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Discussion Starter · #1 ·
Hi all

James from the land down under - Australia here, I've got an Australian 2014 RG Colorado manual with the 2.8Lt Duramax, tuned for towing with max boost/MAP of 300kPa (up from 258kPa max here looking at a stock file)

I'm having a strange lack of power when going to higher altitudes over 500m (1500ft) which first occurred over 2.5 months ago. At first I thought I have a boost leak and have had 2 mechanics look at the car extensively, but car is fine back at sea level and has never logged any trouble codes.

Speaking with the tuner who did the remap, they are adamant it is not related to the tune, but did mention something interesting, that they don't touch the med/high altitude boost maps.

I'm looking for a 2nd opinion - when others are tuning a Colorado / Duraxmax or other diesel with an E98 ECU, do you change the 'Desired Boost, Med Altitude' map as well as the low altitude base map?

Thanks in advance
James
 

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Might gain more traction in the EFI live forum, but i would say unless you have extensive mods to the truck, your stock altitude maps should work still OK on that truck. You tuner may have made slight adjustments to get more out of it and neglected to impart that into your higher altitude tables so, you may be down on power but should perform closer to stock i'd think. He gave you a 16% boost (from 258 to 300kPa) so you could try that in your med/high tables and see if you get your power back. I've never worked on the 2.8 but, is there also fueling tables for med/high as well? My LMM does. So you'd adjust up your fuel and boost (they work in conjunction of course).
 

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Discussion Starter · #3 ·
Follow up

I've downloaded a demo of EFI Live myself and some stock tune files for Colorado's as short of replacing the turbo, I don't think it is a mechanical issue as car still going strong at sea level for 2.5 months and towing 2.6 tonnes for lots of that...

The tuner couldn't tell me at what altitude the ECU will switch from the low to medium altitude boost map - not sure if anybody here knows?

My assumption for this change from low to medium altitude boost map by the ECU is from the table in Boost Control called 'Maximum Allowed Boost' as below;

Colorfulness Rectangle Operating system Slope Computer


Looking at this stock table, the max boost by rpm & barometric pressure is the same for 96-102kPa range, and then also for 66 to 93kPa range. My assumption is these may relate to the 'Low Altitude' and 'Med Altitude' settings for the ECU? e.g. below 96kPa barometric pressure, the ECU goes into 'Med Altitude' mode/mapping - which in my case would drop the car from a tuned low altitude map back to stock med altitude map.

There is also a big drop off in max allowed boost when the Barometric reading is under 96kPa (approx ~500m altitude which is were I see my issue starting when going up hill) - at lower revs under 2400rpm, but over the 2400 rpm range it is almost no difference so performance would/should pick back up (in my case it doesn't seem to)

I am also wondering when others tune a Colorado / E98 ECU car, do you normally scale up this Max Allowed Boost table across all Barometric readings in the scale range from 63 to 102kPa? I'm wondering if that has been done in my tune or maybe it's only the sea level 100-102kPa max boostwhich has been adjusted up which might further contribute ...

If my assumption from above is correct that the max allowed boost ranges indicate that 'Medium Altitude' kicks in at under 95-96kPa barometric pressure, then maybe that is what is happening as it really does seem the lack of performance kicks in around 500m and boost maxes to a 240kPa on my Ultragauge vs. 300kPa normally. The car is 'flat' and won't accelerate up a slight incline in 4th gear, just holds speed...

Looking at the stock map of Desired Boost Low vs Med Altitude, it does look like similar Boost levels are targeted at Med Altitude, just higher in the rev range (say 2400rpm vs 1800rpm for 250kPa at max fuel) ... so I assume this 'Med Altitude' map can be scaled up safely also without turbo overspeed issues?

Colorfulness Rectangle Slope Font Screenshot

Colorfulness Computer Rectangle Font Slope


In terms of a mechanical issue, I've done a lot of trouble shooting to date with 2 mechanics thinking it was a split intake hose/pipe/intercooler crack etc. - smoke test for leaks at 13 psi fine, cleaned MAF/MAP, new air filter, sensor relearn, reset ECU, and new tried a new MAP sensor, but no improvement. Short of trying a new turbo though, I'm not sure there is much else to try mechanically so I'm wondering if it is maybe the tune.

Unfortunately for me, the tuner doesn't want to talk about it anymore and is telling me to flash car back to standard and get it retuned by somebody else. So looking for a 2nd opinion from somebody with tuning experience on this engine/ECU if this could be the cause, or just focus on mechanical

Thanks in advance
James
 

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Discussion Starter · #4 ·
Might gain more traction in the EFI live forum, but i would say unless you have extensive mods to the truck, your stock altitude maps should work still OK on that truck. You tuner may have made slight adjustments to get more out of it and neglected to impart that into your higher altitude tables so, you may be down on power but should perform closer to stock i'd think. He gave you a 16% boost (from 258 to 300kPa) so you could try that in your med/high tables and see if you get your power back. I've never worked on the 2.8 but, is there also fueling tables for med/high as well? My LMM does. So you'd adjust up your fuel and boost (they work in conjunction of course).
Thanks Stroked06Goat, yeh hasn't gained much traction on the EFI Liveforum. This one seems a lot more active so thought I'd try over here

I'm not a tuner, don't have the hardware and not going to try to tune it myself, just looking for a 2nd opinion if this is worth trying or not.

I agree the car should theoretically go back to stock, I never drove my car at these altitudes before the tune so don't know what it was like without the tune, but I don't think it could be that bad - GM wouldn't have sold any Colorado's! and with the caravan on the back horrible and unsafe - at 500m we were 2nd gear 2750rpm and just holding like 30kph, could not accelerate up a slight incline... so not sure if the ECU at altitude is now ending up in some confused state with stock desired boost tables but maybe another aspect tuned up
 

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There IS a guy over at the HPTuners forum that is a big Colorado guy. He's super smart when it comes to tuning those. Go search some of his posts on his babymax might give you some insight?
 
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