Chris bought his Ceffy from Japan already fitted with an S13 SR20DET. This has turned out to be quite a popular conversion in the drift world. It keeps the weight back to improve handling and the SR gives nice strong power without having to rev it to the moon.
When Chris approached me to do some tuning the SR already had a GT2510 turbo - as well as Z32 AFM and 550cc injectors. The ECU had a "mail order map" in it from a prominent local tuner. He'd been drifting the car like this so the tune obviously wasn't too bad.
He had decided to try the new 98 RON E10 fuel (from United Petroleum) in it and wanted it tuned to suit the ethanol blend fuel. I'd been involved with quite a few E10 tunes at this stage so i was keen to tune Chris's car.
It responded very favourably to the E10. I was able to crank in ludicrous amounts of IGN timing and the SR just lapped it up. From the figures I usually use on an SR running 16psi I added timing in 2 degree increments. It was making an extra 5rwkw for every 2 degrees! This happened 4 times before showing any signs of backing off! Resulting in a gain of around 17rwkw once a safety factor was added. This car is not registered - it's only used for track work so the tune needs to be safe.
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| 98 RON petrol vs E10 tune |
Chris then proceeded to the track with the car in this state of tune. The little GT2510 gives very snappy boost response and Chris is keen to keep it this way. As you can see by the graph, it makes full boost at 3300rpm.
I mentioned to Chris that E85 was now locally available (at very limited outlets here in SA) and it wasn't long before he was booked in for another tune. The Ceffy arrived with a belly full of E85 (Chris was beaming as it only cost him $1.35 per litre - at a time when premium unleaded was around $1.55!). As the car rolled in it was followed by a waft of sweet smelling burnt ethanol. Mmmmmmm...
I was more than a little apprehensive about sticking with the 550cc injectors as E85 (being mostly alcohol) needs quite a bit more fuel (30 to 40%) to achieve a safe AFR. Stoichiometric is 14.7:1 for petrol but 9.76:1 for E85. So if you work in AFR a safe number is around 8.2:1 for E85. As opposed to around 12:1 for petrol.
I had to add 40% to the injection multiplier value in NIStune to bring things into line. I was expecting the little 550's to start leaning out up top but to my surprise they held up. Just. What really surprised me is what a forgiving fuel E85 is to tune with. I added a more timing over E10 but not a huge amount - it just wasn't responding to more. So I left it safe. Same with mixtures - power didn't vary much when I went richer or leaner.
Because E85 is such a terrific knock suppressant we decided to turn the boost up a bit more. It was running 16psi before. Normally I wouldn't be keen on adding boost with such a small turbo - that little 60mm compressor wheel will be outside its efficiency zone and inlet air temps will go through the roof. Leading, of course to detonation. But with E85 it's not such a big deal. We didn't get far though - like most small turbo, they'll make more boost early in the rev range but run out of puff up top. So no matter how much was dialled in, it always dropped off to 17psi up top.
The bottom line was that with a bit of extra timing and an extra 1psi of boost it just hit 230rwkw. Pretty impressive for such a tiny turbo! Check out the graph below and you'll see a pretty decent improvement across the range. Note that the SR really responded to extra timing up top and it continued to pull hard to over 7000 instead of dropping off at 6500.
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| E10 tune vs E85 tune |
To anybody else considering a similar setup I'd highly recommend using 740cc injectors rather than 550's. We got away with it but the 550's were totally maxxed out.
Big thanks to the ever helpful Simon at Morpowa in Modbury North, SA.