Hey guys,

Trying to get a better understanding of reading plugs more accurately. So regardless of how much boost, or the engine combo, or fuel used, what we are trying to accomplish is max cylinder pressure at 5-10* ATDC or somewhere in that area.

Does the heat line on the ground strap tell you where your timing is relative to the ATDC degree?

Assuming the line being right in the middle or at the bend is in the 5-10* ATDC range, and if the heat line was all the way to the base ring peak cylinder pressure is closer to 0*?

One other question, tuning without a dyno for max timing. How can you tell on the plugs if you have too much or not enough timing at peak torque in the mid range vs HP in the upper rpms? This seems almost impossible to figure out best peak torque timing and peak HP timing without a dyno or being at the track.

 

Personally my opinion (on another website that I frequent (Pontiac Site - I own a early GTO), We have a Boost Section over there.

We are dealing with 6 second vehicles 199+ mph speeds.

One thing that I recommend is that you are extremely careful with timing, especially on a dyno.
I have seen thousand of dyno runs at the Company I used to work for (see Avitar picture).
I have also seen lots of runs at different dyno shops in the country.

What fuel you run makes a difference SLIGHTLY.
An example. many engine like for total timing a number between 22 and 27 degrees of total timing under high boost.
These engine are Methanol engines, E-85 Engines, and Gas engines. They make a lot of power and they do not hurt parts based on screwing up on the timing and going too far.

If you want to get greedy on timing, be prepared to buy a lot of engine spare parts. One extra degree can be the difference betweena good engine and a broken engine once you get past 27 degrees of timing. under 27 degrees of timing the SPECIFIC ENGINE seems to like that 22 to 26 degree window.

I have seen the blown head gaskets, the torched heads, the pistons with ring land torn off and holes in pistons.
Again, if you have lots of cash and are ging for $50,000 in prize money, maybe you can use the money to buy new parts if you kill the engine on the winning pass. Either that or the TV Show people are giving you enough cash that you can take a chance.

Now these engines are Procharger Engines, Vortech Engines, and Turbo Engines, for the most part.
People who can afford Brad Anderson Engines are not hanging out here and reading this post.

It does not seem to matter if the engine is a 4 cylinder Pontiac engine that makes 780 HP on 200 cubic inches and 38 psi of boost on E-85 fuel or guys running Methanol engines that make 2885 HP and run 230 mph at much higher boost.

Ideally you would cut the plugs apart and look at the inside of the plug (inside the threaded part) vs just the ground strap. Again a money deal.

You can make a lot of power with boost and even more boost. You can hurt a lot of engines with getting greedy on timing.
Not saying you can't go there on your Chebby or Ford but timing doesn't seem to care whose name is on the engine.
It tears them all up if you make a mistake, due to greed or bragging, and wanting 5 more hp NA or 30 more hp Boosted.

Tom V.

 

Thank you for that info. I definitely agree with not getting greedy with timing. I've had my share in the past of several blown head gaskets and a cracked block. Not fun.

I understand cutting the plug open to see the porcelain. This is mostly for the AF/ jetting correct?

My main question about reading plugs, is basically my plugs show no heat in them.

This new car I aquired is basically a stock 4.6 mod motor. I'm not familiar with these engines and the timing curve that they require unboosted.

My last car had a 363ci with a F1R Procharger. I was at home tuning that car. But the info I've seen on this mod motor is crazy. I see people claiming max timing at only 10* with pump gas.

I have my total timing up to 16* and the plugs still show now heat in them. Like you said, don't get greedy. At the same time I don't want a Ill tuned motor that the combustion event is finishing in the exhaust.

I'm keeping the AF around 11.5 and boost is peaking at 8-10#. I just want to get the timing in a nice safe zone for 93 pump gas without putting too much pressure on the stock internals.

So should I creep up on the timing until the heat line is in the middle of the ground strap? Or is that too must heat for pump gas?

 

When I cut the spark plug apart I look for small metal "Balls" down inside the cavity between the porcelain and the threaded housing.
If no "balls" then good if the heat is showing on the ground strap in the middle of the curve.
This article/link does a pretty good job with explaining things with pictures.

http://www.4secondsflat.com/Spark_plug_reading.html

Tom V.

 

Here is best plug info I've found: http://www.strappe.com/plugs.html

 

Good info guys. But holy bajesus there is a lot of info to be had from looking at the plugs!

I read a part about plug heat range being too cold. Said you won't always see the correct heat in the ground strap even being over advanced. This makes sense as I remember on my F1R combo I could never get enough heat in the NGK 10s no matter how much advance I did. 9s were much better.

So about the timing curve .......

Peak cylinder pressure is at peak torque/ peak VE. Is this area of timing lower than the top end HP timing?

Do you have any boosted SBF timing tables I might reference?

Thanks again for the plug info guys

 

Both VE and RPM affect timing
So if you held VE constant you'd expect to see an increase in timing with rpm for most common engine configurations

likewise if you held rpm constant and increase VE you will gradually want the timing to decrease.

Since most engines are dropping a bit of VE after peak torque while rpm is increasing, it gives both 'green lights' safe to advance slightly into redline.

that said, combustion chamber design, fuel quality, and chamber heating (which becomes measurable EGT), also play a role in the speed of combustion dynamic.
If the engine parts are getting hot and running a poor (gasoline) fuel and doing drag racing 'runs' (short blasts followed by a cooldown) it is entirely possible that you'd need to pull timing as it redlines for extreme setups due to temperature creep.

 

Makes perfect sense, thank you!

 

I'm using the Holley HP.

Can i use my VE table to find peak power while adding timing throughout the rpm? Like if I add 2* and it picks up power or looses power, will I see it in the VE table?

 

Often peeps go with colder plugs cuz they are trying to play it safe. The wrong heat range can be misleading. If someone was to run a plug too cold for the app. it can lead to overtiming if they start chasing the plug only. Now if they are watching data and track #s they should see that the timing isnt helping.
10 or 11 ngks are for extreme setups. Like , much beyond what some think.


This is way better explanation of reading plugs.
http://www.crankshaftcoalition.com/wiki/Reading_spark_plugs

 

100% agree about the plug heat range. NGK 10s were way over kill for my last F1R setup. Would constantly soot up the plugs and eventually would start misfiring.

 

Essentially, yes, to a degree. The holley fuel table can be correlated to hp easily.

 

Gonna have to start slow and see if VE changes wi
Tuning for optimal timing at peak torque seems like a real bitch without a dyno.

I still don't get how you could be optimum with timing at peak HP and at peak torque track tuning. How the hell going by mph, do you know if you picked up torque or HP?

 

Because hp can be calculated from mph and vehicle weight. Lots of calculators online, like wallaceracing.com. The mph has to be from a drag strip pass to work

 

Oh I get it, I'm totally familiar with track tuning.

However, I'm only familiar with global timing adjustment, ie distributor adjustments. Last combo I ran a locked out dizzy and a BTM. This Holley EFI is my first stand alone.
I'm gonna see if I can upload a pic of my timing table. You guys tell me what you think.

 

If you email me your tune, I can look it over for you and send it back with changes you can try.

This content is protected

 

Awesome man, thank you!

 

I sent over that tune file, let me know if you didn't receive it.

 

I did and I will look it over this weekend