It was mentioned that I might want to retard timing some (using LS1 Edit) when I run my N2O for optimal performance. Is this true? Why?

The reason I ask is becuase plenty of people are bolting on prefab N2O kits and hauling *** without messing around with the timing in their computers.

Inputs?

 

Yes..with a shot that large I would definately look in to retarding timing. With the increased cylinder pressure from a 250 shot detonation will be more likely. If you retard the timing you delay the peak cylinder pressure farther beyond TDC giving more "room" for the pressure to expand keeping peak cylinder pressure down.

The general rule of thumb concerning nitrous and timing retard is 1-1/12 degrees for every 50 hp increase. LS1s seem to be able to stretch that a bit. We regularly use 100-150 shots without any timing retard...although I would be willing to bet some of those people do get detonation from time to time without them knowing. I dont know what timing your running...but for the big shot I would use that rule of thumb to start out conservative. 250 shot = 5-8degres of timing retard. Also start with the AF on the rich side. Then tune for 12 or 12.5 to 1. Keep and eye on KR during the runs. Stay conservative....many times with loud exhaust on spray you will not hear the detonation and damage can occur in the blink of an eye.

 

As of right now, the timing is 32 degress NA across the board at WOT, but I haven't seen any KR at all.

So do I continue running big timing with N2O as long as there is no KR?

Or do I assume there is unseen detonation a scale back the timing for running wet shots?

Todd

 

IMO you will have to assume detonation will occur and err on the side of caution. The alternative would be actual detonation. Your timing is already at the max even for an NA tune. Many think anything beyond 29 degrees is a waste. With that much timing I would bet on detonation occuring with that big a shot.

Anybody run a big shot on stock cubes? What timing did you guys use?

 

I made up a new timing curve for N2O on LS1 Edit. Backs off timing starting at 3600rpm (I spray at 3800-4000). Timing is retarded to 25 degrees for the spray. I will check the results on the dyno soon.

Thanks for the input!
Todd

 

New timing tables? Damn...I wish I had LS1 edit.lol.

Are you spraying a 250 shot? What kind of setup do you have?

 

What if instead of pulling timing you up the octane? Would 116 be enough octane to run a 250-300 shot on agressive timing, assuming no KR?

- Matt

 

One of the reasons I got rid of the turbo was constantly buying race gas for when I wanted to haul *** <img border="0" alt="[bullshit]" title="" src="graemlins/gr_bs.gif" />

So I'd rather pull timing and use pump gas for now.

Todd

 

32º of timing on a shot that large is asking for trouble. I think your 25º table is a good place to start, I probably would said start out at 26º and go from there.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Trans Am WS6 420:
<strong>What if instead of pulling timing you up the octane? Would 116 be enough octane to run a 250-300 shot on agressive timing, assuming no KR?
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">It isn't so much that the advanced timing will lead to detonation and hence race gas would be the fix. A juiced charge burns a lot quicker than a NA charge, and the larger the shot the greater the burn rate in the chamber. The reason behind retarding the timing is make sure that your cylinder pressure does not peak while the piston is still coming up to TDC. The goal is to get your cylinder pressure to peak in the same palce as it does for optimal NA power, which is a couple degrees after TDC where the piston has just started to move downward. With the faster burn rate of a nitrous charge, you have to retard the timing to get your pressure peak at the right point.
Hope that makes sense and helps.

 

You would defintly want to retard the timing with that shot detonation would almost be a sure thing even with race gas and if you still have hypereutectic pistons I wouldn't even think of that much n2o. Nos systems recomends 2 degress for every 50 hp of n2o.even with timing retarded I would say to use at least 100 octane.I ran a dry kit last year with a mafs for the dry kit 2 to 3 degree retard with that mafs and ran 100 octane at the track. Had great results and know problems 11.67@115 mph in a 2000 SS convertable with a few other mods. Hope that helps you out any other ?s email me. rsschuler@netzero.net

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Reckless:
<strong>One of the reasons I got rid of the turbo was constantly buying race gas for when I wanted to haul *** <img border="0" alt="[bullshit]" title="" src="graemlins/gr_bs.gif" />

So I'd rather pull timing and use pump gas for now.

Todd</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">OMG...I just bought some race gas today. Like $4.50 a gallon for 100 octane. And people complain about filling bottles. Ill fill a botle anyday over paying $50 for half a tank of gas. I agree about pulling timing instead of race gas. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

TNT F2 kit >>>

<img src="http://www.turbo-ws6.com/tnt.jpg" alt="" />

<small>[ March 21, 2002, 12:33 PM: Message edited by: Reckless ]</small>

 

Thanks for the inputs guys! I will be getting back on the dyno tomorrow prolly. We'll see haow the new timing table works out.

spiesscj...thanks for the explanation. I always like to know why I am doing things. I hate doing things just because someone says it's a good idea. Your explanation cleared things up for me. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

I don't have a stock bottom end BTW. My motor was built to handle 15psi of boost:

Lunati Rods, Ross Forged pistons, blah, blah, blah <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Thanks Again!
Todd

 

Hey reckless good luck on the dyno.Sounds like you have a good motor but remember how much it cost and I wouldn't want to brake it tring to save 3 bucks a gallon. This is racing and knowbody said it was cheap.Don't want to sound like a dck but I blew up my 525 bbc by tring to save a few bucks and made junk of it. Just tring to save you those same headaches. Good luck again.Rich