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Discussion Starter #1
Ok so many are aware that the passenger side of a BBC usually ends up with a different timing than the drivers side due to piston rock and rod angle at tdc. so some compensated with a different thickness head gasket on one side, that being said your changing the compression ratio on that entire bank. so arent you changing the power on one side vs the other? now for the main question here. ASSUME the combustion chambers are cnc'd and exactly the same so the flame travel and quench is out of the equation ok. when the technology advanced and we can now control individual cylinder timing we have started to move timing around by reading plugs in an attempt to make each cylinder "happy". So most know that I have switched to efi and LOVE it. In my amazement of what these systems can do i have started think about its ability. so WHY are we changing the timing in each cylinder and not the amount of fuel to make them "happy"? the crank, rods, and pistons are not varying they are in a solid state(except for rod stretch). that being said for example lets say cylinder number one has a very hot spark plug its clear back into the bend and this particular engine seem to be happiest with the timing mark just a 1/8 from the end of the tip. So you go in and take a degree out make a pass and now that plugs mark is in the middle of the flat of the strap so you pull another half and now its right in line with the rest. that cylinder is now showing a equal plug to the rest. now the piston is not moving different its not dwelling at tdc different than the other cylinders on that side so WHY did we move the timing. My way of thinking is the variables here are the throttle body location, the shape of the intake runners, and the shape of the runners in the head. I have a tunnel ram now with two throttle bodies not a single intake with a single TB which is what started part of this thought. Before I switched to the tunnel ram I had cylinder number 3 was really pissed off. I just assumed it was a more efficient chamber. so the heads didn't come off just the intake and it immediately became a twin to number 5 needing no timing being pulled. so that told me it was in the intake and possibly the carb? im good with the fact it was either more or less efficient but now to my main point. why are we not tailoring individual cylinders fuel instead of timing? you take timing away you are not making the cylinder fatter but you are delaying its efficiency to burn the fuel because its more efficient for what ever reason. so why arent we giving each cylinder that fuel it wants for the air it can get and leave the timing as a solid base IF the chambers are the same, the rods are the same the pistons are the same the head gaskets are the same the timing is the same. the difference is the amount of air that gets in each cylinder for what ever reason. on a fogger the amount of nitrous in each cylinder is the same as well (assuming each nozzle flows the same). im not saying I am right I am opening a barn door for opinions. maybe I am just not seeing it right.
 

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The fact that we are giving some cylinders more fuel due to better intake charge or whatever, gives them the potential to make more power (not unlike a larger pill). Thus requires less timing (just like a larger pill).

HP potenial is different so timing could be as well.

Just my thoughts.......
 

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Discussion Starter #3
I agree, I shouldn't have said it has to a solid timing number because each cylinder in a compression test and leak down are going to vary slightly. but my thought was what if and why are we not tuning each cylinder differently? I mean maybe the answer really is timing but with an injector in each runner to me if the efficiency of the intake varies or like you were saying the charge is different from cylinder to cylinder be it sealed scoop at 165 mph shoving more air into the back runners in evitably in that case wouldn't the rear runners need more fuel?
 

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Efi does give you the option of adding individual cylinder fuel control but the thought of compensating a hot cylinder with fuel is a good way to make ashtrays. The older nitrous tunes were based on the same line of thought. The end result was a serious nitrous guy had a first hand relationship with his piston builder. Hell I think I made it on Mike Nelsons Christmas list at one point. As long as the fuel system has zero failures i.e. filter issue, fuel pump or regulator issues, it will survive. The problem is when those components don't work consistently. You make make a small power gain, but would it really be worth it over a clean tuneup with a degree or 2 missing?
 

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The nitrous guy
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Some have the mistaken impression that removing timing from a cylinder to make it "happy" is costing you power and that is usually not the case. Especially with an EFI combo, you can be pretty assured that distribution is good and fuel is properly atomized. But regardless of that, injecting nitrous into the equation results in some cylinders being more efficient than others. Efficient, translates into a quicker and more efficient burn. So if that cylinder cleanly burns the charge quicker than others, removing timing to make that hole burn equally to the others does not cost you power.

