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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Mon Jul 11, 2011 12:10 pm 
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throttlehappy wrote:
I was linked this from rexnet, so forgive me for the necromancy :roll:

I have had a brief read through of what many think of the Tip-In Enirchment maps... however, I do believe that quite a few of you have failed to understand exactly what it is. I have been tuning Nissan ECU's for a few years now and I posted this on a Nissan tuning forum a while ago, so my apologies if it references people who are not members here...

Here is the important bit about TE tuning.

Not many of you have probably ever tuned an old carby fed engine? They had what was called 'accelerator pump', which fed in extra fuel when the throttle was initially applied to add extra fuel until the carby jets actually were able to suck in the extra fuel.

Now, think of it this way... your engine is idling away at the very lowest load cell of the fuel map. When you stab the throttle and TPS voltage increases to maximum, then it adds the largest amount of fuel(left TE cell value) Of course, if your already crusing at say mid load figures in 2nd gear and then give it full throttle, there is no way you need the maximum figure, it references the middle figure of the TE map. No if your near maximum load and go that extra TPS voltage to full throttle, it references the right most TE value. Of course, with so much load on the engine you are running a very rich AFR so there is no need for TE enrichment.
Now as Vader has posted in a previous thread, he was getting AFR figures all over the place. The reason being that his TE table was all over the place. Depending on which load cell was being accessed, it varied his AFR from lean/rich.

Hope this makes sense :)

Now, a few people are running modified intake systems with big diameter piping or aftermarket intake manifolds that flow better than stock. This is where TE tuning comes into its stride. By moving the MAF away from the throttlebody and increasing its diameter, you are increasing the delay before the MAF is able to respond. The engine creates a vacuum behind the MAF but draws in a MASS of air before the MAF can tell the ECU that you are consuming much more air. In this case, the figures would need to be increased slightly, although they do tend to run rich from the factory on this map

Look at a few dyno sheets and see how they can run lean at the very far left side when the power/AFR graph when the throttle is initially applied... This does not aid throttle response but adjusting the TE graph fixes this problem. There is no specific formula for modified intakes that I can give you(at the moment)except for trial and error. The same also applies to freer flowing air filters, where the engine can start moving the air with less filter restriction which 'CAN' result in a lower TE figure.

Hopefully, this has helped someone


So many people recalibrating their MAF's needlessly due to failing to understand that they are trying to calibrate something that does not need fixing. The 'airflow' over the AFM element is correct, they are just trying to compensate for the delay in air volume movement(unless the laws of liquid flow dynamics physics has changed recently?)

Less pressure drop across the TMIC core with a better TMIC and you can adjust figures as the airflow 'reaches' the engine faster etc. Of course, a long intercooler piping system with a FMIC means you needs to adjust accordingly as well(add s*** loads of fuel, since the MAF takes a while to register a vacuum behind the MAF moving from part throttle to full throttle changes etc) Throwing the AVCS system into the mix also vastly changes how the T.E tuning works, as your often blowing extra fuel right out the exhaust... with extra oxygen which can promote faster turbo spool. Also, in some Nissans where I have converted to a blow thru MAF, the T.E tables were obviously very lean due to the almost instant MAF response :)
I was even able to provide a injector calculation for larger injectors and what the T.E table should have done to 'repair' the mapping.

I am open to discussion on the topic. I would like to point out that I have ALWAYS modified my T.E tables to reflect the cars modifications. All of my Subaru tunes run stock MAF calibrations, with absolutely perfect tunes(air flow figures spot on etc)

Cheers,
Matt


You are correct for the most part. The TE table is there to add fuel due to the time delay from when the throttle is cracked and the maf voltage rises. The MAF doesn't detect a vacuum difference. It only is using voltage to reference the airflow. Most TE tables are only scaled to 30% give or take. So any throttle input over 30% gets the max amount of ipw. If your at 90% throttle and you move the throttle to 100% then you only get the amount of ipw that is in the 10% cell in the TE table. The ecu doesn't care about the throttle position, it only cares about the % delta to throttle input.

