ignition timing and EGT's

[MRX]

I can see how there might be a brief moment of pressure, but due to the sheer volume of the CC at bdc, would it not have to have so much more mass of liquid to reach any significant pressure when compared to near TDC?

I am not trying to argue a case for incorrect ignition timing so much as I am trying to gain more knowledge by creating the opposing argument.

I'm not sure I understand the question. Do you mean volumetrically speaking would there have to be a lot of the air fuel mixture to create significant pressure?

And by all means pose questions. the more challenging the better because we all learn.

[dbsharp]

I'm not sure I understand the question. Do you mean volumetrically speaking would there have to be a lot of the air fuel mixture to create significant pressure?

And by all means pose questions. the more challenging the better because we all learn.

Lets just say that at bdc you have about 600 or so CC's Of volume, and at TDC you have 60-70 or something around there. It take a LOT more moles of matter at a certain temperature to make a certain pressure in a 600cc chamber than it does in a much smaller volume: near TDC.

Think about the Ideal gas law.
I know that combusting fuel air mix isn't exactly an idea gas, but It is close enough for the basic principal to still apply.

[d112crzy]

This is what I replied to the other thread we're talking EGT's in.

Think about it from this perspective: If you retard the timing too much the fuel that is ignited, although late, still gets ignited, correct? Well, think about the time it takes for the a/f mixture to explode under optimal conditions (perfect spark timing, pressure, and flame travel). Whether the mixture is ignited, at say 25* as opposed to 14*, doesn't change the amount of time it takes for combustion to start and end. This is called "burn time."

However, in regard to egt's there becomes a problem because if the mixture takes the same amount of time to completely burn and you are running retarded timing then you are igniting the mixture late, in reference to the piston's physical position (tdc).

If your piston is on its way down, your exhaust valves are going to be opening immediately proceeding or at the time of bottom top dead center. The a/f mixture, having been ignited late, is still exploding once the valves are open causing exhaust gas temperatures to raise due to the flame travel still not being completely done burning the a/f mixture. The piston is literally forcing the flaming mixture into the exhaust ports.

This is gravely important if you think about of the speed at which the pistons are traveling. The pistons travel so fast that for the time it takes the mixture to burn, the piston may be already on it's way back up to complete it's cycle. This means the explosion is pushing the piston down as the crank is forcing the piston upwards; Two opposing forces. This results in a loss in power and in some cases broken or damaged parts. Our weak point are our ringlands.

Its not necessarily the egt's, its the cause of the egt's that's the problem. The egt's are the indication that the timing is too far retarded or too far advanced. The combustion chamber can get past, i'd say, 1500+* F for gasoline engines. Possibly hotter. But exhaust gas temperatures are much lower than the chamber temperatures because of the distance it has to travel as well as the exposure to already combusted particles and the air in the exhaust stream.

The piston travels up as it's compressing air. If the timing were correct, it would fire a few degrees before it reached the top(depending on rpm). If the timing were retarded, it would fire just as the piston started going down already. If it were super retarded(what it sounds like you're explaining), it would have to be in the negative or around 0 for it to still be burning once the piston starts going back up for its exhaust stroke. IMO, your explanation is a little on the extreme side.

High EGT's mostly come from not enough air. If you don't have enough air, you're more than likely either running too rich and/or don't have enough ignition timing. Even if you have the correct a/f ratio down, you could have too little timing still causing those high EGT's. Adding timing will make for a better burn and lower EGT's because there is no unburnt fuel left for the next combustion event, which could cause predetonation.

I'll expand more tomorrow.

[WiKKeDV16]

Dbsharp..u stated that the ex. Valve is open during the pistons upward travel. Agreed, here's my counter..

Although the exhaust valve is open and there is a outlet source. How big is that outlet source really?.

How big are the primaries of either header or turbo manifold?.
So while you made a valid point that the mixture isn't being surpressed in such a tight enclosure..its still in an enclosure. Via it be a header/dp/exhaust. Or manifold/turbo/dp/exhaust.

The diamter of said outlets are a vital agent in why the combustion event has to be precisely timed.

