allentownS4

I've been STFA and have found a lot of information I believe to be useful. That said, it seems that over time there have been a lot of changes in theories and ideas surrounding which injectors are "best", to the point where single members have posts over the span of 3 years claiming different injectors to be better.

Here's what I've found so far, maybe you can give me some clarification, or at least confirm that I am on the right path:

- RS4 injectors have the best flow pattern and idle characteristics, but they cost 2x-3x more than other options and do not have the ability to flow as much.

- "Greentops" were considered the "best" for awhile, but this has been reconsidered over time due to rough idle and cold start issues (hence the reason AWE stopped using them for their Stg3 kit; BTW, I couldn't find an answer as to what they use now).

- "Bluetops" seem to be the injector of choice these days. They have the capability to flow more fuel than the RS4 injectors, cost about 1/3, and have stock-like idle and cold start properties.

Am I on the right track? TIA :-)

PSmalls::DoggieStyle

RS4s were the 1st real option out there so many considered that the best. Then, Greentops and Bluetops came along as an option and both were considered very good options. Now, there are 38# and 42# Delphi injectors along with 60# Seimens injectors that are all good options as well.

FWIW, Bluetop injectors (36#) are smaller than RS4s. However, most run them at over the stock 4bar fuel pressure so actual flow is slightly more than RS4 injectors @ stock 4bar pressure. The same goes for 38# Delphi injectors, which are smaller than RS4s, but will flow more at a higher pressure (BTW, I run the 38# Delphis @ 4.7bar which is ~500cc/min). You can also run the RS4 injectors at higher pressure to get more flow, but obviously the downfall with regards to RS4 injectors is the price. 42# injectors (Greentops and Delphis) are probably the most commmon way to go because they flow ~510cc/min @ stock 4bar fuel pressure. I've heard that the Delphis are better with regards to drivability (idle/part throttle), but many have very minor drivability issues (a couple random idle misfires for example) with 42# Greentops...which are by far the most commonly used injector in a homebrew setup due to their abundance and price. Once you move on to bigger turbos and higher boost levels that require more fuel, there is the option of running 60# Seimens injectors at lower than stock fuel pressure. Not many have experimented with this thus far, but a few have (Mike2KS4 mostly). As in other aspects of life, as time goes on and we evolve new options become available/known so keep your eyes and ears open.

Here is a breakdown of the injector flow rates:

36# bluetops (~380cc @ 3bar, ~440cc @ 4bar, ~488cc @ 5bar)

38# Delphis (~400cc @ 3bar, ~460 @ 4bar, [me: ~500cc @ 4.7bar], ~515cc @ 5bar)

42# Greentops/Delphis (~440cc @ 3bar, ~510cc @ 4bar, ~570cc @ 5bar)

60# Seimens (~575cc @ 2.5bar, ~600cc @ 2.75bar, [IIRC, Mike2kS4: ~6100cc @ 2.8bar], ~630cc @ 3bar)

Disclaimer: All flow rates above are rough estimates done with a calculator assuming the LB rating is accurate. Some numbers will vary due to LB ratings being rounded to closest whole #.
Hope this helps, sorry for typing so much. ;-)

allentownS4

too many opposing and conflicting comments.

Anyway, so just to verify, if I get a set of the 42# Greentop/Delphis injectors, I can run them in a stage 3 setup without the need for a FPR (i.e., stock fuel pressure)?

Thanks again.

PSmalls::DoggieStyle

However, it may not be enough fuel for cars running bigger turbos (hybrid K04s or GT)...in which case you can either increase fuel pressure or move up to a bigger injector.