ski_dwn_it

I'm surprised that no one want to converse about the AFR graph I posted.....

87400tpi

In a year from now that will be the hot topic.

ski_dwn_it

I guess it sorta shows how exact you can get with MAF and it scares some away...kinda hard to refute exact tunes and undeniable ET slips. Oh well.

87400tpi

Could you do me a flavor and post your current pe a/f ratio table and injector constant?I have a few ideas but would like to see that stuff.

ski_dwn_it

You will have to wait till I get my car back and I can verify what chip I have in there. I have it out at the dealership up on a rack, planning on tweaking a few items this week....

RBob

iTrader: (1)

Well. . . it is a little difficult when the AFR scale can not be read. Though I'd be tempted to mention that the AE fueling is lacking and the AFR starts to lean out at 5,800 RPM. But without the throttle sensor input on the graph those may be up in the air too.

RBob.

ski_dwn_it

Rrob,

The AFR is right at 12.9 through the entire run, the reason the graph at the begining was skewed, si they had to ease into the WOT so the car would not downshift, and at the end its what you said, they let off the gas, since it was verified that the car started to drop with power, there was no sense in beating it to death with a high RPM run.

I think everyone would agree that it has a pretty steady AFR.

RBob

iTrader: (1)

OK, sounds good. I also do not believe that the question was whether the AFR was controllable throughout a WOT pass.

There is the dodo area with part throttle that is being ignored. In your case this isn't an issue, as you are either on the track at WOT, or on the street with part throttle within the MAF/PE limits.

Put another way, why did GM go with a larger MAF when they built the LT1's and LS1's? They not only flow better they also measure to a higher level of flow.

RBob.

black87c4

Looks like you had control of the AFR to me. Did you get my email?

ski_dwn_it

Sure Rob, they flow better than 450 CFM as the stock unit flows, but when gutted mine flows 750CFM.

Lets not cloud issues again. I have come here to share what my experience, a reader of the thirdgen for a while now, as a testimonial to show what MAF could do. Rather than taking about some GN that is tubro charged etc etc, and can run 10s.

Like I explained to 87_ta, I think the majority of people switching to SD from MAF are under the impression that the switch is necessary for not resolution purposes, but rather because the MAF meter is a flow restrictor. That is not the case. As you can see that I am running well into the low 11s with just a gutted MAF meter. Granted the stock unit at this point not being gutted would cause problems, I would imagine. I would like to prove that though, before saying for sure. Alot of things around here that intuitively have been thought to have been gospel have been being reconsidered lately.

If I had it to do all over again, I should have posted a poll of of opinions, as to why people think they need to switch. I think you would all be surprised to find that resolution is probably last on the list for most people. They simply think the MAF meter is cutting air flow down. That is not the case obviously, at least to about the 450rwhp range, and not many people fall into that area.

Also I will agree that there is a range of air flow greater than 255 g/sec that the MAF system looses resolution, but remember you would have to be going ~120+ MPH to achieve that, so are you really loosing resolution, or loosing touch with reality, going that fast on the street? Nearly every car out that that achieves a 255 g/sec MAF reading is for all intense purposes going WOT, where there the PE is used to adjust the AFR.

I think we need to seperate real life situations, to that of theory. That is the key to understanding the systems capabilities and realizing that MAF is just as capable of a system as SD, when it does come down to resolution for non-pe situations.

87400tpi

That is where I'm coming from,real world experience.I also switched to SD because it was DRILLED into my head that maf is fine,up to a point,"if you really want to go fast in a third gen switch to sd"."the maf is restricted to around 350 hp,it physically cant flow over 255 grams".I can go on all day long,trust me.Anyone can do a search on maf and see what's really crackaletin.All the time I have with maf I have learned alot.My gut feeling was to keep the system.Why manually compute the ve curve when maf does it automatically?After the calculations you can even correct them via maf tables(easy).

It is wrong to think resolution can be applied the entire maf system.Ski is close to 10s ,that is faster than I want to go right now.I'm sure I can dig up a BILLION maf guys on the net that is running 750 hp+.Callaway had twin turbo maf vette back in the day,right?If the code readers want to see what is really going on,they need to check out million turbo/supercharged l98 out there.Tubo city seems to be able offer infinite tbi,maf horepower limited by your pocket book.These limits being put on sysems here is bogus.

The Callaways/lingenfelter of the world never was limited using a maf system.I bet they could only dream of the editing software round today.Not to mention the primitive scan software back in what 85-89.There is a reason for me and ski is giving the shakedown here. Is because because of(a little) bogus info, this board is not progressing.

