Injector Opening Times

[JDEstill]

BTW, one of the questions I believe you asked earlier is why the use of the gas law is a selling point. Back when the FAST was originally released, their main competitor was probably the DFI 6. That old clunker required you to enter in the pw you wanted at every operating point. The new FAST unit was instead doing air flow calculations with a VE table and calculating the required pw. The Haltech was probably another big competitor, and if I remember correctly the user had to tell it pws as well. TEC-II, something similarly bad. The FAST was a huge jump up over those guys, and the methodology of calculating the pw (which uses the gas law) was why. So to me, trumpeting that (which is also where the "true" speed-density claim came from) is 100% valid.

John

 

[norbs]

That old clunker required you to enter in the pw you wanted at every operating point.

John

Those clunkers were simple and with the right numbers they did pretty good back then and even today !Now with the use of in expensive wide bands they take the guess work out of it. Getting in to the depth if its true 100% ve or not I don't really think it matters ......The systems work the cars run well.

 

[bruce]

I really don't have time to do any searching on this, so perhaps you can tell me Bruce, what are the steps involved in, say, the BPC or BPW calculation for a GM speed density ecm? 749, TPI, whatever. I'm betting the gas law is in their routine somewhere. It might not be obvious, but I bet it's there. So tell me how they figure up the inj pw to command. They do some kind of A x B x C x D = pw, so what are all the A, B, C, D, etc they use to get there? If that P4 document doesn't give the right equation like you say, then what is the right one?

While I do appreciate your response, the original guestion is:

*Does anyone have any facts or data to prove that using a Ideal Gas Law, such as F.A.S.T. claims, does offer any better fueling than a BPC, or BPW calculation?, considering that the injector opening time, is just a fudge factor.*

As far as the P4 document.
In the P4 document, they talk about a inj constant, to use the inj constant in an ideal gas calc, you need some sort of engine displacement entry, to actually be able to figure out how much air the engine is pumping (ie VE). In the P4 document the code actually uses the BPW vs EGR flow, for the injector size.

Just to define what may be GMese terms.
BPC, is the TBI fueling where they typically don't use any IAT, or MAT for fueling.
BPW, is an Ideal Gas type fuel calc, but uses a BPW in lieu of an injector size, and cylinder displacement. The neat part of the 58 (syclone) code is that it uses a MAT, and you can see how much of a fueling correction there is based on MAT).
Then in like the 8D code it's an Ideal Gas Calc, and uses, an Inverse IAT Calc, inj flow, and cylinder displacement.
And in all of them they use a correction for injector opening times, based on voltage, and while typically 128'd out, there is also typically a fueling correction based on fuel pump voltage.

 

[bruce]

Those clunkers were simple and with the right numbers they did pretty good back then and even today !Now with the use of in expensive wide bands they take the guess work out of it. Getting in to the depth if its true 100% ve or not I don't really think it matters ......The systems work the cars run well.

Like you said, *pretty good*.

If you want to swing by some time, I'll take you for a ride in my car, and with a constant PW, show you how much a WB can be off. While commonly ignored, timing, and injector timing (with SEFI), can push the EGTs, and AFRs all over the place. The larger the injector, makes for a shorter PW, and the ability to push the injector timing into the *sweet spot*. As you get into the high load conditions, the effect lessens, ie PWs get long, and the time between cylinder fillings lessen.

While to some VE might not be really important, it's more telling then how much boost you're running. VE actually tells you how much air the engine is using. With that info, you can tell if at 30 PSI you're actually passing more air thur the engine then at 28 or not. Or how meaningful what MAT change is to how much air the engine is actually using.

 

[JDEstill]

I guess I'm still not sure what your beef is Bruce. It sounds to me that you just don't like the way people tune their cars more than anything else. The way the FAST has implemented the VE table is similar to GM - once you have good numbers there, you should never have to touch it again (unless you are changing hard parts). It's an engine characteristic, not a tuning handle, for either system. Now if people don't use it that way, it's not the fault of the FAST. Or for GM for that matter. Don't people mess with the VE table when they're doing chips for their OEM speed density systems? Are the values they come up with 100% correct? What makes what they are doing any different than a FAST user?

I'll agree that ideally the VE map should be 100% on the money, but if it isn't, if it's only within 95% of the actual value, so what? All that ultimately matters is getting the right amount of fuel in there, and if some tuning handle somewhere else lets you do that, then it doesn't matter.

If GMs TBI code doesn't use MAT at all for its fueling calculation, then I say that is less sophisticated than the FAST or DFI7. You cannot properly determine the airflow in a speed density system without it, and if you don't know the airflow then how does it know what the fuel flow should be? If that's the case, I would guess they are fudging it with the BLMs. Heck, a BLM range from 105 to 150 gives you what, plus or minus 20% fuel? That's a huge range that can cover up a lot of inaccuracies. If the TBI code doesn't use a MAT then I am confident in saying that a FAST is superior to a BPC calculation, without knowing exactly what that is, just because you need to know the MAT to do it "right".

I can't quite tell, but I think you also implied that the BPW calc doesn't use a MAT, exceptions being for some systems like the 58 or 8D code? If that's true then the BPW calc would not be a true speed density system either, and I would consider it to be inherently less accurate than a FAST (or 8D or 58).

