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  #1  
Old 02-18-2013, 12:26 PM
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Question Modifying injectors to larger flows

EDIT
Around post 1XX someone asked me to consolidate the post. The post turned from a what is done to make a larger injector to how you or I can make a modest sized injector at home or in conjunction with a local machine shop. So I made mine with the help of a local machinist since I do not have a lathe available to me. He was very hesitant to do what I asked, but after it was all said and done, it was an fairly easy process to do. Both the plunger and intensifier piston can be turned down on a lathe, but care must be taken to not damage the pieces in the chuck. For the DLC coated plunger, it was turned down using a diamond lapping wheel. Please read the rest of the post, especially where the photos and video are. Some will be included in the edited post.

First some basics:

The plunger bore is 6.34mm in diameter.
Below the spill port, the maximum volume is 0.178cc. At rest the plunger sits just above the spill port and at maximum extension it sits 0.025- 0.029" from the end of the barrel, giving about 0.135cc of injection.
The raw volume of a stock injector bore at rest is about 177ml! Losses to give about 135ml are the end gap (23ml) and the spill port (20ml).
You can increase the stroke to give a chamber volume of about 0.205cc before spill port losses affect the idle or performance characteristics. This will create a flow of just under 0.190cc.
If you want to go larger, do the math and be prepared to plug the spill-ports with 3.5mm brass rod or add shims to the top of the fuel plate. Read on!
Injectors are expensive. Work carefully because no one will sell you parts.
The barrels and plungers are matched - KEEP THE TOGETHER AS A SET - MARK WITH A SHARPIE. The tolerances are very tight. See Lilpooh"s measurements further down in the post #89.

Although all the plungers will be about 46.50mm, to ensure a good results, take off specific amounts, do not just make each part the same length. This plunger has 0.030" taken off the end. (I also took 0.020 off the clevis end - this was a mistake on my part and required me to make an adjustment to my intensifier piston and shim). For a 175cc injector modification the plunger needs to be shortened about 0.030" (0.633mm) to convert to a 175 volume. Compare the plunger below to the photo in post #7. The intensifier piston is about 21.43mm in length. To create the increased stroke, this needs to be shortened 0.050" 1.267mm to create a 175cc injector. See photos post #6. Ensure you have 0.002" (possibly more) clearance from the plunger to the end of the bore. If you go tighter, there is the possibility that the plunger will contact the fuel plate at max PW for your injector/nozzle selection. For a 175/75 injector, max fuelling will happen about 2.6ms PW.

<<< I deliberately went tight to the bottom of the bore (<0.001") with the plunger stroke. During a test run in the truck, at a high ICP and a PW of 2.6, my injectors are completely empty. How do I know? Well, I could hear an occasional slight ping. I thought this might happen, so to prevent damage, I will decrease the PW slightly on my extreme tune. Of course, I could go back and trim the plunger another 0.001". >>>

I measured another set of injectors. The intensifier bore depth was out slightly on some of them. I had similar results on the first set as well. Lilpooh shows 0.029" as the space available, but I had a few that were as tight as 0.025". It would be a good idea to measure the shims to see if they are different thicknesses as well to make up for the bore depth. Most of the ones I have seen are within 0.002 of each other.

After thinking about it a little longer, it is probably a good idea to leave a minimum of 0.005" as a buffer for the plunger to fuel plate clearance. So what ever you cut from the intensifier piston, cut 0.020" less off the plunger. I would cut 0.035" max of the hammer end of the plunger, and cut the remaining amount from the clevis end.

So for 190cc injectors, the chamber would need to be 6.63mm deep to keep the plunger safe from bottoming out. and the total stroke would be 6.5.mm. Again, keep in mind the plunger in a stock injector sits about 5.6mm from the fuel plate at rest (volume 177ml) but does not travel full length (loss of 22ml) and looses some out the spill port to give about a 135 injector. This is why a simple plug gives you a 155cc injector. This is also why you don't necessarily need to cut 0.087" (2.21mm) off the plunger to achieve the desired travel for a 190cc injector. You could, but it is not as efficient as moving the plunger down the bore by cutting more off the piston.

For a 190 injector cut about 0.065"off the intensifier piston and 0.045"off the plunger. Remember that the 0.035" you take off the bottom of the plunger does not affect the DLC wall or even the spill-port interaction. You could cut a bit more off (0.005"-0.010"), but the gain would be marginal at best and only at WOT.



In post #97 I wrote about the issues surrounding fuel flow for horsepower, torque, nozzles and PW (pulse width). It is a good read for determining what you need to reach a certain HP level and how PW and ICP is needed to deliver the fuel. I used 75% over nozzles that were extrude honed by Chatham Fuel Injector Services in Canada.

The torque values are:
Cross bolt = 0.5 Nm (very little torque) - this is probably why some break after a rebuild or inspection. I used a lot more torque to remove them!
Two hold down bolts = 3 Nm (a bit more torque)
Nozzle nut = 85 lb/ft** (about as much as you can pull with a normal wrench - it probably fine at 60 lb/ft). ** I came across an article recommending 55lb/ft. I used about 60lb/ft when I did mine. Perhaps the 85 was a transcribing error?

Here are 3 videos of the injector internals and how easy they should move. Included are shots of the spill ports for both fuel and oil. The outer casing is already take off and the nozzles are missing, since they are out for extrude honing to a larger size. All the moving parts should move this easily, without any play. I went very tight to the end, hopefully it won't cause any problems. Of course, if I don't exceed the PW for 100% flow, it should work. I mentioned the pressure for higher ICP, but the range is 3500-27000psi.







Here is them idling in the truck after installation.



I only had the SCT Performance tune on it for the installation, just to see how it behaved on start. If I go WOT, I get hazing, but the temps are quite good; all probably due to the 75% nozzles. Anything under 50% pedal is clean. I suspect with a hot tune (larger PW) and the stage 1 at WOT it will be dark, but how often are you going to do that in while driving. There is no doubt a bigger turbo is needed if you plan on playing hard - but that is another thread.

The fuel milage is crazy good! Up from 19mpg to 27+mpg on the same tune, possibly from the nozzles? I have to get a manual calculation done! I suspect the PCM calculates fuel consumption based on ICP and injector PW a model for a stock injector and nozzle.

There is a lot of good information in the remaining 161 (my in truck running report) or so posts; however, as with anything posted on the internet, you are responsible to ensure all measurements and movement are valid before you do this yourself. This was a relatively easy adventure. The only thing I would have changed is I would have used 50% over nozzles.


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Original Post
First off, this post is more for information, so if you don't know what is involved, don't guess. I will start off with a few assumptions, but they may be incomplete. At the end of the process, the myth about building larger injectors should be known to all. However, just because you know the process, doesn't mean you can pull it off yourself. I know of at least 10 re-builders/re-manufacturers, but only 4 modification shops. There are probably a number of other commercial, private or self builders, so with the right knowledge and skill set it might be possible for members here to DIY or with outside machine work. However, the tolerances are very tight, so if you try it yourself or have inferior work done at a "shop", then understand the result.

For regular injector modification, I believe the primary change is plunger length. If you were to machine off XX from the plunger end you increase the charge available for injection. At some point you may require other changes to ensure enough fuel makes it into the chamber in time for the next injection. I believe most modifiers now increase the diameter of the fuel intake for injectors larger than 190cc, but some may even do it for 190s. Knowing it take a very good lathe to have reliable tolerances of 0.0005", what is the amount of material removed from the plunger (or its new length) for 155cc, 175cc or 190cc injectors? There is a limit to how large you can go, before more modifications are required. What is that point, and what happens next? For instance, Hybrids, with larger barrels, plungers and intensifier pistons, are used over 300cc.

As well, what is being done to the spill ports lately?

I have written about nozzles in another post. There is no way these can be reliably made without very specialized equipment. EDM, honing and a combination of the 2 are the only way to make them reliably matched. However, they could be installed by a DIYer with the right tools and guidance.
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Last edited by twoicebergs; 04-18-2014 at 05:28 PM. Reason: Final solution!
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  #2  
Old 02-18-2013, 12:48 PM
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Modifying injectors to larger flows

Nice thread!! Time for me to get educated!!


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Old 02-18-2013, 01:21 PM
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It depends who is building the injectors, there are various ways to get to that "cc" rating.

You can machine the oil intensifier piston, shim the spool valve, machine the fuel plunger, shim the barrel at the fuel plates, bore the barrel/larger diameter plunger (hybrids) etc. The right way to do it? Couldn't tell you that, you have to find what works for you. There is a reason why some are cheaper than other because they use different methods, some are just easier and most cost effective to do. I wont even run an injector with plugged ports again, the rough choppy idle always bothered me, but to some it doesn't at all, all personal preference.

I will say this, whoever tells you that you HAVE to plug the spill ports to go over a certain volume capacity ie over 205s, is entirely wrong. I've also come across that there are two different shims used in some injectors out there. Whether this was a replacement from an aftermarket reman shop or Ford, but I have a few sets of cores here that have .020" shims and another that have .025" shims. So not all measurements are universal, there is some play room in that respect.
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Old 02-18-2013, 02:07 PM
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Very good information here. These are the type of threads that really get me excited. Greg is exactly right that there are several ways to machine the injectors for larger capacity. Depending on who builds the injectors and how large they are, any combination of the methods listed can be used to reach that displacement. As a general rule, the tighter the tolerances used in the machining and shimming, the better the injectors will run, i.e. smoother idle, more power, less smoke. For those who are buying injectors, just because an injector builder says the injectors will flow a certain amount of fuel, does not mean that they will actually flow that much, they need to be flow benched.