I face this all the time when tuning cars with log manifolds. I feel I have to add more timing then what could be optimal for X engine. Just to eliviate the escalading egts. Running the higher risk of detonation.

I might of steered off in my reply...

Correct me as needed..lol its 3am..blah

[MRX]

This is what I replied to the other thread we're talking EGT's in.




The piston travels up as it's compressing air. If the timing were correct, it would fire a few degrees before it reached the top(depending on rpm). If the timing were retarded, it would fire just as the piston started going down already. If it were super retarded(what it sounds like you're explaining), it would have to be in the negative or around 0 for it to still be burning once the piston starts going back up for its exhaust stroke. IMO, your explanation is a little on the extreme side.

I'm going to explain things for the masses, so don't take offense to the things you already know. I'm just catching anyone else, who doesn't know, up to speed and saying the same things differently.

Since spark timing is a function of the crankshaft's rotation with respect to the pistons position. To run extremely retarded timing would be suggesting things like 0* which is TDC, like d112 said.

He is correct that my explanation is a bit extreme. But I did so in hopes that people could clearly understand the concept of burn time in relation to egt's. JUST for reference sake we'll state 20* as absolute perfect timing. Anything below 20* is considered retarded. Even if my above explanation is extreme, the same burn time principles apply. The burn time correlates the temperature
in the cylinder.

I was trying to imply was the more retarded the spark timing event is the hotter the air exiting through the valves is. The particles may be burned on the exhaust stroke, using lets say 15*, but there will be more heat exiting the exhaust valves because the heat resulting from the combustion hasn't had enough time to dissipate.

High EGT's mostly come from not enough air. If you don't have enough air, you're more than likely either running too rich and/or don't have enough ignition timing. Even if you have the correct a/f ratio down, you could have too little timing still causing those high EGT's. Adding timing will make for a better burn and lower EGT's because there is no unburnt fuel left for the next combustion event, which could cause predetonation.

I'll expand more tomorrow.

The following is just another way of stating what d112 said again (Although I do disagree that the a/f ratio is more significant than the timing):
Both scenarios of a/f and timing with respect to egt's actually lead back to my original theory of "burn time." Consider too much fuel and perfect timing
in this case. The burn time is actually increased because of the amount of air/fuel mixture that needs to be burned at the same temperature. There is more to burn so it will increase the burn time. Increasing the burn time then results in the air being hotter as the exhaust valves open.

[MRX]

Lets just say that at bdc you have about 600 or so CC's Of volume, and at TDC you have 60-70 or something around there. It take a LOT more moles of matter at a certain temperature to make a certain pressure in a 600cc chamber than it does in a much smaller volume: near TDC.

Think about the Ideal gas law.
I know that combusting fuel air mix isn't exactly an idea gas, but It is close enough for the basic principal to still apply.

I'll have to think about this one. The ideal gas law is applicable of course but I might have to include the adiabatic process in order to correctly answer your question.

[HondaFan81]

not that I can tell. The det I'm talking about is mild. I have to listen very close to hear it unless I am using my diy det can. My compression is a bit higher than a stock f22b also. I milled the head .020", and it could have been milled/ resurfaced before that. Just running the numbers through ciscos engine calc, that brings me up to 10:1 static compression.

I remember doing calcs for a friend and a .020" mill on F22B DOHC head would increase it from 9.2 to 9.4? Am I missing something?

[HondaFan81]

Interesting conversation guys. I have some questions for all you involved in this conversation dbsharp, MRX, d112, Wikked:


1) What tuning tools do you all utilize to set ignition timing properly on customer's vehicles (i.e. det cans, EGT thermocouples, read spark plugs, etc)?

2) What EGT range is considered "good ignition timing"? (specify temp units)


I hear these ignition timing conversations and little indications (like dbsharp using a DIY det can), but I don't hear people using tools for this constantly. I hear people using wideband, datalogging and some read spark plugs. Maybe it's me, but in the back of my mind I'm thinking someone that does tuning for a living is actually reading spark plugs for every vacuum vs RPM condition? That does not sound timely and would result in a large tuning bill, would it not? Sure you may do it on your own car, but on customers all the time?

