Modifying intake manifold

[spink]

Anyone know if the manifold could be modded to increase power output? What are the differences between the 3B manifold and the RS2?

[Pisobiker]

3B intake manifold's internal volume is ~3.3 liters and RS2 one is ~4.2 liters (both including the 5 inlet ducts).
I don't know if the exchange of the IM alone would make any difference on a stock 3B engine (ABY, with slightly higher boost, uses same volume IM as RS2), but I believe it does on tuned engines.
Plenum volume is supposed to let intake flow settle and feed each cylinder with same pressure. If any improvement could be obtained by using the bigger volume IM, this would mean that some of the cylinders, using the small volume IM, actually get less than the max boost reached in the plenum.
Any upgrade on the engine that gives more flow (stroker kit, head porting etc.) or gives more charge density (increased boost, bigger or more efficient intercoolers, whater injecting etc.) would very likely also need some IM tuning to maximize improvements.

Marco

[porkkis]

The Swedes at www.irry.com seem to drill out the maintenance tubes from 3B IMs.

Marco,

Corky Bell in his book "Maximum boost" recommends plenum size of 0,5 times engine volume. That makes 1,1 liters. Runners (the 5 ducts of the IM) are not included in that plenum volume.
So original IM seems rather large as I guess one runnes isn't a lot more than 0,2l.

[Pisobiker]

I'm sure Mr. Bell knows what he's talking about (I don't know him and never had the pleasure to read some of his literature) but apart from a rough practical guide that can relate engine displacement to plenum volume, variables that concur to determine optimized volumes are a lot more, like flow pressure (which is the absolute pressure range that make that formula usable?), effective flow mass (thus including all density related parameters) internal casting finish, lenght of plenum, layout of intake of plenum and distance of it from nearest and farthest runner.
Take into account that all dissipating forces follow exponential laws so that increase in flow speed and or density make dissipating forces increase more than proportionally.
Pressure in the inlet of runner is the sum of pressure in the plenum (which is also dependent to the volume changes among different sections of plenum) + the kinetic factor of flow which will definitly be different between, for example, 1st cylinder and 5th cylinder runner inlets. So, decreasing volume of section going farther from plenum inlet, are supposed to compensate for volume reduction while each runner is reached + pressure drop caused by friction between flow and plenum walls (that is influenced by flow speed and flow density). A big plenum volume will decrease the kinetic factor of flow, therefore making it less sensitive to flow speed and density variations.
Probably only usable way to check if IM is well dimensioned for each setup is to test simultaniously all pressures in the runners from 0 to max boost.

I didn't find the page where the IM you're talking about is shown (in the Irry site) but I guess they drill away the maintenance holes just for an "aerodynamical" reason: the internal columns will cause some flow disruption (turbulances) that decrease actual boost fed to furthest runners.


Marco

[Mark Halligan]

Marco,

I was looking at my old ABY IM earlier and exploring the idea of cutting and turning the main body of it 180 degrees and re-welding.
I think I've grasped what you are saying (late night and busy day :wacked: ) in that the fact that the cross section of the IM actually decreasing the further away from the throttle body is a good thing, and helps contribute to equal distribution to all cylinders?
If so I think that I will try this mod, although it will involve a lot more than 'simply' turning the IM 180 degrees to get it to fit .

I can't help thinking about the other tuners front entry IM's from MTM,TS and Wagner,
http://www.wagner-tuning.de/content/index.html and scroll down.

as these 'seem' to have a uniform cross section along their lengths and possibly a larger volume than the ABY/ADU ( I would'nt be suprised if they were all the same casting!) Is there any advantage to this do you think?

Am I on the right track?

Cheers,

Mark.

[Mihnea]

@Mark: I can now confirm, they are all the same casting, all of them being copied on MTMs proprietary design (??) IM. Checked pics of TS and MTM and checked mine, the casting is the exact same for all of them!

