Airflow Demand in Siamese-port BMC A-series head

[Sir Yun]

RL, Vannik programmed/coded EngMod4T. Not much sense in arguing about what it can do

I can assure you it can do siamese 4 inlines and that only works when everything interacts.. it takes quite a bit of time to compute though.

the centre cylinders run at a lower DR at high rpm, but at a higher DR at low rpm as there is some sort of supercharging effect ( see link) . I suspect that at higher RPM the better scavenging action from the end exhaust makes the difference. In theory /model you can improve that by using a different exhaust. We will be testing that shortly

https://aseriesmodifications.files.word ... arrows.gif.


look at the mass flow trace of nr 3 &4 cylinder at 4250 rpm using a long 3-1

massflow.gif

EGT are different (that is in de model and has been confirmed by EGT data gathered from the folks that made port injection work) , I'm pretty sure they have dual AF sensing as well. I'll probably have definitive data in a few months ( as in In cylinder pressure data, intake and exhaust pressure data from dyno tests). I'm not sure If that will be shared because we first want to win some stuff

[RL]

RL, Vannik programmed/coded EngMod4T. Not much sense in arguing about what it can do

There is nothing on that site that shows all the capabilities of the program - I can't read minds -, from the outside it just looks like a Dynomation clone - it only shows single cyl pressure traces and power curve outputs -.

The author is shooting himself in the foot by not showing what it can do, because by the look of what you have just posted it looks like it has heaps more stuff than the general pubic would know looking at the site.

[Sir Yun]

How much charge robbing takes place is hard to quantify as it is rpm, induction,exhaust an cam dependent. As Modok mentions , split cam (does help a bit), twist crank (is a whole new can of worms, but it does work),run two different CR's. I did a rethink of the exhaust and there is a bit of gain there as wel

the mass flow race is just a quick one I dug up .It is a very long cam (312 I think)


You are right EngMod is a lot more elaborate than the site suggests.
it does temp traces , mass traces, Mach traces, purity traces, etc etc .. it even does noise spectrum. And that is just the main categories.

All of them have a whole host of sub categories.

My main problem is to make sense of it

To give an idea this is the list of just the burn data:
Deg Engine degrees using the last cylinder as reference.
HPistTDC The piston height from the top of the cylinder per cylinder.
Torque The instantanious torque produced or absorbed by the cylinder per cylinder.
VSqshAc The actual squish velocity in the cylinder per cylinder taking density and combustion into account.
VSqshTh The theoretical squish velocity in the cylinder per cylinder ignoring density and combustion effects.
Mun The unburnt air mass ratio in the cylinder per cylinder.
Men The entrained air mass ratio in the cylinder per cylinder (the mass ratio of air, but not all burnt yet, inside the flame sphere).
Mbt The burnt air mass ratio in the cylinder per cylinder.
TurbInt The turbulent intensity in the cylinder per cylinder.
TurbDis The turbulent disipation in the cylinder per cylinder.
Integral The integral length scale in the cylinder per cylinder.
Taylor The Taylor length scale in the cylinder per cylinder.
RFlame The radius of the flame sphere in the cylinder per cylinder.
AFlame The flame area of the flame sphere in the cylinder per cylinder.
VFlame The volume of the flame sphere in the cylinder per cylinder.
RBurnt The radius of the burnt sphere in the cylinder per cylinder.
ABurnt The flame area of the burnt sphere in the cylinder per cylinder.
VBurnt The volume of the burnt sphere in the cylinder per cylinder.
AWallU The area of the exposed wall in the unburnt portion of the cylinder per cylinder.
AWallB The area of the exposed wall in the burnt portion of the cylinder per cylinder.
RoHR The rate of heat release per cylinder.

[Larry Widmer]

The burr that Kevin Johnson posted will do the job. We used to run the engine a bit on the rich side and there was evidence that the back-flow was turning to the shared valve rather than fighting the incoming charge. I can tell you that the process allowed us to make power another 1500 rpm above the limit of the conventional ports. The 3-main bearing blocks didn't particularly like the increase in rpm, as we "separated" several blocks at the crank center-lines. On one occasion, a blow-up also forced a good portion camshaft out the side of the block, making it a permanent part of the header...

[Sir Yun]

Larry was that an A series or a B series?

[Dan Timberlake]

The burr that Kevin Johnson posted will do the job. .........

==============

This one?
download/file.php?id=9556

Kevin posted two types.

regards,

Dan T

[vannik]

You are right EngMod is a lot more elaborate than the site suggests.

Ok, I take note and will attempt to fix it - but I am an engineer and not a salesman so be gentle!

Vannik

[RL]

You are right EngMod is a lot more elaborate than the site suggests.

Ok, I take note and will attempt to fix it - but I am an engineer and not a salesman so be gentle!

Vannik

That's cool, but if I knew what it could do I wouldn't have dismissed it when I looked at it last year. All you need is screenshots of input and output pages.

We used to run the engine a bit on the rich side and there was evidence that the back-flow was turning to the shared valve rather than fighting the incoming charge.

