Tuning Du's Nissan S15 200SX with Full Flex E85

Posted by Johnny La on

I've had some customers ask me how NHB Automotive started and if I had any relationships to trak-life, and to confess I do! All the cars you see in the trak-life stable have been tuned by me, especially Phil's S15 Silvia - we will call that Patient 0. 

I thought I'll get a blog going to bring a bit of life into NHB Automotive, instead of it just being a boring e-Commerce site. I'll kick off this blog with a recent tuning adventure I had with one of their cars.

Du's S15

You might have seen this S15 200SX running rings around Wakefield Park, and there's a high chance of that too! This immaculate blue S15 200SX belongs to Du and he and his S15 200SX are both no stranger to Wakefield Park, some argue it's a bit too clean of a car to be racing. What's the point of having cake and not eating it too right?

Previously it has had some basic work done to it by Phuoc from Greaser Co to allow it to be relatively competitive around Wakefield Park - lapping an impressive 1 min 8 sec consistently with only 219kW (which is very quick for a car producing low power). The car at the time sported a set of Tein coil overs and some basic suspension arms to keep it planted to the ground, however nothing wild or over the top.

S15 Dyno E85

Back then, in the power department laid a stock motor and a stock ADM S15 turbo with all the supporting mods to run full flex E85. By running E85 the knock threshold was raised which allowed additional boost and timing to be added safely thus maximising the hot side to the point where I'm sure I was over spinning compressor/turbine. To keep things simple and allow a wider range of configuration, a Haltech Platinum Pro was chosen and installed to keep business up front and party at the back by protecting the motor with the usual boost, AFR and oil temperature strategies.

The car was running more than optimal, until this year when firstly the stock 6 speed gearbox was fed up with the extra torque and decided to implode, then once the gearbox was replaced the OEM head gasket failing a few months later - talk about going out with a bang!

Fast forward a few months v2.0 plans were decided on by the guys at trak-life and myself. Du, determined to keep the low down torque and driveability we carefully selected a few extra things to update and refresh on his S15, this included a few extra goodies such as:

  • A tidied up head (Supertech valve springs, valve stem seals, ARP studs)
  • Tomei Head Gasket
  • Tomei 258 Poncams (yes, not 256)
  • Garrett GTX2860R Gen 2 0.64 IWG
  • Alpha Omega RB Box Conversion Kit ($$$)
  • R34 GT-t 5 speed gearbox
  • Nismo 1.5 way GT LSD with 4.08 ratios

Off it went to John's Garage to get some surgery, once the car was ready I advised Du to fill up his car with 98RON so I could revisit and tidy up the existing fuel map - knowing with experience, breathing mods equals running lean. Straight away with the new setup, the motor was flowing more and more fuel was needed in most parts of the map.

S15 E85 new Setup Haltech

After two nights of street tuning, I started advised Du it was time to start blending in ethanol so I could readjust the compensation tables. Following that, a few more late night runs we had and then we were ready to strap the car to the dyno.

S15 GTX2860R Gen 2 Dyno Time

Friday night, tuning started with the usual load holding sessions, adding in fuel and timing as required to achieve MBT under the 4000rpm mark. During this time, it was a good idea to reset HKS EVC boost controller to suit the new waste gate actuator. These (overly complicated) boost controllers always require re-initiation  when the base pressure changes. Once all the pre-setup was complete I began with a power run on gate pressure, which in this case is 1 bar of boost. Straight away with very low timing figures in the 10~12 degree range, we achieved a healthy 208kW. Once the run was over, analysing the data showed us the mid range required more fuel, which confirms signs of well flowing engine.

S15 GTX2860R Gen 2 at 1bar

Changes to the fuel map were then made to flatten out the AFR, at 1 bar boost using gasoline scaling I was targeting 11.7:1 AFR, following that adding in a bit more timing I achieved a solid 221kW still the same boost and only 15 degrees of ignition timing at peak power.

S15 GTX2860R Gen 2 at 1.1bar

At this stage, running 1 bar of boost was already performing as well as the old setup at 1.3 bar of boost (if not better), this excited Du and I could see his face light up. I started to add in more boost, and continued tuning. Each time 0.1 bar was added, roughly an additional 10kW would appear with no signs of slowing down, at 1.3 bar the car was happily pushing out 253kW! At this stage, I was seeing the 270kW we were both targeting in sight.

S15 GTX2860R Gen 2 at 1.3bar

Then of course, this wouldn't be a true Nissan if there weren't any problems to be had. Nothing Nissan ever goes to plan! At 1.4 bar the fun police came and it was a misfire riot. With the spark plugs gap set at 0.8mm, spark was being blown out with the boost commanded. I tried to up the dwell timing valves on the Splitfire coil packs but at 3.2ms @ 14v it was getting a bit dangerous. The misfire seemed to be a bit less frequent - however runs could not be replicated smoothly so at this point we both agreed to leave the car as is for now until the ignition system got addressed.

S15 Dyno Sheet GTX2860R Gen 2

But there's always a happy ending to all the stories, and that is 252kW with 1.3 bar of boost with plenty of boost headroom to go. I definitely see  270kW+ in the horizon once the misfiring problem is sorted. We'll be definitely back for Round 2 and No Holding Back this time!



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