RBob

iTrader: (1)

Yes, you are static on the injectors. At 6,000 RPM the injectors fire every 10 msec. Your are over that on injector PW with the first run-up the RPM (1st gear?). Even the next run-up in RPM (2nd gear?) is going static (from what I can tell from the graph).

The problem with static is not the injectors sitting wide open (the definition of static), the problem is during the decrease in duty cycle there will be a point that the injector is opening/closing/opening. . . without ever really closing.

This causes the pintle to start banging open/shut in an erratic manner. This beats the injector to death. How long the injector(s) stay in this state will define how long before they start to fail.

RBob.

87400tpi

I think if you go w/ bigger injectors you be in the 10s,no problem.Then what would the maf haters say.It's seems like the maf might not be at it's limit, yet.

ski_dwn_it

Hey guys I have the actual number, I went home at lunch and downloaded them off the computer. So am I understanding you all right? That anything past 10ms is static. How do you come up with that number? I do not understand, can someone put it out on the table with some calculations. I am skeptical that I am static, but if I am then there may be some ETs in there yet. I am all ears.

I am running the stock intake tract. I plan on at some point picking up a vaccum guage and attaching it to my intake plenum. Then make some WOT passes. If I see a vaccum anywhere while at WOT then I have a restriction. Remember fellas I just put this thing together, I have not had hardly any play time with it. Open headers makes that even harder.

ski_dwn_it

Here is the Data:


Engine Speed Injector Pulse Width
RPM mS
1500 2.95
1525 2.98
1550 2.94
1550 2.92
1550 3.04
1575 3.06
1600 3.08
1600 3.08
1600 3.04
1625 2.97
1625 3.06
1675 3.01
1700 3.03
1700 3.06
1725 3.11
1750 3.04
1725 2.89
1725 2.77
1700 2.74
1725 2.66
1725 2.66
1725 2.65
1700 2.68
1725 2.66
1700 2.69
1700 2.69
1750 2.68
1725 2.69
1750 3.35
2200 11.67
3475 14.31
4150 13.85
4525 13.43
4900 12.74
5125 12.52
5075 12.48
4975 12.67
5075 12.41
5275 12.13
5300 11.87
5450 11.23
5825 11.03
5850 10.57
6075 10.42
6175 10.39
6300 10.24
6375 10.08
6375 10.28
5575 11.83
4725 13.36
4600 13.39
4600 13.69
4375 14.03
4125 13.74
4375 13.39
4500 13.89
4475 13.85
4525 13.97
4525 13.43
4750 13.16
4800 13.13
4900 12.82
4975 12.74
5100 12.59
5200 12.41
5275 12.21
5375 12.03
5375 11.83
5350 11.83
5675 11.57
5650 11.11
5700 12.06
3875 14.7
3550 13.77
3600 14.98
3700 14.15
3675 14.11
3600 14.31
3750 14.03
3775 14.26
3800 13.82
3850 13.89
3925 13.89
3825 14.54
3950 14.08
3875 14.46
4050 13.89
3950 13.89
4025 13.82
4100 14.08
4050 13.77
4150 13.89
4200 14.26
4175 13.97
4275 14.03
4175 13.74
4175 14.26
4325 14.26
4350 14.26
4375 14.26
4400 14.15
4425 14.08
4350 13.59
4475 13.46
4525 13.59
4525 13.59
4600 13.62
4500 7.04
4475 1.01

ski_dwn_it

Here is the MAF data:

Engine Speed Mass Air Flow (MAF)
RPM gm/s_
1500 25
1525 25
1550 25
1550 25
1550 25
1575 25.3
1600 25.7
1600 25.7
1600 25.5
1625 25.3
1625 25.4
1675 25.5
1700 25.7
1700 25.6
1725 25.5
1750 25.3
1725 23.7
1725 22.1
1700 21.6
1725 21.3
1725 21.1
1725 21.3
1700 21.2
1725 21.1
1700 21.2
1700 21.1
1750 21.1
1725 21.3
1750 46.3
2200 109.4
3475 193.5
4150 232
4525 241
4900 246
5125 247
5075 246
4975 246
5075 247.9
5275 247.1
5300 247
5450 247
5825 247
5850 247
6075 249
6175 252
6300 253.1
6375 254
6375 254
5575 247
4725 241
4600 239
4600 239
4375 230
4125 224
4375 239
4500 237
4475 238
4525 240
4525 241
4750 244
4800 245
4900 246
4975 246
5100 247
5200 247
5275 247
5375 247
5375 247
5350 247
5675 247
5650 247
5700 247
3875 200
3550 191
3600 200.4
3700 200.6
3675 204
3600 205
3750 204
3775 210
3800 214
3850 208
3925 211
3825 214
3950 215
3875 218
4050 218
3950 218
4025 225
4100 224
4050 221
4150 224
4200 227
4175 229
4275 227
4175 227
4175 232
4325 233
4350 235
4375 236
4400 206
4425 237
4350 207
4475 235
4525 238
4525 239
4600 241
4500 142.6
4475 24.7

