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PostPosted: Wed May 31, 2006 12:34 pm 
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Hi Guys,

Based on the info you both have provided I think my trucks are going to be running awesome! If I understand correctly, by tuning the pop off adjustment on the injectors I am effectively changing the fuel pressure that the cylinders see. It sounds much like the nozzle on a hose. I would imagine there is a point that the volume the pump is putting out must be increase to cover the duration the injector is openned. It's probably safe to assume that my stock, normally aspirated engine will never need the additional volume/pressure from the pump. Please keep the thoughts coming. I and everyone else are learning from you guys.

Thanks again for all the input!
Joe

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PostPosted: Wed May 31, 2006 2:17 pm 
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DEVILPUP wrote:
...I would imagine there is a point that the volume the pump is putting out must be increase to cover the duration the injector is openned...

Keep in mind that the "duration" is controlled only by the pressure that is supplied by the IP, at least on the old-technology diesels like ours. It seems counter-intuitive, but the pop-off pressure is higher for the turbo-D...perhaps some other reason than amount of fuel.

Jack

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PostPosted: Wed May 31, 2006 4:45 pm 
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DEVILPUP wrote:
If I understand correctly, by tuning the pop off adjustment on the injectors I am effectively changing the fuel pressure that the cylinders see.


Let's say you have a truck with a considerable amount of miles on it (200k or more), is it recommended to have the diesel fuel injectors rebuilt before you set the pop off pressure for them? Would you still see an effective change in the fuel pressure with injectors that have never been touched in a 200-250k mile lifetime? Just trying to learn more.

Salvy

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PostPosted: Thu Jun 01, 2006 6:50 am 
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Hello everyone. The duration of the injection is controlled some by the injector pressures. The fuel quanity adjustment screw is a major factor with duration of injection.......

Salvy.....a little story for you........I just purchased another 82 Luv showing 204K miles.....it was smoking, power was down, and skipping under load.......I was told the injectors had been cleaned and set???......now, when I got it home I quickly (meaning not thorough) did some cleaning, put in a set of injectors (pre set and cleaned), ruff set the timing...........fired her up and went for a ride........excellent power, no skip, and could hardly make it smoke under load......still need to adjust the valves and install a new timing belt /optimise the timing...........I looked at the old injectors and the tips were clean, checked the pop off........showed from 1250 to 1325 PSI and did not drip till over about 700 PSI........these are tipical numbers of what I find on old injectors........

A "quote" rebuilt injector has only been cleaned and the pressure set...............setting the pressure is extremly important.........equaly so is making sure they do not drip...............

regards,
crossbones


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PostPosted: Thu Jun 01, 2006 8:55 am 
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JoeIsuzu wrote:
Keep in mind that the "duration" is controlled only by the pressure that is supplied by the IP, at least on the old-technology diesels like ours.

crossbones wrote:
Hello everyone. The duration of the injection is controlled some by the injector pressures. The fuel quanity adjustment screw is a major factor with duration of injection.......

What I meant was, as long as the supplied pressure exceeds the pop-off pressure, the injector is "open". I was not addressing how to adjust that.

Jack

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PostPosted: Fri Jun 02, 2006 8:18 am 
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Hello.......you may find this thread interesting about what we have been talking about so far...............

http://www.4x4wire.com/forums/showflat. ... art=1&vc=1

regards,
crossbones


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PostPosted: Fri Jun 02, 2006 8:44 am 
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crossbones wrote:
Hello.......you may find this thread interesting about what we have been talking about so far...............

http://www.4x4wire.com/forums/showflat. ... art=1&vc=1

regards,
crossbones

This is fascinating, but now I'm caught in a "loop". That thread refers back to this one...this one refers to that one...I'm stuck! How do I get out? :wink:

