Down on boost, wondering why? w/ some dyno results and JB4 log

[Landboat G80]

Yesterday I went to the dyno to do some logs and get some results.

Intake, Exhaust, Fuel-It
432RWHP 499RWTQ on E30 MAP4
Can’t tell if this is substantially low or not, but seems like people these days are making 460AWHP with same mods.

Noticed that my peak boost barely touched 18.0 during the dyno and I’m used to seeing around 20.4, I did some digging into the logs and while the boost target for the JB4 was correct the ECU Boost is lower than it used to be.

The ECU hardly peaks at 12PSI now where it used to be around 14.4 PSI. (From looking at old logs) the weather is around 50F colder now, so I’m wondering if that has anything to do with it.

Was really hoping to be sitting at 450 considering RWD and mods, so I’m not sure if I’m underperforming or if this is normal? Either way it’s time for WMI.

Dyno in the log is at the tail end.

 

[G70LEbyAdoom]

The stock ECU WILL lower peak boost when certain temp conditions are met. that is most likely the case.

 

[oddball]

You really cannot compare numbers from different dynos. Even the same dyno from day-to-day will change.

Boost PSI also is just a wishy-washy number. The ECU cares about the air charge, and PSI is just part of calculating that. It'll drive the wastegate to get the air charge it wants. Colder air is denser, so a lower intake PSI will have the same amount of actual air in it.

 

[Landboat G80]

You really cannot compare numbers from different dynos. Even the same dyno from day-to-day will change.

Boost PSI also is just a wishy-washy number. The ECU cares about the air charge, and PSI is just part of calculating that. It'll drive the wastegate to get the air charge it wants. Colder air is denser, so a lower intake PSI will have the same amount of actual air in it.

That makes sense! I knew that the ECU would vary boost based on the weather, but I've always assumed that the lower the temperature the more boost you could make, hense the term "Boost Weather." However, based on what you've said that makes a lot of sense! So I don't want to increase the boost any using the EWG to meet the numbers I was used to seeing in hotter weather, as I could run into fuel crashing, right? I'm already pretty up there with fuel trims from what I understand, pulling around 40 at WOT, giving me very little room to keep adding fuel. (E30)

Thanks for all the knowledge you've been shedding on this noobs posts.

 

[Landboat G80]

Also another question for you @oddball should I be concerned with the way the Dyno is very choppy, or is that likely just accredited to the dyno itself? I've never seen that before.

 

[oddball]

That makes sense! I knew that the ECU would vary boost based on the weather, but I've always assumed that the lower the temperature the more boost you could make, hense the term "Boost Weather." However, based on what you've said that makes a lot of sense! So I don't want to increase the boost any using the EWG to meet the numbers I was used to seeing in hotter weather, as I could run into fuel crashing, right? I'm already pretty up there with fuel trims from what I understand, pulling around 40 at WOT, giving me very little room to keep adding fuel. (E30)

Thanks for all the knowledge you've been shedding on this noobs posts.

Cool weather is good performance weather - NA, turbo, supercharger, 2 cycle, diesel, whatever. Check out some of the Engine Masters episodes talking about turbos. Yeah, the fuel pumps become a limiting factor pretty quick. It can be easy to go too far then have a lean spike at WOT. That's when things go ker-sploooey.

Also another question for you @oddball should I be concerned with the way the Dyno is very choppy, or is that likely just accredited to the dyno itself? I've never seen that before.

You can ask the dyno operator to turn up the smoothing factor. That will make a nice smooth line that's also a total lie.
My machinist leaves smoothing turned completely off. The graphs look like dog shit, but that's what the machine is actually seeing.

Each dyno is different. The dyno operator develops a feeling for when things are working correctly and how to get the best(*) results.
In this case, best means "most correct".
You can change the correction factor, change the weather data, muck with all sorts of dials and options to get whatever output you want. Want a dyno graph that shows 1,000hp? Easy!

So, generally, you just have to trust the operator. And in the end, the only real use for a dyno is to see the effect of tuning changes on the same day.

For example, here's the output from three days on an engine dyno. I got good data on how different carbs reacted, and different ignition timing. Shockingly, 34 degrees total timing had the best average output! Almost every old v8 prefers 36deg.

 

[oddball]

welp, not letting me upload pictures, maybe later

 

[oddball]

*sigh* hospital wifi ain't great, and hacked verizon hotspot ain't much better.

 

[Oryan]

Do you have a dragy or plan on taking it to a track? I'm really curious about what a modded G80 can do. I've never actually seen a modded 3.3T G80 run anything.

 

[LibmanLive]

The stock ECU WILL lower peak boost when certain temp conditions are met. that is most likely the case.

In October 2022 my DynoJet was 521@ 5134rpm. In May 2023 I'm at 490@5107rpm. On the same day at a higher speed I reach 554 whp@140mph. It could just be the weather changes from cold to hot and also barometric pressures.

 

[Tommy G]

Do you have a dragy or plan on taking it to a track? I'm really curious about what a modded G80 can do. I've never actually seen a modded 3.3T G80 run anything.

I have a 2018 Genesis G80 sport AWD, got exhaust, secondary DPs, intakes I'm faster than a scat pack and the JB4 shows 0-60 in 3.9 I'm not sure how accurate this is but it's fast! Also this morning I raced a brand new Acura TLX type S 340 hp I believe he had intakes only. I'm in map4 E30 but in Eco 20mph roll he was frozen in time lol he couldn't hang.