Richer AFR driving turbo's harder?!?

[Warsteiner05]

Without any changes to any other parameters except for main VE, adding fuel to tune twin turbo jet boat @ WOT. 5.3 with Twin S366 turbos and 80lb DEKAs

base table: 12.3 AFR @WOT: Boost controller closed was right at 10psi. I added three turns to maintain 15psi

added 10% fuel to base table: 11.7 AFR @ WOT: one turn back to maintain 15psi. (2 turns from closed)

added 15% fuel to base table: 10.4 AFR @ WOT: boost controller closed, 16-17 psi (This is where it pulled the hardest, by seat of the pants dyno)

(Just for shits and giggles to see what would happen) added 18% fuel to base table: 10.2 AFR @ WOT: 17-18 psi with boost controller closed. (Pulled pretty hard, but not like 10.4 afr run)

Why in the heck is it driving the chargers HARDER at a richer AFR? So rich that its starting to black smoke. I re-calibrated my innovate wideband prior to making these runs.

Tune attached is the 10.4 afr run.

[5FDP]

Are you sure it's not because of the timing you are running?

10 psi of boost on 18 degrees is going to be nothing like 17psi on 18 degrees. The more timing is going to make more power and wanted more fuel because of the boost.

[Warsteiner05]

Are you sure it's not because of the timing you are running?

10 psi of boost on 18 degrees is going to be nothing like 17psi on 18 degrees. The more timing is going to make more power and wanted more fuel because of the boost.

I think I should have re-worded my question. I was tuning WOT afr after some other changes I made (intake mani, 92mm TB) and discovered the richer I was going, the more I was having to turn down the boost controller to maintain a desired boost level (15 psi in this case).
I can understand a more powerful burn from 12.3 to 11.7, but to gain power from 11.7 to 10.4 afr and drive the turbos so hard that I had to set the boost controller to minimum, and again gain boost going from 10.4 to 10.2 (but no power increase). It was just odd to me!

What are your thoughts on timing? I'm still making some changes here, mainly tuning for WOT to ensure the engine stays together. I do plan on smoothing the chart once I get WOT dialed in, but say going from 93 octane to 105 octane, what is safe maximum timing for say 15-18 psi? Also, is there a boost retard table in a 3 bar os? I'm not getting any detonation running 18 degrees on 93 oct non-ethanol. I've even sent my camera down the spark plug hole and had a look around. Air/Water intercooler with 75 degree lake water helps im sure.

[blindsquirrel]

Congrats, you just rediscovered one of the main components of how jet engines work!

[Warsteiner05]

Congrats, you just rediscovered one of the main components of how jet engines work!

Coming from diesel-land, you would think I would have just said OK thats how this works, but knowing that that 11.76 afr is Rich best torque, and 12.2 is Mean best torque, it surprised me that going richer than 11.7 provided a significant amount of drive pressure increase to the turbos, enough that I had to adjust the boost controller a good bit to compensate, in order to maintain 15psi, until I lost control of the wastegates via the boost controller and they simply couldn't bypass enough drive pressure to maintain desired boost.

Initially with 18* timing and an AFR of 12.3, the wastegates could bypass enough drive pressure to get as low as 10psi boost pressure. Going richer to 11.3-11.7 made a little sense, but how did adding so much fuel that its fat and pig rich, raise the drive pressure even more?!? Thats where my confusion is.

[village_idiot]

I was going to ask how you ended up at a 10.4 AFR when your PE is commanding 11.7, but then I realized you're running in open loop and your open loop eq ratio is still set to 1.13 above 80kpa so I found it. Works the same I guess, just more tables to look at, and more math to do

Sounds like a neat boat. Post some pics one day, I miss my jet boating days

[Warsteiner05]

I was going to ask how you ended up at a 10.4 AFR when your PE is commanding 11.7, but then I realized you're running in open loop and your open loop eq ratio is still set to 1.13 above 80kpa so I found it. Works the same I guess, just more tables to look at, and more math to do

Sounds like a neat boat. Post some pics one day, I miss my jet boating days

I'm not running narrow-band sensors, so the ecm has to run open loop. I'm simply running widebands and monitoring them myself and adjusting the VE table as necessary to obtain my desired results. If its not the correct way then i'm open to suggestions and opinions, I'm still learning my way around the Hptuners software.

