Leaking injectors, required maintiance.

I had a bad 360 motor in the shop on the floor with 120,000 or so miles. It was a daily driver. We had cars come in regularly with symptoms of bad injectors and since it was so easy on a 360 we would swap rails to see if that fixed a cars problems.

Those 120,000 mile, never touched injectors worked better than the ones we tested with 10-20,000 miles. They were perfect.

Lots of things can cause injector problems but non use is the worst.

 

Injectors are wear items, but RC-ENG has always been good to me with rebuilding injectors.

 

what are some symptoms of bad injectors?

is rebuilding/testing/cleaning them the only option.

there was a thread in the past about aftermarket 355 injectiors
but it was highly advised against. and only to use oem 355 injectors.

are oem injectors still available to purchase?

 

I have heard that it is not just the clogging, but more the seals that go bad and cause problems. Do not know if any internal seals or outside seals are meant (outside sounds easy of course).
Can seals be replaced on these injectors, or is a bad seal end-of-story?

 

What is the original spec for flow rate?

 

272cc/min

You might have been able to purchase new injectors for about the same price. I know that the 650cc/min injectors that I am switching to are only going to set me back $169 for the set plus shipping.

 

They sound big, until you consider this.

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Just one... LOL. Seems wrong doesn't it. This is not my first rodeo either. That's a 77mm inducer with a 98mm compressor wheel and big a 35 lb hunk of metal.

So why just one? Because it allows me to greatly simplify the whole system. Now I know that joining the two exhaust streams in a flat plane V8 could cause reversion, but that is why I am using a twin scroll T4 housing. The turbo prevents reversion. The system will have dual 38mm waste gates. Outlet air will go into a relatively small intercooler, but the SPAL fan and ducted air feed should keep efficiency high despite the compact size. Low boost levels will also help reduce thermal load. I have it pretty well thought out. Sorry for the hijack.

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So, if injectors are not flowing at spec rate a longer injector pulse is required to keep A/F ratio at the desired point. This should result in a positive LT fuel trim. I.E. if injectors are not flowing at spec you would expect to see positive LT fuel trim. If spec is 270 and you actually had 250 you should see about +8% LT fuel trim, assuming no other problems.

 

Assuming that the injector was tested at the same pressure as the spec. If the spec pressure flow was 8 percent higher than the pressure used, you would see no significant change in fuel trim. Additionally, that long term trim assumes no other reason to trim negatively.

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Yea, that what "assuming no other problems" means.

 

I said no other reasons... For example an inaccurate sensor, decreased flow due to port differences, dirty filters, efficiency in catalyst flow, o2 sensor accuracy, etc, etc.

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Single 77 on a 3.5l. You must want a harder hit than an F40 Good thing you have almost 9k rpm to work with.

Are you doing this now with your current rebuild? What do you plan to use for engine management?

 

I am going with the MS3-Pro. Yes, I might have to tighten up the exhaust A/R. I would like the turbo to begin spooling around 3.5k-4k RPM.


I will start a thread for continued discussion on this.


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Neat, hopefully flex fuel if you have E85 available. I'll toss my wrench in it and vote for twins and the y-pipe as a perfect wastegate location. Only because I think you would prefer the response of twin GT3071r's....or so

 

Yes John you make perfect sense. I think what Mark might be thinking too (sticking to the bad injector thing) you could have one injector leaking and one injector lean cancel each other out and not alter the LTFT, ie "other problems." So I think looking at LTFT is a good idea but there is still not good way to see if injectors are doing their job. As RD said sitting is death. So in my case Ferraris are not used as daily drivers. Therefore, I send out my injectors for service every time I do a major service as part of my major service routine. I have advocated that addition as the cars have gotten increasingly dependent on multiple systems working well together for a good running car. We sure have come a long way from a bowl of gas, floats, and venturis.

 

LOL! Well past my area of expertise on that one