Plenums/Plenii

Need help from a fellow owner, something to air - discuss away!

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ChrisL
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Plenums/Plenii

Postby ChrisL » Wed Oct 28, 2020 9:46 am

So I've been thinking - oh god here we go - about plenums, specifically the one on my car. Some of you may remember I had a go at making my own, well 3 goes actually and whilst the plenum I built works there are some things that could do with improving:
1. air flow, no. 4 cylinder looks to be running a little rich as its plug is consistently sootier that the rest. I think this is dues to the existing design just being a tube that extends beyond no.4 (inlet is no.1). There's a pic below of a plenum that someone sells to fit on Jenvy adaptors that shows a taper at the 'far end'. Also GTiR plenums do a similar thing. I can only guess, not fully understanding fluid dynamics, that the first 3 cylinders effectively reduce pressure, not by a huge amount (pressure moving at the speed of sound and all that) but enough to richen no.4

2. The injector bungs: They are made out of 1 or 2 mm ali, I welded them into the manifold plate, 10mm and well as anyone who's tried this knows welding thin to thick is hard, especially in a cramped space. They work but secretly I know I've got lucky and they are a concern, so I plan to move them to the runners

3. Fuel rail: Kinda linked to the bungs but the fuel rail isn't really in the best position, the injector plugs only just fit, the regulator hits the cam pressure relief outlet and I'd managed to strip the mounting points on the manifold plate and have heli-coiled them! So moving the bungs gives me an opportunity to reposition the fuel rail;

4. The position of the throttle body: After being very proud of my first lobster cut bend I realised it could have done with 1 less segment this would mean that the throttle body would line up perfectly with the charge cooler outlet and get rid of the dodgy angle cut silicone hose, that makes me wince every time I look at it! Also this would help to re-route the throttle cable

5. Vacuum bungs: Erm I've got 3! good hey I could have just had 1 and some t-pieces which would have meant less vacuum tube running about, also they could go into a better position, maybe 1 for all the rear of the car stuff (MAP/Gauge/FP regulator) and one for the bypass valve.

6. Velocity stacks: the current runners are just tubes that connect the big tube to the inlet plate, but properly contoured velocity stacks are the way to go!

I'm not a neurotic perfectionist honest; most of these issues I've said "feck it' to but I've got the time, tools etc so why not and I've I get it done before the rolling road great, if not well I've still got something that does the job...
Also depending on how this goes I might knock out the odd one for the cost of materials...

This is what I'm aiming for, found on insta and left the username for credit:
IMG_2044.jpg


current plenum:
IMG_8668.JPG


IMG_8665.JPG
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ChrisL
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Re: Plenums/Plenii

Postby ChrisL » Sat Nov 14, 2020 8:45 pm

It begins
3227E6B9-EDE2-4478-B9EF-A8DC82B7D102.jpeg
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Re: Plenums/Plenii

Postby greenwoo » Sun Nov 15, 2020 8:45 pm

oooh a winter lockdown project....can only assume that Jenvey and the like will have done plenty of research; Unless they saw a design on locostbuilders and thought ' hey we can knock those up' :lol: :lol: :lol:

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Re: Plenums/Plenii

Postby ChrisL » Mon Nov 16, 2020 8:29 am

Funnily enough Jenvey phoned me last week and offered me the job of lead designer but I had to turn it down as the money was crap!

On a serious note you're missing the point; as with the SC project, this is about the journey, the mistakes and hopefully something working at the end. In this case hopefully improving on what I've done before, learning a few new lessons, improving on old mistakes and enjoying the process the time spent working on a project.
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Rob E
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Re: Plenums/Plenii

Postby Rob E » Mon Nov 16, 2020 8:47 am

ChrisL wrote:Funnily enough Jenvey phoned me last week and offered me the job of lead designer but I had to turn it down as the money was crap!

On a serious note you're missing the point; as with the SC project, this is about the journey, the mistakes and hopefully something working at the end. In this case hopefully improving on what I've done before, learning a few new lessons, improving on old mistakes and enjoying the process the time spent working on a project.

Agreed
Look forward to some vids and pics either way, could help someone thinking of doing the same plus we get an ali welder to send bits too :D
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Tony B
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Re: Plenums/Plenii

Postby Tony B » Mon Nov 16, 2020 9:52 am

Rob E wrote:Look forward to some vids and pics either way, could help someone thinking of doing the same plus we get an ali welder to send bits too :D


I was thinking more along the lines of once he's mastered it he sends out his Ali welder for us all to increase our skills!

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Re: Plenums/Plenii

Postby greenwoo » Mon Nov 16, 2020 11:52 pm

On a serious note you're missing the point; as with the SC project, this is about the journey, the mistakes and hopefully something working at the end.


that'll teach me to write a response without clarifying...
i was attempting (badly) to reference the fact that tapering the plenum may/should sort out the running rich on whatever cylinder.
and actually am a bit envious of folks that can weld...to the point where i started to look up last week what welder a beginner out to buy, so i can try to learn a skill.

(needless to say with my shocking time management, i saw 90sec's of a utube vid and ran out of time to see the rest....which suggested that possibly a welder/hobby wasnt likely to get much use if i have bugger all time)

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ChrisL
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Re: Plenums/Plenii

Postby ChrisL » Tue Nov 17, 2020 8:40 am

It's certainly time consuming, it's like an airfix kit except you've got to design it as well and make it fit whilst still being able too put it together.

@TonyB I think I'll be in my grave before I master it! I've just about got to a point where it sticks!

@Rob You're welcome to ask, but no guarantees (see comm ent above!) :lol: :lol:
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Re: Plenums/Plenii

Postby ChrisL » Mon Jan 11, 2021 2:50 pm

Still very much in the prototype stage but figured I’d stick a pic up of where I’m at, space is the main problem or rather the lack of it, currently bouncing between a tube or a box on this:
05B3D2BD-E2D2-46EF-8C01-5C1BFC53D1F6.jpeg
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Re: Plenums/Plenii

Postby ChrisL » Sat Mar 27, 2021 2:42 pm

It’s taking shape although the TIG is being a pain as I can’t seem to find the sweet spot! The velocity stacks are the same ID as OD of the runners, so I used a plug to get them central and welded them to the plate then added a little 1 cm section of the runner tube and ground it back to create a smoother transition.

Pretty it isn’t, but like me :lol:

E67A8283-8C4C-4D70-9BFE-CCA9781155F7.jpeg


09457D69-55BF-4BEA-A099-C1AE487EF4B8.jpeg
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