What fuel is optimum for stock SOHC 4G64?

[4g63lover]

The point of higher octane fuel is to avoid Knock/detonation.

It really is up to what people do with their cars. The way you drive it really makes a huge difference in what fuel you should use. EVEN on a stock 4G64. I drive my car HARD. I revmatch a lot and I heel-toe alot when I am going on spirited drives. Not to mention my car sits at 3000 RPM's @ 75 when I am on the highway. The car is driven the way it wants to be driven.

I agree with Adrian that the engineers design the engines to run on a certain fuel for a certain application, but the manufacturer recommendation is the BARE MINIMUM.

87 is good with bone stock 4G64's that are daily driven under normal conditions. i.e. driving like how a regular owner (non-TGC people) drive a Galant. Not everyone will modify or even drive their Galant past 3000 RPM.

In my case, I run 93. And save the "wasting your money" argument because I am not buying it.

When it was auto, my dad ran 89 in it. and when I started driving it some more I used 89/93 sometimes even 87 and I didn't feel a difference.

Now that it is manual I run STRICTLY 93 in it. The only thing I have done to the motor is an axle-back exhaust, intake and a V6 TB. I run 93 in it because it has a SIGNIFICANT difference between 87 and 93.

On 87, you can feel the engine work harder and detonate through the dash. If you watch it idle, the engine vibrates A TON more on 87 than 93. Going through the powerband in 2nd and 3rd (not much in 1st, it goes by too fast) the car is significantly more sluggish and the drop of peak power is felt earlier than when running on 93. It hit peak power at about 5800 RPM on 93 and you can feel power drop at around 5500 on 87. The car is also stronger and has more pick up from a 60+ mph acceleration on 93 in fifth than it does on 87.

I run 93, to me I've proved its worth just by how the car reacts to my driving.

It could also be due to my adaptive strategies that the car runs better on 93 due to the fact that I STRICTLY use 93 and nothing else but thats besides the case.

I feel a SIGNIFICANT difference. So I stick with what feels better. I wish I had a dyno or a datalogger to see the numbers to prove my point.

"Fuel is all the same 'til they get to the pumps" is a fact but not EVERY car is the same.

The engineers design these motors to run "properly" on a minimum fuel grade, it doesn't mean the engine will not run better on higher octane. EVERY engine knocks, I dont care if it's a 1.3L from a Honda Fit to a 6.0L V8 from a GTO. If I can prevent my motor from detonating that much more I am going to spend the money on doing it.

It amazes me how some people can spend money on wheels, JDM parts, all these expensive mods on their cars but they are content with running the BARE minimum in their fuel systems, coolant, trans fluid, oil, etc. Just because they think running anything above the minimum is a waste of money.

[Isaurio]

With your mods maybe youll get alil bit of gain in something bc you have more air intake and higher flow which in order to make a diff in performance you need either more fuel or higher octane fuel.

I might be crazy but you should get your cars ECU flash and tuned since you have more air coming in...you prob gain hp there but not sure if its worth it. With you mods (which is a nice list you got there) you have alot quicker throttle response and I guess you feel the car pull hard in 2nd gear. Thats how it was for me...right in 2nd gear my car was pulling. With your mods I know there was some diff bc one day I was just playing around with my brother and he was driving his gf car which was a 2006 Acura TSX 2.4L I4 motor. I did a quick pull with him and at first he had a good start off and got in front of me...after outlader manifold swap and intake and full exhaust system I had. Next time he came over and we did another pull...there was a big diff bc this time he couldnt get past me. In first he got the alil in front again but after 2nd my car pulled like a mother F!!!!! and he could not get past me.

I think i went off topic.lol

Ohh yeah. deeznuts and me soon are going to work on a tune ROM for the I4. Yeah shes is asking for a tune because:
when is below 700 RPM you feel the engine shake a little. This is due to the injectors not delivering the right amount of fuel bacause of the extra air and the diamante TPS sensor signal. "fact, i increase the idle and she is a smoth as new"
Thinking downscaling the diamante injectors
remap the evo MAF sensor.
TUNE TUNE TUNE. TRIAL and ERROR.

