07-24-2007, 12:25 PM #1
Help 07 Sc Wake Rpm Drop While Surging
I have been fighting this for about three weeks now. The ski has 38hrs. on it. Mods are RR sc impeller,Jerry's washers, 158 thermo, 4" intake, SS wear ring,14/17r, Riva catch can, 3) 4" flo-rites up front replacing storage bin, 1) 2.5" flo-rite opossite gas filler, 4) 2" flo-rites at rear. Change oil between 10 and 15 hours.
When take off it will run hard to 8000 - 8100 then start dropping off and surging down to around 6900. At times it will jump like it wants run normal.
If I stop and idle for 30 sec. to a minute and take off again it does the same thing. Leaves hard and runs up to over 8000 and starts dropping off again. It appears to be something affected by heat or not getting rid of enough air.
Things I have done-
1)Inspected sc to tb hose for holes and reclamped tight.
2)S/C clutch slip is 125 in. lbs. pulled it last night for the second time and still at 125 in lbs.
3) installed new plugs (stock ngk)
4)Installed fuel pressure gauge- stays at 58lbs. all the time.
5)Pulled stock IC pluged and air tested in a bucket of water with press. reg. at 60lbs. did not see any bubbles. Pulled it a second time and tested with water hose. Both times I pulled it there was drops of water all over it and drops in the intake. Do they condesate that much?
6)Swaped coils with a buddy same chit nothing changed.
7)Ran it until it was surging real bad pulled the key right before the ramp, coasted on the trailer, took it up to the house and pull the plugs to see if one was wet or fouled. One was a little darker at the ring at the end of the threads than th rest.The insulators looked more white than tan like it might be a little lean.
Run with seat off and seems to do a little better but still does it.
9)Pulled the pump and impeller has been rubbing wear ring but still spins freely. Don't know what its doing under load. I will pull it again tonight and remove the impeller and clean it up with a flap wheel.
10)I have removed the exit tube on the water box and looked in there with a flashlight. Did not see the baffle or anything. I have not actually removed the waterbox to see if the baffle has come loose.
Things I wonder about is if the intake could be cracked and loosing boost. It idles fine though. Right at 1800.I am going to install a boost gauge. When the rpm's drop the boost will drop so won't it be hard to tell if you have a boost leak.
Please help with any suggestions guys.
07-24-2007, 01:00 PM #2
are you sure the gaskets on the intake are in place and not damaged?
be sure to silicone/grease your intercooler where it meets the intake.....
have you checked the throttle body gasket and tighness of the tb ?
i think you are on the right track with the cracked intake thing......
sounds like something is getting hot then expanding and causing a leak.....
just remember that when your r's go down so will the boost numbers....so you have to figure out which one is causing which
07-24-2007, 01:07 PM #3
- Join Date
- Jul 2005
- euxton nr chorley lancashire, england
07-24-2007, 01:15 PM #4
I greased the ic and it is a snug fit.
I have not checked compression and need to. I need an adapter for my gauge to reduce thread size.
It really does seem like it is loosing boost some how. If the intake was leaking you would think it would idle high or not good. I even looked around sc housing last night when I had it out to make sure it didn't blow some sealer out of the seem for a leak.
Thanks for the help DIGGS I will check gskts. tonight. I may spray them with something while idling and see if it changes.
07-24-2007, 01:18 PM #5
it is hard to diagnose something you cant see.... but i am sure someone will come up with the fix......this forum is the best i have ever been where people actually share and help people
07-24-2007, 01:18 PM #6
07-24-2007, 01:22 PM #7
07-24-2007, 01:23 PM #8
this is a long shot but......
07-24-2007, 01:33 PM #9
Battery connections are clean and tight but have not checked the other end of the cables and will do that.
This could be an electrical problem too because while it is acting up and surging it will jump for a second here and there like it wants to be normal.
When you are just riding at around 5000 rpm's you can feel it surge just barely.
10-06-2007, 11:14 PM #10
my buddies 2007 GTX Limited is doing this same exact thing !
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