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mjr
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2.5 injectors

Post by mjr »

Hi all,

Im just looking for an opinion on what others would do in my sitution.

to cut a long story short, I have been trying to get to the bottom of a rich running problem for a few months. I have replaced and tested everything, and the last on the list is the injectors and fuel pressure regulator.

Anyways. I have all the injectors out and ready for sending off for ultrasonic treatment. Im not sure weather to go ahead and get these cleaned at approx $110 for the set or whether to to order aset of BMW 633 bigger new injectors at $30 each. I am planning on upping CR, camming and head job later this year. so Im thinking that perhaps I should go with the 633 injectors? The question is the BMW injectors, which I think are bosch 208's IIRC, would I need the 633 ECU to go with it as well? by the time im done, I should be around 200hp, so would you guys go with the bigger injectors, or would you stay with the stock injectors? (I think they are probably adequate up to around 200hp) Would the 633 injectors plug straight in too?

thanks in advance
Greg Gordon
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Re: 2.5 injectors

Post by Greg Gordon »

I have experimented with this quite a bit for supercharging work.

On a stock or lightly modified engine, if you install the BMW injectors, they will fit right in. However the engine will run a little rich all the time and VERY rich at idle and full throttle. You can make adjustments to get the mixture good enough so it will idle OK, but you won't be able to do anything about the excessively rich mixture at full throttle.

If your engine inhales enough air because of a turbocharger/supercharger, cams and headwork, or whatever the BMW injectors will work pretty well.

The stock injectors can support about 200hp at the flywheel, but that's really about it. Any more and you are really pushing your luck.

You don't need the BMW ECU. The stock ALFA ECU is just fine.

Another option (commercial alert!) are my Stage 1 injectors. These are brand new and flow about 10% more than the stock GTV6 injectors. They work very well on a stock engine. We have them in matched sets and flow check them before shipping. I consider them ideal for exactly what you are doing.

Greg Gordon,
www.hiperformancestore.com
www.okinjectors.com
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mjr
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Re: 2.5 injectors

Post by mjr »

thats good info Greg, thanks. so basically the BMW injectors inject too much fuel for the duration on the standard ecu on a stock 2.5 then. well I dont want that at the mo, she runs rich enough as is! :lol: good to know re you stage 1/2 injectors though. Once I start pulling the engine apart, I will bear that in mind. I think for now I may well get the stock injectors serviced then, as its only $120 or so over here with the same cleaning rig you guys are using.

Im also going to fit an adjustable fuel pressure regualor, since Im replacing the stock one anyhow.
Greg Gordon
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Re: 2.5 injectors

Post by Greg Gordon »

Fair enough! Good luck, and let me know if I can help.

Greg
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Re: 2.5 injectors

Post by MR2 Zig »

Ok Greg,

Since we are on the subject of recomendations....

3.0
L-Jet
164s pistons
164s cams
California smog
Shankle headers
bigger AFM & your intake hose (afm off a Jaguar and worked well on the 2.5)
otherwise stock 1983 GTV6

What are your recomendations for injectors here. I have 2 sets that I think are the same. One from the 2.5 and one from the 3.0. Both sets look a bit grungy on the outside. I had heavy carbon deposits on the pistons when I took them out (had 3000 mi on rebuild and oil pump lower half came off the upper half. lost the last 2 rods and the crank as it siezed)


Thanks,
MR1 Zig (I made rate!)
Machinery Repairman USNR
Greg Gordon
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Re: 2.5 injectors

Post by Greg Gordon »

That's easy. Stage 1. The stock injectors are a little undersized for that application and Stage 2 injectors are simply too big, plus there is no way Stage 2s with L-Jet will pass California smog.

Greg
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mjr
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Re: 2.5 injectors

Post by mjr »

Well had the stock injectors back from ultrasonic treatment. there was an 8% imbalance before, and one injector was leaking, explains the crappy fuel consumption too. all were between 179 and 186cc flow before cleaning, varying. after cleaning, every injector (plus replaced leaky one) now at exactly 201cc @ 38psi. I would guess they will run at approx 190 195cc @ 35psi?? Anyway, running problem gone, and engine runs a lot smoother throughout rev band now too.
Greg Gordon
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Re: 2.5 injectors

Post by Greg Gordon »

That's good to hear, and it's pretty typical of injector servicing. The injectors on these cars are pretty old now, and rarely perform like new without overhaul.

Greg
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