I'm running a base L03 and I'm wondering what grade gas everyone's running to get good mileage. Is the higher octane realy worth the extra cash? Once i get through with my mods I'll be using the 93 octane but for now is the 87 good enough? I've been using either 89 or 91, i can't remember recently. What is everyone else using?

 

general rule, is to run the lowest octane you can, without pinging.

stock i ran 87, modded, i have 1 chip for 87 which i usualy run, i also have a chip with more base timing, that i use with 92 octane.

 

When I was stock I could run 87 without knock. After I bumped the base timing up a bit and modded the car I had to run 92. If you are bone stock with the factory base setting of timing, you can run 87 without any problems.

 

i run 87.


its a L03. even if you modded the crud out of the motor, its still a street driven 305. i run 87, and i intend to keep running 87, and if they made a cheaper gas that it would run on, id use that.


you do NOT make any more power with higher octane gas, and the l03 is NOT a performance motor that needs higher octane. all you are doing is wasting money.


now if you advance the timing tables from stock, you may need higher octane gas...... but its not a worthwild trade in my opinion since the car will still be a slow dog.... only now its a slow dog that cost twenty cents more per gallon.

 

I've heard that the high octane will help to clean up the engine, true? And what abotu additive such as the STP stuff that you're supposed to use every tank?

 

FALSE.
FALSE. False. false.

the exact same detergents that are in the highgrade at the pump are in the lowgrade. that wasnt always true, but it is today.


cleaner or octane booster?

the "boosters" dont do crud. they may raise it from 87 to 87.3 (a whole 3 POINTS) but you dont need the octane, and they're ineffective anyway. you would have to be RIGHT on the bleeding edge for them to work.


as far as the cleaners.... they're pointless. gas sold at the pump already has detergents, and what are you trying to keep clean anyway? gas is a solovent. unless you let it evaporate and turn to varnish, its fine... the pump is submerged in it. the lines arnt ever going to be restricted for as long as the car is driven, and the injectors cannot be properly cleaned on the car anyway. so after a few hund thousand miles, get your injectors cleaned(properly, off the car), and you're set for thousands more...

 

I run 87 octane in the '87 Trans Am it is pretty stock.

I run 91 octane in the '92 Camaro it is modded and has a custom chip.

 

i run 87 in my 89 TBI.
full exhaust, headers back open element.
of course my ecm is giving me code 43(esc). but it is my inderstanding that is because of the headers.

 

I usually run 89 but I gonna try 87 soon.

 

93, it's only a couple bucks more a tank. I think the trade off for increased timing is worth it. Oh, and did I mention the nitrous likes it too.

 

I like to run the increased timing too.


EVERY 305 I've owned which would be 3 all from thirdgen maros, HATED 87 octane. Stock settings Pinged and Dieseled really bad.

They didn't like cheap arco gas either. And yes I had them all cleaned of carbon too.

I run Union 76 92 oct in the car, 89 oct in the s10, and 87 oct in my 2.8 jimmy.

 

87 is all you need for a nearly stock LO3. Unless of course pinging is an issue.

 

and if pinging is a issue on your nearly stock L03, then somthing is wrong with it.

 

yup :P

 

i usually run 93 and have run some parial tanks of 100 but the chip i have the timing curve isnt stock..

i noticed alot better throttle respnse with 100 actually but at 3.10 a gallon i cant afford to run that all of the time.

 

87 Octane and it'll never get any higher. I just wish I could get my friend with a stock L03 to understand the simple facts of octane. Oh well, its his money.

 

Damn..you mean that poster at Sunco stating "94 Octane, time for a spring cleaning" is false advertising...man what a waste. 87 octane from here on in it is.

 

If it burns, Ill buy a tankfull of it. With only 14 in the city, ~18-20 on the highway, I cant be too picky.

 

I agree with not needing high octane for these cars. The only car I had that got high octane was a late model EX accord. Thing would have audable ping on tip in and under very high load with regular.

 

You guys say that with your 87 octane you don't knock.

Is this just audible knock you aren't hearing... or have you got out a scan tool and looked to see if you are really not getting any KNOCK via the knock sensor.

If you have a knock sensor, you should never have audbile knock.

 

I thought he knock sensor was designed to catch engine knock prior to it occuring and then lower the timing...or something on those terms.

 

it catches it when it senses it, then it retards the crap out of your timeing.

mr dude:
"so after a few hund thousand miles, get your injectors cleaned(properly, off the car), and you're set for thousands more..."

how do you go about doing this?

-chuck

 

Basically, the knock retard works like this... The knock module, which is that black thing behind the relays, listens for a peticular waveform from the knock sensor. Once it sees that, it sends out a pulse to the ecm. The ecm takes these pulses and adds them up. Then, the pulses are multiplied by an attack rate to get degrees of retard and they are added into the overall knock retard, which is something up to around 15 degrees or so, accumulated while knock has been present. All of this is then subtracted out from the spark advance. After it stops knocking, the accumulated retard is then decayed out to zero. That, I think, takes around 3 seconds on a stock ecm. One thing about the ks is that it hears detonation before it becomes severe enough to be heard, which is one of the reasons you usually cant hear knock. With a stock exaust on the car (so its quiet) and the windows down I could catch it, but its real faint and hard to hear.

 

WTF are you talking about? The knock sensor is on the bottom of the block in a coolant passage on the passenger side of the engine block.



My point was, is that you people say you don't knock, which you should never HEAR knock with a knock sensor, but you may be *knocking* so that the sensor pulls out timing. Depending on the amount of knock and the rate at which it occurs, is the basis for how much timing is pulled. Which is why sometimes you can't tell you are knocking because it doesn't pull ALOT of timing out, but easily enough to cost a half a second at the track without you even knowing it.

 

A knock sensor does not get rid of all audible knock. He was describing how the knock system works and he is right.

 

You can hear knock when its occuring. Its real quiet with the ecm in control. Usually, though, the only indication of knock,on an unmolested ecm, will be the cars power nosing over momentarily, along with knock reported through the ALDL. I think another reason knock isnt real apparent on a stock ecm is the fact that the time needed to fully restore the timing is quite generous IMHO and its hard to tell when the timing is being reintroduced. The car just sort of looses some power for a bit while its recovering. But yes, to be absolutly sure, one must take a look at the data stream to see if any knock is reported.

The module is there because the ecm doesnt have the hardware onboard to analyze the signal from the knock sensor. It acts as a go-between so it can look for the waveform of detonation specific to the engine and send a signal to the ecm that it can use, which is a pulse.

 

You can send them out to be cleaned. I used an ultrasonic cleaner and some 'diesel in a can' to clean them. Worked pretty well. Wasnt much, if anything there but whatever was there was removed.

 

Correct. The knock sensor is nothing more than an accelerometer. It will produce a voltage that is represented by a certian value of knock.

 

Stock I ran 87 fine, when I advanced my timing I ran 89/91 and with my current setup I run 92/93.

 

I run 87 when it gets really expensive (now) and just keep a light foot. I've found 87 to work best with my setup believe it or not. I've run 87 and 94 at the track, both with the same results, go figure.

 

You're alive! Are you still in C-bus?

 

If it helps I run 89 on my LG4 only because one a local gas station sells 89 as the same price of other places 87.

I was getting some slight knocks with 87, but my car is moded somewhat.in sig

I think the open air elements and uncoated headers in the summer time attribute more towards knocks then the octane levels.