Skyline GTR octance minimum

[koh]

What is the minimum octance level for a Skyline GT-R? I heard from some that it's 100 (lucky japanese has better gas too). I want to find out before i consider getting one because I heard if you use 92 with performance mods it would mess up the engine.

[adamandsonja]

my stock gtr 33 had problems with australian premium unleaded which is 95 octane. we have recently been able to get 98 octane easily. if u use 92 octane u will HAVE to use octane booster from a reputable manufacturer.
adam

[R33]

Hi Koh, the GTR, like all Japanese cars made for Japan, is optimised for the Japanese high octane fuel (100 ron -or is it 101?). Anything below 97 ron may result in problems. Especially when you have up-ped the boost from stock. The lower octane fuel does not burn like the 100 octane fuel - under extreme pressure and heat it explodes (detonate) rather than burn. A detonation for a few second is enough to destroy the engine.
I use a cheap concoction with the 97 octane fuel for daily drives. A big intercooler also helps as it reduces the intake charge temperature thus reducing heat and providing more oxygen. Another option is to install a water injection system to further cool the intake charge and provide more oxygen. Of course another option would be Nitrous

[koh]

So i can run NOS constantly and nothing bad would happen? And can a intake alone take care of the problems?

[koh]

ANd don't new cars have this special programing chip that automatically changed tha engines configuration and stops detonation (teacher told me, he said 5 years old though, and I'm thinking about a 95)

[Moppie]

All the imported GTRs here seem to run fine on 96.
No you can't run NOS all the time, and since it rasies the Dynamic compression ratio you really need to run higher octane gas with it, so its not an answer to this problem.
Pretty much all Japanese cars (and the rest of the world for that matter) made after 1990 have knock sensors. These detect the sound of knocking and retard the timeing, and/or richen the fuel mixture through the ECU to compensate. The result is that running on low Octane US gas you may not be making as much power as if the car was still in japan, (but who really cares).
Of course people wouldnt be importing them if they didnt run on lower octane gas, so I wouldnt worry to much.

If your are really concerned, then a bigger intercooller, (altough the GTR's is already pretty damn big) may help a little and lowering boost with a boost controler will definitly help.
Water injection is an option, but it would be expensive to setup on a GTR, and you have to remember to keep filling the water tank, besides there's no proof that it will always cure engine knock.

[koh]

thanks for all your responses, i'll go check out how much are those stuff. thanks alot, you don't know how much you helped

[adamandsonja]

fact: the gtr's knock sensor only works up to a certain rpm - 3000 i think.
fact: gtr is designed to run on 100 octane fuel, 92 will cause detonation.
fact: i own a gtr that detonated (while standard ie. no engine mods or boost increase) when running on 95 octane aussie fuel.
fact: detonation will cause serious engine damage.
fact: retarding the timing is a bandaid remedy.

if you cannot get at least 98 octane fuel put in some octane booster, it is not worth the risk of damaging a piston etc.

moppie do you have a gtr?
adam.

[R33]

I agrre with Adam here. Not worth the risk of pre-ignition and detonation. I run my 33 on 97 ron and it's okay at 1.02 bar. But I have a huge GT i'cooler. For daily drive, I normally use my mechanic's concoction to boost the octane rating. On track, no option....always use the HKS booster.
On NOS, I think a very mild dosage of NOS would help and could be used daily. I think NOS is ok if you use it to help the fuel burn more rather than using it in huge quantity to produce 50-100 or more horses...in that case it might hurt the bearing and even the pistons after some time.
Water injection has been used quite extensively to prevent knocking. Quite expensive to install one in a GTR though.
Big i'cooler will help if the fuel is not below 96 octane.

[Moppie]

Originally posted by adamandsonja
fact: the gtr's knock sensor only works up to a certain rpm - 3000 i think.
fact: gtr is designed to run on 100 octane fuel, 92 will cause detonation.
fact: i own a gtr that detonated (while standard ie. no engine mods or boost increase) when running on 95 octane aussie fuel.
fact: detonation will cause serious engine damage.
fact: retarding the timing is a bandaid remedy.

if you cannot get at least 98 octane fuel put in some octane booster, it is not worth the risk of damaging a piston etc.

moppie do you have a gtr?
adam.