Also, when going to a fmic and longer piping, adding fuel to the TE table is not the answer. Its the time in which the injector applies the additional fuel that matters. Whether or not you need to add fuel or subtract fuel will mostly depend on injector size and would have nothing to do with intake size or how far it is from the throttle body.

I'm sure somebody will scream that increasing the maf size will require more ipw. It will globally, so you either have to increase ipw by lowering the scaler or adding to the g/s in the maf scale to compensate. The TE is only a adder and will be applied to the corrected ipw. You still have the same g/s air entering the engine, only the voltage vs g/s being seen by the maf sensor has changed. So no additional ipw in the TE table should be needed.


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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Wed Oct 19, 2011 4:41 am 
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As a matter of interest, rather than using a calculated value (throttle position 2 minus throtlle position 1 %) to see whether tip in was applied, and how much, would it not make sense to rather use tip in throttle % and last tip in enrichment?

I'm trying to finesse this part of the tune, since moving to substantially larger injectors thoroughly threw out the corrections on throttle stab. I've reduced the entire table by 40% (roughly the difference in size of injectors), but am sure that more localised changes need to be made. I find with the CAN logging you often get a number of rows with throttle identical - which makes me wonder whether it's not polling it so fast, that it's reading the same value. This makes the approach of throttle delta a little more problematic.

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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Wed Oct 19, 2011 5:22 am 
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Yes, I think you're on the right track with that.

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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Wed Nov 16, 2011 3:22 pm 
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http://www.chevytalk.org/fusionbb/showt ... id/206863/
This is an interesting read even if it isn't exactly Subaru stuff. They make a big distinction between enrichment due to increasing TPS and MAP.

Anyone have any comments on this?

Also, wtf is the boost error compensation table wrt tip-in enrichment? I've read description and I understand it but I don't understand how that table will help tip-in enrichment if the values for 0 and 1psi boost error is remove 50% of tip-in! That just sounds outrageous.

Also, http://www.hondata.com/techwidebandtuning.html is an interesting read for tuning techniques. They did mention setting the accelerator pump enrichment to zero while tuning the fuel table. Most likely, you have to bump this up later gradually till the car stops going lean. I have never tried to flatten my tip-in enrichment and tune up from there. Maybe I should?

http://forums.haltech.com/viewtopic.php?f=24&t=3450&start=15 wrote:
This map allows for the tuning of the amount of enrichment needed according to a given RPM and starting throttle position. In general more enrichment is needed at a low throttle position because a change will cause a larger in rush of air than at a higher throttle position. At a low RPM more enrichment is needed because of low air speeds and the atomisation of fuel is poor. This becomes less of a problem as the engine goes up in RPM and airflow increases.

The value in this table represents the enrichment needed at the maximum Delta Load. The maximum Delta Load is the largest change in throttle that you can make in the sample period of 10mS. In simple terms, this is the amount of enrichment for a full throttle opening as fast as you think you will ever open the throttle. Display the Transient Throttle Delta Load channel on a display or gauge to determine the magnitude of maximum Delta Load that you can achieve.

How do we adjust for tipping-in from low TPS versus high TPS?

Also, I haven't bothered to log just tip-in throttle % and see how it correlates to my real world accelerator pedal stabbing. Don't know how fast the ECU polls the TPS but I have a feeling that 40% throttle delta is a bit unnecessarily too high.

http://files.haltech.com/downloads/plat ... ottle.html

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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Thu Nov 17, 2011 2:35 am 
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mrf582 wrote:
Also, wtf is the boost error compensation table wrt tip-in enrichment? I've read description and I understand it but I don't understand how that table will help tip-in enrichment if the values for 0 and 1psi boost error is remove 50% of tip-in! That just sounds outrageous.


My stock ROM's boost target table was only reasonable above about 1psi. For the RPM/throttle areas that would be in vacuum, the target boost table was flat at 1psi.

So the boost error would be larger at high vacuum, and smaller at low vacuum.

So if boost error is used as tip-in compensation, you could get more tip-in at high vacuum (e.g. idle) and less tip-in a low vacuum. Which makes sense, since high vacuum would suck in more air than low vacuum.