As Jon was getting at............in a perfect world, an 800hp motor would make 100hp per hole...........doesn't work that way
 

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Discussion Starter #6
Efi does give you the option of adding individual cylinder fuel control but the thought of compensating a hot cylinder with fuel is a good way to make ashtrays. The older nitrous tunes were based on the same line of thought. The end result was a serious nitrous guy had a first hand relationship with his piston builder. Hell I think I made it on Mike Nelsons Christmas list at one point. As long as the fuel system has zero failures i.e. filter issue, fuel pump or regulator issues, it will survive. The problem is when those components don't work consistently. You make make a small power gain, but would it really be worth it over a clean tuneup with a degree or 2 missing?
yep I do understand the added fuel when not needed in the end hurts parts. my point is with the exception of ring seal. if a runner is moving more air then its going to want more fuel or it will be leaner than the others. if you have one o2 sensor it doesn't know what individual cylinder is lean or fat it knows the average of whats in the collector is 12.2 or 13.1 but it doesn't know that cylinder 1 is at 10.9 and cylinder 3 is at 13.6. so then I started thinking if every cylinder wants what it wants what if we changing the timing is a band aid for the efficiency(or the lack there of) of a cylinder. now those are big extreme I know im just using that as a example
 

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Some have the mistaken impression that removing timing from a cylinder to make it "happy" is costing you power and that is usually not the case. Especially with an EFI combo, you can be pretty assured that distribution is good and fuel is properly atomized. But regardless of that, injecting nitrous into the equation results in some cylinders being more efficient than others. Efficient, translates into a quicker and more efficient burn. So if that cylinder cleanly burns the charge quicker than others, removing timing to make that hole burn equally to the others does not cost you power.

As Jon was getting at............in a perfect world, an 800hp motor would make 100hp per hole...........doesn't work that way
Monty I agree sometimes it's not a bad idea to slowly jet that hole down a little to even the tune up
 

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yep I do understand the added fuel when not needed in the end hurts parts. my point is with the exception of ring seal. if a runner is moving more air then its going to want more fuel or it will be leaner than the others. if you have one o2 sensor it doesn't know what individual cylinder is lean or fat it knows the average of whats in the collector is 12.2 or 13.1 but it doesn't know that cylinder 1 is at 10.9 and cylinder 3 is at 13.6. so then I started thinking if every cylinder wants what it wants what if we changing the timing is a band aid for the efficiency(or the lack there of) of a cylinder. now those are big extreme I know im just using that as a example
This brings up another point that was mentioned in a different thread about correction if you are correcting off of say one or two o2 sensors and it's an average of 8 cylinders what is it doing to your individual cylinder tune up when it adds and subtracts fuel on all eight cylinders

I fully believe a lean engine can burn up weather it's a over timed issue or not my point is let's say you are correcting off of one o2 mid way through the run you have a injector stop up or for whatever reason stop functioning in that side of the engine the o2 reads super lean and plows fuel to the other seven holes now you have one hole that has no fuel at all but seven overly rich holes
 

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Discussion Starter #9
ok let me see if I can put this another way. we all know that to much fuel lifts ring lands. so we have a cylinder that you have to add 2* off timing to more than the other 6 and you have one that is way more efficient and you have three degrees out of that one. so your adding the 2* because for some reason that cylinder is not as efficient. why would you not take fuel away from that cylinder to increase its efficiency? maybe you take away 1.5% fuel from just that cylinder. does it go lean or does it now need the same spark timing yet now that you pulled fuel from it it is now making the same power as the average because its now not overly rich? it takes air/fuel to make power but how do you know your not adding timing to bandaid a inefficient cylinder?
 

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ok let me see if I can put this another way. we all know that to much fuel lifts ring lands. so we have a cylinder that you have to add 2* off timing to more than the other 6 and you have one that is way more efficient and you have three degrees out of that one. so your adding the 2* because for some reason that cylinder is not as efficient. why would you not take fuel away from that cylinder to increase its efficiency? maybe you take away 1.5% fuel from just that cylinder. does it go lean or does it now need the same spark timing yet now that you pulled fuel from it it is now making the same power as the average because its now not overly rich? it takes air/fuel to make power but how do you know your not adding timing to bandaid a inefficient cylinder?
In that scenario, I think most good tuners would start by getting the fuel out first (or at least in line with the other cylinders) before adding any timing to that cyl.
 

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I always tune with tayloring the fuel first, then timing, usually after I clean a cylinder with fuel, and still shows it is on the cold side, I add timing and then fuel ring shows that it has gone lean, so then I add fuel to the hole again.
 

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Am I reading this right? With EFI you guys are setting the fuel first and then the timing? I grew up on carbs with timing first then fuel... that's changed with EFI?
 

