z 28 jari

iTrader: (1)

Hi,
I take some winaldl logs at idle(750rpm) last saturday and noticed that injector pulse width(bpw) was only 1.2-1.3ms,and integrator was from 92 to 102.BLM was 108.
At first logs intergator was at 85(fuel pressure was 43psi)After that I lower fuel pressure to 37psi,and after that integrator was previously mentioned 92-102.Engine have 30lbs FMS injectors.Are those injectors rated to 30lbs at 39 or 43 psi fuel pressure?
Engine is sbc 355,vortec heads,stealthram,hotcam,tri-y's ,no cat etc.Ecm is -870 with lsracingchips tune.

-Jari-

Grim Reaper

What type of injectors? Ford's are rated at 38 or 39 psi (as I recall) and GM and Accell are rated at 42 psi (as I recall).

z 28 jari

iTrader: (1)

Injectors are 30lbs Ford injectors(Ford Motor Sport)

sofakingdom

iTrader: (1)

Looks to me like too much injector.

The usual choice for a moderately modded 350 is the "blue top" Frod/Bosch 24# ones, like these.

http://cgi.ebay.com/ebaymotors/24-IN...QQcmdZViewItem

http://cgi.ebay.com/ebaymotors/Ford-...QQcmdZViewItem

I don't know anything about these particular sellers or their parts, just using them as an example.

AFAIK there is no difference between the ones you can get out of junk cars, and the ones that sell over the counter as "performance" "motorsports" parts. AFAIK they are the same Bosch part #s, depending on the year model and "style" of the body. I believe they come in some BMWs and other cars as well.

z 28 jari

iTrader: (1)

I asked also local Bosch injector dealer and he can't either tell which pressure those injectors were rated.Only that he can tell was that Bosch rated injectors at n-heptane(sg~0.68)which means that they flow little less at gasoline(sg~0.77)What is lowest pressure that I can use with these injectors?

VincentZ28

iTrader: (2)

Up grade your wire harness to Speed Density. No one tunes the old and out dated 870 ECM. Thats your problem right there.

sofakingdom

iTrader: (1)

Changing the ECM won't fix the fact that the PW is already as narrow as it can possibly be, and yet all the integrator settings are still trying their hardest to TAKE FUEL OUT.

Obviously, lowering the FP brought them closer to ideal, but they still have a LONG WAY to go.

Likewise, the fuel pressure at which the ratings are specified, won't change the same set of facts.

AFAIK Bosch rates their injectors at 43.5 psi.

Lower pressure is bad. The lower the pressure, the less fuel atomization you get. The car will run better and be more efficient with smaller injectors and higher FP, than with larger injectors and lower FP.

AFAIK the injectors will not work very reliably at less than about 35 psi. So you've already gone almost as far as you can go, in the direction you're going. Problem is, you need to go about 3 times as far as you've already gone, to get the mixture right. There's simply not that much adjustment available by that method.

30 lbs/hr injectors are enough for about 500 HP. They are commonly used in 383 or larger motors, with SUBSTANTIAL modifications. They are too big for practically any naturally-aspirated street 350.

Sounds to me like you simply have the wrong injectors. You will NEVER be able to get the motor to run right with those huge things in there. Sell them and buy the right ones. You can probably even make a proift.

z 28 jari

iTrader: (1)

I select those injectors based a engine dyno sheet(measured with 750 carb and open headers)Max readings were 413hp/bsfc 0.426.I made injector selection at here http://www.rceng.com/technical.aspx
It shows needed injectorsize is 27.65 lbs/hr at 43psi at given values.So I think closest were 30 lbs/hr...
Are those injector size calculators based to SAE horsepower(measured with assessories)or gross hp?If I re calculated new flowrate at 37psi it shows 27.66lbs/hr.If those calculators are based at SAE hp,that explains mismatch because I think engine shop rated that engine at gross hp.
So next I borrow 24lbs FMS injectors at my friend and re test,but then chip is again mismatch because it is burned to 30 lbs injectors.