What was the evidence? I'm interested in the mechanism so I can gauge the amount and whether it matters to fuel metering.

By the sound of it it's robbing the adjacent cyl, not the incoming charge in the manifold. If you look at cyl 3, 4 it's probably the negative exh wave when cyl 4 int valve opens pulling on 3, and not what I assumed was that it was robbing the inlet charge.

The whole reason I wanted to know the cause and amount wasn't about HP, which most assumed, but because I was wondering how you would EFI it if you only have a 4 fuel channel, 4 ignition channel, EMS that could only pulse once per revolution but had sequential. The EMS is limited and can't do what a full featured expensive EMS can do.

I was thinking about putting 2 injectors on each runner and running sequential 4 cyl.
Or run 2 inj channels on a single Injector per runner, and running sequential 4 cyl - not an electrical engineer so I don't know if it's more than a just couple of diodes -.

[Sir Yun]

I think you are on the right path.

I has been figured out by a few guys on turbominis.co.uk. they do it with a megasquirt with siamese code I think. It is quite hard to get to work as you have a very short window to get the fuel in so they use staged injectors as otherwise you can't get it to idle with the size you need for big power. Don't know enough about it though

there is some info here

http://www.starchak.ca/efi/siamese.htm

http://jbperf.com/sequential/index.html

[Leftcoaster]

Wasn't a new A series high rpm fully counter weighted aftermarket crank introduced for these a few years back?

Did anyone experiment with a 1-3-2-4 firing order to equalise induction draw on the siamesed 1&2, 3&4 ports?

[hoffman900]

Wasn't a new A series high rpm fully counter weighted aftermarket crank introduced for these a few years back?

Did anyone experiment with a 1-3-2-4 firing order to equalise induction draw on the siamesed 1&2, 3&4 ports?

There is the Swiftune set up:
http://www.swiftune.com/Product/1423/sw ... n-set.aspx

But this is the ultimate set up:

http://bwrperformance.com/a-series-all.html

[Leftcoaster]

If the BWR SCCA spec mini is a 1332cc version of 72.20 x 81.28 bore/stroke, producing >150bhp @9200rpm is surely "competitive"

Interesting that neither site gives much info on head mods - - some photos on BWR's site but nothing "in depth" - - anything else handy please Bob?

Presumably these hard core racers would have considered a 1-3-2-4 firing order but were discouraged by insufficient gain or rules

[hoffman900]

If the BWR SCCA spec mini is a 1332cc version of 72.20 x 81.28 bore/stroke, producing >150bhp @9200rpm is surely "competitive"

Interesting that neither site gives much info on head mods - - some photos on BWR's site but nothing "in depth" - - anything else handy please Bob?

Presumably these hard core racers would have considered a 1-3-2-4 firing order but were discouraged by insufficient gain or rules

Check out the latest posts here by Aaron.
http://www.vintageracerules.com/forums/ ... #Post11951

If you go back a page, you'll find info he shared on different ignition curves for different cylinders. After talking to Darin Morgan about it, he said it's not worth the time and they figured you can get the same effect with different heat ranges.

In SCCA FP, they run 2 x 1.5" SU, stock valve sizes, stock rod length, and only a .040" overbore. You cannot relocate anything or add material to any cast part.

GTL is open induction, rod length and valve sizes. Bore and the material added rule is the same as FP.

FYI. The FP car that Aaron builds engines for destroyed the FP field two years ago, including Joe Huffaker and his Midget. https://m.youtube.com/watch?v=sDfqTr0i6IQ (white car).

[RL]

I think you are on the right path.

I has been figured out by a few guys on turbominis.co.uk. they do it with a megasquirt with siamese code I think. It is quite hard to get to work as you have a very short window to get the fuel in so they use staged injectors as otherwise you can't get it to idle with the size you need for big power. Don't know enough about it though

there is some info here

http://www.starchak.ca/efi/siamese.htm

http://jbperf.com/sequential/index.html

I was also thinking about that second polar graph method, by injecting on the back side of demand, but it seams like it has problems as well.

The TBI method was also mentioned. and has been proven to work in the Rover TPI engine, but it seams that no one knows the actual semantics of that setup.

[Sir Yun]

GTL rules permit a x flow head.. so you can put an Pierce 7 port or Arden 8 port head on

150 would be extremely good for an iron 5 porter in any legal config, but for an Arden head it's not all that impressive . KC reportedly made 168 bhp using one of those.

150 bhp at 9200 It's a BMEP of about 11.0-11.3. (150-153) which is not unheard of for a 5 porter ( granted at lower revs) . piston speed will be 25m/s and you are still on three main bearings (with fake journals).

I reasonably convinced (or deluded )that you can get a bmep of 12 at 8500 with some expensive parts, hard work and some magic.

@RL.


TBI/SPI is basically electric carb, so you could do that just as well/bad as you could do using a carburetor , no magic to it , you just accept that it scavenges and run it rich it will get bad mpg and terrible HC numbers. The MPI setup rover made works but only up to about 90 bhp as after that it lacks the injector capacity to get enough fuel in given the small window. The turbo boys have sorted that more or less I understand.