I have done alot of tech work on cars.The map systems seem to be sesitive to the extreme.Under some component failure the map system seem to occur engine failure more often.That is from actual repair work on hundreds of cars,import and domestic.It seem a maf car can run with two dead cylinders.Trust me,ski's 350 could'nt have ran that fast with broken rings if it had SD.I'm sure GM switched back to maf for one reason.Because maf runs better when things are not 100%.

With prom tuning the maf system has the ability to correct things.This puts maf up there with SD when both are tuned.SD might be technically more correct.But under real world conditions maf shines.I have come to the conclusion that the maf system is for engine tuners.SD is for someone that wants to manually compute the exact data to the 3d tables.I have never thought there was a conspiracy against maf.Just a bias towards speed density

87400tpi

...

camarojoe

I agree with you guys, meaning Ski_Dwn and 87400, about the bias towards one system over the other on these boards that has been "propigated" for the past 3-4 years. Granted, I don't post much and when I do it's usually a stupid tech q, but when it came time to tune my car a couple years back when it had the 355, all I heard from guys I mailed and talked to was "MAF's hold'n ya back, switch to SD and go from there". I mean c'mon there's always guys who will say "I have a friend w/the exact same setup that just isn't as fast; we think because he's running MAF and can't get it tuned right". I've heard them all and I'm honestly sick of it. It's about time that the balance of power shifted on these (DIY)boards from the guys who like to use semantics when attacking others to the guys who are experimenting and dissproving old myths. Actually I'm kidding about the power statement but you get my point. I know my attitude is similar to some of the guys who posted earlier, but by *** my opinion counts too. Let the learning hence the knowledge commence, boys and girls.

Joe

ski_dwn_it

And another silent voice speaks out. Its like peaking around the corner to see if the coast is clear, so you don't get hit in the head with a rock.

I wish that more of the people that email me would speak up. Glad to see someone sees the reason for my posting here.

black87c4

--------That is where I'm coming from,real world experience.I also switched to SD because it was DRILLED into my head that maf is fine,up to a point,"if you really want to go fast in a third gen switch to sd"."the maf is restricted to around 350 hp,it physically cant flow over 255 grams"-----------

That's why I bought a 727 ecm and was going to convert mine. Seems like people either didn't want to tune maf, didn't know how or just condemed it out of ignorance. Anyone want to buy a 730 or a 727 ecm I think there will be many more chime in, most are probably like me , didn't really know enough to comment but that's changing thanks to this thread.

RBob

iTrader: (1)

I can't see how you think that I am clouding any issue. You are the one poking the hornets nest with your statements. I have been supportive of all types of EFI, and you?

Exact tune? Your own data shows the injectors are static from 4,200 RPM up to 6,200 RPM. All you really need is a WOT switch to turn them on. There is no tune.

I've asked for two other pieces of data and have yet to see them. You posted a dyno pull from another motor. What does this have to do with the one you are now running? You posted AFR's from Corky's vehicle, again a different motor.

(and if you want me to bring that up, why would he want to run at 10.2:1 AFR? If MAF is so good why can't the AFR be controlled better?).

Sure you have enough fuel to support that? You are static now so the AFR will be leaning out proportionally to the increased airflow. Gonna' chance it?

The problem I see is that you are making statements that you can't back up with data. In other words "show me the money."

RBob.

funstick

Rbob i gotta alot of respect for you but this stament is grossly inaccurate. if he can command the AFR he wnat then obviouly the injectors are not static. ive posted some reasons Why i think this works. no one has yet done anything to disprove my throery let alone prove it. facts are facts. hes not static. if he was then how can a car with SEFI run a 20msec pw at 6000rpm. there something thats being overlooked.

if you could prove me wrong that would be fine. but until you can prove the statements and thoerys i have about how INJ PW and fueling models work at various rpm then i think you should check what your saying.

the Facts dont support you injector firing model. here is a guy with control over his injectors as PW's that you claim he shouldnt be able to.

ski_dwn_it

Rrob,

Hold on a second, you are taking offense to what I said when you shouldn't be. Let me explain, I just didn't want people to take your last statement about the large MAF meters etc as a statement that my MAF meter could not support high HP motors.

As for your statement about injectors going static, if you can prove to me that beyond a shaddow of a doubt and to the rest here that my injectors are truely static, which every other equation someone puts up here shows I am OK, or I am not. What is right, I don't know, and neither does anyone else. The facts still remain, I am able to control my AFR via my WB02 at a 12.8 AFR. I provided the graph of my last engine, because I just got this one together and have not yet had it to a dyno. If you want to send me 200 dollars I would gladly get a dyno quicker I have devolged all I can to help you here, I risked taking the car out on the street with open headers, slick and skinnies on it to provide you with a log that everyone asked for. Trust that I am not here to throw false claims around or do I get a woody on about lyiing to people. My engine is what it is and I provide the data that I can. My 350 dyno was one that showed the control you can have with the system and I think its pretty damn good for all the more time I took doing it. I have asked tons of people on here for information like time slips etc, I have yet to see one. Corkys dyno was provided just as some information to SHOW you that obviously the 24# injectors can provided tons more fuel than you or anyone else realizes. That was from the Fomato chip he is running. Can you explain to me how its possible to get down to 10.5 AFR with static injectors, on identical engines?

