timing, to advance or retard?

[ESPER]

what does each setting offer? and how do u change the timing?

[s13sr20chris]

well you have...1)spark timing(ign. timing) 2)valve timing(cam timing)

spark timing is easy. there is a stock setting. advanced timing means more cyl pressure, higher wear, lower knock threshold, slightly higher output. it mostly offers a little more off idle snap which feels really good. advancing your timing is addictive, but it will blow your motor if you are not carefull.

valve timing is tougher. unless you know what you are doing just leave it stock or pay someone who knows. you will need a dyno.

[gyfer]

You turn your spark distributor to advance or retard timing.

Advance timing allow you have better respone and power curve throught out the RPM range. The power different is sometime noticeable at high RPM. Retard is vice versa.

quote:"Generally, advancing the timing will give you better throttle response and low end power along with improved fuel economy. Retarding the timing will reduce the chances of detonation and provide a safer condition for boosted motors or N2O motors."

quote:"Since many of you drive vehicles with an 86-octane requirement, yet run 91 or higher octane in the tank, there is some room for a power increase through more aggressive ignition timing settings. The key is to advance ignition timing right to the edge of detonation"

In rule of thumb, every 1 degree of advance timing, require next higher grade of octane gasoline. Means, if pretty safe to advance 2 degree timing, with 91 octane gasoline.

Detonation can happen anytime, even with stock ignition timing. To protect your engine, a lot of car came with knock sensor (to sense detonation/knock/ping) The ECU will retard the timing if it sense any.

For 240sx (at least for s13), the ECU do not do progressive timing.Which mean, ECU will only retard the timing when it sense knock.Some vehicle, like mitsubishi, the ECU will advance the timing for you until the ECU sense a knock. Thus, it will take advantage of the high octane gasoline you pour into your tank. Which also mean, advancing your timing wouldn't help much or don't help at all on these car.

Read around. I am sure you will find interesting information.

[s13sr20chris]

if you check out the ratio of hp increase to cyl pressure increase in response to ign timing advance it is seldom worth it to be right on the edge of detonation. rather stick close to the factory specs unless advised by a really good tuner(not joe bob at the dyno) like clark from jwt.

[ESPER]

hmm its hard to decide, one post says that it is good to increase timing, other says not worth it, what do i do?? hehe

[DAEDALUS]

It's unlikely you would blow the engine if your knock sensors are hooked up, but if you actually did blow the engine, would you have a plan B?

[gyfer]

plan B ?

first, you should ask yourself, why advancing the timing ?Have you done anything to your engine.... etc etc

Why dont' stay stock timing, and use 87 octane?Premium is soo expensive now. I wish my turbo is tune to run 87

[ESPER]

well, i always use 91 octane, i got the intake exhaust mods, simple stuff..

[gyfer]

well, i always use 91 octane, i got the intake exhaust mods, simple stuff..

hhmm... you might actually wasted all your money Because of not untilizing higher octance gasoline, you lost some performance, causing improper fuel burning, result in more carbon deposit and oxidation, which require more frequest oil change necessary, but you didn't. So, you end up with more engine wear. Your valve couldn't seal fully because of the carbon deposit, you lose cylinder pressure, result in more unproper fuel burning, and etc etc. ... Is not that serious, but this what it kinda happen. :pface :icesangel

Well, you should have just use 87. If higher gasonline price make you feel better, you can use 89.

[ESPER]

huh?

[crzycav86]

Running premium gas is a waste of money because you aren't utilizing it. In fact, I think running higher octane may actually hurt performance. The higher octane stuff is more resistant to combustion and therefore it burns slower. So it may be possible that not all the fuel was burned during the power stroke. This hurts both performance and emissions...

[s13sr20chris]

that is a lot of speculation there.

[ESPER]

look, all i know is that the ka24de manual says run on 92 octane or better, so i use 91

[gyfer]

This hurts both performance and emissions...

no doubt it will hurt performance*

http://www.caranddriver.com/ar...ber=1

*: Like i said, if ECU don't do progressive ignition timing (advance timing until it sense a knock), which will not utilize higher octane gasoline then factory recommended, you will suffer performance lost.