Yes but your running on EXTREMLY low quality Ausie fuel, the same crap that forced Subaru to creat a special under powered version of the WRX for the Aussi market, after to many of the old model cars destroyed themself's.
I find it hard to belive that the knock sensor would stop working above 3,000rpm, there would no point in having it, since most engine knock occurs at high engine RPM.
I dont own a GTR, but there are certainly plenty of them running around on NZ roads, and most have been modded in some way, and run on 96 with out any trouble what so ever.
These cars are also being imported into the states in limited numbers, and Iv yet to hear of any having trouble.
A fuels Octane rateing is a poor indicater of how it will preform in the real world, the actual chemical composition has far more to do with how it will behave in a street engine. For example a leaded 96 octane fuel will resist knocking far better than an unleaded 96octane fuel.

[adamandsonja]

quote from autospeed article on knocking
"The ability of a fuel to resist knock is specified by the fuel's octane number. A fuel with a high octane number is more knock resistant".
From personal experience loading up the engine also induces pinging, even at low rpm!

the subarus that destroyed their engines were actually sti's, all were damaged on either racetracks or after periods of sustained high speed/ load driving ie. street racing. these cars didn't have their ecus altered, and were designed to run on japanese 100 ron fuel.

the standard aussi wrx (155 - 160kw) was also supplied to other markets, japan likes to keep the "hot" stuff for themselves.

i cannot comment on leaded fuel as it is totally unsuitable for a gtr and i've never used it.
adam

ps. maybe specifically ask some gtr owners if they have had pinging on anything less than 98 octane fuel - i'll bet yes.

[R35]

FYI: MotoRex (the ONLY US importer for the Skylines) change the ECU as one of the many different things they do to make it US streat legal so there should be no problem running cars from them at the lowe octane. This is not necessarily true for a stock.. any car from outside the US.

Since all cars that are legally imported into a country get modified to meet the standards of THAT country, most of the time it doesn't mean much when comparing a car in one country to another.

[Moppie]

The Currtent model WRX as supplied to the Aussi Market is a detuned Version of what is sold in Japan, NZ and the UK. It runs lower boost, has a lower compresion ratio, and diffrent ECU mapping to cope with the lower quality Aussi fuel. (source, Motor, Autocar, NZ Driver).
The STi is sold all over the world, and has been for some years. (it was the ADR that prevented it being sold in Aussie, thats why your getting the EVO VI while the rest of the world is getting the EVO VII)
The WRXs that destroyed themselfs in aussie were engaged in all mannor of driving situations, and the problem was bad enough that Subaru took measure to prevent it happening, after the cars were repaired under warrenty they had a diffrent ECU fitter that reduced power. (why do you think the new model WRX is slower down the 1/4 in aussie, but faster than the previous model everywhere else.)

When a the Octane rating of a fuel is measured it is done on a special test engine, that runs at very low RPM, and using a special head desgin that allows the compresion ratio to be adjusted while the engine is running. Its only a single cylinder engine, and does not provide anything like a real life driving simulation.
The engine is run and the CR is increased untill knock is detected. From this the Octane rating is calcutated. However it fails to take into account things like changes in the Dynamic compresion ratio of an engine, and only serves as a rough guide to the fuels ablity to resist knock under a static compresion ratio.
Hence when Lead was removed from NZ 96 octane fuel people with cars requiring a higher octane fuel reportred huge probelms with engine knock, (I was one). The lead in leaded fuel works very well at controling detonation, as it has a very high flash point and burns very slowly. However with out the lead in the fuel Tolulne was used to bring the octane rating up to 96, this resists knock well enough on a test engine, but in the real world is a very poor subsitute for lead. It has a lower flash point, and burns a lot faster. It is also very corrosive, and it took sometime before the Tolulene levels were reduced and other compounds were used. Australian fuel however still uses very high levels of tolulene, compined with huge distances accross which it is transported. Go ask a tanker driver about load loss over even a 100km trip, literaly the lighter compounds in the fuel, which are also the octane raisers will evaporate off very quickly, and so lower the fuels octane rating between when it arraived at the depot, and when it reachs the pumps.
In New Zealand even heavily modified GTRs have no trouble running on 96 octane fuel.
And we get a faster version of the WRX.

[R33]

Moppie, instead of lead or tolulene, can Metahnol/Methane be mixed with 97 ron fuel to prevent detonation or pre-ignition? I think it's used for race cars with high compression.

[adamandsonja]

do you understand that australia has recieved both the sti and the wrx - ie. the same car that great britan got as the impreza 2000 turbo ?