-Jari-

sofakingdom

iTrader: (1)

Ignore the "calculator". It seems to disagree with the REAL WORLD (the thing in your garage).

What value did it put in for BSFC?

Believe the ACTUAL RESULTS. They do not lie, and leave no room for uncertainty.Sounds like the best thing to do.

Let us know how it turns out.

z 28 jari

iTrader: (1)

I put there BSFC value 0.426.That is from dynosheet which came with engine.
I will tell results when I have retested with 24lbs injectors.Only bad thing is it is now winter here at Finland and no test drive untill next spring(4 long months...)

-Jari-

sofakingdom

iTrader: (1)

413 HP
.426 lbs/hr/hp BSFC
8 cylinders
90% duty cycle

413 HP * .426 lbs/hr/HP = 176 lbs/hr

176 lbs/hr / 8 = 21.995 lbs/hr/cyl (per injector)

22 lbs/hr / .9 DC = 24.43 lbs/hr <-- There's your injector size.

Could be as much as 25-26 lbs/hr if you want your WOT duty cycle to be lower. In which case, bump the FP up a lb or 2.

Looking at your integrator values, I doubt your chip will need as much changing as you might think. I would bet that your integrator values will be right in the correct range (120s) with the smaller injectors.

RednGold86Z

iTrader: (1)

Does the engine run well with the low PWs? And, is the O2 switching normally in this situation?
If so, probably just need to calibrate the PW table better, or the injector offset.

If there's a large discrepancy between low RPM and high RPM at the same LV8, you might be fighting one of several things, such as the MAF, fuel leakage (from anything, such as pressure regulator, purge, injectors).

You do have the vacuum connected to the pressure regulator, right? Need to adjust fuel pressure with it disconnected, then reconnect it when done - and it'll drop on the gauge.

z 28 jari

iTrader: (1)

To Sofakingdom:I calculated injectorsizes at 80 duty cycle.
I run now original fuelpump.Can pump supply easier more volume at lower pressure(37psi to 30lbs injectors vs.45psi to 24lbs injectors)?

To RednGold86z:Engine is running otherwise nice,exept it's rich(little bad mileage),o2 swithing seems normaly.I have vacuum connected to regulator(and fuelpressure adjustment make at vacuum disconnected)When adjusted fp to 37psi there is ~32psi at idle (vacuum connected)

When I was at dyno at october it was rich at wot(a/f 11.0) and midrange (steady load ~2500rpm at 3rd gear a/f 11.7)Fuel pressure was 43psi at dyno.
Any good quess how much this rich a/f actuate to power?

-Jari-

sofakingdom

iTrader: (1)

Yes the pump "can" supply the lower pressure.

On the other hand, even if a thing "can" be done, that is not the same as "it is a good idea". In this case, if you lower the fuel pressure, then instead of fuel spraying vigorously out of the nozzle in a fine mist, it will sort of just dribble in large liquid drops. Bad.No, that won't get the job done.Think about it. The ECM is ALREADY commanding the LEAST amount of fuel it can possibly command. It doesn't matter if you set up the ECM's programming to shorten the pulse width based on air temp, injector constant, tables, or what; at the end of the whole process, the only method it has to control the outcome, is to adjust the pulse width. Well, it already has the pulse width AS SHORT AS IT WILL GO, but even that short, IT'S STILL TOO LONG. So at this point, it doesn't matter by what mechanism we tell the ECM to shorten the pulse width, it can't possibly do any good.

The injectors are too big.

