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MG Midget and Sprite Technical - EFI stuff... manifolds and air distribution

Hi folks, hope you are well!

It's winter and I am making a mess with my injected midget... Don't tell the folk on the MASC FB page ;-)

Just something for amusement and that might interest some of you. I have been stripping my head in readiness for some work to be done and I noticed that the exhaust valves get noticeably sootier from cylinder 1 to 4 (left to right in the pic). Clearly, with the log manifold as it is (see pic, without various bits like the injectors/fuel rail attached), cylinder 1 being closest to the throttle is getting loads of air and perhaps tending towards lean, whilst no. 4 is struggling for air and thus looking rich/sooty. (Note that the injectors fire the same amount of fuel into each cylinder).

I am now wondering how I can modify the manifold to even up the air distribution, how much power it might free up whether it is why the idle has always been a smidge uneven whatever I do.

Cheers,
Malc.







Malcolm

I'm pondering adding an "appendage" onto which I can mount the throttle at a jaunty angle. Hopefully allowing more air to flow along the red arrow area to the back two cylinders.

I wonder how manufactures get around this problem... I don't think my manifold is too dissimilar to what you find on a lot of production vehicles.

Cheers,
Malc.


Malcolm

You might want to check out the TR forums. Some TR6 owners have a similar problem.

One suggestion was a bigger plenum.





Dave O'Neill 2

Interesting. There is nothing new in this world! Thanks Dave.

I don't want to go too nuts on plenum size as it makes the throttle response a bit soft. But even a 3.2" diameter plenum as per the TR6 has a greater cross sectional area than what I have now. Although the problem will be even worse with the longer inline six setup of the TR6.

Cheers,
Malc.
Malcolm

Dont know Malcom , im not a sientist but could the airstream in your box not be right?
Does the box needs to be bigger?

My airbox on my K is bigger in size and allows me to have trumpets on the inlets to help airflow.
could the problem cylinders not get enough air for a perfect combustion?





A de Best

Maybe you should just fit a K. 😉
anamnesis

Arie: The runners are trumpet-ed inside the plenum :-) I am proud of that detail, shame nobody can see it! Are you running individual throttles? I can't quite see where the throttle is. That's a big air box!

Anam: if I fit a K then I will just be the same as everyone else. It's way more fun to show them up in a "crappy" 1500 ;-)

Malc.


Malcolm

LOL. Showing a clean pair of heals to a k, in a lowly 1500. 😄
anamnesis

Malc.
IF you've got enough room, I reckon maybe run the throttle body at 90 deg. into the centre of the plenum would make it more of an even spread
Also, because of the firing order being 1342, with it on the end where it is maybe your plenum hasn't got enough capacity at the rear and needs to be a couple of inches longer out past No4--My thinking is here that because of the firing order No3 would take a good suck at that end creating a lower pressure there, followed imediatley by No4--maybe-? there's not enough volume at that end and No4 misses out a bit, A bit extra capacity in the plenum there might help, but also, if the throttle body were to be moved to the centre then extra volume might be needed out past No1 as well
William Revit

Just found this--you might get some value out of it-- Not sure if there are follow up vids (part-2) but probably is

https://www.goengineer.com/blog/manifold-optimization-with-solidworks-flow-simulation-part-1
William Revit

Maybe a Turbo would cure it?
Rob
MG Moneypit

I have thought about turboing a few times. It would be relatively easy to do now. But I spent so much time with all the fabrication and packaging of what I have now, I don't particularly want to reconfigure it all again.

And the bottom end probably wouldn't take much more either.

It would be a fun project though... :-D

Malc.
Malcolm

This thread was discussed between 24/01/2023 and 26/01/2023

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