Do I need a re-tune to run bigger injectors ?

NoFear99 said:

I'm running a custom tune from VF.

If I install those 525cc EV-14 Bosch Injectors sold by Phil because I want to change my 3.1 pulley for a 3.0 to push things a little bit more, do I need a retune to drive those news injectors or it just doesnt matter ?

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Why not just do the injectors and pulley at the same time, and then re-tune properly for both?

In general, injectors need a tune. Otherwise, your ECU is trying to drive the new, bigger injectors using the duty cycle and dead times for the old, smaller injectors, which means too much gas potentially at the wrong time (i.e. - running rich and potentially missing).

Depending on how far off things are, the ECU might be able to adjust long term fuel trims while it's in closed loop and get close, but it won't be "right."

At first, I was planning to only change the pulley because from a 3.1 to a 3.0 my boost pressure should only increase from .5 psi to 1 psi maximum. So if I'm fine right now I should still be fine with such a minor change.

My goal is to be at around 250-260WHP instead of 240-250WHP to be very close to a blade 300 level at 264WHP.

At that level of power I know my injectors duty cycle could be working between 90% and 100% into the high rpm range.

I do not track my car and only push it hard for short period of time.

I do not want to change the fuel pump but I'm willing to upgrade the injectors if absolutely needed.

NoFear99 said:

At first, I was planning to only change the pulley because from a 3.1 to a 3.0 my boost pressure should only increase from .5 psi to 1 psi maximum. So if I'm fine right now I should still be fine with such a minor change.

...

At that level of power I know my injectors duty cycle could be working between 90% and 100% into the high rpm range.

I do not track my car and only push it hard for a short period of time.

I do not want to change the fuel pump but I'm willing to upgrade the injectors if absolutely needed.

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Are you sure you want to run, even for a short time, at 100% duty cycle?
That tells me that odds are, you are likely to run lean!
(as a reference, but YMMV https://www.rbracing-rsr.com/calcinjpulse.html "Injectors should not be pulsed beyond an 85% duty cycle.")

Going to agree with Bri3d. Do them at the same time.

Like I said, right now I'm considering seriously to install bigger injectors also to better suite the smaller pulley.

But bigger injectors = new tune needed apparently.

Now I need to know if Jermaine ( VF ) has a tune for those bosch 525cc or if he is only used to work with the RC 550cc injectors setup....:scratchhead:

it is risky because if one injector stop delivery at 100% you run lean and could hurt the motor.

Basically any engine mod will benefit with a tune for optimum performance.

You need a new calibration with different injectors. Basically, you just need to tell the ECU what the new characteristics are like flow rate at a certain pressure and dead time at different voltages. No "tuning" is needed or beneficial until you change the pulley


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sturgeongeneral said:

Basically any engine mod will benefit with a tune for optimum performance.

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I agree with you but injectors do not give more power.

The purpose of bigger injectors is only to drop lower the duty cycle.

The oem 440cc injectors can do the exact same job as the 525cc at 250-260WHP but they may working too hard and may give it up on you.

My question was to know if my car is going to run like **** if I put bigger injectors without telling the ecu ( retune ) hey you now have 525cc weapons instead of 440cc.

NoFear99 said:

My question was to know if my car is going to run like **** if I put bigger injectors without telling the ecu ( retune ) hey you now have 525cc weapons instead of 440cc.

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yes. will run rich

I have the VF on my lotus with the larger injectors. When I took it on the dyno it came out to 260. I beleve I have the stock pully but do have a after market exhaust

Changes to the intake (beyond cup or standard airbox) or injectors require a different tune. Period.

The goal of 260whp is going to be dyno and condition dependant.

The Gotham tune is a Lotus Cup tune almost to the Tee. I'm certain they can change the injector scaler to 550 from 440, as I've seen them do that in their tunes. Outside of that, you'll still basically just have a Lotus Cup tune with a Gotham tune...

-Phil

NoFear99 said:

I agree with you but injectors do not give more power.

The purpose of bigger injectors is only to drop lower the duty cycle.

The oem 440cc injectors can do the exact same job as the 525cc at 250-260WHP but they may working too hard and may give it up on you.

My question was to know if my car is going to run like **** if I put bigger injectors without telling the ecu ( retune ) hey you now have 525cc weapons instead of 440cc.

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I’m not positive but I’m guessing the injectors running above 80% might also affect the fuel atomization and this could affect power.

LostPawn said:

I’m not positive but I’m guessing the injectors running above 80% might also affect the fuel atomization and this could affect power.

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This may be possible. It make sense.

Frankdavid4 said:

I have the VF on my lotus with the larger injectors. When I took it on the dyno it came out to 260. I beleve I have the stock pully but do have a after market exhaust

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What injectors do you have ? (RC 550 or Bosch 525 or DeatschWerks 550 )

What kind of VF tune do you have ? (The VF stage 2 or the Gotham tune. )

What kind of exhaust do you have ? ( Headers - midpipe - catback )

How come you dont know which supercharge pulley you have ?

Listen to Phil, follow the recipe, go fast.