Quick question I couldn't find...

For a base flash with minimal mods (TBE and MBC), do you need two seperate maps for 91 and 93 octane for the car to be safe? Does the reflashed ECU account for the fact it may be running 91 and then 93 a few days later?

Are two seperate tunes needed? Thanks.

 

two seperate tunes would be ideal. you should tune for the octane you run normally.

 

2 separate tunes would serve you best. Sure, you might not need it but it's always better to err on the safer side of things. Using 91 on a 93 map could cause ...

 

Well, the stock evo is tuned for 98 RON, ~93 octane here in the US ((R+M)/2 I think). We only get 91 octane here in cali and when I datalogged my car, I got 4-8 accounts of knock from 3.5k to redline.

I would say that you need a separate tune. I basically pulled ~4 degrees of timing from 1/3 of the timing map to keep it from knocking on 91 octane, otherwise completely stock car.

 

My real confusion is on the stock evo, you can use 91 or 93. I've been unable to take 3rd gear pulls at either, but I'm assuming its rich enough on either for there to be 0 counts of knock. So if the stock map can use both, why couldn't a tuned map? Does it have to do with the lack of a safety net with A/F ratios?

 

if tuned right it could. but why?

 

with a higher oct. you're less knock prone so you can run more timing.

put in a lower oct. fuel on the above map and you're basically going to knock all over the place...

if you're 93 oct. map is very very conservative i guess you could get away with pumping in 91 oct....but what's the point?

if you only have 91 oct. like the cali people do, we usually get a 91 oct. map and a 100 oct. map, and change them around depending on our mood

 

No, like I said before, you WILL get knock using 91 octane. The ecu is just forced to pull timing to keep from grenading. It will also adjust the long term fuel trims, i.e. richen up. My high fuel trim was 126 before I started tuning on the car and the A/F ratio was somewhere way below 10.0 after 5.5k trying to prevent knock... which it still got.

My high fuel trim has since come down to 118 last time I checked, so it's starting to lean back out, I think. This is because I pulled quite a bit of timing so it's not knocking anymore.

 

bumpin an old thread for two similar questions:

I have a 91 oct tune:

1. how much hp am i loosing over a 93 oct tune

2. is it possible i am running into problems as a result of ALWAYS using 93oct on
a 91 oct tune? I didn't choose a 91oct setup and it is hard to find anything but
93 around here. I assumed it wouldn't make a difference but i am starting to
question the power of the car. Could i be slowly hurting sensors by running it
too rich ...or ....? Sorry if this is a newb type of question haha.

 

Would lowering the boost while keeping the same AFR / Timing maps help?

This would be like tuning for 93 octane map at say 24 psi tapering to 20 by 7k RPM and lowering the boost to 19psi in midrange tapering to say 17 psi at 7k RPM...

I am planning on doing something similar in my car as I can get 94 octane where I live, but might have to use 91 octane on long road trips if better fuel is not available. I have an AVC-R so I have low/high/off(running off wastegate) settings for boost... In case I have to use **** gas, I will put some octane booster and turn the boost controll off running of the wastegate or just lower to 19 psiş

 

at the same AFR the lower octane fuel has to run a bit less timing which can equate to significant power loss across the board.

Let me know via PM when you're ready and I can get you fixed up with a great 93 octane tune