ran the camaro yesterday and went real well, 9.8/138 mph, car weighs 3950 with me in it so its making close to 1k flywheel hp. running 112 octane, blow thru carb, 28 deg timing, 15 psi boost. wideband showing 11.8. did a plug reading, and i dont see a burn in mark on the groundstrap for timing, most of the stuff i set usually has a heat mark about midway on the groundstrap, and the plug has a yellowish tinge to it. my friend who sets up nitrous engines agreed that there is no timing mark on the strap, also said that the yellow is from not having enough heat in the chamber(lack of timing). i put another 2 degrees in it(30 deg total at this point) and ran the car again. wideband went to 12.2, and mph and et stayed the same, so the car needs more jet, plug lost some of its yellow on this run, but still no burn in mark. i included a pic of the plug, but is this correct that when the timing is rite on a turbo engine i should have the annealing mark? #ad

 

Yes, I think you're on the right track...

 

i wiped the ground strap off, no marks on it and it looks like new, i wonder if i need to go to a warmer plug, currently have br8es in it

 

If it's staying that clean, it's burning good, I'd add a bit more timing...

 

Are you at 30* in boost? You should have seen a mph change adding timing.... I would proceed cautiously if adding timing.

 

If it didnt pick up mph with more timing put it back where it was. Blow thru stuff seems real happy at 28 degrees max on a combo like yours and i would be cautious going any higher.

 

30 deg at 16 psi, the engine apparently wants more fuel with the additional timing, it is running 112 octane as well

 

let me ask this, i know with the typical efi stuff i work on, if you timing and you have to add fuel you keep going, until you add timing and the engine doesn't want any more fuel. if fueling requirement goes up that usually means the engine is making more power and needs more fuel. do you guys agree?

 

I would agree.

 

I agree with trbo355... with a decent chamber 30* seems like more timing than I thought it would need. Either way at this point you need to be very careful what you do. If you're sure you want more fuel, and timing, back the timing down, add fuel, and slowly bring timing back a degree at a time until hp, or mph levels off, or falls. trbo355 knows gen1 sbc's... you may have read his "grenade" thread....

 

let me ask this, is it possible with the 112 octane that the timing requirements will increase due to the slow burn rate of the fuel?

 

I'd say that's quite possible. What's the static compression of your motor Charlie? What fuel would it need if it was N/A?

 

9.2:1 compression ratio

 

Then I'd say "definitely possible". That should be an easy 93 octane pump gas combo up to at least 6 or 8 psi.

 

The 112 is definitely going to like more advance, but many n/a setups don't like more than 36-38 degrees on 112 with a good chamber, and some compression. Every combo is different, and the only way to know is to test, and tune, just don't make any drastic changes.

 

Here are the pics of the plugs cut open the lower plug is 28 top 30 #ad


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Man that pic looks kinda like a spark plug sticking out of a hairy butt crack.

I think you're nuts! Added timing and boost'¦ picked up no power'¦ then and add more timing? What tuning school are these methods from? 12.2 isn't lean on race gas. The fact that you added boost/timing , its running on the leaner side of peak power AFR, and it didn't pick up any MPH means it is NOT making more power. Adding more timing and fuel isn't going to fix that. It's going to melt things. Also jumping 2* either direction is a huge step when dealing with a boosted engine. Professional tuners adjust timing a ¼* at a time. 2* jumps are nutty when your already at 28*+ in my book.

The whole 'yellow plugs need more timing' is total BS IMO. That could be related to many things. I agree that plug doesn't look right. Was that a new plug installed just before that run? Did you shut off the car right after the pass and pull the plug to inspect it? That plug looks like it's been driven on before and/or after the pass. Heat line in the strap should be VERY visible if done properly. The nickel plating should still look shiny and new. Your cut up plug is showing your fuel ring, it has nothing to do with timing.

Tuning is hard with a carb because your AFR keeps jumping around. You need a set boost level/AFR to dial in timing. Adjust timing to a known safe level. Set desired AFR, Set desired boost and maintain your desired AFR. Last step is to bring in timing slowly and really should be done on a dyno. A degree of timing should gain 15-30hp range. Very easy to see on a dyno. Once 'in the zone' typical peak gains on the LS stuff is around 20whp per degree. Eventually you'll see less of a gain per degree say 15whp'¦ That is the stopping point if you want a 'safe' tune. YOU can keep going and try to squeak out a tiny bit more but it's not worth it IMO and usually breaks something. If you adjust the boost or AFR you have to do the process all over again.

I'm not suggesting you run crazy low timing. I don't mean to come off as a wanker either, I wish you the best of luck. I really think you're going to break something if you keep tuning as you are.

 

^^ Agree 100 Percent and I thought the same! That's a damn hairy ass... I've always added till no power or ET is gained, no point after.

 

i had to hold the camera with one hand and focus with the other, so held the plug in my legs, lol. basically ran 16 lbs boost, 28 deg timing, 112 octane. wideband showed 11.8, and that is the rich plug, but we have no annealing mark on the ground strap. went to 30 deg timing, 16 lbs boost, wideband went up into the 12's, lite popping in exhaust at the end of the run, and plug looked lean-still no annealing mark on the ground strap. thats where i'm at rite now with it. i changed the power valve jets from 73's to 80's(had to drill them), and changed the primary mains from 76 to 75, so i went up 6 jet sizes to richen it up. why am i not seeing a mark on the ground strap? and, when i added the 2 degrees of timing why did it go lean?

 

Did you put a new plug in just before the run... IE at the track, no street driving? Did you shut the car down after the pass and coast. Then pull the plug without starting it again? Thats how to get a good plug reading.

Most of the plug should still look shiny and new... similar to this...

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