Timing advance to maximize cruise fuel economy - 460 Ford Forum
Engine Tech A place to discuss all 385-series engine tech and theory.

User Tag List

 1Likes
  • 1 Post By PSIG
 
LinkBack Thread Tools Search this Thread Display Modes
post #1 of 11 (permalink) Old 03-23-2019, 08:18 PM Thread Starter
Junior Member
 
Join Date: Jun 2011
Posts: 36
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
 
Timing advance to maximize cruise fuel economy

Significant changes to my 460 prompts me to ask some more involved questions than usual about the details of the optimal timing curve for my motorhome version of the engine. To repeat the details of my configuration, about 10,000 miles ago I had to replace the stock engine with a ProMar crate remanufactured stock engine with cast iron heads, high temperature valve seats, and a Melling MTF-3 cam with double roller chain and cam timing set to 2 degrees advanced. The Melling MTF-3 specs are 292 degree exhaust duration and 282 intake, exhaust lift is 214 and the intake lift is 204, lobe separation is 112. Smog equipment has been removed, the intake is an Edelbrock 2166 non-EGR Performer, current carburetor is an Edelbrock 1406 (tuned by Bob’s Carburetor Engineering), Hedman long tube headers go to 3” single exhaust feeding a 3” inlet/outlet 6” diameter and 30” long Magnaflow muffler (no catalyst). The ignition is DuraSpark II (recurved and rebuilt by Scotty) with a Crane Hi-6S multi firing CDI box and 0-20 degree variable retard, and Crane Fireball LX-91 coil. The transmission is a C6 automatic with Gear Vendors Overdrive and Hughes towing converter. The 158” wheelbase, 24 ft. motorhome has a 11,000 pound GVWR. Rear axle is 4.56:1 and the tires are 8.75R16.5LT giving a measured 2342 rpm at 55 mph, 2550 at 60 and 2779 at 65. Therefore, the engine cruising rpm is the band from 2300 to 2800 rpm and I am especially interested in maximizing the fuel economy of this configuration!

The unique new opportunity that presents itself is the acquisition of a Fitech Street Go EFI 400HP system to replace the existing Edelbrock 1406 and a CB Performance Black Box programmable ignition controller. The Fitech makes it possible to tune the AFR during cruise to 15.0:1 and the programmable ignition controller, with its MAF vacuum sensor, gives full control of the ignition timing. In addition, the Crane Hi-6S fires a series of spark pulses for each ignition event at cruise rpm that gives a total spark duration of 20 degrees (crankshaft).

Now for sometime I have been studying a number of engine design papers and articles about the relationship of timing at lean cruise conditions for maximum economy. As most of you know, lean conditions require additional advance to fully consume the charge before the appropriate point after TDC for a clean power stroke. The amount of advance depends on compression ratio, spark burn rate, combustion chamber design, intake and exhaust flow parameters and temperature (and probably the lunar phase). So, I think I have an opportunity to tune the timing advance in this important operating range of a more or less stock 460.

But several questions have bothered me. The Duraspark II system curved by Scotty for this engine is 32 degrees total, all in at 3200 rpm. The vacuum advance is 12 degrees. My idle vacuum is 15” at 5,200 ft. altitude and the manifold vacuum at cruise is between 14 and 16 inches Hg. With carburetor the system is just fine with overall mpg between 8.5 and 9.8 mpg. But, the mechanical advance is just a linear increase with rpm from the initial value. The total advance is clearly to give the best advance at high load and high rpm just shy of detonation. The vacuum advance is the wild card to account for the wide range of engine load variations. But when I look at engine dyne results (all I can find are SBC and BBC engines) that look at maximum power at different rpm’s the timing curve is NOT a simple linear function. It appears to change rapidly from 1000 to 2000, then slowly taper to 4000, and then change very slowly if at all at still higher rpm. Unfortunately, nowhere can I find a BSFC curve for the 460 engine with any type of cylinder head design.

So, I wonder if others in this group have looked into the “Optimal Timing Curve” for the cast iron head, low compression, towing cam version of the 460 with their dyne results?

