Nos timging retard for 4 cly per hp shot?

[bakes]

Question on retarding timing as per hp level, most say 2 deg for every 50 hp added but this is for a V8 # ,wouldn't a 4cyl be like 4 deg retard for 50 hp added because of 1/2 the cylinders twice the cylinder preasure to make the same Hp as a V8??

[bakes]

or how much timing are you pulling with your XX hp shot?

[Dave]

Ive always followed the rule of 2* per 50 shot. However, I don't listen to the rules for just a 50 shot alone. If I we're going bigger I'd be more concerned. I did not see any detonation (salt/pepper) after making a few runs.

[BadAssPerformance]

I have always used -4°/100hp per NOS's instructions years ago. This is a base timing *suggestion* and depending on how your cal adds timing for RPM it could be too much.

Zin, weren't we taking about making a nitorus KC article? I'll help with the formatting... :thumb:

[zin]

I have always used -4°/100hp per NOS's instructions years ago. This is a base timing *suggestion* and depending on how your cal adds timing for RPM it could be too much.

Zin, weren't we taking about making a nitorus KC article? I'll help with the formatting... :thumb:

Yeah.... Soon as we get some "spare" time! Maybe we just cut and paste from all the threads?:D

Timing retard is confusing to some, but the reason behind it is really simple. More oxygen = faster burn. Engines make best use of the cylinder pressure if you generate peak pressure around 15-20* ATDC.

Normally we have to "light the fire" around 36-38* BTDC in order to achieve this goal. But, add extra oxygen and it'll happen sooner and sooner as the oxygen concentration goes up.

The rule of thumb (2* per 50HP of nitrous) is a nice, safe starting point. No one is going to blow up something because they took too much timing out, their engine may run like crap and not make any power, but a late pressure peak is safe.

So, if you stick with 2* per 50HP of nitrous you'll be safe, but probably not optimized.

To optimize the timing you'd have to read the plugs and adjust accordingly. Most times you'll leave it a bit rich (light tan color), then add 1* and make a pass. If the MPH is up, you made more HP and that means the timing is closer to optimum. Re-read the plugs and add fuel if needed, then try another degree, if the MPH comes up, repeat the previous steps. If the MPH doesn't improve, or if you ever see signs of detonation (black/purple/silvery specks on the insulator), STOP!, and back up the timing to the last setting that showed an improvement. This is your optimum timing. Once you have this figured out, you can equate it to X* of retard per 50HP of nitrous. This is useful when you go bigger (and we always do, don't we?:nod:), as you'll know exactly how much timing to take out without having to make a bunch of runs... I do hedge my bets and take an extra 1* off of my paper figure, just because weird sh1t happens!

Hope that makes sense! If not, feel free to ask questions.

Mike

[BadAssPerformance]

Yeah.... Soon as we get some "spare" time! Maybe we just cut and paste from all the threads?:D

LOL, I hear ya on the free time! With the new KC software... if you can shoot me links to threads/posts, I can combine them into an article :thumb: