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Better injectors than stock Bosch units?

Not wanting to change to EFI, are there any injectors available to supersede the stock Bosch injectors from 78-89 930 3.3L?
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Old 02-18-2014, 11:00 AM
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Define "better".
Better atomization? Greater volume of fuel delivered?
Rumor is that Turbo 3.6 injectors deliver a little more fuel. Otherwise you don't have much to gain except swapping your injectors out for a set of new clean ones.
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Old 02-18-2014, 12:04 PM
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Unlike an electronic fuel injector, the CIS injectors do not use an electronic signal to open... they use pressure. Once line pressure hits a certain value, the injector opens. Based on this fact, even if you could get a bigger injector, the results would not be really any different.
Electronic injectors use timing (in Ms) to adjust the amount of fuel injected, as well as size (measured in cc's, or Lbs) and fuel pressure.

On a CIS car, the only measurement you can play with is fuel pressure... which is why the B/L warm up regulator is sought after, because you can adjust control and working pressures..

For CIS, the best you can do is get yourself a set of matched injectors, that are very close to each other, and clean ones that have a perfect spray pattern....
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Old 02-18-2014, 01:11 PM
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This board is pretty remarkable. Great post. Terrific responses.

Thanks!
Old 02-18-2014, 01:16 PM
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Quote:
Originally Posted by 911nut View Post
Define "better".
Better atomization? Greater volume of fuel delivered?
Rumor is that Turbo 3.6 injectors deliver a little more fuel. Otherwise you don't have much to gain except swapping your injectors out for a set of new clean ones.
Yes, atomization. For instance, one of the few upgrades from a VW GTi from model year 83 to 84 was improved injectors quoting better atomization.

I would think any old-school injector eventually(besides the tip) has to get filled with crude since the fuel filter is only so good, and thus compromise the spray pattern. Pic is cross section of CIS injector.


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Old 02-18-2014, 01:30 PM
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Injectors are ware items. You will be amazed how nice new ones will perform. The -009 Euros have greater flow than the standard -017 USA.
Old 02-18-2014, 01:38 PM
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Quote:
Originally Posted by Tilikum Turbo View Post
Well, what is pictured there is why it's BS, IMO, when vendors claim they can clean CIS injectors. It would be next to impossible to get the crap out of that narrow space between the cone filter and the bore.
Unfortunately, it seems like the factory didn't push Bosch to improve much on CIS; doing only what they had to for emissions. Bosch wasn't going to invest anything on it's own since Porsche was the only customer for the archaic system (I'm talking about the Turbo 3.6 time frame) and K-Jet production volumes were miniscule at that point.
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Old 02-18-2014, 03:43 PM
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Too bad a person can't get those injectors apart and take out the cone filter, which certainly may plug over time. One would think that our in-line fuel filters are much better up to the task of removing particulates to where the fine mesh screen within the injector is an unnecessary add-on. Plus, I wouldn't be surprised that the screens are steel and thus prone to corrosion from the E10 fuel (and it's propensity to attract H2O) that we're all forced to use. Corrosion=plugage=poor fuel delivery=lean=holes in pistons (well....)
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Old 02-18-2014, 06:27 PM
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Quote:
Originally Posted by 911nut View Post
Well, what is pictured there is why it's BS, IMO, when vendors claim they can clean CIS injectors. It would be next to impossible to get the crap out of that narrow space between the cone filter and the bore.
I believe that is why the well know injector guy/shop, Witchhunter Performance, quit offering to clean CIS injectors a couple-a-three years ago - found it couldn't be properly done.
Old 02-18-2014, 06:40 PM
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I used to offer injector cleaning but always discouraged it as a short-term fix at best. Problem is that new ones cost >$700/set so I can understand why folks want to try cleaning them.
You can take them apart and if you do will see why they are not worth refurbishing. The spring is rusty and worn out, there is all kinds of crap in the screens, which are also rusty, and buildup on the pintle. I sonicated the ones I cleaned for folks with the pintle held open. They did work better but nothing comes close to new.
Now I just verify cracking pressure and spray pattern. If they fail they hit the trash can.


