Timed Injection for Siamese Port Six Cyl - uS

[Steven]

I’m currently enjoying driving my newly turboed and uS’d 6 cyl C10. And everything seems to be working as it should. However when I was trying to solve some of the early issues one of the guys mentioned some code specifically for Siamese Port engines. From what I can determine on the 1970’s 250 turbo thrift engine the firing 153624 will give two Siamese ports that are 240-480 degrees apart and one that is 360-360. I also understand that my current setup of 2 squirts per cycle (uS) is initiated randomly on startup but should give good results most of the time.
Currently I am running rich to make sure that I don’t have issues with one cylinder running lean but I would like to take the tuning to the next level and time the squirts… 1st to the crank number 1 tooth with an appropriate offset and 2nd before my next build using a similar engine and a Megasquirt I’d like to time the individual squirts to the valve openings.

As usual all help greatly appreciated.

I have considered extending the exhaust flange into the Siamese port to try and somewhat separate the ports, this is a long shot though…

[Shane Lang]

where in mn are you located? I am halfway through turboing my 67 c10 with a 292.. ive read up on alot of this siamesed injection stuff... pondered fabricating a crossflow head from 2 sbc heads with 1 cylinder chopped off.. i could use some advice though. is that considered bank injection how you have it running? i have only just built my megasquirt and havent started any tuning. nice to see fellow minnesotans with simalar ptojects as you know as well as me how rare this is to see.

[Steven]

Shane
I’m in Jackson though not a true MN’n. My system is a bank injection system and it is this way because I was uninformed (ignorant) of the system and what was needed. The complication is the outer two cylinders having 480 and 240deg separation so one cylinder will get more fuel than the other, but the Oxygen sensor will report the average of the two (or six). If you are using the Megasquirt and have a third bank (driver) added then you may with the right code be able to get it correct. I am currently running uS and this I only have two injection drivers.

Funny you should mention the welded sbc heads as that is what I have been researching today. I’m going to cut a head soon and see what is required, I do have a spare 292 and a 230 lying around so I will see what can be done.

I was warned about the 240 and 480 deg separation issue but didn’t fully appreciate the magnitude of the problem until the first time the engine really got on boost. Then it bent a con-rod in an ‘s’ shape and I did understand the issue very well. The plan for next year is to over-fuel at high loads to save the engine and at least have some fun with the truck during summer.

Next project is a 1949 3100 and that is why I’m looking at the 2 x sbc head ‘cut and shut’ project.

Good luck with the Megasquirt.

Regards Steven

[Shane Lang]

Steven
Ahh that scares me! I don't like hearing about bending rods as I have a lot invested in this engine already. I too came up with this crazy idea and started buying parts before doing enough research. I really want to figure this out without cutting apart heads though. I have ms2 so i have added the 3rd driver. I think I am going to use Jeans idea of using multiple O2 sensors with sampling chambers to get a clearer picture of the AFR's. Do you have any pictures of how you did your trigger wheel?

--Thanks, Shane

[Steven]

i copied the 36-1 wheel from a ford minivan then used its vr sensor, i laser cut from 0.25 steel and added three lugs to fit the GM crank pulley. i can give you the CAD model if you like. you will have to give me a format.

[Shane Lang]

I was just curious as to how you did it. I'm mounting a 36-1 from a L-series Nissan to the back of mine.

[Steven]

Need Help... Again. Just got my Truck out and fired up with the reconfigured injection set-up (see siamese port setup) , i have been away from this truck for over a year and now i'm having trouble getting it to run. I am running a cheap turbo, intercooler, throttle body injection (injectors before throttle) GM LS throttle body, coil near plug (LS coils). i upgraded to the registered version of TunerStudio to try and get it to autotune but its running incredibly rich and hunting a lot. i am trying to remember all the hard lessons i had learned so far but getting old i guess.

[Steven]

Fixed it, wrong setting on the map sensor... Stupid stupid stupid