That perspective makes sense to me... However the values that are actually in the tip-in boost compensation table don't make sense.... 50%, 50%, 0%, 0%, 0%.... WTF? There are a lot of tables in my factory tune that appear to have been crafted by someone who was in a big hurry. :)

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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Thu Nov 17, 2011 3:29 am 
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NSFW wrote:
That perspective makes sense to me... However the values that are actually in the tip-in boost compensation table don't make sense.... 50%, 50%, 0%, 0%, 0%.... WTF? There are a lot of tables in my factory tune that appear to have been crafted by someone who was in a big hurry. :)


Simplified explanation i sas follows:

Under high load\ boost a share in intake wall evaporated fuel is small in mixture balance, thus you should not wet the intake wall (and compensate a vapor share in balance) by extra (tip-in) fuel.

At high vacuum wall evaporated fuel may take 40-60% depending on injection phasing.


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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Fri Nov 18, 2011 1:09 am 
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Sasha_A80 wrote:
Under high load\ boost a share in intake wall evaporated fuel is small in mixture balance, thus you should not wet the intake wall (and compensate a vapor share in balance) by extra (tip-in) fuel.

At high vacuum wall evaporated fuel may take 40-60% depending on injection phasing.


That sounds like a good reason for a tip-in compensation based on boost, but these tables are based on boost error. Boost error could be close to zero at any boost level, if the boost targets are set carefully. But Subaru set up their boost targets to that when you are not in boost, boost error is proportional to vacuum strength.

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 Post subject: Re:
PostPosted: Fri Feb 17, 2012 10:25 pm 
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j87w wrote:
What point are you guys judging your A/F ratio when doing tip in? For a split second when I tip in my air fuels go to 18:1 then to 13:1 then it kinda bounces around. Then my car hestiates and like boggs when accelerating and changing gears (especially with the A/C on). I have only found one other thread about this and the guy blew his motor so he never figured it out (go figure). Its almost like it holds back then takes off then holds back. My car feels gutless when driving around except for cruising. Its an 06 STi with Deatchwerks 740cc Injectors.


Bringing this one back from the dead. Did you ever get this figured out? I have the same problem running Freon's SD with 1600cc injectors. I have a horribly rough area from about 2k-3k rpm, unless I am close to or at full throttle. I lowered my tip in by the correct % (due to larger injectors) but it didn't seem to make a difference. When I am either easing in to the throttle or stabbing it, my afrs go from 14ish to 18-20ish for a split second and the come back down to the normal range. Also when this happens I get some popping in the headers, like it goes really lean then dumps fuel in to compensate and explodes in the header. Should I try adding tip in or pulling it? I'm stuck.


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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Sat Feb 18, 2012 11:44 am 
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What other mods do you have?
I have a theory that says the more mods you do to increase airflow would require increasing tip-in enrichment, not decrease it.


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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Sat Feb 18, 2012 12:04 pm 
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dschultz wrote:
What other mods do you have?
I have a theory that says the more mods you do to increase airflow would require increasing tip-in enrichment, not decrease it.


Makes sense, I'm running a FP 3575 rotated kit with a 4" intake. Spearco TMIC, DW300 fuel pump, 1600cc Five-Os, TGV deletes with spacers.....

Thanks Aaron


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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Sat Feb 18, 2012 8:32 pm 
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dschultz wrote:
What other mods do you have?
I have a theory that says the more mods you do to increase airflow would require increasing tip-in enrichment, not decrease it.



Im thinking that might be right, ive been reducing tipin to suit 565 injectors from the 440 stockers and it hasnt stopped the flat spot I get when idling in neutral, then giving a quick blip to accelerator which gives me a stumble and then revs up. Now if I start the car dead cold and blip throttle the same, its perfect, no stumble, can do that for 30 seconds or so and then it starts to stumble again as choke comes off. Its not a major problem but I want to know why it does it, seems like when choke is on and getting more fuel it doesnt do it.

How did you work out increasing tip is better?, which does make sense if you have increased air flow to engine with good mods. You have to increase fuel everywhere else in the tune where you have increased airflow so why not tip in as well. Sounds good.


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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Sun Feb 19, 2012 11:27 pm 
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greyhairhoon wrote:
How did you work out increasing tip is better?, which does make sense if you have increased air flow to engine with good mods. You have to increase fuel everywhere else in the tune where you have increased airflow so why not tip in as well. Sounds good.