You right with the outlander and the diamante tb, the engine pulls a lot harder specially above 3000 RPM. "UN-TUNED" With the tune i will gain more HP but the best part is super throtle responce.

Before i go with my super built and leave the N/A world. LOL i'm going to make sure to make some HP increase with a few mods and a nice TUNE.

[Rabbi1991]

I use 95 and always wanted to try 98 ( pernir it's 98 not 97 ) but have not been able money wise since I want to fix everything there is to fix on the car first.

[bigmacak22]

who ever say to run the 87 on the galants must be stupid..and those people who are professional who are work for car factories must be on crack..how you going to run of 87..87 is low octane..and plus that 87 is for tractors..i have been put 87 on my galant what i see is a difference..my car was slower..slower than the turtle..you guys can run on 89 or 93 those dosages are for more speed in the car..my manual says to run on 87..so i was listening to that manual and got knocked out..car slow..the valves were noisey..so that way i came out with idea that those professional workers from factorys must be stupid and on crack that they don't even know what are they doing..as i say if you are running 87 than you must have a engine of john deere tractor, or cutting grass mower..when i use the 89 or 93 i feel that my car is flying in the air..

[DTP]

You know, the manufacturer and designers might have some idea as to what fuel to run in the car they designed... I would presume they know more about the cars than we do.

Maybe your car has other issues you attribute to the 87. My car is fine on 87 and I've tried all the others. Hows that for ya?


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[wetamup2k3g]

Yeah, if you have a stock engine on a non-performance car, and the manual says use 87, and you really can feel the difference (I couldn't), then you have other issues. I don't think our engines alter the ignition timing (I could be wrong, but in my searching i couldn't find where ours does) to the degree at which it could take advantage of the higher octane and the delayed ignition of the fuel because of its resistance to ignition. In fact, because we don't have knock sensors stock, the PCM can't know directly if the engine is knocking. So it doesn't take advantage of higher octane, and you'll waste that extra money running it unless you have other issues.

[Galant306m]

http://www.stopbuyingcrap.com/stop-b...ng-3-gasoline/

[4g63lover]

Yeah, if you have a stock engine on a non-performance car, and the manual says use 87, and you really can feel the difference (I couldn't), then you have other issues. I don't think our engines alter the ignition timing (I could be wrong, but in my searching i couldn't find where ours does) to the degree at which it could take advantage of the higher octane and the delayed ignition of the fuel because of its resistance to ignition. In fact, because we don't have knock sensors stock, the PCM can't know directly if the engine is knocking. So it doesn't take advantage of higher octane, and you'll waste that extra money running it unless you have other issues.

I'd hafta disagree. I work on cars day in day out. I don't have to rely on a knock sensor to feel the car vibrate while using different fuels. If something was wrong, like lets say a misfire, changing the octane will NOT mask the issue. AT ALL. I've gone over fuels, ignition timing, fuel maps, etc. for a lot of different cars from import to domestic and the labels in the manuals are merely MINIMUM requirements. The engineers aren't going to EVER put a MAXIMUM requirement on the manuals. The manufacturers wont either. I didnt read this shit on google or some website. I've done real life testing from scope tests to manufacturer specific scanners. I've even tested the knock sensor through knock lights (our cars have knock sensors they're just not connected to the ECU. Don't believe me? look under the t-stat housing you will see a plug with no connector, follow it and it will lead you to a knock sensor). And the PCM WILL alter ignition timing on EVERY car. Why do you think modern engines have crank sensors? It's not merely for tachometer reading. It watches when the piston hits TDC and if combustion is not complete 23 degrees after TDC guess what? it will advance it. If it is completed 23 degrees before it will retard it. The day I see an engine that will not advance or retard ignition timing is the day I will stop working on cars. It's the magic of electronic ignition, we don't need to manually adjust timing mechanically anymore. Especially with the advanced technologies of COP systems. The PCM will do all of it for us! (on stock cars anyway) Don't even get me started on Adaptive strategies!! OMG if you see some of the coockoo shit these cars are doing these days with adaptive strategy you will pull your hair out. Fuel octane counts, I don't need google or the internet to tell me that. I've seen it, felt it, heard it. the 9.5:1 or somewhere close to that compression for the 4G64's in the 8G is enough compression to make minute counts of knock so that is enough info for me to use mid-grade to 93 octane.

