cruisin

iTrader: (1)

Hey, so im running a MSPNP 1 and and RX7 460cc injectors on a 1.6 batch fire. It runs pretty good considering its MS1 and rx7 injectors.

One on going issue i am having is that as the car gets hotter my AFR's at idle and low load <30kpa go leaner then what i have normally tuned for. So as i get to operating temp and my coolant is 90-95 celsius for the first 20 mins or so things are normal; idle is 900rpm +/- 15, 13.3ish afr, ego only corrects by 1 or 2 % and off idle its fine. Then after driving for 30 mins and engine is hotter my coolant seems to mostly stay in the 97-99 celsius range; idle afr is the same but now with ego having to add 7-8% and off idle as well, and it just runs a bit rougher and more misfiring not as stable as before. IAT does not heat soak much, maybe only a few degrees if i sit long enough while running. It will increase by 10 degrees or so during a hot lean restart, but then it leans out to a 16 AFR even with gammae 100% and the PW being around the normal 1.6-1.7 range im used to seeing during a good idle. Same thing for when engine gets hotter, idle PW looks normal but needs more ego to maintain it.

Im running the injectors with 1.0 dead time and .10 voltage correction, 195 thermostat with 205(96) fan on temp, fan is on when coolant is hotter at 97-99 temps and i do see voltage drop a bit from 14.1 to 13.6-13.8ish. Not sure if that is enough of a voltage drop to lean the AFR out that much and it should be compensated for with the voltage correction. Or can some fuel vaporize in the hot intake manifold before it enters the cylinder?

Anybody have any idea what can be causing this issue?

Onyxyth

iTrader: (2)

I'd run a log and look for a few things. Look at Fuel: Total Correction to see if the software is pulling full at all.

Then Isolate that by looking at, Fuel: Baro, Fuel: Warmup, Fuel: Air Cor to see which is pulling fuel specifically.

Post your tune and a log of it happening, then others can review.

cruisin

iTrader: (1)

Thanks for the reply!

With MS1 there is not much to look for. I set up my air temp correction so Gammae and Gair are always at 100% so no correction. I dont have baro correction, so nothing affecting fueling there. PW's look normal during running and hot restarts, yet ego needs to compensate alot more then normal to maintain target AFR and even tough AFR is the same it runs rougher slightly. It develops a bit of a hunt and starts misfiring a bit. I have read about the injectors heat soaking theory, which is possible here.

I dont see much possible differences to compare between logs, nothing stands out to me. Other than ego needing to compensate more.

stefanst

iTrader: (1)

As the underhood temperatures of your car climb, the coils on your injectors heat up and increase resistance. This means less current flows and your dead-time increases. Your injectors effective opening duration decreases and therefore your engine is running leaner. Get decent injectors or adjust idle to be stoich when hot and deal with rich idle when cold....

cruisin

iTrader: (1)

Thanks for the reply!

That makes sense, since i cant see anything else causing this. Is this a problem with the bosch EV14? I have a set on the way.

cruisin

iTrader: (1)

Hey stefanst,

Can you explain this a bit better. Are you saying the injector gets less voltage when they heat up? Wouldn't the dead time go lower from less voltage? Even though my PW at idle is still the same, it still somehow gets less fuel? Not saying your wrong just trying to understand this better.

Is there any injectors you would recommend that are less affected by this issue?

SpartanSV

You will have the same voltage going to the injector.

Injector dead time is how long it take for the injector to start allowing fuel flow after it has been energized.

The resistance of the coil inside the injector increases with temperature which causes a longer delay before the injector opens. Hotter coil=Longer dead time

Modern injector designs like EV14s are less susceptible to the problem.