Now I think I backed my statements pretty well through this entire posting, or hornets poking. I never called you out, I just did not want to go down the restrictive MAF path, but I am glad you responded, because obviously you had some reserves about the data I was providing.

PLease if anyone else has reserves, please let me know what they are.

Just for the record, I did call a dyno in State College PA about getting my car there for a run. I took my headers off my car this Saturday to let Corky try them on his car. He picked up .07 with the swap from 1 5/8 => 1 3/4 headers. Just thought I would share what we found. I'm trying to help here Rrob, not be a dick. If you read my posts the only time I bite back is when someone trys to step on my toes. I can provided more information about the headers test if your interested. It was done with back to back passes and DA was taken into account.

I just want people to get the true story of what can be done with the MAF system, I don't have anything at all against the SD system, I just hate the myth that has been circulated that MAF is a waste and is worthless. That you can't deny is exactly the wrap it has.

Again I will say that anyone that wants to go over my setup with a fine tooth comb, is more than welcome to meet me at any track I go to, but if you take me up on that and you don't find anything fishy, which you won't. You owe me a steak dinner Sound fair?

RBob

iTrader: (1)

Fun, what? Can't keep up with these multiple 100's of post threads?? Me neither! Anyway ski posted the data in this thread:

https://www.thirdgen.org/techbb2/sho...5&pagenumber=2

And a recap:

When TIME AVAIL becomes less then BPW they are static.

RBob.

ski_dwn_it

And here is another method........ provided in that same post above.....


local atm air pressure 29.92 in Hg
displacement 406 cid
number of cylinders 8
manifold pressure 14.45 psia, or 0.50 in Hg vac, or -0.25
manifold air temperature 80 F
volumetric efficiency 85 %
engine speed 5400 rpm
air/fuel ratio 12.8 :1
injector size 26 lb/hr
injector offset 0.2 ms (allowance for injector opening/closing time)
batch/seq 1 (1 for sequential, 2 for batch fire)
air flow 295.0 gm/sec
lb air per event 0.00181
req'd pulsewidth 19.74 ms note: assumes 1 injector per cylinder and assumes linear flow behavior (ie 40% duty cycle gives 40% of the rated flow)
max pulsewidth 22.22 ms note: pulsewidth at 100% duty cycle
duty cycle 88.9%

Courtesy of JDEstill
last rev = 4/25/03


So who is right? I would go with the fact that I am am not static, unless you can disprove Corky's AFR data, and that was with a 36psi fuel pressure rating, that's probably not even 24lb injectors if you go throught the calcs......again if you would like to meet corky and I at the strip to verify his FP before he goes out to run an 11.2@121, we love steak and would be happy to have takers of the offer come forward

RBob

iTrader: (1)

OK, then how come your reported BPW at 5400 RPM is 11.23 msec? You are only delivering half the required fuel if you believe the above.

Opening time for a saturated injector is closer to 1.2 msec, not 0.2 msec.

RBob.

ski_dwn_it

here it is with 1.2ms:

local atm air pressure 29.92 in Hg
displacement 406 cid
number of cylinders 8
manifold pressure 14.45 psia, or
manifold air temperature 80 F
volumetric efficiency 85 %
engine speed 5400 rpm
air/fuel ratio 12.8 :1
injector size 26 lb/hr
injector offset 1.2 ms (allowance for injector opening/closing time)
batch/seq 1 (1 for sequential, 2 for batch fire)
air flow 295.0 gm/sec
lb air per event 0.00181
req'd pulsewidth 20.74 ms
max pulsewidth 22.22 ms
duty cycle 93.4%

Courtesy of JDEstill
last rev = 4/25/03

Grim Reaper

Ski

I saw that formula too by JDEStill. It is an excellent estimating tool IMO for Injector Size. Better than the basic (Inj_Flow/BSFC) x #Cyls = HP formula we have been using for Injector Sizing.

But, that estimating formula also has a "guestimate" number just like BSFC (which I says mean Bull $hit Fudge Constant). JDE's forumula has "Volumetric Efficiency Factor" (imputed 85%). It is still a subjective number just as BSFC.

Measuring the Injector PW to RPM is an actual measurement of your %DC. No "fudge constants" that are open to subjective opinion. Just the length of time the Injectors are open vs the amount of time available to it based on the RPM.

