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6.0 S480 Combo low power and dropping off early. Help. Please.
Basic rundown of the setup:
Motor:
Rod and Piston Lq4 (.005)
Untouched 317's
BTR 660 Springs
Tick stage 3
LS7 lifters
LS1 Intake
Trans:
Glide
PTC converter
Rear:
9"
3.50 gear
28" tire
Fuel:
Bosch 210s
4303
82-84 Ethanol Content on the dyno
Turbo:
Cast S480
Flipped Truck manifolds
2.5 hotside
3" cold
4" by MAYBE 20" long downpipe out the bumper
Car is running an MS3 gold box.
And the problem... On street pull and the dyno the car spools as expected and then has a very noticeable nose over in the 5k-5.5k rpm range. You can see it on the dyno sheet here:
The 770 pull was on 23 PSI and 14deg. The 40X pull was on 5 psi. I really have no idea whats causing the power to drop off like it is. Plugs look great and are gapped at 18, I checked the pushrods and they are short by .045 (new ones on the way) Compression on 1 and 7 are 130 and all other cylinders are 120. I tried adding fuel, pulling fuel, swung the timing by 3 deg in each direction with no noticeable progress. Boost level holds solid within 1 psi once it comes in. Fuel pressure is 45psi base and raising 1 to 1 with boost and not dropping off. Car doesnt miss or pop during a pull but the power loss can be felt in the driver seat. Am i crazy or is 150 + hp drop to redline from 5500 not normal?
I'm no expert, but it almost looks like valve float. check the spring pressure since it has been broken in? This also could be the result of your pushrods being too short? Again, not an expert, just throwing my $.02 into the fountain.
3 Window: I would have to look at the log to be specific but the boost comes in around 5k and holds within 1 psi all the way to redline.
ls3 fox: I switched the chart over to MPH and checked some of the pulls, the 770 pull went to about 165 mph, there is no noticeable drop in MPH as the power level rises from pull to pull.
Red fury: Its a 1.32 AR 96mm
MY 2K Z : That had me worried but i was told by a few people the number is kinda BS and as long as they're within 20%ish of each other its not hurt. Is that information valid?
Valve float seems to be there general consensus, theyre are BTR 660 springs "dropped in" as suggested, no shims or anything. I'll be checking installed height and seat pressure over the weekend as well as the pushrod change.
I really doubt it's valve float. I'd check your gauge, or buy a new one. Maybe swap with a friend. But 120 is not normal for a 6.0. Should be 170-190 depending on elevation. Did you degree the cam? Sounds like it might be off. I had a 5.3 like this. Degree'd the cam with no other changes at the same boost and picked up 12mph. (it was installed "dot to dot" originally)
All that said I have similar issues with the last 3 LS turbo setups I've done. All used MS3 gold boxes and PTC converters. I've checked the valve springs, push-rod lengths, and my cranking compression is 'normal". I have also degree'd the cam in all of them. No idea what the deal is. Have you tired switching over to wasted spark? I was going to try that next track visit.
I had an ms3 gold box and swapped it for a Holley because every time I reved over 3000 rpm the box would stop logging and it even shut off on me one time at WOT around the 1000’ mark and I thought I hurt the motor. Tech support from the gold box just kept telling me I needed better grounds. I have the best grounded car on the planet now lol. Everything is isolated. Car went mid 6s and would probably go 9.99 if the gold box stayed connected. Swapped to the Holley and went 9.6 first pass on 14psi. Similar combo to yours: 6.0, ljms stage 2 cam, tfs as cast 220 heads, single VS racing s480. That’s with 1.5 60’ and still trying to figure out the suspension for best 60’. That being said your compression sounds low.
I've never had a unit skip a beat and have installed several and owned 4 now. Usually setup makes so much power down low that I'm not super concerned with the lack of RPM. But it has me curious now. I don't believe there's anythign wrong with the MS3 units. (at least none I've worked with) But there might be a setting that is off or needs adjusted. Not alot of big RPM guys using the MS3 I'm aware of, just throwing it out there as a possible issue. Have you tried putting it in wasted spark?
Tried wasted spark and fuel at track this weekend. Changed the tune a bit. Had to add alot of fuel. But did nothing for the lack of power at RPM or performance that I could tell. Have you locked timing and monitored ignition with a light at higher RPM to make sure it doesn’t wander?
I noticed in the ignition settings they mention something about ignition latency and retarding excessively with RPM. There is a field you can adjust to correct this. I haven’t had a chance to check it yet. It’s on the “to-do” list. Also found I had “80” in this field. But when I looked at a friend’s tune he has zero here and can rev well past 6k with no issues. No idea how this field was populated or why... or how long it’s been this way. Haven’t ran the car since.
This is just a screen shot form online, but it shows the field Im talking about.
Thanks for posting the results Forced. My latency is zero btw.
This is beginning to worry me now. My car was originally T56 and Turbo, no problems smacking the rev limiter at 6400rpm, even with my tiny turbine. Switched the car over to a TH400 and the car gains RPM well until ~5,500rpm then just hangs, I even lost RPM on one pull. I have been blaming it on the small turbine and it's known 5,500 fall off issue, but the OP has the turbo I would eventually move up to with a big juicy turbine on it.
So common denominators are Goldbox & PTC converters. I have searched enough to know PTC is the bomb when it comes to turbo converters, which is why I picked them. This leaves the Goldbox...so now I am wondering if there is indeed a setting somewhere that needs tweaking. The weird things is as I first mentioned, care did not do this with the T56, although I was at less boost which points back to the turbine.
Check your back pressure, it’s cheap and easy and likely fine.
I was told by PTC if you aren’t making the power you claim when the converter was spec’d... It will likely “hang” at a set point and never fully couple and gain RPM. (same deal with gearing) Might look at your converter specs and call up the PTC guys. They have always been great to me. They straight out told me my gearing and converter combo won’t work well and suggested I change it.
What I don’t understand is in 1st gear with my TH400 2.48 1st gear ratio It should have plenty of mechanical advantage to couple... It’s not like I’m at 1:1 gear ratio there handing the converter out. Yet RPM still hangs on both cars in 1st. I have a 1.80 first on the glide. Should easily carry out to 7k+ on the shift.
are you guys using the 9.5" or 10" converter from ptc? i run there 9.5" with a 1.80 glide and have no issues sending it to 7400 rpm but i run holley efi
One of each for me. They have different stators they install depending pn how they want it to act. So much more complicated than 9.5” or 10”. I have a 14 blade stator in my 9.5 now which is really tight. I had a 17 blade stator in it originally on my stockish 5.3 turbo build from them. I’d have to double check the 10”, but same deal there.
06-13-2018, 08:07 PM
6.0 S480 Combo low power and dropping off early. Help. Please. 
