NZConvertible

This is a misleading statement. It's not whether the secondaries are on that's relevant; it's how much power you're asking for, i.e. your right foot.

Say you're in 5th gear on the highway at a constant speed, and the secondary injector switch-on point id 3800rpm. You will obviously use more fuel driving with the engine at 3900rpm (88mph) than you will with it at 3700rpm (83mph), but it's not because the secondaries are now firing, it's because you need ~17% more power to do it. The same is true when comparing 3600rpm (81mph) and 3400rpm (76mph), even though the secondaries aren't on at either speed. (Speeds are for an S4 TII.)

No, it doesn't work like that at all. When the secondaries come on all four injectors fire at half the pulsewidth the primaries were firing at just before the transition. There is no sudden jump in the amount of fuel injected or AFR.

The only emissions device that affects mileage is the cat, and removing it can slightly improve mileage because the reduced restriction means less engine power is required for same performance. The rest of the system just adds air to the exhaust to reduce emissions, it doesn't affect how the engine runs.

No you didn't. The O2 sensor is only used during light-load cruising, no other time. As soon as you put your foot down it's ignored.

If you're not prepared to learn something new (and your posts prove you really need to do some learning), then you're already wasting your time just being here. Do yourself a favour and do some reading before posting any more on this thread so youdon't look quite so ignorant.

No, it's completely invalid. The octane rating has nothing to do with the energy content of fuel, so burning the same quantity results in the same power regardless of octane. If you weren't so lazy and had read some of the info you were given you'd have already learnt that.

s4Lt

Yeah sure, why not **sarcasm**

RotaMan99

NZConvertible

You actually think that's not right? Are you trying to make yourself look completely ignorant?

so-mars

dunno trying to wrap my head around the issue w/i the context of what other people are saying...

and from what peeps are saying it seems to me that i get a 'stronger kick' out of 93 because i can press on the gas pedal and i guess from what you are saying there's actually latency introduced into the system for the fuel to ignite... so a bit more fuel gets punched in between when you hit the accelerator and it ignites or whatever it does. probably a matter of 200-300ms delays or something but i do audio engineering stuff so am pretty tuned in down to about 2-8ms (well that and computer games and 2ms latency tft screens versus average 80ms latency lcd or sometimes up to 130ms latent vga cable to old crt monitor, which is more than cable modem latency is so its obviously a huge effect)

as for shell gas... the 'boutique' gas or however the refer to it is the 93 and that's what they put the most alien stuff into but yeh i guess if you guys say 89/91 also has detergent then its just the specialized stuff is in the premium 93

wikipedia has a chemistry explanation of octane but i couldnt really read it

from reading this i do get the idea that w/ 93 theres a bit of delay and subsequent more 'seeming kick' when the gas blows heh

quiet before the storm

RotaMan99

The same amount of fuel is being delivered. There is no fuel being injected when there is combustion, the injectors have already injected the amount of fuel they were supposed to inject into that one chamber. Don't be compairing computers to engines. Its like compairing Mars to a tree here on earth.

Huh, so, if this is true, which its not, what Special stuff do they put in?

Then don't try to give advice in this topic.

I give up!

RotaMan99

I think the one closest to the oil filter is where the fuel filter line goes. I could be wrong, its been years since I have had that nasty metal rack on my engine. Try looking under the intake manifold from the front of the engine and from the drivers side with a flahslight and see where it goes.

NZConvertible

No, it actually burns slower. There is no delay and there is no "kick", and anyone who claims that or thinks their car is faster just from using higher octane fuel is imagining it.

As has been said several times (not including what's in the links provided), octane rating is simply a measure of resistance to detonation, so higher octane allows more boost and/or more advanced ignition timing. Those will give you more power.