RBob
I just want to clarify whether you start to go static before100% DC?

At 6,000 rpm, you only have 10ms to open the injector, spray the fuel, and then close the injector fully before you are deemed "static"?

So, if it takes .8 ms (assume) to open/close the pintle, the moment you go over 9.2ms of PW (10ms-.8), you now are going static? So you are actually starting to go static around 92%?

ski_dwn_it

Glenn I was just gonna comment on the fudge factors and the VE fudge factor on the spread sheet, I don't think either are accurate enough to draw any conclusions from.

The facts are this:

1. I CAN maintain a 12.8 AFR, it was down in the 10s in spots before I did the second chip. Steak dinner is at stake if you want to call me out on this.

2. Corkys AFR data with only 36psi and again we would be happy to entertain anyone at the track with verification of his FP before he goes out to run.....just speak up, and I'm sure 87_TA would be happy to meet us at Keystone Raceway on a weekend to be the neutral party......I will gladly provide the address to where the gift certificate of the dinners can go.

Guys I will be the first to admit I have never crunched the numbers for injectors before. I never really had a concern to, since I always seemed to start richer than crap, then move towards a leaner mixture, intuitively thinking I guess told me I was holding back the injector so obviously the injector was not static. Sounds a bit basic, for a person that is maticulous with everything else on his setup, but I don't like to complicate things with overthinking them. I spend the time that others spend doign the before mentioned on the things that most others overlook and take for granted.

I would love to find that I have more power left in this thing. I only need about 20-30 HP to get into the 10s for good.

Please don't think I am being a smart ***.....or even disagreeing with you, I'm just playing the devils advicate. I get paid to do that for a living

Eric Marshall

Yeah, like Rbob said, it should look more like this:


displacement 406 cid
number of cylinders 8
manifold pressure -0.25 psia
manifold temperature 80 F
VE 85 %
rpm 5400
air/fuel ratio 12.8 :1
injector size 24 lb/hr
injector offset 1 ms (injector open/close time)
batch/seq 2 (1 for sequential, 2 for batch fire)
air flow 295.0 gm/sec
lb air per event 0.00241
pulsewidth 15.12 ms
max pulsewidth 11.11 ms
duty cycle 136.0%

The option for batch/sequential should have been set to 2.
Even if the VE "fudge factor" was an awful 65%, you would still be over 100% dc (at 5400rpm).

Unless you have a sequential system?


Regards,
Eric

Grim Reaper

Just for a "test" - try raising your fuel pressure to 52-55 psi as well as Corky's. Provided your fuel pumps are up to the flow demand, you PW should shorten (once you again correct the A/F Ratio to 12.8:1 (your preferred AF Ratio). At least this will reduce your DCs (which is always a good thing).

BTW, have you experimented with other AF Ratios besides 12.8:1? Try a little richer? Or a little leaner? I'm just curious if you have done some minor experimentation +/- 12.8:1? Or is 12.8:1 the ultimate A/F Ratio you came up with after MUCH experimentation.

Just looking for opportunities that may exist in your tuning.

funstick

whats been pissing me off about the whole thing is that each cyclinder takes 20 msec @6000rpm. secondly there something amis. ive posted WHY i thought this works. check out what im saying. whenever the commanded PW exceed what a 4 ref pulse PW would allow the ecm MUST go to firign every 8 ref pulses. that woudl very clearly explain why his setup works.

87400tpi

control of a/f ratio=injectors NOT static

top question:

Why does everyone assume there is something wrong with ski's setup?

RBob

iTrader: (1)

Ya know, not much more I can say. Look at the numbers and use some common sense (kinda like a sanity check, does it pass the smell test?) Ski is running a '165 ECM. It is a batch fire ECM. Every revolution it fires all eight injectors. That is every 10 msec at 6,000 rpm.

When the pulse width gets too short, it will double fire with a doubled PW once every 2 revolutions.

Sanity checks are like this:

Say you are not static and have 20 msec to fire that 10.4 msec pulse of fuel (@ 6,000 RPM, from Ski's data). That means that only half of the time are the injectors open. OK, now rough it in:

26#/hr * 8cyl = 208 #/hr total available

Of course they only are on half the total available time:

208#/hr / 2 = 104#/hr

Then the basic BSFC term, we'll use .45 #/Hr/HP which is in your favor:

104 / .45 = 231 HP

Are you really making 231 HP at 6,000 RPM???

Doesn't pass the smell test.

Now double the PW number (which makes the injectors static):

231HP * 2 = 462 HP

Hmm, looks like a winner to me.

Bottom line is: you have to be static, simple as that.