TRAXION

For Batch fire systems:

RPMs / Revs per mSec * PW (mSec) * 100%
RPMs / 60000 * PW (mSec) * 100%

Example:
4500rpms / 60000 * 12mSec * 100% = 90%

Tim

TRAXION

As stated in previous post - I have tuned several 350ci heads/cam MAF cars that peg the MAF at or around 4800rpms. The fact that Ski isn't pegging the MAF with a 406ci heads/cam car is freakin' wierd. Definitely twighlight zone material.

Tim

Morley

Looks like you have a tad of MAF resolution yet to go.

I am with the others here on the injectors, the 24's on that high of a HP engine just seem too small. I am running 24's (accel) on my 350 at 46 psi and have had to set the constant to 23.5 to get the BLM's in the respectable range, and I am pushing no where near your HP level (352 at the crank with 414 ft/lbs tq).

RBob

iTrader: (1)

We seem to be getting the same info in two threads now. Maybe time to start another?

I responded in the other thread as to why the MAF _data_ is not showing pegged.

RBob.

TRAXION

He doesn't have any resolution left to go. See the other post in this serious where RBob posted the max g/sec per RPM. He is pegging the MAF.

Tim

ski_dwn_it

Rrob, in one of the first posts you say that I am going static on the injectors above 6000 RpM. Does it just start to happen there? Or is it lower. And can you lay out how you are figuring this out for the people like myself that are a little behind. Thanks.

Morley

He is in the 250's in the 6k+ rpm range, if I am not mistaken, Ski did say that is not where he normally runs during a race.

kevm14

Ski wrote:
The injector constant merely allows the ECM to calculate how much fuel it is injecting. But the commanded pulse width will BE the real pulse width, regardless of what size injectors you run or what your constant is set to. It's just an injector driver board and the units are time, which is obviously a real unit.

Trax wrote:

I think this is incorrect. Max torque implies the highest VE, yes, and this is a higher fuel demand than, say, half that RPM. It is also likely the highest fuel requirement per RPM. But we don't care about per RPM. As RPMs exceed the torque peak, even though the VEs decrease, we are still building HP (hopefully) and more HP requires burning more fuel. You are going to burn less fuel at your torque peak than HP peak (at WOT), not surprisingly, because you have less HP at the torque peak. So what's happening is, you are requiring less fuel per RPM, but MORE fuel per unit time. Therefore, a higher PW is required as RPMs increase all the way to your HP peak RPM.

Ski wrote, again:
This is incorrect. You are suggesting that the area of your injector orifices combined is infinite. This is not the case. even at 100% DC, there is a total area through which fuel can flow and your stock pump can likely maintain ~45psi. Hell, even if you took the pump out of the car and turned it on, just to get fuel to flow directly out of the pump, there needs to be a pressure. There is an EE equivalent to this, if that helps: pressure = voltage and flow = current. The total area of your 8 injectors could be modeled as a resistance to flow. Thus, the whole thing could be modeled, simply, as a simple V=IR circuit, or, more relevantly, V/R = I. If you did the calculations, you'd likely find that it is nowhere near impossible for your pump to provide 45psi against static injectors.
Finally, from another perspective, you are saying that upgrading to larger injectors would do a person no good, since one would be out of fuel pump capacity at that point. Also, do you really think that at, say 95% DC, your fuel pump is fine, then add a couple milliseconds to the PW and all of a sudden, no FP? Of course not. Injectors, even operating static, offer a resistance to the flow of fuel, which will maintain the FP as long as the pump can deliver the flow required.