I have thought that I might address this (without the dyno) by taking advantage of the Variable Timing Retard feature of the Crane Hi-6S. The Retard Control is mounted in the E350 cab and quite accessible while driving. Its dial is marked in 1 degree increments. I have calibrated the numbers while monitoring the timing at idle speeds. For the experiment, I would also have to calibrate the vacuum advance canister. Then, I could add, for example, 10 degrees of advance to the initial (idle) timing - and then remove those 10 degrees by retarding with the Hi-6S control. Then, finding a flat section of extended highway ( probably the Hwy to Burning Man/ Black Rock Desert) and fixing the Fitech AFR at 15:1, and cruise control at 2350 rpm, I could vary the timing with the Hi-6S while monitoring the manifold vacuum. Finally, I have a high gain electronic stethoscope to monitor for the onset of engine knock, should I venture into that territory. Running the experiment at several rpm levels might answer the question of best timing advance at a fixed AFR. Additionally, It would answer the question of whether or not the maximum vacuum level can be used to optimize the low-load timing curve.

If I can get these numbers, I will load the digital spark map into the “Black Box” and put the instruments away!

Any comments (short of outrage) welcomed! As always, too long…
FrankGRUN is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 04-10-2019, 04:00 PM Thread Starter
Junior Member
 
Join Date: Jun 2011
Posts: 36
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
 
Additional Data

I have been disappointed to see that this effort has triggered no response from the group. However, this forum has a long history and I have ofter been able to return to the search feature to refresh my memory about some detail. Therefore, and in the hope to stimulate some discussion, I have decided to add some of the information I have gathered on the subject. I'll add proper references and pdf's of papers if requested.

As I indicated above, with a locked distributor (I'm going to use the Ford TFi distributor from the 88-96 460's using the Hall sensor trigger output) and the CB Performance Black Box Programmable Ignition, I have the ability to add a full Spark Timing Map. Typically, these are generated on a Dyno, but I don't have access to a Motorhome compatible one in Reno, so I have to develop the full tune on the road. Best would be to get a Dyno tune for the 460 with similar use application, camshaft, heads, etc. Fortunately, I have found one timing map for a build similar to mine.

But first to the background data. A variety of classic engineering texts demonstrate the "optimal" timing for a cast iron head, 4-stroke, gasoline engine using data from the GM Tech Center on experimental engines. The enclosed figure labeled Torque vs. Spark Advance at WOT. As you can see, the the torque max is measured at wide open throttle by varying the spark timing at a constant engine rpm. A second important figure, shows torque measured against spark advance for several different constant RPM values but also noting the onset of light knock. From this figure we can take the KL-MBT value (Knock-limited Maximum Brake Torque) at a given RPM. Finally, for this set, the next Figure plots the torque for an optimal spark advance curve vs. the normal curve, showing that approximately 15% of the possible torque is left at the table by the non-optimal curve. BTW, the optimal curve is calculated by the measured KL-MBT value and subtracting 2 degrees for a knock margin.

Now, in the next Figure I have taken a data set from another V8 engine (Not Ford 460) that studied MBT spark advance for various loads represented by manifold pressure in KPa units and added the data from Scotty's recommended curve for my engine (12 initial and 32 total in at 3200 rpm) to the plot. I have added a second curve for Scotty's recommendation and added 12 degrees for maximum vacuum advance. Notice how closely Scotty's no-vacuum curve parallels the 100KPa curve and the Mad Porter + Vac curve parallels most of the 50KPa curve from the detailed study.

The next Figure summarizes the data from a comprehensive Thesis that studied a SAAB 2.0L Turbo 4 cylinder. The Spark advance curve is the KL-MBT value less 2 degree knock margin. I have also added the Scotty derived curves to this plot. Notice that the + Vac curve closely parallels the 2 degree knock margin curve save below 1500 rpm and just 3 degrees advance separates these curves above 2500 rpm.

Finally, as I mentioned above, I found a full timing map, optimized from the starting base map, for a "Mild" 460 build with very similar parameters to mine. In the last Figure, I have plotted the spark timing values for three different load values, 10 MPa, 30 MPa and 98 MPa which corresponds to WOT. I have also included the Scotty-derived curves as well. However I have hit a file limit, so I'll add that figure in the next post.