That leads me to think that for efficiency, there has to be tools that are utilized. Do all you guys have EGT bungs installed or install them onto customers cars? Do you use a det can (don't know how this works or looks like yet)?

More insight please, thanks.

I have an EGT bung and EGT thermocouple with my Zeitronix wideband setup. I didn't want to install it into my Bisimoto jet hot coated header to ruin the coating in that area, but if I have to I will. If I start to pursue tuning, I will get a ZTX LCD readout and use that in coordination with the S300 for real-time tuning.

FYI on white project: I noticed the first tuner use some detonation device, seems like he attached to block. However, I did not notice the tuner use EGT and he only looked at spark plugs when they had rich foul out. If he had appropriate tools, he should have recognized he set my ignition timing values low or that something was wrong.

[d112crzy]

EGT's is just a tool, just like a wideband is. It doesn't even help more than a wideband.

Reading spark plugs IS the way to tune and if you know how to read properly, they tell you absolutely everything you need to know about that cylinder.

Yes, it is timely. This is why I recommend street tuning if you're going to get dyno tuned. I charge a flat rate fee for my services, dyno time is charged by hour. You don't need to look at spark plugs for every RPM vs vac section, just WOT. If you're on the dyno, you'll know when too much timing is too much timing because you'll stop making power, or make very little power for the amount increased. When that happens, back off 1.5 degrees is my rule.

DET's help you hear detonation that isn't audible, which a lot of it isn't. But if you check spark plugs regularly, you'll see event he slightest hint of detonation even if you didn't stap at the certain RPM.
But one thing a lot of tuner don't know, a huge amount detonation happens in the lower rpm's and under medium load, especially in higher compression motors. Most of the time due to way too much timing.

MRX, the reason I think that fuel isn't as significant as timing is because I've had detonation happen at 25* btdc, 3.5k rpm wot and be at 12:1 air fuel ratio. Then I went to 11.5:1 and I STILL had detonation. I retarded to 20* and it was gone. I leaned it out to 13:1 and it was still gone. This was back when I started tuning my current setup. I couldn't understand why with such little timing it was detonating like that, even on a cold night. But I guess we're talking EGT's here, not detonation, lol. little OT.

*OT**

I remember when I first started reading MRX's posts that are now the stickies in the Perf. Tech section. I only dreamed I would be that smart. now I'm here discussing this shit with him

[HondaFan81]

It's funny, I understand combustion and camshaft timing events, but I still don't have the confidence to tackle the tuning myself. What holds me back is my lack of experience. I also need to learn how the active ignition/fuel cells jump around with respect to driving conditions.

Josey, going back to spark plug reading, you say you do it at WOT. I realize you must first set your AFRs across the board, so these are set at about 13.0-13.5 for NA motor. Let's say the plugs give you indication of detonation in the recent WOT run.

1) How and what columns on the map do you adjust your ignition timing accordingly?

2) Do you just highlight that entire WOT run section and retard ignition timing by a couple degrees?

[WiKKeDV16]

It's funny, I understand combustion and camshaft timing events, but I still don't have the confidence to tackle the tuning myself. What holds me back is my lack of experience. I also need to learn how the active ignition/fuel cells jump around with respect to driving conditions.

Josey, going back to spark plug reading, you say you do it at WOT. I realize you must first set your AFRs accord the board, so these are set at 13.0 for NA motor. Let's say the plugs give you indication of detonation in the recent WOT run.

1) How and what columns on the map do you adjust your ignition timing accordingly?

2) Do you just highlight that entire WOT run section and retard ignition timing by a couple degrees?