With regard to injector opening times, I may have referred to that as being a fudge earlier, but that may mean something different to me than to others. To me it just means something that corrects for a deviation from perfection. In this way the VE table is a fudge, since it is correcting for changes in cylinder filling at different rpms and manifold pressures. Perfection would be getting exactly 231 cu in of air at manifold temperature and pressure into the cylinders every 2 revs of the engine, no matter what the rpm or boost level. But that doesn't happen, so we need a fudge factor - the VE. Same thing with injectors. It would be nice to have a 1 ms pw give exactly 10X the fuel as a 10 ms pw, but again that doesn't happen, so we have to take it into account and have a correction. So what? You say that GM has a table for this. So why harp on FAST for having this correction. Or do you just not like that fact that FAST uses a constant instead of a table?

John

 

[bruce]

I guess I'm still not sure what your beef is Bruce.

Is this forum so out of control, that when someone wants to have a discussion about something, the first thing up, is assuming someone has an issue. Never, mind it seems the answer is apparent.

The TBI code is basically, a *do enough to get past the EPA, and have fair drivibility* set-up. So in a basic set-up like that, yes, one might consider the closed loop portion as fudge, just to get the system passable. When you get to the cars (8D) code, then that same closed loop is just a final trim on the actual running of the car, to allow for variations from the prescribed maintance schedule, and variances in gas, etc.. If one wants to use a TBI level of code, then fine, but to use a sophisticated Ideal Gas Law system, and reduce it to the level of a *just get by system*, really doesn't make much sense, IMO.

Yes, while fueling and timing are still estimates, the closer you get to being able to optimise filling the needs of the engine the more HP, and reliablity you will have.

So much for,
*Does anyone have any facts or data to prove that using a Ideal Gas Law, such as F.A.S.T. claims, does offer any better fueling than a BPC, or BPW calculation?, considering that the injector opening time, is just a fudge factor.*

 

[gewroo]

It's nice to some some people really "get it". Nice John!

So much for,
*Does anyone have any facts or data to prove that using a Ideal Gas Law, such as F.A.S.T. claims, does offer any better fueling than a BPC, or BPW calculation?, considering that the injector opening time, is just a fudge factor.*

How about this instead: *Does anybody have any facts or data to prove that using a BPC or BPW calculation such as Bruce claims, does offer any better fueling than the Ideal Gas Law?, considering that Bruce thinks that injector opening time is only a fudge factor.*

 

[Ricky Trussell]

Thread Jack

Can you guru's take a break from this and look at this thread??
http://www.turbobuick.com/forums/showthread.php?t=169456

It should be a simple fix for experienced tuners.

/thread Jack

 

[GS70350]

Bruce just asked a legitimate question

I dunno Bruce, I have no comparable experience in the tuning of the DFI, stock ECM, Motec, etc, but I do think that your point about injector timing and other seemingly small factors could be manipulated and have a worthwhile effect on driveability, performance, and overall efficiency, and therefore deserve a closer look, or perhaps some out of the box thinking to make progress on the matter.

HOWEVER
From what ive read on these boards, youre about the only one who is really capable of testing these things at the moment. If i had a bench, a few ECMs, and a few months to learn the code i would be right there with you and would love to discuss topics outside the general realm of vehicle modification and performance. I dont have the testing equipment, but i have ideas and ill test the concept. If i prove the concept works, then i know that in the future i will be able to eventually put more time into utilizing the idea, or making it a reality.

My favorite topic about cars is the ICE, and once you narrow that down, is to try and find ways to increase the efficiency of the system. My budget is lesser than yours i guarantee it, so the extent of my experimentation will always be limited, but i always pay close attention to what you do and record your results (when you post them) in my database, and I admire you for your work.

One thing ive realized however, is that once you move on to topics of this sort, you wont get much out of anyone that is of any help at all. Most people dont focus on this stuff, they focus on bigger turbos, intercoolers, need more injector, different heads, etc, all because the tuning is more or less "standardized" in my book. You just have to end up doing it alone and coming up with your own answer to your question.

It doesnt matter what engine it is, people tune them the same way. The general concensus is that cold dense air/fuel charge is best for power, cold thermostats are best for power, injector timing has no real effect it all goes in when the valve opens anyway, etc. Thats about all you can expect to hear, and dont expect to sway everyone by showing them another way. This is the way things have been for years, and its the way things will keep going for a long time to come unless some people step up to the plate and change that. These concepts are just too widespread to get people to think twice.

 

[JDEstill]

Is this forum so out of control, that when someone wants to have a discussion about something, the first thing up, is assuming someone has an issue. Never, mind it seems the answer is apparent. *

Sorry Bruce, bad choice of words on my part. I wasn't trying to be snippy. Instead of "I'm not sure what your beef is" I should have perhaps said "I don't know what issues you have", or something similar. I sometimes have trouble getting to the root question that you are trying to ask.

to use a sophisticated Ideal Gas Law system, and reduce it to the level of a *just get by system*, really doesn't make much sense, IMO. *

I don't consider a FAST, DFI7, or OEM speed-density setup to be a "just get by system". Why do think a FAST is a "just get by"?

So much for,
*Does anyone have any facts or data to prove that using a Ideal Gas Law, such as F.A.S.T. claims, does offer any better fueling than a BPC, or BPW calculation?, considering that the injector opening time, is just a fudge factor.*

I would be happy to discuss some facts. Tell me how the OEM gold standard BPW calculation works (as I asked several posts above) and I'd be happy to look into it and compare it to how the FAST works. The only reference I have is the P4 document, which you say is not valid, and I'm not about to spend several hours on the internet trying to hunt it down, esp. when you can apparently quote it to me quite easily.

John

 

[norbs]

This is getting too technical , put the numbers in the ve table and be done with it. The fast and dfi systems have run in the 7s in the 1/4 mile. They do work just fine, and no need to write "code" for years. I am done with this thread........