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Old 02-24-2011, 11:29 AM   #1
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Default Fuel Pressure/Supply.

I recently had a good used engine swapped into my 92' Eunos Roadster (oil pump on the old engine died), at the same time I had the mechanic fit the FM dual-feed fuel rail that had been waiting to be fitted for several months.

Those were the only changes that were made. Ok, so I realise an engine change is probably the BIGGEST change you can make, but it was a straight like-for-like swap.

Since the work was done the fuelling has been off the ball, where before I used to see 11-12:1 AFR in boost I now see 13:1+ in boost.
Needless to say I've been keeping out of boost and have driven the car very little, only to check the guages and see what was going on.

I haven't yet managed to hook a laptop up to the Emanage to see what's going on (software driver issues with the cable), and I'm sure I have enough headroom in the injectors to dial out most if not all of the under-fuelling in boost.

I'd be interested in opinions on any other possible causes of this fuelling issue and any short term ways of perhaps boosting fuel pressure at the rail to ease the duty cycle on the injectors (eg fitting an AFPR or high-flow fuel pump) as I'll be going the Megasquirt or Adaptronic route before the end of this year.

Spec below...

92' Eunos Roadster 1.6, TD04 turbo, intercooler, 320cc injectors, FM fuel rail, stock pump, GReddy Emanage Blue, O2 clamp, running at approx 6psi.
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Old 02-24-2011, 11:40 AM   #2
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New engine = New injectors and FPR.

you could swap in your old ones and see what happens (maybe one of the new ones is clogged up?)

I'm a newb, wait for others to respond
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Old 02-24-2011, 11:45 AM   #3
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when I say a "good use engine" was fitted, basically (at least in the UK) when you get a used engine it comes without ancilliarlies (ie. intake, exhaust, starter motor etc), you simply get the block and the head.

So the injectors, stock FPR, intake manifold etc are all the same as before.
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Old 02-24-2011, 11:52 AM   #4
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your old motor, was it tired?

you're probably making more power now, more power = more fuel consumption needed to support the horses.
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Old 02-24-2011, 12:05 PM   #5
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well, the old engine had around 90k (miles) on it, the "new" engine allegedly has around 70k on it.

It's a possibility I'd not considered to be honest
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Old 02-24-2011, 12:07 PM   #6
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I've replaced a transmission that was bad that caused me to go lean, since there was so much friction losses being wasted driving the trans, I had to retune the fuel when it was replaced. Likewise, this same thing has happened when I've replaced a worn block, with a fresh one. If it's more efficient, it will require more fuel.
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Old 02-26-2011, 02:24 AM   #7
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how much fuel pressure should i get when floor it!?
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Old 02-26-2011, 03:23 AM   #8
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Quote:
Originally Posted by c41250n View Post
how much fuel pressure should i get when floor it!?
When you're flooring it, the FPR should be maintaining close to the same pressure. Unplugging the vacuum line from mine with the car sitting still raised it about 10 psi if I remember correctly.
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