My point in all of this is that I have no interest in maximum power, just access to the full available torque from idle to 3000 rpm. I still plan tp manipulate the AFR at 2-3000 low load conditions to see if the lean conditions are further optimized by spark advance.
Attached Images
File Type: jpg Torque vs. Spark Advance WOT at Various RPM.jpg (14.5 KB, 6 views)
File Type: jpg Measured Torque vs. Spark Advance for Fixed RPM.jpg (19.6 KB, 7 views)
File Type: jpg Spark Advance Map Optimal vs. Normal.jpg (12.8 KB, 7 views)
File Type: jpg Spark Timing Map at MBT vs. RPM and Load.jpg (20.3 KB, 6 views)
File Type: jpg Spark Timing Map at MBT:Knock Onset less 2 Degrees.jpg (18.2 KB, 6 views)
FrankGRUN is offline  
post #3 of 11 (permalink) Old 04-10-2019, 04:17 PM Thread Starter
Junior Member
 
Join Date: Jun 2011
Posts: 36
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
 
To continue, here is the plot from the Dyno-optimized runs for the "Mild 460 Build" that I referred to above. Again you see that the Scotty-derived curves at +Vac, closely approximate the 10 KPa plot from 2000 to 3500. However, in a situation where degrees are significant, there are substantial differences. In particular, there are surprising differences between the curves for 10 and 30 KPa (and for the 20 KPa, 40 KPa, 50 KPa and 60 KPa curves that I haven't plotted here) in the region below 2300 rpm. Also, the 30 KPa curve shows less advance that the WOT curve in the region from 2000 to 2800 rpm.

I'll also add that I'm nervous about adding a bit of onset detonation stress to my engine. I'll first try to study the effect od timing advance at a specific AFR and constant RPM on the measured manifold vacuum. I've setup a crude data logger system to help. Finally, I'll be adding the GM ESC anti-knock system with module and knock sensor tuned to the BBC 454 stock truck engine. The ground signal will be used to trigger the Crane retard by 2-4 degrees as needed.

AS before, any comments or data strongly solicited.
Attached Images
File Type: jpg Ford Mild 460 Spark Map by Dyno Tune.jpg (19.3 KB, 9 views)
FrankGRUN is offline  
 
post #4 of 11 (permalink) Old 04-18-2019, 10:17 PM
Junior Member
 
Join Date: Jan 2010
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
 
Whew.... You've done a lot of homework. The lack of responses indicates most people don't buy old 460's with the deliberate intention to improve fuel economy... that's the realm of late model vehicles with high tech engines ...like turbos and diesels.

None the less, hot rodders establish an end goal and work towards it. There are three possible outcomes: exceed the goal, get close enough and move onward, or change direction/reset the goal.

Since a 'mostly stock 460' is not a stock 460, the performance goal desired for your engine is torque improvement while obtaining maximum fuel economy. But you will want to define or clarify the specific goal... 10 mpg, 15 mpg? with the motorhome empty or fully loaded while towing another vehicle? and, at what speed?


I think most on here would agree that improvements in the intake, cam, and exhaust will certainly wake up a stock 460. Once an engine build extends beyond efficiency improvements, physics dictates more power (torque) requires more fuel. Most people build engines for a specific goal) and will go after the best bang for the buck that is currently available. The budget and value conscious apply the 80/20 rule while others go all in and take out a second mortgage.

Regardless, MBT is the correct timing curve. MBT is determined on a dyno under a wide variety of controlled conditions and the data is logged and analyzed. Various changes are made and the cycle repeats until the best results are achieved.

Restated: to determine the ideal MBT for a non-stock build requires dyno time (lots of dyno time)... not on a chassis dyno in an open air shop and not on a public road.

Since most of us do not have that kind of disposable resources, hot rodders develop a conservative tune (meaning staying away from detonation) and they run it, making minor adjustments as needed, when needed. The possible 5 ft-lb improvement could cost a new piston.

[FWIW Knock sensors are a band aid for the unforeseen... like a tank of bad gas. If an engine bounces off the knock sensor, something is wrong and needs fixed.]

