Project S2000: Part 35 –Dyno Tuning, Finding Problems, Retuning, and Math

Plotting the same points on the G25-550 compressor map, this is actually the better match. I’d likely gain ~400rpm of spool and quicker transient response with no loss of power.

The transient response is pretty good as-is though. These plots show a pull in 2nd, 3rd, and 4th gears. On the shift from 2nd to 3rd, it took about 0.6 seconds from when I got back on the throttle to hit 10psi. On the shift from 3rd to 4th, the recovery time to 10psi was about 0.35 seconds.

There’s some room for improvement still on the boost response. In the Hondata KPro, there’s a functionality called ‘quick spool’ that maxes the boost solenoid duty cycle to hold the wastegate shut until the boost target is almost hit. It’s not as fancy as a PID controller in a stand-alone ECU, but it’s not bad. In the boost settings used on the dyno, the boost solenoid was only at 30% duty cycle during spool-up and that resulted in about 300rpm quicker spool-up compared to running a straight wastegate. Looking back at the first dyno session and comparing it to the second, the initial boost control settings from the first session were making 260tq at 4000rpm compared to the second session making only 250tq. Definitely more torque to be had at lower RPMs with adjusted boost solenoid duty cycle settings.

While I didn’t hit my initial torque and power targets of double stock at 8000rpm while being spooled up at 3500rpm, the car is still a blast to drive and it doesn’t suck anymore on the street. I did do double the torque and power up to 6000rpm and the torque curve is relatively flat. Keeping the torque curve relatively flat kept the feeling similar to how a stock S2000 pulls all the way to redline, but getting to redline way faster. I could run more boost in the mid-range to get a mountain of torque like Project STI, but the STI has WRC rally car roots and the S2000 does not. My original targets were just unrealistic given the constraints I put in for noise levels, emissions, and fuel type. I could get to my targets with two adjustments: E85 and wastegate dump. Based on my calculations, I’m wastegating ~35%. If I did an external dump, that would reduce the flow through the restrictive exhaust to ~65% of the current level. As an approximation, the pressure drop is roughly a function of mass flow squared. So 65% flow reduces the pressure drop to only ~42% of the current value which is a huge drop. I’m going to try out the ‘quick spool’ functionality soon. I’m going to take some data on how well my cold air duct works along with the intercooler efficiency too. I’ll take some data at stock wastegate boost levels too; the lower boost level and slower spool-up have been nice in the recent rainy weather.

It took help from all these companies to get the turbo portion of the project done! And about thirteen years.

Garrett Motion


ATP Turbo

Bell Intercoolers

Mahle North America



King Bearings

JE Pistons

ARP Bolts

Killer B Motorsport

WPC Treatment

HPS Performance Products

Advanced Clutch Technology

Blacktrax Performance 


Improved Racing

Dyme PSI


Eimer Engineering

Invest Cast Inc.


  1. Epic build! Always love your updates. Your attention to detail and penchant for data is an inspiration. Looking forward to hearing how the “quickspool” effects things.

    On a side note, I must say that I would love to see this thing with a full OE style valved* exhaust. Big pipes and cats, but giant mufflers and electronically controlled cutout! It would cost a human soul to do right but man that would just be the cherry on top of an already incredible build!

  2. I was confused for a bit on the boost curve shape until the mention of constant duty cycle came up – I may be spoiled by having worked with stuff natively designed for turbos and forgot that PID isn’t a given. Interesting results and gratifying even from here to see what it can do, I imagine it’s far moreso on your side of the screen.

  3. Flat torque from 3500 rpm to 8000 rpm in an f20c proves your diligence in designing the turbo system was worth the effort. great read!!!

    1. What I’d really like to see is this with G30-660 or 770, 0.83 A/R, on a track setup with wastegate dump and bigger exhaust. it should really flow well on the top-end.

      1. The G30 series makes me go sploosh. Once I’m done with my current turbo (Boostlab) I’ll look at the g series.

      2. Agreed but for a street car, making that much torque that low AND being quiet is nice.
        Can’t wait to read about it!!!

  4. With the extra manifold, maybe consider consulting with Artec Performance and see if they could work with the design? I’d love to see your manifold become more readily available (or might have to shoot you an email about it)

    Incredible build otherwise!

      1. It’s been a blast to watch it all come together I’ve been following it for years! Hoping to see an update with E85 added in one day
        I would love to see the design sold and other people trying different setups with it!

  5. Thought about testing the 0.92 A/R housing on the current setup and switching to a less restrictive exhaust ? That combined with some quickspool should wake up both the mid-range and top end. I’ve run up to 90% quickspool duty with larger turbos using the Honda-based ECU code. With this smaller turbo, you probably don’t need that much though. Try using quickspool pressure equal to wastegate pressure if targetting more than WG pressure or 1-2 psi under wastegate to prevent boost spikes.

    Some tuners map in quickspool in the WG duty table and don’t use the pre-set Hondata feature. This allows you to tailor quickspool to different target pressures (boost per gear for example)

    1. I’d go to G30-660 in 0.83AR before the G25-660 with 0.92. That G30 config would spool faster and make more power I think. I’m happy with the exhaust volume noise as it is, so no changing it. I’ve had some time to adjust the boost by gear and the settings for the quick boost. I’ll update in the next article but your recommendation of targeting around WG pressure is accurate. If you look at the screen shot of the boost settings in this article, you’ll see the targets are higher than achievable in the lower rpm range which is the alternative strategy you mentioned. I’m not sure if I like the quick spool yet, I need to get out in the canyons and see what the throttle/boost/torque modulation is like in the twisties.

  6. Are you just set on keeping the stock axle back exhaust section or would you consider making a nice system and perhaps including a resonator or two to keep things quiet and streetable without producing so much back pressure?

    1. I’m set on it to keep the stock/stealth appearance. I’ve been driving it a couple times a week and I honestly leave it on low boost/wastegate most of the time as most of my driving is on surface streets. I can still give it full throttle without spinning in second gear once the tires are warmed up.

  7. Hello Khiem, i do have some questions related with an article you did back in 2012. Can you kindly email me?



  8. Awesome project. LHT Performance did a similar build and they did a custom twin exit exhaust where side is opened via vacuum/boost for sufficient flow under larger boost settings, yet still quiet like stock-ish under normal throttle low speed etc. Check it out on youtube. Can’t wait for the next iteration!

    1. Yup, I catch their videos here and there. I’m impressed they got the internally gated turbo to fit, though they did have to compromise on the manifold design a bit. I figure a freer flowing rear exhaust section with larger diameter pipes and straight-thru mufflers would free up 20-30hp on this setup. And still be pretty quiet.

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