Det cans/egt gauges/reading plugs.. its all part of it..

cisco.. grow cojones.. seriously.. start out slow. tuning partial throttle and vac percentages to get the hang of how your ems fuel/ign cells colaborate.

as for your question about reading the plugs..

heres the problem. you need to get your airfuel/timing were you think would be adequate (From previous adjustments) and install a fresh set of plugs..

go for a WOT run and immediately turn off car right after WOT run... pull over.. let vehicle cool (dont strip the threads of the spark plugs nignog) read plugs.. make adequate changes and redo the test..


see how time consuming that can be?


heres something i learned from tuning some evos.. with rom raider and it clicked into my head that this applies to all vehicles..

knock/detonation will ALWAYS happen... regardless of how flawless the tuning.. the condition.. there will ALWAYS be a knock event. so whats our goal? to limit these events to a tolerable status.. 0-1 knock counts per full cycle. these knock events are hardly audible.. the owner of the evo9 i was tuning had a nice ass DIY det can installed in parallel with the stock knock board. he wanted something to test against the stock setup.. which the mitsu engineers did a pretty good job on vs the honda knock sensor i must say.

the knock counts were in clear conjuction with eachother..

say i saw 6 knock counts at 4psi. i could clearly hear back to back detonation through the DET can.. now.. when the the timing was corrected so that the ems logger showed 0-1 knock count.. it was hard for me to distinguish if what i was hearing through the det can was knock.. or other engine noise.


my point is.. you cant try to eliminate the event of knock. just surpress it as much as possible.


grab your laptop and start playing.. unfortunetly there will be know real way for you to learn unless you get on the bicycle and fall.. this isnt to say your gonna grenade your engine.. just start slow my man.. your more than capable of doing it..

when i started tuning.. it was soley on principal..

i need X airfuel and Y timing.. and that should "run good" ive learned over the years its more to it than that... thanks to mrx/joser/zigenballz/piratemcfred/98vtec

learning were peak torque is due to timing curve developed... how to tell when adding more timing isnt doing anything.

etc..


till this day ive never grenaded a engine that wasnt due to poor engine conditions (not tune related) knocks on nightstands wood lol..





OT:

guys this thread and the other one is purely sex. it feels like the old days.. talking about something more in-depth.


FTMFW

[WiKKeDV16]

heres something i put together in hopes of helping you cisco





Red line = A WOT event from Idle

Blue line = a revving event while holding the same throttle position. the column position can vary dependant on the angle of throttle. obviously i used barely any throttle at all in the selected columnn(21vac)/(col2)

purple= raising rate event partial throttle adding more and more throttle till WOT is reached

hope that helps

[HondaFan81]

Thanks for the info C-los, unfortunately I can not view your images at work.

In regards to the 0-1 knock count and not completely eliminating it. Wouldn't the normal combustion event be considered a "detonation" event and could account for this 0-1? It's when you get more than one combustion event per cycle that is a problem, right?

According to all articles that I've read, they make it clear that detonation is not desired.

So would running an EGT and reading plugs be sufficient for ignition timing tools?

What is a normal EGT range for a F22ax NA motor?

Thanks.

[WiKKeDV16]

As I understand it..the combustion event can't be considered knock/det because its what is desired..anything beyond that..anything were not intentionally creating..is considered knock..because is happening at the wrong time/sequence.

Unsure of na egts..but on boosted engines my goal is 750-850.

[d112crzy]

It's funny, I understand combustion and camshaft timing events, but I still don't have the confidence to tackle the tuning myself. What holds me back is my lack of experience. I also need to learn how the active ignition/fuel cells jump around with respect to driving conditions.

Josey, going back to spark plug reading, you say you do it at WOT. I realize you must first set your AFRs accord the board, so these are set at 13.0 for NA motor. Let's say the plugs give you indication of detonation in the recent WOT run.

1) How and what columns on the map do you adjust your ignition timing accordingly?

2) Do you just highlight that entire WOT run section and retard ignition timing by a couple degrees?

The last two columns are the WOT columns, regardless of RPM(supposing your motor is healthy and does 0 vac at WOT). Depending on the RPM I stopped the motor at is where I'll make timing adjustments. On the street, I usually retard the entire WOT section by 1-2 degree depending on how loud the detonation was, or how bad the spark plug is "peppered".

And I agree with Carlos, quit being a bitch and grow some balls and tune yourself. You can read all you want, but that isn't going to get you anywhere. Start with the map you have already and go tune the fuel tables out more. You can't fuck it up unless you increase timing by a huge amount. Once you feel comfortable enough, add timing in slowly.