Belt Slippage?
Thread Starter
Staging Lane
Joined: Aug 2005
Posts: 84
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From: H.E.B
Belt Slippage? Could belt slippage cause a 80 hp loss? One dyno pull said 547rwhp, Next said 460rwhp.... I dont know much about dynos but both shops are very professional. So iam a little concerned.. thanks joshb
TECH Resident
Joined: Jan 2004
Posts: 832
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From: Castro Valley, CA
Was one a Dynojet and the other a "Mustang Dyno"?
If you can post your graphs, that would help... but your first course of action should be to contact each shop and ask them for their explanation of the difference.
But to answer your question, yes, belt slippage could cause a loss in your observed HP.
If you can post your graphs, that would help... but your first course of action should be to contact each shop and ask them for their explanation of the difference.
But to answer your question, yes, belt slippage could cause a loss in your observed HP.
If you do not have one yet look into buying a new idler pulley . The stock idler is notorious for slipping when wide open . Katech makes a good replacement and either tsp or thundder I think makes one for about half the price . Maybe someone else can chime in on which sponsor has the economy idler replacement .
FormerVendor
Joined: Mar 2006
Posts: 1,540
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From: Hell AFB
How tight is your belt? 6rib, 8rib? If its a new belt then it will stretch the first couple of runs, we usualy make a pull, tighten it up and check it the next few pulls. The napa/gates belts are verry good.
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Thread Starter
Staging Lane
Joined: Aug 2005
Posts: 84
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From: H.E.B
its a 6rib set up, car has less than 800miles on it since build.. 1st dyno was a dynomax pulled 547@7lbs 2nd dyno was dynodynamics pulled 460@6lbs... as far as belt tension am not sure.. if i had to guess it is set to standards to pro charger has in place... please advise 2nd shop reported car was running perfect no fluxing in power or boost... Am going to leave shop names out of this because both shop are very professional and if it is a mistake am sure it is an innocent one!!! that they would both be willing to pay for.. please advise thanks josh
heres an easy question that would explain if u lost horsepower or if it was the dyno.... is ur car slower? if it is, then its the car, if it isnt then u first dynoed on a generous dynojet and then dynoed on a mustang dyno
On The Tree
Joined: Oct 2004
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Probably best to stick to one dyno if you can so you can measure the changes. Why did you dyno the car a second time? Did you make changes?
According to your numbers you ran 14% less boost on second run and again very roughly that equates to about 80hp and on the second run you ran with about 80hp less. You ran 7lbs vs. 6lbs of boost so it sort of makes sense on paper. I guess the question is why did you run less boost on second run.... you either have a leak or belt slip, boost should be consistent assuming you are running motor up to same rpm and you have not made any mods in between.
According to your numbers you ran 14% less boost on second run and again very roughly that equates to about 80hp and on the second run you ran with about 80hp less. You ran 7lbs vs. 6lbs of boost so it sort of makes sense on paper. I guess the question is why did you run less boost on second run.... you either have a leak or belt slip, boost should be consistent assuming you are running motor up to same rpm and you have not made any mods in between.
Thread Starter
Staging Lane
Joined: Aug 2005
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From: H.E.B
The second dyno was just for the hell of it!!! I am over seas so i dont drive it, but when i took delivery of the car it ran well lets just say it ran very strong, 2 days later when i left the counrty again it was running the same very strong.... The only drive time it gets is when my father starts it up and lets it run for about 30mins, then take it around the block to keep things lubed... The 2nd shop with the dyno dynamics said the car was running mean(good) so i don't know... if it is the dyno and not the car What Hp Number is more accurate Dynomax or dyno dynamics?Oh yeah we did not change boost or anything else 2nd dyno was for sh*ts and giggles guess the joke was on me!!!