dingy

I will reply when i have read through this a little more.

Later Today.

AS for toluene, you get more advance from NF than 10% toluene mix BTW.

Plus using toluene on the road is illegal, and its really bad for your health.

Toluene is good tho, but you need a massive about of it.

As for OB not working, i think you will find most are very poor.

NF works, better than any other commercial booster on the market, proven fact.

Keeps oil temps down on track, along with exhaust gases. Plus raises the Octane of the fuel in ron not points.

Mycroft

The knock sensors reatard your ignition to a point where it no longer detects the knock, now when you reset your timing with (say) the EFI fuse trick, if the car fails to knock (due to being fooled) then the timing stays in its original Japanese spec. the same trick can be performed by shorting out the sensors between (on the Soarer) F3 and Earth, this tells the ECU all is well and the fuse trick need never be used again. The fact that the retardation mechanism is fooled does not mean that the stuff is necessarily doing anything other than that.

To anyone out there reading this, if you believe that any of those little bottles of stuff work for you and your car, then please continue to use them.

I do not want ANYONE to stop using anything that they feel is 'right'.

dingy

So are you basically saying the OB fools the Knock sensor ?

Mycroft

Yep.

dingy

Right, so knock is det and you saying OB hides det ?

Thats not possible.

Taken 2 engines apart mapped for 103 octane fuel using NF and SUL/optimax with no det on there at all.

I don't see how the knock of your engine can alter if its not knocking....

The fuel can't fool an electronic device that way.

Hugh Keir

Mycroft,

Knock sensors are microphones that are capable of detecting noise usually from detonation, but can be triggered by harsh engine noise, piston slap etc.

Knock sensors have no ability to adjust ignition timing. The standard Skyline ECU reacts to the knock sensor output by cutting the boost back to it's lowest setting for the rest of the run until the ignition is switched off.

The Apexi ECU that is used by many reading here only reports the knock value to the hand controller and to the engine warning light above a preset value and makes no ignition or other adjustments when knock is present.

Once knock starts, it takes a large amount of ignition retard to correct the problem, typically 10°. Knock is most commonly caused by excessive combustion chamber temperatures which knock only makes higher. Many systems having retarded the ignition by a large amount will then slowly allow the ignition to advance back to the standard setting. The trick is not to let knock start in the first place.

The EFI fuse trick you talk about is I believe similar to the system employed by Subaru. The ECU can be reset to maximum ignition advance by disconnecting the power for a while. When knock occurs, the map or overall ignition timing is retarded and that value will now be set for future or until the ECU is again reset, unless of course you short out the knock sensor ala Mycroft's procedure.

My advice is, get your engine tuned correctly and avoid the risk of blowing it up through melted / holed pistons.

Hate to disagree with you, but Octane booster does not fool the knock sensor, knock is either present or not, fooling does not come in to it.

TIM_H

1st post - new member here.

What a breath of fresh air- compared to all the other BB's i've been trawling lately.

What a fantastic thread - read every word with interest.

If this is a taste of what this board's got to offer, it'll be my main stopping point from now on!

keep it up.

Tim

Mycroft

Hugh as far as i'm aware ALL japanese Turbo'd motors have the Knock sensor signal to the ECU it is essential to retard the ignition to avoid this continual predetonation, the Skyline would be unique amongst all the performance Turbo cars in Japan if this was the case, I am fairly certain that you will find if you delve deeper into the ECU programming that the Circuit sys. 12a/**** will be the control wire, the ECU then retards the Ign. slightly to stop the knocking signal, it will do this using a load/fire reading taken from the crank timer.

The normal knock sensor on Japanese cars is actually quite basic, cant work much over 2000 rpm and as you say can even be fooled by internal noises that are nothing to do with pre-ignition, that is why rather than develope an expensive 'digital' device some manufacturers fitted 2, I have 2 on my Soarer, I have shorted them out, there is then no retardation of the spark due to this rather crude set-up, the best thing is to buy the latest generation of Digital Knock Sensors made by Nippon Denso, i have tried to buy the ones used on the latest SC430 but the signal from them is not compatible with my ECU.

pre-detonation is a 'growth' item, it bredds on itself, so the ECU works to retard the system next time the Lamda probe kicks in, and you are running 'normally' at that point the upper curve of advance is retarded, and this continues until the car no longer knocks.

I have just checked my files and all cars running OBD2 MUST have this function, and most Japanese cars with OBD1 had this feature too.

I tis easy to fool knock sensors, that is why the system can so readily be 'zeroed', if they were only rarely faulted then the procedure would be made more difficult.

Tim, you're right, this forum and the Soarer forum are the only ones to really debate things with serious intent. Both are great places to post and get real feed back from people who actually take a real interest in the'r cars, its not a 'Biggest spoiler (dick) wins' site!

