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| Iain G | Posted - 24 Feb 2023 : 06:46:20
I posted pics on the FB page up but not everyone succumbs to the global harvesters of personal data……Hoping to make the debate more inclusive…….
I made a custom inlet manifold for my red 96 V4. Its for a Weber dcnf carb mounted in-line. I have up to 40mm of space between carb and manifold for an insulation gasket and spacer so I can increase induction length and torque in theory. Question is - should I make two ports in the spacer or an open oval hole? Should I use the max space available? I could also divide the manifold for 1+3 / 2+4 etc.
It’s just a road car but interested to apply best practice.
Cheers
Iain G |
| 13 L A T E S T R E P L I E S (Newest First) |
| UK_Sub | Posted - 03 Mar 2023 : 12:30:31
I found out a bit more info on the supercharger and the owner also sent me a link to an alternative version...
It’s a Stewart Warner Unit… Off a B-24 USAF cold weather start up unit…
With a swept volume of 600cc.
Originally made with 1.75 stromberg… too tall.
Currently with an S&S Harley Davidson upgrade…
Heads are running 3.0 Cologne valves… 3 angled.
93mm pistons so it’s 1815cc
Slightly machined to just below deck height. So between low and high comp.
Cosworth 2.9 conrods….
High pressure oil pump
The elbow is off a FIAT 500 exhaust manifold…
Should really be more than 2 stud.
The big issue is clearance, the setup with the S&S carb is below the height of the heater. Just…
https://hydemotorworks.com/shop/product/amr-500-supercharger/?fbclid=IwAR209038JsN5cVqSwDg6m1m4IaQJRQr1mS94gE1WFWinz2DsM0MB3clOze0
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| ratty | Posted - 03 Mar 2023 : 10:57:00
There was a photo of a supercharger sat on a v4 inlet manifold? Has anyone got more details about this set up? Am thinking of using an AMR500 Japanese built? Cheap and Cheerful! Suck through a Weber or SU.
nigel martin-oakley |
| Iain G | Posted - 02 Mar 2023 : 10:40:04
I was looking at various Lynx manifolds for 2 chokes / 4 cylinders and all except one have a crossover so both chokes can feed all cylinders.
Only the DCOE Weber conversion for A series Mini has completely separate feeds.
Iain G |
| Vedrive | Posted - 27 Feb 2023 : 19:11:44
Well, it seem if you use common sense you make an open plenum, at least my friend also said so, he did some work with changing 4 in line engines from 1 SU carburettor to twin SU carburettor where 1 carburettor is feeding the 2 front (or rear) cylinders so similar as V4 cylinder 1 and 3
He is much more in favour by experience of a single bigger bore SU in central plenum than a split up as there is no risk 1 carburettor can choke the charge. Makes also sense.
But than he said "some swear by a dubbel barrel"
So whatever you choose lain G, keep us informed with some nice pictures (or a link to, when problems to post.
Melle,
Really looking forward to have them on the flow bench. Talking about tuning and real time figures, Some while ago thought about building an engine in my engine dyno to level up a bit.
https://www.matramania.be/phpBB3/download/file.php?id=9805
Schenck W130 Eddy Current engine dyno
But right now its one project too many, at least according to my wife. And I know without even asking.
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| melle | Posted - 26 Feb 2023 : 21:25:11
A V-twin won't suffer from charge robbing due to its layout, it will draw charge from left - right - left - right - etc. If you would completely split the front and rear intake on a V4, the cylinders will draw from (1) front - (3) front - (4) rear - (2) rear. You'd have the same problem if you'd split it left/ right: (1) right - (3) left - (4) left - (2) right, that's why I've removed the internal baffle in the V6 plenum I'm using on my EFI engine. I don't think Iain plans on spitting the intake though, as I understand it he just wondered if the spacer should have two round holes or one oval one. As said, I doubt it'll make any difference, but I can think of one argument against, and none in favour of two round holes, so I would make a spacer with one oval hole.