TRAXION

Word. You got me. I ignored the affect of RPM on DCs which is extremely important. Funny - I metioned how important it was in the other posts but failed to apply it here. Woooops.

Tim

RBob

iTrader: (1)

The amount of available time can be calc'd as follows:

TIME AVAIL = 1 / (RPM / 60,000)

From a portion of your chart:

Any time the TIME AVAIL is less then the BPW you are static. Starts at ~ 4200 RPM.

RBob.

ski_dwn_it

kevm14,

No that thought did cross my mind about the pump being able to supply enough with the injector open to maintain pressure. With now I would have mentioned it as a possibility.

It was just a thought. I am by no means saying these people are wrong with their statement that I am going static, for i would estatic if they were right and all I had to do was take my injectors off and slap some bigger ones in their for some more ET.

But still even after posting the injector pw adn RPM no one except Rrob said i was static and at what RPM. And remember, I shift this thing at ~5200-5600 on the strip.

I look forward to seeing some calculations worked out.

ski_dwn_it

Rrob, now what is pretty convincing and I have to ask the question though. How accurate to real life do you think these are? I have to ask since the calculations spoke of earlier in one of the posts led me to believe there were flaws in them. And lastly how much ET do you think I am missing? 4200 is pretty early and could be costing me a bunch of ET possible, as that is proabably right around max tq and the Hps are climbing after that....

Thanks great information, from everyone!

RBob

iTrader: (1)

Part of your statement is incorrect. Max PW occurs at max VE. This is due to the injectors firing in step to the plug firings. More fuel is injected for higher HP/RPM as the injectors are fired more often per unit of time.

This can be seen in Ski's RPM vs PW chart.

RBob.

RBob

iTrader: (1)

The math is static (ohh, bad pun), what you see is what you get. The fuzzy math comes to injector selection were DC and BSFC comes into play.

As for ET, probably a wash. The only reason is that you do have enough fuel to get a decent AFR. I posted in one of these two threads that the problem isn't going static, it is the portion of DC where the injector is bouncing open/close but not attaining either. It will beat itself to death.

Of course if for some reason you found some hidden HP you could easily go lean since you are now max'd fuel delivery wise.

RBob.

RBob

iTrader: (1)

edit add in: from previous posts it appears your injectors are flowing 26#/hr.

So at a BSFC of .5#/hr/HP:

26 * 8 / .5 = 416 HP

At a BSFC of .45#/hr/HP:

26 * 8 / .45 = 462 HP

SATURN5

What would be intersting is adding in a MAP sensor and feeding the output into say.. TPS2 input of the ECM and add a patch to output the reading into the aldl stream, Something similar to the WBo2 feedback patch should work.

Then you could compare apples to apples..



My thoughts on why Ski is maintaining a decent AFR once his injectors are static, that the maximum arflow thru the MAF is reached.. no additional air.. no additional fuel needed.

TRAXION

Well - I am outta here due to family vacation. Other moderators will be watching the board. I'll return on Wednesday of next week and will probably reply at that point.

Tim

87400tpi

I did say I think you could be static.Look at your pulse width around frame number 2900.I also agree with Rbob,those injectors are not bouncing hard,yet.

Your maf has'nt pegged yet because you have stock air intake.I know you would see higher gr/sec if you opened that up.That is why you see the spikes in the last bit of the gr/sec log.But that does'nt matter.Like I said the 255gr/sec theory is bust.


Ski,I have another warped thing to share.First do you have the stock maf screens?That could cause that spike.The stock maf screens are made to create a vortex.That is the best form they found to get acurate maf reading.BUT for a car like yours,I would suggest a coarse screen(bigger holes).The factory screens are a restriction at a point.But it's always good to keep the screens for acurate readings.I tuned my maf tables for no screens before,ran great.But the idea is to keep that vortex.

ski_dwn_it

Saturn,

I'm game with any experiement you guys supply the hardware and instructions.

As for the maxing of the MAF unit, as I said there was a N/A vette that ran mid 10s on his, with a 1300 CFM monoblade TB. The calculation for a 406 at 6500 RPM and 100% efficiency @76* F shows an air demand of 768 CFM.

