SEDave

My S3 now has 171K miles on it with the original 680cc injectors. I've been looking at RCEng.com recently and have been wondering if I should get their 750cc peak-hold injectors or have them clean the old ones(I'm going to replace the fuel pump either way). Eventually, the motor will need a rebuild and receive a street port job and I will be getting a Corksport header soon(already have a K&N cone and custom exhaust). Are the stock injectors close to being maxed out at high rpms or do they have room to spare? Also, if I do decide to get new RC injectors, what style would I use...Bosch, Denso, or Honda(probably not)? Thanks for your time, David.

j9fd3s

if you're gonna be flowing more air i'd get the 750's... denso style

SEDave

Thank ya.

j9fd3s

stock ecu seems to limit duty cycle, so bigger injectors are good

SEDave

Well, I got bored and went ahead and installed the 2 RC 750cc injectors I got a awhile back to see what they would do(the motor's internals are still stock). Wow, what a difference in power and smoothness from the midrange and top end. Although there is a negative, the idle is now poor...like the idle mixture is rich( of course). I've had to retard the lead timing greatly to get it to keep from stalling and adjust the idle speed to no lower to 1K. How effective is the variable resistor at changing the idle mixture? I've set it to all-the-way lean and it still idled like ****. All-the-way rich made it run worse and no setting in between helped. I should get a wideband a/f gauge to diagnose but don't have the money right now. Is there any other way to mess with the idle mixture? I'll probably end up putting the old dirty injectors back in until I tear apart the engine if I can't sort out the idle.



Also, will the intake air temp sensor from a NA S4 work on a S3 if I make an adapter for the electrical connector?

j9fd3s

yep