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I need to bring out a new - clean thread regarding this issue as the rest of the threads got really mixed up with so many different opinions in the past, I couldnt get to a conclusion.

I finally found someone in Cyprus who is willing to do my exhaust manifolds for my 16V Alfa 33 - non catalytic.

What I know for sure, is that I need to have an end pipe on the manifold of 56 or 57mm - 2 1/4 inch.

What I dont know, is if the guys who made a crossover manifold had better results from the guys who made a straight manifold.

The car is used as a fast road car and its modified to 1.8ltr high compression with fast road cams and omex ecu.
Better torque and more power are whats requested from this upgrade, as well as for the boxer sound.

Can we get to the bottom of this ?

I need to know which type to do ( straight or crossover ) and also the design and dimension and lenghts of the tubes.
I cant afford to the this wrong, as these custom made manifolds dont come cheap :rolleyes:
 

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I've ran with both in the past, and found the crossover type gave me more torque at lower Revs, but that's just what I noticed not fact. I did notice I had less ground clearence with the crossover
 

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So did I johnboy, as I say I've ran with both and it is questionable if it made much difference in feel, maybe it did on paper? I did run a straight through middle for a while, then but a new middle box in and I noticed right away the engine was pokier with a middle box, maybe the sweetspot of air flow and back pressure is key? Could be wrong but that's what I've noticed personally
 
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the system i built for BLS is by far the most common layout for any boxer engined car on any grid in any race series that includes them.

as johnboy says quite correctly, and as i discovered when researching the build/design.

i also spoke at some length with AHM, who probably has the Holy Grail of boxer engine development to coin a phrase, and he has tried them in the past, but does not use them now, and said he would not again.

the BLS system i built, was a new version and an improvment on an existing manifold they had already been racing with, and had been designed by a Cosworth associated engineer, again, stock layout, but equal length, and i came into the picture because their new engine will use higher revs's and higher state of tune etc so needed a manifold design tweak to maximise the new motors characteristics, and they also repeated AHM's findings, and confirmed that they knew no-one in a competition boxer engined car, that used a crossover.

i think that speaks volumes personally.


however, and just to make a mess of my own answer (keeps the thread interesting anyway!)

I have spoke with Dave at Brunswick, regarding being commissioned for a race manifold, and it sounds like he would like a crossover manifold design, BUT, the difference is, the car will be running a dry sump, which means that virtually all the depth of the sump pan will disappear, and this will give me a lot more room and scope for pipe routing the front branches.

Dave clearly has had some very competitive cars running his idea's, designs and handywork, and i would never go against what he has found to work for him in the past, but that doesnt answer the question as to "which is best?" either,

so i believe the only answer i can offer as a 100% gospel, is that given the room and clearance, the crossover can work well, and may be suited to certain engines very very well, but is it any better than a well planned/built equal length on the same engine? I don't think so.


myself, i will build for my own 16v and would recomend for a mildly tuned 16v under 2.0, an equal length stock layout manifold, 4-2-1,

2"/2.25" system, (no centre box required if the system is kept to reasonable shape and size IMO), keep the heat and flow going, finish in a reasonable sized back box and tip,

thats what i'll be doing,

shrew
 
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the system i built for BLS is by far the most common layout for any boxer engined car on any grid in any race series that includes them.

as johnboy says quite correctly, and as i discovered when researching the build/design.

i also spoke at some length with AHM, who probably has the Holy Grail of boxer engine development to coin a phrase, and he has tried them in the past, but does not use them now, and said he would not again.

the BLS system i built, was a new version and an improvment on an existing manifold they had already been racing with, and had been designed by a Cosworth associated engineer, again, stock layout, but equal length, and i came into the picture because their new engine will use higher revs's and higher state of tune etc so needed a manifold design tweak to maximise the new motors characteristics, and they also repeated AHM's findings, and confirmed that they knew no-one in a competition boxer engined car, that used a crossover.

i think that speaks volumes personally.


however, and just to make a mess of my own answer (keeps the thread interesting anyway!)

I have spoke with Dave at Brunswick, regarding being commissioned for a race manifold, and it sounds like he would like a crossover manifold design, BUT, the difference is, the car will be running a dry sump, which means that virtually all the depth of the sump pan will disappear, and this will give me a lot more room and scope for pipe routing the front branches.

Dave clearly has had some very competitive cars running his idea's, designs and handywork, and i would never go against what he has found to work for him in the past, but that doesnt answer the question as to "which is best?" either,

so i believe the only answer i can offer as a 100% gospel, is that given the room and clearance, the crossover can work well, and may be suited to certain engines very very well, but is it any better than a well planned/built equal length on the same engine? I don't think so.


myself, i will build for my own 16v and would recomend for a mildly tuned 16v under 2.0, an equal length stock layout manifold, 4-2-1,

2"/2.25" system, (no centre box required if the system is kept to reasonable shape and size IMO), keep the heat and flow going, finish in a reasonable sized back box and tip,

thats what i'll be doing, .....

shrew
.... to my sud;)
 
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Discussion Starter #11
Shrew, in other words, for my engine setup, you are recommending a straight type equal length manifold, not the crossover one, with 2" diameter or 2.25" ?

Might be getting somewhere here :)
 
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tell me a bit about your engine and set up mate?

but right now, that would be the best advice i could offer.


i know its been said before, but there are also two important, but none technical reasons, why folk today still query the crossover layout option.

firstly, Alfa themselves used a very very crude crosover design, "claiming" to get back the power loss that the very last 33 16v's suffered due to the fitment of CAT's that restricted the exhaust flow in the first place.

because of the claim, people assumed that a crossover manifold must therefore be worth horsepower all on its own, and it became considered a possible performance enhancer, when in fact the AO version was pure compromise, and my 4 year old could accidently make a better shape with pipe cleaners!

secondly, the name Ansa, for many, provokes fond memories for starters, even me, i had my fair share of Twin Tips myself back in the day too. Ansa did manage to become a brand attached with the notion of performance enhancement, and so everything they did MUST be good,

when in reality, back then, just as today, there are plenty of brands and companies out there that will convince the naive that even the right back box is worth 15 horsepower, or maybe closer to the truth, the naive convince themselves?

