There is a version of this article that opens with how much timing you can run once ethanol is in the tank. This is not that one, because in New Zealand the hard question is not what E85 does to an SR20 – that is well established – but whether you can get it into the tank consistently enough for the tune to survive.
What You Can Actually Buy At A New Zealand Pump
E85 Is Not On The Forecourt Anymore
Start with the disappointing bit. There is no E85 pump waiting for you in Hamilton, or anywhere else in the country. Gull ran a high-ethanol product for a while and it quietly went away, leaving Force 10 – a 98 octane petrol carrying up to 10 percent ethanol.
Useful fuel, but E10 is not E85, and an engine tuned for the latter runs frighteningly lean on the former.
Coverage matters as much as product. Gull is largely a North Island operation with a handful of South Island sites, so an Aucklander and a Southlander are having different conversations entirely. If your nearest station does not stock it, this stops being a fuel choice and becomes a logistics project.
Drums, Race Fuel And The Cost Of Doing It Properly
So where does the ethanol come from? Motorsport fuel suppliers, mostly. Drums of E85 or denatured ethanol move through the same channels that keep club racers and drag cars fed, and you either buy it pre-mixed or blend to a target percentage yourself. Expect to pay well above pump prices per litre.
Then there is storage. Drums need somewhere sealed, cool and clear of the ignition sources scattered around a working garage, and ethanol starts pulling water from the air the moment a lid sits loose. Buy what you will use in a few weeks rather than filling the shed.
The cost per kilowatt still stacks up. It is the inconvenience that kills most conversions inside a year.
The Fuel System Has To Change, Not Just The Tune
Lines, Seals And Filter Media
Ethanol is a solvent, and everything downstream of the tank on a thirty year old Nissan was specified for petrol. The soft rubber sections either side of the hard lines on an S13 go hard, then soft, then they weep. Injector O-rings and the fuel pump hanger seal follow the same path.
The fix is PTFE-lined hose with a stainless or nylon braid for anything you replace, and Viton seals wherever you can source the right size. Hose marked SAE 30R9 is acceptable on low pressure sections, but it is not a forever answer.
Filters deserve more attention than they get. Paper elements swell and shed. Move to a stainless mesh element in a serviceable housing, because the first few tanks will scour years of varnish out of the tank and deposit the lot in your filter.
Pumps And Injector Sizing
The stoichiometric ratio for E85 sits near 9.8 to 1 against petrol’s 14.7, and that single number drives every hardware decision after it. You need roughly 30 percent more fuel by mass for the same air, so a set of 550cc injectors that lived comfortably at 250kW on petrol is suddenly marginal.
Our rule of thumb is to size as though you are chasing 30 to 35 percent more power than you actually are, then confirm duty cycle on the dyno rather than trusting a calculator. It helps to know that pump blends labelled E85 are rarely 85 percent ethanol, so the target moves with what you poured in.
The pump gets the same scepticism. Flow figures on the box are quoted at low pressure and 13.5 volts, neither of which describes your car at full noise.
The Tank And The Bits People Forget
The tank itself is usually fine. Most Nissan tanks of that era are coated steel and cope well enough. The fittings inside are another matter – level sender resistors corrode, and the first symptom is a gauge that reads full right up until it does not.
The hanger seal, the sock on the pump pickup and the short hose between pump outlet and hard line are all original rubber on a car nobody has been inside for two decades.
While the tank is down, follow the vent and return lines along the chassis rail. On a Silvia that has lived near the coast in Napier, those are usually why this job takes a weekend instead of an afternoon.
Cold Starts And Corrosion In A Damp NZ Winter
Why A Dunedin Morning Is The Real Test
Ethanol does not vaporise readily when it is cold, which is why overseas markets blend more petrol into E85 through winter to lift vapour pressure. New Zealand runs no such programme, because there is no supply chain here to blend. Whatever sits in your drum in January is what sits in it come July.
That shows up as extended cranking on a five degree morning, and it worsens as ethanol content climbs. A car that fires instantly in Whangarei in February can take four or five seconds to catch in Dunedin in July on identical fuel.
Cold start enrichment tables need real attention rather than a base map copied off a forum. Reference coolant temperature as well as intake air, because the engine’s temperature decides how much of that fuel turns into vapour.
Water, Phase Separation And Cars That Sit
Ethanol is hygroscopic – it pulls moisture straight out of humid air, and we have no shortage of that. In a sealed system on a car that gets driven, this is a non-issue. In a project car sitting in a damp Christchurch garage over winter with a third of a tank, it is not.