I'm really struggling here to understand what's so difficult to understand. Why are you so resistant to allowing yourself to confront the only possible conclusion that can be drawn from the facts at hand? The first law of TUNING a car is to BELIEVE what the facts you observe are telling you. If you refuse to BELIEVE that what's going on right in front of you is REALLY going on right in front of you, then this is probably not the right hobby for you. You have to be open-minded enough to admit that maybe whatever you calculated, planned, intended, etc. didn't quite work out like you thought it would, and be willing to make a change when you see that it needs to be made. Going into "ostrich mode" (head buried in the sand hoping the problem will just go away) won't really fix anything.What is THAT telling you? Your A/F ratio ON THE DYNO was 11.0; should have been around 12.7; even under the IDEAL conditions of the dyno, your mixture was already almost 20% too rich. Are you listening to what the dyno numbers are telling you? THey're saying, in no uncertain terms, "YOUR INJECTORS ARE TOO BIG".

The FACTS are all telling you, LOUD AND CLEAR, that the injectors are TOO BIG. Every single fact you have available to look at, tells you the same thing. They are OUTSIDE OF THE RANGE within which they can be controlled to meter the correct amount of fuel for YOUR engine, as installed in YOUR car (which I'll bet that a motor that made 413 HP on an engine dyno, makes less than 375 IN THE CHASSIS, which is yet another reason why the injectors are TOO BIG). There is only one correct solution to the problem of the injectors being too big. I wonder what that could be?

See my signature for advice on inductive logic: that is, making observations, and based on those observations, figuring out their cause.

Section162

THIS IS VERY WRONG. Just because a lot of people think 30# injectors are "too big" for almost every small block, doesn't mean that it's true. In this case, it probably means they read it on the internet so many times, they assume it somehow *must* be true.

His combo is surprisingly similar to mine. Vortec heads, upgraded intake, hot-cam-sized cam, and MY 30# FMS INJECTORS. Set at factory fuel pressure. BLM's are 128. Idles and runs flawlessly. Very easy to tune.

Sofakingdom, with all due respect, in post #9, you tell him to "ignore" any calculator. Then, a few posts later, you give him............... a calculator to use. A search on the DIY-PROM board will provide hints on how to properly size your injectors. Most of the time, the (misleading) calculators aren't required.

We shouldn't blame the injectors for what's very likely a lousy mail-order chip.

sofakingdom

iTrader: (1)

THE PROBLEM IS NOT THE CHIP!!!!! The chip is already doing ALL that it can do to keep from drowning the motor. I don't care who wrote the tables or what, THE CHIP CANNOT GO ANY LEANER THAN THAT!!!!!!!

The injectors HE has are too big FOR HIS MOTOR. YOUR injectors might be fine for YOUR motor, but HIS are TOO BIG for HIS motor.

See my signature for a helpful inductive logic hint.

z 28 jari

iTrader: (1)

I will test those 24lbs injectors as I said at post#9.Can I calculate duty cycle like this,if engine makes it max. power approx. 6000rpm.
Injector close and open takes~1ms ,one minute =60000ms
60000ms/6000rpm=10ms ->10ms-1ms(what it takes to close and open injector)=9ms ->9ms/10ms=0.9=90% max.duty cycle.
If this is correct way to calculate max.dc,I test next spring at deep hill how many ms winaldl shows.If there is more than 9ms->more fuel.Final a/f check is made at dyno by wb lambda.
Is it somekind safe margin why lt4 engine uses 28lbs injectors?It makes 330SAE hp,and if my combo is well tuned it makes abot same.

sofakingdom

iTrader: (1)

I couldn't say, about the LT4; never have worked on one.

However, flip it around the other way.... the factory used 26 lb/hr injectors in the LS1, which makes 375-410 HP, INSTALLED IN THE CHASSIS. (with FACTORY exhaust system, STOCK air cleaner, emissions accessories as required, water pump, etc. etc. etc.) As opposed to, on an engine stand during dyno testing, under absolutely ideal conditions.

z 28 jari

iTrader: (1)

I found this: http://dtcc.cz28.com/flow/index.htm
It says:LS1 injectors 25.2lbs/hr at 43.5 psi,but dont they use 58psi fuel pressure at LS1.It makes them flow 29lbs/hr.
I compare my engine to lt4 because it is somehow similar(vortec head design,hot cam)

z 28 jari

iTrader: (1)

24lbs injectors are in place and take winaldl logs.Runs at idle still rich,int 101...107,blm 108.Fuelpressure was 47psi at test.Wot a/f ratio is BIG mystery...

