Low Vacuum on Holley Sniper EFi
#2961886
09/07/21 02:44 PM
09/07/21 02:44 PM
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Joined: Jul 2007
Posts: 732 eastern,Ky
70RT Charger
OP
super stock
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OP
super stock
Joined: Jul 2007
Posts: 732
eastern,Ky
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Is there anybody running a Sniper that has low vacuum with good results? My Comp cam is a XR-286-HR producing 8 hg at the Intake and 7-8 hg at the carb at 900 RPM idle.
Last edited by 70RT Charger; 09/07/21 02:45 PM.
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Re: Low Vacuum on Holley Sniper EFi
[Re: 70RT Charger]
#2961890
09/07/21 03:01 PM
09/07/21 03:01 PM
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Joined: Jan 2003
Posts: 31,082 Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,082
Oregon
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Sure, lots of people. Here is a video of a RoadRunner that I installed a Sniper on. This is a 700 hp engine with a big solid roller and it has open exhaust. https://www.youtube.com/watch?v=sNeBSOqpO40There are some tricks to make it work since the Sniper won't run on a low vacuum engine right out of the box. You'll need a laptop and the CAN to USB cable as well as the Sniper software. Once you have all of that you'll need to adjust the base fuel table, adjust the ignition tables and you might need to run it in open loop at idle. If you don't know how to do any of this tuning then give Rich at FAST Man EFI a call and he'll set you up with a tune.
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Re: Low Vacuum on Holley Sniper EFi
[Re: AndyF]
#2961908
09/07/21 03:43 PM
09/07/21 03:43 PM
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Joined: Aug 2008
Posts: 941 Texas, USA
ChrgrCuda
super stock
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super stock
Joined: Aug 2008
Posts: 941
Texas, USA
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My 512 RB with Solid Roller has about 8 inches of vacuum and it runs awesome with the Sniper.
68 Cuda Notchback [Email]10.86@120[/Email]
69 Charger R/T 440/505
2009 Challenger SRT8
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Re: Low Vacuum on Holley Sniper EFi
[Re: 70RT Charger]
#2961982
09/07/21 07:40 PM
09/07/21 07:40 PM
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Joined: Jan 2003
Posts: 31,082 Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,082
Oregon
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Is there anybody running a Sniper that has low vacuum with good results? My Comp cam is a XR-286-HR producing 8 hg at the Intake and 7-8 hg at the carb at 900 RPM idle. Are you controlling timing with the Sniper? If not you should be. If you are then throw a lot of idle timing at the engine. Start at 25 degrees and then test 28 and 30 to see how it responds. Watch the MAP and IAC values as you change the timing since those two numbers will show you if the engine is getting happier.
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Re: Low Vacuum on Holley Sniper EFi
[Re: 70RT Charger]
#2962024
09/07/21 09:38 PM
09/07/21 09:38 PM
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Joined: May 2004
Posts: 12,418 Taxes & Virus's R-US, NY
Dragula
I Live Here
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I Live Here
Joined: May 2004
Posts: 12,418
Taxes & Virus's R-US, NY
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Running a Sniper 4500 here....Raise your idle to 950....And yes. My Cam might scare you....and maybe add idle timing....
Last edited by Dragula; 09/07/21 09:41 PM.
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Re: Low Vacuum on Holley Sniper EFi
[Re: fastmark]
#2962123
09/08/21 11:18 AM
09/08/21 11:18 AM
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Joined: Jan 2003
Posts: 31,082 Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,082
Oregon
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I have a friend who fought his Sniper with a big cam for quite awhile. He called Rich and he helped him fix the problem. . He said he wished he would have done that from the beginning. Yeah it only takes a few minutes for a pro to dial in a big cam tune on a Sniper so it is a good investment. Holley kind screws up the deal by telling people that a laptop is not required to tune a Sniper. That is true if you have a stock 350 chevy, but it isn't true if you have a big engine, or a big engine with a big cam. When you have a big cam you have to use a laptop to tune the spark and fuel tables. Good news is that it only takes a few keystrokes to fix the tune, bad news is that Holley doesn't provide any instructions. There are a few videos on youtube that kind of show part of the process but nothing very professional. Just guys in their backyards taking shaky videos with their cell phones. Someone like Rich can dial in a tune in 15 or 20 minutes.
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Re: Low Vacuum on Holley Sniper EFi
[Re: 70RT Charger]
#2962532
09/09/21 03:56 PM
09/09/21 03:56 PM
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Joined: Oct 2007
Posts: 4,213 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,213
New York
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100 years ago, I got a Holley "tech" person n the phone ($$$) about the new EFI system. I asked where the input for engine vacuum was, what was the range of A:F, Hg" adjustments, etc. He had no idea what I was talking about, even enough to say "there isn't one". No, I didn't buy one.
Boffin Emeritus
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