Start off – I’m not familiar with all the technical terms or names so please bare with me!

I have an rx7 s6 with standard Primary Injectors and 1700cc Secondary injectors and a Motec Fuel Rail (of course other mod’s but these are the only ones that matter in my situation)

I have been told that the PFC is for semi stock standard cars, not cars that have been highly modified. I have also been told, because of the 1700cc injectors having something like 7 or 8 o ring things (I forget what they are called) and standard ones only have around 4. This causes over time the PFC to malfunction and the injectors to over heat, which creates the car to run lean without noticing it, even if my tune in the car was perfectly done a few weeks ago.

So that leaves me with this satiation, I have been told I have only 2 options with the PFC.

1 – I can change the injectors and fuel rail back to standard, which should leave my car a bit more reliable and stop making the PFC running hot.

2 – I can buy bigger primary injectors and a different computer so I can achieve the above outcome.

I am not really keen on buying a new computer but at the same time, as I do like the PFC’s and I’ve just learnt how to use them, I don’t really want to down grade everything to standard either.

So my question to you guys – as I’m still only learning about cars – is there anyway that I can keep the PFC without having to change my fuel rail and secondary injectors?

I know I can put some heat things in the injectors, however if they blow out whilst I’m driving I wont be able to drive my car – which leaves me in a situation I don’t want particularly want to be in.

I also am going to start looking at Microtechs and haltechs for my FD. How are these on the rx7s? I’ve been told the Microtech is good, but the startups are very poor.

Please feel free to correct any information i have got wrong, as im only going off what ive been told.

Also any information / suggestions would be greatly appreciated to help me gain a better understanding so I can make my decision and get my car back on the road.


Thank you!

 

You have been somewhat misinformed. The problem with running low impedance injectors (which the 1700cc are) with the PFC, is that the injector drivers (amplifiers) in the PFC cannot handle the current flow required and will burn out eventually. This can be solved simply by adding a resistor in series with the injector to raise the impedance and lower the current demand.

This is a well known and documented procedure, so a little searching around the site should give you all the answers you need to know (search using 1600cc injector though). I'm not sure what effect adding the resistor will have on lag times and AFRs, perhaps Chuck (cewrx7r1) will chime in on that.

 

Adding resistors only slows the injector opening time which is like increasing lag.
The PFC has a lag adjustment which can compensate for it. Just add another .10ms.

If you had already AFRed the engine before adding the resistor, retest and only use the lag adjustment to make the fuel correction to get the full throttle AFRs back in range.

 

Ok, so instead of doing it the way mentioned above....

That means you could basically - Use the standard injector output, to trigger a transistor which will then trigger the output to the injectors.. that way the ECU drives are only switching a transistor rather than an injector?

Which logically this would be a lot easier to do..

(hopefully that made sense)

 

heh? You just wire a resistor in....it doesn't get much simpler or easier than that.

 

It would be easier for you to go buy a low impedance injector driver and install it between the PFC and the injectors.

 

Wouldn't it also be easier to just buy high impedance injectors in the first place? Or am I missing something?

 

The stock 850cc secondaries are the largest high impedance injectors on the market.