Vipec V88. Table for quick throttle close?

[07_wrex]

Hey guys. I have been tweaking my tune here and there on my 2007 Subaru STi. The one thing I cannot find or seem to get right is when I step on the throttle fairly heavy and then let off quickly for a shift. Obviously once I let off the throttle and the throttle plate slams shut, the fuel required for acceleration is no longer needed for that split second when the plate closes and causes the car to go super rich. 9.9-10.2:1 AFR. It is so excessive that 90% of the time the car will backfire slightly upon pressing the gas pedal in preparation for the next gear.

So, is there a table similar to the accel fuel table that does the opposite? One that removes fuel quick enough that this doesn't happen?

This only happens when I'm trying to be quick about gear changes and when I go from more than 40% throttle to closed for the gear change. If I accelerate and then slowly ease my foot off the throttle and then shift, it doesn't happen. This tells me that somewhere or some setting in the ecu is not quite right for a shift as fast as I am wanting under the conditions of 40+% throttle to quickly closed for a shift to the next gear. It is most notable in the lower rpm with quick heavy shifts. If I am super easy with it, it does not happen. But I'm not wanting to compromise being able to shift quickly when necessary. I feel that this is not a driving habit issue because this is the only car this happens with. My others have no issues performing flawlessly with the same driving conditions.

Thanks for any help.

-Sean

[Dave Kriedeman]

Hi,

do you have Overrun Fuel Cut activated in your PCL file.

This can be found under the FUEL tab.

Regards

Dave.

[07_wrex]

Dave,

It is active. I was under the impression that this is fuel cut for extended periods of engine braking. I have no issue with that part of it. The injectors shut off as they should when the thresholds are met.

I suppose I could set the activation delay to a really small value. 0.1 second maybe? It is currently at 1 second.

Thanks,

Sean

[lekonna]

where is your map sensor located, what kinds of lines you use ect.?

what does your fuel map look around the rev area on vacuum where you are experiencing this?

i'm guessing it might be delay on the map sensor readings or then the fuel map has too much stuff

on the vacuum area. its a nice effect tough, suits the rally car i think

[07_wrex]

The map sensor is bolted directly to the intake manifold near the throttle body. It is in the stock location. I have attached my fuel map. The sensor is very quick to read. I don't notice any lag that would suggest it is reading in the wrong when this happens. It's not the injectors because this is my second set. My first set were injector dynamics 1000cc and now they are Injector dynamics 2000cc (2250). It happened with both sets. I have been experiencing this issue from the start. It is nothing new that has come up.

Am I correct in that I am not missing a table? Could I setup a table to correct this behavior? My old aem v2 standalone had a table for both accel fuel and decel fuel. Meaning it would inject more fuel depending on the percent of throttle change and rpm for accel (obviously) and it would do the opposite for decel. As in when my issue happens (going from 40+% throttle to closed quickly).

Thanks.

[lekonna]

took a look at my logs from the standing mile event, i get the same spike on the AFR during the changes.

http://zonediscgolf.fi/media/supra/kenttaveto_logi.PNG

[07_wrex]

So I'll have to live with it I suppose. Dangit. Haha.

[07_wrex]

Lowering the delay for overrun fuel cut has helped quite a bit actually. I set it to 0.1 seconds. I think I was compensating for that issue with accel values that were too low. Along with lowering the delay, I was able to raise the accel values back to where they should be and the car seems quite a bit better. Not perfect, but much better.

[ssddaa]

flat shifting or gear shift cut control, but you need digital input for clutch

[07_wrex]

flat shifting or gear shift cut control, but you need digital input for clutch

re you suggesting I use those tables to fix this issue?

[Dave Kriedeman]

Hi,

have you ever tried turning Overrun Fuel Cut off and tuning the decal fuel.

I sometimes do this to tune the high vacuum areas of the fuel able that are never reached.

Turn off Overrun fuel cut , find a hill with a nice long down hill gradient.

By selecting different gears on decal coasting down the hills you can hit the high vacuum fuel cells and tune them to your target AFR, normal stoich or around 15:1.

You can manually tune this with someone else driving or datalog the downhill decent and use TPS or MAP as your trigger,

Example active from TPS value < 5 % or MAP <30 Kpa.

This way you can go back through your datalog and manually tune these sites.

Another thing you can try is to play with is the Ignition Transient Retard settings.

Have a play and see how you go.

Regards

Dave.

[Dave Kriedeman]

Hi,

may i ask why your DBW target table has the low values in the O% low rpm row, is this to help your idle speed control or something.

Also looking at your injector dead time values it would appear you are running around 50 psi fuel pressure.

Regards

Dave.

[07_wrex]

Dave,

It is supposed to help the engine idle. Would it be better to set those to 0 and use the idle speed control as the only means of idle control? Other than idle ignition that is.

My fuel pressure is right around 50 psi base pressure.

[Dave Kriedeman]

Yes, it is preferred that your 0 line should be all 0 values.

Closed FPS 0% however the engine is idling at at X rpm which will make it run in a different fuel cell area,

You should really tune your DBW settings correctly as having values other than 0 can create issues on decel fuel.