Wanna 'nother sanity check? What is the injector size used by GM for the run of the mill L98 TPI?

22#/hr

And you can over double the L98's HP w/26's and stay within industry standard design practices? Ski, didn't you say it that the recommended injector for your engine was ~ 44#/hr?

See the problem, it doesn't add up unless you are static.

RBob.

P.S. Ski, when you check the fuel pressure is it at idle?

ski_dwn_it

Rrob and company,

I don't know what to tell you. All I can tell you is what I am know I have seen with my own two eyes and used to tune my car, simple as that. When I did the first chip I was grossly rich, down in the 11s, sometimes 10s with AFR. This was on purpose since I wanted to ensure I was rich while tuning part throttle, and if I touched on PE I did not want to going lean or having major detonation. Once I got the race gas I did some more tweaking and then could open it up, without the pinging. That is where I concentrated on AFR for WOT, it came up a tad with the race gas and then I leaned it out to the desired 12.8 AFR. So I took it from rich at WOT, had to have a large pulse width to leaner, shorter pulse width....don't know how I can be static, like I said any time I adjusted the PE afr I saw a direct response, so maybe my sanity check is off, but I don't think so.

Ralph over on the Corvette forum is running a 350 into the mid 11s with 24# injectors, Corky is running 11.10 with 24# and I'm certain I could dig up tons of others if I liked that are doing mid to low 11s with the injectors.

I see and understand that your formulas don't make sense, but I tend to to trust fomulas when assumptions that are critical need to be made, sorta like the sales guys forcast for sales of the month...LOL....well if this and that and this and that...no give me for sures then I will listen.

Also everyone keeps saying 6000 RPM, I said in the very begining I was shifting at 5200 RPM.

Let me try to bate you in... Would you assume that if the injectors on my car are static I would be able to run as good and strong as I am with the FP at ~45psi? If I am static then what do you think Corky would be with 10psi less? Static at about probably 3000 RPM and grossly static at 5600 (where he shifts)....Right? I would have to assume that is what your saying. Then how does he run 11.2s consistantly at any track he goes too?

I would love to see us get to the bottom of this.....

Let me answer some questions that were asked...

Rrob, the 44 # was off some injector calculator, I just threw that out there to show the huge variety of suggested sized when using available calulations.

I have checked my FP at idle with the hose off the reg. It was about 42 psi, I have also run it with the guage on the windshield and it holds steady through the runs at ~45-46 psi.

Corky's pressure I speak of being at 36psi is with the vacuum line connected at idle.

Eric, you have in the spread shown 24# injectors, shouldn;t that be 26 with the pressure I am running?

I wish to *** I had a miniram that was easy to swap injectors on, I would take one for the team and get some bigger injectors on there, tune it and see what happens. But it would be just to show that the 24s are doing as good of a job.

Can someone in laymans terms explain to me how these critters fire....I mean through the entire cycle...maybe if we lay it out on paper, we can understand it collectively better. Thanks.

Grim Reaper

Ski, just ask yourself this question. Why is it the people in this board that have the longest experience with eprom burning (RBob, Traxion, Grumpy & myself as well as others who've come out of the wood work from time to time) keep saying you are going (or on the verge of going) static?

There is only a few people saying you are not and they have less experience than any of the others I've mentioned above.

And before anyone says "Yeah but those are the same guys that said you MUST go SD", that's not true. I never told anyone that you MUST dump your MAF system and go SD. I've always said that you could tune past a maxed MAF with PE Tables - been saying it for years.

Ski, it's my buddy with the 383 MR/AFR that currently wants to jump to SD. He would tell you that it is me that is saying "hold off for the time being". (But I do look forward to comparing both with actual time slips as a definitive acid test).

This whole %DC issue is not unique to MAF, it's works on the SD ECMs and calibrations of that vintage for batch fire.

As for the swapping a Miniram (pity you don't live close, I'd volunteer mine), you would then discover a relation with peak HP adn RPMs (something I am noticing myself). I'd say that for a "similar engine", you can use a smaller injector on a "torque" oriented intake like a TPI System vs. a high revving oriented intake like a Miniram. (Superram is in the middle - more than TPI, less than MR).

The higher revs really shorten the amount of time you have left to get your "business done".

black87c4

question - if an injector is static, does that mean that it can't provide anymore fuel or just that it's running wide open and will fail soon? If static means that it never closes but is still capable of moving enough fuel could this explain why ski could move the ratio to below 12.x:1 ?? I would think that an injector that's wide open all the time could provide alot of fuel especially if the pressure is turned up, thoughts ??

ski_dwn_it

Glen I fully understand what you are saying, but although rrob, yourself, and trax etc are telling me something, doesn't necessarily convince me that I am static. No disrespect, I appreciate your effort and I'm sure people are learning from this thread...nevertheless....I have corky on my other shoulder that has been running cars in the 10s, and low 11s for years, with absolutely no tuning skills as far as these ECMs are concerned. Don't get me wrong the man is a wizard, coupled now with my experience and tuning ability, we could be a dangerous combination.

