Can I get Manifold Vacuum from here??

[jayfire]

I am putting a Holley Sniper on top of my blown hemi and it says it needs to read manifold vacuum from a remote source. I have these 2 ports on the back of the Crager intake. One is plugged and the other was used for blower gauge. Can I use one of these as a vacuum source and run it to the Sniper unit? Thanks

 

[BeepBeepRR]

I think you would be ok using it. Its a MAP sensor so its looking for Manifold Absolute Pressure and you cant get more pressure than that.

 

[steve340]

No that will not work that fitting will see blower boost at times.
If you have carburettors/spacers connect to the constant vacuum fitting on or below the carb baseplate but above the blower.
The Holley system may have a suitable port - might pay to give them a call.

 

[BeepBeepRR]

No that will not work that fitting will see blower boost at times.
If you have carburettors/spacers connect to the constant vacuum fitting on or below the carb baseplate but above the blower.
The Holley system may have a suitable port - might pay to give them a call.

I didnt think about it being below the blower.. Derp. So yes what Steve Said. Don't listen to me.

 

[jayfire]

This is what the instructions say. So, I should use a port in the carb spacer?

 

[1 Wild R/T]

The port you choose is correct... It will act as a boost reference...
reading in the carb spacer won't give the reading you want...

 

[steve340]

I was not 100% sure but it seems the MAP sensor - though the instructions say pressure they would be clearer if they said vacuum or negative pressure.
When the blower goes in to boost you will get a positive pressure below the blower. From the tutorial by Engineering Explained that is the opposite thing the MAP sensor needs to see and it would not work correctly and probably would be damaged.
Ring Holley if that sensor is only to see vacuum/negative pressure you need to be above the blower as I said in my earlier post. The port you show in your original post will see both negative and positive pressure.
I think I am right because in the Holly info you posted it says no change for a naturally aspirated engine required. A NA engine never has positive pressure in the intake.

 

[1 Wild R/T]

As stated in the info posted above
"Draw through Supercharger Applications: When using the Sniper EFI on a draw through boosted application (I.E. positive displacement blower such as a 6/71), the throttle body must be converted to read manifold pressure from a remote source that sees manifold pressure."

The Sniper needed to know if the engine is under boost to adjust the fuel & timing properly... If it doesn't know boost is present it'll over advance the timing & provide to little fuel.... Which will lead to a lump of melted aluminum where your pistons use to be....

BTW have you downloaded the revised software for a boosted application?

Correction, apparently that was only on earlier Snipers, current units don't need this..

 

[jayfire]

Just called Holley Sniper tech support, and it does need to see the manifold vacuum, so my ports I have available will work. Thanks for the insight.