The Target table shouldn't be used as an idle correction table.

Regards

Dave.

[07_wrex]

I will change everything above 2000 rpm to 0 (at 0). When you say decel, are you referring to decel fuel? As in the opposite of accel fuel? Is there a table I'm not seeing? That's what I was asking initially. My overrun fuel cut works like it should and I have no problem with it if that's what you're referring to. Just making sure we're on the same page. Its the fast throttle close when I shift that causes it to go super rich. I understand the injectors can only shut off so fast maybe? But if I try to shift really fast (climbing a hill trying to catch the next gear so I don't lose momentum) it loads up fuel and pops and then goes like normal. I'm trying to get rid of that. Its only below 3000-3500. Maybe I'm just too picky.

Thanks,

Sean

[07_wrex]

Also, the part about the other values in the 0 row helping idle is from the vipec help file. Though it should definitely be 0 from 2000 rpm and up.

[Dave Kriedeman]

Hi,

If you have values other than 0 at the 0 axis, you must remember that the throttle blade will be open x amount dependant on your target table versus FPS.

Obviously the Throttle blade being open slightly will have an effect on the TPS voltage also,

So if you look at your DBW target table from 3000 rpm back to 0 rpm your cell number increases, the ecu will see this as the throttle is opening and therefore if not setup correctly the ECU will add acceleration enrichment as it is seeing the TPS value increase as the rpm reduces.

I add 3000 rpm into the equation as from 3000 rpm set at 0 and the next site is 2500 rpm has a value of 1% so the ECU will interpolate between the 2 cells.

So a combination of this along with your overrun fuel cut settings may be contributing to your issue.

There can be lots of contributing factors, so really you need to log the parameters such as TPS SUB and Main, FPS SUB and Main, Ignition angle, VVT value, engine RPM, AFR, MAP, MGP, etc.

The parameters that can or could influence this should be logged and studied.

Sometimes when trying to find annoying issues I disable extra fruit (controlling parameters etc) and simplify the setup and slowly creep back up onto my final combination, taking a step at a time and evaluating the impact on the engines behaviour.

You have a lot of controlling variables on your engine, which is perfectly fine, however as an example it could be a single simple PID value that is not quite right and create small little niggling characteristics than can be frustrating to yourself the end user.

Regards

Dave.

[Dave Kriedeman]

Also, the part about the other values in the 0 row helping idle is from the vipec help file. Though it should definitely be 0 from 2000 rpm and up.

This is correct and is OK to do, however you must check that the Throttle enrichment settings cant activate during these rpm and tps settings.

I prefer to have all of my idle control parameters etc setup correctly to obtain correct idle speed and have the DBW TARGET SET TO 0 at the 0 AXIS.

Using the idle ignition timing table can also add to more refinement here.

I personally never use idle speed error as an idle ignition timing axis.

Regards

Dave.

[Dave Kriedeman]

Hi,

I forgot to add, when I refer to decal fuel I am referring to the high vacuum load sites in the fuel table.

For example if you where coasting down a hill in 4th gear with your foot off the throttle and your engine was running at 40Kpa, you then downshift to 2 nd gear for more engine braking or getting ready to reaccelerate as a passing move on slower traffic.

When you down shift to the lower gear you will enter higher vacuum sites of the fuel table that may not be tuned for example 15 Kpa,

I realise over run fuel cut is there to help take care of this, but I am trying to point out some other underlining contributing factors.

Regards

Dave.

[07_wrex]

Dave,

Thanks. I was just making sure I wasn't missing an actual decel fuel table. My aem stand alone had one that was the opposite of accel and separate from the main fuel table. I will try to play around with it when it dries up here.

Thanks,

Sean

[ssddaa]

re you suggesting I use those tables to fix this issue?

that will definitely fix your problem

[Dave Kriedeman]

Hi Sean,

does your engine have tumble valves?.

You have some very complex ignition timing control setups in your PCL file.

You have obviously spent a lot of time setting this file up for your engine.

Regards

Dave.

[07_wrex]

that will definitely fix your problem

Lol. Its only active at 90%+ throttle. I know I can change that, but why would I? Obviously flat foot shifting the car would stop the issue because I'm now avoiding actually letting off the throttle for a shift...that's not going to fix the issue unless I'm racing someone. Maybe explain what you mean unless you're joking.

[07_wrex]

Hi Sean,

does your engine have tumble valves?.

You have some very complex ignition timing control setups in your PCL file.

You have obviously spent a lot of time setting this file up for your engine.

Regards

Dave.

Dave,

I do not have tumble generator valves. Those are long gone.

I have spent quite some time on my pcl file. I have an ethanol sensor and have set it up to be completely pump and go, so to speak. Base fuel and ignition maps for regular 93 octane pump gas. And then all the overlay tables for various situations vs ethanol content for e85. But I'm sure that's exactly what you could tell by looking at it.

I'm pretty proud of it. Lol. Just trying to fine tune it. The car made 711 whp on a mustang dyno at 41 psi. (817 ish on a dynojet).

Thanks,

Sean