[crzycav86]

I see..

So my speculations had some merit. ..Actually I've read some things dealing with running premium gas on different forums.

When my dad went to get his '93 suburban to get smog tested, he asked the mechanic what kind of fuel he should use. The mechanic said to use whatever the factory recommended for it. So I suppose you go with that.

So the point is, if Nissan recommends premium gas, then it probably wouldn't hurt to use it.

[navysnail]

another thing, my friends dad works with bp on gas additives, ect...he told me that the middle grade has no chemical difference when it comes to engine performance. if you knock on 87 you will knock on 89

[ESPER]

crazy

[gyfer]

another thing, my friends dad works with bp on gas additives, ect...he told me that the middle grade has no chemical difference when it comes to engine performance. if you knock on 87 you will knock on 89

Your dad friend are damn right... but not fully.

Premium fuel does not necessarily pack more energy content than does regular. Rather, it allows more aggressive engine designs and calibrations that can extract more power from gasoline, because of higher resistant to knock.

In physic and chemistry, if you knock on 87, you will have lower change to knock on 89 PERIOD.

peace

[s13sr20chris]

lower energy does not mean lower output.

[gyfer]

Any fluid that contain less energy rating (BTU) , will result in lower power output. This is not argueable. Is physics/chemistry. How many energy can transfer from thermal energy (heat) to kinetic energy (acceleration) is another story.

87 and 89 octane rating gasoline have identical energy rating.

cheers

[s13sr20chris]

in a labratory environment you are right. inside a dynamic engine i am thinking that there are some variables to account for. less calories per gallon will lean out the mix. in the case of many 240s or any nissan with some age this will increase performance. the reason is that most nissans with any kind of age have a lot of resistance in the maf ground. this means extra fuel injected and rich running. so, what is better? depends. just think of the big picture; thats all.all in good fun eh?

[gyfer]

I repeat : " 87 and 89 octane rating gasoline have identical energy rating. "

No matter in labotary environment, or in whatever environment, any* octane rating gasoline has identical energy index(BTU). PERIOD.

There is NO "less calories" , that will cause lean out. Octane rating don't effect lean/rich !! Is the air fuel ratio !!

To be rude, if you can't figure octane, lean/rich, and air fuel ratio, I can see why all your car blowed up. :rolleyes You should spent more of your time in reseaching, not listen to some dude says "my mechanic told me... / my friend told me... "

no hard feelings. Cheers.

[cory2081]

oh boy. well, from many years of tuning turbo cars and N/A cars alike, i can say that using premium with advanced timing on an N/A car is worth it. You will yield better gas mileage and performance. See, just b/c 93 burns slower, doesnt mean that the car will all of the sudden run richer. A slower burn is a good thing as it gives the pistons more of a "push" than a quick hit. Keep in mind, we are talking very small time measurements here. 87 is for your lawnmower!! I've used 93 all of my life, never had any fuel system failure of any kind, never had high carbon deposits. Yes, 93 can possibly hurt your performance IF THE CAR ISNT TUNED FOR IT!!! I run my S14 at 25 degrees base timing using 93 octane and the car runs so smooth you cant tell it's idling (except for the rumble of the header and N1 single), I have better throttle response and more high RPM power. So, go ahead, experiment and see what tuning works best for your car and your needs. It even states in the owner's manual that the 240 runs at it's best when a slight knock can be heard ONLY under an extreme load (going up a steep hill at 45mph in 5th gear) Any questions?? Hope that this helps you!!

[gyfer]

owner's manual states the car will run in slight knock ?wow..

[s13sr20chris]

http://www.faqs.org/faqs/autos/gasoline-faq/part1/

"It is important to note that the theoretical energy content of gasolinewhen burned in air is only related to the hydrogen and carbon contents.The energy is released when the hydrogen and carbon are oxidised (burnt),to form water and carbon dioxide. Octane rating is not fundamentally related to the energy content, and the actual hydrocarbon and oxygenate components used in the gasoline will determine both the energy release and the antiknock rating."

i believe this is what you are saying. see you are correct. notice the word theoretical.

