Abubaca

iTrader: (3)

Hello all DIY PROM guys!

I have a favor to ask. For anyone who's spent much time lately on the TPI board, there's numerous questions and discussions with regards to fuel injectors. Several of which have to do with the ever popular Ford/SVO/Bosch injectors, and several have to do with how to tune for bigger injectors.

I am installing a set of 24# SVO/Ford/Bosch injectors this weekend, and I intend to measure and photograph all the minor differences and write up an all inclusive sticky. Along with this, I'd like to explain why I can't simply turn down the fuel pressure on my AFPR to compensate for the 2# increase over my 22# stock multecs.

I personally understand for the most part why a tune is needed, but I don't feel comfortable writing an explanation that may (or may not) be etched in "TGO Sticky" stone so to speak.

Can someone here please write up a simple paragraph (in lamens terms) why hacks and tricks are NOT the proper way to do this, and why a tune is necessary?????

Thanks guys.

DENN_SHAH

iTrader: (1)

im not sure if this is what your looking for, but here is my 2 cents on it.
im sure other people can expand on this even more.

why putting in bigger injectors & not making other changes is bad.
without changing any thing other than the injectors the motor will run rich.
the ECM will still be injecting fuel thinking it has the smaller injectors.
based on what it sees from the O2 sensor, the ECM will start pulling fuel until it reaches its lean limit. now it starts kicking code 45, always rich. im not sure about these older ECMs, but some of the newer PCMs will kick the BLM & INT back up to what should be the normal amount of fuel after a few minutes & then it starts the process over again.
with it too rich, you have excessive unburned fuel in the cylinders, most of which goes out the exhaust. it also washes the oil off the cylinder walls leading to increased wear. some of the unburned fuel gets past the rings into the crankcase & dilutes the oil adding to even more increased wear. soon you have a low mileage worn out motor that never ran as good as it should have & used way more gas than it should have & its pumping clouds of oil smoke out the tail pipe. you also have killed your cat & polluted my air, thank you very much


why just turning down the fuel pressure after installing bigger injectors is bad.
turning the fuel pressure down will help, but the fuel won't atomize as good at the lower fuel pressure. atomization is key, liquid fuel will not burn. the better you can atomize the fuel, the more power you can get from each gallon. poor atomization means you have to add more fuel so the motor doesn't have a lean miss. now your back to having excessive unburned fuel in the cylinders washing the protective oil off & contaminating your oil & wearing out your motor, again your killing your cat & polluting my air, thank you again

Orr89RocZ

iTrader: (20)

pretty much hit the nail on the head. To add, stock pressure is like 42-43 psi. to make a 24lb injector act like a 22 lb injector, you'd need to run roughly 36 psi.


Now this may work ok, but its best to keep some pressure for atomization. Another thing to consider, is that MOST factory tunes are alittle rich. So adding a larger injector without telling the ecm will cause it to run abit richer than it was before, so now its even MORE rich than stock which is not good It all depends tho, not all cars run the same. My car was on the rich side stock, and adding a higher flowing manifold really helped lean it out to make some good power without a tune

Abubaca

iTrader: (3)

Thanks guys.

I'm gonna see how this thread develops in the next few days before I do a write up, but I think you guys pretty much explained the part I didn't grasp. The pulling fuel based on the o2 part of the equation was pretty much what I wasn't sure about. It makes sense, but I wanted to KNOW before I started telling other people.

JP86SS

iTrader: (1)

Another view on the injector size.
The ECM has values to compensate for how long it takes to open the injectors, Its also calculating how long to keep it open for the proper amount of fuel to make the commanded AFR.
If the actual amount of fuel dispensed is more than the calculation expects then the next thing is the o2 sensor indicates the mixture is too rich and the pulse width is reduced. So you see each time a calculation is made it is consequently reduced (after the fact). That in itself is leading for trouble

With this in mind we look at adjusting fuel tables to correct for it.
Now you have a good running car when cold and really sucky when warm, accelleration bogs, lean pops, all the fun things that come with fuel being calculated on percentages that are incorrect because of the injector size.
Its a chase your tail situation if the injector change is rather large.

Make the "correct" hardware match the software configuration parameters and tuning will be the easiest because you can "go by the numbers" when figuring complex issues out. By correct I mean operating at its rating, proper adjustment, or best efficiency (no vacuum leaks, etc).
Having fuel dribble out of a large injector obviously is not going to be good for the operation.
The myiad of combined setting for tuning is difficult enough to keep under control, trying to figure fudge factors on top of that is just not the way to Get-R-Done.

pandin

Abubaca's M9593-a302 24# injectors

From the Bosch calibration sheet:

Target Injection Pressure = 39.15 psid"

This is 24#/hr at 39.15# Fuel line pressure.

I don't mean to start a bunch of ---- But I find it hard to believe that Bosch would put out false info.

Abubaca

iTrader: (3)

Pandin,
You're suggesting that because they're rated at a lower pressure than our car's stock fuel pressure, the 24# injectors are pretty darn close to actually flowing 22#, correct? If that's not what you're saying, by all means correct me.