Mihnea

[Sweeper]

Mark: Eh u b@stard . I didn't want to talk about it till I make it myself but oh. I was pointed to one of the service guys here in Latvia, who turned IM 180 degrees and install it on his 2.2 turbo engine. He's now selling the car for about 8000$.

I was planing to go for a RIDE and look under the bonnet to check how it was fitted there(no intensions to buy the car). I just don't have free time to do that now. But as far as I know everything worked fine.

Their car :
(280HP, 1990 20V 2.3 90 Body Shell,sport exhaust,sport hidrokompensators,K&N filter,MTM chip,hidraulic handbrake,shorteret wheel spin to 2 turns)

I guess it his pictures (taken from their service web site)

And engine picture :

[Pisobiker]

Originally posted by Mark Halligan
Marco,

I was looking at my old ABY IM earlier and exploring the idea of cutting and turning the main body of it 180 degrees and re-welding.
I think I've grasped what you are saying (late night and busy day :wacked: ) in that the fact that the cross section of the IM actually decreasing the further away from the throttle body is a good thing, and helps contribute to equal distribution to all cylinders?
If so I think that I will try this mod, although it will involve a lot more than 'simply' turning the IM 180 degrees to get it to fit .

I can't help thinking about the other tuners front entry IM's from MTM,TS and Wagner, as these 'seem' to have a uniform cross section along their lengths and possibly a larger volume than the ABY/ADU ( I would'nt be suprised if they were all the same casting!) Is there any advantage to this do you think?

Am I on the right track?

Cheers,

Mark.

Mark,

I cannot tell if MTM (and/or Wagner Tuning) IM design is actually 100% optimized for theyr respective engine and tuning setups, but differences of flow and charge density through the IM will definitly affect how each cylinder will be fed. For extence a 450 hp engine setup will require a much higher flow+density charge that the one of a 300 hp setup, thus upsetting all the pressure+kinetic flow calculations for optimizing plenum dimensions.
What I mean is that for the ~300 hp RS2 setup the original decreasing volume plenum maight be optimized but when you increase pressure and flow, pressure drops caused by internal drag and aerodynamical turbulances must be compensated by increasing the volume: in a closed system total energy of the fluid going through a pipe remains constant. Total energy is sum of kinetic+pressure+potential energy factors, so given the potential one will remain constant, to increase pressure you have to decrease velocity therefore increasing duct section. (Bernulli law of energy conservation for fluid dynamic closed systems).
As a matter of fact MTM, for theyr 450+ hp setups, may have found the right dimensioning so that the resultant of plenum diameter reduction when reaching each cylinder + plenum diameter increase for compensating pressure drops seems, from the outside, to be just a simple "same section" plenum.

If a small volume plenum (together with the shorter inlet plumbing route as possible) will give faster build up of boost, bigger volume plenum will reduce kinetic factor of flow thus reducing also friction losses that raise with the square of velocity.

I dont' want to make things more complex than they are, but in this case 100% optimizing is a matter of good calculations + some nice work on a flow banch.
What I can say is that turning the intake so that TB is front mounted will reduce significantly total volume of system + lenght of plumbing. The two factors will at least give faster build up of boost and less internal friction, the latter therefore giving a smaller pressure drop between turbo cold side outlet and IM inlet.
Then to optimize internal dimensions and make sure you feed each cylinder with same flow you should measure pressures in the runners as sayd in my previous post. If differences among runners are consistant you may want to modify plenum dimensions (welding, for example, a calibrated increasing volume of "cone" section).

All this academic talking may seem to the most a waste of time (and they maight be right), since the gains actually obtainable aren't so big compared to the work they involve. Take into account that if you for example find out that 2 of the 5 cylinders at redline get 2.4 bar absolute instead of 2.5 of the others, gain for optimizing pressures would be in the 1.6% range. If you add some overall pressure gain of a bigger internal volume + shorter plumbing, this, for a 450 hp setup, could roughly mean some 10 to 15 hp.
Too little for the hassle?
Probably yes.... but not for everybody


Marco

[Mark Halligan]

Marco,

thanks for the reply, much to think about and research .
I think I will make something of my own although I'm not sure just what.....yet.
Apart from being cheaper it will be more satisfying (assuming it works well) in the long run.

