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The Pac number will work perfect! I would check that, it should take .045 without issue. Next time you need springs I would step up the open pressure #400+. I use PAC 1207X or 1221X on hollow intake/titanium valve engines with .625-675 lift at valve. Shimmed for .050 from stack they will operate at 7500 on road course without issue. I use a fairly mild ramp which is helpful, but I would bet the 1207X would set up and work well in your car.
Kurt
Originally Posted by Forcefed86
So the “stack number” is the same as the coil bind? If this info was provided by PAC would I even need to do this step? (I’ll check anyway)
Pac says the bind is 1.096 +.050 +.612 = 1.758 So .042 worth of shim would get me within .050 of bind assuming 1.8 installed height? So my .030 shim would be about as close as I should get?
Shim tracking indicates “out for delivery” so I should be able to shim them .030 at least by Sundays event.
I could put the larger tire back on, but I won’t know if my issue resolved itself then? Hoping to run the 275 tire and squeak some more RPM out of this combo. Feel like it’s leaving a lot on the table only pulling 6200 thru the traps with the 30” tire/3.25 gear. Before this issue the plan was to drop a 3.40ish gear in and be around 6800ish at 161-162ish. Shooting for 8.5x with a 1.4ish 60’.
If it does the same thing, I’ll stop for the day. I’ll only be doing TNT. I don’t have a road I feel comfortable on over 150 close by or I’d go test it now with only the plug gap change.
I went to a chassis dyno to get some data for just that reason. At 7k rpm I figured i would have been going close to 175mph!
I hope you figure it all out. Been reading along and it sounded like valve float to me as well but enough people already mentioned that so.......
Also clamped the spring down completely to get the bind. Came up with 1.085 though I could still see air around some of the coils on one side, but the other side was completely compressed? Had it clamped level between to 1/4 thick alum pieces so not sure what that was about. Little short of the advertised 1.096 anyway.
The opposite side had no gaps on the coils and was completely bound.
Nearest I could tell the installed height was 1.78...
So 1.085+.050+.612=1.747 1.78-1.747= .033ish?
Anyway I shimmed it .030. If it was really this close and the spring pressures are good, it makes me think I shouldn't have had valve issues at 6k.
Anyway I shimmed it .030. If it was really this close and the spring pressures are good, it makes me think I shouldn't have had valve issues at 6k.
Looks like you measured ~131 lbs at your previous installed height, remeasure with .030 more preload and see what it goes up to. I don't think 131 is enough for your turbo/engine combo...
did you buy that load cell arduino or make it? thats sick!
Aknovaman on this board made me a set to get corner weights on my car. The cell was around $20. Think we had less than $50 in parts for the whole rig.
Originally Posted by NicD
Looks like you measured ~131 lbs at your previous installed height, remeasure with .030 more preload and see what it goes up to. I don't think 131 is enough for your turbo/engine combo...
131 was at 1.8". Which is what the spring advertises. I'll see what it looks like at 1.75" (which should be where I'm at with the shim and installed height). I've only done one side of the engine so far.
What kind of pressure do you think I need? They are advertising that as a .650 lift spring with 130/337 and I'm well under that with a mildish lobe, and around 6k is where I seem to be having troubles, but only in high gear. If I could get it to rev clean to 6500 in Hi-gear that would be more than enough RPM.
Here is the lobe info....
~thanks!
Last edited by Forcefed86; Oct 1, 2016 at 10:09 AM.
131 was at 1.8". Which is what the spring advertises. I'll see what it looks like at 1.75" (which should be where I'm at with the shim and installed height).
Ahh gotcha, I thought that was your measured installed height but yes remeasure at 1.75.
Originally Posted by Forcefed86
What kind of pressure do you think I need? They are advertising that as a .650 lift spring with 130/337 and I'm well under that with a mildish lobe, and around 6k is where I seem to be having troubles, but only in high gear. If I could get it to rev clean to 6500 in Hi-gear that would be more than enough RPM.
I would bet your seat pressure would need to be around 150+. Just remember that having pressure on the tops of the valves from the hotside/coldside ups your seat pressure requirements over that of a naturally aspirated setup. Advertised max lift doesn't mean anything except that's where coil bind is, you need to shim it appropriately to get good seat pressure for the combo while avoiding coil bind.
Nice spring pressure setup! Curious to see what your pressures were at with previous installed height of 1.780" and 1.170 and new spring pressure at the shimmed height of 1.750" and 1.138".
86, As a baseline, did you happen to measure the orig 1.780" and 1.170" pressures? I won't be surprised to see some nice improvements with the .030" shims based on springs pressures. If needed, a dual spring would further manage spring control/oscillations as compared to the single bee hive. Just a thought.
That is a great idea. Want to make another one and sell it to me? You said you made a setup for getting corner weights too? I'm in! I've been on the lookout for a set of used scales, but they are few and far between at bargain prices.
I'm with you, it doesn't look like you should have had an issue with valve float.
This is some great tech, thanks for all the info Kurt, I'm going to pull a spring on my car and check things out, I think mine is way off, 1.010 coil bind +.0.050+ .621 lift = 1.681 minus 1.8 installed height (I'm going to check it) .119" which sounds like a lot and be part of the issues I'm having on higher boost
Didn't get the results I was hoping for. Made one pass at 20lbs. Made 17 lbs in first gear at 6800. Did the usual and nose dived around 6k. 9.2 @ 154 6200 rpm. Still way down on mph. Pulled into pits and car went nuts. AFR's dead lean, wouldn't idle. Added 40% fuel at idle/cruise just to limp it home. Plugs look great, no odd noise, oil pressure is good. Going to pull the push rods and make sure I didn't bend anything, assuming I'd hear it if I had.
Loaded an older tune and it fired right up and appears to run normal.
Stumped on this one, compared the tunes and there isn't much different aside from a few small VE map tweaks and timing/boos ramp tables. Electrical gremlin of some sort I spose. Another TNT next weekend I'll have to test it then.
Popped this plug in just before the run. Shows heat just into the first thread and about 3/4 of the plating around the top of the plug colored. Really don't think the tune is off... .019 plug gap with the shimmed springs didn't help. 128* IAT 36 psi peak back pressure.
Flash made the plug look dark for some reason, but you can see the heat just down into the 1st thread, 11.0 AFR
Last edited by Forcefed86; Oct 2, 2016 at 06:11 PM.
Fuel pump goin bad? Sucked up some garbage from the tank? Seems possible as there'd be enough to get you goin and trough first (which would be a rather short time in your case) then go into starvation mode. Think about it, ran horrible afterward, added a ton of fuel to limp it home........just thinkin out loud.
You are slowly fixing all the little things, bound to find the right one soon. Does anybody local have larger capacity turbo you can try? What engine control are you using?
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