A lot of you guys on this board say that you run advanced timing anywhere from 4 - 8* it seems. Just out of curiosity, what octane gas are you all using? I just advanced mine to 6* and it really smoothed out the engine and seems to pull higher harder, but I've got a tank of 87 octane Shell gas. Is this a safe thing to do if it doesn't knock or should I go mid-grade (89) ?

 

the diffrent octanes burn at diffrent temps so depending on the compresion of the engine and how much you have advanced and the temp should help you decide which gas to use...
i am currently running 87 octane with one of brians chips and advanced 8* and i have no knock or ping. i even pulled the plugs to see.
also i made the mistake of putting 87 octane in my 90 300zx and it ran like poop and detonated a few times. it has a 10.5 compresion ration engine that needs the higher octane. thats why the factory recommends it. i think the 4th gens also have around a 10 compresion and recommend 92 or higher. try it and see you can always add some octane booster if you start getting knock then put in new gas

 

If it's not pinging then you are good to go. I have mine at 6*, but I run 93 octane. 87 pings too much, and 89 is ok but pings during heavy loads (which is rather normal). So, I just play it safe and use 93. Ohh, and this is w/ a 180* thermostat, but during most of the year it's running hotter than that (200-220)

 

i advanced mine 6* and have a tbichips.com Stage 1 chip and have used nothing but chevron or shell 91 octane, dont want to see what would happen if i put a lower grade, it does hurt the wallet though seeing that i live in the Bay Area (CA), highests gas rates in the nation baby.

 

were pretty bad here in NJ too but i always use 93!

super plus is my favorite because it cleans out the tank from water and such

 

my car is only at tdc though as well.. i might advance mine soon

 

i have basicly adjustable on the fly timing (thanks to Craig Moates!)

on 87 octain, i can basicly always run 4* advanced with no knock, even dataloging, i show no knock above the normal 1 or 2 counts here and there.

most of the time on 87 i can get away with 6* most of the time, but i have a 160* stat, so my temps are low, if i start to heat up (sitting in traffic) under load i show knock.

 

I always run premium (93 octane here). If you add up how much the difference between a tank of crap (87 octane) and a tank of premium is it's like $3.

 

I'm running 6* advance with the stock chip, headers and catback, with no detonation so far on 89 octane.

 

As combustion temp goes up, so should your octane??

 

OK, now I'm noticing that my car shudders at idle in town when cruising for a while. Is this evidence that I need to retard timing or up the octane? I have no way of monitoring knock counts, I'm going off of driveability. The car runs well otherwise.
What do you guys think? :hail:

 

Sounds to me that you "Loading up" the carb. Basically what it means is that when you sit and idle, the car get too much gas and eventually starts to flood, hence the rough idle. To test this, put the car in nuetral and rev it once, the check the idle. If it smooths out, than that's your problem. Perhaps you need to change/check you fuel filter or need a tune-up. There are a ton of things that will 'cause that.

Anyway, the stock v-8 has a compression ratio around 9:1. This ratio should run just fine on 89 octane or better. It could run just fine on 87, but I think you'll have better mileage going with the 89, it burns more completely and produces a 'lil more power under the throttle. Where a 10:1 car needs 93 octane. Usually most racers go by compression to judge what gas to use. Some people go by what there computers say, but I don't believe in that computer BS. Take the car to the local drag strip one night, run 89 gas for a few runs, then drain it and run 93. Your time slip will tell you which gas worked better, then you'll know.
I have 10:1 so I use 93 or higher gas.

 

I think my car is in a pretty good state of tune right now, recently did: fuel pump/filter, plugs/wires, O2 sensor, oil change, air filter, thermostat, probably something else I'm forgetting. I know there could still be something else causing it.
I'll have to try revving it to clear a rich mixture, so basic I hadn't thought of it.
Also, unfortunately since '95 there isn't a "local" dragstrip, probably 1-1/2 - 2 hour drive to the closest.

 

I don't mean to insult your intelligence, but I just thought of something.....

When's the last time you ran injector cleaner through your gas tank, and sprayed some 2+2 gum cutter in your carb. I've already had a rough idle and that's all it took to straighten it up.

I have over-looked this before as simple as it is......Just wanted to ask, so you didn't do something stupid and spend $$ when you didn't have to like I did
Oh well, you live and you learn, I guess.....

 

Yeah, I was thinking about that today, too. It's been a little while. Oh, and don't worry about insulting my intelligence if you have a good suggestion, if I knew or thought of everything I wouldn't have to ask, would I?