OK, here's my issue with TGO, and the entire reason I want to write up this tech/sticky:

Your logic makes sense, and I don't doubt the information you've found. But as a self admitted NON expert, I research just about everything I do to my car. What I've found, and I've read this on some Ford forums too, is that it's easy to find information showing the Ford injectors as rated with a lower pressure. BUT, in reality, the guys with the wrenches and laptops show that in fact they're pretty darn close to 24# at our factory fuel pressure. They show that a tune is ultimately required.

I don't know how much difference a few pounds of pressure makes. I don't. I also don't know if maybe the Bosch/Ford rating is simply rated lower for some political type thing like GM underating HP levels. I DON'T KNOW. All I can do is to see what people are actually doing. And EVERY time I do, I find that no matter how many people bring up the lower pressure rating, in the real world, it seems these injectors are no different than any others.

I'm trying to help myself, and help others not have to go through all the research and troubleshooting. I know you and I have discussed this in other injector threads, and I'm 100% onboard with your logic and info. -BUT as stated, for whatever reason, it seems that your point, which I AGREE with, just doesn't seem to be good advice. I'm TOTALLY willing to look at other evidence, but like I said, what I've found shows it not to be right.

Abubaca

iTrader: (3)

Just to clarify my saying "This is what I don't like about TGO"

.....there's SO much conflicting info on TGO regarding technical things like this. It's hard sometimes to sift through it all and get a straight answer. The whole point of my write up will be to EXPLAIN the differences, and WHY one method is correct, even if some info shows otherwise.

.....and by all means, if we can determine that IN FACT, 24# Ford injectors DO NOT NEED additional computer tuning, then that's what I'll report. But so far no one has been able to show that they are different, even though on paper, there is evidence.

Orr89RocZ

iTrader: (20)

Fuel injector flow math for pressures

New flow lb/hr rating = old flow lb/hr rating * (squareroot (new pressure/old starting pressure))

Say you have 24lbs injectors rated at 39 psi. That injector will flow 24lbs in an hr at 39psi. What if you change it to run 43 psi?

New flow will be = 24 lb/hr * (squareroot ( 43psi/39psi))
= 25.2lbs/hr


MORE pressure means more flow, and likewise the opposite.


By all means the car will still run on 24lb injectors if the ecm still thinks its 22's as programmed in the computer. It will be richer than it was before. How much will the ecm try to compensate by reducing pulse width and such? I'm not sure.

Tuning still should be used as there is a good bit to gain even on BONE stock engines on stock tunes

Blown87IROC

It seems to me you are in a perfect position to do some real world testing that could provide a difinitive answer to this. All you have to do is some data logging. I would reset the ECM then log your current configuration. Next, install the new injectors, reset the ECM and log trying to replicate the previous logging conditions. Then, adjust fuel pressure and repeat the process once more. Hopefully you have logging capabilities--a good thing for everyone who wrenches on their own car. Have fun!

Orr89RocZ

iTrader: (20)

I just found out some info on BOSCH

I believe they make the Ford injectors which are generally rated at 39psi as thats what ford uses apparently. Since they are made for ford they are advertised at ford pressure, so in fact on our cars, they will flow 1.05 times MORE than what they are rated at apparently. Most injector companies use 43-44 psi tho. I believe bosch will give rates for both 39 and 43.5 psi

pandin

All my intentions are to have a good start on the "paper numbers".

I am a firm believer in following the "paper numbers" till proven wrong by (real world facts).

Any Interpretation by anyone who knows what all this means will be appreciated by all TGO members.

The Calibration sheet






Pressure ----Multiplier
50.03---------- 1.1289
54.96---------- 1.1869
60.03-----------1.2427


FNPW_BKCOMP
Pressure ----Multiplier


VBAT---- Voltage Offset
15---------------- 0.462




FNPW_OFFCOMP
Pressure--- Multiplier


ALOSL "low" injector slope
FNPW_OFFCOMP Multiplier on FNPW_OFFSET as a function of injection pressure in psid"


This is copied from a pdf file from the Ford motor sports web site.

All credit is given to the original authors.

pandin

From Stan Weiss's flow charts this injector should flow 24#/hr, 252.2 cc/min, or 181.4 gr/min. No fuel line pressure is given so how about 39.15#????

This would be the injector constant to start with, only if AFPR is set to 39.15# at what? Idle or No vacuum?

Orr89RocZ

iTrader: (20)

i would set the injector constant to what the injector is advertised as ONLY if your fuel pressure is what the injector was rated at.

If its 24lbs at 39psi, run 39psi and make the injector constant 24. If you run stock 43.5 psi or so, then change your injector constant to match which looks to be 24*1.05, or 25.2

Abubaca

iTrader: (3)

I agree with what Pandin is saying. ...and I agree with Orr89rocz in that you should actually set your constant higher if you run higher pressure than the rated 39.