Jack

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PostPosted: Fri Jun 02, 2006 8:54 am 
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I don't fully agree with some of what is posted here. So, here's my two-cents - take it or leave it, I guess.
I've worked as a diesel mechanic for almost 40 years now. My work experience has been mostly on heavy equipment and has involved engine rebuilding and repair along with bench work on diesel fuel injectors and pumps. I was an injection pump repair guy at two dealerships - most repairs involving Roosamaster/Stanadyne, CAV, Amercan Bosch, Detroit Diesel, and Simms pumps. I have had little experience with the little rotary Bosch, or Bosch-type VE (Diesel Kiki) pumps used on Isuzu and Volkswagen cars and small trucks. That is mostly because they are virtually trouble-free. In regard to Isuzu, we had many pieces of heavy equipment with small Isuzu diesels, but those used the more rugged in-line piston-type injection pumps, not the rotary VEs.
My experience does not automatically make me an expert on anything - but I do know a few things about mechanically injected diesels and Isuzus. I own three Isuzu powered vehicles with the small fours, and one full-size Chevy with the Isuzu V-8 diesel.

First - in regard to the fuel-injectors and pressure settings. For a smooth running engine, having the pressures generally equal with all four is more important than the pressure setting. Taking used injectors and trying to set their pressures to that of new injectors is asking for problems - and there is no noticeable gain from it. I've had many engines on dynometers and measured any possible gains in power - it will be small to non-existent. A plugged, or partially plugged injector, will of course rob a lot of power. But, it is natural for a fuel injector to "settle" over time and the operating pressure will get lower. Many spec tables will give pressure settings in two scales - one for new, and one for used. I have run engines on the dyno, before and after and injector change and seen, often no difference in power even though the new injectors were set much higher. Injector pressure will also, to some degree, affect fuel timing advance - I explain in a later paragraph. Keep in mind, that when an Isuzu, Bosch or Diesel Kiki tech. manual gives an injector opening pressure of 1500 PSI - it is also stating that worn parts - e.g. the needle and seat in the injector must NOT be worn. Well - that pretty much tells the full story. If you are working on a well used injector -the parts WILL be worn - so don't expect the injector to always respond well to a pressure setting meant for new parts. I have seen many used injectors that worked fine until the pressure was jacked up. Some will work okay, and some will not. From what I've seen, it's best to leave the settings alone if all are even. Many times, in the case of replacing one injector with a new one - against the others being used - we usually LOWER the pressure in the new injector to match the others - usually by half the difference since the new injector will also lower itself a bit over time.

Second - in regard to "rebuilt" injectors only being cleaned and set. That is not always true. If you are buying injectors, or having them worked on, ask what the descriptive words actually mean. "Rebuilt" means different things to different people. Yes, some such injectors are simply cleaned and set and will not have the service life of a new injector. But, there are some very expensive machines that reclaim and resurface the valve and seats in injectors and they CAN be almost as good as new. Also, some techs. install brand new tips and they ARE as good as new. YOU HAVE TO ASK. I just went though this myself. A shop is selling NEW injectors on Ebay, and cheap. I wanted some for my 94 Ford turbo-diesel, but I called first. NEW to this shop means little. They were simply cleaned and reset - in my mind they are lying about what they are selling.

Third - in regard to external pump adjustments. Many functions can be adjusted externally, including low-side transfer pump pressure, fuel delivery amount, timing advance, etc. All these functions, however work together in certain ways. So, unless you have a distinct problem you are trying to correct, fooling around with settings may not be a good thing.

Some examples:

Turning up the fuel delivery will create excess smoke under load and extra heat. The engine is only designed to successfully utilize a certain amount of fuel - and once that is exceeded, it is mostly wasted. Now, there are a few engines out there that come from the factory "detuned." This is popular with some farm tractors and industrial machines. It enables a company to use the same engine in various horsepower settings. The more you pay, the more power you get - but all actually use the same engine. Often, the higher power units have larger cooling systems. This is one case where some engines respond very well to turning up the fuel. But . . . this does NOT apply to the little naturally-aspirated four-cylinder 1.8 or 2.2 Isuzu engines. Now, if you want to turbocharge, or supercharge, and intercool, and inject propane - then you could use extra fuel and make more power - but you'd then have to figure out how to hold the little engine together.

