In the last 9 months or so my '88 n/a 'Vert has gotten VERY particular about the gas she likes....

Last fall I got a tank of somethin' she didn't like and she ran so crappy I thought I had a clogged cat or fuel injectors. The engine sputtered, wouldn't idle steady and threatened to stall often. It backfired (severely sometimes) & smelled sulfury and seemed to be running exceptionally rich. I haven't gotten a tank that bad since, but some tanks are better than others and occasionally, like this morning, I filled up with some nice fresh Mobile Super 92 Octane and she's now purring & singing and just loves it - and not even a little backfire!

The car was stock when this started, but now has intake, exhaust and ECU upgrades and none of this seems to have had any effect on the issue. I also replaced the fuel filter and last week the O2 sensor.

Has anyone else seen this sort of thing? Is it maybe 'Winter blend' gasoline causing the problem?

 

87 octane

There should be no reason for higher.

 

The new ECU requires the higher octane.

 

What ECU is it? Did it mess with timing or what? How does it need more octane?

 

My car has sipped Shell a few times and rewarded me with very nice billows of black smoke and terrible shaking.

She only like Chevron regular, with Citgo 2 stroke premix. Then, she won't even studder at all.

 

Every car I've owned hates Sunoco gas. My TII likes Citgo and BP best.

 

that must be the nastiest gas ever

 

Well, it's oxygenated, which is a bad thing for turbo cars because it has a lower real octane rating than normal gas. I don't know why my other cars hated it, but my MX6 would run like crap whenever I got gas from there.

 

The gasoline issues have been going on for about 9 months, the new ECU has only been in for one.

The ECU is from Autothority.com (and I'm still trying to decide if it made much of a difference.... The 'verts ECU isn't a standard n/a, but the turbo map didn't work at all and we had some trouble sorting it out.)

Anyway, they claim that they tune the map for the premium gas, and I believe that since the timing is advanced it's closer to detonation range and the higher octane compensates. I could just be blowin' smoke, too...


But aside from that, I have not yet narrowed it down to exactly WHICH brands of gas are good and which are bad. After the first real bad tank (I don't remember which brand that was, unfortunately) Citgo straightened it right out. And it loved the Mobile I put in it this morning.

 

I almost always run 87 chevron with techron... my car has never given me problems... Once i stopped at a HESS and put a full tank of 87.. for some reason she didnt like that to much

I've tried running 89 and even 93 and my car hates it. She is tuned to run on 87 and makes the best power doing so..

-markus

"N/A cars there is no reason to run higher octane, in fact you'll get a slight power drop... i stress the word Slight..."

 

it depends on how high the compression on your engine is, cause it can stand up to like 87 pounds of pressure ( if its 87 octane) any higher itll combust without spark
thats why when ur engine starts to knock u kick it up a grade. 89 can take more pressure before it combusts,a nd so on and so on.

 

huh? I don't think the octane rating stands for the PSI the fuel can handle.

 

what? i use sunnoco 94 octane personally.

 

yeah i'm with ya santiago, the 87-89-93 thing is definatly not the PSI engine rating... rather, it's the minimum octane grade rating, 93 octane is "heavier" it takes longer to move around in the cumbustion chamber, hense : it's better for a turbo, it also has less of a chance of detonation

Here with us N/a guys we dont have boost, 87 octane gas is "lighter" it moves around and acctually ignites faster, giving your n/a mazda better performance..

-Markus

"That sounded pretty smart, i guess that's about right"

 

Where's icemark, i'm sure he can fill in in this situation...

anyway, not to steal the thread or anything

-Markus

" :END HIJACK OF THREAD: "

 

Well, I'm not Icemark, but NAs (assuming stock timing and ECU ) should be running 87 octane. TIIs should be running as high as you can find, which is typically 91, 92 or 94. You need the extra detonation resistance that the higher octane fuels give when you have advanced yoru timing or are running forced induction.

Running high octane in an engine not designed for it will result in poorer burn, and thus less power and more carbon. The carbon will "artificially" raise the compression ratio until you NEED that high octane to avoid detonation.

 

87 Octane does not mean that compression cycle can prevent knocking up to 87 PSI.

87 octane is actually gasoline that contains 87% octane and 13% heptane

Octane is actually a carbon chain of 8 carbon atoms and is more stable than heptane. This is were your carbon build is from. Heptane actually is unstable and can ignite easily.

93 Octane contains 93% Octane and 7% percent Heptane.

 

good enough description for me, thanks

-Markus

"See, 87 baby yeah!"

 

Wooo I loved my college chemistry class. I was like thats what it means.

Santiago

 

umm, wtf?

How much % octane does 110 have, then? 110%? last time I checked, that's not possible.

 

Lead was added to gasoline because it reduce knocking. however it has its conseqences.

 

you really don't have to look at Rm/2

 

How does it work then?

 

holy ****, ur crazy intelligent with this chemistry stuff eh?

i hated chemistry, i feel stupid when i read wut u posted cause it's so like CRAZY.

 

Remember 110 Octane has lead added to it so the Octane increases. Its almost like having concentrated Octane