For me it's the result of a number of things. Watching AFR, feeling the car hesitate, knock as I get back on the gas after a gear change, and switching injectors (520 -> 740). When I changed injectors I scaled all the IPW related tables by a factor based on the injector size change, as is the common practice. But, I do have a few mods that are designed to increase my airflow (headers, catless-uppipe, highflow catted down-pipe and the rest of the exhaust). As I've been going along I've found increasing my tipin (after the initial re-scaling) back towards the stock settings has resulted in better responsiveness of the car.

BTW: I ran through the enrichment routine of the DBW 32bit ECU code (once) and it appears that, as defined, enrichment only happens if the throttle change % is above the threshold and that the calculated injector PW is also above the threshold. I think this last threshold is very important. If you change your injectors (go bigger) the IPW will be shorter to achieve the same AFR as you had before the change. So you must scale this PW threshold or your enrichment will not be applied for some small TPS changes.
Also, it appears the enrichment is calculated, latency added and then applied to all four injectors at the same time (batch firing). This would mimic the accelerator pump of a carburetor. It is in no way timed to the combustion cycle.


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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Mon Feb 20, 2012 5:12 am 
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Well Dshultz,

It makes so much sense to increase tipin when you have increased air flow. So I put my tipin scale back to stock for 440cc injectors then upped it 30%, roughty the difference of new 565cc injectors, flashed map and tested, flat spot 95% gone, upped tipin another 10%, flashed and tested. Brilliant, no flat spot, the car is so much better in traffic, on off accelerator etc. It revs freely from idle now with no flat spot at all. All this time I couldnt get rid of that flat spot because I was reducing tipin as per what is the accepted way. Ive been pulling out whats left of my hair trying to solve this flat spot for over a year.
I have similar mods to your car deshultz and have increased the airflow heaps over stock as well.
Thanks again Dshultz.


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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Mon Feb 20, 2012 8:33 am 
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Location: Bama, 02 wrx, stroked ej22t, pt5857, ppg, E85 (fear the ear) fastblueufo@yahoo.com
dschultz wrote:
greyhairhoon wrote:
How did you work out increasing tip is better?, which does make sense if you have increased air flow to engine with good mods. You have to increase fuel everywhere else in the tune where you have increased airflow so why not tip in as well. Sounds good.

For me it's the result of a number of things. Watching AFR, feeling the car hesitate, knock as I get back on the gas after a gear change, and switching injectors (520 -> 740). When I changed injectors I scaled all the IPW related tables by a factor based on the injector size change, as is the common practice. But, I do have a few mods that are designed to increase my airflow (headers, catless-uppipe, highflow catted down-pipe and the rest of the exhaust). As I've been going along I've found increasing my tipin (after the initial re-scaling) back towards the stock settings has resulted in better responsiveness of the car.

BTW: I ran through the enrichment routine of the DBW 32bit ECU code (once) and it appears that, as defined, enrichment only happens if the throttle change % is above the threshold and that the calculated injector PW is also above the threshold. I think this last threshold is very important. If you change your injectors (go bigger) the IPW will be shorter to achieve the same AFR as you had before the change. So you must scale this PW threshold or your enrichment will not be applied for some small TPS changes.
Also, it appears the enrichment is calculated, latency added and then applied to all four injectors at the same time (batch firing). This would mimic the accelerator pump of a carburetor. It is in no way timed to the combustion cycle.


So the Tau affect would play a big role in tip in. Since the injector is batch firing and some injections are getting sprayed on a closed intake valve. Having more time to evaporate into a more easily combustable mixture. That is interesting that the injectors would batch fire for tip in and not be added to final ipw for each injectors cycle.


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 Post subject: Re: Next Problem to be Cracked: Tip-In (Accelerator) Enrich
PostPosted: Mon Feb 20, 2012 10:00 am 
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fastblueufo wrote:
Having more time to evaporate into a more easily combustable mixture. That is interesting that the injectors would batch fire for tip in and not be added to final ipw for each injectors cycle.


This strategy allows enleanment to be compensated faster.


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