Seriously, if you guys aren't prepared to read and learn, you shouldn't be making wild guesses and nonsense claims, and you certainly shouldn't be arguing about it with people who have bothered to learn.

so-mars

sorry neither of you two guys sound like you have a clue because you are contradicting yourself

it cannot burn slower w/o altering the timing and amount of fuel in play after injection, the two are mutually exclusive


unless of course you are saying that fuel disappears into a vacuum (probably one like your brain)

NZConvertible

You really need to go do some more reading on the subject. This has nothing to do with the amount of fuel injected, but does affect the ignition timing you can run. The higher the octane, the more heat energy is required to ignite it and the slower the flame propogates through the chamber during combustion. These two factor lower the chance of pre-ignition or detonation, and also allow the spark to be fired earlier to improve combustion efficiency.

Good to see you can contribute to a technical discussion a mature manner, rather than resort to childish insults...

RotaMan99

crap I just noticed my post above about the fuel line is in the wrong thread... oppss

so-mars

the other guy was being rude *shrug*

what i'm saying is that when you punch the accelerator, there is a SLIGHT delay before the fuel ignites and flame propogates w/ higher octane gas

meaning there's essentially a 'virtual time vacuum' introduced into the entire system that could cause it to seem like it has more PUNCH in the first say, second or so

then after that, negligible... (apparently)

which is exactly what i was saying before, but do you understand what i am saying now so you don't jump on my back for trying to go 'logical gating' on other peoples intellectual property? as IT systems architect i organize other peoples IP for a living

RotaMan99

Me? Good.

chinkst3r

iTrader: (5)

wow, this simple thread has developed.... so whats the safest octane you guys are running on your T2s? i just fixed my exhaust leak, and all seems to be good so far, getting 16-17 MPG...

unW7WZ

lol, i run 87 (need to be running 89 or 93, cuz i boost creep bad, and i dont wanna grenade the engine).

NZConvertible

So be the bigger man.

You're looking at two completely different time scales and not understanding the difference. You're talking about a one second on time, I'm talking about at even that takes milliseconds to occur. At say 2000prm when you "punch it", in the second you're talking about 33 combustions events have taken place (more if you accelerate in that time), all with about the same flame propagation speed.

RotaMan99

^ I was hoping you would clear that up. I needed to learn a little myself at this point.

so-mars

btw... i am running with 89 now instead of 87 or 93...

and i can tell what you mean about it being tuned for 89


def would go with the 89 for best performance

RETed

Uh...no.


-Ted

ericgrau

iTrader: (1)

I'm chuckling at the unrelated debates here. And the more unrelated the more misinformtion it contains.

Best option for mpg and other problems is keeping everything in shape. I get 24-25mph @ 85mph. I made sure to get a good '7 and do all the maintenance. And I got a lead foot. For best mileage, shift when your shift light says so; that's what it's there for.

octane: I'm only answering this particular side debate b/c it affects how much you spend on gas, which is why you want good mpg anyway. Octane equals knock protection. Octane ONLY equals knock protection. Better knock protection means a better safety net for high compression and high boost. Higher octane gas contains less energy, meaning both your mpg and power will always be lower. But it's better than knocking. A lot of high performance cars can't live without it. But it won't boost the performance of any car (see video below). Your car doesn't knock? You're wasting your money. Your car knocks? Is it an N/A or unmodified turbo? Fix your car before you blow your engine, high octane is just a band-aid here.

Here's an example to illustrate:
http://www.youtube.com/watch?v=Njno_9UoRZc

chinkst3r

iTrader: (5)

lol, eric this thread is so old... how'd u find it? well neways, u drive an na right? haha im talking about mpg for t2's...

RETed

It wasn't ericgrau's fault.
so-mars resurrected it again - check the date / time stamp.


-Ted

ericgrau

iTrader: (1)

Oh, then buy an N/A :P. Anyway, small world. See you at the BBQ. I'll get there quicker b/c I'm not stopping for gas, hehe.

chinkst3r

iTrader: (5)

LOL fo sho, hey are u still bringing wood?