badass951

So why did Porsche have to be so special and manufacture a 5.5 ohm injector (I have also read 4.7 ohms, but I have seen 5.5 more frequently)? This does not make it easy for me to decide what the BEST aftermarket upgrade injector setup would be. I would prefer not to have to use ballast resistors, but it seems like that may be the only safe option. So far I have found a few low-impedence injectors online for reasonable prices. Hoping RC Engineering would be able to make custom injectors I called them and they offered me a 12 ohm, high-impedence injector. After reading a little bit and discussing some of this with Magown, I am not sure what I should do. I am definitely going to be making over 300 rwhp in the near future so keep this in mind.

What do you think I should do? The cheaper the better, however I will not use any low-qaulity parts on my car, just looking for a good buy.

Thanks!

Chris

Danno

Have a good talk with RC.Eng. about injectors, they have disassembled just about every injector on the market. Quick & dirty method is to use high-ohm saturated injectors. But that won't work very well because our DME puts out a peak & hold signal.

"What do you think I should do? "

Check out what every standalone EFI system uses with low-ohm peak & hold injectors....

badass951

Thanks for the advice. However, I do not want to go standalone, and want to stick with the DME. It seems most people are using ballast resistors, but I guess I was looking for a way around this. This is the first product I had to buy that is giving me a headache...

hacker-pschorr

I could be way off here, but the 928S4's can use Ford injectors. IIRC the 944S uses the same style as the S4's. Not sure on the 951's

badass951

So for all of you that have upgraded injectors, could you please tell me what a good injector setup to buy is.

Danno

I was subtly making the implication that all aftermarket standalone EFI systems use ballast resistors for impedance matching between the load and the driver transistor. Depending upon whether you drive the injectors individually per driver, or in paired banks or fully batched in parallel, you have to present a total load that's within the ranges allowed for that driver transistor. Check out Pages 36-37 of the MoTeC catalog.zip.

Now, we have to stop and ask why you wish to replace the stock injectors to begin with? I would recommend that only at the stage of upgrades when they are absolutely needed. On a non-S car, only when you replace the turbo will you need larger injectors. On a TurboS, if you go with a MAF/MAP kit @ 18-20 psi for 300-325rwhp, then you'll need larger injectors.

The other question also is how will you control fueling to be appropriate to the airflow? Just dropping in larger injectors, say 42#/hr units in place of the stock ones will result in 20% more fuel across the board under ALL operating conditions.

eman930

Danno, man you know your sh*t, If I have questions Im gonna come and ask you.

SoCal Driver

That's why he has all those young things fighting to keep his hood ornament warm!

badass951

I know exactly what you were implying (look at my second post in this thread). This is why I made a point to say that I was attempting to see if there was a way to avoid using ballast resistors.

As I already said in this thread, I will be at 300 rwhp or above with a custom turbo from Promotion along with numerous other mods. As you clearly stated, on a non-S car (mine is an '86) when you replace the turbo you will need larger injectors, so there ya go, I am upgrading the turbo.

My engine is currently being custom built by Promotion and is going to be custom tuned by them as well, so clearly I am not just dropping in larger injectors. Thanks for making me look like I might have been a dumbass though.

If you had taken the time to read what I actually posted there would have been no need for this.

Chris

Danno

I rushed through a little too quickly and didn't get all the meaning out of your message, sorry.

2+2

Badass, I dont know anything about ballasts but Lindsey appeared to have some that they claim does not require ballasts so you should check them out.

Also, many people do skim through posts...IMO, it would be beneficial to be a bit more understanding and clarify your post in a courteous manner. Danno was just trying to be helpful. In no way did he make you seem like a dumb anything. My opinion.
Good luck.