General question
thomas walter x5955
walter at roadster.sps.mot.com
Fri Dec 29 19:30:02 GMT 1995
> From: pantera at dris.com (David Doddek)
>Tom writes:
>>On a MGB witha 5 port...
> Actually the injectors could be fires is a batch sceme twice a revolution
> and still maintain a even fuel distribution. Firing on the open valve is a
> contriversial subject.
Agreed with all the good stuff.
Problem with that siamese ported MGB head is if you batch inject
the fuel, that 1 and 2 will get different charges of air/fuel.
Firing order is 1 3 4 2 (standard 4 cylinder).
With cylinders 1 & 2 sharing the SAME intake port, (ditto 3 & 4),
Of a given 720 degrees of crank rotation, cylinder 2 has access
to 540 degrees intake charge, cylinder 1 has only 180 degrees.
So if you batch ONCE per revoltion... you MIGHT get a double
dose of fuel into cylinder 2, but ONLY air into cylinder 1!
Yikes.
Admitted this applies to the 5 port head, something of which most
of the members on the list haven't seen. ;-)
#1 INTAKE OPEN xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
#2 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx INTAKE OPEN
^---------^----------^----------^----------^
0 180 360 540 720 crank degrees
-------------######---------------######---- worse case
batch injection
---###-------###-------###---------###------- "twice per rev"
Uh oh...
[Please forgive the ASCII art, but this is a neat example
of odd ball problem]. ###### = injector is on.
Sigh, seems like the TBI IS the better solution for this
engine (compared to Port Injection). So I will kindly eat
my words that "port injection is preferable over TBI". ;-)
> By the way, I am going to turbo and fuel inject my neighbors mg sometime in
> the future.
neat... curious as to the fuel delivery system. ;-)
Cheers,
Tom Walter
Austin, TX.
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