I still can't get past this point. How can he be PIG rich with the Famato chip if he is running out of injector? And Grumpy said if you would see an injector go static, you would never run one there again....sooo I am assuming, since I have never witnessed that occure that the spray patter that the injector is designed to have would be all hosed up, efficiency would be WAY down etc, etc, and I would probably be running about 1 or more sec slower.

AFR is AFR....I would be more willing to cave if I came into my AFR from the lean side, and had to keep increasing the % change AFR vs RPM to get to my desired 12.8, then I would figure I was FORCING the injectors to perform there and yeah most likely I would be maxxed. But the exact opposite is very true and reflected on corkys as well.

I know you are probably all about to say, screw him, let him go if he isn't gonna listen....but before you do, realize I am lot just being stubborn and if I just say, yeah your right, get some 36# injectors, tune them etc and run equally as well, we will not understand what is happening or why I am able to support the HPs.

let me ask you this....before I posted here, if you were asked without knowing my ET/MPH what HP 24# injectors could be taken to, what would have been your replies? I would guess maybe 300Rwhp. Not trying to make anyone look foolish, just trying to point out we are all learning here, and I am not fully convinced YET that I am static.

My new shifter cable that broke at the last track should be in today for replacent, I will put my exhaust on and try to get you all some data that will be helpful in figureing this out. I want to know the bottom line as well. Several good things have come out of these threads.........keep it coming.

RBob

iTrader: (1)

Yes I would expect you to run that strong. As I have shown 26#/hr * 8inj is enough fuel for ~462 HP. As long as they are on all of the time.

Checking Corky's engines FP at idle with the vac line connected will show lower gauge pressure. This is because the FPR is manifold pressure referenced. He is really running a FP closer to the same as you run, as you checked yours with the vac line disconnected.

A port injected system manifold references the FP so that the fuel pressure drop across the injector does not change as manifold pressure (or vacuum) changes. (Although LS1's in Vettes do not and the code modifies the BPW in order to compensate for this).

The danger of running static is two fold: first is that during the transition period the injector is not opening & closing properly. It can beat itself to death and/or deliver inconsistent fueling.

Second, there is no margin of error. Any additional air flow (IE: cool low humidity air at sea level, reduction in intake tract restriction), and there is no additional fuel available to maintain the proper AFR.

RBob.

Grim Reaper

Yes, the Injector should be more like 26.1 for Ski's 24SVOs @ 45 psi, but the point Eric is raising is still valid. The $6E is "batch fire" not Sequential as Eric so kindly points out.

JDEStill errored in using 1=SEFI, he should have used 2=Batch. Also, look at the temperature JDEStill used "80*F". Use the coolest ambient air temperature you intend to operate. If you will operate the car in the spring or fall with 40*F temps (or even cooler), you should use that. Ski, humor me, just change those numbers and see what happens. You will now see JDE's formula starting to correlate to the actual data which RBob has explained so well. This is ignoring the "subjectiveness" of the 85% Volumetric Efficiency as well.

When someone sizes an injector, you should consider the most extreme situation of operation, not the most favorable. Heck, you can run 19#s (or even smaller) if you never booted it.

SATURN5

RPM BPW Time Difference
2200 11.67 27.3 +15.63
3475 14.31 17.3 + 2.99
4150 13.85 14.5 + .65
4525 13.43 13.3 - .13
4900 12.74 12.2 - .54
5125 12.52 11.6 - .92
5075 12.48 11.8 - .68
4975 12.67 12.1 - .57
5075 12.41 11.8 - .61
5275 12.13 11.4 - .73
5300 11.87 11.3 - .57
5450 11.23 11.0 - .23
5825 11.03 10.3 - .73
5850 10.57 10.3 - .27
6075 10.42 9.9 - .52
6175 10.39 9.7 - .69
6300 10.24 9.5 - .74
6375 10.08 9.4 - .68


Okay.... my thoughts..

Since it appears the Ski is going static @ ~4200 RPM, I thought I would do a difference in time avail to PW.

Since the accepted opening of a SAT injector is ~ 1ms he is only short of fuel during the initial opening, after that since the injector is @ 100% the difference in time is under the "normal" time required for the injector to open. Hence he is making up for the "lost" time/fuel by being static.

cheers, Bob

ski_dwn_it

You guys are giving me a head ache.....LOL.