The fuel grade RECOMMENDED on the manual is a MINIMUM. It's the minimum requirement for the engine to last under NORMAL driving conditions with stock components. You think an intake wont affect fuel trim? It does. It is such a small change that the PCM wont throw a check engine light on because it would never ever complete the drive cycle properly but sure enough if you're looking at a scanner and saw the fuel trim, you will see it's a bit lean. You think the motor can knock then? Definitely. The leaner it gets the more chances of it knocking. The richer it gets the more chances of it pre-igniting. This is why most modern cars with electronic ignition, MUST be tuned after each modification. A 60mm throttle body with a short ram on a stock exhaust can cause up to a 10% difference in Short term and long term fuel trim. It WILL detonate at that point. Very small counts but it is present. To me, if that was the case I'm using 93. You will be blown away once you see what your average engine has to deal with on a daily basis. Most people run them on the BARE minimum buying the belief that the "engineers" know everything. You know how much shit the engineers have to change and recalibrate to meet emissions requirements alone?? most of these motors come out of the factory super-restricted for the mere fact that most of them would never pass an I/M 240 test on their own.

When it comes down to it, it's up to what you do with the car I guess. I will keep running 93 'til the car runs the same on 87 (will never happen). most people will run 87 'til they remove the oil cap and replace the car under it.

P.S. just because nothing "watches" knock in the motor, it doesn't mean it's not happening.

[4g63lover]

You know, the manufacturer and designers might have some idea as to what fuel to run in the car they designed... I would presume they know more about the cars than we do.

The problem with this is, like every one of us in here, they are human as well. The problem with MOST engineers (not all) is they've NEVER worked on a car before. It's all about numbers to them. If it makes sense in paper it makes sense in RL. Thats far from the truth.

It's easy to make it look good on paper, it's a whole different monster trying to make sense of it while it is happening in front of you.

Some of these cars are so over-engineered that you will literally go crazy trying to diagnose a drivability issue and end up at "replace with known good part". anyone whos ever looked at or read through a MASSIVE diagnostic flow chart will know what I am talking about. So these engineers that "know more than we do" is telling me (the tech) to start throwing parts at it? WTF? It's like telling your girl how to suck your dick because you've googled "how to properly suck a dick". Then when it doesnt work, have your friend have a go at it.

"Known good part my ass!"

[wetamup2k3g]

4g63lover, I'm at work sitting in my car as it idles with my little scanner on it watching my ignition advance hover between 8 and 13 degrees. If I run 93, will I see that advance change to a different number or am I oversimplifying? I'm not trying to be smart or nothing; I just wanna know if on my boney stock motor (means no mods at all at the time) will 93 really make a difference? I'll take a tech's word over an engineer any day; I'm a tech on trains and I know these engineers come up with shit that makes my life hell. Honestly though I don't think it will make the difference. I'm willing to fill up on 93 the next couple fill ups and hook the scanner up and see.


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[Galant306m]

LOL if you have a stock sohc non turbo galant run 87, my truck is rated for 89 or higher and i use 87 in it with better gas mileage and no issues. We dont have hand built 12:1 cr Ferrari engines here they are in the realm of NORMAL ENGINES. Just run 87 its not going to hurt the car and your butt dyno wont be able to tell the difference between 87 and 93 anyways because there is none.

I wish all you guys could log your cars ecu because then you would find out that 93 isn't doing anything for you. Btw your cars do have knock sensors from the factory its in by the timing belt assembly.

[4g63lover]

8G knock sensor is located in the back of the motor. The sensor in the timing belt area is the crank position sensor.

[4g63lover]

4g63lover, I'm at work sitting in my car as it idles with my little scanner on it watching my ignition advance hover between 8 and 13 degrees. If I run 93, will I see that advance change to a different number or am I oversimplifying? I'm not trying to be smart or nothing; I just wanna know if on my boney stock motor (means no mods at all at the time) will 93 really make a difference? I'll take a tech's word over an engineer any day; I'm a tech on trains and I know these engineers come up with shit that makes my life hell. Honestly though I don't think it will make the difference. I'm willing to fill up on 93 the next couple fill ups and hook the scanner up and see.


