Fuel injection? Open or Closed loop?

[Mickey Whaley]

I thought you could only run 1 loop as the other would adjust the fuel for the weather?

[Ed Wright]

Micky, open loop makes no corrections.
Closed loop attempts to always correct to the values in the Target Air/Fuel ratio table.
I'm surprised at how many use closed loop in this poll.

[HawkBrosMav]

you guys might want to read the rulebook....

FUEL INJECTION
Fuel injection must retain OEM throttle body(s), plenum, and
manifold. If OEM throttle body(s) was equipped with electronic
throttle control (i.e., drive by wire), the throttle body(s) may be
adapted to mechanical throttle linkage if an aftermarket OEM-type
electronic-fuel-injection system is used. Larger fuel injectors
permitted, provided no modification or redrilling of manifolds is
performed. Electronic fuel injection must be closed, OEM-type
system; i.e., may monitor only engine functions. Monitoring of
vehicle performance criteria, wheel speed, driveshaft speed,
vehicle acceleration, etc. by fuel-injection system prohibited. All
aftermarket OEM-type electronic fuel injection must be NHRAaccepted. A current list of NHRA-accepted electronic-fuel-injection
systems is available on NHRARacer.com. Open-loop systems
permitted on production vehicles as equipped with OEM electronic
fuel injection. See General Regulations 9:1.

not saying it could be checked very easily but 99% of you are illegal running in open loop..

Brad

[Tom keedle]

as i read all this i'm reminded of some classes/training i've took over the years......when you go WFO, oem stuff IS in open loop.

[Ed Wright]

Originally Posted by Tom keedle

as i read all this i'm reminded of some classes/training i've took over the years......when you go WFO, oem stuff IS in open loop.

You are absolutely correct Tom. P.E. (Power Enrichment) mode is Open Loop. Closed loop target air/ fuel ratio is always 14.7-1 unless they have a Lean Cruise Mode. Then usually over 15-1 or leaner. Those are normally "Export" calibrations, as the cats used now are not efficient that lean. Most factory calibrations are actually overly rich in P.E. mode. Richer than we run our cars. Most GM calibrations are closer to 12-1 from the factory.

[KRatcliff]

Originally Posted by HawkBrosMav

you guys might want to read the rulebook....

FUEL INJECTION
Fuel injection must retain OEM throttle body(s), plenum, and
manifold. If OEM throttle body(s) was equipped with electronic
throttle control (i.e., drive by wire), the throttle body(s) may be
adapted to mechanical throttle linkage if an aftermarket OEM-type
electronic-fuel-injection system is used. Larger fuel injectors
permitted, provided no modification or redrilling of manifolds is
performed. Electronic fuel injection must be closed, OEM-type
system; i.e., may monitor only engine functions. Monitoring of
vehicle performance criteria, wheel speed, driveshaft speed,
vehicle acceleration, etc. by fuel-injection system prohibited. All
aftermarket OEM-type electronic fuel injection must be NHRAaccepted. A current list of NHRA-accepted electronic-fuel-injection
systems is available on NHRARacer.com. Open-loop systems
permitted on production vehicles as equipped with OEM electronic
fuel injection. See General Regulations 9:1.

not saying it could be checked very easily but 99% of you are illegal running in open loop..

Brad

Brad,

I am not sure you are reading that right. It says that it must be a closed system reading only engine functions, not driveshaft speed etc.... The "closed" system part of the rule doesn't have anything to do with "Open loop/Closed loop" as far as O2 monitoring.

The later part of the rule that you put in bold clarifies that.

[Ed Wright]

Originally Posted by KRatcliff

Brad,

I am not sure you are reading that right. It says that it must be a closed system reading only engine functions, not driveshaft speed etc.... The "closed" system part of the rule doesn't have anything to do with "Open loop/Closed loop" as far as O2 monitoring.

The later part of the rule that you put in bold clarifies that.

Yep. It says "closed system", not closed loop system .

[art leong]

Originally Posted by HawkBrosMav

you guys might want to read the rulebook....

FUEL INJECTION
Fuel injection must retain OEM throttle body(s), plenum, and
manifold. If OEM throttle body(s) was equipped with electronic
throttle control (i.e., drive by wire), the throttle body(s) may be
adapted to mechanical throttle linkage if an aftermarket OEM-type
electronic-fuel-injection system is used. Larger fuel injectors
permitted, provided no modification or redrilling of manifolds is
performed. Electronic fuel injection must be closed, OEM-type
system; i.e., may monitor only engine functions. Monitoring of
vehicle performance criteria, wheel speed, driveshaft speed,
vehicle acceleration, etc. by fuel-injection system prohibited. All
aftermarket OEM-type electronic fuel injection must be NHRAaccepted. A current list of NHRA-accepted electronic-fuel-injection
systems is available on NHRARacer.com. Open-loop systems
permitted on production vehicles as equipped with OEM electronic
fuel injection. See General Regulations 9:1.

not saying it could be checked very easily but 99% of you are illegal running in open loop..

Brad

Some stock systems run in open loop. Till certain parameters are met. The turbododges are in open loop at wide open throttle.
We are not illegal. I had went through an NHRA electronics teardown. And they had asked it I running open loop.

[boostedf22c]

Open loop.

Unless you have an o2 sensor for each cylinder (with correction factors to support each cylinder) then you could argue some advantages to running it closed loop.

[Bobby Fazio]

Open loop is probably better for bracket racing consistency I would think because the car doesn't adjust itself going down track.. however, would closed loop be better in a heads up run or when you need that extra power if the car is properly tuning itself downtrack? Has anyone ever tested to see which method was strictly quicker?