Besides basic intake, exhaust, and camshaft mods, a good efi setup (wide band O2 with self learning) and a conservative ignition tune and your 460 is ready to work efficiently. Then, fuel efficiency improvements can be derived from the rest of the chassis.
JimL is offline  
post #5 of 11 (permalink) Old 04-19-2019, 04:00 PM
Junior Member
 
PSIG's Avatar
 
Join Date: Feb 2015
Location: Seattle area
Posts: 7
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
 
Cool

Hi Frank(?). I only pass through here occasionally over the years, and just happened to see your posts. You have a much better grasp on timing than most with your research, but I do have a few opinions and observations I will throw at you on this topic from my experiences in engine tuning to kick the conversation off. I am pleased to see you recognize the ignition as a critical part of the entire tune, and what enables the air and fuel to do their job efficiently for any performance purpose (including economy); a fact that many overlook or purposely ignore. Engines are like trying to play the best guitar or piano in the world — it will suck if not properly tuned.

First, there is no "optimal timing curve" for any engine except the one you are working on, with the fuel that is in the tank right now, under the conditions of the moment. Many factors from variations in valve timing, to coolant and other temperatures, exhaust configuration, density altitude and 101 other 'little' things will affect best timing both overall and under specific conditions. The greatest single controllable factor is your fuel, which when known as "pump gas" is variable in grade and quality, and so is a constant enemy of consistent results or comparisons. While your research is useful, at some point you will have to go find what yours needs, using the knowledge you've gained to guide you.

You are already aware of what best timing (MBT) is, though my perception is that you connect it to detonation as a guide. If I am mistaken, I apologize, but perhaps the following will help others. Detonation (knock) detection and tuning ignition timing are two different things. While one can affect the other, knock has nothing to do with correct ignition timing. Knock is a limitation caused by other factors that can force an incorrect ignition timing in order to avoid knock. If knock is forcing an incorrect retarded timing value, then either your fuel grade is not sufficient for the engine package design and performance goals, or the engine design is not correct for the chosen fuel grade and performance goals. A very common misunderstanding is that correct timing is found just before knock begins, which is entirely false.

Detonation (knock, ping, pink, etc) is a failure to reach correct timing, through specific heat sources and/or insufficient octane/AKI, and is considered det-limited (detonation or knock limited). For example, if under current conditions the engine should have 32°BTC timing in order to place PCP (peak cylinder pressure) at the precise crank angle for best torque, but det limits the timing to 29°, it has failed to reach correct (MBT) timing. So, 29° is neither best nor correct timing (32° is), but retarding is one method to reduce or delay the cylinder pressure ("de-tune") in order to avoid det. Det is caused by heat, and so there are other ways to reduce specific heat sources and avoid det, other than retarding from best timing. Note here that none of this is preignition, nor "pre-detonation" which isn't even a thing.

Side note - detonation detection is by many methods, but my favorites are reading spark plugs and using amplified headsets, as the brain can detect anomalies and frequencies not programmable into most electronic controllers. Your knock module might be good, but only if it is tuned to read on your engine for proper response at any rpm; so verify that on your engine by another detection method before you trust it at any point. Always use more than one det detection method. Detonation and its detection are topics unto themselves.

In an attempt to be helpful, I would suggest that if you detect det during your initial tuning exercise, that you simply upgrade your fuel or apply other heat-source reductions until your curve or timing table is completed to MBT, det-free. Then you can return to the lower-grade fuel and concentrate on detecting det, taking steps (possibly including timing retard) to configure your setup to use that lower-grade fuel. Once all is happy at that level, then you can begin stages 2 and 3 of your performance (economy) tuning by testing for minimum fuel (typically around the low 16:1AFR/Lambda 1.1 range for this engine type) and then re-tuning timing in order to re-establish MBT and highest efficiency with the new AFRs, decreasing pumping losses for mileage gains. It's not the lean AFR that saves fuel directly, but the efficient use of lean AFRs allowing reduced pumping losses that gains the efficiency and mileage. Timing does that.

That's enough for now. Fair warning — tuning may be addictive. But it's a better addiction than most. Rock on!

David
The Pope likes this.

-= If it was easy, everyone would do it =-
PSIG is offline  
post #6 of 11 (permalink) Old 04-22-2019, 12:32 PM
Junior Member
 
rattle_snake's Avatar
 
Join Date: Nov 2018
Location: Chandler, AZ
Posts: 15
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
 
Interesting read. I can't offer any ignition timing related advice relating to fuel efficiency.

8.5-9.8 MPG for a 24' brick sounds pretty good so I wouldn't expect to see significant improvements coming from further ignition tweaks. I would try the EFI which should get closer to stioc at all times with it's closed loop control. Lowering the vehicle weight will always help.

