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Injectors - choosing the right Design III (and some II info)

 
Old 03-16-2011, 06:59 AM
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Hilton
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Default Injectors - choosing the right Design III (and some II info)

edit2: Scroll down to Post #14 for a list of design III and II injectors which have the same grooves as a stock injector, to allow use of the fuel rail clips on an S4

Here's what I mean by II and II:
  • Design II look like the stock injectors with a plastic upper, and a metal lower, but instead of a pintle, they use a disc and have 4 holes for better atomization.
  • Design III have similar fitment, but an all-plastic body, which is narrower

Handily, both Design II and Design III injector body types have 4 holes, so I can ignore the old original Bosch design pintle-style injectors with their pencil stream of liquid fuel.

I'll be buying some 30lb injectors - for a very lightly modified 5.0L NA.. just modified S3 cams, X-pipe, and maybe GT-style port-matched intake manifold if I can be bothered (I have a sharktuner too).

Does anyone have any direct experience comparing the 4-hole design II to design III injectors running on a 928? Even if no experience of both types, I'd like opinions from all sides of the fence

This picture shows one of each type (III is on the right): (edit: scroll down to post 6 - there are multiple groove variations on design III's)




From what I can gather via armchair research, design III has a few advantages over II:
  • All plastic body reduces heat soak to the fuel
  • Nose is shorter (no plastic cap, just a plastic ring) so a few mm less protrusion into air stream
  • Slightly better spray pattern
  • Quieter ?? (anecdotal, and may just be a pintle vs. disc type feature)

But the design II is a simple plug and play, due to:
  • Same dimensions as a stock 32V injector
  • It already has the groove for the injector rail clip so no dremel needed (edit: NOTE - some design II do not have the grooves it turns out, e.g. 24lb ford)
  • Wider body that will prevent it falling too far into the intake if the clip fails/falls off
  • 4 hole version gives far superior spray pattern to stock pintle-style anyway

So, is it worth modifying a set of design III's to fit over just buying some design II's?

The "Quieter" point I've read actually interests me, as it bugs me that the 32V motor sounds like a sewing machine due to the injector noise

And here's a couple of videos of comparisons of various injector types (some types not relevant, but you can see the Bosch pintle, 4-hole and design III's):

Slow-mo


Fast-mo

Last edited by Hilton; 04-11-2011 at 03:16 AM.
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Old 03-16-2011, 02:08 PM
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Interesting videos. In the last one it appears the design III and the pink top design II have a pretty similiar spray pattern while the yellow top doesn't seem to atomize quite as well. I assume these are rebuilt and aren't new injectors so I wonder if the yellow top has more mileage than the pink top since they're both design II type and should have the same pattern. I don't think you're going to notice much difference in noise from the type II vs III since they're both disc type vs the pintle type which was noisy. A good site for comparing injector output and resistance based on bosch part # is http://www.polog40.co.uk/article_injector_table.php. It shows our stock 19# injectors, 0280150730, flow 201 CC/Min at 3 bar with 15.9 ohms resistance. Good site to use for ebay purchases.
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Old 03-16-2011, 02:58 PM
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one thing to consider if your putting the injector you have on the right then there wont be any way to hold it in position on the fuel rail,
a few others have used these and if things are just right the injector can come loose from the rail and fuel will spill and this will cause a fire, the injector will slide down into the manifold.
It is better to have the injector held in place with the clips
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Old 03-16-2011, 05:56 PM
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Agree stan - however a few rennlisters have used a dremel to cut grooves on the design III injector to allow it to use the stock clips to hold it in the fuel rail.

This post from Dave H. in another thread covers it:

Originally Posted by Dave H. View Post
i just put the injector (w/ o-ring on) in the fuel rail socket and then used the clip to make a mark on the injector body. i then cut the groove (both sides) where the mark was. repeated on the other 7...


