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Discussion Starter #1
(Apologies if this is already answered... surely it must be... but I can't find it...)

What fuel does everyone use? I note a few threads saying ethanol can cause higher than normal pressure in the fuel tank so I avoid that but how premium should we go? Don't want to be wasting money...

My car is an 83 but PO put a computer in it and got rid of the AFM...
 

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But Mad North-Northwest
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10% ethanol's not an issue. That's all we get in California and it works fine.

A US 2.5 V6 only needs 87 octane (that's PON, I guess it would be ~92 RON for you down under). Not sure what the tuning was outside of the US, though...check your owner's manual.

If your engine or timing have been modified all bets are off, though. You may need premium if you hear pinging.
 

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If the airflowmeter (AFM) has been deleted the car has been converted to speed density (SD). If somebody has "put a computer in it" this potentially suggests stand-alone engine management.

This may mean all bets are off what a suitable fuel may be though in all likelihood you should be safe with a similar premium fuel that was for sale from where the car comes from unless it was track only. Most people who will go to SD and stand alone engine management are performance minded and would tune for premium fuel.

To start with it might be worthwhile to check whether your ignition timing/advance is stock or not.



My car is an 83 but PO put a computer in it and got rid of the AFM...
 

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Discussion Starter #4
Yeah sorry, I've had the car for three years and done 40,000 km in it. I've been using 98-rated fuel or 95 if I'm ever caught short. The question really is whether the 98 ultra-premium stuff is overkill.

Meanwhile... is "put a computer in it" a bad way to speak or something? I know the original system is technically also a computer... or should I only say "ECU" or similar around here? Oh wait, I bet ECU is wrong too... ah, so much to learn.

Specifically the ECU in my car is the previous generation of this: e440d Universal Select ECU | Adaptronic
 

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(Apologies if this is already answered... surely it must be... but I can't find it...)

What fuel does everyone use? I note a few threads saying ethanol can cause higher than normal pressure in the fuel tank so I avoid that but how premium should we go? Don't want to be wasting money...

My car is an 83 but PO put a computer in it and got rid of the AFM...
Remember that in '83, we still had leaded petrol here in Aus. Leaded pertrol had an octane rating up around the 96-98RON mark.
So for a standard car, that should be kept in mind. The car's ignition timing would have been fine running on that octane rating.

But as others have mention, you have a programmable computer (nice choice by the previous owner BTW).
Octane rating and ignition timing is a complicated combination, but if the previous owner had any sort of decent workshop tune the computer, then they should have tuned it to suit fuels available today. If you can't hear any knock/detonation/pinging when running on 95 octane, then just run it on that and save some money.

Don't go putting any ethanol blended fuel in the tank unless you can monitor air/fuel ratios accurately. Ethanol blended fuels have lower energy densities (the more ethanol, the lower its energy density) and if it's just put in the tank, the engine can run lean because of this. There may be enough headroom in the computers tune (it may be running richer than it really should be on petrol), but there may not be as well. So accurately monitor air/fuel ratios if you use any of the ethanol fuels.

Now, having said that about ethanol fuels, Adaptronic have a firmware upgrade that allows users to add a Zietronics ethanol sensor to the fuel system. This sends appropriate data to the ECU based on the ethanol content of the fuel. And now there is a tunable compensation map for both fuel and ignition to allow you/your tuner to take full advantage of ethanol blended fuels, while making absolutely sure that you are running safe air/fuel ratios (this will be awesome for force fed engines!).
 
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