Retard timing verses high octane fuel
Thread Starter
TECH Fanatic
Joined: Nov 2001
Posts: 1,705
Likes: 0
From: Iowa :-/~
Retard timing verses high octane fuel When shooting bigger shots of nitrous I understand why we need to retard the timing but why not just use 104, 110 or 118 octane fuel instead? I know the obvious...cost! But what if a separate fuel cell was used for the fuel that goes to the wet side of the nitrous kit? This would keep the cost down you would gain more power from not having to retard the timing. What do you think? Why don't more people do this?
Re: Retard timing verses high octane fuel I think its a great idea. The reason you dont see it alot is probably cost and space for the tank, pump, lines, and regulator. I have seen it several times on serious "track" cars. I say go for it. Also watch out for the high octane fuel. I believe most fuels much over 100 octane are leaded. Not good for O2 sensors. Although if you had a small tank as you said...and were only running the really high octane leaded stuff through occaisionally, which would be mixed with unleaded in the combustion chamber.....I wonder how badly that would adversely affect the O2 sensors? Hmmmm.
Even with high octane..depending how large a shot...at some point you may still need to retard timing.
Even with high octane..depending how large a shot...at some point you may still need to retard timing.
Teching In
Joined: Jan 2002
Posts: 10
Likes: 0
From: Elgin, Illinois
Re: Retard timing verses high octane fuel It is my understanding that high octane fuel is used because at high compression ratios, fuel can burn too fast (knock). Nitrous burn is more complicated. I think that it does burn faster, but I think it also burns longer. High octane fuel is recomended for nitrous use, but I do not think very high octane will do as much as retarding timing will do. Using nitrous, we need to insure that we do not get too much combustion pressure prior to TDC. I have seen dyno sheets showing more power on nitrous when some advance is taken out. I have a 1K resister that is wired into my arm switch so that the IAT shows a high temperature, and this pulls 3-4 degrees of timing out.
TECH Enthusiast
Joined: Nov 2001
Posts: 617
Likes: 0
From: Milford, Ohio
Re: Retard timing verses high octane fuel 2000 C5 is right. I made a similar post in the other thread on this, so hopefully between the two of them I will make some sense. Retarding timing when using nitrous is not done in an attempt to avoid detonation, and as such the same result cannot be achieved by simply using high octane race gas. Nitrous acts as an oxidizer and lets the motor burn more fuel durng a combustion cycle. It does this by increasing the burn rate of the fuel mixture. Ideally in any situation, you want to achieve your max cylinder pressure a few degrees after TDC, as the piston is starting downward on the power stroke. This is why more timing is not always better once you reach a certain point. Having cylinder pressure peak prior to TDC is very hard on the bottom end of the motor and robs power being made in the other cylinders b/c the piston must overcome all this pressure to pass through TDC and start back down. When using nitrous, the combustion rate is much quicker and timing should be retarded so that cylinder pressure does not peak to early.
Thread Starter
TECH Fanatic
Joined: Nov 2001
Posts: 1,705
Likes: 0
From: Iowa :-/~
Re: Retard timing verses high octane fuel Here is just a note: You can get un-leaded race fuel from distributor for these guys. http://www.racegas.com/Racegas/fuelspecs/default.asp When I lived in Alaska I had GT Plus 104 octane shipped in for $7.50 a gallon in 55 gallon drums.
Thread Starter
TECH Fanatic
Joined: Nov 2001
Posts: 1,705
Likes: 0
From: Iowa :-/~
Re: Retard timing verses high octane fuel Chris I see what your saying about timing and having the burn farther after TDC to hedge against detonation. (I'm a novice here and just trying to learn please don't take this like I'm disagreeing) Speaking to the timing being retarded and after TDC...This is why I ask about using high octane fuel. The higher the octane the greater detonation fighting properties you have, that is the nature of the fuel. And this is my logic, if using higher octane fuel (higher detonation fighting properties) the less retarding you have to do (still will be after TDC) and more HP can be produced as the timing is set closer to optimum. Is my thinking flawed or is this worthy of farther investigation? Lets remember SILVER LS1 using 118 octane fuel to do a 300 shot on stock internals.
Trending Topics
Thread Starter
TECH Fanatic
Joined: Nov 2001
Posts: 1,705
Likes: 0
From: Iowa :-/~
Re: Retard timing verses high octane fuel Hey Chris I found your other post and read through it. Making more since to me now. In my posts here I'm not talking about as big a shot, I guess I should have clarified it first. At this time I'm talking about up to a 150 shot. With this in mind I'm really asking is it a better idea to use high octane to further hedge our safety with up to this high of shot. When I go higher I will be retarding my timing to your recommendations.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo Re: Retard timing verses high octane fuel IMO there are two seperate issues here. The first and most important is that NO detonation occur. If it does you basically have two choices, retard timing or increase octane. Second is tuning for power. Retarding timing even more may or may not increase power. 75% of the time max power will be near max timing with no detonation.
TECH Enthusiast
Joined: Feb 2002
Posts: 551
Likes: 0
From: chicago
Re: Retard timing verses high octane fuel C5 is right but not only do you retared timing to stop detonation it also will lower cylinder pressure which besides helping with knock also reduces wear on the bearings, pistons, rods and so forth. You have to remember even on a 150 hp shot say you will get about 200lbs increase in torque so you really don't need the all the timing. Your best bet is run a minimum 100 octane and rule of thumb from NOS is 2 degress for every 50 hp in the shot. The granetelli mafs for the dry kit retards your timing 2 to 3 degress and I had no kr at all.Any other ?s email me rsschuler@netzero.net <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