1. i am not taking my engine that high
2. I doubt the eff. is 100 %
3. I'm not running mid tens, YET

Who knows though, all I am saying is a lesser engine surely doesn't need to switch over for the reasons of MAF being a restriction all things equal.

ski_dwn_it

I gutted the screens a long while ago, along with the heat fins. its wide open thoughout.

The other thing I should mention, since you mentioned it again. The air duct is stock up to and including the MAF meter, but the filter housing etc is all from TPIS, its their cold air system that pulls from down by the rad through the fan shroud. Its HUGE, so that is surely not a restriction.

87400tpi

I'm not sure about the vette but the l98 for firebirds came with a "silencer box".Do you have that between your maf and tb?If so it will cause problems.

ski_dwn_it

No silencer, it looks just like this, and yeah the AC still works, keep me cool while in the pits/staging lanes



Here is a little better one...



And here is a shot of it going together with so you can see the #24 injectors too.



Opps got one extra there too...

kevm14

Ah damn. I concede. Well, 2/3 ain't bad...

Funny thing is, I was looking right at that chart as I typed that response, and I even noticed the affect of higher PW lower down in RPM. I must have just ignored it.

87_TA

Well I would love to convert back to MAF just as an experiment,
but that experiment has been done from me already by switching to SD.
When I switched I picked up 1 mph,at that time I was only running 12.9 so no great increase.
But I can tell you the other day at the track I removed my cold air induction and gained a tenth and 1 mph,and thats not as restictive as a MAF.
But also one of the reasons you MAF is not killing you is because
of the short,straight shots in the vettes along with forced air.

I would take one for the team,but after hours of repinning and cutting MAF wires to use for MAP its not that easy. Had I known then what I do now I would have made the adapter harness.
As for the hesitation,that was only at Free rev after sitting for a while idling.. But now trax and grump shared some insight I should be able to tune that out.

87400tpi

The air lid looks good but if I was running that fast I would cut some 1in holes in tha thing.It looks like a slight bottleneck by the radiator.I think you could gain some,it would look ugly.I think your engine would breathe better for sure.If you did gut that thing your maf spike might go away.Are you going to get some real injectors??I don't think new injectors will shave off alot of time though,it might.

JDEstill

Hello all, a friend of mine sent me a link to this thread. Interesting... Thought I could contribute a bit if I may.

First off, I'd like to say that it looks to me like people get hung up on BSFC when doing injector sizing. I realize there are formulas out there that size injectors based on some assumed BSFC. To me that is completely wrong. Injectors should be sized based on engine airflow alone. That is all that is required. As pointed out earlier, if the engine is moving X gm/s of air, then it needs Y gm/s of fuel to get the desired air/fuel ratio. The amount of hp that air/fuel makes doesn't matter a bit.

Example: two engines, A & B. Both are moving 300 gm/s of air at some given rpm, etc... Engine A is has low compression, low timing, was poorly assemebled, etc... It makes 317 hp. To get an a/f ratio of 12.5:1 it needs 24 gm/s of fuel.

Engine B has high compression, the right timing, was well assembled, etc... It makes 475 hp. To get an a/f ratio of 12.5:1, it also needs 24 gm/s of fuel.

Engine A has a BSFC = 0.6. Engine B has a BSFC = 0.4. Both engines need exactly the same amount of fuel because they are moving the same amounts of air. But the hp they turn that air and fuel into can vary widely. There are just so many factors that go into the BSFC...

Now turn that example around. Suppose the owners of the two example engines are trying to pick injectors. If they both use the typical formula that uses BSFC, the owner of low power engine A might take his power level, plug it into the formula, and get an injector that is too small for his needs, while the owner of engine B that is making great power plugs in his hp and picks an injector that is too big. In reality they both need the same injector!

Here's a little spreadsheet I whipped up.
http://pages.prodigy.net/buickv6/_im...0pw%20calc.xls

Basically you just plug in a few items and it will tell you what kind of inj pw and duty cycles you'll be seeing for a given injector size. The only kicker is estimating the volumetric efficiency. This isn't as bad as it might seem at first glance. When you look at the error you get if you miss the VE by 10%, you'll find it is a LOT less than the error you get by missing the BSFC by 10%.

The numbers that are currently in the spreadsheet are based on the 406 in question. It certainly shows that with the low rpm that is being run, the injectors being used should be getting close to the limit, but it is certainly believable. I would say that if the engine was revved up any higher, or the volumetric efficiency is higher than what I estimated, you're looking for trouble.

