What Valve Float looks like?

[Ranger6202]

Was curious to how you would know if you have valve float by looking at a tune or scanner. I've dialed in my turbo'd Vmaxx pretty well, but after 4800 my VE table goes flat. My WB's actually tell me to pull a little more fuel past 4800 by about 5%. My guess is: being the motor is completely stock, could be valve float; Or my turbo exhaust housing is too small and that's the RPM it really chokes the flow. FYI, both banks flow into one turbo and i'm at about 8#'s of boost at 6200 ft elevation, boost stays steady (via MAP) to 5600 RPM.

Float.jpg

[GHuggins]

Older engines did have a weakish valve train, so I could see boost aiding in unseating the valves. Valve float typically will show in torque delivered or on a dyno graph. Dyno will look very jagged right before it starts, then power nose dives. BUT if your experiancing float, you should notice it with how the motor pulls - You'll hold it floored out and she'll just barely gain speed if it's bad enough, especially in the higher rpms.

Turbos require very precise timing to be 100%. Rather advanced in the 85 to 100kpa 3000rpm to 4500rpm range. Then dialed in withen a degree in the 100+kpa areas. Most times you have to "tune" the knock parameters to where it's seeing actual knock for all this to work too. For that you pretty much need a dyno, but I guess if you had an airport runway or something like that wasn't being used where you could run back and forth in 3rd or 4th gear, you could dial it in that way. BUT that would be a pain.

Then of course it's very well possible that you do indeed have something "choking" your system. You could install backpressure gauges at different points and see if you have a muffler or other "like" exhaust restriction problems.

Just some thoughts...

[Ranger6202]

went to the dyno today, 473.8 HP and 557.5 ftlbs (mustang dyno). Here's the graph, can you see some of the "jagged" change you have seen before? The graph kinda sucks since they didn't slide the graph up to see what the torque curve does outside the chart.

MDGraph-2015-06-03-10-50-45.JPG

[GHuggins]

A little right there around 4700, but still couldn't confirm it 100% to be float. It does dive afterwords, but again, this may just be typical for your setup... AND if your dyno graph is smoothed it's full amount or not will make a difference. If it's smoothed fully, jagged and nose diving while maintaining boost into those rpms, then I would look into it.

I've attached a pic of our LS3 Twin Turbo Vette. It's not the latest Dyno Tune. Puts down a little more now, especially down low - it's increased 30 or so hp down there. BUT this is with graph smoothing completely off to show full detail of the pull. It's got a little jaggedness to it, but not much. AND it doesn't nose dive... Just to demonstrate that jaggedness doesn't necessarily mean float.

[SultanHassanMasTuning]

torque would indicate the issue, but the graph looks ok. maybe no smoothing has been applied or the tire tread is giving off a bad graph

[Ranger6202]

I don't think any smoothing was applied. The guys that did it, weren't the most familiar on their own equipment. Hell i had to show them how to navigate around their program and export the files onto my usb since their damn printer wouldn't work. After doing some more reading on how to setup a mustang dyno, i wouldn't be surprised if they had the weight of my truck wrong in the dyno data. From what i read last night, the few bits of data you put in the dyno program can change how the dyno calculates the output and adjusts the load quite a bit. It was my first time using a dyno, so it was beneficial to get that monkey off my back and at least have an idea what to expect next time.

GHuggins....you're right, pressure sensor looking at back pressure would tell me a lot. I did order a pressure sensor last week, so i'll probably be pulling the manifold here in the next month to weld in a bung and route some stainless tubing. Thought i would ask ya'll what you've seen in your travels that might lead me down the right fork to determine which is the culprit. I'm not terribly worried as this is my daily driver, that i don't race. But i have friends bringing me their crap all the time and its something i wanted to learn from and be able to identify in the future.

A few more questions with my setup: above 68 MPH my MPG has gone to hell. I use to run about 15 - 16 mpg and now i'm about 12-14 mpg. Everything else below that is still normal. That was my other bit of data that leaned me to thinking my turbo exhaust housing was choking my flow. I do start rolling into boost at about 2200, which on the interstate at 75 i'm running about 2500, thus boosting all over depending on the terrain. So whether i'm choking exhaust or not, if i were to go up a size....say a .81 or .96 (don't remember what i currently have), i should shift my boost range up a few hundred RPM. Hopefully getting me out of boost while cruising with low pedal at 2500 rpm. Am i right with my thinking? I had a friend tell me i just need to change my exhaust turbine profile altogether. But i was hoping the housing would slow the velocity down enough on the low end to shift me up, but still keep the full rpm range this turbine has.

[GHuggins]

I'll be honest... 65 to 70mph with rpms around 2100 to 2200 is where I used to notice valve float the most (especially) if you by chance have adjustable preload roller rockers that are set with too much preload. That's if you by at all possible chance have adjustable rr's. Oil pressure would increase durring cruise and then the valves would hang open slightly. Was a big bog when you would floor it out. BUT if the truck in your ID is the one with the motor, then the size of that truck alone would be a load

Shouldn't be burning more fuel with turbos vs NA. Turbo's usually increase fuel economy even with their more fuel demand at the same rpms due to the pumping efficiency increase on the motor. Hince why your seeing all of these smaller motors coming from the OE with turbos now....

Mind posting your stock and modded tune?

Finally, don't know if you are or not, but you don't have to run a flat line for PE. Better to run around a 13:1 AF for tip in enrichment, then hit full 11.5:1ish or full PE around 2500 or so rpms or atleast where you know your turbo is starting to build around 2 or 3 lbs boost. If your running a custom OS, you can use boost enrichment for safety boost spikes and set it to full PE at the 2 to 3 lbs boost.

Hope this helps a little.

[Ranger6202]

Yeah, i don't flatline my PE, only me BE. I'll post the tune. This is the one i used on the dyno. So the timing was about 2 degrees higher than i normally run cruising around.

The more i think about it and ask around, i'm leaning more towards my exhaust having a choke point. If you look at my VE table, it flatlines at 4700 RPM. I'll post the log of my dyno run, and you'll see that my manifold pressure doesn't dive off at that point, it maintains. Which i'm thinking is because i've lost airflow velocity due to the exhaust back pressure. I'll keep pressure at the manifold due to the turbo, but i've lost velocity. So either i need to increase my wastegate size, or wastegate piping, or the exhaust housing altogether.......just some thoughts. Easy fix would be to put the pressure transmitter in on my back pressure side and see if it ever exceeds my boost pressure. And i could just buy some ls6 springs and swap them out too.

If i remember right, there was three pulls on this scan.

THE BAT VE Tune -21 NO TQ MNGMT.hpt
turbo ve tune 20 dyno 2.hpl