Hello, I am engaging nitrous at 3500 RPMs and it is a 100 shot. My total timing with nitrous is 32 degrees. My air/fuel ratio was a pretty wide range from 11.0:1 all the way to 12.2:1. Is this safe for nitrous or should I go richer or leaner?

Thanks!

 

It's rich and that's too much timing.

To start - I'd be around 25* total and AFR of 12.5-12.8 but don't chase an AFR number just to have it at a certain number.... Anywhere in the 12.5-12.8 range is safe and the engine will tell you on the time slip where it likes to be run in that range.

Like wise with the timing.... forget about this "pull X number of degrees per 50hp" stuff. That's 1980's tune up technology and it's burned up a bunch of engines... and given enough hits it'll burn yours up too.

When tuning nitrous - Always take more timing out than you think you need and work on cleaning up the fuel first.... Once you have the AF tune up clean, then start bumping the timing up 1* at a time until MPH falls off.

Then will you know the limits and where you need to be.

Will

 

agreed with will. 11:1 is too rich on nitrous - you are giving up power.

i know my nx wet system didnt require any timing retard up to 100 shot, but i cant speK for your system/setup.

call the nitrous manufacturer tech support line and ask.

 

Okay well I'm a little on the edge about nitrous because this is my first time using it. Is 11.0:1 rich enough to damage the motor? And should I try to be at 12.0:1? I'm not looking for the strongest hp and torque number I just want to be reasonably safe.

Thanks!

 

Rich is very dangerous to the engine its worse than being lean. Keep in mind your burning all that extra fuel and injecting extra oxygen needed to do that via the nitrous... too much fuel is bad... too much oxygen not as much.

Timing is the real killer... all the extra fuel and oxygen burns HOT and super fast... you don't need timing advance in that situation and when you light it off too early starting the power stroke too soon BTDC your in trouble next go around because of the heat generated and trapped in the cyl.

11 anything AFR is bad enough to hurt it coupled with too much timing. Like I said knock some timing out and lean it out to the 12.5-12.8 AFR range.
Will

 

I'm not in agreement with you. Extra fuel (rich) will cool the combustion chamber. Extra oxygen (lean), aka nitrous, will find something to burn due to increased burn temperature. (like your piston) Think of an oxygen/acetylene torch. I haven't heard of a nitrous engine burning down due to extra fuel. Just my .02

 

I was of the same opinion you have for a very long time but Monte Smith set me straight about 10yrs ago.

Here it is straight from 2 of the top dogs in the nitrous industry. Right on the first page you Steve Johnson, Monte and Billy Stocklin (one of the top Pro Mod tuners) talking about rich v/s lean and the importance of timing advance....

http://www.yellowbullet.com/forum/sh...d.php?t=126804

FYI I torched every piston in my race car last year because my new fogger came to me with a tune up sheet that had a typo for the starting tune up. Car was pretty fast but the plugs looked like crap.... So I broke out my wideband and found it was running 10.9-11.0 AFR....

On a baby 300 shot it only took 6 passes to crush the ring lands in all 8 Diamond custom nitrous pistons and it even bent the .215 wall H-13 wrist pins.... Over $1500 to replace 8 pistons, wrist pins and rings.

Will

 

Wow really? 10.9:1 was rich enough to do that? Damn

 

What your seeing here is very rare in a nitrous engine failure.... most of the time the damage is catastrophic to the pistons. I just caught it early and stopped racing it before it got that bad.

The motor started smoking a little because it was passing oil (frozen second ring). If I would have ignored the smoke and made one more pass it.... It would have been over... this piston would have looked like a torch burned down the side, because the oil passing into the chamber would have caused detonation.

You can see it cracked the lower top ring land support and crushed the land down on the 2nd ring locking it up.... You can also see a very fine line developing from the crown down to the top ring land where it was about to torch...



In all fairness I'm making near/over 1000HP so everything including damage and the rate it happens is magnified compared to a lower HP car.

A lot of people get away running nitrous rich. I did also when I first started out because all nitrous tune ups were rich and over timed.... The consensus from the experts is that those people just aren't making enough power to hurt parts in a hurry. And that makes sense to me today because once I really started to make some HP, I started hurting parts. I always thought that hurting parts was the nature of big power nitrous engines, because everybody was hurting parts at my level back then.

Past 10yrs I've been tuning my stuff to be "lean and mean". This is the first failure I have had in many years and I know for a fact it's due to it being too rich.
Will