Timing - In many ways, the distributor injection pump on the Isuzu works like a distributor on a gas engine. It's mounting can be loosened, and it can be physically turned to advance or retard timing. But - this is only meant for the initial or "static" timing. Keep in mind, that the pump also has an adjustable timing advance - and with the Isuzu - the pump is capable of advancing up to 12 degrees (pump degrees) which equals 24 engine degrees. This timing advance is operated by fuel pressure that can range from 40 PSI up to 175 PSI. The more pressure - the more advance. This action is adjusted by spring pressure that is accessed from the outside of the pump. But, if the fuel-pump vanes themselves get worn, the advance gets sluggish. Also - if the pressure at the fuel injectors is raised - then "injection lag" is increased, and timing will also be affected. This "lag" results in the amount of time it takes for injection pressure created at the pump to actually reach the fuel injector. The higher the pressure, the more lag. If you suspect the timing is not advancing as far as it should, you won't hurt anything by simply rotating the pump a bit. This is a "back-door" approach and more of a band-aid than a true repair. But . . . sometimes simple is good. If, perhaps the pump is a bit worn and falling short by maybe four engine degrees of advance - and it sometimes skips a bit at higher RPMs - and you simply loosen the pump and rotate to accomodate. Well - the end result will be - you will now have more advance timing at the higher RPM - but the down side will be too much advance when you first start the engine and at lower RPMs. If the engine still starts fine - then don't worry about it. In fact - many British diesels advise doing so if a little more power is wanted - but they also advise that is will result in more diesel "knock" noise.


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PostPosted: Fri Jun 02, 2006 1:26 pm 
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It's obvious ther is a wealth of knowledge available from you guys on the subject of injector pumps and injectors. Hopefully someone could share with us the location of all the external adjustment on the pump, how to adjust them and what they do (pros and cons) as well as the ejectors. I think this would help to clear up many of the questions most of us have and provide us a greater knowledge of how our fuel system operates.

Just like Jack, I'm caught up in this thread and enjoy learning!

Thanks Guys!

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 Post subject: RE: Devil Pup
PostPosted: Fri Jun 02, 2006 3:06 pm 
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You can buy a pretty well written book from Bosch there will explain, in detail every system and subsytem in the VE pump. It will NOT give you enough detail for rebuilds or repairs, but it's good reading just the same and has good drawings and/or photos. They have an online book catalog at: http://www.boschtechinfo.com/ The book that relates to the Isuzu VE type pumps is - Distributor Type Diesel Fuel Injection Pumps - Bosch No. 1 987 722 144, ISBN No. 3-934584-65-9, Costs $17 plus all the shipping and handling garbage. Bosch used to have a better manual specific to the VE pump, but it's out of print.

My explanations here are a bit simplistic - so don't get p*ssed off if I've left some details out.

As far as me describing all the adjustments to you - it's much easier to understand with photos and diagrams. But, as I said previously, many of the subsystems affect each other. So, making adjustments without a lot of experience is, more-or-less a crap shoot. On this pump as used in the Isuzu, there is not a lot of provision for seeing the results of your adjustments with common, generic, measuring devices. On many other distributor pumps, especially U.S. built Stanadynes/Roosamaster, you can affix a temporary plastic timing window on the pump, and adjust the timing advance with the engine running with an external trimmer screw. But, no such thing on the Bosch/Diesel Kiki pump. So, on the vehicle, it boils down to trial-and-error. If it starts better cold, or runs better hot or cold - then you did good. If it runs worse, smokes too much, starts hard, etc. - then you screwed up. If it runs good, but fuel mileage drops from 30 MPG down to 18 MPG - well, you screwed up again, etc. etc.
Here is a brief description of some of the systems within the pump. Keep in mind, that this is a rotary distributor pump. That means there is only one little pump that has to feed fuel to ALL the cylinders - in this case four. So, there is a distributor section on the pump - and it distributes the fuel from the one pump to whatever cylinder needs it - in the direction or order of the firing order. Now, with a lot of industrial stuff, and some cars - e.g. Mercedes, and in-line pump is used. And in-line pump has a separate pump for every cylinder, so by nature, is more durable. With a four-cylinder engine, an in-line pump does only 1/4 the work of a rotary. So, the rotary as used in the P'UPs has a planned trouble-free life span of approx. 250,000 miles, whereas an in-line pump is rated for at least 1,000,000 miles. There are. of course, many exception either way.
Back to the VE rotary as used in the P'UP or Chevette. Here are a few sub-systems that all work together. inside the VE injection pump. It is designed for a maximum power rating of 25 KW per cylinder.