Mark.

[Pisobiker]

Mark,

I would have been really happy to give my support and contribution on finding a good IM layout for your application that could also give some nice data for other applications (mine included ). Unfortunatly distance doesn't help .
It's already some time I'm thinking of making my own front mount IM and now, with that ......"thing" ( ) coming from the States (hopefully , already payed...) that mod would probably be a must.
At the moment I'm in the process of having some "Tig welding" training (togheter with my friend that owns the welding machine) so that I hope I soon would be able to do the "cut and paste" job myself on aluminum parts as well .

Anyway, for your specific application, your porting and polishing work on the cylinder head will again change all flowing and density values thus involving some optimization work on many mechanical and electronic management systems:

Your volumetric efficiency will increase, at least in the mid to high rpms, which means:

1) with same pressure read at manifold your turbine must provide a higher flow (=> boost and fuel management optimization);
2) with same intake duct diameters speed of flow increases (=> higher friction losses);
3) with higher flow and pressure your IC will cause higher pressure drop (apart from heat exchange issues);
4) with higher flow and pressure, IM design must be optimized (if equal flow must be kept on runners).

#2 to 4 optimizations aren't absolutely necessary, but if you want 100% out of your mods they must be taken into account.

Another important thing (you probably already know, but I write this down anyway) is also to modify IM runners accordingly with the porting of cylinder head so that the match is perfect (and also IM to cylinderhead gasket). Apart from porting, slight metal removing to make IM and EM + gaskets perfectly match to head ducts is something worth even on original engines , where castings and matching are never 100% perfect.


Marco

[Mark Halligan]

Well, I cut up my old ABY IM today (as you do ), with a view to possibly turning it around 180 degrees and re-welding it, here’s a picture of what it looks like inside (sorry quality is not too good).
You can see the maintenance tubes Porkis mentioned being drilled out by some DIY tuners and on the face of it that could be a good idea as they are quite large and possibly obstructive to flow?
The entries to the runners are good and are nicely bell mouthed for good flow, the inside of the casting is a little rough.
If I was going to stick with the standard 3B, ABY, ADU manifold and wanted to improve upon it as Spink asked, opposed to the front entry IM’s from MTM, Wagner, homemade, etc. I would remove the maintenance tubes, weld up the holes, and possibly have the casting extrusion honed to smooth it out a little, inside the plenum and runners.

Just some thoughts,

Cheers,

Mark.

[S2central.net]

@Mark - Oi geezer that's quite a penknife you have there

Jokin apart, I recall am article written by someone respectable & trusted ages ago - he used to write the best tech articles in CCC and spent ages improving flow rates on cylinder heads. I clearly remember that he said there can actually be detrimental effects on smooting out all the bumps, knurles and castling textures on inlet manifold walls as the process can actually reduce the 'swirling' effect of the air into the engine. Maybe the comments only applied to a specific head or IM.

Maybe my memory is just pants, but thought I'd offer it up for discussion...

Paul

[Mark Halligan]

Paul,

You could well be right, who knows especially when it comes to forced induction.
I did do a bit of reading up today between butchering expensive bits of metal, and one book I have, advised smoothing out any high spots (welding dags, etc) and then in another paragraph said that inbuilt turbulators can help with equal cylinder distribution :wacked: .
On another note, does anyone here know if the SQ KW inlet manifold can be adapted to fit our engines? I know it has the water manifold built into it, but I think I read somewhere that it could be made to fit?


Cheers, Mark.

[Martynf]

Mark,

That KW inlet manifold is a bit of a non starter from a parts point of view... the manifold went obsolete in 2002 as did the gasket for it too!!! when... the inlet manifold was available, it sold for £1200 :eek2: she's a BIG girl too!!

Martyn

[Mark Halligan]

Thanks Martyn

Mark.