Hey, Whats the pros, cons and dangers of 120ron fuel in an fd? Both standard twin setup and a single turbo conversion? Cheers
Ha haa, some lad a mate of mine knows can get it. No clue where it comes from yet but seeing as these engines are the way they are, it would be a shame for him to use it and do harm. Or me on my engine too for that matter. Expensive stuff though
Woops, my balls up. 115ron race fuel.
Cheers, thats the bits I understand but how much of a benefit if any is someone going to see with using it? He\'s only talking about trying it out and not changing his map so I wasn\'t sure if he will see a benifit. To make use of the fuel, im asuming it would need to be re mapped. Could there be a negative effect if the car wasnt mapped for it?
If you put it in the car you will gain a few hp, might be noticeable.... Just. All turbo charged cars benefit from higher octane fuel whereas na cars don\'t.
I can\'t see there being any risk of using it in the car, it\'s like running your car on normal morisons petrol and then sticking vpower in it.
Also depends on the scotch level of the fuel. Look at E85, its got higher ron but you need to run more of it because the scotch value is lower.
LPG is the same, higher ron but lower scotch.
Shaun
Mmm, never come accross scotch level before. Well I couldn\'t speak for his setup but on a standerd system like mine. Could I push the boost up much with higher than 97 fuel? Currently it\'s about .7bar and from what I remember from reading, much higher and I will be putting the injectors under to much stress?
Is stoich a way of measuring the quality of the fuel, apart from the octane? That\'s prob a google question but is there a home kit style way of testing both these levels on the fuel I by, be it 97 or other? BTW there\'s no shell/BP garage near me to even trust that was getting good fuel :S
Quote from: leefitz;766659Hey, Whats the pros, cons and dangers of 120ron fuel in an fd? Both standard twin setup and a single turbo conversion? Cheers
ok lets talk about rotary engines, this way we can understand what benefits higher octane fuel can give.
what makes us different than piston engines, what allows them to run loads of boost on stock engines where we are limited to around 1.1-1.2bar.
Is it high compression, a 13b-rew has a compression ratio of 9.0:1, maybe even a little higher with the carbon build up filling the rotor chamber....but then look at modern 4g63 evo engine, that also has a 9.0:1 compression ratio and we have seen the boost pressures that run on pump fuel
so what is it thats holding us back.
HEAT
that is what limits and kills us.
so what does heat have to do with it, surely you have seen piston engines being pushed very hard under loads of boost and manage.
Heat is the biggest killer of any engine, with rotarys the issue that plagues them is called auto-ignition.
when fuel travels into the engine, at the point of compression the spark plug fires to ignite the fuel, this is all controlled by the ecu at a predetermined point in time safely.
auto ignition is where the fuel actually ignites itself before the spark plug gets to fire, as you can imagine you have the engine trying to compress the fuel/air and it then explodes, trying to push the rotor back the way it came, not saying auto-ignition will make you engine run in reverse but you see the problem.
also the explosion can put dents/pits in the rotor and break apex seals
now when you increase the boost, you also increase the heat, which in turn makes there a larger chance of auto-ignition, hence most people put a cap on there boost pressure to keep the turbo from working hard.
Now with piston engines, you map up to the point of det, then back off a couple of degrees of ignition timing and your done.
rotarys cant do this, because if you get them to the point of det then most likely you will blow the engine, so we have to tune very conservately at the cost of power.
so what can we do about this issue, how do we stop auto-ignition.
well there a number of ways to achieve this, but they all equate to the same thing.
change the ratio of temperature to fuel BTUs
what i mean by this is you need a wider divide between these two items to obtain more boost.
so you can either, reduce the heat entering the combustion process to stop the fuel autoigniting, or you can increase the octane of the fuel.
the higher the octane of the fuel, the slower it burns, this means that the fuel/air mix can withstand higher temps before it ignites, this gives you time to get the mixture to the spark plug to let it do its job.
2 ways to get more performance
1.
temperature control can be done by a number of ways.
first is a simple way, fit a bigger/more effecient intercooler....this will in theory drop the inlet temps of the air that in turn mixes with the fuel......the colder it is, the more temperature is required to heat it up to the point where it auto-ignites.
second is a fuel cooler, friction creates heat, when your engine is running your fuel pumps are pumping fuel down the fuel lines from tank to engine....if you dont use all that fuel(say your on idle) then that fuel is sent back to the tank...basically a big circle.
So you have a warm fuel pump, friction from the lines, entering and exiting a hot engine bay, maybe a hot exhaust right next to your fuel tank...you can see how it all adds up to warm up.
Decrease you fuel temps and again you will be allowed to add more heat(boost) before you start getting auto-ignition.
third is quite a common one, water injection......alot of people believe that it just cools the air down by evaporation and thats why you can run more boost.......thats only part of the story.
The second effect it has is by mixing with the fuel air mix.....as im sure you are aware, igniting water is not something thats easy, adding it to your mix then makes the the total mix much harder to ignite.....hence less auto-ignition problem.
