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Discussion Starter · #1 ·
My other thread on part throttle a/f (http://www.team-integra.net/forum/display_topic_threads.asp?ForumID=10&TopicID=155114) has got me thinking about the relationship between richer mixtures and timing. Im not going to limit this discussion to only WOT conditions, but I think it is there that they are the most critical. Im also going to put a nice big disclaimer here that these are just my best guesses based on the material Ive read from various books, articles, etc. and that they are open for discussion, not to be accepted immediatly as fact.

So, from what I understand, richer mixtures keep the combustion chamber cooler, yadda yadda, but do they slow the burn speed down?If this is the case, more gas should also mean more timing. Has any experimentation been done with a slightly richer mixture and more timing as opposed to less fuel and less timing?

Feel free to post your thoughts, but prefereably, references or studies/dyno plots are best!
 

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If you want to slow the burn then you run a higher octane.... IE: c16

You are correct in your assumption though that with a cooler combustion you can advance the ign timing SLIGHTLY. When I say slightly I mean SLIGHTLY, half a deg or one full deg at the most to keep it on the safe side. In a boost application you will actually pull more timing and increase the boost. C16 allows you to make more power at a safer level keeping temps down. At the same time that you retard more timing you will be moving the "burn or combustion" and will need to watch your EGT's.

What you want to do is tune the car on a dyno. For tuning ignition you will want to be able to kill the car immediatly at the peak RPM to read your plugs....

To tune ignition you will make several dyno pulls, adding timing until you make max torque then back off about .5deg. This is called finding your motors MBTT. Your AFR tuning should be self explanitory. Follow the standard AFR table and you will be good.

I hope this helps a little at least. If you need me to clarify something let me know and I will do my best. It is sometimes difficult to explain myself while typing. Sorry if I am confusing you.

Are you tuning your motor yourself right now or are you trying to learn before you do the tuning. I am just trying to understand where you are coming from here....

I have always liked your posts.... you ask real questions compared to others out there. They are down and dirty tech questions. Good job on keeping T-I and myself thinking.
 

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Discussion Starter · #5 ·
Thanks. BTW, your setup is badass and I like it especially because it is unique. Its nice to see people trying new stuff instead of just shooting for 8000hp on a street car.

Anyways, I read that article a while ago and I have a pretty decent understanding of what happens with timing changes, different afr's etc. Basically Im just curious about what burn speed in relation to a/f ratio, if there is any such relationship.

As far as my setup. I've been N/A on a stock JDM b16a for a while. I have wideband and the ECU is chipped with crome. Ive been playing a little with the part throttle a/f ratios and temps, gas mileage etc. So Ive been street tuning the fuel maps for a while now, so that I can get used to the changes, etc. I probably wont touch the timing much without a dyno or some way of measuring changes in acceleration.

My turbo is sitting on the shelf right now waiting for a few more things, and once I put it in, Ill probably just retard the timing 1*/lb of boost and keep checking the plugs. I doubt Ill play with timing unless I get dyno time, but Ill nail the a/f to 12:1 on the street.
 

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Discussion Starter · #6 ·
From his article:

Rule two is that rich fuel will burn at a faster rate at the same engine speed.

When under load, the A/F mixture gets richer because the ECU adds more fuel to compensate for the excess air entering the engine, which is also denser.


Since fuel burns faster at a richer rate, the timing must be retarded to insure it burns right with spark. If it keeps the same timing as before, then the fuel would burn up too soon and you wouldn’t get a complete combustion.
I guess this helps to answer the question. Can anyone confirm this? If richer mixtures burn FASTER, we should be retarding the timing along with them. So on a boosted application, we should be able to run more timing at 12:1 than at 11.5 or 11:1, theorhetically?

In practice, the safest way is hands down to start with very conservative timing numbers, nail the afr, then advance slowly to find MBTT.
 

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cobra2326 on Jan/20/06 said:
So on a boosted application, we should be able to run more timing at 12:1 than at 11.5 or 11:1, theorhetically?


Yes because of the burn rate, you can have more timing. The article was written to help members visualize the relationships for what happens if you richen up your mixture with a piggy-back unit. It will automatically pull timing along with that.

Unless you have a standalone or a way of adjusting timing from the fuel adjustments, that is what will happen.

on a standalone unit, you will have seperate ignition tables from the fuel tables. Therefore you can have the timing adjusted seperately as can be seen here. It has comparisons of stock ignition map vs modified ignition map on same fuel maps.
 

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if you use one type of fuel while you are programming/tuning and then use a different fuel when you actually drive, the program becomes obsolete and is not suited for the new fuel.

This is why I cringe when I see people here in North America use JDM ECU's where 1) they run 100 RoN octane at the pump in Japan. 2) they run different emissions.

It's no different than (by analogy) tuning on 1 size fuel injector and then swapping injectors.
 

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sak:

I think you may have missed a major point in you piggyback article....

Trimming down your fuel with a piggyback will increase timing (advance) while adding fuel will decrease timing (retard).

I'll use this sample ignition map as an example...
(obviously not from a honda)


Timing increases with both RPM and vacuum. So, lets say I'm running 450cc injectors for a turbo setup and using the VAFC to trim down the fuel. Basically, I'm lying to the ECU and telling it that the engine is under a much lower load so that it will cut back the injector duty cycle.

The consequence of this is that it affects your ECU's ignition map as well. Lets say the engine is under load @100kpa MAP and 2500 RPM (on the above figure). This would be 22 deg. of advance. But if you're telling your ECU that you're running a lower MAP of 70Kpa (to cut back enough fuel) then you would have a value of 24 deg. of advance.

