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needing bigger injectors/fuel reg? 

 

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Posted: Thu Dec 29, 2005 5:59 pm 
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yep - hence why i'd like to just get it all done once - i'm going to do as much as i can when the engine will be swapped over, and want to do it so that it doesn't have to be touched again! :)

 

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Posted: Thu Dec 29, 2005 6:04 pm 
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if you want to do it all at once go for 24lb injectors and 3.2 bar on the rail. Thats what saloon cars use to get a genuine 160 at the wheels.

And yeah, dont foget the tuning

 

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Posted: Thu Dec 29, 2005 6:11 pm 
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24# @ 3.2bar would also leave a fair bit of headroom i imagine... headroom is good :)

 

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Posted: Thu Dec 29, 2005 6:12 pm 
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what kind of $$$ and where should i be looking for these? :? assume i know nothing, because i really don't! lol. much appreciative of the help though! :wink:

 

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Posted: Thu Dec 29, 2005 6:16 pm 
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My local wreckers have 24lb injectors for $11 each. Fuel regs from ebay (dont skimp though).

 

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Posted: Mon Jan 02, 2006 12:58 pm 
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I reckon stock injectors are fine on any E-AU series non turbo or supercharged engine. With a good stock or XR fuel pump at sensible AFR's they are good for just about up to 180rwkw. I doubt there is any real problem running injectors up to 95% of their duty cycle as long as its not prolonged or over too much of the rev range.

Few engines are that good they need bigger injectors really. spend the dough where its needed.
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Posted: Mon Jan 02, 2006 2:30 pm 
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jonbays wrote:
I reckon stock injectors are fine on any E-AU series non turbo or supercharged engine. With a good stock or XR fuel pump at sensible AFR's they are good for just about up to 180rwkw. I doubt there is any real problem running injectors up to 95% of their duty cycle as long as its not prolonged or over too much of the rev range.

Few engines are that good they need bigger injectors really. spend the dough where its needed.


Dangerous advice.

Tell me again whats the difference between a stock and xr fuel pump?

Do you know all the reasons why you want to keep duty cycle to safe levels?

 

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Posted: Mon Jan 02, 2006 3:03 pm 
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Tell us all then what is the difference between a stock and an XR fuel pump? Is the regulator the only difference?

And whats the problem with running the injectors up to the max duty cycle? If the AFR's still OK and you can always up the fuel pressure a bit from from stock why would you need to change them this side of 180rwkw of course.

I really don't think N/A OHC falcons need bigger injectors untill you are well past street and strip and into full on race only engines
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Posted: Mon Jan 02, 2006 3:25 pm 
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Yep - no difference between stock and xr fuel pumps. XR's just have more fuel pressue via reg.

There are several problems with running injectors at high duty cycles. Reduced lifespan due to more heat, inability to accurately control fuel flow approaching 100% DC, no room to move for enrichments at high rpm/load. I know there are some cars that seem to be able to stretch the stock fuel system a long way, but you have to ask yourself how safe/reliable this is in the long term.

When I first asked about injector size some time ago I was told pretty much what your saying now - dont worry about it, they are good for big power figures. When I checked it out though, it definately wasnt fine. Now that I have looked into this problem at length I see that these cars seem to be the exception to the rule in that they are able to get alot more fuel in.

My advice, dont base your decision on what is happening with other cars - measure the duty cycle and AFR to see how your car fairs with fuel deliver. I now have 24lb injectors and they are hitting 95% duty cycle by 6000rpm and 12.8AFR. Im guessing the power levels are low to mid 150's now. On paper this is more fuel than others with more power than me, but its what the engine needs.

 

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Posted: Mon Jan 02, 2006 4:47 pm 
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Sensible to check your own motor out for sure.

Stockstandard yours seems to be wanting a lot of fuel even if it is revving pretty high to 6000rpm I would have thought the bigger injectotrs would have coped much better. I have run on a couple of dynos and on one I was running 13.4 AFR and on another only days later 11.8 so it may pay to confirm the AFR are correct.

I have seen a stock injector car running 174rwkw and its AFR's were fine don't know what the duty cycle was like though. Also I would say this dyno was an optimistic one probably reading 10kw higher than a "fair" one.

On mine with lets say 135-145rwkw i can tell you from the Unichip tune which was pulling fuel out most of the time up to 5500 rpm I have heaps of headroom in the stock injectors. Enough for a bigger cam and a ported head before i would worry about my injectors
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Posted: Mon Jan 02, 2006 6:03 pm 
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jonbays wrote:
Sensible to check your own motor out for sure.

Stockstandard yours seems to be wanting a lot of fuel even if it is revving pretty high to 6000rpm I would have thought the bigger injectotrs would have coped much better. I have run on a couple of dynos and on one I was running 13.4 AFR and on another only days later 11.8 so it may pay to confirm the AFR are correct.

I have seen a stock injector car running 174rwkw and its AFR's were fine don't know what the duty cycle was like though. Also I would say this dyno was an optimistic one probably reading 10kw higher than a "fair" one.

On mine with lets say 135-145rwkw i can tell you from the Unichip tune which was pulling fuel out most of the time up to 5500 rpm I have heaps of headroom in the stock injectors. Enough for a bigger cam and a ported head before i would worry about my injectors


My AFR is measured with a wideband O2 sensor mounted before the cat so its probably much more accurate than one mounted in the tip like at the dyno.

My chiptorque tune was the same. It pulled massive amounts of fuel away in the low end->mid range. Top end though it just couldnt get enough. I tried to talk to chiptorque about it but by the sounds of it they were very busy and didnt have the time to sit down with my tune and check out what was going on. Im not complaining though - gave me the motivation to install the MS2!

 

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Posted: Mon Jan 02, 2006 7:08 pm 
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jonbays wrote:
On mine with lets say 135-145rwkw i can tell you from the Unichip tune which was pulling fuel out most of the time up to 5500 rpm I have heaps of headroom in the stock injectors. Enough for a bigger cam and a ported head before i would worry about my injectors


Your unichip wasn't pulling fuel out, it was leaning out the AFR targets that the EEC were asking for. The fact is that stock injectors do not have very much headroom and any more than 130-140rwkw will put them well above the specified 80% duty cycle limit. AFR is one thing but no decent tuner will allow injectors to run at 90-100% duty cycle without major concerns.

You can get 160-170rwkw out of stock injectors, this has been prooven a few times, however the fact that their AFR's remain in a decent range is not really anything to do with the injectors themselves. At 100% duty cycle (and even much above 80%DC) the injectors do not close therefore there is no way they can be responsible for the the resulting AFR. The fairly stable AFR is more to do with volumetric efficiency decreasing in the upper rpm range meaning less fuel is required. Stock injectors will work on N/A engines with 130-170rwkw and its a cheap and easy solution for a street car, but it's not the ideal way to do things.
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