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Honestly, on a bone stock motor you will most likely see only a slight difference in ignition timing when running 93. What scanner are you using? The scanner might only even see it for only a fraction of a second. In that case with the stock auto, I doubt you will see a huge difference.

On a manual swapped 8G it could be more noticeable because the clutch and flywheel weigh less than the TC and the engine will not have to work as hard to rotate the assembly. I'll have to get the scanner in front of me to see the numbers. I wish I had a Ethos or a solus pro for myself just cant fork out the cash for it at the moment.

Small difference or big difference, wouldn't you agree that the car would still run slightly better on higher octane than lower octane? Just by looking at the numbers on the scanner. I honestly feel that watching the ignition timing will not completely answer the question compared to if we had the knock sensor actually send a signal to the ECU and show the counts. You will see a SMALL difference in ignition timing just by using different octane but you will see the most difference in ignition timing under load and if it had to compensate for mechanical issue or a fuel management issue (i.e. fuel trim percentage, MAF and MAP values, o2 sensor readings, etc.)

[IVORY_G]

I run 91 since thats the highest octane we have in CA. Ive felt the difference b/w 87, 89, & 91. 87 car runs like shit, 89 runs better, & 91 is the best IMO. I called my local dealer and spoke to the lead mechanic there to verify what was the recommended fuel grade. He told me not to run 87, & that I could run 89, but I would get better gas mileage and the car would run smoother on 91. So thats what I did, & I get more mileage per tank on 91. I know this bcz I reset my trip odometer every time I get gas, and saw the mileage increase there.
My 240SX was the same way, & on the inside of the fuel lid it said "Premium Octane recommended"...

[wetamup2k3g]

Honestly, on a bone stock motor you will most likely see only a slight difference in ignition timing when running 93. What scanner are you using? The scanner might only even see it for only a fraction of a second. In that case with the stock auto, I doubt you will see a huge difference.

On a manual swapped 8G it could be more noticeable because the clutch and flywheel weigh less than the TC and the engine will not have to work as hard to rotate the assembly. I'll have to get the scanner in front of me to see the numbers. I wish I had a Ethos or a solus pro for myself just cant fork out the cash for it at the moment.

Small difference or big difference, wouldn't you agree that the car would still run slightly better on higher octane than lower octane? Just by looking at the numbers on the scanner. I honestly feel that watching the ignition timing will not completely answer the question compared to if we had the knock sensor actually send a signal to the ECU and show the counts. You will see a SMALL difference in ignition timing just by using different octane but you will see the most difference in ignition timing under load and if it had to compensate for mechanical issue or a fuel management issue (i.e. fuel trim percentage, MAF and MAP values, o2 sensor readings, etc.)

I figure I'd see more of a difference at load but I can't really pay attention to the values and try to maintain a set speed to control this experiment and drive all at the same time safely. Like I said before, I ran 93 once and noticed no difference honestly but it was more of a seat-of-the-pants type evaluation. My thought process is, running 93 would burn slower, meaning the ignition would have to advance to take advantage of that, but if they set the base timing and all the other engine operating parameters on running 87 and it runs fine, how can the engine know it's running a higher octane if it was set up for 87? Does the PCM advance the timing to see if can run fine and then retard if it determines the engine can't run well so far advanced? Does it monitor a/f ratio to determine knock? Does it monitor cylinder acceleration after each spark? How does it run better on 93 if was set up for 87? That's how I was thinking about it. I'm not just reading Internet articles that say "don't run high octane" I'm remembering what I learned in engine performance class at Lincoln tech and what me and a senior tech were trying to dig into on his scanner when he had a car running extremely rich one day when I worked at goodyear some years ago. But since I don't do this everyday I'm trying to gain some insight from those who do. Sorry for the long post.

Oh, I was using an Actron AutoScanner Plus CP9180 that does freeze and live data. I keep it with me :)


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[Galant306m]

8G knock sensor is located in the back of the motor. The sensor in the timing belt area is the crank position sensor.

pics or ban, the knock sensor is under the timing cover on the 4g64 in the block. I know the is a crank angle sensor in there too!


you guys are really looking at this to hard, gas is gas! 87 is perfect for the car to run on, if your car runs like crap "knocks" and feels more powerful then there is another problem with your car.