Transfer pump - it uses vanes and draws fuel from the fuel tank with suction. This setup can be a problem at times simply because, if a fuel line starts leaking, it will suck IN air, instead of leaking OUT fuel. So, you cannot see the leak. Many times, the injection pump gets blamed when there is nothing wrong with it. One remedy is to add a small electric fuel pump. This transfer pump sends fuel on to the little high-pressure piston pump than can generate pressures over 5000 PSI for indirect injection engines and 18,000 PSI for direct injection setups. The transfer pressure gets higher as engine and pump RPM increases. As this pressure increases, in a range from 40 - 175 PSI, the fuel timing advances by means of a hydraulic piston held back with spring pressure. So, timing advance can be altered via fuel pressure or spring pressure.

Distributor head and rotor - this is the section of the pump that has ports that line up and distribute fuel to the proper cylinder in the proper sequence - with the Isuzu 2.2 it is 1-3-4-2. No adjustments, and no repair - it relies on close fitting parts - and if it gets worn - it must be replace. It is the most expensive part of the pump. It is also very dependent of good lubrication and will not tolerate any water, or temperature "shocks" - like getting hit with cold water when hot.

Axial piston pump - this is the single pump that is fed by the transfer pump, and creates the high pressures needed to open the fuel injectors. It is, more-or-less non repairable, it can only ge replaced. The amount of fuel it delivers can be changed by altering the length of its travel - i.e its stroke.

Mechanical Governor - it uses flyweights and springs and keeps the engine at the desired RPM up to the preset limit. The VE pump is designed to govern to a speed of a maximum of 4800 engine RPM. The pump runs at half engine speed. The Isuzu P'UP 2.2 engine is designed to run at a max. of 5100 RPM which is 2550 RPM at the injection pump.

Fuel timing Advance - works by transfer pump against a hydraulic piston. The pressure varies with RPM, 40 to 175 PSI. At 1000 pump RPM (2000 engine RPM), timing movement in the pump is 1.6 to 2.8 mm. At 1500 RPM it is 4.1 to 4.7 mms, and at 2175 RPM it is 7 to 7.9 mm. Transfer pump pressures at the given RPMs are - 1000 RPMs = 3.8 - 4.4, 1500 RPM = 5.2 - 5.6. and at 2175 RPM = 6.6 - 7.2 (these pressure figures are kilograms per centimeters squared).

Aneroid Compensator - monitors air density due to altitude and changes fuel delivery to compensate. Turbochargers use to do sort of the same thing and - in the old days - were usually called "altitude compensators." A turbo makes up for less air by forcing more volume into the combustion chamber instead of changing fuel delivery. Also, many gas engines used to be available with "high altitude pistons" for use in areas of high elevations. The problem with them - was and is - what happens if the machine gets moved to a lower area - and then has too high a compression ratio.

Cold Start Device - allows for extra fuel delivery for easier cold-starting. Many older diesels - especially with farm and industrial equipment, had a separate cold-start device which was sometimes, just a hand-pump that squirted raw fuel into the engine air-intake for cold starting. Some other systems have a hand-primer and a heater element - so fuel actually lights when the hand-pump is used, and a sort of "flame thrower" results. My John Deere 2010 and my Allis Chalmers HD6 both still have hand primers for cold stating. Most US built gas engines, before 1986, with carburetors, did the same thing via an accelerator pump. Every time you stomped down on the gas pedal - a charge or squirt of raw fuel was shot into the engine's intake.

