First Dyno - Something weird happening...
First Dyno - Something weird happening... Well here is my dyno graph....
344.2hp/352.7tq Lid, cutout, free mods.
The HP dropped off dramatically everytime at WOT at about 5000-5600 rpms.. It stutters and then picks back up again. All that I can gather is that it is pulling Fuel and leaning out during that time. Why? I dunno. I bought the car used 3 weeks ago.. Only thing I've added is a Lid and it already had a cutout. When installing the lid I noticed the Free Mods had already been done. Those 3 mods are the only thing done to the car. My only guess is that the previous owner had the computer programmed. Everyone said those numbers were really good for my mods and being an auto.
Someone PLEASE HELP!! Tell me what is going on so I can get that fixed!!
344.2hp/352.7tq Lid, cutout, free mods.
The HP dropped off dramatically everytime at WOT at about 5000-5600 rpms.. It stutters and then picks back up again. All that I can gather is that it is pulling Fuel and leaning out during that time. Why? I dunno. I bought the car used 3 weeks ago.. Only thing I've added is a Lid and it already had a cutout. When installing the lid I noticed the Free Mods had already been done. Those 3 mods are the only thing done to the car. My only guess is that the previous owner had the computer programmed. Everyone said those numbers were really good for my mods and being an auto.
Someone PLEASE HELP!! Tell me what is going on so I can get that fixed!!
He went really lean( hptuners said like hight 800's which isnt too bad but i think it was lean) and dropped from 25* timing to 22 with a good bit of knock.... this is non wideband.
Dunno what caused the lean spot tho...it wasnt pulling any fuel ltft were 0's
Have you ever seen an A4 w/ mods dyno this high?
Dunno what caused the lean spot tho...it wasnt pulling any fuel ltft were 0's
Have you ever seen an A4 w/ mods dyno this high?
my buddys bolt on ls1 had a very simular dyno graph...it would make good power at first then around 3800rmp to 4600rpm he'll drop 100rwhp and then it will start climbing back up ended up being colapsed valve springs.
hope that helps you
hope that helps you
are you sure that there isn't a cam in that car? I have never seen a stock cammed ls1 pull much past 6. All of the ones that I have seen start to fall off around 5700-5800. I am by no means an expert, just what I have seen. Do you have an air/fuel chart to go along with the dyno?
Originally Posted by obrien24
are you sure that there isn't a cam in that car? I have never seen a stock cammed ls1 pull much past 6. All of the ones that I have seen start to fall off around 5700-5800. I am by no means an expert, just what I have seen. Do you have an air/fuel chart to go along with the dyno?
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Verdad Gallardo i'm telling you guys my buddy had a graph that look exactly like that. Is it m6 car? This is the full story.
He was street racing and instead of putting the car in 4th he shifted into 2nd from 3rd. Bend pushrods, local dealership fixes the car by installing new pushrods the car sounded and ran normal. He kept modding, longtubes, catback no cats, lid, 12 bolt, drag radials car never went faster then 12.8@110mph so we thought that was wierd decided to dyno. Came to find out same exact graph. Someone told him that they read a post on ls1.com about same problem and ended up being the valve springs. sure enough most of them were calapsed and 2 were broken.
He was street racing and instead of putting the car in 4th he shifted into 2nd from 3rd. Bend pushrods, local dealership fixes the car by installing new pushrods the car sounded and ran normal. He kept modding, longtubes, catback no cats, lid, 12 bolt, drag radials car never went faster then 12.8@110mph so we thought that was wierd decided to dyno. Came to find out same exact graph. Someone told him that they read a post on ls1.com about same problem and ended up being the valve springs. sure enough most of them were calapsed and 2 were broken.
Originally Posted by DarknessZ28
It's an Auto. Why would a broken valve spring cause that to happen only at a certain rpm?
Originally Posted by LittleRedZ
i could only guess valve float but that should be up top, but like i said its a very good friend of mine and thats exactly what happend, i'm not saying he said she said type deal this really happend and i have seen the graphs they looked VERY simular to yours, just trying to help man you can either belive it or not
just dont look like anyone is trying to help you. been in that situation before can be very frusturating indeed. try posting in ls1 engine section and also ls1.com if you havent tried already
good luck bro
good luck bro
TECH Fanatic
Joined: Jan 2002
Posts: 1,205
Likes: 0
From: harrisburg, pa
You need to start from scratch...
what do the plugs look like? Do you know how to read them?
Change the fuel filter...check fuel pressure...do the basics
How many miles on the O2's?
Any codes?
Can you put the stock tune in?
My guess its knock and your car is pulling the timing out. You need to get on a wideband.
what do the plugs look like? Do you know how to read them?
Change the fuel filter...check fuel pressure...do the basics
How many miles on the O2's?
Any codes?
Can you put the stock tune in?
My guess its knock and your car is pulling the timing out. You need to get on a wideband.
TECH Enthusiast
Joined: Sep 2004
Posts: 564
Likes: 0
From: Omaha, NE
My guess also is that it is a valve spring problem. A weak or broken spring can go into a harmmonic/resonant frequency causing a missfire at only a given RPM range. By monitoring each bank with an O2, preferably wide band, you should see one bank go lean while this is happening. This will help narrow down which valve cover to pull for inspection. If you do have a non stock cam but stock springs could explains this problem. I agree with a previous post that your power band is high in the RPM and power for a stock cammed engine.
EJ
EJ
Originally Posted by dynocar
My guess also is that it is a valve spring problem. A weak or broken spring can go into a harmmonic/resonant frequency causing a missfire at only a given RPM range. By monitoring each bank with an O2, preferably wide band, you should see one bank go lean while this is happening. This will help narrow down which valve cover to pull for inspection. If you do have a non stock cam but stock springs could explains this problem. I agree with a previous post that your power band is high in the RPM and power for a stock cammed engine.
EJ
EJ
thank you