MicroSquirt.com read only forum (Jan.15,2018)

Ive got 370cc injectors, What is the expected power I will get from them??

We need more info... things like how many injectors....

An integrale with 386cc/min injectors is fast approaching meltdown at 300bhp in the real world.

Guy.

Assuming you're tanking about a 4 cylinder (4 injectors), in a turbocharged application running no mor than 90% duty cycle, 250-270 BHP is a more realistic and safe figure.
Just for reference a stock Nisaan Silvia has 370cc injectors and pruduces 200 BHP.

Avner.

Ferret wrote:Assuming you're tanking about a 4 cylinder (4 injectors), in a turbocharged application running no mor than 90% duty cycle, 250-270 BHP is a more realistic and safe figure.
Just for reference a stock Nisaan Silvia has 370cc injectors and pruduces 200 BHP.

Avner.

They are nissan injectors, 4 of, 2.0 turbocharger

I was hoping for something closer to 300bhp, Cant I increase the fuel pressure to compensate??

Running about 4.5 bar fuel pressure (measured with the vacum hose disconnected fro the regulator) should increase the flow capacity to support 300 BHP - assuming that the fuel pump is powerful enough.
Keep in mind that all the figures I'm giving you are just estimates/guidlines, they sould point you in the right direction but must be tested with your engines and injectors.

Whatever you do, I suggest when you start tuning, try mapping the maximum boost/RPM/HP sites first. Start by checking that you can get the AFR you want (probably around 12:1) and continue by cheking that the duty cycle doen't exceed 85-90%. If You cant get near the desired AFR than you probably need bigger injectors, if you are in the ballpark and just need a little more fuel, to lower the duty cycle for instance, consider raising the fuel pressure.

Keep in mind that running high fuel pressure reduces the pump's flow capacity and shortens its life, unless it's built to work at these pressures.

In any case don't spend a lot of time mapping the low map/RPM/HP sites, only to discover later that you need to upgrade the fuel system. After the upgrade you will have to waste a lot of time remapping the low map/RPM/HP sites.

I hope this will help you progress in the right direction,
Avner.

thanks for that, very useful, A few more questions

What should I set the constants too (required fuel)?

I though when using MS you didnt need the regulator vac/boost connected?

The fuel pump Ive got fitted at the mo can easily do 5 bar of pressure but I am fitting an even more powerfull one in the very near future

Just use the "wizard" in Megatune, you enter the injector's flow rate and the engine displacment ant it sets the ReqFuel automatically.

You don't have to connect the vac/boost to the regulator but I feel it will be easier to tune with it connected. The only exception is aftermarket raising rate FPRs, that can be almost impossible to tune from my experiance.

Fuel pumps are rated by both flow rate and pressure. For example: fuel pump "X" is rated 200 liters/hour at 5 bar. The same pump can also work at 4 bars and will have a higher flow rate and it can probably work at 7 bar with a much reduced flow rate.

You can calculate the pump's required flow rate by multiplying the injector's flow rate by the number of injectors.

Fitting a pump that is too power can lead to fuel vaporizing in the pipes because it spends too much time circulating through the engine bay. Fitting a pump that is too weak can lead to lean AFR at high HP because it can't supply the flow required by the injectors.
Overall it safer to go with a too powerful than with a too weak pump.

Avner.

Ferret wrote:Just use the "wizard" in Megatune, you enter the injector's flow rate and the engine displacment ant it sets the ReqFuel automatically.

You don't have to connect the vac/boost to the regulator but I feel it will be easier to tune with it connected. The only exception is aftermarket raising rate FPRs, that can be almost impossible to tune from my experiance.

If I increase the fuel pressure doesnt that alter the flow rate?? If it does I cant enter 370CC in the flow rate box.

There used to be a calcutator on the MS website but I cant find it

As for the pressure reg, I have got an after market rising rate one

Since the ReqFuel is just the base number that is modified by the VE it doesn't have to be that accurate. You can enter the following injector flow insted of 370:

370*(New fuel pressure/Old fuel presure)^0.5

in other words the new flow if the old flow multiplied by the squre root of the new pressure devided by the old pressure.

I had a bad expreriance with a rising rate FPR the slightest change to the throttle position would send the AFR allover the place. I suggest you either disconnect the vac/boost or better still revert to the stock FPR.

Avner.