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First pic is a close-up of the reference bore from which all other bores were CC'd to identical liquid volume, ie; +/- 1 drop or 1/20 of a millilitre equal volume in all 6 cylinder head intake runners.

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RCE injector on left/Bosch on right.

This is particularly important due to next picture in this thread.

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TONS more fuel to make as little power as possible.

The red circles show the extreme restriction about 1" below the injector spray orifice. That tight "V-shaped" restriction is .375" at its widest point. Your OEM injector spray pattern is .616" wide at that point. Could explain why that spot is always clean and spotless every time you peer in that injector bung. Wide dispersion conical spray pattern of fuel hits that obstruction and due to it's angle deflects and splashes of that obstruction, ricochets to the runner wall 180* opposite (downward in pic) and becomes big sloppy drops of fuel that then are pulled into the combustion chambers in much the same size and pattern as rain falling down your windsheild.

This guarantees we use tons of fuel, have dispicable A/F mixtures in the combustion chambers at all times and struggle with making good power.

The RCE injectors are FAR superior to the OEM injector when it comes to threading this needle but best performance comes about with the old adage that "an ounce of prevention is worth a pound of cure"... that is to say GET RID OF THE PROBLEM!!

Getting rid of that problem is exactly where we're going next.

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In that past I've simply used my grinding tools to go at this kinda thing. But while doing it this time it dawned on me that by using the runner assembly I cut off a 12V IM I had the workings to make a very nice jig fixture that would allow me to get perfect alignment of the injector spray pattern to go where it was meant to go originally... directly at the back-side of the valve head.

By bolting this fixture to the cylinder head IM flanges using stock OEM bolts I could then turn a bushing up in the lathe that is a snug interference-fit into the injector bungs. Then by drilling an under-size bore thru the bushing then reaming it to .0005" over the diameter of the grinding tool shanks I would have a guide that when tapped into the injector bung would give me perfect alignment to the intake valve. The by using engine oil in that bushing I could then turn the grinding tools as fast as I wanted as like our cams they allow the precision ground bur shanks to ride on a film of oil within the bushing bore. This give me perfect alignment and all I have to do is move the grinder hand-piece up and down for a perfect spray pattern bore that as-planned does indeed aim the injector spray pattern DIRECTLY at the intake valve. By running the smaller diameter "flame tip" bur thru first opens the V-groove up and then a .500" diameter ball-nose bur can be used to open the bore up further. Then sanding drums and/or other polishing media can be used to smooth out any roughness left by the coarse aluminum-cutting carbide burs.

Of course I did all this before but by hand. Had I had this tool available I could've made a FAR faster, more acurate task. And when finished the bur and guide are tapped out of one injector bung and moved to the next as an assembled unit where the process is repeated. And this can be used with laps, hones, buffs, flapper wheels etc etc. When one cylinder bank is done just move the fixture assembly to the next cylinder bank and repeat the process.

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This shows precisely where the injector spray pattern is aimed. Injector spray alignment just CANNOT get any better than this!!!

Important to note that this valve and all others had about 1/8" thick hard, granular, crystalline carbon build-up on the surface shown in this pic when IM was replaced. The addition of narrow cone RCE injector flow patterns and unshrouding the injector obstruction in the head intake runner and 5k miles of driving shows this intake valve today. There was no clean-up done on this valve for this pic. This is what all 6 of my intake valves look like today when I remove the IM.

Something is working very, Very, VERY right!!

if i understand this correctly?

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This is the cylinder head intake runner from one of my spare heads. As you can see by the red dot on the area I've removed from my heads that area is constantly cleaned by injector fuel spray bouncing off of the area inside the marks left by the old intake manifold gasket. That fuel spray is then deflected to the runner wall 180* opposite and indicated by the curved red line on bottom of intake port. Below the red line is dirty indicating it sees no fuel spray. Above the red line is clean indicating the spray pattern starts there and then is pulled into the combustion chamber via vacuum. The intake valve head back-side is covered with 1/8" thick carbon build-up indicating there's no fuel being sprayed directly on it that would otherwise keep it clean of carbon build-up.

