<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JonnyCoupe &raquo;</TD></TR><TR><TD CLASS="quote">Your talking out your **** arn't you? If you have found peak torque what benefit do you get from advancing ignition then simply backing it off a few degrees?

Proper dyno tuning is steady state at each rpm and load site, so you dont care for the power, just hit the sweet spot for the torque and later when you do a 'pull' the power will come naturally due to several laws of physics that exist on our planet.

Do you tune with your dissy or sommat </TD></TR></TABLE>
No he isnt talking out of his ***. Just think about it....as rpms increase there it takes less time for one complete rotation of the crank. Just because the rpms increased doesn't necessarily mean the burn rate will increase. Therefore you need to increase timing to give the mixture the extra amount of time needed for it to spread and hit peak cylinder pressure at the right crank angle for best power.

 

Ah i see, hes refering to peak torque on the graph which is best rpm point for cylinder filling.

I was refering to a steady state load where you dial in advance to MBT, ie peak torque. That way you can do the rev range and get best timing at the rpm columns for the best torque. Backing off timing after peak torque (from both the point of reducing cylinder filling and crank rotational speed) makes perfect sense but theres not specific rule to know how much to back it off to keep the in the MBT region.

However holding a engine at full throttle with **** loads of boost at 7000 rpm to tune the ignition for peak torque is a risky area, heatsoak and a lean mixture can soon cause problems

 

Why an engine needs more advance as its speed increases

"When the compressed mixture inside a cylinder is ignited it takes time for the flame front to reach the piston and for the expanding gases to start pushing it down. The time that this takes changes according to a number of variables such as mixture strength, how well the cylinder has filled (dependent on volumetric efficiency and throttle opening), compression ratio and combustion chamber shape. Given the same circumstances of mixture strength, cylinder filling and CR, the time taken for the mixture to fully ignite and burn is the same regardless of engine speed. At increasingly higher RPM however, the time available for this burn to take place is correspondingly less, so it follows that you have to start burning the mixture earlier in order for it to push on the piston at the right time. This is the basis for increasing ignition advance.

Too much of this and the burning mixture hits the piston as it rises (pinking or pinging), too little and the flame front reaches the piston far too late and does not do a good job of pushing the piston down and the engine behaves like a herd of turtles. One of the reasons a diesel engine does not perform at higher RPM is that it has compression only ignition, so there is no way to increase the effective ignition advance. " - http://hometown.aol.com/dvandrews/timing.htm



"Most engines encounter the worst detonation in the rpm range where maximum torque is produced. Most import street turbos find this in the 3750 to 5000 rpm range, although this can vary widely depending on turbo matching. Since this range is mostly above where the engine is normally cruised, timing can be pulled back here without impacting economy. In fact, timing will usually have to be retarded below what is required for maximum power at high rpm in this rpm range. This retard will not be required on high octane fuel usually. It should be noted that most performance turbos make very little boost below 3000 rpm so detonation is usually not a great concern below this rpm." - http://www.sdsefi.com/techign.htm



No you don't see, he and everyone else are talking about the same thing, MBTT at peak torque.




Obviously it doesn't make perfect sense to you, since you retard timing FOR peak torque, not AFTER, and you ADVANCE after peak torque, not back off. AGAIN you generally CANNOT run MBTT where the engines natural torque peak occurs because you will more than likely detonate. SO THAT'S WHY YOU RETARD A FEW DEGREES LIKE HE SAID.



No ****, he didn't say there was a specific rule. He said that is the common practice, and it is.


LOL...........





Modified by LeGeND4LiFe at 12:38 PM 3/31/2006

 

What he said ^^^

This is all basic timing info. Dont clog this thread with lame questions. Check out the evans-tuning.com forums, read up, and come back. We're trying to progress here, not argue about known ideas...

 

could someone explain this to me then...before I made the det can it SEEMED like it was running nice and strong with these timing numbers...


...after I made the det can, I realized my engine was detonating...this was the outcome. I did feel some power loss. There still is a little detonation around 7500-8000rpm. One theory I have, is maybe my air/fuel is being contaminated by blow-by. I'm going to install 2 breather cans sometime soon and see if this fixes my "detonation".

 

Has anyone actually read thier plugs? I think there is a reason Longrace sells a 'spark plug light' that is really a 10x magnifying glass with a bright light on it.

 

Lol ive totally typed the opposite to what i meant. Indeed advance timing after peak torque, must be all the excitement today as we thought my GF was going into labour

Apologises for the pollution

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by See Are X &raquo;</TD></TR><TR><TD CLASS="quote">could someone explain this to me then...before I made the det can it SEEMED like it was running nice and strong with these timing numbers...

