Twin Scroll Turbo

[squaab99t]

Geez I felt pretty proud of myself for gluing some pieces of wood together this weekend

In order for the readings to be accurate for a force inducted engine the exhaust pressure reading needs to be obtained and factored in with the AEM Wideband arrangement.

This part confused me until I did some reading up on how o2 sensors get their reference oxygen and now I think I understand it a little better. I guess now I am still confused, just in a different way, but how is this not a bigger problem with all FI cars? Is it because factory ECU's usually ignore the narrowband o2 sensor when at WOT to get high boost levels? Is this more of an issue that mostly pops up when tuning with a wideband?

Gluing wood together in a ice cold garage is no easy task.
To be honest that was the first time I have formed tubing like that. Keeping in your mind's eye the shape and were you want to end up. And being careful you don't fold over and crimp the stuff in the process.

I too have been wondering what the need was to have a back pressure input on a force induction engine? Besides to sell you another $250 worth of hardware. We ran the big block n/a without this input, but again the absolute pressure did not change much, it any.
Did some surfing and found info on various forums on setting up engine dyno cells.
Seems that the Bosch or NTK WB sensors are affected by pressure deltas above and below standard atmospheric pressures. Graphically depicted in this screenshot. This is based upon the technical data on the Bosch sensor itself.

I have a feeling it has to do with the Perfect Gas Law. PV = nrT
Now this author used elevation as the variable to cause delta P. IMO (guess), Forced induction would be a bigger factor as the boost pressure simply does not get absorbed in the combustion process. Remember these sensors are in each primary prior to the turbo.
I think you are onto something with the OEMs and ignoring the AFR. It simply goes to the map and grabs a correct value per the predetermined map based upon the the engine development program. Most likely conservatively rich and listening for knock.

Next step is to wire in the AEM module and have it feed the analog inputs to the ECU. It will be interesting to see the amount of each runner is getting compared to it neighbors. I have a feeling cylinder 4 is getting totally robbed relative to the others.

[hutch]

I've only dealt with 3/8" copper, admittedly pretty soft, but yeah bending is a huge pain. Look at it the wrong way and it kinks up on you, so nice work!

I'll admit I spent more time than I should trying to reason it out with PV=nRT but couldn't think of any scenario where an increase in P and V didn't result in a proportional increase in moles of O2, even if T is increasing as well. Once I learned how O2 sensors actually created the voltage I realized it would be a problem, but then was further confused why it wasn't an issue on a magnitude greater than the errors on that chart. For example if you are running 1bar of boost why wouldn't that essentially show the O2 sensor you were incredibly lean since you had twice the O2 compared with the reference air.

My only thought was it is a big problem with a narrowband sensor, but like I said the ECU is ignoring the O2 sensor most times you are seeing that much pressure so it doesn't matter. I guess widebands are constructed a little differently, but I'll admit I'm still confused why its such a relatively small error % when you are dealing with doubling, or tripling the amount of oxygen...

Oh well, enough of my ramblings, awesome job as always!

[squaab99t]

I use this project car as a learning tool and figuring out why there is an affect would be good, I got other tasks to work on. Maybe another time, or I'll ask for the cliff notes when I visit AEM at SEMA this year.
Next task to mount the module in the engine compartment so it is secured, safe from heat and rotating objects.
Wires need to be close to the Lambda sensors and pressure sensor. I chose the fresh air cabin intake box. I have a catch can mounted to the A/C blanking plate, so I'll piggyback on to that.

Bent up some sheet with some stiffening flanges. Provisioned a hoop to clamp around the catch can. Added some controlled electrical current and filler rod.

[squaab99t]

A little bit more work this morning before house projects.
Worked on the wire design. Switched power, curcuit protection and relay for the heavy power. 20 amps to drive the 4 UEGO heaters and wideband module.
Love hate relationship with the electrical part of this. UGEO sensor look hot on the other hand. Lined up in pairs, looking with purpose versus a porcupine.

[squaab99t]

Completed the wire design and most all of the install. Everything is looking pretty tidy. I used the old ignition coil for the switched power, and the Saab relay fuse holder combos you would find on a convertable for the roof actuation. Bolted that to the LHS now that I have my battery on that side and terminal blocks. Works out well for the switched power and it is away from the heavy heat.

One last connector to wire up: 4 pins for the voltage outputs and one signal ground. The bundle of blue wires are the analog inputs to the ECU.

