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Free "boost cut"

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Old May 20, 2019 | 04:15 PM
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Default Free "boost cut"

Well its free if you have Hp tuners or efi live. I know some maybe of you are going to say its not a good idea to do this, but bear with me. Its does work, to and extent...so far...

I had posted a while back about adding a bunch of fuel past the boost that i'm safe with. Got mixed opinions. So I picked 12psi to be my max. I went right past that in my boost enrich table and added a bunch of fuel. And I've hit it a few times. Its feels like the engine loses a bunch of power for a second and I let off, quickly glancing at my wideband, seeing it was flashing 9.xx meaning its pig rich, and it hit like 15 psi. Why tho? Well my china wastegate failed on me and locked shut. Nice. That could have ended real bad. So theres reason 1 for me. Ive since replaced it with a Tial wastegate.
Second reason. I recently upgraded my down pipe to a much better flowing setup. Now I get even more boost by 1-1.5psi at peak. Well I hit it then too. I felt it and let off, saw 13.5psi. Ive passed my max boost a couple times while dialing in my boost controller, so I feel like its saved me. I guess if The boost were to go really really high and the fuel didnt drown it but actually matched the boost, well i'd notice a huge power increase and let off. I never try to be a hero....any little thing out the norm, I let off. What say you?
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Old May 20, 2019 | 05:12 PM
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From: Portlandia
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you can pull timing too via a NC hobbs switch put in line with the ground side of the IAT

above a certain psi, the opens and the IAT reads -38* F

go into that cell in the IAT timing table and pull whatever timing you want

I found that was a little safer than dumping unburnt fuel on a hot turbine wheel (although doesn't make as many cools sounds)
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Old May 20, 2019 | 05:36 PM
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Originally Posted by truckdoug
you can pull timing too via a NC hobbs switch put in line with the ground side of the IAT

above a certain psi, the opens and the IAT reads -38* F

go into that cell in the IAT timing table and pull whatever timing you want

I found that was a little safer than dumping unburnt fuel on a hot turbine wheel (although doesn't make as many cools sounds)
Not a bad idea!
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Old May 20, 2019 | 07:43 PM
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Yep, don't just add fuel. Pull timing, it's actually safer.
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Old May 21, 2019 | 02:13 AM
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If you are not using meth injection, cutting fuel is a better option. Everybody worries about going lean, but beyond a certain point you no longer have enough fuel to do any damage, no matter what your timing is set to. You really do need to have an extremely hard transition for this to work, though. Otherwise you could go lean with enough fuel to damage something.
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Old May 21, 2019 | 05:55 AM
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Originally Posted by gametech
If you are not using meth injection, cutting fuel is a better option. Everybody worries about going lean, but beyond a certain point you no longer have enough fuel to do any damage, no matter what your timing is set to. You really do need to have an extremely hard transition for this to work, though. Otherwise you could go lean with enough fuel to damage something.
Or you just pulling timing and there's no chance of detonation regardless of how much or little fuel or oil is in the chamber.
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Old May 21, 2019 | 10:22 AM
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Originally Posted by gametech
if you are not using meth injection, cutting fuel is a better option. Everybody worries about going lean, but beyond a certain point you no longer have enough fuel to do any damage, no matter what your timing is set to. You really do need to have an extremely hard transition for this to work, though. Otherwise you could go lean with enough fuel to damage something.
this is scary. I could set my 210 kpa line to all zero's, but my ***** aint big enough to do that. lol
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Old May 22, 2019 | 02:45 AM
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Originally Posted by ddnspider
Or you just pulling timing and there's no chance of detonation regardless of how much or little fuel or oil is in the chamber.
With enough overboost your timing has no effect on whether or not you have detonation. A good fuel air mix can easily diesel your motor into pieces with no spark at all if the effective compression ratio is too high.
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Old May 22, 2019 | 06:04 AM
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Originally Posted by gametech
With enough overboost your timing has no effect on whether or not you have detonation. A good fuel air mix can easily diesel your motor into pieces with no spark at all if the effective compression ratio is too high.
And comparing the odds, I'd much rather deal with dieseling cause the boost level would have to be stupid high with no spark to cause it, compared to trying to pull fuel and hope there was nothing in the chamber.
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Old May 22, 2019 | 08:27 AM
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Originally Posted by ddnspider
And comparing the odds, I'd much rather deal with dieseling cause the boost level would have to be stupid high with no spark to cause it, compared to trying to pull fuel and hope there was nothing in the chamber.
Yea I’m not brave enough to try cutting fuel. Because consider this. Say the mixture was rich right before the fuel pull and there’s some left. Pull fuel, little bit left ignites. Well you’ve got problems.

I do have overboost protection in my controller, which is great if I don’t have a wastegate malfunction. I mean usually that’s what causes a overboost mostly anyways (besides creep) and if a line pops off the wastegate, then you have no control either. At least if I dump fuel (and when I say dump fuel, I mean add enough to where is just pig rich but not flooded out) then it’ll alert me something is wrong.
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Old May 22, 2019 | 09:31 AM
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A fuel cut will work. I’ve hit my fuel cut rev limiter without damage enough to know that will work. For what you are trying to do I would go with ddnspider on this and tune for the correct afr under all conditions while pulling timing as a safety net.
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Old May 22, 2019 | 10:15 AM
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From: Little Austin
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Why not buy a better wastegate?

Andrew
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Old May 22, 2019 | 04:49 PM
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Originally Posted by Project GatTagO
Why not buy a better wastegate?

Andrew
I have a Tial MVR. Do I need to get something else? I thought those were good?
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Old May 22, 2019 | 04:53 PM
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Originally Posted by Project GatTagO
Why not buy a better wastegate?

Andrew
A cast unobtainium wastegate won't fix an install/hook up error.
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Old May 22, 2019 | 05:18 PM
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Originally Posted by ddnspider
A cast unobtainium wastegate won't fix an install/hook up error.
a better waste gate wont fix a blown off vaccum line to the wastegate.
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Old May 23, 2019 | 03:01 AM
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From: Stockbridge GA
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I got lucky once when a map sensor blew out of the intake at 10#s of boost, so I had fueling for 0 boost. The car just laid over with no damage. I'm sure if I had not let off as soon as it laid over something would have been damaged.
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Old May 23, 2019 | 07:38 AM
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Originally Posted by Kfxguy
a better waste gate wont fix a blown off vaccum line to the wastegate.
Exactly what I was going to say. The size of the wastegate don't mean you'll never have a boost spike. I had a reference line melt shut and if I had not had a safety setup for over boost, things could have been ugly.
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Old May 23, 2019 | 03:08 PM
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Originally Posted by ddnspider
A cast unobtainium wastegate won't fix an install/hook up error.
So don't install or hook it up wrong ?

It's kinda simple really.
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Old May 23, 2019 | 03:29 PM
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Originally Posted by stevieturbo
So don't install or hook it up wrong ?

It's kinda simple really.
Did you see the dude on here who literally installed the entire wastegate backwards??? Not everyone is perfect and stuff happens. That's the point of a fail safe.
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Old May 23, 2019 | 03:46 PM
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Originally Posted by ddnspider
Did you see the dude on here who literally installed the entire wastegate backwards??? Not everyone is perfect and stuff happens. That's the point of a fail safe.
Let's be fair though...the sort of person to do that...would probably set up any failsafe incorrectly too.
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