[village_idiot]

They both achieve the same results, but where as your PE table has 1.250 in it (14.68 / 1.250 = 11.74 AFR commanded in PE), and you have another adder in play here that most people will set to 1.00 to just simplify things

Engine > Fuel > Open Loop/Base > EQ Ratio (ECM 12430)... If you look, yours is set to 1.13 above 80kpa in operating temp, so the way your fueling math breaks down right now is
14.68 stoich / 1.250 PE = 11.74
then
11.74 / 1.13 open loop eq = 10.39

Personally, to eliminate having one more adder, I would set the OL EQ table to 1.00 straight across the board and continue tuning on the VE to achieve whatever the commanded PE is.... If you do this though, just know you will be pulling 13% fueling out of your current situation and be aiming for a true 11.74 target. Either way works, but one is just less tables and less back figuring

[village_idiot]

You can also use Boost Enrichment for a final target AFR on yours

Engine > Fuel > Power Enrich > Boost Enrichment

Yours is set to 1.00 (not active) but if you wanted to add a layer that way, set the kpa threshold to whatever you want it to activate at (currently 110kpa) and set it just like you did your standard PE table. If you wanted PE to be 11.80 and BE to be 10.80 then you could keep your PE at 1.250 and set the BE to something like 1.360 to aim for roughly an 11.80 while not in boost, or a 10.80 above 110kpa

Just throwing another scenario at you for you to look at. They all WORK, it's just all different routes to the same place. With BE, you'll see in the table, you can change your target AFR every 10kpa from 105-315 if you wanted to

[Warsteiner05]

You can also use Boost Enrichment for a final target AFR on yours

Engine > Fuel > Power Enrich > Boost Enrichment

Yours is set to 1.00 (not active) but if you wanted to add a layer that way, set the kpa threshold to whatever you want it to activate at (currently 110kpa) and set it just like you did your standard PE table. If you wanted PE to be 11.80 and BE to be 10.80 then you could keep your PE at 1.250 and set the BE to something like 1.360 to aim for roughly an 11.80 while not in boost, or a 10.80 above 110kpa

Just throwing another scenario at you for you to look at. They all WORK, it's just all different routes to the same place. With BE, you'll see in the table, you can change your target AFR every 10kpa from 105-315 if you wanted to

Thank you so much!

[blindsquirrel]

Add some spark timing, if it's safe to do so, and I bet it makes boost go back down (some, at least). It's excess fuel plus spark low enough to put fire out the exhaust instead of normal-combustion exhaust gases that drives the turbines harder.

[Warsteiner05]

Add some spark timing, if it's safe to do so, and I bet it makes boost go back down (some, at least). It's excess fuel plus spark low enough to put fire out the exhaust instead of normal-combustion exhaust gases that drives the turbines harder.

That makes sense! But I'm a little wary of adding any more timing, as I'm running 18* now on 93 octane. I found a supplier for some AVGas 102 octane, I'm gonna run that this weekend and play with some timing and fuel tables. I am also going to do as village_idiot said and set the open loop eq ratio table to 1.00 across the board, and add the 13% back in on the VE to compensate. Which is correct as it should eliminate some extra legwork. After I get the afr close to where I want, I will atttempt to smooth the tables out and fine tune my part throttle fuel/spark. I have it a little rich to be safe, but on a part throttle run around 2800-3200rpm, the plugs start to foul out and I have to mash on it to clear it up.

On a boat its a little tough, logging, setting the laptop where it will stay put and not get wet during a run! Nothing stays put in a 700+hp jet drive boat! I can barely hold myself in the boat! I have a new all forged engine built that I plan on pushing the limits of a 3 bar map with, but i'm trying to learn on the current engine setup. Shooting for around 1200-1300+hp on the new setup.

THANK YOU ALL for your input!

[blindsquirrel]

OK, then if you just want to experiment (not trying to solve a specific problem), do this - go back to the leaner mix you had before, ensure your boost is back down to it's baseline, and then pull 5 or 6 degrees of timing out of it.

This happens a lot, somebody pulls some timing 'just to be safe', and ends up getting more boost they weren't expecting.

[Warsteiner05]

But which is safer? Which makes the most efficient power? Less timing and more boost? or More timing and less boost?

[blindsquirrel]

You'd really need to monitor EGTs and backpressure:boost ratio numbers to know more about what it's really doing and whether it's safe long-term. If what you're seeing is from fuel burning in the pipes it'll be really hard on the turbines. Might make good power that way but at the cost of reliability. Boats are a special case since aside from idle, they never really do any no-load running so what's 'safe' in a car doesn't necessarily apply.