Quote:
Originally Posted by pizza pig View Post
I will say this, whoever tells you that you HAVE to plug the spill ports to go over a certain volume capacity ie over 205s, is entirely wrong.
This is true, to a point. At a certain size of injector, much larger than anything anyone will be running on the street, when the maximum amount of shimming, machining, and boring has been done. The only way to increase capacity further is to plug spill ports. This point may be somewhere over 500cc for all I know, but there is that theoretical point where the only way to increase volume any further is by plugging spill ports. It is safe to say that for all but one or two trucks on the planet, the injectors can be made in the desired size without plugged spill ports if one so chooses.
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Old 02-18-2013, 02:29 PM
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Quote:
Originally Posted by TooMuch03 View Post
Depending on who builds the injectors and how large they are, any combination of the methods listed can be used to reach that displacement. As a general rule, the tighter the tolerances used in the machining and shimming, the better the injectors will run, i.e. smoother idle, more power, less smoke. For those who are buying injectors, just because an injector builder says the injectors will flow a certain amount of fuel, does not mean that they will actually flow that much, they need to be flow benched.

Thats a common issue most people just build them to a capacity of 190cc of fuel lets say, and its left at that point.



This is true, to a point. At a certain size of injector, much larger than anything anyone will be running on the street, when the maximum amount of shimming, machining, and boring has been done. The only way to increase capacity further is to plug spill ports. This point may be somewhere over 500cc for all I know, but there is that theoretical point where the only way to increase volume any further is by plugging spill ports. It is safe to say that for all but one or two trucks on the planet, the injectors can be made in the desired size without plugged spill ports if one so chooses.
Thats hard to say, I have no clue, nor will I ever get to that level, because 98% of peoples goals can be done with far less fuel and it isn't necessary. I like to keep things reasonable and realistic, Im not after the happy land beyond the point of plugged spil ports. Im currently in the process of building two different individual injectors, that will be flow tested to compare the two. They will be large conventional, Over 250cc, open spill ports, using machined pieces and custom made shims. Im being patient though, quality work is worth the wait, especially around here. No I dont expect the truck to hold icp on a stock pump with all the fuel being used, big oil and tripples will be cleaning them up if all goes as planned, dont hold your breath for this one though
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Old 02-18-2013, 04:16 PM
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Short of pulling one apart, over the years I did grab some injector internal part photos. Here is a good shot of the intensifier(amplifier) piston, return spring and clevis, and the plunger.



This one gives the perspective of what fits where, but it's not labelled.



Greg, so from your experience, you are saying that laying in extra shims at the Spool valve housing is one method to increase the chamber size, or am I misreading your comment? I could see how machining the intensifier piston would require less precision (internal) to achieve the needed movement for volume.

Last edited by twoicebergs; 02-18-2013 at 04:20 PM.
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Old 02-18-2013, 04:27 PM
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Quote:
Originally Posted by twoicebergs View Post
Short of pulling one apart, over the years I did grab some injector internal part photos. Here is a good shot of the intensifier(amplifier) piston, return spring and clevis, and the plunger.



This one gives the perspective of what fits where, but it's not labelled.



Greg, so from your experience, you are saying that laying in extra shims at the Spool valve housing is one method to increase the chamber size, or am I misreading your comment? I could see how machining the intensifier piston would require less precision to achieve the needed movement for volume. Also, The same could be said for the top if the plunger.
Yes you read my comment correctly, you can see the shim in that photo there it has the 4 alignment holes in it. However I dont recommend you stack shims, i've seen it done, wouldn't ever trust it though, you dont even need to run the shim, in fact a lot of people machine them and pull the shims out, so that you can add a shim to make them larger or smaller. Its far easier to shim them at the spool than machining the plunger or intensifier piston. The Intensifier piston is machine fit the the bore of the injector body so you cannot at all score the finish on it to create it from operating properly. I like the idea of machining the plunger better, but again it has a hardened Diamond like coating that shouldn't really be messed with either. You can se on the bottom (left in the picture) of the fuel plunger where there is a line where the plunger becomes tapered? Thats the end you machine.

In that bottom image you see the two silver fuel plates? There is a ball bearing and check valve, next to the spring and fuel plunger? Thats where im talking about shimming the body. Shimming here, in addition to machining the plunger or intensifier piston, or shimming the spool allows you to increase volume without the need to plug the spill ports.
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Old 02-18-2013, 04:44 PM
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Thanks. It makes a lot more sense to do any shimming at the fuel metering plates, not the spool valve side.

Last edited by twoicebergs; 02-18-2013 at 06:50 PM. Reason: addition
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Old 02-18-2013, 04:46 PM
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I believe that the ever quoted 190cc max with open spill ports is if you don't do any shimming between the body and fuel plates.
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Old 02-18-2013, 05:35 PM
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careful with shimming at the spool valve. To thick of shim/shims will keep the o-ring from sealing.
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