TheRotaryGF

iTrader: (3)

Ok, so I just recently finished my S5 NA to S5 TII swap and there seems to be a small issue with power in the upper RPM range. When I push the car and get above 6500RPM, it seems like it struggles to go beyond that. I think it may have to do with the injectors but I am not sure. Below is the info on the car:

I purchased the TII engine as a rebuilt, street ported engine with an upgraded oil filter pedestal and upgraded primaries. One set of injectors was light blue (700cc I think) and the others are the stock maroon 550cc ones. When I got the engine, it looks like there is a resistor box connected directly into the primary and secondaries. Fuel pump has been upgraded to a Walbro 255. ECU is a stock N370.

Now the question I have is, can the stock ECU manage the upgraded injectors ok? The previous owner was running a standalone ecu. If not, can the street ported engine run ok with all stock injectors? Also, I noticed that there is a fuel resistor box behind the front passenger light. Do I leave this disconnected if I am using the one that is hooked up directly to the injectors?

Any help on this would be appreciated. Thanks

Jason

Current Injectors

<a href="http://www.flickr.com/photos/jmartin/5648268558/" title="IMG_8138 by Nosaj_08, on Flickr"><img src="http://farm6.static.flickr.com/5065/5648268558_22b94554bd_z.jpg" width="640" height="480" alt="IMG_8138"></a>

j9fd3s

iTrader: (3)

what do you mean by manage? do you expect the ecu to do something?

chatchie

iTrader: (22)

Are you saying you have resistors on the injectors and also have the resistor pack?

Take a multimeter and check the resitance of all the injectors to make sure they match.

Lo imp. injectors (around 3 ohm) run a resistor pack, at least on s4's they do.

Your car should still run fine untill your secondaries come online, after that its gonna get rich (assuming your running at stock psi). Youll need some sort of fuel controller to lean/fatten it.

Get a wideband setup. Its money well spent and will let you know whats going on.

elmayimbe4eva27

iTrader: (2)

By manage, I believe he means Fuel Management. The streetport will run on stock injectors, but may run lean. Add a set of 720cc secondaries (At Least) and go for an RTek which will have a new fuel map for the upgraded injectors.

I'm not sure as to why he has 2 resistor boxes though. There should only be one. The box that is connected to the injectors directly, is it aftermarket?

You might want add an air/fuel gauge, just to make sure you're running the correct mixture.

TheRotaryGF

iTrader: (3)

Well, there is the stock resistor box that is behind the pass headlight. It says in the FSM that it is for the fuel pump but I have read on the forums that it is also for the injectors? The one that is connected directly to the injectors is a Denso ballast resistor. It was added by the shop that did the rebuild I think (Neptune Speed). I did buy a Prosport Air/Fuel ratio gauge but didn't realize I would need a different O2 sensor so I will be buying a wideband one and hooking that up soon. In the mean time, until I can afford an RTek or a standalone, is there any chance of damaging any components using the stock ECU with 700 primaries and 550 secondaries?

chatchie

iTrader: (22)

Put the 700s in the secondary. Not the primary.

j9fd3s

iTrader: (3)

the resistor box on an S5 is for the fuel pump. the S4 turbo and S5's can change the fuel pump voltage from 9ish to 12ish to change the fuel pump speed.

the early S4's have a resistor block for the injectors, but this is early S4 ONLY and not S5. its just a 12ohm resistor that lets mazda use 3 ohm injectors on a 15 ohm circuit.

so you need to measure the resistance of the injectors, anything over 10ohms is fine, anything under that needs a small resistor in the circuit to avoid drawing too much current and frying the driver in the ecu.

TheRotaryGF

iTrader: (3)

Ok that is good to know. Ill try to measure the resistance today.

Correction: 700cc injectors are being used as the secondaries. Ive attached an image below to show how they are hooked up to the resistor box. Two of the wires are unplugged in this photo but they are now hooked up correctly. I had to zip tie the wires to something solid because the connections were being pulled apart if anything pulled on the wires.


<a href="http://www.flickr.com/photos/jmartin/5650609594/" title="IMG_8084 by Nosaj_08, on Flickr"><img src="http://farm6.static.flickr.com/5064/5650609594_3b4474f124_b.jpg" width="1024" height="768" alt="IMG_8084"></a>

Black Knight RX7 FC3S

iTrader: (7)

if you are on stock ecu, with a 700cc in the secondaries, it will be too much fuel at high rpm when the secondaries kick in. That could be a reason as to why at high rpm you are feeling sluggish

RotaryRocket88

iTrader: (7)

Mazda gave the resistor pack a confusing name: "Solenoid Resistor" in the early S4 wiring diagrams. Not to be confused with the fuel pump resistor/relay.

The resistor pack is actually a set of four 6 ohm resistors, so each injector circuit is only 8-9 ohms total.

I'm not seeing any resistors in your picture; are they out of view? If those light blue injectors are aftermarket, they may be low impedance (2-3 ohm), which would require resistors. S5 OEM injectors will all be high impedance, and not need them. I'd also suggest solder and shrink tubing on the injector wiring; crimps can come loose.

TheRotaryGF

iTrader: (3)

Ok, I was finally able to get to measuring the injectors. The stock red injectors are being used as the primaries and are measuring 15.5ohm. The blue injectors are being used as the secondaries and are measuring 3ohm. The resistance from the resistor pack is measuring 7.5ohm; only the secondaries are hooked up to the resistor pack.

So, from what I can see, it looks like everything is hooked up correctly and I will just need to figure out how I want to manage the fuel at this point. Looks like Haltech is in my near future

Denso Resistor Pack
<a href="http://www.flickr.com/photos/jmartin/5667094749/" title="IMG_4004 by Nosaj_08, on Flickr"><img src="http://farm6.static.flickr.com/5106/5667094749_9c88cca3cc_b.jpg" width="1024" height="768" alt="IMG_4004"></a>