I created the translation tables to convert the 0-5v output to a lambda reading in the laptop. Should feed the datalog and user defined gauges.

[gmreider]

Dennis , The catch can and bracket caught my eye. Any photo showing where the plumbing goes to the motor? Looking for other examples of controlling the breather output.
All that wiring for the sensors has made be dizzy ! And then the theory.
Maybe I'll just go work on my 2 stroke?

[squaab99t]

Dennis , The catch can and bracket caught my eye. Any photo showing where the plumbing goes to the motor? Looking for other examples of controlling the breather output.
All that wiring for the sensors has made be dizzy ! And then the theory.
Maybe I'll just go work on my 2 stroke?

Catch can? Yes, that is more my cup of tea too.
Off the cam cover PCV nipple and into the horizontal inlet. Off the top of the catch can is an additional extension hose and a splice into the original hose leading to the inlet of the turbo compressor.

Home grown catch can. A blade baffle runs vertically, but stopping short about an inch from the bottom. This separates the two ports to promote capture. Stainless steel kitchen scouring pad added for filter material.
Drained it yesterday and it was mostly water and some cottage cheese.

[gmreider]

Thanks Dennis , I am using a small can with a breather on top to the surrounding air. It keeps the oil out of the intake stream and the intercooler, but still did not satisfy me. Once I started to make big power blow- by started to creep up on me. I guess my motors are a little loose. As the leak down numbers increased, We could get some excessive pressure and push some oil out the dip stick / fill pipe.

[squaab99t]

I ran it with a pleated filter off the top too. Made a mess of the engine compartment and did not seal the crank case like it does with a little vacuum like the stock arrangement.

[gmreider]

Thanks for your input. Its easy enough to make some changes and see if it works as you say. I'll just monitor the oil that winds up in the turbo intake and then the intercooler. I am assuming that you put a petcock or a drain plug at the bottom of the can? Just where did you locate the scouring pad, right at the intake of the car or across the bottom between the chamber?

[squaab99t]

Across the bottom and part way up the sides. If I recall 2 pads one on each side of the baffle.
It does have a petcock on the bottom. You can get a small cup under it and drain.

[squaab99t]

Back to the science project. Reminds me of a FB meme I saw. Picture of a microscope and the words " Science, it is better to figure stuff out than to make shit up."
Got her all wired up and tidy, so nothing would melt or turn into a weed wacker. Powered the module up, no fuse blows and the magical blue smoke stayed in their own boxes.
I did some garage laptop testing and user defined gauge setup. Got digital read out in lambda, needle on a dial and feeding the analog input to the ecu for datalog for all 4 primaries.
Feeding pretty proud, time to do some real testing. Call up Kevin to see if he is available to run the laptop while I drive on the road dyno.
We did about 10 runs with various load and RPM conditions.
Took many hours to get the data off the laptop, formulas built and interpolation tables to drive output of some meaningful and understandable graphics.
Be careful how you look at the data as the scales are different.
Two charts so far, at much different rpm and loads:
Low-Mid RPM

Upper RPM

As suspected, 1 and 4 can have a pretty sizable delta, but I got Science to back me up...

[Geoff]

So you built a pretty nice exhaust manifold. Maybe you could build a nice intake manifold to help reduce that delta...

[speedysaab]

Love this project so much. Any reason for a rich wot Dennis?

[squaab99t]

So you built a pretty nice exhaust manifold. Maybe you could build a nice intake manifold to help reduce that delta...

That might be the next project? But the plan is to install the new ECU first, that has trim capability for fuel and ignition timing per cylinder. See if we can pull the lines together at the correct AFR. Trim per injector can be tailored at load and rpm map.

Love this project so much. Any reason for a rich wot Dennis?

Thanks, it has been a fun and rewarding project.
Rich?, well it has not been tuned at the dyno since I had the OEM manifold and the GT3071R turbo. I have since added the new header and gone with the GTX3067R turbo (smaller compressor). Might be pushing less air? Maybe the the average post turbo AFR across the 4 is not an accurate reading versus the individual per cylinder? We were also running the water/meth injection on those runs. 50:50 by mass mixture, so the methanol is a fuel and that is adding to the richness. It has been 5 years or more, but I recall tuning without the water/meth injection knowing if we ran out, we would not grenade the engine due to excessive timing or lack of charge cooling. Not the best strategy to get the most power, but a safe one.