Running Skyline on low octane fuel

[Duncan]

My understanding is that Rb25s, and presumably other skyline motors have knock sensors in the block. When the stock ECU detects knock it retards timing, reducing power and preventing further knocking.

Is my understanding correct?

Specifically, I've got a long trip coming up and don't expect to find anything better than PULP (95), and I may even have to use 91 at times.

[strutto]

Thats how I understand it Duncun...

The question is, can the ECU retard the timing enough to prevent detonation under high load and high temp conditions?

I'd try for 95 as a bare minimum and avoid putting it under too much load...

HTH

[dangerous_daveo]

Maybe get some octane boost as well, just incase.

[strutto]

Maybe get some octane boost as well, just incase.

Good idea daveo but don't use that Nulon or STP stuff. Do it properly and use some Toluene...

Not to sure how keen you are on carrying a 20L drum of Toluene with you though Duncan?

[Kinks]

nulon is the only one that actually works..

http://www.angelfire.com/mb/southo/Octane.html

or

http://www.fbody.com/members/stevenmh/Fire...ane_booster.htm

or

http://members.rennlist.org/951_racerx/Oct...Comparison.html

(I think they all quote the same test results).

Toluene is way too much hassle IMO.

[MINES_DATSUN]

well , using octance 95 on my rb26 is bad . im not sure about the RB25 series.

i can feel less torque with 95 then the regular 98 i use daily!

[Duncan]

Thanks all.

Yeha strutto, I guess thats the problem....it will be hot and it will be under high load. I'll turn boost down to stock but it wasnt too high in the first place.

And of course highly flamamble 20l can in the back isnt my idea of fun either

[meggala]

try redarding your timing a bit b4 you go say 10o it should help ore make a note of both positions normal and 10o and if you need to low low octane then move it back 95 houdl bo ok if you dont have the boost wound up

meggala

[hippy]

i've been using shitty petrol for a couple of weeks now ... i find the theres less power .... not that much ... but i've found it a little strange in that the car still runs smoothly and my feul economy is slightly better in that using 98 ron i was getting just over 400 ... but using 91 ron i'm getting 450+ ... i've got a pod and full exhaust on an auto ... so i'm not too sure whats going on LOL ...

before i had a dump pipe my economy was

91 ron - 350-450k's

95 ron - 450-500k's ... usually very close to 500 so thats what i used.

98 ron - 350-400k's

strange huh?? anyways i can't run 95 ron with the full exhaust cause the bp that used to have only has ultimate.

my question is ... will a SAFC correct whats going on and let me get the same or better mileage ie 500+ k's of a tank using 98 ron??

[Duncan]

hey meggala at the risk of hijacking my own thread, how do I retard the timing?

My understanding is that the only effect of retarding the timing is producing less power?

[blind_elk]

I did a trip last Easter Melb - Bris - Syd - Melb - Adel - Melb. At times, I could only get PULP. I ran some Nulon OB as well, as a safety precaution. But I would think that under general highway cruise you shouldn't be loading the engine so much that you could induce knock. These things run like 40 deg advance on cruise, I believe.

[kjb_r33]

retarding ignition timing by the crank angle sensor also retards injection timing (not overly good if your after economy). If the knock sensors dont retard it enough to stop any damage occuring you will hear it pinging, back off. Ideally, if PULP isnt available then use an octane booster, but keep in mind it only raises the octane rating a very small amount.

[hippy]

what does pinging sound like?? cause when i step on it i hear a really high pitch sound which i've always assumed was the turbo spinning ... goes like ... ZZZzzzzeeeeeaaaa!!!

[franks]

just start worrying about your fuel when you hear a ping ping ping'ing sound coming from the engine dude otherwise, keep turning up the boost

[hippy]

so can anyone give me a better discription than "ping" ??

[franks]

so can anyone give me a better discription than "ping"  ??  

lol..sorry dude, i should've put my 2c forward - pinging sounds like shaking a tin can filled with nuts and bolts ...

wether this be the case of "zzzeeeeaaaaaaaa" i would hazard a guess thats either a) induction noise or B) your turbo

[hippy]

yeah i was thinkin it was induction and then the turbo ... but someone told me something and i was a little worried it could be a ping at the end LOL ...

[Duncan]

sweet. thanks all.

[meggala]

as said adjust the crank angle sensor should do it

and your a typical race car driver.

[druzilla32]

as said adjust the crank angle sensor should do it

and your a typical race car driver.

My engine is pinging.

I did an ecu test and came up i got a fault in my knock sensor.

Can i prevent further pinging by retarding the timing more?

do i turn the CAS anti clockwise?