injector placement.

[travellinbob]

hi everyone, I was talking to a mate this morning in oz and was discusing my intended set up. 12a, t04(came yesterday:D ) side draft carby(hopefully 48mm) but maybe converting the carby to use fuel injection. Cheap way to get throttle body, perhaps. So anyway we were talking about where best to place 4 injectors. I thought 2 on top of converted carby and 2 further along on the top of the side draft manifold. He said that a few guys he knew of were putting injectors on the inlet side of the butterfly valves in the throttle body. And that this whilst hampered fuel economy, aided fuel cooling. I have no idea and am a relative novice so any help would be appreciated.
 Oh i also want to run an intercooler.
 And yes this is a budget build.



p.s. nice to be let out of the old skool section once and a while.:rollin

[travellinbob]

me again, actually I think it was mor along the lines of fuel atomisation rather than cooling. Sorry to confuse.

[MikeLMR]

I think it does help with atomisation, I seem to recall a big writeup about this in the old CCC magazine about 4 years ago (car and car conversions) and they were running injector tests with the injectors actually before the bell mouth intake of the throttle body ... in fact just like this

[bill shurvinton]

Its a compromise (as is everything) The higher up you go, the better the atomisation and cooling of the fuel charge, but the worse your economy and throttle response.

Port injection gives best economy and response, but with a small loss of power.

Just after the throttle plates in an IR setup is about the best compromise unless you are doing 12000 RPM...However

For a turbo you actually want some of the fuel in as early as possible. Ideally just before the turbo so you cool the intake charge as it is being compressed. This (and especially with a tad of water injection) allows you to ditch that hunk of worthless bling called an intercooler and instead focus on optimising the inlet path for maximum flow.