mickeyd2005 Posted July 1, 2008 Share Posted July 1, 2008 Don't bother with a protune until you have all the mods you desire. The heat will increase boost treshold and can sightly reduce boost pressure. However your boost isn't low for stage 1, remeber you are at a higher elevation (14.075 Atmo Pres) therefore the ecu will lower your boost. At your current peak boost (14.51) at sea level this is around 15.15psi. That's true in regards to the physical aspects of the compressor. However, the ecu does not correct the target boost for atmospheric pressure based upon pressure ratio. It corrects MAP target based upon a percentage of MAP target. I don't have the numbers with me, but IIRC between 14.29 psi to 14.7 psi the correction is zero for the 05-06 LGT. At 14.1 psi, the correction is about 1.2% of MAP target. Link to comment Share on other sites More sharing options...
mickeyd2005 Posted July 1, 2008 Share Posted July 1, 2008 Here's a comparison to a 2005 stage 1 5MT. The temperature was very high but the atmospheric pressure is 14.7 psi. Even given the higher atmospheric pressure, the timing is just incredibly low. In fact, usually at higher altitude, the timing is higher due to the lower manifold pressure. The dip in timing on jblaze's tune between 4500 and 5500 rpm appears to be intentional and not knock. http://i141.photobucket.com/albums/r69/mickeyd2005/untitled-29.jpg Link to comment Share on other sites More sharing options...
Infamous1 Posted July 1, 2008 Share Posted July 1, 2008 However, the ecu does not correct the target boost for atmospheric pressure based upon pressure ratio. It corrects MAP target based upon a percentage of MAP target. I don't have the numbers with me, but IIRC between 14.29 psi to 14.7 psi the correction is zero for the 05-06 LGT. At 14.1 psi, the correction is about 1.2% of MAP target. Yes I know it is a correction base upon MAP numbers. However I am usually around 14.3-4 atmospheric pressure and there is definately a correction. My understanding is that anything in between cells it will slope +/- to the next cell. So anything under 14.7 will have a correction to some extent. Link to comment Share on other sites More sharing options...
jblaze7469 Posted July 1, 2008 Author Share Posted July 1, 2008 now i see what you mean by low timing Link to comment Share on other sites More sharing options...
mickeyd2005 Posted July 1, 2008 Share Posted July 1, 2008 Yes I know it is a correction base upon MAP numbers. However I am usually around 14.3-4 atmospheric pressure and there is definately a correction. My understanding is that anything in between cells it will slope +/- to the next cell. So anything under 14.7 will have a correction to some extent. If you have access to romraider, you can pull up the atm slope and atm offset. For some reason, I have a spreadsheet that says 0.06234 is the slope and 0.1094 is the offset (those might be for a differet ecu. I can't remember why I have those default values). However, the multiplier is capped at 1.0, so anything between 14.29 and 14.7 has no effective adjustment. I'll check later tonight. Link to comment Share on other sites More sharing options...
Infamous1 Posted July 1, 2008 Share Posted July 1, 2008 If you have access to romraider, you can pull up the atm slope and atm offset. For some reason, I have a spreadsheet that says 0.06234 is the slope and 0.1094 is the offset (those might be for a differet ecu. I can't remember why I have those default values). However, the multiplier is capped at 1.0, so anything between 14.29 and 14.7 has no effective adjustment. I'll check later tonight. I will email you one of my logs later on tonight. Link to comment Share on other sites More sharing options...
Legend Posted July 1, 2008 Share Posted July 1, 2008 If you have access to romraider, you can pull up the atm slope and atm offset. For some reason, I have a spreadsheet that says 0.06234 is the slope and 0.1094 is the offset (those might be for a differet ecu. I can't remember why I have those default values). However, the multiplier is capped at 1.0, so anything between 14.29 and 14.7 has no effective adjustment. I'll check later tonight. Curious about this too. My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
Infamous1 Posted July 2, 2008 Share Posted July 2, 2008 If you have access to romraider, you can pull up the atm slope and atm offset. For some reason, I have a spreadsheet that says 0.06234 is the slope and 0.1094 is the offset (those might be for a differet ecu. I can't remember why I have those default values). The slope is 0.05208 and the offset is 0.2500... Link to comment Share on other sites More sharing options...
mickeyd2005 Posted July 2, 2008 Share Posted July 2, 2008 The slope is 0.05208 and the offset is 0.2500... Yeah, I just got home and looked it up. The other values are for a different car. Answer is the same. Let's take a look at two examples: one, at 14.07 psi and one at 12.0 psi. In both cases, we'll assume the target boost is 18.0 psi at sealevel. The rom actually stores target MAP which is 32.7 psi, but romraider displays it as 18.0 psi at sealevel. EXAMPLE 1: Patm = 14.07 psi multiplier = 0.05208 offset = 0.25 Boost multiplier = 14.07 x 0.05208 + 0.25 = 0.982766 Target MAP At sealevel = 32.7 psi Corrected Target MAP = 32.7 x 0.982766 = 32.14 psi Corrected Target Boost relative to sealevel = 32.14 - 14.7 = 17.44 psi Corrected Target Boost relative to actual atmosphere = 32.14 - 14.07 = 18.07 psi EXAMPLE 2: Patm = 12.0 psi multiplier = 0.05208 offset = 0.25 Boost multiplier = 12.0 x 0.05208 + 0.25 = 0.87496 Target MAP At sealevel = 32.7 psi Corrected Target MAP = 32.7 x 0.87496 = 28.61 psi Corrected Target Boost relative to sealevel = 28.61 - 14.7 = 13.91 psi Corrected Target Boost relative to actual atmosphere = 28.61 - 12.0 = 16.61 psi Link to comment Share on other sites More sharing options...
jblaze7469 Posted July 2, 2008 Author Share Posted July 2, 2008 yall are getting into some heavy stuff here, i dig it!! Link to comment Share on other sites More sharing options...