Originally Posted by Mrmerlin View Post
one thing to consider if your putting the injector you have on the right then there wont be any way to hold it in position on the fuel rail,
a few others have used these and if things are just right the injector can come loose from the rail and fuel will spill and this will cause a fire, the injector will slide down into the manifold.
It is better to have the injector held in place with the clips
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Old 03-16-2011, 06:28 PM
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76FJ55
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I've installed type III in my 85. 24 lbs injectors. I used an old lathe to cut the clip slots in mine. Worked flawlessly. But if you look at the yellow III from the first post and compare it to the black III in post 4 you will notice a design difference in the top half of the bodies. The black design matches the ones I cut and installed, but the yellow ones don't appear to have the constant diameter upper which allows the addition I'd the clip groove.
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Old 03-16-2011, 07:24 PM
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Originally Posted by 76FJ55 View Post
But if you look at the yellow III from the first post and compare it to the black III in post 4 you will notice a design difference in the top half of the bodies. The black design matches the ones I cut and installed, but the yellow ones don't appear to have the constant diameter upper which allows the addition I'd the clip groove.
Thanks for stating the obvious, I'd completely overlooked it.

Now that you mention it, I did some looking and there's a few types of "design III" bodies. The three attached pictures below are all 24lb Design III inhectors, all with different arrangements of grooves (note the greeny-blue ones are EV6 connectors - just included them as an example of grooves).

Interestingly, FiveO advertise the pink ones as being suitable for 85/86 928S.

From a look at those pics, I'm wondering whether the red ones are a direct fit on S4's and include the groove for the clip?

Has anyone used Design III injectors in an S4 that didn't require modifying to use the fuel rail clips?
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Old 03-16-2011, 07:40 PM
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I went to 4 hole type II's 2 years ago when doing an Intake R&R and also didn't replace the fuel rail covers. I've noticed no discernable noise increase from those changes.

I've also settled on 30lb injector size to go with Colin's Cam's and have been having the same debate re type II's which are plug and play or type III's with minor performance increase but some additional effort to get them safely fitted. The mod seems simple enough, I'd want it done on a lathe in order to ensure the grooves are all in exactly the same place, thickness and depth. I don't have Parkinsons, but neither are my hands steady enough for brain surgery
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Old 03-16-2011, 07:42 PM
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Originally Posted by cfc928gt View Post
A good site for comparing injector output and resistance based on bosch part # is http://www.polog40.co.uk/article_injector_table.php. It shows our stock 19# injectors, 0280150730, flow 201 CC/Min at 3 bar with 15.9 ohms resistance. Good site to use for ebay purchases.
Cheers for that link - I've also been using this list:

http://users.erols.com/srweiss/tableifc.htm#tabtop

Originally Posted by cfc928gt View Post
Interesting videos. In the last one it appears the design III and the pink top design II have a pretty similiar spray pattern while the yellow top doesn't seem to atomize quite as well.
Yep, in the first video, I'm pretty sure the design II and design III are injectors no. 4 and 7 respectively. Both open fast, and atomise well, but there is a minor difference in the spray pattern.

If I can find some design III's that are a drop-in replacement I'll go with them - would be good to put together a list of Bosch part numbers of design III injectors which have the correct grooves

Anyone with a stock injector to hand who can measure the distance to the clip groove from the top of the injector? All my stock ones are in cars at present. Then I can check photos online to scale (I have a used 19lb design III injector here on my desk to measure, to scale a photo correctly).

The fall-back is just go with the 4-hole design II's, which is hardly a bad outcome, but I may as well go with the slightly newer technology if I can find a good fit.

I also have a set of used 19lb design III's (yellow body without any grooves) - I was intending to buy new caps/o-rings for them and test fit them in one of my 87's when I'm doing its intake refresh. Injector-rehab sell all the bits to rebuild them (filters, o-rings, caps etc.).. http://injector-rehab.com/shop/home.php
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Old 03-16-2011, 07:59 PM
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Originally Posted by Hilton View Post

Anyone with a stock injector to hand who can measure the distance to the clip groove from the top of the injector? All my stock ones are in cars at present. Then I can check photos online to scale (I have a used 19lb design III injector here on my desk to measure, to scale a photo correctly).
I've got my old stock ones under the house in storage - Won't be back home untill Friday night, but happy to measure them then if no one responds in prior to that.
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Old 03-16-2011, 08:03 PM
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Just brainstorming, it might be possible to take a plastic ring, groove it, split it, and epoxy it to the body of the III.
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Old 03-16-2011, 10:34 PM
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I've got my original 24 lb injectors out of my 85 I can measure if that will work for you. I would think they would match dimensionally but don't know for sure. just let me know and i'll go out to the garage and grab one and the caliper. or this may have what your looking for. if there is anything in addition just specify an I'll try to get you the numbers.
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Old 03-16-2011, 11:21 PM
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Hilton,

Looks like the groove is 1mm thick and it's between 9 and 10mm from the top.