When comparing this to my pic below of my cylinder head intake runner and it's intake valve you can see the benefit of both removing the restriction found in the cylinder head that are ground away on mine as well as the smaller, more focused spray pattern if the RCE injectors that via constant focused fuel being delivered to the back-side of the intake valve how much cleaner everything is in that area. Doesn't break my heart that you can feel it in the seat of your britches either!

The efficiency of a more focused and totally unrestricted injector fuel pattern allows fuel to go directly to the combustion chamber without having to be pulled down the runner walls. The velocity around the valve head can be close to 200 miles per hour insuring a focused stream of fuel aimed directly at the valve head can be pulled into the combustion chamber immediately and at INCREDIBLY high velocity insuring it's even more finely atomized after the valve closes and combustion occurs. This all plays into how I'm able to run a lower flow-rated injector with increased power and efficiency.

There's LOTS more to injectors than just their flow rate. If their pattern is all wrong for the application or if they aren't aimed correctly or if their fuel flow path is mostly obstructed it doesn't matter what injector you use... it'll always be horribly inefficient and totally WRONG! You've GOT to get the fuel to where the combustion is via the most well-aimed, finely atomized and unobstructed flow-path possible. And when done right intake valves stay shiney-spotless and you make MORE power with LESS fuel.

When running fuel efficiencies such as these you eliminate a LOT of things that Audi engines are known to require. A perfect example of this is the complete lack of fuel additives and treatments used to keep things clean in the upper combustion area. Why would I use those when my valves look like they do in the pic in the post below!?! When everything is done right there's no need for all that crap. The engine is internally self-cleaning! I mean everyone has seen my exhaust tips. Everyone has seen my intake valves. It's a safe bet to assume EVERYTHING between my intake valves and exhaust tips is virtually as clean without adding a myriad of caustic, volatile and expensive internal engine-cleaning products! Again... "an ounce of prevention is worth a pound of cure."

that 'v-shaped' part is there in the first place. Did Audi put it there as a power restrictor?

this 4-5 years ago. I do not believe it's an intentional power-reducer but more likely just an INCREDIBLY stupid error/mistake. You have to remember something like this DEFINATELY has a significant negative influence on Audi's published city/highway EPA/MPG window sticker fuel figures. It's at least possible "maybe" Audi planned on narrow cone pattern injectors that were going to "thread the needle" past thru that obstruction then went back to ordinary wide-dispersal injectors when the bean-counters got a look at what narrow pattern injectors would cost.

Best I can offer is that trying to understand why someone does something/anything is a lot like a dog chasing a car, ie; once we catch it whatta we do with it!?!

if theres issues like this with the 7A head ??

where the injector is aimed and if there are any obstructions between the injector tip and the intake valve.

I "think" my 20V engines were clear of obstructions but I've always used RCE injectors because of their smaller/narrower, more fucused pattern that hits the valves rather than the runner walls 3"-4" upstream of the valves.

Using RCE's on my AAN/UrS4 was an incredibly good modification that cured a lot of related ails. Same on my TT. I just don't like Bosch injectors when used in cylinder heads with longer than 1.5" to 2" intake runners due to the fuel dispersal pattern always impacting the intake runners dramatically upstream of the intake valves. I will always prefer valve head fuel impact/dispersal to ANY/ALL other fuel-stream impact locations.

What sort of results would you get with the stock injectors with this mod?

then later when injectors are more in reach you don't have to R&amp;R the intake manifold to do this. Swapping injectors on these engines is a 20 minute task.

for myself this all makes even more sense to see you do this. some of the pluses of FSI is the high pressure injectors that atomize the fuel before it hits the chamber where ours has to heat up off the back of the valves to "atomize" which i see now a good part of it doesnt ever even get to the valves until bouncing around ..Very cool!!

and doing these extra modifications

from the intake runner? How much material was this that hadn't already been removed from gasket matching?