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This is just my opinion and I am not claiming I am right...just how we do it.
All of the engines we race....all of them..4 cylinder, 6 cylinder, 8 cylinder, 10 cylinder our our 2 cylinder engines....are all 1 cylinder engines with one crank shaft.
A V8 is 8 single cylinder engines with one crankshaft...we run 8, O2 sensors, 8 spark plugs, 8 different cam shafts, 8 different compression ratios.
There is NOTHING the same about what each one is asking for or needing....other than..it is asking for what IT needs or wants.
You must remember that an engine is not in a static state..at "full song" every cylinder is different for MANY reasons...one is firing order.
One, is the cam is jumping forward and backwards...so cam timing is forever changing. Another is the crank shaft winds up and returns like a dish rag.
On the bottom end..the oil and windage is blowing and flowing into one bank of cylinders and totally splashing past the other bank of cylinders.
Plus all of the rings all seal differently, even like an identical pair of twins have totally different personalities.
Have you ever noticed how crankshafts used to be very symmetrical looking and now they have a "predicted" twist to the counterweights?
Piston used to be round in the ringland belt....now they are VERY ovate. I believe all 8 of them will need to have a different cam and barrel and ovateness.
It is like scaling a car....why do you preload anything? Because it will work better when it is running.
In most of the engines on these forums, we make everything the same when we dont know what it wants to be....
In our world an 8 cylinder engine will want different fuel, timing, compression and lash, etc...so that each child in the 8 cylinder family can do its very best to carry the collective weight....The family of cylinders, with all individual children, doing the best work each can, will be the most pwerful.

Once again...opinion here, mine and a few others....just look at it a little differently, and it looks different :)
 

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Am I reading this right? With EFI you guys are setting the fuel first and then the timing? I grew up on carbs with timing first then fuel... that's changed with EFI?

Even with carb i tune the fuel first, with the timing on a safe side
 

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The nitrous guy
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ok let me see if I can put this another way. we all know that to much fuel lifts ring lands. so we have a cylinder that you have to add 2* off timing to more than the other 6 and you have one that is way more efficient and you have three degrees out of that one. so your adding the 2* because for some reason that cylinder is not as efficient. why would you not take fuel away from that cylinder to increase its efficiency? maybe you take away 1.5% fuel from just that cylinder. does it go lean or does it now need the same spark timing yet now that you pulled fuel from it it is now making the same power as the average because its now not overly rich? it takes air/fuel to make power but how do you know your not adding timing to bandaid a inefficient cylinder?
You seem to be asking two different questions. I personally would not add timing to a rich hole in an attempt to burn that fuel. I try and get the hydrocarbon ring equal on all holes by eyesight in lieu of having 8 O2 sensors and do this with fuel trim. When I feel the fuel is evened out and attempt to add some timing, you always inevitably have a hole that starts showing unhappy from having a faster burn rate. It's at that point, we "doctor" up that hole with less spark lead, or in extreme cases, pull some power out of that hole by removing some fuel and nitrous.

MANY things can effect power hole to hole. It can be the intake, the air flow, the runner size or shape. A little difference in the chamber, etc...............it can also be something as simple as the quality of the ring seal or the valve job on that hole
 

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This is just my opinion and I am not claiming I am right...just how we do it.
All of the engines we race....all of them..4 cylinder, 6 cylinder, 8 cylinder, 10 cylinder our our 2 cylinder engines....are all 1 cylinder engines with one crank shaft.
A V8 is 8 single cylinder engines with one crankshaft...we run 8, O2 sensors, 8 spark plugs, 8 different cam shafts, 8 different compression ratios.
There is NOTHING the same about what each one is asking for or needing....other than..it is asking for what IT needs or wants.
You must remember that an engine is not in a static state..at "full song" every cylinder is different for MANY reasons...one is firing order.
One, is the cam is jumping forward and backwards...so cam timing is forever changing. Another is the crank shaft winds up and returns like a dish rag.
On the bottom end..the oil and windage is blowing and flowing into one bank of cylinders and totally splashing past the other bank of cylinders.
Plus all of the rings all seal differently, even like an identical pair of twins have totally different personalities.
Have you ever noticed how crankshafts used to be very symmetrical looking and now they have a "predicted" twist to the counterweights?
Piston used to be round in the ringland belt....now they are VERY ovate. I believe all 8 of them will need to have a different cam and barrel and ovateness.
It is like scaling a car....why do you preload anything? Because it will work better when it is running.
In most of the engines on these forums, we make everything the same when we dont know what it wants to be....
In our world an 8 cylinder engine will want different fuel, timing, compression and lash, etc...so that each child in the 8 cylinder family can do its very best to carry the collective weight....The family of cylinders, with all individual children, doing the best work each can, will be the most pwerful.

Once again...opinion here, mine and a few others....just look at it a little differently, and it looks different :)
I agree 100% George. A multi cylinder engine is just that, several separate engines sharing a common crankshaft to pass that power to the wheels(s). They all want something different. Those that can get the most out of each will be leading the pack.
 
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