....but all I've read on here by those who've done this show that the injectors flow 24# AT STOCK GM FUEL PRESSURE. Yes, I know this conflicts with what the Bosch/Ford numbers show. ...and even those who didn't actually test the injectors have showed that they perform perfectly, and as expected when the constant is set at 24, and they're run at 42.5 (or whatever the stock FP is). I've also talked to a local guy who does proffesional tuning and he just kinda chuckled when I mentioned this rating difference, and he said that he uses 24 as the constant with 24# Ford injectors, and not to worry about it.

I dunno, I'm just reporting what I'm finding.
----------
check out the fuel pressure multipliers in Pandin's chart. What's the difference between LSComp and BKComp.

One would suggest there's quite a difference in the pressure rating, one suggests there isn't.

Abubaca

iTrader: (3)

OK, in searching for the "proof" that the 24# injectors flowed 24# at stock GM fuel pressure, which I KNOW I read the other day.....

....I came across evidence to the contrary. Jim85Iroc was selling his 24# pounders that he bought with the flow chart. Numbers were as follows:
Flow numbers @ 43.5psi
27.24
26.86
27.14
26.86
27.14
27.43
27.33
26.86

Well, at least at the moment, I think I'm gonna shoot for 39 pounds of pressure, and tinker from there.

The question then does the atomization become an issue? You'd THINK they were tested at a pressure where they had a good spray pattern, BUT, perhaps the higher 43.5 pressure is better? ....in which case a different ECM setting would be in order. Just because they were tested at 39 doesn't mean they have a good spray pattern.

JP86SS

iTrader: (1)

Measured results on 30# SVO injectors.
This the report I got on mine and VernW also had the same results with his.
Just some fuel for the fire but it is actual not theoretical.

pandin

Abubaca

If you do a base line with the stock injectors. Say Idle and a few other repeatable rpms (35/55 mph same stretch of road?). Then change injectors and see what the blm's change to. Then change constant. Then change fuel rail pressure. See what the results are.

Also the vacuum change "will" (see next post) effect the out come (Idle vs no vacuum).

I am sure the out come will be interesting.

"Paper" vs "Real world" numbers. Maybe one or more of the "multipliers" from the calibration sheet is causing the differance. ???

Some math 39.15# + 11% = 43.45# Jim85Iroc avg of 8 injectors 27.01#hr/ 24#/hr = 12-13% increase. This is well inside the compensation area of a MAF system. 128 blm + 13% = 144 blm. ???

JP86SS

iTrader: (1)

Vacuum control of the fuel presure is to maintain the pressure differential across the injector so the output is linear with respect to PW calculations.
Otherwise fuel delivery would change with engine load.
Just thought i'd point that out.

pandin

Thanks JP86SS.

So should Abubaca be using the no vacuum setting, to start?

Also then with vacuum what would the fuel line pressure drop to at idle?

I did not write it down the last time I pressure tested mine. CRS

My idle vacuum is 17"

Blown87IROC

Exactly this happens under supercharging. Normally aspirated engine vacuum goes close to atmospheric pressure at WOT; however, boosted engines go beyond atmospheric pressure, increasing fuel pressure up to the pump’s potential, depending on boost. Then you run into another problem—at higher RPMs the pump’s volume can be exceeded, causing pressure to drop, leaving you with an ugly fuel delivery curve to deal with rather than no curve as with NA engines (unless the pump can’t keep up).

pandin

Copied from their Tweecer Beta3 tuning guide.

All Rights Reserved (c) 2001-2006 STKR, LLC
ÓSlower Traffic Keep Right, LLC
www.TwEECer.com


Injector Specific Parameters

83lb-------- 1 ----0.95--- 0.7---- 0.5----- 0.25- 0.25

Abubaca

iTrader: (3)

Guys, I find all this very interesting, but I'm not actually a DIY Prom guy. While I understand most of it, I have no practical knowledge of it whatsoever. My buddy Josh (OnemanArmy) has a Notchback GTA and he recently purchased the gear needed for datalogging, and I think we're both gonna go in on the burning hardware, but this injector issue is being paid for Sorry guys, time was of the esscense.

....originally, the plan was to have the factory Multecs serviced, but Rich at Cruisin' Performance recommended new injectors based on the high mileage and shoddy reputation of the Multecs. ...thus starting my interest in all this. But the Multecs are already out, and they're not going back in for testing!

pandin

If you look at some of JP86SS injector pulsed flows (not all) they were at 90%. 30.49#/hr, avg of the eight, times 90% = 27.4#/hr

If this held true for the 24#/hr, then OR89RocZ number of 25.2#/hr is high. 90% of the 27.01#/hr, eight injector avg. = 24.3#/hr.

I think the on/off times for the < 100% duty cycle are limiting the flow.

Actual fuel flow is what needs to be entered into the injector constant.

At 43.5# fuel line pressure, the 24#/hr at 39#FLP injector flows 24.3#/hr because of the on/off times. Any comments to this way of thinking?