I have the current modifications: Ported intake with slp runners, ford svo 24 lb injectors, AFPR set at 43.5psi, AFR 190's heads, TES headers, flowmaster cat back system, and a paxton sn2000. I am currnetly not running my supercharger because i am breaking in the motor. I have been looking at burning my own chip, but my question is .....Are the 24lb injectors too big? my tail pipes are alway showing black as the plugs too? I set my fuel psi to stock and it seems to make no difference? I wonder if anyone else has this problem? I had to replace two cat's as a result of running too rich. I set my FMU on the supercharger from 8\1 to 6\1 ... but i am not running it now.?

My question on this board reguarding the larger 24lb injectors is will i be able to control the amount of fuel with the prom burning kit and how easy is it to do this? Also, is there any danger of running to lean? What can I do to monitor my car so it will not go lean? I have the 386 laptop and the Craig Moates software?

 

24s to big with a S/C?
How much boost?
24 are hardly any different from stock.
I'd suggest you start with running a search and reading thru the final answer series of posts.

FMUs are for those trying to patch a system together. With the right calibration, and proper sizing of components there is no need for them.

Too Lean will kill any engine N/A or S/C
S/C eats lots of parts when too lean

EGT guage and Wide Band O2 sensor will help.

 

If you have not let the eprom know that you are running larger injectors, then the ECM is going to calculate your fuel mixture too rich. 24# SVOs @ 43.5 psi is like 26.5#. If the eprom is a stock 350s, then you are running 20% too rich - until the MAF maxes (I believe you are running a MAF system). Then, once the MAF maxes, the ECM will stop making any further fuel corrections (based on MAF readings) and you will start to run leaner (unless you are correcting via the "PE %Change AF Ratio vs RPM" Table).

You need the eprom changed to reflect the fact that your injectors are flowing similar to 26.5# injectors. Then, once you max the MAF, you will need to add more fuel via the "PE %Change AF Ratio vs RPM" Table. But you must ensure that you are in PE when the MAF maxes and NOT in PE when the MAF is not max. This is why tuning either the MAF 165 (or SD 7730) difficult for "power adders" and the BEST ECM is the 7749 used on Turbo SyTy.

The FMU will help with you "boost" situation, but are you adding too much or not enough? If you wish to retain the FMU and try to make the MAF 165 work when in "non boost" situations, you need a WB O2 Sensor. The WB will allow you to get the mixture right when you are in a boost situation AND the MAF is maxed. With careful analysis and determining the proper "trigger point" (the RPM level where your MAF is > 255) for your %TPS to engage PE, you should be able to get the mixture reasonably close for this situation.

I am helping another friend that has a virtually identical setup and this is some of things we are doing. We are trying to "salvage" the MAF 165 but I have already "warned" my friend that he should be prepared to convert to the Turbo SyTy's 7749 ECM as it is designed to work with a 2 Bar MAP and handle boost situations properly. Life is so much easier when you work with an ECM designed to work in "boost situations" than working with an ECM designed for a Naturally Aspirated engine.

But for either situation, you really should get a WB O2 sensor. Not only to maximize power, but more importantly, to ensure that you are not running too lean.

 

Glenn, I read an article in CHP about superchargers and thridgens. The chevy stock 22lb injectors can not withstand the added psi of the FMU and go static at about 80-90psi. The article also stated that a 10% increase in the fuel injector size is the max you can upgrade your fuel injector size before you need a custom prom. The ford SVO's can handle the added psi of an fmu... that is why i added these about 2 years ago. I will email you/PM and plan on giving you a call either this week or next. Got a lot going on....fixing a blown head gasket, so I'm doing both sides.. And my wife is due in 1 week and 2 dayss So i gotta get the car done before the baby comes! If i finish by tomorrow, I'll give you a call.