Justin
72 F250
14 F250 6.7, CCLB, 37s
04 Mustang Cobra, 14psi + N20
rattle_snake is offline  
post #7 of 11 (permalink) Old 04-25-2019, 02:05 AM Thread Starter
Junior Member
 
Join Date: Jun 2011
Posts: 36
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
 
Jim, David and rattle_snake, thanks much for your comments and response! I've been buried under the hood and under the chassis of the Motorhome for the past week as I finished various mods and wiring projects to bring the Fitech online. I've finished the installation and will be running the system with the original Duraspark II/Crane Hi-6S ignition system until I'm comfortable with the operational parameters of the Fitech unit. Then I'll switch over the ignition to the CB Performance Black Box programmable ignition with a TFi distributor and the Crane. The question for me is how to develop the spark timing base map with the Duraspark II, its vacuum advance and the variable retard capabilities of the Crane Hi-6S.

Jim, you have me dead to rights here - in that there is no financially justifiable outcome to the project, its simply an addiction. I have the opportunity to set up a reasonably efficient version of my engine and match its utility to my application. I understand that an engine dyno would be an ideal solution to the problem, but its out of the question with my limited resources. This is, of course, why I have been hoping for access to a colleague's engine dyno spark timing map. My region of interest is the area controlled by the initial timing and the advance provided by mechanical (WOT) and the low load map provided by the vacuum advance. That is 1200 to 3000 rpm at the outside. This is an area I have never seen addressed in any chassis dyno curves I have seen (always start at 3000 and head on up). So neither chassis of engine dyno offer an answer for my engine. The asphalt road dyno seems the only way open to me. The Knock Sensor is just an attempt to add a margin of response if I have pushed the timing literally too far.

David, as I go back and read my comments, you're right, I was overemphasizing the detonation limited MBT. As you indicate, relying on finding the timing advance triggering the onset of detonation is a key point to know but its independent of the actual MBT timing value for a given load, AFR and RPM. I was also surprised at the number of research papers that focussed on 2 degrees less that knock limited MBT.

Your last paragraph certainly summarizes what I wanted to map out. I had completely overlooked using fuel quality as an operating variable. My problem is trying to find a measurement that directly relates to MBT given my limitations to establish variable load at constant rpm. I looked into high speed cylinder pressure measuring spark plugs, but the investment for a single unit would make the engine dyno run look like free Easter candy! The only thing I can think of is maximizing manifold vacuum at a constant rpm and load as I vary AFR and timing. I have a reasonably accurate manifold sensor capable of 32 bits output. I can link up serial AFR output with analog engine RPM and vacuum signals input to my laptop. I could include the filtered output of the knock sensor as well. The question is, is there any demonstrable relation ship between manifold vacuum and instantaneous torque?

Better stop here, my addiction is showing!
FrankGRUN is offline  
post #8 of 11 (permalink) Old 04-25-2019, 11:37 AM
Junior Member
 
rattle_snake's Avatar
 
Join Date: Nov 2018
Location: Chandler, AZ
Posts: 15
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
 
Did you get the FITECH unit that has timing control?
If you did you can lock out mechanical and vacuum advance on the distributor and have complete timing control with the FITECH. Should be able to log parameters like manifold pressure, load, AFR, short/long trim, maybe even fuel rate as you drive with the fitech itself.

EFI tuning can be a black hole, but sounds like you may like that kind of challenge.

Justin
72 F250
14 F250 6.7, CCLB, 37s
04 Mustang Cobra, 14psi + N20
rattle_snake is offline  
post #9 of 11 (permalink) Old 04-25-2019, 12:08 PM Thread Starter
Junior Member
 
Join Date: Jun 2011
Posts: 36
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
 
Justin, unfortunately, I got the Go Street EFI 400HP which is their de-contented one without timing control. At first, I was disappointed in the lack of timing control, but then, looking into it further, I realized that the FiTech timing control is only based on a 3 x 3 timing map with linear interpolation between points. For the $200 price difference, I purchased the CB Performance Black Box programmable ignition that has a 21 x 21 map. I'm just starting to delve into the Fitech capabilities and hadn't thought about its logging function. Thanks for the tip, this could be a big help! I will be mapping the current distributor timing and the vacuum advance while sitting in the driveway. For the on-the-road mapping, as I mentioned, my plan was to advance the initial timing bu 10 degrees and simultaneously retard the timing with the Crane Hi-6S. Then, while driving I could vary the timing by plus or minus 10 degrees in one degree increments. Dump the log for each run and I could have enough data to keep me out of trouble all winter!
FrankGRUN is offline  
post #10 of 11 (permalink) Old 04-25-2019, 01:13 PM
Junior Member
 