Re my manifold: the top has been milled off a single-choke manifold, and the new piece is cast directly onto it. Height can be milled to suit, and the inlet side can be ported depending on torque curve requirements. This is project #1337 on my list, so no real world results any time soon, but it would be cool to stick it on your flow bench Bonne! (Note that Joop has already ported it for me.)
www.saabv4.com |
| Vedrive | Posted - 26 Feb 2023 : 18:51:49
Very very nice looking rebuild manyfold Melle (compliments for Joop of course) I do not see any welds,or? How is it made?
Concerning the pros and cons of cylinder charge yr right could be, but I hardly dare to do any hard sophisticated statement on cylinder charging with that manifold so I see no hard don't do.
The charging with 1 barrel is in my opinion purely dictated by restriction in flow, improve that will help. I just like the idea of splitting front and rear flow as it sounds "something different to try" wit reminded me of V-twin set ups where it is not uncommon. I am also interested in the results with the Joop manifold you showed compared to the standard double barrel.
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| Iain G | Posted - 26 Feb 2023 : 17:20:27
Yes mine looks like Joop’s but carb mounting surface is lower so I have the max space in case I want to use on my Sonett some other time.
Iain G |
| melle | Posted - 26 Feb 2023 : 16:35:11
A reason I can think of in favour of one single port, is the firing order (1-3-4-2). Assuming 1 and 3 draw mainly from the front venturi, a two port set up might result in a compromised no. 3 charge. In practice, I doubt this is a problem, but I can't see any pros either.
quote:
Originally posted by Borstlap
Is it an reworked single throat manifold or a newly cast one from Joop (if I recall his name correctly)?
Modified single manifold from my friend Joop.
Stud pattern is for DGV/ DCD as that's what I originally thought I'd use.
www.saabv4.com |
| Iain G | Posted - 25 Feb 2023 : 17:27:04
Thanks Vedrive
I think I might go for two ports and see how it goes. I can open up to an oval later if I want to.
Iain G |
| Vedrive | Posted - 25 Feb 2023 : 11:02:02
Although most often the bad cylinder filling is mentioned with V4 alike manifolds (as V8 s), may be more important for such manifolds where a carburettor has to feed multi cilinders is the dramatic mixture distribution EDIT: special at idle and lower load where you cruise most.
By experience on better looking intake manifolds on inline cylinder engines I know you can have a Lambda sonde displaying a nice everage, lets say 1.0 value, the reality can be peak variation from cylinder to cylinder from an over rich 0,8- to a lean 1,2+ value. In my opinion it is 1 of the reasons why a good electronic ignition has such a positive effect on engine running in such engines as a good spark copes much better with lean and rich mixture.
I know even small changes in carburettor lay out can have impact on mixture distribution. (For better or for worse). Looking to the V4 manifold I think it is very difficult to make it worse. (If you look at it the positive way)
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| Vedrive | Posted - 25 Feb 2023 : 10:28:39
Personally I think Melles answer is as close as possible to what you can expect, but I am always in favour of people who try something. Whatever the outcome. Sometimes with suprises and not in the least the fun you tried something different.
Higher carburettor position with a split to front and rear cylinders as you mention, it will act more like a set up you will find on V-twin motor bikes with 1 carburettor, including the uneven firing order, its not uncommon. Perhaps no clear expectation for better results but also none that it will be worse in my opinion
For the torque improvent due induction length increase you mention, such predictions calculation is in general applied for systems where each cylinder intake has its own individual intake runner ending up in open air or a manifold with sufficient big air volume.
I am also curious to see pictures of the manifold / carburettor set up. |
| Borstlap | Posted - 25 Feb 2023 : 10:02:49
We'll also need a picture of yours Melle. Is it an reworked single throat manifold or a newly cast one from Joop (if I recall his name correctly)?
Alex |
| melle | Posted - 24 Feb 2023 : 09:10:45
I don't think it'll make any difference (Vedrive or AnttiK will probably have a more useful answer), but we definitely need a picture of your manifold! What size DCNF are you using? Someone made me a manifold recently that I purchased a 36 for.
www.saabv4.com |
