My injectors were going bad so I replaced them not long ago with some 24# injectors from Accel because I found it cheaper to get these than to replace them with stock 22# injectors. Now my car is running rich and surges at idle sometimes. My car has SD and I know the best solution is to burn a chip. However, I don't have the equipment or the money to get one made at this time. What I do have is an AFPR that I haven't installed yet. What would be the ideal fuel pressure to run with these injectors? I have read many times on this board that pressure should be lowered to accomodate larger injectors. This does not make sense to me. If people increase fuel pressure with smaller injectors for better atomization, wouldn't a larger injector require a higher increase in pressure for ideal atomization?

 

You guys have alot more experience than I do. I know someone here can help me out.

 

yes ,higher pressure causes a better fuel spray pattern but you still have to be able to use that fuel.you would want to turn down your pressure to avoid a rich condition.you really need a scanner to see whats going on.once the car go's into closed loop as with the stock chip being slightly rich in the first place you are most likely now very rich especally at idle.you might have exceded the range of the ecm to compensate.you can try lower pressure as a quick fix,but you really need a chip burnt for your combo to get it closer.
if you think of your chip burning equipment as performance parts it is most likely the best bang for the buck you can get!
pete

 

1LE, I had the very same problem (car running way too rich) and I tried to lower my fuel pressure to get the BLM/INTs back to 128/128. I couldn't get my fuel pressure low enough without affecting the way my engine ran (fuel pressure got too low for the engine to run right, but not low enough to fix the overly rich condition).

The only solution was to get a new eprom, and decided to learn to burn them myself (since I was planning on getting a Miniram in the not too distant future).

The fix is really quite simple, I just increased the size of the Injector Constant in the eprom to get most of my readings as close to 128/128 as I could by this simple change. Then, as I learnt more, I then slowly "fine tuned" the VE tables so I was ALWAYS getting 128/128.

I would expect that if you were to get a "custom prom" burnt for you, the person would probably do what I initially did (just increase the Injector Constant in the eprom) to try and get you as close to 128/128 on as often as possible for most Load/RPM situations - but they will not probably not "fine tune" the VE tables as that requires a LOT of data, analysis and time to do properly. If you had to pay someone to do this, you'd probably have to spend $1,000 (or more). Now you know why I say that a "custom eprom" written by someone else can NEVER be as good as an eprom that you burn yourself cause no one will spend the time necessary, except the actual owner of the car.

 

I see. It looks like I need to get some prom burning equipment ASAP. Thanks for the help guys.

 

Please do. The change to the Injector Constant takes about 5 seconds and to reburn it about another 30 seconds. That will get you a heck of a lot closer than you are now and you'll probably notice an increase in power since you are probably overly rich.

Then, I can direct you to a post on the DIY Prom Board regarding "tuning of the VE Tables" that you can take you time to play with. Just take it "one step at a time" in the beginning and as you build your knowledge (and experience) you'll become a lot faster and make "bigger changes". But initally, you should make only small changes anyway so you can also learn how to "recognize the effects" when you hook up the scan tool.

 

What increment should you bump the injector constant by? I have 22# stock injectors that have a constant of 24.1. But I heard the 24# SVO are much higher then that 24. What do you recommend as a starting point?