PSIG's Avatar
 
Join Date: Feb 2015
Location: Seattle area
Posts: 7
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
 
Quote:
Originally Posted by FrankGRUN View Post
…Then I'll switch over the ignition to the CB Performance Black Box programmable ignition with a TFi distributor and the Crane. The question for me is how to develop the spark timing base map with the Duraspark II, its vacuum advance and the variable retard capabilities of the Crane Hi-6S.
While it's good to do some things in steps or phases; I would avoid tuning the DSII (or any other mechanical/vacuum advance) except as a casual educational exercise, and go straight to programmable timing.* You haven't had fun until you are watching your sweat sizzle on the intake the nth time adjusting the distributor mechanisms during cyclic testing of this type. With programmable, you just test, click, test again from the driver's seat. It's certainly not just convenience and comfort, as you will get better and clearer results, and much quicker — an important consideration when stuck with the asphalt dyno.

That said, you will rapidly progress to an inexpensive controller (ECM) that combines full fuel control with full ignition control, data logging, etc, in order to read, interpret, and adjust the functions together. Using the FiTech for full control is a good way to "get your feet wet", though ease of setup and operation tends to limit the advanced control you will need to feed your addiction. *See related stuff below, as control and analysis can be in one package that suits your goals better for similar cost to the good CB ignition-only box.

Quote:
Originally Posted by FrankGRUN View Post
…As you indicate, relying on finding the timing advance triggering the onset of detonation is a key point to know but its independent of the actual MBT timing value for a given load, AFR and RPM. I was also surprised at the number of research papers that focussed on 2 degrees less that knock limited MBT.
Correct, though in your last sentence you may have interpreted the data 2° retard to avoid knock as relating to MBT value. Your statement is correct that it does not, except by coincidence on any given day and tank of fuel. You can have less than knock, or you can have less than MBT, as it would be rare to have knock and MBT coincide perfectly. So yes, knock is a limitation on reaching MBT, and has nothing to do with finding MBT for that engine package and fuel.

Quote:
Originally Posted by FrankGRUN View Post
…My problem is trying to find a measurement that directly relates to MBT given my limitations to establish variable load at constant rpm.
There are many creative ways to load the engine in order to find MBT. On a dyno is simple, predictable and stable. On the road, it can be creative driving with hills, brakes, or other drag or load; while monitoring things like MAP, RPMdot (rate of RPM change), MPHdot (commonly used by drag racers, but it doesn't have to be at WOT ), etc.

Quote:
Originally Posted by FrankGRUN View Post
…The only thing I can think of is maximizing manifold vacuum at a constant rpm and load as I vary AFR and timing.
And MAP is one of the good references, used as I described in phases 2 and 3. As-stated, there are other indicators, and some are easier than others when you have double-duty driving and monitoring. You will eventually experience police pullovers as they just have to know what the hell you're doing, looping the same highway and hill for the 4th or 14th time. See below.

Quote:
Originally Posted by FrankGRUN View Post
…I have a reasonably accurate manifold sensor capable of 32 bits output. I can link up serial AFR output with analog engine RPM and vacuum signals input to my laptop. I could include the filtered output of the knock sensor as well.
Here we go. We cannot possibly monitor and compare various responses, data, etc, while driving, with any reasonable accuracy or consistency. Very difficult and equally unsafe. The dyno guys can't either, and so plot their data on displays and printouts, often overlaying one result with others for direct comparison. Enter the data logger and analysis software, your personal live-monitoring assistant and record keeper. You can configure your laptop to do this and create/design a hardware board for all of your inputs from scratch , or you can use a system designed for it, with compatible software also designed for engine tuning.

