tuning for 2 up riding in high elevation

i tune harley's and i just recently did one for a customer who is now experiencing issues. i tune in san jose california which is 82 feet above sea level. the customer just now informed me that he is riding 3,500 ft. above sea level on some mountain with a passenger and they are experiencing flat spots. I got the ve table damn near perfect. i am using powervision (reflash tuning) to tune the bike. any clue on what could be causing him to have issues ? apparently there is a big hesitation from 2100-2900 rpm's but only at high elevation with the passenger. i also asked him to try riding with out knock control on to see if it was pulling timing from a false knock (harley engines are loud and cause knock sensors to falsely go off alot) but that didnt help. wondering if i should turn off the narrow bands or the adaptive control. please help

Hi Adam,

Does the ECU you are working with have a barometric correction function?

Some ECUs will apply a correction based on the MAP sensor reading when the engine is not running. For example at sea level barometric pressure is around 101 kPa, at 3500ft this is going to be closer to 89 kPa. If the ECU isn't able to correct for this variance, it would cause all sorts of issues.

no it does not. it can pull spark based on head temp or air temp but has no barometric function. as far as the map sensor there is a map load normalization feature that allows you to change how the map sensor reads (such as for high overlap cams) but like i said no barometric feature. harleys that dont have stand alones, thundermax systems, or target tune systems only have narrow band sensors that are only used in cruising ranges of the ve table

Normally as you gain altitude (and have lower overall cylinder filling), the ignition timing can be advanced (just like with lower MAP readings the ignition is advanced). But if you tune for high-altitude, you often need to retard the ignition of the engine is going to be run at lower altitude.

If there were an easy way to add a few degrees of ignition timing, I would try that.

if i added a few degrees of ignition timing and the guy road back down to sea level wouldn't that run the risk of pinging ? or if the knock control is on then it would make it not have optimal power correct ?

Scott is correct. If there is no barometric comp, the VE tables will be incorrect at high altitudes...The good news is it's going rich instead of lean. I'm assuming the AFR will be down by 1-1.5 at 3500ft/89kpa depending on what the target AFR was at sea level. Maybe have the customer keep an eye on the spark plugs for fouling until he comes back down from the mountains. Hopefully, he is understanding of the situation.

TBH, I find it difficult to understand H-D not having an ambient pressure correction built in, as the owners could be riding from sea level to well over 10 000 feet.

I might suggest there being a function on/of the "map load normalization feature" part that would perform this correction?

I would also suggest checking with the H-D specific sites and/or forums as this must be a common issue?

I have no experience with HD/power vision, so I am just speculating...However, after briefly scrolling through the power vision owner's manual, it does utilize a map sensor and separate VE tables for the individual front/rear cylinders. So in theory, it should compensate for altitude change... (someone correct me if I am wrong here)

I did find there are A few enrichment multipliers that can be triggered by the rider's throttle input that could be the culprit at higher altitudes.

- Enrichment Multiplier: This will determine the total amount of fuel to add during rapid changes in acceleration. To "globally" increase the amount of fuel added during acceleration enrichment increase this value. To reduce the amount of fuel delivered decrease this value. Available in pro user level only

- PE Air Fuel Ratio (Lambda/Stoich) Power Enrichment mode is active at higher RPMs and when the throttle position is greater than 95 percent. The purpose of PE mode is to operate the engine at maximum torque AFR and spark values for a short time, then adjust to more conservative values to reduce engine temperature. Available in pro user level only

- Acceleration Enrichment Acceleration Enrichment mode can be triggered by a sudden change in throttle position or an increase in MAP pressure. To increase the fuel delivered, increase the values.

G.T. Eleven there is only 1 map sensor on harleys idk why it would say 2. the power enrichment is managed by time so i have already set that properly and the acceleration enrichment has alread been set. but i dont think those would have to do with why its hesitating between 2100-2900 rpm's. i usually dont need to touch those settings unless its a pretty high performance build. this is bike only has a cam, injectors, exhaust, intake manifold, and a air cleaner. typically its a pretty easy tune. wondering if its more of a timing issue. the map load normalization feature is more so to set the map reading where you want it. for instance if at idle the bike is reading 60 kpa but you want it to read between 30-40 kpa ideally you would use that table to adjust it. or if at higher rpm with the throttle wide open say 5500 rpm-6500 it drops back down to 90 kpa instead of 100 kpa you would use the map load normalization in order to make it read where you want it before you proceed with the tune. the map load normalization is not a constantly changing parameter such as a iat or 02 sensor reading if that makes sense

just got off the phone with dynojet. they said there was an issue with the firmware for the 2021-2022 harleys that put an incorrect value into the iac scaling table and the incorrect values into the minimum and maximum values for that table. they gave me the correct values to enter. im curious to see if this fixes the issue