I agree with that. An A/F wideband is an excellent investment and well worth the money if your running a big shot of nitrous.

 

Thought I would check out this thread for some nice technical timing info. After reading the Lost Cause debate, I was wrong.

Robertt56 - I couldn't agree more with your timing levels for your power level, looks like it cost you some money to obtain that info?

MRDragster1970 - good rules of thumb practical application, You wouldn't be a Robert or a Bobby would you?

just some info on my exp.
I have tuned more then a few lsx cars
Stock LS1s on Cali 91 fuel in 100 heat will just start pinging @ 26 deg.

IMHexp. back to back dyno and track results have proven;
Less timing will always make more power on spray than NA timing.

FACT. Detonation @ BTDC makes massive negative torque.

The point to internal combustion is to expand or detonate the fuel ATDC to send the piston and rod in the direction it is ALREADY going...DOWN. Spark advance is lead time for the burn event to happen. There is another technology out there that uses glow plugs that have no spark advance and it make gobs of low end torque.

FACT. Pre detonation is happening before you can see or hear it. If you are making a minor 15-25 foot pounds of negative tq due to mild pre detonation that you can not hear yet, it is hard...impossible... to realize this minor power loss when your adding 200 hp to the motor.

Anyone want to do the math on how much total heat energy the piston head and valve have to endure with 20 HP worth of detonation **20hp is like 4% of total output on a 200ish shot LS1** with a 11 second run. Watching a nice calibrated aftermarket temp gauge crank over to the right during and after a run is a good indication that too much timing is present.

 

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No, that is my real license ! ! !

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Oh duh~ my bad

 

Good explanation. Yea that pre ignition can lead to detonation. 30 guys were standing around my car and it didn't make any noise or sign of something wrong. Was watching for KR on the laptop, it was ZERO. My car held up well with over 200 sprayed passes, then went to a 285rwhp and decided to pull an additional 4* of timing, well I added the 4* instead of pulling it, and ended up with about 26* total. Way too much for that level, that's why I caution running a high timing on the big shots. (on my dry, timing can be pulled in the tune automatically when spraying only)

Anyway, Lostcause, what plugs are you running. Is this how you have been checking for detonation, reading plugs? Really the best way I am finding out, can't count on the Tuner Programs to let us know. Once again, good luck on your combo, i am hoping my 408 will also be a beast.

Remember what Brad said, (to all reading along) it's not a matter of if you hurt something, but rather a matter of when, at least on the big hits.
Robert

 

Could Not agree more!

 

In addition, Everyone on here who is serious about making safe power wither it be N/A or forced induction should have a WB in their car. Reading plugs is not always as accurate as one might think. Not to say don't read plugs but they will not always tell you the whole story. If I had my way I'd put one in every header tube!
I wonder if anyone can give me a price break for buying 8 WB's?

 

wide band are good, but not always right on. like computers. never put all your eggs in one basket.
always read plugs no mater what the wb says.

 

Dude...plug reading has been around WAY before WB's were invented. He may be old school....If he is, id bet he knows what hes looking at under that 10X magnifier.

 

I Agree Plug Reading has been around for much longer and it is a another way to look inside the combustion chamber. However, unless you make a pass wide open, immediately shut off the engine and then read the plugs there is a good chance that they will not show you what you need to see. Idling and part throttle time will change the way the plugs look and what they show.
On the same token, if something is going south in the motor, a WB will NOT show you signs of detonation!

 

Ya thats what i was thinking.... isnt our cars stock with 28 degrees timing??

I've heard that 2 degrees per 50hp but i was running stock timing on my 100 shot with no problems but i had a bigger fuel jet then i was supposed to so that away it was "safe"

 

yes and no... you have to shut it off immediately to know where your A/F is at. but if you were detonating/leaning out your plugs are going to be pretty hammered (speckled and/or melted ground straps) even if you let the car idle for a while afterwards.


Btw robert i dont think it was 100% the timing that killed your motor... the stock pistons are junk and you were running power levels similar to what most guys run before the ring lands give up. id say yours looks like it finally just cracked or got a little melted then just went to hell. Forged nitrous pistons are a alot more forgiving and can handle alot more actual HP than the stock pistons.


its all in the tune up till a point... that point is the actual physical constraints the motor itself has on it. you can have a tune spot on but stock pistons are not going to like over 550 RWHP for very long

 

after every pass i run threw the traps, throw it in N shut it right down and cost to the end. i pull over, shut off my bottle, purge, then pull a few plugs throw some warmup plugs in the car drive back to the trailer. read the plugs, put them back in, pull the rest of the plugs be sure all looks ok, reinstall mke adjustments as needed. thats how you do it.

 

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If you're not towing back then you have to pull the plugs at the big end ^^^^. Even the 1/2 mile drive back will alter the true read. I have a Professional style data recorder, on my Pro-Modified and we still pull plugs. All the data you can get, is better for making changes, or catching something going away on you.

For the guys running more timing than the specs say, or people say you should. More timing is not going to make more power in every case. As said, there is a specific relationship between burn, timing, compression, efficiency ect ect. You might actually be hurting your power by going more & more timing. Just because you aren't blowing up, doesn't mean you won't. Maybe soon, maybe never. Example on BBC. The better the head, the less timing we run. My Profiler & Pro-Stock heads run much less timing, and make more power. I'm not a rocket scientist, but there is a real reason for more efficient motors with & without N2O to like less timing.

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All in all timing is just what is states, Timing. You are timing when you have max cylinder pressure at a given crank angle. All the number is, is your lead time. More efficent engine will want less lead time.

 

I wish there was an easy answer to this. Say I'm running 28 degrees on a NA tune, I can bump it up to 32 with no knock on hot days and also no gain in power...so wouldn't spraying a 150 at 28 just be like running 28 and saying I'm pulling 4 degrees...???

So what do most people do? So say I'm running 28 degrees and want to spray a dual stage 300 shot. 93 in tank and 116 in stand-alone. One guy said he was at 25 degrees and a dual stage 300 shot. If I check plugs (right heat range and good reading) at that level, have no KR, read fat on a wideband, and only use fresh race gas that wouldn't be safe? If not then why the hell not? It seems like running the timing up until I get some kr and then backing it off is just running it close to the edge...

 

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I'm probably not saying what I mean correctly, but I'll try. If you increase timing and don't increase HP why do it. Max timing without detonating is not automatically max power. Like it was said, peak power has a sweet spot in timing. If my motor runs the exact same from 22-26 degrees, I run 22 degrees. On conventional heads, same thing, 32-36 degrees, I use 32. Just because you can run more timing without knock, doesn't mean you have to.

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If you've bumped timing up on a dyno you'll notice that as you add degrees you make more power to a certain point, then you really won't make much more even as you add timing to it. This is probably where you're sitting. if you then continue to add timing you'll then hit detonation.

All spark advance does is timing the flame front, or pressure spike, to the downward motion of the piston. This is good for the motor. You can add too much advance and have the pressure spike hit during the piston's dwell time at the top of its motion. This is when you'll be able to add timing without making more power. This isn't that great for your motor. When the peak pressure hits as the piston is on it's way up is when you'll hear the actual ping, though. That's the sound of your bearings making contact with each other. This is bad for your motor.

 

Oh so true. There is no need to advance till it knocks, juts till youre at peak power.

 

lol there is so much more to that statement its insane though... there is another HUGE piece to this puzzle.... a/f ratios.


until you mess around with your a/f ratio at the higher timing levels you will never really know if your at "max power"