Perhaps it's primarily the supercharger intake distribution but there is a turbo feeding the whole thing. I've been running this thing for about 6 years now. The engine had a valve drop and destroy everything that moved. So I rebuilt it with a cnc ported head and better supercharger.

Now I'm noticing issues with extreme fuel trim adjustments. The center cylinders are getting loads more air than the other two. I noticed my outer plugs were black and sooty and the center were just white. It runs on pump e85.

I run megasquirt 3 and adjusted out the rich/lean plugs and ended up at a 30% fueling difference. I think you can see why. The center cylinders are being directly shot by the supercharger outlet. It's a Buick m62 that I reversed the rotation on. The engine is a D16z6 living in a CRX.

It has 1200cc peak and hold injectors. I flow tested the PTE brand injectors which were 10 years old and they were maybe 6% off of each other. Just the be safe, I put in some new deatschwerks injectors which are less than 2% out of balance.

The way this thing works is, the turbo feeds the intake and the supercharger compounds it. The supercharger bypass opens with closed loop control of a servo as the boost target is reached. Once the turbo is at a higher pressure than the supercharger set point, the bypass is fully open. I'm not really certain if the flow from the turbo is going fully through the rotors of the supercharger or if it's through the rotors and the bypass.

The plenum internally is about 9.75"x5.5"x2".

Sparkplug reading doesn't really tell me much other than there is a serious imbalance at some point. I'm installing EGTs and connecting them to an Innovate TC-4.

There are plenty of pictures at flickr and the build thread is here. https://www.d-series.org/threads/d16z6-crx-twincharge-build-with-buick-m62.217609/ The engine made 400whp and 300lb/ft torque years ago. Now it's down on power and has done some heat damage to the cylinders. I don't want to remachine the block until I'm confident that this is solved.

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Question 1: How do I do trim balancing with EGTs. Am I looking to equalize the temperature? I have a map for each cylinder so it's not just a blanket adjustment.

Question 2: How could I go about balancing the airflow here. I was thinking about putting a plate over the supercharger outlet to help direct flow away from the center cylinders. Would a perforated sheet be a good idea to diffuse the airflow? I hate to make the airflow less efficient but it's really out of balance right now.

 

I would agree, the blower is gonna push on those center cylinders.
As for the inlet of the turbo. That intake design will for sure starve the cylinder closest to the inlet. Flowing air is gonna rush right by it causing a low pressure area. The cylinder at the back side of the inlet very possibly could be the the same issue but from the flowing air hitting the back side and tumbling it back towards the middle of the intake where the center cylinders eat it up.

You may want to go check out the intake designs under "intake maniflold design" thread in the advanced section. Definitely go thru it.

I believe your problem is the intake design. I do like how you bypassed the blower. Should be able to make this work with some reconfiguration for air distribution. Possibly even some baffles to redirect air.

 

I joined this forum because I read that thread. I need ideas on how to baffle this thing to direct more air to the outer cylinders.

 

trial and error. Ive done it with air hats. Just didnt put a top on it. Covered the top with clear kitchen wrap and blew smoke thru with a smoke machine to see what the air did. Also did a before and after blowing air from a vacuum thru the hat and out the carb to verify air flow equality.
So you could cut the top off, blow some air thru it and see how the ports are flowing, blow some smoke, tack some material in to redirect the air, smoke it again seeing what it does until your happy. Then verify air out the ports again.
I sounds super hillbilly but on the two combos it did it on, all the cylinders are even.

 

Does airflow distribution through a manifold change when the pressure changes? Vacuum vs boost. Unfortunately, I think with the supercharger rotors being right in the plenum, this kind of testing might not work right. I need a motor to spin the thing on a bench or something.

 

Not really. Pressure doesn't change direction. Airflow direction can change with velocity.

 

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