I am about to run my S5 turbo vert, and I heard if you are not running a stand alone fuel system that the injector duty cycle will be thrown off if you use say, 550/850's. I have a modified ECU from RE Amemiya and have tweaked the car to make all the boost on the stock S5 turbo and intercooler. I want to get a BNR stage two or three eventually. Do I need to use matched pairs of injectors or is it ok to mix and match if you are only running an ECU. I think I read that the pulses of the smaller set will be too weak from the extra fuel being dumped by the second set if the second set is bigger... or should I use two sets of 7 or 850's anyway...
tks

 

I am trying to avoid the $ and hassle of a piggyback fuel management system since I am only shooting for around 300 RWHP on a cold day

 

You're gonna need some kind of fuel control. S-AFC, etc.

 

thanks for answering my question... NOT #$%@!!!
the ECU is already remapped for more boost

 

Actually the duty cycle for a given engine load and RPM (because IDC varies widely based in those) will be unchanged because the ECU has no idea anything's different. The injectors will flow more fuel for a given pulsewidth, and mixtures will be richer as a result, causing power to drop.

Do you know anything about that ECU, i.e. what exactly is "modified"? It's risky using a reproggrammed ECU unless you know exactly what it was set up for. It might require bigger injectors of a specific size, higher octane, a timing change, etc.

The primaries much match each other and the secondaries must match each other, but different sized primaries and secondaries are fine. Many people run like that, and FD's run that stock.

Er, no... The primaries have no effect on the secondaries and vice versa. They don't even spray into the same place.

 

ditch the re amemiya ... throw a stock vert ecu in and do an actual standalone .. i.e. microtech

I'm in the same boat as you. I have no management and I've cranked the boost up 3 psi more then normal (although it spikes to 10.5 which is scary).

Do it right the first time and buy large injectors i.e. 720 and 1200+(for secondaries) ... and tune from there. Otherwise you will find yourself replacing injectors and fuel management quicker then you think. IT ADDS UP AND IS EXTRA DRAMA YOU DONT NEED TO WORRY ABOUT !!!

 

Why would you want both...?

 

Hey, I have an idea, quit being an *******. I answered your question, it's not my fault you're an idiot.


I don't care if your ECU is mapped for more boost, how does that make it able to cope with larger injectors? You said it was tuned for a certain size.

If you put in larger injectors than even your maaaaagical ECU is tuned for, you will still have to have some kind of EXTERNAL FUEL CONTROL LIKE AN S-AFC OR STANDALONE OR SOMETHING.

 

why don't you admit that you just don't know if having two different types throws off the original balance? You might be right, that I will need a piggyback fuel mangagement system, but you just don't seem interested in answering my question so keep out of it. I didn't make this up, I did read it on some post here on this forum. I may go for a AFR gauge first who knows

 

What are you talking about? I've answered it twice so far.

What balance are you even referring to?

If you put larger injectors than the ECU is tuned for, which is what you're saying you're going to do, then YES, the "balance" will be thrown off and you will need to compensate with a fuel controller.

If you're referring to the fact that you're using two different sizes of injectors, then no, that is crap. People use different sizes of injectors for primaries/secondaries all the time and it works out just fine. Although in that situation, AGAIN, you will need some way to control the extra fuel. As the ECU is not setup for that.

Simple enough for you?

 

Look, if you plan on modding the car to get you 300+ hp, you MUST have SOME type of fuel management. Otherwise you are basically just kinda eyeballing how much fuel you are throwing in there. If you know how to tune the engine without the assistance of an S-AFC, GREAT! However, it's a hell of a lot easier with a fuel computer OR a standalone. Ditch the Modded ECU, I know it sounds cool and all but it's not what you are looking for. Get an S-AFC or a standalone and call it a day. The last thing you want is to throw on a BNR stage 3 and run way lean on that turbo and blow your engine up.