Injectors

[BoostedGS]

Well, I'm getting better at launching my car. A little bit of clutch slip helps a lot. So we'll have to run when you get back.

But I won't be racing too much until I get bigger injectors. Now that I have the SAFC in the car, I discovered that my injectors can't provide the fuel I need. I added fuel at the higher rpm's and my egt's still scream towards 1600 at WOT by 3rd gear.

So as soon as I scrape the money together, I'm gonna order some 550cc injectors. Why couldn't those damn engineers at Chrysler use the same fuel rail for my car so I can throw some stock 450's from a 4g63 in??!!

Patrick - the tires aren't my fault, talk to Rob about that one! ;)

[303Racing]

550cc is too big for the afc. You run hella rich even at 50% lean. the largest you can go without a dfi or a standalone is 440cc. And these should be more than enough for you w/ the s-afc. You will still be rich w/ the 440cc but no where near as rich as the 550cc are.

[hoffman]

the car was datalogged and when you apply the formula to figure out the injector size needed it came out to 550cc.

the car is running so lean right now its almost dangerous.

[303Racing]

<sighs> ok.

The math may tell you what size you need but the ECU on the 420a will not let you run them. (I haven't seen a successful one yet) You have to get a standalone or a piggyback like the DFI to run 550cc or higher.

Like I said, 440cc and the S-AFC should be fine for what you are after now. (On stock internals)

Feel free to try it, it may work. But remember the math is one thing and the stupid POS mopar ECU in another. I'm not getting the DFI for nothing.

Don't get me wrong I am not trying to argue, I am just trying to help you out. I spend WAY too much time reading anything and everything about the 420a. And even more time trying to make my car be on of the fastest 2gnts in the country. I have talked to HRC about this and I have read many posts on the topic. I just dont think it is going to work. But like I said maybe you will get it to and then I can copy what ever you did to make it work:-)

[BoostedGS]

True, 440cc injectors will with the SAFC will work fine for my current setup (stock internals). But I will be upgrading my internals before the end of the year. I don't want to buy injectors twice this year.

Maybe I'll give the boys at HRC a call and get their input.

Thanks,
Patrick

[hoffman]

post the links to this stuff. you have peaked my interest now.

i wasn't trying to start an argument either, i only had information on one side of the problem. so if we could all see the differnent sides of the problem maybe we could come up with a better solution.

[303Racing]

I stand corrected in a way. You can run 550cc w/ the afc, but you need a s-fmu to lower you base fp ALOT. Don’t know what to though. It may also have to do something w/ peak and hold and saturated injectors. (I know how they work but I don’t know how you would decide which ones to go w/)


440cc w/ afc will be enough for 15-18psi boost. I know you already know this but you can always force feed (turn up the fpr) the injectors. Even w/ the 440cc I couldn't see you running into the 100+ psi on your fuel system that you run now. I only know one guy that is running 550cc injectors and an S-AFC. But I don’t know if it is a peak and hold or saturated that he is using. My understanding is that you may be able to run 625cc saturated w/ and s-afc and be more than fine. (But I have no solid evidence as of yet and I don't want to be the one who tries it first)

I have posted on a ton of boards and e-mail lists trying to find out if I could run 550cc or 625cc and s-afc only. I didn't get back any encouraging feedback. I know there are alot of guys running 440cc and the s-afc fine and boosting 15-18psi

I think the problem w/ the 550cc is going to be your idle. At max boost it should be fine - that is what the math says to use. So, to keep it from being too rich at idle you will have to lower you base fp. To what I don’t know?

I to am VERY curious about all this injector crap. I have just been reading alot (not all at once, but over three years) about 550cc being too rich at idle even w/ the s-afc leaned out 50%. I wasn't trying to tell you that you were wrong. I was just trying to point out what I have read over the past three years or so. I just wish it was as easy for us (420a) as it is for you guys (4g63)


I could have been clearer about the rich part. The 550cc and s-afc is fine and dandy until you get to the stop light. It is just rich at idle.

If you did get the 550cc and it was too rich all you would have to do is sell the s-afc and get a dfi. Then you could boost 25+ like me:-)

When you use an AFC, it only modifies the stock fuel map by a percentage of +/- 50%. The issue would be less so at wot but at idle and low boost/off boost around town driving. I think getting the car to start would be the biggest issue though. The fuel pressure that would be necessary to get these things to idle would not be very pretty.

The reason for using a stand alone fuel system is it allows for new maps properly written for large injectors that are far more accurate being peak and hold which allows stock fuel pressure and full derivability. And that is what I am after (daily derivability)

I just wish I had more time and money to do all the testing and tuning to truly find out what is capable or not. That is why I am just going w/ 625cc and the DFI. I like you, don’t want to buy injectors and have them not work.

If you guys end up trying it let me know how it goes. I will have my car up and running in a few weeks or so. I would be able to drive down to the springs and see how it works.

I am very curious to see how it all works out.

[BoostedGS]

I just got off the phone with one of the techs at RC Engineering. He told me that the ECU for the 420A requires "high resistance" injectors, where the 4g63 requires "low resistance."

The largest high resistance injector they sell is a 440cc, which is good to about 300hp at the wheels. Once you go above that, you'll be buying low resistance injectors and will require a piggyback system, which he said and I quote "costs and arm and a leg!"

So, I think I'll be going with the 440cc injectors and the S-AFC, for now. Hopefully I'll be able to tweak the S-AFC and the FPR to make the car idle and boost correctly. Even with the stock injectors, sometimes I have to crank my car for a few seconds before it starts.

Speaking of base fuel pressure, did you follow the HRC manual when you set your base and boost fuel pressure?? According to the manual, for 6-9psi the base fuel pressure is supposed to be between 47-55psi, and under boost it should be between 105-115psi!!! Is that really true, becuase everyone hits the ceiling when I tell them that.

Patrick

[hoffman]

open up a new thread on NT injectors so we can keep the facts straight and stay on topic.

[DSMxTSi]

Or you guys could just sell your cars and get an AWD 4G63! :p j/k I can't wait to see what you two run this year, it'll be fun indeed. But if you're serious about going fast, Patrick, then save up for a stand alone when you get the motor rebuilt later, that'll be the only way for you get where you want to be. Just remember that both of you will have a hard time keeping up with Dave, Hal, myself, etc! :p

[303Racing]

Yourself, hahahahaha. You better get wrench'n on that bad boy Cody. I think there will be some good races this summer though. You know I'm out to brake down some barriers.

All I can say is bring in on....


Patrick,

You shouldn't have any problem w/ that set up. Like I said there are a lot of guys running it w/ no problems. The only other thing you might want to get is the Vortech S-FMU. It is pricey but it is far better than the HRC POS.

The fuel psi is high because the kit doesn't come w/ larger injectors. Force feeding them sucks because you go into those high ass fuel pressures. But w/ the 440cc you wont be anywhere near those #'s. You will be able to boost 15-17lbs w/ the 440cc and S-AFC and built internals.

I am going to run the 625cc or 725cc w/ the DFI (piggyback)
gen 6 DFI is 1100.00 from HRC (cost Both arms and both legs)