Motorgen - Automotive Events, Meets, Cruises and Forums - View Single Post - Highest vacuum/ top gear/ slowest speed survey.

enkeivette · 08-01-2008, 11:58 AM

I'm starting this thread to collect results. Drove the SRT4 last night, and I was surprised to find that it pulls highest vacuum at the lowest speed of 65mph in 5th gear, on flat road. Thought it would have been closer to 55 mph seeing as how it's a 4 cylinder. It pulled 10" at 60mph, 12" at 65mph, and 12" at 70mph. Meaning, 65mph would be the most economical speed to cruise at... if my theory about pumping loss is correct, and assuming the engine has enough power to develop highest cruising vacuum in the top gear.

List (To be edited):

Year / Vehicle / Slowest speed at highest vacuum in OD

2003 / SRT4 / 65mph

2006 / Mod Evo (E85) / 65mph

1996 / Mod Cobra (C SC) / 60mph

Feel free to add info and I'll add it to the list. Mods feel free to edit the list. Going to try this in my friends car that has a vacuum guage when we get a chance. His motor/trans setup was NA from the factory and has much higher gearing than the SRT, so I suspect his best will be around 50 - 55mph.

08-01-2008, 11:58 AM	#1
enkeivette Super Moderator Join Date: Dec 2007 Posts: 6,850 Tweet	Highest vacuum/ top gear/ slowest speed survey. I'm starting this thread to collect results. Drove the SRT4 last night, and I was surprised to find that it pulls highest vacuum at the lowest speed of 65mph in 5th gear, on flat road. Thought it would have been closer to 55 mph seeing as how it's a 4 cylinder. It pulled 10" at 60mph, 12" at 65mph, and 12" at 70mph. Meaning, 65mph would be the most economical speed to cruise at... if my theory about pumping loss is correct, and assuming the engine has enough power to develop highest cruising vacuum in the top gear. List (To be edited): Year / Vehicle / Slowest speed at highest vacuum in OD 2003 / SRT4 / 65mph 2006 / Mod Evo (E85) / 65mph 1996 / Mod Cobra (C SC) / 60mph Feel free to add info and I'll add it to the list. Mods feel free to edit the list. Going to try this in my friends car that has a vacuum guage when we get a chance. His motor/trans setup was NA from the factory and has much higher gearing than the SRT, so I suspect his best will be around 50 - 55mph. Last edited by enkeivette : 08-06-2008 at 12:03 PM.