OK say your formulas are right.......I played with the spread sheet the other night and did notice that the system was set to seq, when it should have been batch....anyways, let set aside the formulas for a second if we may......

How do you explain Corky's AFR being pig rich and my controllable AFR? I would say you guys have me convinced and I would order a different set tonight, but that is still naggin at me that maybe there is something else missed.

Can someone explain this?

Grim Reaper

Don't go out an buy a set of 30#s immediately. There are alternatives such as increasing fuel pressure to 55 psi (which will make your SVOs behave like 28.9#s).

The "recommendation" of not exceeding 50 psi is for the stock fuel pump as high pressure seems to prematurely kill the fuel pump (which seems to happen on it's own any way).

If you had a good fuel pump (not Holley), then you could easily run 55 psi and that would "just enough" to keep you in the "safety zone".

Also, increasing fuel pressure on a smaller injector does not make it behave exactly like a larger rated fuel injector. The reason is the vacuum line on the regulator is always altering the fuel pressure. I have done some testing and investigation ion fuel injectors and fuel pressure. What I have found is that increasing fuel pressure makes a smaller injector seems to make the injector "bigger" more @ WOT (where the vacuum is nil). But at part-throttle, the injector behaves "smaller" due to the vacuum line.

In some respects, I prefer the characteristics of a smaller injector with higher fuel pressure than a large injector with low pressure.

Save some money right now, and do some "testing" with higher fuel pressure while adjusting your fuel injector constant (plus some other tweaks). You don't have to buy new injectors now, you have alternatives as the ECM is not commanding "a PW that is far in excess than can be obtained".

If you were pulling more revs (i.e. 6,000), then I would lean to 30#s. But at 5,400 rpm, you have alternatives IMO.

Corky should also look at increasing his FP while altering his Injector Constant.

Good luck.

ski_dwn_it

Here is the plan of attack, so we all have some good data to go off of and there are some reserves about me co-operating with regards to data, sorta have my hand tied now with the car on a lift, headers off, shifting cable broke (picked up my new one today at noon from NAPA). But I will get my car put back together. The only concern I have with putting a whole lot of effort into tuning the AFR to a different level, is the exhaust is definately hurting me a little and I will not run with it at the track any more. So maybe I will leave my stock O2 out of the car and replace my stock unit with that of the WB.

I saw a post that Craig Moate, is working on a patch to log data with his WB02 via the loggin computer. That would be cool.

I am able to log with my WB, can't say from who or I will get killed again like last time for someone elses vendeta I will try to get some good runs in, I can't go crazy though at ~$8/gal of toluene and the added cost of reg 94 octane using about 1 gal per run, it costs me quite a bit to run this critter under WOT.

Honestly how many of you think I have any ET left in this things and someone asked earlier if I knew for a fact that this AFR was best, the answer is no, my 350 like it there and my first track appearance, back a few weekends ago was primarily just to see where I was at, then go from there. It turned out pretty good, and that is the experience I am reporting from.

That is also why I want to get to a dyno to get some good dyno numbers....I might have a 10 sec car all day long in any sort of weather, who knows?

Time to make some calls.....talk to you later.

Jesse

kevm14

Exactly. This just isn't a problem on the street, but that doesn't mean it doesn't exist. Put the car on a dyno with a brake (to hold drum rpms and let the car run through the whole load range), and you would damn well see 255 g/sec before you hit PE (depending on your PE TPS enable %). So I guess the argument is partially Ski saying "I don't care, it doesn't affect me," when others are saying "So what, it's there and you are ignoring it for the wrong reason."

kevm14

This is just the opposition's point though. You're going on that assumption. No one should be refuting the results you are seeing. Good for you. But don't make blanket statements about the system as a whole based soley on your experience (and a few select others, like Corky's 406). And you don't have to be going 120mph...familiar with gears? What is your PE engagement point? What happens if you hold the throttle 1% under that threshold and wind the car ALL THE WAY OUT in, say, 3rd gear? This is the area I think RBob was trying to address. If you drive your car in such a way as to always be in PE before the 255 g/sec is hit, that's your deal. But not everyone will drive that way. And, imo, the system has a flaw there.

kevm14

The thing that has me confused, though, is that he says he moved his AFR up to 12.8:1. Even if they were static before, they can't be now, since he decreased his PW...
Time to flow these SVO injectors and see what they really do at a given FP.

kevm14

Does anyone know what affect compression has on BSFC? Seems to me that it would decrease with an increase in compression. Ski's motor is pretty high compression, so...

RBob

iTrader: (1)

Ski never said at what RPM he saw that it was richer.

And yes, I agree that it would be a good idea to have the current injectors flow tested. One reason just to know, and the other to make a better selection of how much larger to go.