Past a certain water content the mixture phase separates. Ethanol and water drop out as a layer in the bottom of the tank and the petrol floats above it. Your pump pickup sits in the bottom layer.
The practical answer is dull. Keep the tank full over layup, keep the cap sealed, and drive the car. A Nissan used every second weekend never meets this problem.
Why A Flex Fuel Sensor Beats A Fixed Tune Here
The Problem With Tuning For A Blend You Cannot Repeat
This is where the New Zealand situation bites hardest. Blend your own fuel from drums and the actual ethanol content shifts batch to batch, while a fixed E85 map assumes it never moves.
Fill on a batch that leans heavier on petrol and the engine runs lean against a map expecting nearly a third more fuel, carrying all the timing advance that ethanol’s knock resistance let you dial in. That combination is how pistons end up with holes in them.
You can build margin in by tuning conservatively for something like E70, which works but throws away most of the reason you did the conversion. Or you can stop guessing.
What A Continental Sensor Actually Buys You
A flex fuel sensor – almost always the GM-sourced Continental unit, cheap secondhand and easy to plumb into the feed line – measures ethanol content in the fuel passing through it and outputs a frequency the ECU reads. Fifty hertz is zero ethanol, 150 hertz is neat ethanol, and everything between is interpolated.
Every aftermarket ECU worth fitting supports it. Link, built in Christchurch and already sitting in a fair share of the modified Nissans here, handles flex on the G4X platform without drama, and Haltech and MoTeC are no different.
You end up with a petrol map, an ethanol map, and a car that blends between them in real time.
Living With Two Maps
Two maps means two dyno sessions, and the second is not optional. Your tuner needs the engine on straight 98 and on your highest blend, because the targets at each end are what the interpolation works between. Skip the petrol end and you get a car that is superb on ethanol and detonates its way home on pump gas.
Worth verifying once it is running:
– fuel pressure under load, on a proper gauge rather than the ECU’s guess
– injector duty cycle at the ethanol end of the range
– the sensor’s reported percentage against a test kit
That last one takes a graduated cylinder, some water and five minutes. Sensors drift, and they live in a hostile place.
Certification, WOF And Keeping It Legal
Where LVV Certification Comes Into It
Modifying a fuel system is modification work, and in this country that puts it in front of the Low Volume Vehicle certification system. Relocated or replaced lines, a surge tank in the boot, a swirl pot, non-standard tank fittings – exactly the parts a certifier examines, and exactly the parts people fit without thinking.
Talk to your local LVV certifier before you buy anything, not after the car is back together. They will tell you which hose specifications they accept, how they want lines routed and secured through the cabin or boot, and what they expect at a firewall penetration.
That conversation in the right order costs you a phone call. In the wrong order it costs you a rebuild.
What A WOF Inspector Will See
A warrant is a lower bar than certification, but it is the one you front up to twice a year. No inspector is measuring ethanol content. They are looking for leaks, chafed or unsupported lines, missing clamps, and anything routed where it can rub or cook. A braided line cable-tied to a brake hard line will fail, and it deserves to.
Ethanol makes the leak check more relevant than usual, because degraded rubber weeps long before it bursts. If you can smell fuel in the garage after the car has been sitting, find it before someone else does.
The cars that do well on ethanol here are the ones that get driven, on a blend the owner can genuinely source, with a sensor watching what is actually in the tank. The ones that do not are usually parked half-full somewhere damp, waiting on a fuel that is not coming. Neither outcome says much about how good the conversion was.
4 Comments
The phase separation bit is the one that caught me out. Left the S14 sitting over a Chch winter with about a third of a tank and it would not run properly for weeks after. Dropped the tank in the end and there was a proper layer of muck sitting in the bottom of it.
Gull coverage round here is basically nothing so yeah, drums it is.
Good writeup. One thing worth adding on the sensor – mine read about six percent high against a test tube check and I chased a rich condition for ages before I thought to verify it. They are cheap enough that swapping it was easier than trusting it. Also the frequency output wants a pullup on some setups, which caught me out on the G4X install.
Question on the injector sizing – you say size for 30 to 35 percent over what you are chasing, but does that still hold at higher duty once the bigger pump is in, or is it worth going up another size anyway? Running 740s on the RB and wondering if I have left it too tight.