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#Post#: 604--------------------------------------------------
Injector placement/type
By: Robin_16v Date: December 14, 2012, 11:46 am
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Hello,
I want to discuss the injector placement/type in this thread.
My first question is:
I'm currentley designigng a slide throttle with manifold and
thrumpets. Now i just got thinking about injector placement,
whats the best place to put them? I'm talking about 8 injector
setup.
Any thoughts would be welcome, thanks.
#Post#: 605--------------------------------------------------
Re: Injector placement/type
By: Tonyb Date: December 14, 2012, 1:04 pm
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This is an interesting one. The 'works' 16v VW engines seem to
run 8 injectors as do JRE top spec engines amongst others. They
are a pig to set up as I understand.
As I also understand the closer to the head the injectors the
better for bottom end power. The further away the better for top
end power. So ideally (you would imagine) you would have one set
in the std position and one set mounted out in the centre of the
trumpets at the far end.
I know one of the guys who runs a 16v who had to go to an 8
injector set up to find any torque in an ABF/KR type set up
after coming form an 8v Spiess set up. As this engine struggles
for good torque anyway seems like a good way to go.
As to type of injectors I don't know, but you want the type that
your ECU supports as a very minimum. You would imagine with 8
injectors you could get away with some fairly standard set up as
the flow is split across 8 injectors.
I'm sure Jason has some info on 8 injector set ups ;)
#Post#: 606--------------------------------------------------
Re: Injector placement/type
By: Robin_16v Date: December 15, 2012, 12:30 pm
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Ok thanks for the info Tony! and for further info, we will wait
for the master then 8)
#Post#: 607--------------------------------------------------
Re: Injector placement/type
By: Robin_16v Date: December 17, 2012, 12:08 pm
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[IMG]
HTML http://i957.photobucket.com/albums/ae52/RobinBreve/slidethrottle2_zps9c828fd5.jpg[/img]
#Post#: 608--------------------------------------------------
Re: Injector placement/type
By: mitlom Date: December 17, 2012, 1:51 pm
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Hi Robin,
I would have said the second set needs to be further upstream as
in at the opening of the trumpets, but let's see what Jason
reckons.
Cheers,
Tim
#Post#: 609--------------------------------------------------
Re: Injector placement/type
By: Tonyb Date: December 20, 2012, 11:35 am
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Tim, your still alive! :D
Normally I'd agree that they need to be in the centre of the
trumpets but if you look at the geometry they are pointing
straight down the centre of the inlet port which is what you
want, the curve on the end will mean you can fit them under the
bonnet and pointing forward so looks good to me.
I'm sure I've seen this set up on a European racer or a very
similar setup because I remember thinking that the injectors
were wrong and then realising where they pointed.
#Post#: 610--------------------------------------------------
Re: Injector placement/type
By: Robin_16v Date: December 20, 2012, 2:35 pm
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haha! and Jason? didint heard a lot from him the last view
weeks. probably very busy
Did made some changes to the design, will post the updated
version soon! Mayor changes would be the first set injectors,
there in front of the trumpets now, because of the bonnet
clearence, always could be changed.
#Post#: 1351--------------------------------------------------
Re: Injector placement/type
By: Tristan Date: November 15, 2013, 5:11 pm
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digging up an old thread , I recall Dave Walker testing 8
injector set ups , and found that you didn't just switch from
one set to another , they had to phase in and out? And that on a
2.0 Pug IIRC , the gains weren't that large.
#Post#: 1370--------------------------------------------------
Re: Injector placement/type
By: mitlom Date: November 17, 2013, 12:02 pm
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I vaguely recall reading that article as well Tris, can't
remember if it was on his website or in CCC magazine that he use
to have a column in from memory.
#Post#: 1371--------------------------------------------------
Re: Injector placement/type
By: Tonyb Date: November 17, 2013, 1:26 pm
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Pretty sure it was in CCC as well.
As I understand one of the reasons for 8 injectors was that
older injectors lost their spray pattern and control at bigger
flows so twin injectors allowed you to run smaller injectors
well within their designed range.
In addition you could inject fuel in at different positions in
the inlet tract [times] to suit the cam etc.
There is probably far more to it than that but as I recall it
meant more power could be made by better control over the
injectors as more fuel could accurately be injected and a better
spread and torque by better positioning/phasing.
With modern injectors I guess flow control is not such an issue
so I would imagine a more 'fussy' engine might still benefit
from the different injector positioning.
The KR and ABF 16v's seem to benefit from 8 injectors as both VW
and Audi top spec rally and race engines generally seemed to
have 8 injectors.
Just a few thoughts.
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