sevenin7

Hi guys. i m thinking to upgrade my secondary fuel rail with 1600cc Bosch ingectors . I use PFC . Its neccesary to use other resistors ?
Thanks.

shawnk

There are a few threads discussing that. I am sure mahjik will be along any minute to post a few links for you since your search didnt find them. In any case I am using the resistors. Many are and many arent.

sevenin7

Thanks Shawn
Do you have PFC ?

Railgun

Can I play Mahjik today?

https://www.rx7club.com/showthread.p...00cc+resistors
https://www.rx7club.com/showthread.p...00cc+resistors

The stock injectors are high impedence. 1600cc injectors are low. If you don't use the resistors, you run the risk of frying the driver in the PFC.

I just wired them inline on one side. Doesn't matter which. 10 ohm 1/2W is what I used.

the_glass_man

iTrader: (2)

Some people say don't use them, some people do. Dave@KDR says not to use them, so does Ralph@Groundzero. There have been cases of peoples PFC's getting fried for not doing so. Makes kind of hard to figure out who to believe?

shawnk

I do...

My setup:
www.3rdgenrx7.com

How-to:
http://rails.3rdgenrx7.com/keithshowto.htm

Shawn

RX794

I've been using my 1680cc injectors for about 2 years now, I drive my car everyday(it's my only car), and I've had no problems without the resistors. The injectors are working fine. 1600cc injector if you measure them are actually 5-5.5ohms resistance which makes them high impedience, not low, there is more info on this here:
https://www.rx7club.com/single-turbo-rx-7s-23/bosch-injector-colors-259968/

CCarlisi

I recently spoke (through a translator) to a Japanese engineer at Apexi that was responsible for developing the PFC. He apparently visits the US office a couple times a year. He said 2amps is the max that the injector driver should see.

Since Amps=volts/resistance
12v/2.8ohms (bosch 160lb injectors) =4.29 amps without resistors

With 6ohm resistors
12v/2.8+6ohm resistor =1.36 amps

With 10ohm resistors
12v/12.8=.94 amps

Stock injectors
12v/13.8=.87 amps

I also asked if Apexi in Japan can upgrade the pfc injector drivers so that low impedence injectors can be used without resistors. He said it is possible, but not something they offer at this time.

1point3liter

I used resistors on my old setup.

I was under the impression that there are high and low impedence 1680's available.

shawnk

and you would think a statement like the above would end the debate...

But alas this is the rx7 forum so I am sure it will continue.

Thanks for the good info ccarlisi. (not that I was headed out to rip mine out but I dont have to keep following these threads any longer)

Shawn

Fish

The 3 cars that I know of in the UK running these are using 10 watt, 10 ohm resistors.

No problems as yet.

Fish

damian

iTrader: (2)

everyone talks about the ohms on the resistor, but what about the watts rating, no one has mentioned what that should be? does that affect anything in this equasion?

i have seen everything from people not knowing to 1/2w to 10w? what is the scoop on the watts?

shawnk

I'm using 10 watt 10 ohm also...

Shawn

DaleClark

iTrader: (55)

IMHO it's a better idea to run the 10watt resistors. The wattage is the amount of heat the resistor can bleed off - IMHO the more the better. 10 ohm 10 watt resistors are easily available at Radio Shack for a VERY reasonable price.

Sounds like not running resistors puts the PFC on the edge of the amperage the injector drivers are handling. There's not a good reason to not run resistors - takes like a minute to splice them in, they're cheap, and you're typically wiring in new injector plugs for large injectors anyhow.

Dale

damian

iTrader: (2)

ok, so 10 watt it is, although i am going to try to get some that are less than 10 ohms, more like 6ish seems about perfect, basing that off the info i saw on another thread. someone posted that the pfc injector dirivers should not see more than 2 amps and had the equasions for the bosh injectors plus the resitors and the amsp it came to, 6 ohm resitor came to 1.36 amps, so it is well under the 2 limit.

DaleClark

iTrader: (55)

Radio Shack only has the 10ohm, 10 watt resistors, though . Myself and friends of mine have run those resistors for a LONG time on FC's with no problems whatsoever - they work great.

Dale

damian

iTrader: (2)

interesting, it looks like im gonna go with 25 watt now, after this understanding:

12V/6ohm = 2Amps

2Amps * 12V = 24W