boost falling off in high rpm why is this? - Ford Mustang Forum
 
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post #1 of 12 (permalink) Old 11-05-2012 Thread Starter
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boost falling off in high rpm why is this?

I'm running 15psi off boost on a 4 gear pull the boost falls off what the reasoning for this

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post #2 of 12 (permalink) Old 11-05-2012
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who installed it? Who tuned it? What fuel system do you have? What are the symptoms? Do you have a dyno chart? What is your A/F?...

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post #3 of 12 (permalink) Old 11-05-2012 Thread Starter
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Its got duel gt500 fuel pumps tuned buy high tech in minnesota. When I'm on the street if I go for a fourth gear pull the boost spikes to Max boost than if I watch it you can c that it falls back to like 13 psi from 15-17psi it is a small turbo a/f is around 11.5
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post #4 of 12 (permalink) Old 11-05-2012
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So you had your car on the dyno how long ago? I take it that this didn't happen on the dyno? If that turbo is too small, seems like it would loose the boost at the top. How small of a turbo?
post #5 of 12 (permalink) Old 11-05-2012 Thread Starter
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60 mm. 96ar its been awhile since its Been on a dyno
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post #6 of 12 (permalink) Old 11-05-2012
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Right what I am trying to get at is this: has your car changed as far as increasing your boost since you had it dyno'd? I mean it was at one point making the 15-17psi all the way through the RPMS's and not dropping off or did you change something and now it is doing this crap?
post #7 of 12 (permalink) Old 11-05-2012
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get it back to they dyno...one hour there will save you a ton of headaches...my Cobra was cutting out at 6000rpms, was easy to see the spark was weak...needed new set of plugs, voila, drove off happy
btw 15 psi is alot of boost, has the engine been built? You might have weak rings, weak valve seals...alot can go wrong on a boosted motor even when they are built...saw a turbo car as the shop this year, 4 times the engine had to be redone, including new heads the last time..kept dropping valve seats
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post #8 of 12 (permalink) Old 11-05-2012
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Quote:
Originally Posted by 2Manystangs View Post
get it back to they dyno...one hour there will save you a ton of headaches...
I would normally say do that, but I'm curious if this guy had the problem when it was on the dyno. If that's the case, taking it back to that dyno might not exactly solve his problems. Hell I just got done reading...well just read post #60 and you'll see my reasoning on my question : https://www.allfordmustangs.com/forum...e-start-4.html
post #9 of 12 (permalink) Old 11-05-2012
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On most motors boost will start to fall as the engine becomes more volumetrically efficient in the higher rpms and the power adder moves out of its range.
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Yeah from what i read that turbo stops at about 550rwhp. They make about 435/465 rwhp/rwtq at 8.5 psi so that would make sense it is loosing boost at the top. I referenced this article for my info : http://www.musclemustangfastfords.co...t/viewall.html

If 1 psi=20rwhp then from 430 to 550 is 120rwhp/20= 6psi difference. 8.5 +6=14.5psi for 550rwhp. Not that it's perfect math, but a general indicator.


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post #11 of 12 (permalink) Old 11-05-2012 Thread Starter
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Car was tuned at 12.5 psi and and it was still a little rich so I turned boost up alittle and thats were I'm seaing it fall off now
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Well then you have your answer. 60mm is maxed out IMO.


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