If you are willing to to a group buy, I will take one for sure...

Also, I assume you're running an adjustable FPR? Would you reccommend the same injector (SL4-155) for the rest of us? Is there anything preventing us from running the higher pressure?

Thanks Mance, I will add all of this to the head workshop pages.

what year is yours?

I only made that piece as an experiment and to keep for when I start into my builder motor's heads. As my posts indicate I had already done all of this head porting/polishing years ago and by hand and without the jig/fixture. Only thing I did this time was CC the cylinder head runners. I didn't use the jig for anything this time out. I just conceived it while working on my heads and made it just for distraction... to get away from stooping over the engine bay for an hour. It's a "nicety" but totally unnecessary for doing a single set of heads. If you were in the business of porting/polishing 12V heads for a living it would be indispensible but not for "one" pair!

I'm not recommending/encouraging anyone do what I've done injector-wise. My car is hugely different than any other car here today and my results would not necessarily work out for others. I have all kinds of fuel adjustments available via stand-alone and adjustable FPR that others here would have no way to adjust. I'm only pointing out what I've done and the results of that work.

Everyone is free to experiment with any part of what I've done but I don't wanna be the guy everyone runs to complaining "I did just as you have on your car and now my car runs like crap." I simply have a TON more control over fuel delivery than most anyone here which allows me a LOT of flexibilty. My car has "dynamic" fuel control while all others here have "static" control, ie; no adjustability without stand-alone beyond adding an adjustable fuel pressure regulator. But nothing as it relates to adjustable injector pulse-widths, durations, duty cycles, fuel maps etc etc.

People should be very careful when going this direction. Read everything they can get their hands on. Do the math on injectors. Learn about "cc's per minute" and "brake specific fuel consumption" before pulling the trigger on ANYTHING!! Best advice I can give on injector swapping is if you cant afford to make a mistake you'd do well to not start down this road cuz it's not a matter of "if" you're gonna screw up but simply "when." If I had a nickel for every bad/wrong injector choice I've made over the years I'd have a roll of nickels.

150cc/min, correct? One forum member has been running 143cc/min Bosch injectors (0 280 150 715 model) with good results so far and with better mileage. Your thoughts?

but because we run 4 bar (58psi) fuel pressure we're probably closer to 190cc/min actual flow rates. I would guess with adjustable fuel pressure regulator with a 3-5 bar range of adjustment one could go within 10-15% above or below OEM flow rates with the ability to make the car run/idle fine. But without the addition of additional air into the engine there's no inherent benefit to "just" throwing more fuel at the combustion chambers. All injector flow rates are tested at 43.5psi (3 bar) therefore when you're shopping injectors the flow rates for that injector were tested at 43.5psi.

In my own situation and with all my induction mods I didn't have to throw more fuel into the engine until after the ported/polished IM and cylinder head work. And even then I was able to tweak the fuel pressure and stand-alone to compensate using a slightly under-sized injector but with a better "tighter" cone dispersal pattern. And no additional adjustment was needed from that point when I added the 272 cams beyond a slight bump in fuel pressure. But I've got a sneaking suspicion I'm at or very near my under-sized injectors 80% duty cycle and will likely hit the wall on further adjustments very soon if I'm not already there. An easy fix for me as I'll then just add the new set of 195cc/min injectors and back the fuel pressure and fuel maps down a bit and start over.

buying some RC injectors solely for the narrow spray pattern. Something close to OEM flow rates, just wasn't sure what to go with. I'd like to be able to buy one set and continue to use them throughout the rest of my modding, but maybe I'll just wait until I get stand-alone...

on an excel sheet dated 2/10/2003. My fuel pressure may not be very accurate as I don't quite trust my gauge, but it should be close to the ball park.