TheWoganSleeve

Hi all,

I have a to4r setup that did not have resistors. i now have fitted resistors. what should i change settings wise on my datalogit. i get 40% cycle duty and it seems to stumble and jump a bit at 4000rpm which has me a little worried?

Also say you had a setup with 1680 decondaries and the map was ok for that, what would you have to do to the settings if you downsized injectors to 1600?

and finally, would a mildly ported map work ok on a non ported set up if all else remains the same (or equal) in setup? what issues would there be

R-R-Rx7

iTrader: (24)

the difference of 1680 and 1600 are minimal since they are used secondary

you installed resistors,
you first have to make sure that your current injectors are LOW impedance and you increase the impedance of the injectors by adding the resistors as the power fc for the fd only runs high impedance injectors


the stumble in the 4000 is normal up to a certain extend... theres a transition setting on which it allows the secondary injectors to shoot a bit earlier or later depending on when you need it

Dudemaaanownsanrx7

iTrader: (23)

I'm pretty sure the the 1600's are 1680's people just refer to them as 1600's. If the car was tuned correctly without resistors adding the resistors means your map is getting less fuel. No map will be right for your setup even if they are identical. You need to get a proper tune for your car unless you're okay with a blown engine. It's very dangerous to just put a map on that you think is ok for your setup, at the very least you should have a wideband to make sure it's safe.

FixableUnknown

iTrader: (8)

Get rid of the resistors and go with a driver like the FJO.

Dudemaaanownsanrx7

iTrader: (23)

Nothing wrong with resistors, but you do need a proper tune. What size resistors did you go with anyway?

arghx

iTrader: (3)

If your 1600s/1680s measure at least 6ish ohms of resistance they don't need resistors. I explained the math in a 3rd gen forum thread. It has do with mathematical relationships in electrical circuits. Just because the stock injectors may read 13 ohms and some injectors read 3 ohms, doesn't mean you need 10 ohm resistors necessarily to bring the total back to 13 ohms. It has to do with how much current (flow of electricity) the injectors need and how much power (work over time) the ECU can really handle delivering.


I'm going to repost here the explanation I gave but it is mostly for anyone who may actually be interested in all the technical crap:

"Some of the 1680's actually read more than the usual 2-3 ohms across the terminals, although they are not in the 12-15 ohm range of the stockers. I've seen varying numbers. But there are a couple variations/manufacturers of the 1680s and you would have to check resistance across your 1680s first then calculate how much wattage you would be up to. By these types of calculations, I would say you would want at least 6 or 7 ohm 1680's to run no resistors. I am unsure which particular 1680s have the higher resistance values.

I'll explain and go through a calculation of injector wattage with the stock injectors, and then stock primary's and 1680 secondarys rated at 7 ohms resistance. The original source of the information for these calculations is from page 80 of the Datalogit FC-Edit manual.

The max wattage allowed is 3 watts. First let's go through the easier calculation using the stock injectors first, which we are going to assume all have the same resistance. We have two formulas:

V=I*R (Ohm's law. in this case voltage equals the injector's current multiplied by resistance of the injector itself)
P=I^2*R (Joule's law. In this case, the injector's power/wattage equals the injector's current multiplied by itself, then multiplied by the resistance of the injector driver transistor)


V=I*R .

let's set V to 14V , probably the max you'd get to your PFC on crusty 15 year old wires.

Let's say that all the stock injectors would have 12 ohms of resistance each, which is a safer assumption than the 15 ohms used in that document ^ .

V=I*R ---> 14=I*12 . I=1.17A. so each stock injector needs about 1.17 amps.

Now we take the 1.17 amps and plug it into our power formula.

At 100% injector duty, the wattage is P=I^2*R . We plug in the 1.17amps we just calculated as being needed for each injector. Then for the resistance, we use .25 ohms across the transistor. That .25 ohms is a given value that comes from that document ^ where it talks about "FETs [a type of transistor] rated at .25 ohms"

so P=I^2*R ---> P=(1.17)^2*.25 = .34 watts per injector.

So each of the stock injectors is going to use .34 watts . We multiply by 4 injectors, and we get:

.34 watts * 4 = 1.36 watts @ 100% duty cycle . Most people run up to about 85% duty cycle.

So 1.36 @ 100% duty cycle, multiplied by .85 , gets us the 85% duty cycle wattage of 1.156 watts. The max allowable is 3 watts according to the Datalogit manual.


Ok now let's do a calculation at 100% duty cycle for stock primary's and 1680 secondary's with 7 ohms of resistance. We just calculated that each stock injector is .34 watts . So multiply by 2 and we have .68 watts on the primary's.

Now we re-do the calculations for the secondary injectors:

V=I*R ---> 14=I*7 , I=2 . we are using 14 battery volts and 7 ohms across the 1680s . With a little algebra that gets us to 2 amps of current for each 1680.

P=I^2*R ---> P=(2)^2*.25 = 1 watt per 1680 injector @ 100% duty. We plugged in the 2 amps from the previous calculation, then multiplied by the .25 ohms that was given to us from the Datalogit document.

So stock primary's and 1680 secondarys (measuring 7 ohms resistance) at 100% duty gives us:

Front primary: .34 watts
Rear primary: .34 watts
Front secondary: 1 watt
Rear secondary: 1 watt

Total wattage at 100% duty: 2.68 watts . Total wattage at 85% duty: 2.68 * .85 = 2.278 watts . Max allowable is 3 watts.

So running a 550/1680 setup (secondary's measuring 7 ohms each) @ 85% duty would still put you significantly below the max power output of the injector driver circuit. Given the mathematical relationships though as resistance drops across those secondarys the current will shoot up quickly, so I wouldn't run much less than 6 ohms. Someone else can post up more details about the different brands of 1680's and what resistance they measure."

Dudemaaanownsanrx7

iTrader: (23)

The bosch 1680's are 5.1 ohm 2 or 3 ohm resistors would prob be ideal to keep things safe. I used the 4ohm resistors that came with mine. running without resistors would probably be okay, but personally its not worth several months wait and $150 to get the PFC repaired.

BTW the 1600/1680 are 160 LB/min injectors which calculate out to 1680cc (160*10.5= 1680)

TheWoganSleeve

awsome responses, once ive read this in full, got my laptop sorted for the wideband, ill give you some more detail of the way things are going. fantastic.

TheWoganSleeve

i have under advice bought 8.2 ohm 12.5watts, resistors.!!!! no wonder there is a mega stumble, will i be ok without then. i also need a digital multimeter really, but shoudlnt all boshes read the same resistance if they are 1680s

Dudemaaanownsanrx7

iTrader: (23)

They should but you need to check them to make sure they are 5.1 ohm. They should be ok without the resistors, the lower your duty cycles the safer it will be. Personally i would pick up some 2 ohm resistors, but if your alright with it'll probably be safe, then go for it.

TheWoganSleeve

Ill get rid of them tomorrow to see if it fixes the stumble. (also a new earth is needed from the boot back to the engine) where on the old datalogit do you make a time adjustment for the resistors? what kind of values are to be changed? ill open up the software now and see if i can find it. Cheers guys