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Flat Torque Curve


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I just got my 93 octane SS-18GXR tuned and the car drives great but the dyno plot doesn't have the typical peak torque curve I am used to seeing. It almost seems lower but flatter? Is this just a difference in tuning style or something with my setup?


Also, the first plot Rev_7 had a lot higher boost down low but for my final revision he backed it back down. My tuner mentioned that with my wastegate being so touchy down low it was better safe than sorry and backed it down. I am assuming he then increased the timing because they look pretty close on the graph?


Current relevant mods are,

  • PP&C Manifolds, GS X-Over, and GS UP
  • SS-18GXR with TD06SL2
  • Perrin TMIC
  • KS-Tech 73mm and Perrin Turbo Inlet
  • Grimmspeed EBCS
  • TGV Deletes
  • ID-1000's
  • TBE wirh Perrin Cans


Any input would be appreciated. Also, the plot has a smoothing of 4 and is NOT SAE corrected, it has been really cold here.


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I actually like to use a smoothing of around 3 or 4. The 1 setting can show spikes. Overall, I don't see anything to be alarmed at.


There's a lot of parameters that don't necessarily need to be logged, and I don't see manifold relative pressure in the datalogs provided. Boost seems a little inconsistent near its peak rpm so that might be smoothed out a little. I also notice from your plot that after boost spikes and dips, it creeps back up through the RPM range. Maybe that's how your tuner wants it, but usually there's a couple psi or so of taper. Ask him about that. I don't see it as a huge problem since it seems to be running healthy otherwise, but I'm no expert.


I would question why your fuel pump duty cycle % is at 100%, however. Your AFRs aren't leaning out at all, though.


If you are happy and it drives wel and it doesn't blow upl, that's what matters. As for your setup, what kind of boost control are you running?

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I appreciate the feedback. I am definitely confident the tune is safe and great but was just curious on the flat torque curve. I am curious why do you not see it very often and is there a direct cause of it? Benefits/Downsides to it?


The the only manifold pressure logged is absolute so i have just been taking 14.7 away and calling that close enough for my curiosity. I am using the Grimmspeed EBCS and the boost climbs due to boost creep. With the wastegate wide open i can still build boost in the upper RPM range. My tuner said he could tune around it because i don't have the funds to cough up a EWG right now.

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I suspect your boost could come on harder and faster but you would have to consult with your tuner on that. My suspicion is based on the fact that between 2-4 KRPM your WGDC is dialed in to less than 20%.


BTW, that's a really horrible logging interval. 343 ms per row sucks. What are you using to log, Tactrix cable with SD card? I think there's a way to enable quicker logging.

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hahhahaha....Logging with a SD card, I like that. I'm using a Dell 6430 with ECU Tek Delta Dash.


Ok, so it sounds like more of a safety thing then? That was my fist thought but then when i compared my Rev7 to Rev8 logs the Rev7 with 21psi boost plots really close to the same as my Rev8 with 17psi?


Could it just be a difference in tuning style where one would prefer torque across a broader range vs a greater torque in a narrow band? Or maybe my boost creep keeping it up?

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I wasn't joking about logging with an SD card. New Tactrix cables can do that very well.


If your turbo is capable of producing boost quicker and sooner down low, there isn't a performance reason for why your tuner doesn't have it engage faster. So again, I suggest you ask him about it. It could be for safety reasons (less shock on drivetrain maybe). You'll really have to ask him.

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OK....talked to my tuner and he said that he prefers to not peak boost down low for consistency and it also alows him to run things more aggressive in the upper RPM's creating the flat torge curve. Car runs great and I am extremely happy the way it turned out, thanks for the feedback.
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Does no one else think the afr curve is a bit messed up. Unless he's starting the log whilst already WOT, which the boost curve indicates otherwise, isn't it way off what it should be.

Not high enough when he starts and all over the place for the rest of the pulls. Does it go back up to 14.7ish when casually driving?

Sure the stock sensors aren't perfect but they generally are better than that, also i was under the impression they cannot read below 11. So could there be something not quite right with it leading to these strange results.

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