...after I made the det can, I realized my engine was detonating...this was the outcome. I did feel some power loss. There still is a little detonation around 7500-8000rpm. One theory I have, is maybe my air/fuel is being contaminated by blow-by. I'm going to install 2 breather cans sometime soon and see if this fixes my "detonation".
</TD></TR></TABLE>

Pull the plugs. Heres a good link on how to read them: http://forums.evans-tuning.com...ensor

Use a 10x magnifying glass and look. Remember that det cans are good, but high rpms introduce lots of noise and other things. If a brand new set of plugs reads clean where you think you are knocking, then you simply are not.

In my opinion, if you really were knocking, and I mean detonating, then you probably wouldnt still have your engine...

 

Excuse my ignorance, but I have a question in regards to the electronical knock sensor setup.

Can we nix the amp and just use the computer's sound card mic port? Sounds like a decent way to simplify things and save a few bucks.

I have a det can made and ready to go. I'll make one of these KS sensor thingers too and see whats what. Just need to find one of the flat response KS's for free or close to free.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nowtype &raquo;</TD></TR><TR><TD CLASS="quote">Excuse my ignorance, but I have a question in regards to the electronical knock sensor setup.

Can we nix the amp and just use the computer's sound card mic port? Sounds like a decent way to simplify things and save a few bucks.

I have a det can made and ready to go. I'll make one of these KS sensor thingers too and see whats what. Just need to find one of the flat response KS's for free or close to free.</TD></TR></TABLE>

That might be a good idea. Include some graphic sounds wave, by downloading something like winamp or something. I might try that, but it might also depend on the sound card? The quality I mean.


Anyone else think this might work???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by splitime &raquo;</TD></TR><TR><TD CLASS="quote">So yeah... it was uber simple to put together, but I do have alot of background static </TD></TR></TABLE>

I wonder if the stock KS does, too. I'd really love to hear one tapped from the stock KS pins @ the ECU.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHC_MShue &raquo;</TD></TR><TR><TD CLASS="quote">No he isnt talking out of his ***. Just think about it....as rpms increase there it takes less time for one complete rotation of the crank. Just because the rpms increased doesn't necessarily mean the burn rate will increase. </TD></TR></TABLE>

No, burn rate stays more or less proportionate to engine speed with iso-octane based fuel. Differing timing needs across the rpm band are in response to the amount of charge mass in the cylinder, and temps and other lesser contributors.

If you kids ever read any of the basic ICE literature, you would know this. Punks!

edit: I'd like to footnote this. While burn rate stays commeasurate, oddly enough it takes a certain amount of dwell time to detonate. If you spin the engine fast enough, and don't get stupid with AFRs or ignition timing, it's easier to avoid than at torque peak.


Modified by J. Davis at 1:24 PM 4/1/2006

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by J. Davis &raquo;</TD></TR><TR><TD CLASS="quote">

I wonder if the stock KS does, too. I'd really love to hear one tapped from the stock KS pins @ the ECU.

No, burn rate stays more or less proportionate to engine speed with iso-octane based fuel. Differing timing needs across the rpm band are in response to the amount of charge mass in the cylinder, and temps and other lesser contributors.

If you kids ever read any of the basic ICE literature, you would know this. Punks!

edit: I'd like to footnote this. While burn rate stays commeasurate, oddly enough it takes a certain amount of dwell time to detonate. If you spin the engine fast enough, and don't get stupid with AFRs or ignition timing, it's easier to avoid than at torque peak.


Modified by J. Davis at 1:24 PM 4/1/2006</TD></TR></TABLE>

That is why fastburn motors don't detonate nearly as much.

http://www.turbobricks.org/for...tmlio

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Matt Dupis &raquo;</TD></TR><TR><TD CLASS="quote">Well as we all know, when we compress a gas we increase it's heat. Similarly when we increase it's heat the volume tries to go up. Interestingly, if we compress it enough, it'll turn into a liquid, but that's not gonna happen to an internal combustion engine anytime soon. Whatever... the stuff that pushes the piston down is carbon dioxide, carbon monoxide, nitrogen dioxides, and water vapour. Notice the lack of oxygen? That's right - it's consumed by the fuel to create heat. Heat increases the pressure in the chamber, and the pressure pushes the piston down.

Elementary to some, repetitive to others.

