chip octane mpg

[lolcantturn]

sup. I have a TRM 91 octane chip on my M50 (no knock sensors) swap but I've always used 87 (never saw any butt dyno difference). However should I be running 91 for mpg sake? Would I actually see a difference in mpg even though I'm going to be paying .30$ more a gallon? Thanks

[nando]

if the chip is tuned for 91, you should be using 91. otherwise, you may as well sell the chip because you aren't making any use of it.

[lolcantturn]

Figured. I just haven't felt any posterior dynamometer difference at all running 91 for a few days.

[bowtie2bimmer]

Alot of the reason too is since they raise the limiter its to reduce the chance of predet

[nando]

what? rev limiters have NOTHING to do with detontation.

[bowtie2bimmer]

a rev limiter is directly related to valve float , i know that'

but it's commonly accepted that as you rev higher and internal temperatures raise it increases the likelyhood of predet

[nando]

you aren't going to get valve float on a BMW unless you money shift it. and it's not going to cause detonation, either.

these aren't GM V6's....

[bowtie2bimmer]

haha ironic you said that... last car I owned was a s10 with a 262 v6 for 9 years lol

[mikeedler]

out of curiosity, why would you need to run 91 octane if it isn't detonating?
and weak valve springs will cause an M20 to "valve float"- that's why the rocker arms snap off.

[lolcantturn]

out of curiosity, why would you need to run 91 octane if it isn't detonating?
and weak valve springs will cause an M20 to "valve float"- that's why the rocker arms snap off.

I'm curious about this as well, definitely no knocking or any adverse affects from me running 87 as opposed to 91, and I don't feel a difference in butt dyno, but I'm curious if its a difference in MPG?

[nando]

you have knock sensors.

the chip increases ignition advance. but since you're running 87, the computer just retards it back until it stops knocking.

[lolcantturn]

There are no knock sensors on a M50 non vanos.

[lolcantturn]

yes or no on the mpg?

[Kershaw]

you might see better. 87 explodes slightly quicker and slightly more violently than 93.

only way to really tell is drive for a month (better averages than 1 tank) with 87 and then 1 month with 93 and chart your mpg.