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Ecu programmed for smaller injectors than im using

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Off topic..Looking for some insight.

I have a Rx7 fc and the guy that had it before me got it tuned from a local rotary shop and iv noticed that the injectors are programmed as

(690 primary)&(990 secondary) injectors

Which I didn't think much of until I removed my intake the other day to see that I have

(Id 725 primary)&( id 1000 secondary)

So one question is, what reason would anyone tune down injectors on a heavily modded Rx7?

And secondly. If I were to simply program the injectors to what they actually are in the ecu(725-1000). Would I have to re-tune the whole fuel map due to the extra flow??

I just don't see why there set up like this..


hey Tramd93,

I have seen tuners typically input the injectors about 5% less than what they really are because injectors never truly flow what they say they do. This gives you a good buffer zone. if this was a very high end build what they could have done is had them flow tested and put in the values (averaged) that they got back from the tests. Issue with that is that as the injectors age they will not flow the same as when they came from the factory or the test.

If you LTFT and STFT as well as AFRs under load do not appear to be off I don't think I would change them

That is all been on my evos. I never got to retune my rx8 before it got totaled so I couldn't say if that's common practice for rotaries or just in the evo community. I hope someone can pop in here and give a more definitive answer.


What ECU is this? Power FC? What is your base fuel pressure? Check it by looking at a fuel pressure gauge, key on and the yellow connector on the passenger side strut tower jumpered with a wire. The ID injectors are rated at 43.5 PSI (3 bar) and it's possible that he is only running 40psi, so he down rated them in the software.

Also, some injector characteristic data is given for a "calibration" fluid of a different specific gravity than the fuel you may be running. Can you post the injector characteristics data for the injectors?

EDIT: the values used appear to be the values for 40 psi base fuel pressure. If base was 43.5 psi you would use 715

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