A couple of other points. It was noted that max pw occurs (or at least should occur) at max torque, which is a good point. Max torque occurs when you get max cylinder filling, which then needs the max fuel squirt to match it. It isn't always understood that this is on basis of a single event, this isn't rpm related. If you look at the air and fuel entering the cylinder for one stroke, both hit maximums at max torque. As rpms increase, the cylinder gets filled less efficiently, but more times per second, so the air and fuel *flow rates* may keep going up, by the inj pw, since it is on a per firing event basis, does indeed go down. And even though each individual inj pw is going down after peak torque, since it has less and less time to do that squirt (since rpms are going up) the duty cycle does keep climbing until it hits 100% somewhere along the way. At which point you're out of injector.

Sorry for the dissertation. Hope I added something.

John

Grumpy

Yep.
But why not use some of the millions of dollars of research GM has done, and let that work for you?.
I've taken to using a simple formula.
If you want to double the HP of a given motor double the injector size.

All the BL numbers and strategies fall into place, if your tunning closed loop, and you AE allowances will be alot closer.

87400tpi

Add something???
You have the best method calculate duty cycle.The bsfc stuff is not that reliable. Ok now ski is noy maxing the injectors then what is the problem folks?
John ,what about this one

ski_dwn_it

JDEstill,

Very well put, and thanks for the spreadsheet. Looks like you just proved that its possible to have control of my AFR as I claimed to and do have.

If you go back a while ago, I basically said the same exact thing you did. Your example might have been a little clearer and more well thought out.

Clearly I have a very efficient optimized setup, its hard to put an equation to something like that. Other than ETs and HP.

87400tpi

Now that is funny,are you joking.If not then I can see why you disagree with me and ski.I think I'll stick with JDEstill's method for calculating duty cycle.OMG

ski_dwn_it

Grumpy this is not anything toward you, but I deal with GM on a regular basis and the last time I visited their St Catherines facility to meet with some of their top engineers on a project we are providing for them, I was a little surprised at how little common sense these people have...let me lay out the story for you.

We get a call that out bolt holes are not round, shortly followed by a fax of a zeius trace on a cmm. The circle that was on the page looked like my 20 month old kid tried to draw a circle. Anyways I proceed to review the print and it was under 1500 power magnification. We'll out process is precise and holes are round to .0001" and things can't change in the middle other than gradual wear. Here what they were seeing were scratches in the pins we use to size the part. And I don't care what kind of hole you are looking at, under 1500 power mag. its not gonna look round. Then they call us back with another complaint, the bolt that they auto feed in to our supplied part would not go through one of our pieces. So I said enough is enough and we took a 4 hours trip up to their facility. Got their and met everyone and proceeded to their world class quality lab as they descibed it. They hand me a part we supplied and a bolt that is to go through it. This top engineer says now explain to me why this will not fit, we thought you were doing 100% inspection. I replied, we did do 100% inspection, did anyone question the bolt manufacturer? Just then I tried to put the two together, indeed the bolt stopped ~.5inches in. Not making excuses, just seeing what investigation they did into the bolt, I asked if anyone checked to see if maybe the bolt was bent, No can't be bent. I said I suggest that you check that by spinning it and an indicator. Just then I said well how many of these bolts won't go through? Just this one so far. I was feeling pretty good that it definately wasn't our part then, but I did not have any other bolts to try, and I asked for a plug guage the size the bolts are suppose to be. As he went to get the plug guage I started looking at the bolt real close, here about .5" up this bolt was a huge lump, like a big old booger on the side of it....I just shook my head. The guy returned and I showed him first that the plug gage when through no problem, the I proceeded to show him the knarl on the bolt that was the entire problem. He was like Oh! Guess your off the hook then. what a F'in idiot....head engineer...if he was working for me he would have the option to be head janitor, and that might be giving him too much credit, or he would have been out the door.

All I am saying is while GM is a monster.....I would take anything they say with a grain of salt. believe me they are not gods. I could give you case after case, and my cousin works for them, he has told me stories that would make you shiver everytime you went to buy a vehicle.

87400tpi

Not trying to be rude ski,but you really wasted your time.Any reasonable person will find grumpy's method on injector sizing unfortunate at best..

