SERT map & exhaust change?

[HD_04Ultra]

I have a good map for my current build.

'04 Ultra, 103", TR-625s, 10.2:1 c/r, street ported heads and 53mm TB.

I want to change exhaust only.
Current set-up is stock head pipes with Samson Rolled Oval slip-ons
Want to change to a 2-into-1 set-up, either D&D Fat Cat or Supertrapp Supermeg.

If the only thing I change is exhaust set-up will I need a whole new map built?

If not, how difficult is it to correct the current map for an exhaust change?

Thanks in advance,

"04_Ultra

[FLTRI]

I have a good map for my current build.

'04 Ultra, 103", TR-625s, 10.2:1 c/r, street ported heads and 53mm TB.

I want to change exhaust only.
Current set-up is stock head pipes with Samson Rolled Oval slip-ons
Want to change to a 2-into-1 set-up, either D&D Fat Cat or Supertrapp Supermeg.

If the only thing I change is exhaust set-up will I need a whole new map built?
If not, how difficult is it to correct the current map for an exhaust change?

Thanks in advance,

"04_Ultra

Easy answer: Yes. Anytime you change the air flow through the engine the EFI needs to be recalibrated to compensate for the changes created by the difference between designs, especially when changing from 1 type of exhaust system to another.
HTH,
Bob

[HD_04Ultra]

Bob,

So basically, the current map does no good at all, not even as a starting point?

I was hoping that the Spark advance table, and certain others could remain intact and that some sort of off-set could be applied to say the VE tables and that might be good or at least good enough.

I must not be thinking right if I understand what you're saying.

'04 Ultra

[FLTRI]

Bob,

So basically, the current map does no good at all, not even as a starting point?

I was hoping that the Spark advance table, and certain others could remain intact and that some sort of off-set could be applied to say the VE tables and that might be good or at least good enough.

I must not be thinking right if I understand what you're saying.

'04 Ultra

The existing map is good for a starting point.
The timing should not have to be changed for an exhaust change.
Since airflow through the powertrain from A/C to tailpipe is subject to change anytime a component along the way is altered, the fuel demand also changes. For this reason there is no "off-set" that can be added to the calibration/mapping without actually measuring the the engine's fuel demand with O2 sensors and making changes based on reading what the engine is doing.

As an example: Today a customer I had tuned some 6 months ago came in for me to evaluate the tune after he changed from a SEAC to the new Heavy Breather AC. He said it changed the way the engine ran. He also told me he replaced the SEAC and the engine ran fine.
As hard as it was for me to believe I told him it should not have made a big change. I was wrong. It changed the air flow enough to need a 80% re-tune. Some places it had gone lean and some places it was rich. After I was done the engine repeated the same power numbers from the original tune and the owner said felt like it was back running the same as with the SEAC.

Another example of why recalibrating/remapping EFI is necessary keep you and your engine happy.
Bob Lobenberg

[Steve Cole]

Hey we share every calibration we have with our products.

[WVULTRA]

Steve:

I think your post above was meant for this thread:

http://harleytechtalk.net/htt/index.php?topic=11841.0

[HD_04Ultra]

Bob and Steve,

Admittedly I am uneducated on the use of the SERT as a tuning device.  From my uneducated and overly simplistic point of view an engine is really nothing more than a glorified air-pump.  The more efficient the engine is at flowing air through the system the more power it will make (overly-simplified I realize).

If, having had the mechanical variables adjusted, tuned for maximum performance, and verified on a chassis dyno with o2 sensor calibrating the AFR at each region of operation, the only change made is the exhaust; how can the exhaust change modify the exhaust-to-intake ratio of the heads, the cfm of flow at 28" h20 of the heads, the timing events of the cam, the timing advance tables (front and rear) etc?  I can see how changing the exhaust would change the volumetric effeciency abilities of the "air pump" but if all else remains exactly the same (ceterus paribus) shouldnt that change be linear in its affect and therefore wouldn't incrementing the VE tables to account for this supposed increase in VE result in a good (or reasonably good) map?

As I said, I am admittedly uneducated on tuning so I am looking for an education and reasons why (and how) an exhaust change would affect each of the other tables in the map; other than VE which is exactly what the exhaust change is intended to accomplish.

Educate me please,

04_Ultra

[05FLHTC]

Nothing is FREE with EFI!

But then I tried to tell you that once already

[FLTRI]

Bob and Steve,

Admittedly I am uneducated on the use of the SERT as a tuning device.  From my uneducated and overly simplistic point of view an engine is really nothing more than a glorified air-pump.  The more efficient the engine is at flowing air through the system the more power it will make (overly-simplified I realize).

If, having had the mechanical variables adjusted, tuned for maximum performance, and verified on a chassis dyno with o2 sensor calibrating the AFR at each region of operation, the only change made is the exhaust; how can the exhaust change modify the exhaust-to-intake ratio of the heads, the cfm of flow at 28" h20 of the heads, the timing events of the cam, the timing advance tables (front and rear) etc?  I can see how changing the exhaust would change the volumetric efficiency abilities of the "air pump" but if all else remains exactly the same (ceterus paribus) shouldnt that change be linear in its affect and therefore wouldn't incrementing the VE tables to account for this supposed increase in VE result in a good (or reasonably good) map?

As I said, I am admittedly uneducated on tuning so I am looking for an education and reasons why (and how) an exhaust change would affect each of the other tables in the map; other than VE which is exactly what the exhaust change is intended to accomplish.

Educate me please,

04_Ultra

It's not about individual component specifications or measurements. It's how all the individual components work together from the time the air enters the air filter through the end of the tailpipe. Anything in between can be responsible for success or failure for the entire system's performance.

There must be compromise in individual component design or we would have 1 cam design, 1 combustion chamber design, 1 exhaust system design, etc, etc. Pretty much everything in IC engine design includes compromise.

For the above reason and known variables of component mfg tolerances, including injector output quantity, individual cylinder tuning of each TP/rpm is required anytime components have been changed that affect fuel delivery and/or airflow through the engine.

Your last sentence: "....other than VE which is exactly what the exhaust change is intended to accomplish."
You are correct which is why recalibrating the VE tables (fuel) is necessary. Exhaust changes do not necessarily make linear changes to actual VE, especially when changing the type (2into2 vs 2into1 vs slipons w/equalizer, etc) of exhaust.

Hope this helps,
Bob

[HD_04Ultra]

Bob,

So I'm guessing with a known good base map as a "starting point" the dyno time would be greatly reduced since the spark advance front and rear, idle rpm, and tuning constants could all be left alone (and maybe the Air Fuel Ratio).  The tuner would have to concentrate on the VE front and rear cylinder (seems that whatever non-linear corrections were made to the front cylinder "might" be an appropriate starting point for the rear cylinder?).  Also, maybe the warmup enrichment, cranking fuel, Idle Air Control Warmup Steps, Accel Enrichment and Decel Enleanment would require some minor adjustments, Right?  The biggest, most difficult, most important, and time consuming of these I presume is the VE front and rear cylinders.

Maybe not as simple as an offset or a given amount of increment but still having a known good map for a particular build should result in reduced tuning effort and dyno time to achieve superior results since at least the spark advance tables could be left "as-is".  I presume the the spark advance front and rear are likely the second most difficult and time consuming parts of a good tune (just guessing).

I am trying to learn something here so tell me like it is.

04_Ultra