2. Changing the octane of your fuel
this is obviously the subject of the thread but i think ive mostly covered it above.
running a higher octane fuel allows you to run more ignition timing/boost/temps due to its ability to withstand, this opens the door to more power.
now just because you have added this fuel into your rx7 doesnt suddenly mean your gonna make more power on its own.
How many times have you heard from people who have put 99ron fuel in there normal shopping trolly and claimed its turned it into a rocket car......well im afraid its total rubbish.
if your running a power fc for example, adding more fuel wont suddenly give you more power, infact it will actually cost you a little power due to the slower burn rate as you will still be running the same boost/ignition timings as before.
where the big gain is when you tune for the big window that has just been given to you.
increasing timing and boost pressures will give you more power and torque, how much more, well that depends on engine/turbo setup.
lee you asked about twin vs single setup on what you will get.
well you will get the largest gain on a single setup because most large turbos have an effeciency band of 1.0-2.0bar of boost and stopping auto-ignition allows you to access most of that.
twin stock turbos are only effecient from 0.7-1.4bar so even with race fuel and super cold inlets, the turbos themselves wont be able to give the engine anymore air.
What your looking for is to be like piston engines, your hunting for detonation, not auto-ignition.
sorry if theres an awful lot of waffling there, just typed it as it came into my head, there might be some stuff missing, ill reread it back to myself in a min and add anything i need.
Quote from: leefitz;766713Sorry man, that didn\'t come up earlyer for some reason. I dont have alota information about it but I\'m more interested in what the effects of such a high octane or av gas is on the engine? My engine is standard bar non sequential setup and knight sports ecu. I don\'t believe I will benefit with the higher octane but would my mate running a single turbo on PFC?
you would only gain if you tune for it, if not you can just use it to keep your engine super safe(say you were drifting/track work and wanted a massive threshold)
Quote from: rx7boy;766715Benefits of higher octane fuel
- reduced risk of detonation (leading to allowance for more boost)
- timing can be advanced to gain more power
- better fuel economy if mapped correctly
All lead to more power, however race fuel is not cheap and once you map for it, then you have to use it otherwise sticking lower octane will make your engine pop under boost.
very true........though most people map the 0psi+ transition upwards for the race fuel(assuming gasolene, not alcohol) so if you have mapped it on race fuel and just pootling to the shops then you will be fine on pump fuel.
Quote from: leefitz;766720Cheers, thats the bits I understand but how much of a benefit if any is someone going to see with using it? He\'s only talking about trying it out and not changing his map so I wasn\'t sure if he will see a benifit. To make use of the fuel, im asuming it would need to be re mapped. Could there be a negative effect if the car wasnt mapped for it?
not negative effect, maybe a little drop in power due to the slower burn rate
Quote from: Grant Monkhouse;766737If you put it in the car you will gain a few hp, might be noticeable.... Just. All turbo charged cars benefit from higher octane fuel whereas na cars don\'t.
I can\'t see there being any risk of using it in the car, it\'s like running your car on normal morisons petrol and then sticking vpower in it.
N/A cars benefit from high octane fuel as it will allow them to advance the igntion further without any detonation.
its just turbo engines allow ignition and boost to be increased so its a double whammy
Quote from: shaunwil;766743Also depends on the scotch level of the fuel. Look at E85, its got higher ron but you need to run more of it because the scotch value is lower.
LPG is the same, higher ron but lower scotch.
Shaun
very true, around 30% more e85 than gasolene to maintain the same lambda.
methanol is around 2.2 times the amount of fuel
No, stoich is short for stoichometric mixture. Its the ratio of fuel to air required for complete combustion. It doesn\'t tell you anything about the quality of the fuel.
RON is the Research Octane Number, its just a number to indicate how resistant the fuel is to detonation - higher RON means the higher the compression / heat of the fuel before it self-ignites.
So... higher RON fuel, means you can run the engine hotter / more boost - BUT unless the ECU has been mapped for this you\'ll get ZERO power increase. Some cars are mapped for higher RON fuels, and then they have an ECU that can sense detonation (knock) if a lower RON fuel is used and retard ignition accordingly - so they SEEM to gain power if you use a higher octane fuel, but the reality is actually that they LOSE power if you use a lower octane fuel - if you see what I mean?
The Rotary engine does not like detonation (bye bye apex seals) so is usually mapped rich to avoid detonation altogether - which means if it was mapped for 95 or 98 RON it wont know to push harder just because you\'ve put race fuel in it. If you mapped for race fuel and then ran 95 RON unleaded, you might find your engine sh*tting itself when you boost it.
Whoo, you men never fail to produce detailed and exstensive answers. Much appreciated. A really good read. I think from now on I will just add a wee drop of millers the my super in the drifter, just to be sure. And will pass all this info on to my mate too, no point in him getting fuel that\'s of no benefit to him.
Cheers lads