Turbo Boost?
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Junior User
Joined: Feb 2012
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From: NW Oregon
Turbo Boost?
Hi All,
What's the max turbo boost you guys get under full throttle with a load? I finally got a 1,000 miles on the odometer and towed the 30' 5er for the first time today and only got around 20-22 psi boost up a 6% grade, WOT. I managed to get to 70mph but couldn't accelerate beyond that.
This normal? Boost gauge goes to 40psi, what's up with half of that?
Regards,
Doug
What's the max turbo boost you guys get under full throttle with a load? I finally got a 1,000 miles on the odometer and towed the 30' 5er for the first time today and only got around 20-22 psi boost up a 6% grade, WOT. I managed to get to 70mph but couldn't accelerate beyond that.
This normal? Boost gauge goes to 40psi, what's up with half of that?
Regards,
Doug
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Junior User
Joined: Feb 2012
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From: NW Oregon
There seems to be plenty of power on tap. I guess I was surprised that the boost flattened at 22 psi. Towing the 5r is a joy now compared to my former truck. Looking forward to first towing trip in a couple weeks.
Regards, Doug
Regards, Doug
Mountain Pass
Joined: May 2012
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From: Keller, TX
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Fleet Owner
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From: Wisconsin
In case anyone researches this, I'm going to post it here as well as in my DPF on tuning thread. You don't get the same amount of boost pressures with DPF on tuning as the guys that are deleted. I've seen 26-28 fairly often, but I've only seen 28psi+ when I'm REALLY getting into it and I've only seen 30psi once and I have the burnout to prove it.
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From: MA
VGT and wastegates complicate it somewhat, but in simple terms more fuel is more boost for most diesel engines, so once you use a tuner it goes up.
I see low 20s on my truck as well (stock). I like that the stock gauge has enough range to cover a pretty solid tune down the road.
I see low 20s on my truck as well (stock). I like that the stock gauge has enough range to cover a pretty solid tune down the road.
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Junior User
Joined: Feb 2012
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From: NW Oregon
20-23 psi just seems low for a 400hp engine, maybe not. I'll reserve judgement on the power of these engines until I get a few towing trips under my belt.
Another question - has anyone experienced a bit of shuddering when starting from a stop under load? I had this happen a few times and don't know if it's a concern or not. Once I got over 10-15 mph it went away.
Regards, Doug
Another question - has anyone experienced a bit of shuddering when starting from a stop under load? I had this happen a few times and don't know if it's a concern or not. Once I got over 10-15 mph it went away.
Regards, Doug
Lead Driver
Joined: Feb 2011
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From: Milford, MI
20-23 psi just seems low for a 400hp engine, maybe not. I'll reserve judgement on the power of these engines until I get a few towing trips under my belt.
Another question - has anyone experienced a bit of shuddering when starting from a stop under load? I had this happen a few times and don't know if it's a concern or not. Once I got over 10-15 mph it went away.
Regards, Doug
Another question - has anyone experienced a bit of shuddering when starting from a stop under load? I had this happen a few times and don't know if it's a concern or not. Once I got over 10-15 mph it went away.
Regards, Doug
Postmaster
Joined: Sep 2006
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From: Maryland
Why do people equate boost pressure with horsepower? High pressures do not always equal more power. The volume of air flowing is just as important as the pressure and sometimes high pressure is simply a result of a constrictive intake path.
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Joined: Aug 2009
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From: MA
Engine displacement is a big factor in boost required for a certain horsepower. Here's some quick math that ballparks the lower boost required with the bigger engine. IIRC, my 6 liter made about 26 psi to make 376/790 at the wheels.
-Divide 6 liters by 6.7 liters to get a ratio on the displacement change. .90
-Multiply 6 liter absolute pressure (26 plus 15) by that ratio to get 6.7 liter PSIa (41x0.90). 37 PSIa
-Subtract 15 psi to get back to gauge pressure (37-15). 22 PSIg.
There are other factors so this won't be exact, but displacement is a big one. The result looks pretty close to me, if my memory of the 26 psi is correct.
-Divide 6 liters by 6.7 liters to get a ratio on the displacement change. .90
-Multiply 6 liter absolute pressure (26 plus 15) by that ratio to get 6.7 liter PSIa (41x0.90). 37 PSIa
-Subtract 15 psi to get back to gauge pressure (37-15). 22 PSIg.
There are other factors so this won't be exact, but displacement is a big one. The result looks pretty close to me, if my memory of the 26 psi is correct.