Slight topic change, temporarily. Water can be a fuel too, when looked at properly. Water must go through a phase change to become steam, which has thousands of times more volume than water, and once it's all converted to steam, the temperature can increase some more by absorbing more energy from combustion, increasing volume even further. All this volume being contained within a closed cylinder, it creates pressure to drive the piston down. Because the water absorbs so much heat, more combustion energy may be created, or the combustion event may be advanced even further to develop more heat in a tighter space. What's that get you? More pressure.

So why am I going through all this? Rod/stroke ratio, baby. The long rod has more time at TDC, which leaves the chamber smaller for a longer period of time. This gives more time for energy to be absorbed by air, and for pressure to be developed.

Just before I started typing all this, I was walking my dogs and I had a bit of an enlightenment, which developed into this here post: If you can burn up all the fuel quickly, without letting any of it spontaneously combust, you can develop a substantial amount of pressure in a short time. This pressure doesn't go away until it's either cooled off, the chamber expands, or the exhaust valve opens.

So why is it that Kenny and so many others are taking 10.3:1 motors and are able to run higher boost at a lower elevation with more timing and less octane than I can at 8.5:1? They are burning the **** out of the fuel, without giving it a CHANCE to detonate. Once you get rid of all the fuel, it doesn't matter how high your pressure or heat is...

We've gone over it before, time and time again, and I think this only occurred to me now: a small chamber burns quickly and completely. A high pressure mixture of gasoline and air will combust quicker than a low pressure mixture. Combine the two and you can get rid of alot of fuel in a short period of time. The faster you burn it, the less time you give it for something to go wrong.</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cobra2326 &raquo;</TD></TR><TR><TD CLASS="quote">Remember that det cans are good, but high rpms introduce lots of noise and other things. </TD></TR></TABLE>

The human brain is a massively parallel sound processor, it is not some idiot 16 bit MCU that has to resort to DSP and must worship the glitch. If you hear knock, you hear knock.

 

Read that Dupis guy with a grain or two of salt. He seems observant, but he's incorrect.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Matt Dupis &raquo;</TD></TR><TR><TD CLASS="quote">the stuff that pushes the piston down is carbon dioxide, carbon monoxide, nitrogen dioxides, and water vapour.</TD></TR></TABLE>

1) CO2 is a waste product, contaminating the working fluid.

2) CO is fuel, and any existing in the exhaust stream is the result of incomplete combustion rxn.

3) Nitrogen (di??)oxides are the result of letting chamber temps get out of hand.

4) Water vapor aka wet steam is what pushes the piston down. Look at the pressure rise over time when burning fuel in a bomb - methanol/ethanol, that create water in one of the first combustion rxns, has an immediate pressure rise. Iso-octane, which does not produce water until one of the last combustion rxns, is mostly finished with the burn by the time chamber pressure starts to rise. Like it or not, the internal combustion engine is a steam engine.

Water is NOT a fuel, btw. You can use it to bring up combustion pressures at super lean AFRs where insufficient water is formed by the combustion rxn, and normally the engine would not run due to lack of combustion pressure. For normal AFRs, more water just acts as coolant, but in no way increases combustion pressure. Examine the existing body of knowledge on water injection.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Matt Dupis &raquo;</TD></TR><TR><TD CLASS="quote">So why am I going through all this? Rod/stroke ratio, baby. The long rod has more time at TDC, which leaves the chamber smaller for a longer period of time. This gives more time for energy to be absorbed by air, and for pressure to be developed.</TD></TR></TABLE>

Uh, no. Not just no, HELL NO.

More dwell at TDC = detonation heaven, and a very narrow powerband. Ask Vizard. Sit down and calc ideal rod angle and mechanical effort required to push the piston down... a shorter RS gives you and easier lever to push on + rotate the crank. There is also the aspect of the higher piston speeds associated with "poor" RS ratios... instead of allowing chamber pressure to rise into the detonation range, the piston falls away and acts and an expander.

If he wants a quick, clean burn, he needs to stick with a small bore. Look at the problems the D16 guys have with small bores, and super high combustion pressures that leave them knock-prone.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Matt Dupis &raquo;</TD></TR><TR><TD CLASS="quote">So why is it that Kenny and so many others are taking 10.3:1 motors and are able to run higher boost at a lower elevation with more timing and less octane than I can at 8.5:1?</TD></TR></TABLE>

Eh, sounds like the 10.3 CR engine actually has quench. Or the piston is a better design. Depending on how they arrived at that CR, the cam could be offset which is going to effect powerband/breathing through the head, and actual versus mapped ignition timing. There is no way, for a given engine with the same bore/head/etc configuration, that an increase in CR makes for a more detonation free engine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by J. Davis &raquo;</TD></TR><TR><TD CLASS="quote">
Uh, no. Not just no, HELL NO.