-Jari-

Section162

Jari, have you verified that there are no problems with any of the above? Also no exhaust leaks? Are you absolutely sure that you are getting accurate data from your logs? You changed from 30# injectors to 24# injectors, changed nothing else, and the BLM is still 108?

z 28 jari

iTrader: (1)

Maf readings at idle are(1000rpm aldl mode) 12-13g/s and increse when gives throttle.Injectors do not leak,holds pressure several hours.Injectors are 2 years old/~10000mi.Fuel pressure regulator works normaly,rises pressure when gives thottle.No sound like exhaust leak.O2 sensor crosscounts go from 0->255 and then starts counting again.Data stream seems ok,I did change only injectors(FMS 30lbs/ 37psi->FMS 24lbs/47psi)
Injector pulse width was better than previous test.It was now 1.6ms at idle.

-Jari-

Section162

If you changed to the smaller injectors, with little change, it sounds like something else could be amiss. You should do some more investigating into why the engine seems to be getting too much fuel.

Damage to the diaphram in the FP regulator could cause raw fuel to leak into the manifold. Another example: exhaust leaks will skew the O2 sensor readings and cause the ECM to think the engine is too lean and add more fuel. Engine misfire has the same affect. (Just because you don't hear a leak doesn't mean you don't have one.) Do some searches on these boards for others with the same problem, etc, etc, etc.

z 28 jari

iTrader: (1)

I rechecked fuelpressure drop.47 to 37 psi about 10 minutes.Next few hours about 3-4psi/hr.After 24 hours there was 11psi left.So injectors don't leak too much.Fuelpressure regulator didn't leak either(no gas at vacuum hose)Next thing that I will check is distributor cap.It has been now 5 months/1000miles there(MSD cap,distributor and wires)

O2 sensor is also 5 months/1000miles old(one wire non heated Bosch sensor)
It measures from 3&5 cylinders exhaustgas(tri-y headers)
So anyone have good tips how I can check if there is some leaks at exhaust system?There is not any sound of leak.

TA

iTrader: (1)

If you have tri-Y headers, you might need a heated 02 sensor, as the increased distance from the exhaust valve and thin tube construction of the headers allows enough exhaust cooling to throw the 02 sensor readings off.

Just a guess

TA

z 28 jari

iTrader: (1)

TA,that might be worth of trying.I checked distance of that o2 sensor,it is ~16" downstream at primary tubes.Those headers are ceramic coated.
If I put there heated sensor,should I simply take power to heater element from place that have power when ignition is "ON"(like fuel pump relay),or is there better way to do power feed to heater element?

anesthes

iTrader: (12)

1.2-1.3 is about as low as you can go with most injectors.
Your pig rich (11:1 on the dyno?)

1) Your injectors are too big
2) Your cam is too small
3) Don't buy mail order chips.

I'm closing this thread. sofakingdom did a pretty good job pointing out what is wrong. Hes been there, done that. I have too - numerous times.

A lot of folks are mislead (including myself just a few years ago) into thinking this crazyness about needing huge injectors, dangers of going 'static' and so-on. A lot of it is horsecrap, and what is NOT horsecrap is simply apples to oranges. Not everyone here has a turbocharged 3.8. Myself, ski_dwn_it, tpi-roc, and others have found that smaller injectors, high fuel pressure, and "static" almost always worked out better than over injecting a car. Even if you need that much fuel on the top end, our ECMs cannot support the firing mechanism required to make the car idle at anything near stoich. A lot of these guys know TONS about tuning, way more than me. But a lot of them also don't have the money to try as many wild combinations as they'd like to prove some of the theories they preach. Take everything with a grain of salt, especially what I say. Theres my disclaimer.

-- Joe