and disagree with some of your statements vs HP Tuners & HP/Dominator. However to keep this thread focus I think the OP got what he needed.
I have to check but you don't need the Can to do that. You can take a TBI / TPI oil pressure switch and wire it inline to the fuel pump relay. No oil pressure no gas. It's the poor man method but it's how GM did it from the factory for a long time.
No, GM never did that. The oil pressure switch was a backup to the relay only. Every GM engine with an oil pressure switch wired to the fuel pump would still run without it as long as the relay was working. This has been well established by now, but the wives tale of the oil pressure switch being used to run the pump still persists.
Hi all, I'm looking to finish up the EFI Holley Sniper conversion on my 76 L48. Either my ADD is kicking in or I just can't find the a clear answer related to AC Kick. My AC compressor is not mounted at this time (it's out to be rebuilt)so I'm not sure what my car will do once I turn it on with the Sniper. I'm just trying to be ready once I get it installed. I guess my biggest question is does the AC kick need to be wired? I have original GM fan and AC setup. If AC kick is needed/recommended, what's needed? Seems like a positive to negative relay connected to the positive AC clutch wire to the relay then to the orange Sniper AC Kick wire? Thanks.
Yes, I read it; No worries; Seems the OP is talking about a Vintage Air system. Others are saying, it's needed, others saying it may be needed, others saying it's not needed. At least that's the way I read it. Guess I will have to just wait to see what happens when I get my compressor back and turn it on.
The answer is it depends. You should if you don't need the input for anything else, doesn't hurt and will help if you have any gaps in your idle tune. I didn't but I have my reasons
Ok, that's the way I read it; No clear answer. LOL. Thanks; To confirm, I am thinking about the setup correctly - positive to negative relay connected to the positive AC clutch wire to the relay then to the orange Sniper AC Kick wire for original GM AC system correct?
Sniper EFI: A/C control wires
