S-AFC, 450cc injectors on a 420A.

cjmech · 01-11-2003, 07:58 PM

Does this allow you to boost the 420A without throwing a code or do you still need the missing link?

Have you done this?
What were your results?

cj

98Turbbo420A · 01-11-2003, 10:07 PM

Using the missing link, you shouldn't throw a code at all.........I Don't really think it matters how much you are boosting, but the 450CC's and the AFC will help...naturally your next problem is ignition. What have you got for that?

cjmech · 01-12-2003, 12:44 AM

I havnt done anything to the motor yet I just got it a few weeks ago, but I was curious as to wether or not the DSM N/T's would allow you to boost the factory map letting the PCM control fuel and ignition while running factory fuel psi. This is the same method I used on my old school CRX, I could boost up to about 11psi (no missing link) before it would throw a code for the map, so I was curious if it would work the same way.

Cj

Strauss · 01-12-2003, 07:20 AM

Well, if you have a 95 like me than you will not need an FCD(missing link). Now, you can run 450cc injectors with the S-AFC, but there is a hitch. You will need a good rising rate FPR(vortech S-FMU is the best) so you can lower your idle fuel pressures down to about 25psi or so. If you don't do this and use the AFC to compensate for the extra fuel at your low throttle settings, the car advances the #### outta the timimg because of the low voltage it's reading fron the now fooled MAP sensor. So yes, the AFC will screw with the timing, but usually it only happens under your low settings because that is where you need to lean the car out the most. So in other words, the more you lean it, the more timimg advance you will get. So, the most common way around it is to run LOW idle fuel pressure with a large rising rate disk.....that way you won't have to lean the AFC down heavy just to make the car idle, and you will have proper boosted fuel pressures........a datalogger is a great tool once you start moving up in injector size

siueclipse · 01-12-2003, 10:05 AM

HAHN told me that its not good to run anything higher than 310cc injectors on the 420a. They say the engine wont run right.

Quote:

310cc is a good choice because it's less than 50% larger than the stocker, hence controllable by teh stock ecu at idle, and it's also a fairly common injector. And with that size injector, at 9 psi, you'll only need about 70-75 psi of fuel pressure to adequately fuel your car at boost, which is much more reasonable a figure. You'll need a high impedance saturated injector...not low impedance peak and hold. Also, you'll want to turn the fuel pressure down at idle. I recommend somewhere in the 30-40 psi range. It would halp to have a datalogger handy so you could check your fuel trims at idle (you want to be close to 0-5%).

98Turbbo420A · 01-12-2003, 11:10 AM

Quote:

HAHN told me that its not good to run anything higher than 310cc injectors on the 420a. They say the engine wont run right.

I'm assuming they meant on there stage 2 system?

I apoligize I keep forgetting that the 95-96 420A's use an OBD1 system while the 97-99 use the OBD2......sometimes I wish I had an OBD1, it's much easier to tune.

cjmech · 01-12-2003, 12:06 PM

I believe my RS to be obd II. It has the diagnostic port for it under the dash just to the left of the center console.

How is everyone accomplishing the datalogging? What all do I need pn#'s, prices ect...

Thanks,

Cj

Kirby · 01-13-2003, 06:35 PM

Go to www.obd-2.com you will need the cable ($125 or so) and a laptop to use it with. As far as HRC saying only 310, that is correct if you want the ECU to control them. You can go as big as you want with the proper equipment to tune it. IE sfmu, afc, 8 injector setup. You will always need to use a missing link to control the map sensor on this car. Odds are your crx was obd1, like our 95's so you didn't need it. But don't you feel much cooler behind the wheel of a sexy car?