So, the bottom line:

Large fueling adjustments on a piggyback will affect where the ECU looks in the ignition map.

-If you add fuel trim, you're retarding your timing
-If you cut fuel trim, you're advancing your timing

(again, keep in mind that the above figure and numerical values are for a different engine)
 

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Thanks for the input Chuck, but we are saying the same thing.



No load on the left, load on the right. In other words, regular at the left, and rich mixture at the right.

The image shows that if you have load, richer conditions by fooling the map sensor, it will pull timing. Same thing as you said below:

Chuck Dean on Jan/21/06 said:
-If you add fuel trim, you're retarding your timing



And if anyone got that far, they would have figured that the opposite was true the other way around as you too pointed out below:

Quote: Chuck Dean on Jan/21/06 -If you cut fuel trim, you're advancing your timing


Thanks Chuck! Much appreciated info as always.
 

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Don't take it the wrong way, I really appreciate your input. More ways to look at it is always a good thing.

The whole pupose of the article was to help members understand what a piggy-back unit does to timing when they adjust fuel, which is the only thing the piggy-backs can do.

Cliff Notes for others:
Piggy-back = Bad

Standalone = Good!




Again, thanks Chuck!
 

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Discussion Starter · #14 ·
I honestly dont even see the point to piggy-back systems when much better engine management systems are available. A chipped ECU without datalogging (crome or uberdata) will cost you around $50 (if you have it professionally chipped). Compare this to the price of AFC, SAFC or another piggyback system and there is no point of buying a piggyback for MORE money. Hondata is another option with real support and will still cost you around the same as SAFC.

Anyways, what I did was buy the chip kit, datalogging and AEM UEGO and it cost me $400. I would argue that a $50 ECU chip kit and crome with a basemap will still give you much better engine management than a $200 piggyback system.
 

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Exactly the point in me putting up those articles to inform members here about the drawbacks and cost involved.

With the currect DIY setup's, there really no point in getting a piggyback if you can do more for cheaper.

 

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you have to understand that back in the day when I started we didn't have what you guys have now. Techtom/G-Power were the only guys around with OBD1/OBD2 Honda ECU based reflash reprogramming. That was expensive. The other alternative we had were standalones without basemaps. You started from zero on a blank sheet with no cold idle startup, warm up idle, part throttle closed loop, part throttle open loop, open loop. Plus you had to account to all the barometric pressure changes and ambient changes. It was daunting. We had Accel, Haltech, Electromotive, Motec which you can imagine was intimidating to a novice who knew zero about tuning. So the piggybacks were like magic for us back then because they were relatively easier to use and you didn't have to be an electronics geek to install them and use them. To us it was the best thing since sliced bread.


But times change. You guys don't know how spoiled you are now with all of these different choices of affordable reprogramming ECU kits and standalones WITH start up base maps and tech support.

So please put the piggyback in perspective and give it the respect it deserves for the reason it was created. It's for the low tech guy/gal who want some form of adjustability.

But you're right sak. These days, it'd be hard to justify getting a piggyback when you have so many ECU reflash programs and easier to use standalones for the Bseries and Kseries.
 

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MD brings up a very good point. Tuning an engine on a standalone w/o any kind of basemap can be a lot of work.

I have the convenience of having an engine outside of the car on an engine stand w/ dyno head attached. The amount of time we spent on the dyno is ridiculous. Additionally, you have so many compensation maps that affect your fuel map. There's barometric compensation, air temp compensation, engine temp compensation, accel "enrichment", decel "enleanment", cold start enrichment. So many variables. You have to be very careful about how you tune a standalone.

Piggybacks represent a way to "hack" a well-tuned engine (stock ecu).
 

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cobra2326 on Jan/22/06 said:
I honestly dont even see the point to piggy-back systems when much better engine management systems are available. A chipped ECU without datalogging (crome or uberdata) will cost you around $50 (if you have it professionally chipped). Compare this to the price of AFC, SAFC or another piggyback system and there is no point of buying a piggyback for MORE money. Hondata is another option with real support and will still cost you around the same as SAFC.

Anyways, what I did was buy the chip kit, datalogging and AEM UEGO and it cost me $400. I would argue that a $50 ECU chip kit and crome with a basemap will still give you much better engine management than a $200 piggyback system.


There once was a time where Uberdata and others were far from being well developed or trustworthy solutions, and OBD-2 to OBD-1 conversion harnesses sold for $200, so only AEM and Hondata were real options and they weren't cheap. That's how the VAFC + Boost thing became so popular. It was cheap, simple to setup, and it actually worked really well when you set it properly... you were just losing some power because of your inability to tune the ignition timing. I road raced a turbo LS with that setup for 2 years and the engine held together great and the car performed exceptionally well. I was extremely pleased with it, and it surprised even me.

The #1 thing people that screw up with the AFC is that they have zero understanding of the throttle points. Do not set them to 76%/77% or 98%/99%! Read the manual to see what it actually does. I had mine set to 20%/50% so it gave me a nice transition from the narrow map to the wide map as I was coming into boost. It worked really well.

But Uberdata is a realistic option now, so I picked up a chipped P06 ECU and a conversion harness for under $150... half the cost of a new AFC. It's a little flakey in some cases, but that's minor and I'm happy with it. It has some neat features, and I'll have mine setup so that I will have two programs on one chip and can switch between them on the fly. So, for this season, I'll have a better powerband, and the ability to switch between an aggressive qualifying/passing map and a more engine-friendly map to get me through the race...
 
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