Ok guys,

Recently I posted that using 91ron fuel on a 3.0L ECU'd 3.5 is a bad idea due to aggressive timing used on the 3lt engine. For this I was shot down and told I was full of shit.

Here is your proof. Comparison of 6G72, 6G74, and 6G74 Ralliart Ignition maps (You will note the 6G72 is up to 6 degrees MORE aggressive then the Ralliart tune - With major advances like this, 91ron fuel is a BAD IDEA).

While the ECU may be able to adapt to certain things (fuel wise) - Ignition map is static.

http://i419.photobucket.com/albums/pp271/db_newman/Untitled-3.png

Here is the fuel maps (these are static between all 3.5L equiped magnas).

http://i419.photobucket.com/albums/pp271/db_newman/Untitled2.png

You will note the fuel map is also noticeably leaner in some areas on the 3lt tune, another reason to use a higher quality fuel.

--

Another thing found in research - Sports/VRX tuning is NO DIFFERENT to Executive.

So please, for those whom have completed a 3.5L conversion, use higher quality fuel and preserve the life of your engine.

Dean, the timing in the high rev/low load areas (1500-7000rpm/10-50% load) arnt of too much concern (the 3.5L engine can take a reasonable amount more timing in this map section BUT of course within reason) BUT if there was 6 degrees more timing in the low rev/High load areas (1000-3000rpm/60-100% load) then that could cause a bit of a issue with pinging on 91 octane especially on hot days.

As a example the 10:1 comp 3.5L currently in my car is running 40deg timing from 2250 to 7000rpm thru the 10-50% load areas and also from 4500-7000rpm thru the 50-70% load areas and shows no signs of pinging (on 95 octane fuel and can also run on 91 if required but not really recommended).
Up top 100% load from 5000-7000rpm its running 32deg timing, the car is also quite a bit leaner than the fuel maps you have shown above.

Best advice is to err on the side of caution and if you can get a set of "knock cans" on your ears and hooked up to the car and load it up to listen for detonation as each engine is just that little bit different (ive seen 2 identical stock engines on the engine dyno during my MMAL days and one could take a leaner mixture and more timing than the other.... Strange but true and just shows of production variances do happen)

Yea this was basically a word a caution. I have used 91 in my car post-conversion before, it didn't run too well. 95 seems to be a much better medium and the 3lt timing is not exactly linear... It seems all over the shop. Looks like mits were trying hard to give it more low-down.

Just remember that more timing in the low load areas (under 50-60%load) is usually used to assist with "cruise mode", to enhance throttle response (makes it feel snappy/perky lol ) and to give better around town driveability.

When ever you "stand" on the throttle or accelerate hard the engine load jumps to 90-100% load (that is just a rough guide), of course on a boosted engine this peak load can go as high as 300+%

Thats why when you gently gently lean on the throttle of a engine with a fair amount of timing you are only submitting that engine to lowish load (under 50% load and say 40deg of advance) timing it generally wont "ping" but if you give it full throttle from a low rev point/high load (1500rpm/100 load) and run high amount of timing then it will ping the ringlands off lol .

Of course boosted engines are a whole different ball game due to spool, air charge temp etc etc.

Alright so all of this means jack shit 2 me... what do you guys run in ur cars???

I love how our maps have 400% load with exactly the same values as 100%, what the hell is the point of having it there!!! Id love to see what would happen if indeed at 400% load car ran those maps. (which of course will never happen on N/A)

I agree with Dean, running such aggressive timing on 91 you are asking for trouble

All that needs to be done to fix those extra rev and load coloums is to adjust the metadata elements for the load axis to 11 and the rev axis to 18, that then removes them but doesnt effect the others.

40deg timing in the low load areas (under 50% load) from above 2000rpm is not a issue, ITS large amounts of timing in the high load/low rev (80+%/1000-3000rpm) areas that will kill our engines with no knock sensors quickly on 91 octane fuel especially when people have a habit of standing on the throttle from low revs in a too higher gear.
If you look at the ralliart map it runs more agressive timing than a 3L in the 80-100% load areas yet it runs slightly higher comp and was factory tuned for 91 fuel, also things like piston "head" shape etc all play a part in max timing our motors will take too.

As i originally said in a earlier post, each engine is slightly different and what one engine takes and work well with wont always work on another engine thats the same. At the end of the day, anyone who just throws an tune into there car without doing some simple logging tests is silly, take it slowly and build it up like any good tuner will.

We only run 98 premium in both our cars.

In the advance we always ran 91 fuel, but last year the car got to the point where it stunk so bad, like dead eggs we had to get mitubishi to check it out. They cleaned injectors, reset everything and said to switch fuel. So we went to 98 fuel and it improved dramatically.

As for the VR-X the original owner only ever ran 98, and thats what I've continued to do since purchasing it.

Boost.

Alright so all of this means jack shit 2 me... what do you guys run in ur cars???

That is because this thread is a load of shit.......I have done over 40 of these conversions over years, except perhaps 4 or 5 of these ALL of them run the 3.0 ECU, dont knock, have not fallen apart, have not failed, have not lacked in performance etc etc

I have no idea wtf a ralliart map has to do with anything here either as wel all run ralliart maps in all of our cars :nuts:

Given that the only read difference in this is capacity, there is no need to panic ppl, the 3.0 ecu will run fine as many here on AMC have already found out. Is good that someone is concerned but please, if you are going to make statements such as these, please get your facts right initially. There is a difference in the map but not a difference that will kill a motor

And as for car not running as well on 91, I assume that there are some power figures to show this or was this seat of the pants (which seems to be the only way people rate cars these days)

We only run 98 premium in both our cars.

In the advance we always ran 91 fuel, but last year the car got to the point where it stunk so bad, like dead eggs we had to get mitubishi to check it out. They cleaned injectors, reset everything and said to switch fuel. So we went to 98 fuel and it improved dramatically.

As for the VR-X the original owner only ever ran 98, and thats what I've continued to do since purchasing it.

Boost.

The bad eggs smell is from the catalytic converter. There are a few reasons they do this, typically when high amounts of sulphur are produced it is a sign of something amiss somewhere else like poor detonation or injection system. Sometimes the smell can be caused by the cat itself failing. As in your case, the car just needed a bit of TLC if it seemed to stop smelling after things were fixed up.