RBob.

ski_dwn_it

Kevm14,

Your making some bold statements that are a little outlandish....First I never disagreed that you would run out of adjustment with MAF if you could get over 255 g/sec without envoking PE........go back and reread my posts. I was just pointing out its not necessary to worry about it since you can have PE to adjust the AFR once you do experience 255 g/sec, then I don't big a hairy bone what the air coming in is, I just add or subtract fuel from the PE AFR vs RPM. Simple as that, this method I am not claiming fame to, I never read that here, but people said it a known method. Not refuting it was, so you don't have to dig up 100 posts with it explaining what I said.

Secondly, don't ask me stupid questions like if I heard of gears? Yeah I'm gonna swap out gear to check to see if I am able to reach 255 without envoking PE....lets get real.

We are talking real world situations here. You are used to driving around a 15 sec car and yeah it probably takes you 1/2 mile to get it going 100 MPH.....if you drove mine you would clearly see that at 1/4-1/2 throttle it would scare the living daylightouts out of you then you would realize that its not necessary for daily driving, nor is it necessary to even get close to 255 g/sec to pass a car at 80-90 mph or go up a steep grade etc. And yeah you would be going well over a 100 MPH when you reach 255 g/sec trust me. 1% throttle and wind the car all the way out, LOL. Yeah I would be going about 147 MPH by the time that happen, with 3.07 gears......maybe you, not me. I don't care to take out a whole family and leave mine behind....and how many times are you doing 100+ on the road and looking for driveability???? Real world situations fella.

Realize, your nearly 4 1/2 sec off the pace with me in the 1/4, that means you would be about 1/8 mile when I cross the finish line.....so before you start poking think next time.....

You did however make a good point about compression that I have been thinking out, but I think its addressed or accounted for in the efficiency variable, and that is why I don't put too much stock in the equations.

Here is another.....the toluene mixture that we run is from what I read much denser than regular fuel, therefore you don't need as much to achieve the same AFR.

ski_dwn_it

For a car that if your at 3/4 throttle and all it really does is make some extra noise....yeah I can see your point.....try that in this thing...you won't care if your in PE or not, all you will be doing especially with street tires is trying to keep is going straight.

Dude your talking about two entirely different animals, you experience is based on what you drive and is nothing even close to what I'm dealing with.

**** the guy that was at Keystone with Corky, took his 2wd chevy truck with a cap and bed full of tools out to see what it would do. It turned an 15.8 the first time out. We laughed our azzes off, that is cookin though for full size stock truck.

ski_dwn_it

Rrob,

I was rich through the entire RPM range, as I said in an earlier post, if I have approached my AFR from the lean side, I would think that maybe I was running the injectors to their max and forcing them to over perform, but I easily just reduced the % chg to AFR using PE and they came right into the 12.8 range.

That is the only hangup I see with the formulas, maybe its a combination of the efficiency, compressions ratio, FP, type of gas and overall SR system that allows us to do what we are doing, and do it well. I am posiitive I will see a 10 sec run this season. Christ that was only the first time to the track and this engine doesn't even have 10 good WOT runs on it yet, no synthetic oil etc. Its just a baby.

Each time I run it it feels stronger and stronger...its only a matter of time.

RBob

iTrader: (1)

I just had a thought, it appears that you are data logging in the high speed baud rate (8192). In order to do this with the '165 ECM you need to put the ECM in another mode (diag or ALDL mode or such) via the 10K resistor.

This causes the ECM to change it's operation.

Maybe the PW's you recorded and posted are not the same as they are when not data logging?

Has anyone gone through the code yet to see what changes the ECM makes when in 10K mode?

RBob.

ski_dwn_it

Rrob,

You know I have been meaning to ask you guys this......I notice a pretty big difference in power when I have that data loggin, like it runs even richer, but I always thought it was me......DAMN I wish I would have asked you guys this before.....

My best runs thus far are with the computer not connected, then I wish I would have had it connected. Do you think it could be hurting my performance with it connected during these runs?

Darn this is something I have always wondered about. Just so you know I am using the Ease hardware and software, before with the Craig Moates, I know it had the 10k resistor, not sure about the ease, but I know it needs to be in there for the 165 ecm to communicate.

Thanks Rrob, I should have mentioned this before, but always planned on doing a search for the information, just kept slipping my mind

Grim Reaper

With my Diacom+ on $6E, ALDL Mode is the one you need to use (it has the least effect on the operation of the ECM). Diagnositc has the greatest effect and should not be used. But they both affect the ECM, but ALDL mode has the least effect as I recall.

No worries, try both and you'll immediately see which one has the greatest effect.

Unfortunately, there is no "Normal" mode like the $8D/7730 where it "reports but has no override or affect on the operation of the code".