well since i got my techtom and bin playing around with it, i notest that my injectors are running a little off, 2.00 in sted of the 2.40 the FMS recomends. but i do have the 370cc in and the JWT ecu with the t25 program, and i dont have the turbo in yet, would this set up make the injectors runn a little slow ? im thinking this is the reson why there off from the FMS values.
Am i right in thinking this ?

Well, my GUESS is that since you're running the bigger injector, it doesn't need to stay open as long to provide the same amount of fuel as the smaller injector right? So I guess it's all good.

Khiem

Nick,

I cannot figure out what exactly the 2.00 and 2.40 values represent. If you have a MDM100 then they should be ONTIME in milliseconds, otherwise it would be Duty Cycle in %.

In any case going from 259cc to 370cc injectors should roughly reduce the ON time (or duty cycle) to 259/370= 70% of the original value.

If the FSM specified 2.40 this would be 1.70 so it does not really "compute". 2.00/2.40 is 83% so (if the values shown can be compared, i.e. they are at the same rpm and load) you are presently running richer that before.

Chris

Originally posted by hpro123
Nick,
If you have a MDM100 then they should be ONTIME in milliseconds, otherwise it would be Duty Cycle in %. Thats right i have the MDM 100 and this is all at idel 850rmp


In any case going from 259cc to 370cc injectors should roughly reduce the ON time (or duty cycle) to 259/370= 70% of the original value.

If the FSM specified 2.40 this would be 1.70 so it does not really "compute". 2.00/2.40 is 83% so (if the values shown can be compared, i.e. they are at the same rpm and load) you are presently running richer that before.

Chris

hmm so how would i go about running the injectors
slower ? i do have a new o2 sencer and i think my MAF is running at the right voltage but ill dubble check that and ill check my TPS too i guess ?

Originally posted by Nick
Thats right i have the MDM 100 and this is all at idel 850rmp
OK, since the idle is steady at 850 why do you worry? Maybe the 200 value is OK. I suggest you warm up the engine, let it idle for 3-4 minutes, let it cool down and take the spark plug out. If it does not show any signs of wet fouling then there is nothing to worry about.


hmm so how would i go about running the injectors
slower ? i do have a new o2 sencer and i think my MAF is running at the right voltage but ill dubble check that and ill check my TPS too i guess ?
Again, why would you want to do that if everything is OK? Maybe JWT intentionally runs a little richer than stock at idle (although I cannot figure out why, the stock mixture is pretty rich at idle). If the rpm is at 850 then there TPS is OK in all probability. The MAF should be checked though since it may show more voltage at idle than the specification and in this case the injectors would behave like yours do.

Letting all speculation aside, there is practically no way you can trick the ECU into letting the injectors stay open for less time. You can always use a device like APEXi S-AFC but I do not think the cost is justified before you are sure there actually is a problem and even then JWt should be your first line of action. If the mixture is richer than it should/was supposed to they will probably reprogram free of charge.

Finally, where in the FSM did you find the 200 specified value???

Chris

Also, remember that wolf tunes everything rich.

jwt's programs are conservative-tend to run on the richer side. now as far as stock idle mixture being on the rich side thats more than likely to to the head design, which is common with the highport motors. The higher port heads tend to have more of fuel wash on the ports which cause the richer idle.

so there is no formula to convert MS to duty cycle? I wish the MDM used duty cycle:(

http://www.sr20deforum.com/showthread.php?s=&threadid=27056

Injector Pulse width at idle 259cc vs 370cc

Maybe someone with an *MDM or Apex AVCR can help out with stock injector duty cycle at idle with *259cc. What im trying to figure out is lets say I heard that the duty cycle (this is just an example) at idle is 2% with 259cc injector and stock ECU.

How much fuel is 2% of 259cc/min or 24.6lb/hr = 5.18cc/min or .492lb/hr

VS

How much fuel will be inexcess with everything the same except now 370cc/min or 35.2lb/hr with a 2% duty cycle at idle = 7.4cc/min or .704lb/hr

(259cc/min) 5.18cc/min vs (370cc/min) 7.4cc/min = 38.332% bigger

I really can't get this accurate until someone tells me the stock ECU duty cycle at idle with 259cc/min injectors.

The reason behind this is because I want to prove to my self that this is true and why my SAFC has to be leaned out at idle some 27% to be able to maintain 14.7 A/F ratio.

So no matter what, your car weather turbo'd or NA with bigger injectors, you will always need the the same amount of fuel required as when it was NA at idle with stock ECU and injectors, and for that matter probably holds true for the first
2,500 - 2,750 rpms because you really are not making that big a difference over stock. No wonder drivability just keeps getting better the more I lean out the first few thousand rpms of Low throttle driving and gas milage improve.

So I come to the conclusion that the one of the MAJOR difference (but not all) between a 259cc ECU and 370cc ECU is the modification of the duty cyle/injector pulse width at idle and the first few thousand rpms until the actual full 370cc is needed this why a stock ECU works pretty good in stock fourm except idle and the first few thousand rpms but once you get going the right amount is fuel (370cc) is now there but a little to much fuel in stock fourm.

Please correct me if I am wrong.

What I explained above totally jives with settings on the SAFC with stock ECU which are generally Lean to Less lean

1 2 3 4 5 6 7 7500rpm

Lean-----------------------Less Lean------------------Even Less Leaner

Originally posted by Nick
well since i got my techtom and bin playing around with it, i notest that my injectors are running a little off, 2.00 in sted of the 2.40 the FMS recomends. but i do have the 370cc in and the JWT ecu with the t25 program, and i dont have the turbo in yet, would this set up make the injectors runn a little slow ? im thinking this is the reson why there off from the FMS values.
Am i right in thinking this ?

2.40=2.4% of duty cycle

2.4 DC(259cc/min)=6.216cc/min = factory idle

2.4 DC(370cc/min)=8.88cc/min = stock ECU+370cc/min= rich idle

2.0 DC(370cc/min)=7.4cc/min = compramise, less rich than above but still not as good as factory idle

1.7 DC(370cc/min)=6.29cc/min = close to factory idle

Duty cycle can be checked with most digital multimeters by back probing the fuel injectors.

http://www.autospeed.com/A_0008/article.html

Don't let the reading on the multimeter throw you the vehicle they are testing is a SR20DET S15 I believe with Low Impendence injectors hence the 2.0 ohm reading and the 1.4% duty cycle and I believe the S15 has 450cc/min or so injectors hence the lower idle duty cycle 1.4% but this could also be do to low impendence injectors because they are way more acurate and true than high impendence.

http://www.autospeed.com/site/autospeed//images/0008_02mg.jpg

http://www.autospeed.com/site/autospeed//images/0008_03mg.jpg


My bad come to think of it I think its a Skyline because the Silvia S15 inj. are side feed and the skyline has low impendence injectors. Duh look at the engine.:confused: :eek:

Yeap thats an R33 Skyline not an S15.