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Old 02-18-2014, 06:57 PM
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Quote:
Originally Posted by RarlyL8 View Post
The spring is rusty and worn out...
+1
With a warm can of carb cleaner, I was able to make an old injector (70k miles) spray to check the pattern but the carb cleaner can couldn't generate enough pressure to open a new injector.
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Old 02-19-2014, 05:52 AM
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neat testing rig Brian!
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Cool home-made pop tester, Brian. Do you use that for diesel injectors as well? If the piping is up to it, seems it would be easy to swap a 2500 psi gauge on it.
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Old 02-19-2014, 11:48 AM
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Quote:
Originally Posted by RarlyL8 View Post
Injectors are ware items. You will be amazed how nice new ones will perform. The -009 Euros have greater flow than the standard -017 USA.
The 0439505009 have more flow capability, but swapping them in place of 0439505017 will not allow for more flow on a US (aluminum) fuel distributor. The injectors have no metering function. The fuel quantity is controlled only by the barrel slits in the fuel distributor, and the differential pressure across them.

There is an air shrouded K-Jetronic injector that has better atomization. VW and Audi used them. Not easy to adapt to a Porsche though.
Old 02-19-2014, 12:38 PM
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well i just wrote a long post on how to backflush these stoopid obsolete injectors with an air compressor and carb cleaner and some copper wire to hold the pintle open and hit the wrong button and deleted it....
Old 02-19-2014, 01:32 PM
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Quote:
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well i just wrote a long post on how to backflush these stoopid obsolete injectors with an air compressor and carb cleaner and some copper wire to hold the pintle open and hit the wrong button and deleted it....
^ I hate it when that happens.

I replaced my injectors a couple years ago (yep, they're expensive). I have a good functioning CIS, but the next time any expensive components go tits up, I'll probably use that as an excuse to covert to EFI. At a certain point it doesn't make sense to throw good money at obsolete tech. For a driver of course - if you're a collector/concours originality guy, its a different game.
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Old 02-19-2014, 01:58 PM
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Ditto that Jim, I've done that a number of times when using my laptop keyboard and not my wireless keyboard @ my desk - stoopid f'n trackpad gets nicked by my palm and - POOF - argh!

I'd be very grateful if you wouldn't mind taking a moment to regurgitate said thoughts 8-). New ones def not in my budget, but would really love to give your method the 'ole college try!
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Old 02-19-2014, 02:03 PM
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Paulito, the following thread, along with several linked threads within it, detail how some people have attempted to clean the injectors (I added this to my "saved threads" several years ago) - And an even bigger FU, of course!

Blocked Injectors - how to clean?

Last edited by Ronnie's.930; 02-19-2014 at 02:15 PM..
Old 02-19-2014, 02:12 PM
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Sorry if I transpose letters every now and then, most folks are not so sensitive about that.
Yes capacity is something that will not be used when the restriction comes from elsewhere in the system.
EFI can be a very expensive proposition. I wouldn't be so quick to can the CIS.
Old 02-19-2014, 02:12 PM
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Quote:
Originally Posted by krasuskyp View Post
Ditto that Jim, I've done that a number of times when using my laptop keyboard and not my wireless keyboard @ my desk - stoopid f'n trackpad gets nicked by my palm and - POOF - argh!

I'd be very grateful if you wouldn't mind taking a moment to regurgitate said thoughts 8-). New ones def not in my budget, but would really love to give your method the 'ole college try!
Actually that method works fairly well, backflushing as it were. Just be carefull not to reef too hard on the pintle when you're wrapping that fine copper wire around it to hold it open...for fear of bending it I guess.

Now about this:

"I have a good functioning CIS, but the next time any expensive components go tits up..."

I thought we were going to stop profaning each other? Well, I guess there's really nothing profane about them thar things....
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