93 really isnt going to help any of you out on your stock engines, and having a cai with a cat back is STILL STOCK! Those are not huge performance items they bring about 2-4 hp at best and kill your low end anyways.

Please educate yourselves and quit wasting your time on gas that in the end is just a waste of money and resources!

[Galant306m]

http://www.genosgarage.com/GenosGara...irCleaners.pdf

Read this and tell me you think your air intake is a HUGE performance item cause really it isn't. this doesn't just apply to diesels and turbo'd cars it apply's to all cars.

[4g63lover]

I figure I'd see more of a difference at load but I can't really pay attention to the values and try to maintain a set speed to control this experiment and drive all at the same time safely. Like I said before, I ran 93 once and noticed no difference honestly but it was more of a seat-of-the-pants type evaluation. My thought process is, running 93 would burn slower, meaning the ignition would have to advance to take advantage of that, but if they set the base timing and all the other engine operating parameters on running 87 and it runs fine, how can the engine know it's running a higher octane if it was set up for 87? Does the PCM advance the timing to see if can run fine and then retard if it determines the engine can't run well so far advanced? Does it monitor a/f ratio to determine knock? Does it monitor cylinder acceleration after each spark? How does it run better on 93 if was set up for 87? That's how I was thinking about it. I'm not just reading Internet articles that say "don't run high octane" I'm remembering what I learned in engine performance class at Lincoln tech and what me and a senior tech were trying to dig into on his scanner when he had a car running extremely rich one day when I worked at goodyear some years ago. But since I don't do this everyday I'm trying to gain some insight from those who do. Sorry for the long post.

Oh, I was using an Actron AutoScanner Plus CP9180 that does freeze and live data. I keep it with me :)


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Honestly, I don't know how the 4G64 watches counts of knock because they don't even have an input to the ECU for it.

Though I would think the ECU would calibrate timing going off of the input from the Crank position sensor and o2 sensor values. If the o2 sensor sees either a low or high amount of oxygen leaving the engine I would assume it would adjust timing by advancing or retarding it to get to 14.7:1 A/F ratio. After all, if the burn is not complete within the time frame the engine wants to burn it in, the o2 sensors should think it is running lean or rich depending on how much oxygen it sees.

Please educate yourselves and quit wasting your time on gas that in the end is just a waste of money and resources!

I AM educating myself. I go to school 6 hours a day 5 days a week for this stuff then work on cars after. I'm not trying to say I'm an expert, after all I am still learning a lot of it but I study it and go off what I see at school and at work. I don't read it on paper then automatically assume it works.

I feel I am not wasting my money just by going off how the car feels. Call it my butt dyno, but I feel I am pretty in tuned with my own car to notice a difference when i drive it. We can argue this subject all day and come to different conclusions and disagree but I will still use 93.

and yes, here is the page from the service manual and I will post a picture of mine when I get a chance to take a pic of it.



BTW, you coming to the meet tomorrow?

[wetamup2k3g]

Honestly, I don't know how the 4G64 watches counts of knock because they don't even have an input to the ECU for it.

Though I would think the ECU would calibrate timing going off of the input from the Crank position sensor and o2 sensor values. If the o2 sensor sees either a low or high amount of oxygen leaving the engine I would assume it would adjust timing by advancing or retarding it to get to 14.7:1 A/F ratio. After all, if the burn is not complete within the time frame the engine wants to burn it in, the o2 sensors should think it is running lean or rich depending on how much oxygen it sees.

That makes sense, but I thought it only adjusted injector pulse widths to correct for lean/rich conditions reported by the o2 sensor. I appreciate the intelligent back-and-forth dude, you (and most the community at large here) know your stuff.

[Isaurio]

Knock sensor is behind the block by the oil preassure switch.
Here it is my 4g64 came with one


But the g ecu did not come with the option/wire.

The key is to tune the ecu every time u change a mod to the engine. Yes if u put a v6 tb and cai even headers is going to affect the ecu readings big time. There is more air coming in and the ecu dont know how to handle the extra load. U need to go and configure/tune the injectors, fuel maps atc to balance the extra air. 93 is the best gas if you running any type of mod plus a tune.