JDEstill

Grumpy (I assume this is bruce?), I'm certain that your method is safe, but it doesn't address increased power due to increased efficiency, it only works if you are increasing power due to increased air flow. And what if your car isn't GM, or what if it wasn't originally fuel injected, what then?

87400TPI, I thought all that got hashed out eariler in this thread The gm/s = cfm x 0.5663 I'll pretty much agree with. It is a simplification, and a different air pressure or temperature will change that .5663 factor. But still, close enough. The 1.3 cfm per hp I don't like, since it has the BSFC assumption embedded in it.

As for the implication that when you get to the limit of what the MAF can read you are all done, I don't agree with that. As long as you don't mind commanding more fuel in an open loop kinda way, then keep on truckin'. If the MAF hits the limit but the ecm knows to keep adding more fuel, then that doesn't seem like a problem to me. I've got a Grand National, and in the GN world hitting the 255 gm/s limit is quite ordinary, and it doesn't stop us from going fast. Now having the ecm able to see the increased air flow, I'm all for that, I think it is definitely the superior way to do things. But in practice, for good tuners it doesn't seem to be a real handicap.

John

87400tpi

I've had to defend myself over about 300 post on that exact point.

SATURN5

Typical corperate mentality...

Engineers at DuraMax are about as bad..

They have a Jap manufatred 24 V DC 220/110V power supply in most of the CNC machines. I havent been to the facotry to see exactly how the supplies are mounted, I fix them thru another supplier, but all have suffered with mechanical fatiuge (sp?) of the solder joints of the larger parts.. They are litteraly being shaken until they burn out the connection. I have offered suggestions on how to remedy the problem, including doing the fix myself as the units cycle thru..

Nay.... the $25 additional plus the original repair is too expensive..

$500 supplies.. month to get from Japan.
$250 here when available.

$150 to fix them.. takes about 30 mins each.

Damn I love corperate mentaility....

Morley

And this, boys and girls, is why they are engineers and NOT mechanics. I deal with this particular breed of moron on a daily basis, they can do wonders with paper and numbers but if it is mechanical, they simply are lost.

Pablo

iTrader: (1)

THANK YOU JDE

You have just successfully explained why I had a problem with the bsfc formula for the past several years. I do believe I posted about that several times but the formula couldnt be wrong I must have been wrong or my setup must have been wrong ( or so I was told, in reality the math isnt wrong it just doesnt apply well at all) Its simple enough really, I wish I would have thought of that.

I went for a year with HUGE amounts of fuel going through my engine and I just ignored all the warning signs because everyone said that formula was gospel and I should surely be melting down my engine without more fuel. Im surprised I didnt wash out my rings instead.

That was a year of wasted gas and lousy performance till I said Fvck the formula and turned the fuel back down.

Thanks

87400tpi

Another bust method uncovered?

goneracin

I have been away from this board for awhile, and was just doing some reaserch. This has been an interesting post.

Man, I hate to beat a dead horse here, but BSFC is a relavent figure. Lets say that 2 engines are on the dyno. Engine a is 812 cid and makes 1650 hp. To achieve this, it required approx 600 lbs/hr of fuel(high .30's brake #s). Engine B is also 812 cid, also makes 1650 hp, but only requires 530 lbs/hr(low .30's brake). Both engines carburated, with same set of carbs(to take carb emulsification, distribution, etc out). Adding fuel to engine B, or taking fuel out of engine A, both result in lost power. BSFC is a measurement of how much fuel the engine effectively burns, and converts into H.P. If I were to assume, having only seen the information from engine B, and were to convert to EFI, sizing injectors only by the info from the leaner motor, I could possibly
undersize the injectors. Ski's engine, if on a dyno, would probably have a very good bsfc number also.Doing some guessing (500 hp,90% flow from 26# inj would be about .38, very good). The biggest problem with an injector chart using bfsc numbers, is not many people have any experiance with what an engine will have, or should have for a brake number. We even sometimes get caught up in trying to tune for a specific number, rather than what the engine tells us it wants. Having said all that, JDE's injector chart is a very useful tool for figuring inj size, probably more useable, and accurate, to the majority of people than a chart using only the bsfc. Sorry about the rambling, but its kinda late at night .
Anyway, very good post, lots of good thought provoking ideas.
Bob