"The energy content of the gasoline is measured by burning all the fuel inside a bomb calorimeter and measuring the temperature increase. The energy available depends on what happens to the water produced from the combustion of the hydrogen. If the water remains as a gas, then it cannot release the heat of vaporisation, thus producing the Nett Calorific Value. If the water were condensed back to the original fuel temperature, then Gross Calorific Value of the fuel, which will be larger, is obtained.

The calorific values are fairly constant for families of HCs, which is not surprising, given their fairly consistent carbon:hydrogen ratios. For liquid ( l ) or gaseous ( g ) fuel converted to gaseous products - except for the 2-methylbutene-2, where only gaseous is reported. * = Blending Octane Number as reported by API Project 45 using 60 octane base fuel, and the numbersin brackets are Blending Octane Numbers currently used for modern fuels. Typical Heats of Combustion are [36]:-

Fuel State Heat of Combustion Research Motor MJ/kg Octane Octane n-heptane l 44.592 0 0 g 44.955i-octane l 44.374 100 100 g 44.682toluene l 40.554 124* (111) 112* (94) g 40.967 2-methylbutene-2 44.720 176* (113) 141* (81) Because all the data is available, the calorific value of fuels can be estimated quite accurately from hydrocarbon fuel properties such as the density, sulfur content, and aniline point ( which indicates the aromatics content ).

It should be noted that because oxygenates contain oxygen that cannot provide energy, they will have significantly lower energy contents.They are added to provide octane, not energy. For an engine that can beoptimised for oxygenates, more fuel is required to obtain the same power,but they can burn slightly more efficiently, thus the power ratio is not identical to the energy content ratio. They also require more energy tovaporise."

i believe this show that there is some variation from formula to formula and even batch to batch.

[s13sr20chris]

"4.13 What is a typical composition?

There seems to be a perception that all gasolines of one octane grade arechemically similar, and thus general rules can be promulgated about "energy content ", "flame speed", "combustion temperature" etc. etc.. Nothing is further from the truth. The behaviour of manufactured gasolines in octane rating engines can be predicted, using previous octane ratings of specialblends intended to determine how a particular refinery stream responds to an octane-enhancing additive. Refiners can design and reconfigure refineries to efficiently produce a wide range of gasolines feedstocks, depending onmarket and regulatory requirements. There is a worldwide trend to move tounleaded gasolines, followed by the introduction of exhaust catalysts and sophisticated engine management systems.

It is important to note that "oxygenated gasolines" have a hydrocarbonfraction that is not too different to traditional gasolines, but that thehydrocarbon fraction of "reformulated gasolines" ( which also contain oxygenates ) are significantly different to traditional gasolines."

good stuff.

[ziggy682]

Guys, haven't you ever noticed what is says inside your gas door. Well, inside mine, it says "Premium Fuel Only". This is on a 91 S13. I always use premium, and it would still occassionally knock during the summer in Texas with stock timing. I can't imagine using 85 or 87 octane in our cars. One time, I put half a tank of 87 octane to see how it ran. I probably lost 20 hp, because the engine was pulling back timing so much from the crappy gas. Now, I know my car is probably a bit too sensitive to what kind of gas I use, but Nissan does reccommend premium fuel.

[Peabody]

I can only run 91 or higher in my s13. My 1st mod in 1993 was a computer chip that remaped the timing. I had to send them my computer and then they sent me theirs. They told me I CANNOT use low grade gas.When I first got the car in 1990 I could use the low grade without any problems. I tried the 89 octain anyway when after I got the chip and it did ping so I always use the 92 or 93. Can I still manually increase the timing a little more? I know the chip does it, but if I can gain more HP and better mileage then why not. THANKS

[gyfer]

good stuff.

Yes, it is. Are you tyring to point out what I say is true ?

[ESPER]

wow lots, of technicalities........ does anyone ACTUALLY use 91 which advanced timing for a while now and had no problems? if so, how far have u advanced your timing?