Electric Shut-off Solenoid - shuts off the fuel to the engine turns off - and does so with an electric solenoid. Some other vehicles use a manual pull-lever to shut off fuel - or in some cases - the lever activates an air-choke (like in some older Mercedes). Many Detroit Diesel engines have both. The primary shut-off turns the fuel off, and then there is an additional "emergency" shut-off that closes off the air intake.

Fuel Injection Nozzle - it is set to open, when new, at around 1500 PSI in the Isuzu 2.2 or 1.8. Some diesels run at well over 3000 PSI. The pressure is determined by a spring with either shims or a screw-adjuster. The main idea is - that no fuel can run through the injector until the pressure setting is met - and it then releases almost instantly - with all the fuel charge running though tiny little holes - or the pintle opening - thus creating a fine atomized mist of fuel. Naturally, the higher the pressure - and the more "instant" it occurs, the more atomized the charge - which leads to better combustion.
With a used injection with wear, the pressure settles to a lower level. Also, since the parts are worn, the firing is not quite so "instant" anymore - so atomization is not as good as a new injector. Sometimes, when attempts are made to raise the pressure on a used injector to new specs - it works worse instead of better. That is because of the wear - and with increased pressure - it dribbles or leaks more before during a slower injection process - instead of doing so instantly. I have run engines on dynos with close-to-worn-out injectors - often running pressures 300 PSI low. I then ran the same engines with brand new injectors. Usually there was NO measurable difference in power as long as the older injectors were not plugged. I suspect there was some drop in fuel efficiency, but not much. Cold starting was also barely affected. From what I've seen - when you know injectors are getting very worn - they are probably due to fail somewhere down the road - usually by sticking wide open - or by getting plugged. So, as preventitive maintenance, it's a good idea to check them every 100K - 150K miles. Sometimes it's hard to figure what to do. I just pulled all the injectors out of my 94 Ford F250 with a turbo 7.3 litre diesel. It has 220,000 miles on it and was starting and running fine. Well - the injectors were running 200 - 300 PSI low, but other than that were working fine. I installed new ones - but hated to do it. I bought eight new injectors at $36 each - and now - the truck runs and starts absolutley the same and fuel mileage is unchanged. But . . . I plan on taking a couple of long cross-country trips and I don't want to be fixing things out on the road. In regard to the Isuzus and some other small diesels. I pulled the injectors out of my wife's 91 diesel Volkswagne Jetta with 190K miles on it. They checked perfect - and being cheap - I just put them back in. I also pulled the injectors out of my 81 Chevette with the Isuzu 1.8 and 260K miles and they also checked out fine - and - I put them back in. My 87 Suburban with a 6.2 diesel and Bosch injectors, to the converse, developed a very bad engine knock at 80,000 miles. Ends up it was one bad injector - but the other seven checked perfect. I replaced them anyway - I had gotten a pretty good buy on new injectors at $18 each.


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PostPosted: Fri Jun 02, 2006 5:34 pm 
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:? I'm scared to even open the hood of my truck anymore afraid I'll upset this delicately engineered balance. Seriousely, I've enjoyed the read about my injection system. I have a couple of injectors on my 84 that seem to be leaking fuel, but haven't pinpointed the source yet. Looks like it's from around the base where it screws into he head. This particular truck blows some white smoke out when it first cranks, and sputters, but eventually clears up. My stress level is about "redlined" right now w/ my new position at work, so a seemingly minor problem w/ my truck remains minor. If I had more liesure time, I'd tinker with it a little more. Thanks for the terrific information.
Andy

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PostPosted: Fri Jun 02, 2006 9:02 pm 
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one word... WOW

