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Here are the results from a run on a mustang dyno. I'm looking for input on why my torque could dive like this. I make good torque down low but then it turns into a turd right were it should be making peak power.
TVS 2.9" Pulley with OD Crank pulley (2.8" effective), lsj TB, Water/meth injection (2X-3gph nozzles), dual pass, opt. B, Phenolic spacer, ZZP LSJ S2 Blower cams, 82# valve springs + titanium retainers, exhaust side gasket port matched, ZZP LT header, 3" back cat+resonator+muffler. AFR around 11.8-12. Boost held steady at 14-15psi, IAT2 temps peaked around 140F. Any ideas why my torque drops off fast and early?
Tuner got back to me and said everything looked good and to toss these dyno results out and have another go on a different dyno. He is thinking this dyno was "loaded" or too big of rollers or something. When I am flowing a certain amount of air, with a constant AFR and drivetrain loss, I should be predictably putting down a certain amount of power and the log/observed reality does not match up with this dyno curve. So for the time being anyway I don't think my car is the problem. I will know more in time.
I've had this damn car for 10 years now. It's not going anywhere. It's worthless as far as sale price. I may go standalone at some point and/or goblin. #neverSS
You are really flat on top.
The dyno operator needs to shut down after HP starts dropping off. No need to keep pushing the engine like that.
Yeah I know and he knows. That is where I am supposed to be making peak HP is right where it turns into a turd. We did not know this was going to happen and if you don't rev the car out to the preset rpm on they dyno it screws up the data. I still don't know what is wrong yet but my torque curve shouldn't look anything like this.
Do you have GM adjustable cam gears and not have them installed at the stock setting for a baseline?
You're HP falls off just past 6000 rpm; way too early for the ZZP stage 2 blower cams.
What does the advance table look like? If it's not camshaft related, it looks like your commanding less and less timing as you go past 5200 RPM.
The red line dyno below is a 2.0 LSJ on stock cams/gears w/ a TVS 2.9 pulley and 75 lb springs.
His advance table used what I called a 4 column method. Not a technical term but any means.
All I mean by it is, if you looked at the high octane timing map.
The advance would slope upwards in steps of 4 columns using .5* increments.
Unfortunately his stock fuel pump on e85 didn't like the high RPM (squiggly line)
Do you have GM adjustable cam gears and not have them installed at the stock setting for a baseline?
You're HP falls off just past 6000 rpm; way too early for the ZZP stage 2 blower cams.
What does the advance table look like? If it's not camshaft related, it looks like your commanding less and less timing as your roll past 5200 RPM.
The red line dyno below is a 2.0 LSJ on stock cams w/ a TVS 2.9 pulley and 75 lb springs.
I'll get a specific answer out of my tuner but he seemed to indicate that it held full timing throughout the pull. I do not have adjustable cam gears, they are fixed. The graph I posted was generated on a mustang dyno which "automatically" induces a specific amount of load throughout the pull. Dynojets typically do not induce a load it just measures how fast you can accelerate a heavy flywheel. There are dynojets where you can induce some load I guess so that you can more accurately simulate road conditions because you might have a really high HP car and they dynojet won't load up enough to even build full boost. But the mustang dyno does not have a heavy flywheel and does it's calculations based on an actual load cell and measures torque based on induced load. There is a possibility the guy running the dyno didn't set this up correctly or the "automatic" software didn't induce the right load or something like that though I don't know how likely that is.
Dyno operator did not datalog my car if that is what you are asking? I did a datalog on my computer and sent it to trifecta for them to look over.
That's the problem right there
There's no way if the temps are good and it's commanding timing properly it's losing power like that, unless your cam timing is off and it's losing effective compression or floating valves or something like that. Compression test numbers good? Go back to a larger pulley and see if it still falls off like that.
A Dyno is far more than a tool to measure HP but for what you could end up spending on tunes and dyno runs, I would just get an HP Tuner and learn how to use it.
Yeah guys trifecta is my only option until I embark on the standalone journey. And I'm not worried about the numbers. Hell that torque is a lot higher at lot lower rpm than I would expect. I just know my torque curve shouldn't even really be close to what I got. I got to looking at the graph yesterday close and am fairly convinced that it can't be right. Look at this video I did of some pulls where I rev the car out to 8k. Pay particular attention when I shift into third. Third gear pull starts at about 5,500 rpm and ends close to 8k. According to the dyno graph above I should be dropping 60% of my horsepower and 50% of my torque over 5,500-7,500. However if you watch the video there is no noticeable loss in power that I can tell. If I was dropping from 310hp, 275tq to 150hp and 100tq like the graph says you would think it would be pretty obvious and would feel like it is falling on it's face. Let me know what you guys think.
The easiest way to check a dyno run for graphing errors is the HP and Torque cross at exactly 5252 RPM..... yours does.
Mustang dyno measures torque and calculates hp. I never assumed that is where things went wrong. That's the simplest part of what mustang dyno software does. Where I think it got off was in rpm calibration or something in how it determines how much load/resistance to implement throughout the rpm range. Mustang dyno's vary load on the wheels based on at least vehicle weight and an aerodynamic factor. The dyno operator says it also makes automatic adjustments based on how much power it is putting down. So loading and or calibration is where I think things went haywire. I don't and never did think it got the formula for horsepower wrong. I don't even care about the numbers that torque curve just doesn't make sense. When I am driving hard I drive pretty much exclusively in that upper rpm range where according to the dyno graph I am making no torque. And I have never once, until this dyno, noticed that it felt down on power in the upper rpm rang. I think if my torque actually looked anything like that graph that there is no way I wouldn't feel that dip.
10-14-2017, 08:58 PM
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