More dwell at TDC = detonation heaven, and a very narrow powerband. Ask Vizard. Sit down and calc ideal rod angle and mechanical effort required to push the piston down... a shorter RS gives you and easier lever to push on + rotate the crank. There is also the aspect of the higher piston speeds associated with "poor" RS ratios... instead of allowing chamber pressure to rise into the detonation range, the piston falls away and acts and an expander.
</TD></TR></TABLE>

You should expand more on this. Higher piston dwell at TDC seems like it can have BOTH advantages and disadvantages. Im no expert, but heres my reasoning:

With a shorter R/S, there is less dwell at TDC, but why would this be any better than more dwell at TDC? Think about it, advancing the timing further would result in the piston actually working AGAINST the mixture in a low R/S motor. In a high R/S motor, with more dwell, more advance will not cause the piston to work as much against the mixture, to a point. Obviously, this point will be sharper, but still.

Correct me if Im wrong, of course.

 

Your point about having the small RS setup's piston working against the initial burn is valid but practically insignificant with how the total package works. Notice the burn-pressure relationship of iso-octane I mentioned in my first (edit: second?) post on this page.

 

Wow, today I drove a long distance and noticed that same "rice falling on foil" sound at 7000 rpms! Timing @ 7k is 16.75*, afrs were 11.2:1 on my aem wideband. Looks like I will be pulling more timing as well, this sounded a lot like knock. Ill be dropping to 14.75* to see if that fixes my issue. scary stuff...

*update* I pulled my plug @ 14.75* @7k rpms when I heard a tiny "rice on foil" sound, and sure as anything, slight knock! Im now running 13.75* @ 7k+ rpms.


Modified by cobra2326 at 5:54 PM 4/2/2006

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by J. Davis &raquo;</TD></TR><TR><TD CLASS="quote">
No, burn rate stays more or less proportionate to engine speed with iso-octane based fuel. Differing timing needs across the rpm band are in response to the amount of charge mass in the cylinder, and temps and other lesser contributors.
</TD></TR></TABLE>

Wow! So you're saying that fuel automatically burns faster at 8k rpms than at 5k? Why? This is against everything Ive ever read, so lets hear more.

PS: I understand what you mean in your above post, I definitely need to do some research on the relationship between R/S and detonation, b/c it does make sense...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cobra2326 &raquo;</TD></TR><TR><TD CLASS="quote">Wow, today I drove a long distance and noticed that same "rice falling on foil" sound at 7000 rpms! Timing @ 7k is 16.75*, afrs were 11.2:1 on my aem wideband. Looks like I will be pulling more timing as well, this sounded a lot like knock. Ill be dropping to 14.75* to see if that fixes my issue. scary stuff...</TD></TR></TABLE>
so how much boost are you running now?

 

7.5 psi!!! I updated my above post w/ my final timing value. wtf???

funny though, my timing mark is now spot-on on my plug...

 

wow that is a lot of timing pulled out for sure. Even more than my sohc wants pulled out. Does it feel a lot slower at all? Possibly your base timing is off or you are getting oil in the combustion chambers?

 

I checked the timing with a timing light, and it was off by about 1* @ idle, looked like it was actually 1* retarded though, not advanced. The car doesnt really feel any slower, but the afr's dipped richer when I pulled 3*, lol

Im 100% that it was knock on the plugs, albeit light knock. Check w/ 10x magnifier and saw tiny black specs and a few tiny ***** of aluminum.

Also, my plugs dont look oil fouled at all, and it burns probably 1/4 quart every 3k miles (maybe slightly more). Ill find out more once I get a catch can...

 

hmmmmmmmmmmm :writes down on clip board:

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MidShipCivic &raquo;</TD></TR><TR><TD CLASS="quote">hmmmmmmmmmmm :writes down on clip board: </TD></TR></TABLE>

After this, I really think that 1.25*/psi is a good starting point. Most engines wont be as sensitive as mine, but starting off *knowing* that you are safe helps a lot. I started @ 1*/psi and ended up still being in detonation territory...

Update, Im not sure of anything anymore. Maybe the light detonation I was seeing was not detonation, b/c now Im at 13* total timing up top, and I still have that sound, not any less pronounced than before. 13* total timing is 1.5*/psi!!!


Modified by cobra2326 at 2:06 PM 4/3/2006

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by J. Davis &raquo;</TD></TR><TR><TD CLASS="quote">
1) CO2 is a waste product, contaminating the working fluid.
</TD></TR></TABLE>

So then using bottled CO2 to cool air charge is actually hurting an engine...?
or are you talking strictly byproduct of combustion...?