Infamous1 Posted July 2, 2008 Share Posted July 2, 2008 Yeah, I just got home and looked it up. The other values are for a different car. Answer is the same. Let's take a look at two examples: one, at 14.07 psi and one at 12.0 psi. In both cases, we'll assume the target boost is 18.0 psi at sealevel. The rom actually stores target MAP which is 32.7 psi, but romraider displays it as 18.0 psi at sealevel. EXAMPLE 1: Patm = 14.07 psi multiplier = 0.05208 offset = 0.25 Boost multiplier = 14.07 x 0.05208 + 0.25 = 0.982766 Target MAP At sealevel = 32.7 psi Corrected Target MAP = 32.7 x 0.982766 = 32.14 psi Corrected Target Boost relative to sealevel = 32.14 - 14.7 = 17.44 psi Corrected Target Boost relative to actual atmosphere = 32.14 - 14.07 = 18.07 psi EXAMPLE 2: Patm = 12.0 psi multiplier = 0.05208 offset = 0.25 Boost multiplier = 12.0 x 0.05208 + 0.25 = 0.87496 Target MAP At sealevel = 32.7 psi Corrected Target MAP = 32.7 x 0.87496 = 28.61 psi Corrected Target Boost relative to sealevel = 28.61 - 14.7 = 13.91 psi Corrected Target Boost relative to actual atmosphere = 28.61 - 12.0 = 16.61 psi Gotcha, thanks for the math I was confusing myself trying to figure it out Now as for the correction being 0 from 14.4-14.7, I still cannot figure out why and I could swear I have log a Patm= 14.4+. I have seen target boost at 18.33 with the rom calling for 18.47. I know you stated to look at the TD proportional yet I still am . I have that log as well but don't know the atmosperic pressure for it, Wikipedia say 361ft elevation for the city where I took the log Link to comment Share on other sites More sharing options...
Legend Posted July 2, 2008 Share Posted July 2, 2008 EXAMPLE 2: Patm = 12.0 psi multiplier = 0.05208 offset = 0.25 Boost multiplier = 12.0 x 0.05208 + 0.25 = 0.87496 Target MAP At sealevel = 32.7 psi Corrected Target MAP = 32.7 x 0.87496 = 28.61 psi Corrected Target Boost relative to sealevel = 28.61 - 14.7 = 13.91 psi Corrected Target Boost relative to actual atmosphere = 28.61 - 12.0 = 16.61 psi Great - thanks. And thanks for picking 12.0atm for example 2 for us Denver guys. As I've tuned boost I plot my boost curves with the target boost. I've found it frustrating to see TD indicating overboost when when actual boost is still a full 1-1.5psi less than target.... never knowing exactly where the ECU thinks the real target is. Now instead of plotting target boost (from the RR table), I'll plot corrected target boost. My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
Legend Posted July 2, 2008 Share Posted July 2, 2008 I must be doing something wrong because for low target boost values I am getting higher corrected target boost relative to actual atmosphere. Assume a lower value at a lower rpm on the boost table... say 2.0 Patm = 12.0 psi multiplier = 0.05208 offset = 0.25 Boost multiplier = 12.0 x 0.05208 + 0.25 = 0.87496 Target MAP At sealevel = 16.7 psi Corrected Target MAP = 16.7 x 0.87496 = 14.61 psi Corrected Target Boost relative to sealevel = 14.61 - 14.7 = -0.09 psi Corrected Target Boost relative to actual atmosphere = 14.61 - 12.0 = 2.61 psi Running a target of 2.0 I end up with a higher corrected target at altitude. What gives? My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
LittleBlueGT Posted July 2, 2008 Share Posted July 2, 2008 I love having a tuning forum. Looks like your math is right Legend. I think the ECU's simplistic formula doesn't work too well at lower pressures. Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
mickeyd2005 Posted July 2, 2008 Share Posted July 2, 2008 I love having a tuning forum. Looks like your math is right Legend. I think the ECU's simplistic formula doesn't work too well at lower pressures. Yeah. It looks odd, but I believe that is the equation the ecu uses. If I made a mistake, let me know. Legend log your TD proportional and I think you'll see that it lines up. If you recall, I used to calculate boost error off the TD proportional. Link to comment Share on other sites More sharing options...
mickeyd2005 Posted July 2, 2008 Share Posted July 2, 2008 Gotcha, thanks for the math I was confusing myself trying to figure it out Now as for the correction being 0 from 14.4-14.7, I still cannot figure out why and I could swear I have log a Patm= 14.4+. I have seen target boost at 18.33 with the rom calling for 18.47. I know you stated to look at the TD proportional yet I still am . I have that log as well but don't know the atmosperic pressure for it, Wikipedia say 361ft elevation for the city where I took the log The LOGGED target boost in romraider assumes sea level. So, if you are logging target boost then you will need to adjust it. Link to comment Share on other sites More sharing options...
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