 

I would say that those 24# ford inj are way too much. I am running 24# GM inj. when I was driving to chicago every day 200+ miles a day I had a stock 350 chip and my psi was at 50. I never had a problem but, when I got a job less than 2 miles from my house my car could not compesate and I went through two sets of plugs in two mounths I even put my psi back to stock no help till I changed the chip to calculate for 24# inj. then It quit foiling out plugs. but, I still have tons to do. I am waiting till summer. It is well worth the time to burn your own.

 

I've had good luck with running 24#SVO in a mild MAF 305 even. Should be no problem if you set up the PROM right. Just dial in the FI constant to start.

If you think you'll max out the MAF (wish I could so I could try this)...never mind, I've been slapped down before on this one...well, you could run with a bypass tube and 'lie' to the ECM about your FI size. If you do it right, it should work. Granted, there will be nonlinearities in the MAF rate compared to the reading, but with a little MAF scalar tuning you could be dead-on.

I'm sure someone else can expound upon this, either pro or con. Just like letting a slip-stream of your A/F mixture run 'blind'. Sort of like a virtual MAP system, no?

 

Craig, I have speed density...any difference in your reply reguarding the 24lb injectors?

 

CHP is incorrect. And frankly, they know dick about EFI systems IMO. Have you ever seen ANY of these magazines do an article on burning your own eproms? Heck no. So how in the hell can they make statements of "what the ECM can and cannot do" when they don't even know how to burn an eprom?

You ALWAYS should have the eprom redone for ANY change in injector size. In fact, typically the stock GM eproms on ALL cars tends to be on the rich size as is. Most guys with basically stock engines find themselves pulling up to 20% of the fuel out that is how overly rich the programming is. Further, how is the ECM going to know how to properly meter the fuel if the eprom thinks you have one size (22#) yet you are using another (SVO 24# @ 43.5 psi = 26.5#).

If your using SD, there are even more challenges with a Supercharger. The MAP sensor readings are greatly influenced by the supercharger. In part-throttle the ECM can help but you really need an SD system designed around a 2 bar MAP plain and simple.

Yes, with a LOT of tuning you will be able to kludge a 1 Bar MAP SD system - adding fuel via the PE tables to compensate. But SCs have so many points where you max the 1 BAR Map Sensor where you won't necessarily be in PE. You end up having to engage PE at a very low TPS reading, monitor your WB O2 sensor readings and play with the amount of extra fuel you need to add (or possibly subtract because the FMU is also affecting the fuel).

The real solution is converting to the SyTy's 7749 ECM/Eprom at this time. You could "kludge" a 2 Bar MAP sensor onto the 7730, but there are too many trade offs. Until someone re-writes the 7730 code to make it work "plug 'n play" with a 2 Bar MAP so it behaves at the same low KPA levels as a 1 Bar MAP, and extends the range to handle 200 Kpa, the 7749 is still the BEST answer.

 

So what will i have to change to use the different ECM Turbo SyTy's 7749 ECM ? And how much will it cost? I was actually thinking of getting the ZIF socket from Craig Moates and burning one chip for normally aspirated and another chip for supercharged. What will the trade offs be if i use my stock ecm and deal with modifying the kludge? Also, I have a kit for my fmu to change the ratios from 4\1, 6\1, 8\1, 10\1, and 12\1. I currently have the 8\1. Thanks for the help!

 

Let's say i get the ECM Turbo SyTy's 7749 ECM. Will I be able to run my car normally aspirated as well as supercharged?

 

The 24# Ford SVO injectors aren't too big if you have an engine capable of maxing out the MAF sensor. I'm running these injectors in my 355 and am hitting injector duty cycles in the mid to high 70% range at WOT and am just maxing out the MAF at 5800 rpm. The stock 22# injectors could only handle this amount of fuel flow by cranking up the fuel pressure by several psi or so.

The problem you had was running too large of injectors w/out telling the computer that, so it was assuming you had stock injectors, hence dumping in way too much fuel. :nono: Even the GM 24# injectors are a little too big for the computer to compensate for with the fuel pressure jacked up too high.

 

When you say 43.5 psi is this with the vaccum hose off the fuel pressure regulator or is this with it on?