I looked at several other videos comparing the design II vs design III and the spray pattern is definately better with the III. One also commented that the IIIs were much quieter than the IIs. There was also one that increased the pressure slowly up to 120psi and the pattern stayed perfect. Seems we need to figure out a design III plug n play option.
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Old 03-17-2011, 12:01 AM
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Hilton
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Thanks Fred.

A quick search between working and checking the news turned up these as a likely 30lb injector..

$320 - http://www.fiveomotorsport.com/domes...rs/?itemid=303
$239 - http://www.summitracing.com/parts/FM...B302/?rtype=10
$209 - http://www.blueovalindustries.com/en7410.html
(all links are to the same injector - just keeping a list here as I look for pricing)

Bosch p/n 0280155759 Ford Racing p/n M-9593-BB302

They're 30lb (315cc) and have the additional grooves, high impedance (14.5 ohms). The top groove starts at 9mm from the top of the injector and is 1mm wide (i.e. ends 10mm), and the second grooved slots (not a complete circumference) start at 12.5mm down.

For reference I just measured a design III injector I have here and its 73mm exactly top to tip - the above rough measurements were taken by zooming the photo until the length is to scale, and holding calipers up against the screen.. rough but effective thanks to LCD flatscreens

Looking at Simon's diagrams above (thanks Simon), the lower groove on a design III is at 12.6-12.8mm, and the upper groove is at 8.6-9.5mm on a design II so my measurements are close enough to be useful. I'm guessing its a tolerance range on the diagrams.

So.. all that remains is to confirm the grooves on the injectors are as shown in the photo, and track down the best price I can find for a new set.

edit: attached a picture so you can clearly see the style of Design III body with the correct grooves

Originally Posted by cfc928gt View Post
Hilton,

Looks like the groove is 1mm thick and it's between 9 and 10mm from the top.

I looked at several other videos comparing the design II vs design III and the spray pattern is definately better with the III. One also commented that the IIIs were much quieter than the IIs. There was also one that increased the pressure slowly up to 120psi and the pattern stayed perfect. Seems we need to figure out a design III plug n play option.
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Last edited by Hilton; 03-17-2011 at 06:20 AM.
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Old 03-17-2011, 01:50 AM
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For the sake of simplicity - here's Bosch part numbers for the ones I'm turning up that have what appear to be the correct groove (i.e. should not require use of a dremel to fit the fuel rail clips) and correct (high) impedance for Bosch LH Jetronic:

Design III
19lb:
Bosch p/n 0 280 155 821 (unusual and expensive)
Bosch p/n 0 280 155 746 (common, found in Volvo 5 and 6cyl's)
Bosch p/n 0 280 155 702 (Volvo)

24lb:
Bosch p/n 0 280 156 013

30lb:
Bosch p/n 0 280 155 759 (aka Ford Racing p/n M-9593-BB302)

Design II (these look the same as stock ones but have 4 holes)
(note - when buying design II's, not all have the same grooves as stock injectors - those listed below do, just worth noting not all that look the shame shape as stock will fit)
19lb
Bosch p/n 0 280 150 943 (aka Ford p/n FOTE-D5A)
Bosch p/n 0 280 150 556 (aka Ford p/n FOTE-D5B)

33lb
Bosch p/n 0 280 150 431 (Saab)

If anyone wants to add to the list feel free to post and I'll add them - if you've got actual fitment experience even better If I get time in the next few days I'll try and add some bosch numbers for Design II injectors (old body style with 4 holes) - as there's no list of them on this forum either.

Last edited by Hilton; 03-18-2011 at 07:29 AM.
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Old 03-17-2011, 02:35 AM
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isn't the fuel rail bolted down? Can't remember. But if it were, would there be a need for fuel rail clips??
If the o-rings at both ends are large enough (meaning snug) the injector will stay in the bung and stay in the rail (provided it was bolted down).
Just a thought.
www.injectordynamics.com has great info on injector science too
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