Bosch 044 fitted: Surging even worse! :( - Page 8 - Perth-WRX.com

Intra · #71 05-11-2006, 05:03 PM

Tode.. for the sake of that engine... S T O P!

get it to a workshop and get it looked at.. really... DET is like aids.. once you have it.. its there for life.. it aint gonna disappear by itself and some how magically regrow the chunks of piston & valves.

Seriously, when that puppy let's go.. its gonna let go in a big way........

waxdass · #72 05-11-2006, 05:33 PM

car is not pushed at all, infact i let go once it starts going lean.
AFR's are very good on cruise, so driving it around without boost is no probs

i dont need a dyno anymore, i know what the prob is and what AFR's it reads

tuna · #73 05-11-2006, 06:08 PM

Quote:

Originally Posted by waxdass

ok so we found the problem!

mate hooked up his wide band sensor - took it for a lap, car runs fine - as per tune, starts to go rich on boost - hits 35-4000rpm then BANG! shoots very lean in a split second. car is fine off boost. AFR's at idle is mid 16's. bit lean ?

So its definatly hitting a lean spot, so we then hooked up a fuel pressure gauge, took it for another lap. at idel fuel pressure measured a normal 230-250 kpa.
however when it starts to see boost, fuel pressure drops to 200kpa..
so its not gettin enough fuel,
my mate said its the ecu and how it controls the duty cycle to the pump, ie; not giving enough voltage when it needs it. This is weird, not sure how exactly it control the fuel pump... although it was strange how the stock fuel assembly and pump did not hit surge at all
On thursday, we are going to fix this problem by wiring up a relay, that will give the pump full voltage. This should be the problem, if not its the fuel reg.

to be continued....

tode, the fuel pump is already wired up on a relay, nothing more you can do to the wiring is going to fix it.

also, fuel pressure on a standard fuel regulator is 299.1 kpa (or simply 300kpa or 43psi) regulated against manifold air pressure. at idle this equates to around 260-270 kpa.

where abouts are you measuring fuel pressure? was kind of measuring device was it?

http://members.iinet.net.au/~tuna/Tu...Regulators.pdf

if your really looking for a problem with fuel pressure, you need to use a differential fuel pressure sensor, which compares fuel return vs fuel delivery to give you an accurate absolute fuel rail pressure.

bear in mind also that once a car starts to detonate, its downhill from there, detonation damages the pistons to the point where detonation is unavoidable at even mild boost levels. check your spark plugs for aluminium dust and burnt electrodes, as these are tell tale signs of a distressed engine.

BALISTC · #74 05-11-2006, 06:11 PM

Tode, do you think this has to do with a certain workshop "modifying" your fuel pressure regulator?

waxdass · #75 06-11-2006, 01:13 AM

im not sure, i'l wait till thursday to see what happens
It doesnt look like my fuel reg has really been mnodified... they just tried to tap it..

the spark plugs were pulled out by a workshop last week, they looked fine, just signs from running rich.

LegacyGT · #76 06-11-2006, 02:32 PM

BANG yet?

sikkhunt

waxdass · #77 08-11-2006, 01:30 PM

OK

ran some more tests, it doesnt seem like its a voltage problem (ran another relay). didnt fix anything.
Its not the fuel reg, we blocked the fuel return hose - the car still lost fuel pressure

So its either a blockage in a fuel line (very unlikely - since non of that stuff has been touched)

or its back down to the fuel pump.. very weird. Going to try another pump out today see if it helps