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PostPosted: Sat Jun 03, 2006 8:45 am 
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Hello jdemaris. Just a few things......I agree with most of the things you posted in general.........I have a diesel timing light that I can tell both pump timing or injector timing at any rpm and under any conditions such as real time driving..............on any diesel engine with a injector line to one tenth of one degree.............my books on the VE pump has different speck information of the pump timing than yours.......says it is capable of 8° advance and on the 15 or so of these 2.2 engines (I own 9) about the average advance of the CSD is about 5-6°.................If memory serves me it also allow a injection quanity of 63 cc's/1000 which is about double the quanity needed for 2500 engine rpms and its main purpose is the "help seal the cylinder" to give added cranking compression..............used often with IDI's.......the CSD is usually canceled before 700 pump rpm and returns to a fuel quanity of about 25 cc's/1000 at 600 pump rpm and the injector timing is then retarded the average 5-6° from cold start...............

Now as far as the Injector pump advancing the timing............this is a much missed conceived idea.........what the Injector pump is doing is tring to maintain injector timing at a fixed point..........at 800 engine rpm the mechanical delay time from the pump to the injector is .960° and at say 2500 rpms is 3°.......and this does not include all of the other factors at effect this delay time to the injector.................

I believe you mention advancing the timing about 4° helps.........agreed to a point as the EPA's attempt at controlling emissions of the time of the engines was to mandate they be retarded 4° (injector timing) from the factory.........increasing the injector pressure over OEM speck does have a retarding effect on injector timing and having a weak injection pressure does not get the fuel core charge as deep in the chamber to expose it to the hotter temperatures and mixing currents of compression causing a incomplete combustion.............advancing the timing with weak injectors does little if any good.............

the injectors that I have tested behind the professional pump and injector "rebuilders" do sometimes show this typical 200-250 PSI lower pop off pressure and leak like hell over the "factory recommend 350-500 PSI drip test"...............this is considered a "good injector" as I am told.....................maybe for you...........

my personal specks for the N/A injector is all injectors MUST pop off at exactly 1500 (factory is 1493) PSI and they MUST be able to hold that pressure without ANY LEAK DOWN for two minutes....................and this is AFTER the cap has been torque...........just torque the cap down can change the pop off 30-50 PSI.....................just how many professional shops are going to spend 30 minutes per injector just to torque the cap and keep the pressure balanced between all injectors to that speck.....................


My post started off with a question from Joe about how to set the timing and then on to how to set the injector pressure................... and on the 4X4 wire was asked about the same thing,,,,,,,,so I thought reading both threads would help answer some question.........sorry.............Even with a perfectly setup IP on a Bosch Injector Pump tester and the static timing set perfectly on the engine or even having a timing light...........the timing is still not optimized for the fuel being used.........the cetane value of the different fuels people may be using varies from about 35 to 65 of which none of the factory way of setting the timing addresses............................which the Dept of Energy states that a cetane change of 10 points is equal to 1° timing change and that varies with engine rpm......................it does not address the issue of lower compression, valve train wear or timing belt stretch ..................

The bottom line is this: all of this talk and facts about the excepted (factory) way of setting the timing Does Not Completely Address All of the Issues That Effect the Auto Ignition Timing of the given fuel of which is ........The Finial Timing of a Diesel Engine...............

My method of setting the timing does...........as I am using a relationship of temperature/cylinder pressure of which is the Direct Result of the Auto Ignition Timing..............................

Can you set your timing for any cetane value fuel you want to use with predictable results?????

What is the cetane value of your fuel??

What cetane value was the original factory timing set for???

Do you have a "meter as such" to see the difference when changing the fuel quanity screw with the engine running in real time???

Do you have a reasonable way to get a relationship of inside cylinder temperatures??

Maybe you blend your own fuel, how do you know if its a good blend??

Can you set your timing for the best results for the speed and loads that you use the most???

The list goes own...........

Simple enough to try and see for yourself.................I am either right or wrong.......report your findings.......

regards,
crossbones


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