Classic Audi Technical Mech/Tech Engine » 7A replacement bosch injectors discussion

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Old 20-01-15, 12:02 PM   #1
PoloGaz
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Default 7A replacement bosch injectors discussion

I've been looking at putting bosch injectors in my 7A.

By means of comparison; The original hitachi injectors are quoted as 305cc - but at what pressure - I guess 4.2bar?

Already bought the adapters and some injectors some time ago after some initial research. Here's what I found out.

The current 034 kit comes with 0280 155 759 red injectors; rated at 315cc @ 3bar AFAIK

A few people on various forums discussing this modification have said these are too large for the 7A unless you are looking to make significant modifications to it.

I've been looking at the grey injectors used in some articles I've seen; 0280155931 including this one; http://www.audiworld.com/tech/eng83.shtml which are the original injectors sold in the 034 kit, and documented in the June 2006 audi driver magazine article 20vcqdriver kindly sent me.

Some of the data I've found suggests these are 300 cc injectors but I have just found some info on an American forum that says they're actually more like 250cc (@ 3bar), and there are a few other sites advertising them as 24lb/hr @ 3bar

http://ls1tech.com/forums/fueling-in...155-931-a.html

There is an alternative 250cc @ 3bar bosch injector; 0280 155 832 pink fitted to Volvo straight 6s - the difference is the impedance is 12 ohm instead of 14 ohm. These injectors are readily available and cheap as chips compared to the greys. So cheap I took a punt on some.

I'm curious as to whether 12 ohm impedance is sufficient to not fry the ECU when I ditch the resistor pack. I will be doing some measuring this weekend to see if it is!

Anyone have any thoughts/comments?

Gaz
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Old 20-01-15, 03:21 PM   #2
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The 7A uses a 4.2 bar FPR so an injector rated at 250 at 3 bar will be flowing closer to 300 at 4.2 bar.

The spec for the injector is 100-120ml for 20 seconds.

It's the grey LS1 injectors I'm using in mine. Had no problems with them. A set of 8 cost me $120
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Old 20-01-15, 05:30 PM   #3
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That's a great price! I got 6 Volvo ones for 75. Quick look on eBay for the 931s and they come up at around $100 each!

As for the pressure I was just using 3 bar as a reference as that's what's normally quoted. so as long as what I have are the same flow rate as the greys are at the same pressure, I should be good to go!

Last edited by PoloGaz; 20-01-15 at 05:33 PM.
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Old 20-01-15, 08:22 PM   #4
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Think I got lucky as it was about 4 years ago.

No idea if the Volvo ones will work but if they flow ~250 at 3 bar, you won't be running lean. I don't see the resistance being a problem. The Hitachi resistance is about 2.5 ohms per injector
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Old 21-01-15, 10:16 AM   #5
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Thanks for the reassurance - The key seems to be the impedance, the dimesions of injector are the same - the '155' part signifies that. They are 4 nozzle and other than that I don't know how else they could vary. I guess in a lot of ways internally but info is scare on that level.

The only negative would be the colour I guess!



vs





Actually - just noticed the position for the retaining clip is in a different place. but I don't think the retaining clips are used with the adaptors?
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Old 07-02-15, 10:04 PM   #6
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Update on this... The injectors are now fitted onto the manifold. Had to take the manifold off because the injector ports were filthy and taking the manifold off seemed like the only way to clean them. I took the white disc off each injector nozzle but retained the rubber seal. This seemed like the right thing to do. Old injector seals were knackered
- at both ends on some of them

The resistance of the original injectors I measured to be 2.5 ohms with the resistor pack coming in at 6.5 ohms so approx 9 ohms in total. The pink injectors are 12 ohms so all good.

Last edited by PoloGaz; 07-02-15 at 10:07 PM.
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Old 07-03-15, 08:51 PM   #7
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how's this going?
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Old 07-03-15, 11:17 PM   #8
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Starting it up next weekend hopefully
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Old 07-03-15, 11:17 PM   #9
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Excellent I'll keep my eyes peeled for an update
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Old 16-03-15, 11:47 AM   #10
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Now running, you can see no1 injector is nice and pink!

Haven't driven it yet but I'm not expecting there to be any issues.

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