Without going into it at this point, there are such systems available at low cost that will make a huge difference in the quality and progress of your tuning. Even with your commitment to the FiTech; these systems may be added for this purpose, or even replace the FiTech ECM for full control of FiTech hardware while assisting analysis of the effects on tune, correcting within the same unit, sometimes automatically. That's another step, and I'd suggest relaxing to familiarize with your FiTech's operation, so you're comfortable when you go to have a talk with your engine and play it like a piano.

Quote:
Originally Posted by FrankGRUN View Post
…The question is, is there any demonstrable relation ship between manifold vacuum and instantaneous torque?
Yes, and only by relationship (it is not a torque meter), but very useful for indications including relationships with other indications and factors. As MAP relates to most factors, it becomes a primary reference. Using data logs and enough coffee, the relative effects of various factors become apparent. That's where tuning really starts, with a recognition of relationships and how they are helping or harming the engine's happiness.

Yes, I am giving expanded responses to you, as it is uncommon to find individuals that not only thirst for the how and why, but are open-minded for new information and forming new (to them) connections of data and theory to help their engines perform best under any mode and conditions. Welcome to the addicts circle. You have my sympathy and support.

David

[EDIT] Fun PS: I see you are occasionally using the word "vacuum", and you may as well get used to thinking strictly in manifold absolute pressure. Everything from zero (outer space) through idle and cruise to max boost is just another absolute pressure number. At some point, it may become irritating to deal with translating vacuum. This is one reason that tuning superchargers and such is not concerning, as above atmo is just another pressure and the world does not rotate differently.

-= If it was easy, everyone would do it =-

Last edited by PSIG; 04-25-2019 at 06:03 PM.
PSIG is offline  
post #11 of 11 (permalink) Old 04-26-2019, 12:51 PM Thread Starter
Junior Member
 
Join Date: Jun 2011
Posts: 36
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
 
David, This is just the level of discussion I had hoped for in starting this thread!

However, a comment is in order about the term vacuum which rolls off my typing finger so easily! After 45 years of a career of chasing surface and interface chemistry and searching for residual organic biomarkers on other planets, all of which involved Ultra High Vacuum spectrometers and Molecular Beam Synthesizers operating in ranges from 10(-10) to 10(-14) torr vacuums, my frame of reference for pressure is the impingement flux required to establish a monomolecular film on a substrate of interest. So I must say that vacuum comes easily to me! One of these most interesting experiments (in pressure) entailed our designs of the Molecular Wake Shield in which we had to take into account the velocity (wake shield was just a large "officially inpenetrable" umbrella outside near earth orbit) we had to move the wake shield structure to outrun the the particles of the solar wind and outgassing components of the carrying spacecraft! Oh well, kPa does offer a continuous frame of reference...

My DSII plan was just to generate the base spark map, in lieu of a Dyno-based map to begin. I am tempted to contact the individual who published the "mild 460" map I referenced above to see if he could share an update. Given the data-logging capability of the Fitech, I was considering trying to correlate the digitized MAP and TPS readings at a constant (more or less) RPM, Load and AFR with the manually adjusted timing. I thought that the use of a flat and straight stretch of highway in the Nevada Desert could be a useful constant load device. I'm also assuming that maximum instantaneous torque would result in a minimum throttle opening and minimal manifold pressure for a given timing advance. It appears that straight and level stretches of up to 7 miles are accessible. Of course, there is always the runway at Area 51... Of course, after each run, I would have to dump the data log from the Fitech to the laptop, for later analysis. Given the fuel capacity of the motorhome, I could do approximately 30 experiments before replenishment. I was hoping I could handle law enforcement with a few cold brews, carefully encapsulated, and stored in the RV refrigerator.

With vacuum and absolute manifold pressure for all!

Frank
FrankGRUN is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the 460 Ford Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in













Similar Threads
Thread Thread Starter Forum Replies Last Post
A Completely different approach- Fuel economy build... blizzardND Engine Tech 61 10-24-2018 07:25 AM
Ported vacuum confusion! Advance and EGR? Cold start advance?? YachtOnWheels Engine Tech 0 03-08-2016 01:13 AM
Air Fuel Ratio Target for Cruise Economy with Edelbrock 1411 Calibration FrankGRUN Engine Tech 6 08-09-2014 08:45 PM
1997 F-250 fuel economy. the_patriot2014 Engine Tech 16 02-20-2014 12:07 PM
Building a 351-W for fuel economy junkyardjeff General Tech 7 03-19-2011 11:18 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome