Oh ok, so does a higher octane mean cooler intake charge? I was under the impression timing was adjusted for colder air that would allow more fuel. But still I think the end result could be the same, more power without having to adjust timing and not having to worry about hurting the engine.

Nah, here's the quick and dirty. The octane rating of say gasoline, whether its 89 or 93 or whatever refers to how easy the fuel is to ignite. The lower that number, the easier it is to ignite.

When you have a car that is tuned for high performance, whether its high compression or boost or even just a lot of stress from driving on the track; that causes the cylinders to get really hot. Hotspots are created at different locations inside the combustion chamber. All that heat can cause the air/fuel mixture that you car burns to ignite prematurely. That is NOT a good thing, it creates a lot of stress on all the components and if done repeatedly will lead to engine failure. This pre-ignition is called pinging, knocking, detonation, etc. Its all the same thing.

So to battle this premature ignition problem, you can make the fuel mixture harder to ignite, that way it wont ignite before it is supposed to (when the sparkplugs fire). That is the purpose of running race fuel with higher octanage and of injecting methanol or water into the mix. It just raises the octanage, making it less likely for premature ignition to occur.

So race gas/meth/water will NOT give you more power, it just allows you to run a bit more boost or squeeze a little bit more performance out of the car. Because you can run more boost (in our case) then you can make more power without knocking. Of course in forced induction applications, that "little boost" can be a few more psi which can mean as much as 50whp+ over regular gasoline.

FYI, the leading cause of detonation is leaning out the air/fuel mixture. When you lean out, you are running more air in the mix than you should be. The more oxygen you have to burn, the more power, the hotter your cylinders get. So when you lean out, chances of knocking increase dramatically. Thats why they say its safer to run on the rich side. (rich = more fuel). So when someone says their AFR is 12. There are 12 parts of air per part of fuel. SO if you say your AFR is 15, then you are running comparatively more air, therefore leaning it out as compared to running the same car at 12.

So no, its not cooler, its just safer. I run 50/50 mix of pump gas and race gas at the track every time to ensure that my car isn't detonating

Thanks, that makes sense, so has anyone with a fully mooded out "Z", ie. CAI, HFC, CBE figured out if we are running too lean yet? I know when I first got the car my tail pipes would get some black junk on them and since Ive gone to my CBE and K&N drop ins, no black junk so Im assuming Im leaned out a bit but hopefully not too much.

Yep, intake and exhaust will lean you out. I had every bolt-on and took it to the dyno to get tuned. It was running a little lean, but nothing to be alarmed about. Now after the tune I have everything smoothed out, no lean spots and the power curve feels completely smooth.


Going too lean makes you lose power too, so you have to get it right at the sweet spot where its safe and it makes as much power as possible.

actually i was going to mention something to stillen about this but forgot about it until now. Most efficient way of using co2 in a water to air setup = tank bubbler. Think stainless co2 bar submerged in the inercooler tank just have to make sure there is enough antifreeze in the mix to keep it from freezing ;)

Edit forgot to mention that this way it is a direct cooling effect from the gas to the liquid instead of having to go through the metal of the cooler, and it contains the cooling effect of the co2 to the water more. I'd insulate the tank, and make it a good bit bigger then the one in the previous photo i saw, to maximize the time after each burst of co2 before the water would heat soak again. You would have to come up with a vented reservoir with a kind of catch can to keep the coolant in but let the co2 out as you would want the gas to flow directly through the water instead of just using an expansion chamber in the tank(think a/c evaporator) for the greatest cooling effect

man as hot as our engines get I might just use that new water to air intercooler by itself they are developing for the SC just to get air temps down, but it would prolly be expensive if they would ever sell it seperately.

RCZ,

I repped you for a great explanation, though I'd like to make one relatively minor correction.

The water/meth does not effect the octane rating of the fuel (also as a side note, the "octane rating" is also not the same as the "octane" of a fuel, which is a specific molecule within the fuel), though it does cut down on premature ignition. The water/meth works by increasing the specific latent heat of the air/fuel mixture, i.e. it cools the mixture. As the mixture heats up during the compression stroke, if the mixture gets too hot it will self-ignite (ping, knock, whatever you want to call it), which is the same method of operation for a diesel engine.

To add to your excellent description, one of the causes of premature ignition (the hotspots you mentioned) are usually caused by carbon deposits on the piston head. As the engine puts on miles, carbon deposits build up, so it behooves people with lead feet to throw in some deposit cleaner every 50-75k miles to keep the buildup level minimal.

^ Excellent, thanks for the correction man. Good to know! I'm learning like everyone else :)

Rep to you as well.

nice explainations :)

That's why I love the Z community!!! Thanks for your response. I have continued to do research on this topic, which is how I got back to this thread.

The ideal temps for intake air, and oil aren't close enough to make this a good idea in my opinion.

I still have alot to learn as I did not know this and had'nt considered it as a factor. Changes my thinking radically!! I will have to rethink my approach.:tup:

Good points!! Guess I still have alot of research to do....lol

These are interesting ideas that I will definately look into. Thanks!

Now that's interesting!

Many TT'd exotics are running something similiar to this type of set-up.

Not to make a segway or derail the thread, but since it's talking about Intercoolers, and very in depth I might add. (My intercooler IQ just shot up 30 points thanks thos this thread lol) I figured this might be the best spot for my questions...

I've seen different SC/TT setups for the 350/370Z on this forum now and have noticed some use a single Intercooler for both -chargers, and some use a seperate intercooler for each side. My questions are:

1. Does this even matter using a seperate Intercooler for each side vs. a single Intercooler?

2. If it does matter, which is better, 1 big intercooler feeding both sides, or 1 seperate one for each SC/TC?