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Fuel calculation question


Stimmer

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Hi, all

I got question about fuel calc, I have fuel maps from lots of ej engines and after pretty much time of tuning Vipec ecus, I've noticed, that my fuel maps

for Vipec seem to be very erratic even after I slightly smooth them out. If I compare them to motec or autronic maps, I can find them much more consistent.

I compare maps for the same engine. What is the reason?

Here are some screens of vipec and motec maps after light smoothing.

Thanks.

fuel%2520map_vipec.png

fuel%2520map_vipec_11.png

fuel%2520map_motec.png

fuel%2520map_motec_1.png

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Hi

Would need to see one of you PCL files to be able to look at all settings.

I would expect the mapping to be very much the same in terms of shape between all three units if all are set up correctly.

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What´s the fuel calculation method in this car? TPS or MAP as primary load source? Is the open loop AFR table enabled?

I´ve got TPS as primary load source (long overlap cams in turbo engine) and open loop AFR table is ON. This provides rather flat fuel table when the engine is on boost side.

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  • 1 month later...

Hi, all

Here is the best comparison of fuel maps. It is absolutely same car, I had free time on dyno, and mapped it to the same afr as it was with motec ecu, all other calibrations are simmilar

including avcs.

vipec_n14.png

Motec_n14.png

Maybe there are some spots where I did very rough tuning, but trend is clear.

And one more question, what is the difference between vipec, motec fueling and autronic? I tuned fuel in autronic ecu with only one sell in fuel table and target afr map.

It is impossible with vipec or motec. I think, that there is some kind of engine model, as tuner have to put CR in settings and injector parameters are rather strange.

P.S. Actually, I don't care what is the shape of the map, just want to know your thoughts.

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Hi, all

Here is the best comparison of fuel maps. It is absolutely same car, I had free time on dyno, and mapped it to the same afr as it was with motec ecu, all other calibrations are simmilar

including avcs.

vipec_n14.png

Motec_n14.png

Maybe there are some spots where I did very rough tuning, but trend is clear.

And one more question, what is the difference between vipec, motec fueling and autronic? I tuned fuel in autronic ecu with only one sell in fuel table and target afr map.

It is impossible with vipec or motec. I think, that there is some kind of engine model, as tuner have to put CR in settings and injector parameters are rather strange.

P.S. Actually, I don't care what is the shape of the map, just want to know your thoughts.

This is what Ray stated a couple years ago about "one cell tuning" (bolding is mine though..):

"Chris,

The engine would need retuning.

The only cells that would be close, would be any you tuned at 14.7:1

The AFR correction should always be turned on before tuning. It makes tuning faster as the values in the fuel table are flatter. You can tune a cell at 3000 rpm and 100kpa and then copy that value over the whole table and the tune will be quite close for most engines. You then just have to fine tune some of the cells.

With AFR correction turned on, the ECU uses the air fuel ratio you have in the target table to apply a correction to injector time. The basis formula is based on 14.7:1 air fuel ratio.

14.7 / Target AFR Value = Multiplication value.

Example:- 14.7 / 12.5 = 1.176.

The 1.176 is correction used to offset injector time to achieve the AFR value in the table, based on the number in the fuel table cell.

It is possible to have a fuel table with just one rpm and load cell. The engine will run the correct air fuel ratio at all other rpm and loads. There is a video by Ben Strader from EFI-101 showing an engine on a dyno with one cell and a full table of cells. The power produced is the same and the air fuel ratios are very close.

Using the target AFR table has other advantages. You can change the values in the table at any time after tuning and the engine will run the new air fuel ratio. No retuning is needed.

Also this table is very good when tuning engines with big cams or multi throttle bodies. You set the fuel table axis to TPS, and then tune based on TPS only and the ECU looks up the AFR table to know how to adjust injector time as the load (manifold pressure) changes. No 4D or 5D tables are needed."

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  • 4 weeks later...

Hm your maps looks pretty strange. I found 2 random maps on my computer. One off my private cars and one customer car, and they dont look that bad at all...

Did Simon find something odd in your map?

Audi90Q_zpsdef77cf5.jpg

Cosworth_zpsce180491.jpg

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  • 3 weeks later...

2 bsh

What engines are these maps from?

If they are not VVT, it may be the reason of such smooth shape.

My fuel maps are all from EJ20 DualAVCS engines. Maybe VE changes cause such shape due to dAVCS.

In fact car runs perfect an has huge torque and good power.

This discussion is just my curiosity.

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If you have a look at our V10 WRX maps in the latest VTS. These are off a stock V10 that we tuned inhouse.

TPS is the most common axis for vvt as it makes it a bit easier for tuning but you can also do it off MAP.

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