AFRs different in open and closed loop

[GTMcoupe]

Brief Car Spec
Honda B18C4 transplant into a Kit car here in the UK
Skunk 2 inlet, exhaust, no other mods
PLX R500
NO ELD so wire not connected to anything


When tunning placed ecu in open loop, and WB output from the PLX was connected to the O2 pin on the ECU and the fuel maps adjusted to suit my setup it would seem i have had to remove alot of fuel in the lower parts of the low cam table to achieve good afrs.

Now happy with map, I wish to put the car into closed loop, so disconnect WB and connect the NB output from the PLX into the O2 input on the ECU and make associated changes to the cal file, All genarally seems good from the display on the R500 on cruise afrs are 14.7 etc, put when i connect to the ECU i notice the Short term trim is high, above 30% and apears to stay there all the time, and some times when idling the afrs will suddenly go very lean, this is when the short term trim suddenly returns to zero.

So to check i put the car back into open loop and connect the WB to the O2 again, do a datalog and the lambda overlay looks as it did before very good. back into closed loop high short term adjustments.

atttached is my cal

Cheers
WEST

[Spunkster]

You should be tuning with the car in closed loop with the WB signal being input into the ELD and the NB signal send to the O2 input. You may also have a wiring problem or are getting interference that is interferring with the NB signal reaching the ecu corectly.

[GTMcoupe]

You should be tuning with the car in closed loop with the WB signal being input into the ELD and the NB signal send to the O2 input. You may also have a wiring problem or are getting interference that is interferring with the NB signal reaching the ecu corectly.

in ref to the closed loop statment

how come it clearly states on the parameter page under closed loop options just under the closed loop check box

When tunning place the ECU in open Loop

as surely tunning in closed loop will mean the ECU will be self adjusting effecting my datalogged afrs?

Cheers

[Spunkster]

That is to eliminate any corrections while on the dyno from long and short term fuel trim, but your final tuning should be verified in closed loop and all street tuning and part throttle tuning done in closed loop.

Wiring instructions to do this properly are at
http://www.hondata.com/techplxwiring.html

[GTMcoupe]

I have that docuemnt saved.
but thanks for the info

I had not seen anywhere in any of the documentation/info i had the details of leaving the ECU in closed loop specifically for part throttle tunning,, I thought the placing of the ECU in Open loop was required for ALL tunning of the ECU not just for when the car would be in open loop if selected or due to parameters i.e column 6 [650mb] and above. thanks for clearing that detail up.

Just been out in the car with the ITR base low cam map supplied in S300 and the short term adjustments are where you would expect +/-10% :D and the PLX is confirmng the afrs are floating as should around 14.7 under part throttle.

So I have a new question
How would you part throttle tune an engine from scratch which you want to run in closed loop? would you construct an educated guess base map, and go for a drive in closed loop and do a s.trim Sensor overlay? as datalogging the WB output would be useless due to the trimming done by the NB. and using the strim overlay to make the required changes to get the s.trim down to the minimum i.e +/- 10%

thanks for your time Spunkster

WEST

[Spunkster]

I wouln't try to create a map from scratch. I would use an existing map that is close to my setup to begin with.

[GTMcoupe]

Ok how would you, yourself tune the closed loop part of the map, like i said above with using a strim overlay, or just by turning the trim down to zero within the parameters and logging the AFRs then through the WB.

I checked somethng else last night and was wondering why does the injector pulse width change when you switch from closed loop to open loop, i did this at idle last night O2 Strim was 1%, 14.7 afr on the plx, switched to Open loop, nothing else and the afrs went to 13.0. the difference between 14.7 and 13 is a lot more than the 1% trim. Is it just a Honda ECU characteristic or is there something else within the calibration file that effects the closed loop open loop running, reason i ask is a prefer to run always in open loop when drag racing as so there is no danger of any fuel trims, especially seeing im now using rather large shots of nitrous

I am very happy with my Hondata but just have a few questions to help understand better.

Cheers
WEST

[Spunkster]

You should be able to tune in closed loop by looking athteh short term trim. When you get it to 0 you have the right settings. However this will vary depnding on the target voltage you have set as well as the voltage offset you need to make your wideband read the same as Smanager.