Something I have just noticed too, this thread is getting rather a lot of 'hits' and will soon crucify the bandwidth restriction yet not a word of 'cool it' from the 'powers that be'. Respect.

Peter

Bugger, waiting for a reply for 2 days, go off 'air' for a few hours, I miss the reply and my thunder gets stolen!

The stock Skyline ecu does retard ignition when it detects det. by around 5 degrees I believe. It also lowers boost by way of the pcm boost solenoid near the fuse box. Both these precautions are reset when the ignition is switched off although the piston in the boost solenoid can become troublesome I'm told and does not always return from whence it came.

I'm still unsure about what function ob performs, whether it fools the det. sensors or reduces det. by way of raising octane levels, two schools of thought obviously. Precisely what form of testing was used to test octane levels with and without ob added to the fuel?

I still can't get my head around Mycroft's earlier post about the benefits of toluene and the comparatively enormous boost in power it gives, just doesn't add up to me. Why don't race teams use it instead of race fuel? How have you managed to run around for so long with your ignition overly advanced without suffering the consequences of det.?

Anybody got any views/knowledge about how Shell Optimax gains it's proven higher octane rating? There is no doubt that it significantly lowers det. compared with other SUL's. Is it just that, higher octane or does it include a form of ob?

Lastly, would Nissan really bother to put a det. sensor into a Skyline which 'cant work much over 2000 rpm'? Why bother since det. at that level of load it wouldn't be considered a threat to the engine anyway?

wsurfa

One of the guys I used to travel to work with used AVGAS in his track car -quite a lto as he had an arrangement with a bloke from Shell ;-). Did it for several years with no ill effects afaik, however his track car was a 1920/30's racing Bentley so that may have made a difference

Many racing organsiations stipulate use of 'regular' fuels hence the lower use of highly specialist fuels. Although I doubt F1 regular is the same stuff we get from the optimax pump.

cheers

Iain

nitro

All i can say is if higher octane fuel fools the knock sensor thats why you use the bloody stuff. Its pretty obvious that it reduces the detonation!!! Exactly the same goes for octane boosters as i certainly dont know what the difference is between high octane fuel and fuel containing octane boosters, same stuff !!! Thats what the fuel companies use seems pretty simple to me unless im a backward auzzie !!!!!!
If one is 98 octane and the other when a booster is added brings it up to 98 octane then can some please tell me the difference between 98 octane fuel and 98 octane fuel because this black duck dosnt know ?????????
They BOTH reduce detonation exactly what its ment to do !!!!
as if they didn't then why bother with high octane fuel and octane booster's in the first place.
If any one wants to start shorting out the ecu by mechanicly fooling it then you will get a guaranted result "look for trouble and you'll get it" the knock sensor is there for "YOUR" protection !!!
For those of you who think you cant possibly get an increase in octane from a small bottle DONT EVER BET YOUR LEFTY ON IT AS YOU WILL LOSE IT !!!!!!

__________________
When only the BEST will do!!

Peter

I'll resist the g'day mate!

What Mycroft is saying is that OB fools the sensors so that they don't register any det. but det. is still there and doing the damage.

I suppose an important point which Hugh made is if your car is set up correctly you shouldn't get det. anyway but on track when she's hot as hell and if your maps are setup pretty close to the line anyway, it can creep in which why I only use OB for track work now we've got Optimax.

Cheers.

Hugh Keir

The most contentious word in this thread is " fool ", as has been said by others above, Mycroft is suggesting that knock is still present but the high octane fuel is somehow masking this from the sensor which is not possible.

At the risk of repeating myself, detonation is spontaneous combustion of the fuel generated by temperatures or pressures in the combustion chamber that are excessive. It is the sound waves from the multiple flame fronts colliding that create the sound we call detonation.

When detonation occurs, all the energy from combustion that should have been released over the downward stroke of the crankshaft occurs near top dead centre, resulting in sharply increased combustion chamber pressure and temperature which softens the piston and the pressure blows a hole through it / traps the top piston ring etc.

Detonation will be stopped instantly by reducing the cylinder pressure which is why the Skyline cuts the boost.

Peters point about detonation creeping in on track days underlines the fact that his engine is experiencing higher than usual temperatures.

For Apexi users like Peter, they have the option of adjusting the “ high water temperature / ignition “ and “intake air temperature / ignition “ maps to control things, but it sure is tempting to tip in one of these bottles for safety.

Peter

Hugh,

You are correct about running hot on track, no problem on the road. I've seen water at 103 and oil at 130+ before easing off. She wouldn't make a 24 hour car for sure.

I've been thinking about upgrading the radiator, Rod had a nice big Apexi one when I was there.

Peter.