ive always had this problem with tuning using a MAP sensor.. basically the AFRs look good in boost at wot, but if I part-throttle it at same boost pressure, the AFRs will be too rich. I think this is caused by the computer not being able to measure the difference in airflow at different throttles, since it is only looking at map pressure. driving on street its not that much of a problem, but lately ive been tracking my FD and it causes rich misfires when i am at part-throttle, for example trying not to lose the rear end in a middle of a turn.

what is the common solution for this? would tuning VE instead of injection time fix it? although i dont see how, because the computer is still only using just MAP and AIT sensors to calculate fuel. i see there is a map correction option, maybe if i set the load sensing to TPS, then add MAP correction? has anybody tried this or have a base map for that? im open to any other suggestions

 

^Good questions there!

I always assumed that the problem would get "better" whenever I get to the fuel/timing maps by gear. Not that is a solution to the problem that you are talking about, but it would lessen the problem... maybe.

My thinking is probably way off tho!

 

For the Sport ECU, you could use TPS as the primary load source and use MAP compensation. VE based tuning will have the same issue if you use MAP as your primary load source. VE isn't the panacea some have made it out to be.

 

How were you able to eliminate the tune as a variable in this?

This sounds like a typical tune created on a Dynojet without the tuner or owner cleaning up the partial load areas by cruising up hills of varying grades in order to keep rpm and load as constant as possible and tune each cell (a pain in the ***).

The inertial load of the Dynojet is very hard to tune under partial throttle as unless you keep trying to accelerate that drum the inertial load drops away.

If you can get the car to a proper brake loading dyno like Dyno Dynamics, Dyna Pack or Mustang dyno you can hold each rpm point and tune all load points on that rpm and then move one to the next rpm range.

Also, you need to have a good understanding of the throttle pump enrichment settings. Not only enrichment %, but decay time and sensitivity can have a huge effect on fueling at partial load.

Last, you may think you are holding the throttle steady, data log it and the throttle may be all over the place, especially if you don't have race seats and harnesses. You may have to knock some sensitivity out of the throttle pump enrichment or really spend a lot of time making sure the enrichment is just right at all rpms, temps and loads so it doesn't matter if you are jittering the throttle.

Hallmark of a good tune is stock like driveability under all conditions.

But, to avoid most of this and as a band aid to an imperfect tune-

You can also just get a super amped up ignition and you won't have any misfires. I used a 2x CDI ignition amps and 2x LX92 coils for the leading spark plugs.

Car ran with on 720cc primary injector stuck 100% open and fuel dumping out the exhaust.
Car stumble/started on engine assembly lube with fuel pump and injectors disabled.
Car operated very smoothly with entire boost map richer than 10:1AFRs and did not gain significant power leaning AFRs out. This was left as the normal map.

Very high leading plug electrode wear- new plugs with oil changes.

 

There are different ways to compensate for throttle position. Some may be necessary depending on what the ECU you are using allows. Also, what you are trying to do may dictate what maps or how much of them you need to use.

This works on the double MAP requires double fuel logic of tuning. You can use an AlphaN (TPS v. RPM) fuel table and have a linear compensation table(2D) for manifold pressure. You can alter the Boost compensation table when you find you need more or less fuel as you increase or decrease the manifold pressure.

Once you start running higher boost settings you will find that your VE is changing and the AlphaN table alone will not allow you to tune for both low and high boost settings. The best way is a true 4D map. Two 3D tables, one for MAP v. RPM and a second for TPS v. RPM. You can tune the TPS v. RPM table as the main table and have a linear scale plus whatever inconsistencies you find in higher boost and RPM.

In a PFC where you cannot change the load axis of the main fuel table you will have to use the TPS compensation. It is a bit more complicated to do it this way but it can still be done.

EB Turbo

 

somehow this ended up in the wrong topic