Tweecer starting point for longtubes?

kbconv

kbconv

Mama's Boy
I just put Kooks 1 3/4" longtubes on my stock '94 (C3P2) and ran a free flowing 2 1/2" mandrel cat DI/DO exhaust out the side. Previous owner added a 4" sorta-CAI intake with a K&N Filter.


I'm going to hook up a Tweecer RT and Innovate wideband this weekend to see where my A/F is after I finish with motor mounts. I've had the Tweecer for years but haven't ever tuned with it, Lightning support was lacking when I got it for a Mustang. I've read the quick tips here quickly but have been sorta brain dead from a complete front end rebuild and other projects also.

Any quick tips on what I may want to change for the longtubes or beginning EEC mods? The stock 02 sensor is now located at the end of the collector, maybe 38" from the header flange. I'll get some A/F readings in a day or two.

Thanks
 
Let it run like a week with the long tubes before making g any solid changes. Just monitor the a/f ratio and driveability. Chances are you may not need much adjustment for headers.... I didnt.
 
kbconv said:
I've had the Tweecer for years but haven't ever tuned with it, Lightning support was lacking when I got it for a Mustang.
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Not sure when you got it but I (and tons of others) ran a EEC tuner before the tweecer came out then upgraded to the tweecer when it came out. I tuned my black 94 with the tweecer back in 2001.
 
Hello, in the STKR software (caledit) there is a table called "Fuel Closed Loop Hego Bias". It's constants -XY values are Manifold Pressure and RPM. The resultant value are the time in miliseconds from fuel pulse calculation until it should register at the O2.sensor. If you develop some drivability issues due to the distal location of the O2 sensor you can raise the resultant values for effect. Try adding no more than 10% to the table values as a starting point across the entire table.
Also make sure you are running the new software updates available from Tweecer.com. RT132 is the latest and greatest. Also note the C3P2, C3P3 an ICY1 are all using the ICY1 strategy now not the LHBLO as previously used.
 
slow94 said:
Let it run like a week with the long tubes before making g any solid changes. Just monitor the a/f ratio and driveability. Chances are you may not need much adjustment for headers.... I didnt.
Click to expand...

This. My truck isn't an L, but my experience was the same. Truck ran like crap for about 150 miles and was then fine.
 
sstock said:
Hello, in the STKR software (caledit) there is a table called "Fuel Closed Loop Hego Bias". It's constants -XY values are Manifold Pressure and RPM. The resultant value are the time in miliseconds from fuel pulse calculation until it should register at the O2.sensor. If you develop some drivability issues due to the distal location of the O2 sensor you can raise the resultant values for effect. Try adding no more than 10% to the table values as a starting point across the entire table.
Also make sure you are running the new software updates available from Tweecer.com. RT132 is the latest and greatest. Also note the C3P2, C3P3 an ICY1 are all using the ICY1 strategy now not the LHBLO as previously used.
Click to expand...

Pay attention here kbconz. sstock has tuned MANY trucks across the nation and is known by many as "the Wizard" with TwEECer tuning of these trucks.

Scott
 
Yup, agree Skritch. I've been lurking here for years reading some of the great info. Had some health issues and finally getting back on my feet to work my plans hopefully.

I got one of the first RT's I think, when I installed on my Mustang I found an issue and documented with Mike Glover, had to send it back to get new firmware or a FPGA replaced, he had to redo all of that run...then life happened and I put it on the shelf till now.
 
sstock said:
Hello, in the STKR software (caledit) there is a table called "Fuel Closed Loop Hego Bias". It's constants -XY values are Manifold Pressure and RPM. The resultant value are the time in miliseconds from fuel pulse calculation until it should register at the O2.sensor. If you develop some drivability issues due to the distal location of the O2 sensor you can raise the resultant values for effect. Try adding no more than 10% to the table values as a starting point across the entire table.
Also make sure you are running the new software updates available from Tweecer.com. RT132 is the latest and greatest. Also note the C3P2, C3P3 an ICY1 are all using the ICY1 strategy now not the LHBLO as previously used.
Click to expand...

This is incorrect.

The correct table to edit for header length is not BIAS, but DELAY. In OE terms (and what you'll see in other software it is referred to as transport delay. You can increase this as mentioned, but remember that you're shooting from the hip. You also likely do not have the ability to increase your heater duty cycle, so regardless of what you do there, you're going to see poor (diminished) sensor performance at low RPM due to lack of heat in the sensor. Depending on the age of your software and the definitions used you may find this named pulse delay or something along those lines. Again, it translates into transport delay.

The logic of the HEGO bias table, which is actually closed loop bias in OE terminology is in place for changing the bias from stoich for emissions purposes. This table will have positives and negatives. Positive numbers are leaner. Negative numbers are richer. It shouldn't be messed with over longtubes in general practice. That's not what it's for. It's for changing your actual mixture.

You'll likely find that you have emissions equipment that may now be removed and should have the scalars adjusted accordingly.
 
When I messed with the transport delays it made my truck run awful. Leave it stock and see what it does. Bet your truck learns how to deal with it in a week. If it does need work I would follow Steves advice and not change it by much.
 
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