Just because Ansa did it, and lets face it we have never been blessed with a plethora of choice anyway, doesn't mean it was the best available, although that doesn't mean that it didn't work at least as well as the primitive stock offerings anyway, which brings me to a final point, which is if the stock pipe worked so badly in the first place, it can be very easily improved upon, and maybe this again is another reason for the everlasting belief in the Ansa crossover.

So now the technical standpoint on the Ansa version itself, at least my experience with the one we believed to be an Ansa Crossover that Rodger lent me way back on the first pipe build i did, was that although i can see where the idea of mixing the front ports, then the rear ports, from a firing order, scavenge, and back pressure point of view could be of advantage, the pipework i examined simply wouldn't achieve it in a month of sundays.

the primary lengths were massively varying lengths, and even simplified and thought of just as mixing pairs, the gas pulses would collide in the collectors so awkwardly, it simply wouldn't work, so enter into the design the full set of primaries and the impact of the now mixed pulses from all four primaries into the collectors and secondaries, and it looked like an unholy mess of a thing!

i took the route of a closely matched length primaries for my crossover, (tough to get close due to routing but we got it pretty good) and i think that puts some mileage back into the theory, but for reasons of lible, please don't ask for my written opinion on the Ansa version of old!

does that help a little further?



Kev, sorry to hear that work is still, err, crappy, or sorry to hear you're still there, which ever you prefer buddy?

truck driving eh, come with me on my new car courier sideline venture mate, always room for a drivers mate?

i'll see what i can do about the meet, sounds cool, but i don't have a driveable Alfa, boo hoooo!

shrew
 
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sorry to highjack the thread but I might come to the meet next sunday, sounds good

at the risk of hijacking it further (sorry chris ;)) you would be more than welcome mate, and be nice to see your 33 if you bring it?

only a quick morning chat over a fry-up, nothing at all serious or formal. most folks will be gone on there way back home by dinnertime so don't feel it's the day wasted :thumbs:

Kev, sorry to hear that work is still, err, crappy, or sorry to hear you're still there, which ever you prefer buddy?

truck driving eh, come with me on my new car courier sideline venture mate, always room for a drivers mate?

i'll see what i can do about the meet, sounds cool, but i don't have a driveable Alfa, boo hoooo!

shrew
don't tempt me mate, wouldn't take a lot for me to walk away :D

bringing an alfa isn't compulsary, pretty sure kris will be coming in his old merc chugger :lol:
 

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Discussion Starter #17
tell me a bit about your engine and set up mate?
Thanks for the detailed answer on this Shrew,

You do make a very strong point regarding the loss of power on the cat models and the lack of choice for manifolds.
To be honest, the catalytic 33's I've driven feel so cut off on power even with the crossover manifold type, that if thats compensation for power loss, I'd hate to see how they were before that :eek:

My setup:
89mm forged JE pistons - 11.5:1 cr taking the engine capacity to 1800cc
skimmed heads to 29 cc per cylinder "cup", polished and slightly ported intakes and outakes, stock valves and retainers - hydraulic tappets.
NON catalytic engine version.
Colombo & Barriani Fast road Medium cams - to work with hydraulic tappets.
Gozzoli vernier cam pulleys - yet to be installed
Lightened flywheel - which will be replaced to a stock one out of a 146 as I feel like I lost some torque but I'm very sure that I've also lost clutch biting point. Racing 4 ply custom made clutch and plate will be fitted when I drop the engine for the installation of the cam pulleys.
OMEX ECU and peripherals - Dizzy removed and replaced by OMEX coil pack, magnecor KV85 spark cables, NGK platinum spark plugs.
BMC cold air intake - the classic carbon cylindrical air box.
BOSCH Competition fuel pump
57mm diameter exhaust pipes follow a very thin straight through mid box, ending on a straight through back box.
Engine revs to 7500rpm

Rolling road tested with wrong valve timing gave 160bhp with 18Kg torques.
After the installation of the vernier cam pulleys and with the valve timing fine tuned and OMEX ignition timing corrected, will be looking at approximately 190bhp.

Mapping "guru" Frazer who mapped my car the second time and messed it up, said that my exhaust manifolds got so hot, they reached temperatures of turbo charged cars.
Mind you, my mixture was very rich at the time so that might have something to do with it as well.
 
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the hard parts resemble most peoples wish list for a fast boxer 16v, and a very nice list too mate,

what use is your actual engine for?


you're right the mixture would have to be very rich to get to those sort of temps i think, makes me wonder wether it was firing a little early too which increases the exhaust temp aswell, could that have been possible?

shrew
 

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Discussion Starter #19
thanks mate, I've spent a lot of money on this car.

What use ? Hmm... lets just say that I'm not into comfort and silence, so I drive my 33 two or three times a week, loving the mountain roads and having a lot of fun with it.
Its a fast road car, but yet fitted with a very nice quality sound system.
I love to tease boy racer cars as well.

Lets just say its my toy ;)
 

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thanks mate, I've spent a lot of money on this car.

What use ? Hmm... lets just say that I'm not into comfort and silence, so I drive my 33 two or three times a week, loving the mountain roads and having a lot of fun with it.
Its a fast road car, but yet fitted with a very nice quality sound system.
I love to tease boy racer cars as well.

Lets just say its my toy ;)

Man after my own heart :thumbs:
 
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