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fuel injection
Written by spacetiger_j... on 11/30/2010 at 03:55 am

Nice article, good info here.

I always wondered were to find the relationship between intake runner length vs.
cylinder fill volume vs. exhaust header length before collectors.

I always thought there was a relationship given the three different volumes that
you could find rules of thumb. That is, the intake fill volume downstream of
the TB needs to be X % of the cylinder fill volume and the exhaust volume before
the collector needs to be Y % of the cylinder fill volume.

I suspect that engine RPM is a significant factor too. That's why some of the
high end car engines that have a really wide RPM band have a dual intake path
for good low and high RPM performance.

For the PC800 engine, we only have about a 1,000 to 6,000 RPM band, so perhaps
this is not as critical. For a VT1100 engine, the RPM band will be even
narrower than the PC800 engine. In the dual exhaust system, I am trying to work
the "header" so the pipes are about equal length before the collector merges the
exhaust pipes together. Since the space will dictate what these lengths are
going to work out to be, I will not have alot of say in the matter. That said,
if I ever play with a FI system, I think I'd like to know how long to make the
intake runners between the TB and engine...

I'm open for thoughts from other gearheads out there.

BTW, I decided to build the exhaust system around the VT1100 engine. The
dimensions are a bit different (not much), but enough that the cost for doing
the exhaust project should be optimized for the new engine. That said, I will
still check to see how it fits on the PC800 engine for anyone else to try. Once
I build the initial "header" I will fabricate a jig using the initial header as
a pattern so I can replicate another header. If this works out okay, I should
be able to have others made... Any takers if this works out?...

Jerry

--- In ipcrc@yahoogroups.com, "revconprince" <daveinet@...> wrote:
>
> http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=466
>
> Longer intake runners get tricky on a throttle body. Reason is, you have to
keep the velocity up at low RPMs to keep the fuel mixed in the air. Dry intake
runners are little easier with port FI is simpler.
>
> --- In ipcrc@yahoogroups.com, "douglasvanb" <douglas.vanbossuyt@> wrote:
>
> >
> > Putting loops in the intake pipes between the throttle bodies and the
cylinders seems like it could cause interesting problems with slowing down the
air flow and delaminarizing it (straight-ish pipes like those found in cars
would tend to make the airflow become more laminar, assuming a uniform-ish
flow). Would it have the same effect if I increased the diameter of those tubes
for part of the way but kept them as straight as possible? Theoretically, I
think it would but that also might create strange harmonics with the shock waves
as the propagate back and forth through that non-uniform-diameter volume. Does
anyone have some suggested-reading links on this topic? I'm not too familiar
with the nitty gritty of using shock waves to pressurize cylinders.
>