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Cracked my BOA overfuelling
NeilP - 1/7/07 at 09:10 PM

Car wasn't accelerating right over 4500rpm - Been trying a lot of things (which in a way has been good as I've checked the output from every bloody sensor on it) but was getting nowhere. Anyway, tonight changed back the fuel pressure regulator from 4 bar to 3 bar and bingo!

The injectors (green top) clearly couldn't cope with a higher delivery pressure so I was effectively quenching when it was on high fuelling (mine is a 91 cosworth and apparently they didn't get everything sorted to about 93).

It was fairly mad before even with this glitch so it is just bonkers now - Cannot believe the acceleration from 3500 to 6000. Took mother-in-law up the road to check it out - She may never speak to me again


mark-wiring - 1/7/07 at 09:25 PM

Well that can only be a good thing if she talks to you again ask john to borrow the beast when its done that should sort it lol


jollygreengiant - 2/7/07 at 03:54 AM

Just been told, my mother-in-law is moving out permanently in 3 weeks time.



This means I've got about 2 weeks to get my engine running (no exhaust & directly under her room).
Did have it running last friday night, but that doesn't count. I woke up a short while later.


OH yes, sorry. Well done on getting your running issues sorted Neil.

[Edited on 2/7/07 by jollygreengiant]


garage19 - 2/7/07 at 06:24 AM

Why on earth did you turn the fuel pressure up in the first place????

It would have meant you were delivering approx a third more fuel than you actually needed all across the rev range. Madness!

Glad you have it sorted now.

quote:
Originally posted by NeilP
Car wasn't accelerating right over 4500rpm - Been trying a lot of things (which in a way has been good as I've checked the output from every bloody sensor on it) but was getting nowhere. Anyway, tonight changed back the fuel pressure regulator from 4 bar to 3 bar and bingo!

The injectors (green top) clearly couldn't cope with a higher delivery pressure so I was effectively quenching when it was on high fuelling (mine is a 91 cosworth and apparently they didn't get everything sorted to about 93).

It was fairly mad before even with this glitch so it is just bonkers now - Cannot believe the acceleration from 3500 to 6000. Took mother-in-law up the road to check it out - She may never speak to me again


MikeRJ - 2/7/07 at 05:35 PM

quote:
Originally posted by garage19
Why on earth did you turn the fuel pressure up in the first place????

It would have meant you were delivering approx a third more fuel than you actually needed all across the rev range. Madness!


About 15% more, since flow is proportional to the square root of the pressure. Turning it up does seem a strange thing to do unless the OP was trying to compensate for something else.


NeilP - 3/7/07 at 06:56 PM

quote:
Originally posted by MikeRJ
quote:
Originally posted by garage19
Why on earth did you turn the fuel pressure up in the first place????

It would have meant you were delivering approx a third more fuel than you actually needed all across the rev range. Madness!


About 15% more, since flow is proportional to the square root of the pressure. Turning it up does seem a strange thing to do unless the OP was trying to compensate for something else.


Apparently on some BOAs an uprated FPR can give you 20bhp (and there was one lying around) - Seems that (as usual with Ford) there are variants on variants with components and therefore my injectors weren't up to the job of controlling the flow at this higher pressure. Bear in mind that the BOA got radically detuned by Cosworth as the original engine was 300bhp and the Granny couldn't put it down - there are therefore (I am led to believe) a number of fairly cheap tweaks that can release a fair chunk of power.

I'm sure that the science is in contradition to this...


mark-wiring - 4/7/07 at 03:24 PM

first thing is a radical re-design of the inlet system as that is where most of the de-tune went on neil then cams and there you go around 300 bhp.

I got quoted loads of money when i looked into it but if you wanna have a talk to the guys that know find the number for merlin race engines ( think there listed on jenvey's web site)


saigonij - 4/7/07 at 04:50 PM

BOA engine with BOB exhaust cams and washers can add a bit to extra power.