JimmyBlack

Additional feedback: I tested on my DW200 over the weekend with Fuel fuse removed to avoid high power mode. 2 observations:
1. My hard starts hot and cold persisted (due to worn out 100k mi engine), with no improvements relating to Fuel circuit changes.
2. My fuel pressure usually on 59PSI dropped to 56PSI under heavy acceleration in 2nd gear (NA), so appears to be safe running a DW200 in low power mode on an NA.
My fuel pressure gauge powers down for a moment when cranking, so I don't have any observation on pressure spikes at start up.


My cold start issues (cranks for about 4 seconds before firing) began around the time I installed the DW200 and the weather started getting cooler, but it seems my starting issues are related to engine, and not the fuel pump swap.

Brettus

iTrader: (2)

Yeah ... The 200 shouldn't be a problem . I actually jumped the high speed relay to see what pressures i would see at startup.

FazdaRX_8

iTrader: (1)

Not that I could tell, its happy to stay at 68-70psi all day long maybe my car is stuck in high mode or doesn't he go into high mod

TeamRX8

iTrader: (25)

^^ and recirculating like a **** ...

JimmyBlack

Faz, sounds like your pressure regulator is non-stock (by design?). I think the manual states 55-65psi is "acceptable". From memory the manual has a test for fuel line leakages where it's OK to lose something like 5psi within 30 minutes of engine shutoff. Best check the manual for details, but if you want piece of mind running the higher pressure may be worth checking. Otherwise make sure you're packing a good fire extinguisher!


Regarding whether the Fuel relay is cutting in, I can easily see when this occurs in on my fuel pressure gauge. On a 2nd gear pull the pressure drops a few psi to around 57psi at mid RPM, then shoots up to about 61psi suddenly then settles at 60 through to the upper RPM range. On your FI setup I'd expect this might be more noticeable as you'd be sucking a lot more fuel (lower pressure) immediately before the Fuel relay kicks in.

4DRcoupe

well...i've managed to find a suitable outer bowl and done B's fuel pump mod.
the only difference i made is rather than drilling the holes around the bottom of outer bowl, i've drilled 4 holes towards the front and rear bottom of the outer bowl instead, leaving the sides 'hole-less'. I'll test this out on track in Sept and report back here.

Wish me luck!

FazdaRX_8

iTrader: (1)

ever sense I put in the fuel guage over a year ago its been reading high it goes down to about 65psi when I am cruising for a long time. I wouldn't be surprised if the guage was just faulty reading a few psi higher then normal.

logalinipoo

Has anyone considered some fuel cell foam blocking the partition so there is little chance to slosh fuel from side to side?

dannobre

iTrader: (3)

Did that...with plastic baffles on each side to Hold it. Worked well...but you need 2 pumps to make sure you get return from each side

4DRcoupe

will there be any concerns with the HDPE plastic bowl in the fuel for the long term?

Brettus

iTrader: (2)

I used to make petrol jerrycans ......... The HDPE we used for that was only slightly stiffer than the HDPE used for the likes of oil containers etc .Essentially it's the same material, it shouldn't degrade .

My biggest concern would be what happens when the fuel gets hot and the plastic becomes soft . It wont melt , but it might deform if it gets up around 100C.

skc

Boiling point for fuel is 95 degrees C so the plastic will get soft however, your car will be stalling by then anyway

4DRcoupe

melting point of hdpe is 130C, but at what temp will it starts to soften and deform?

usually what temperature will be the fuel be at?

logalinipoo

Throw it in a pot of boiling water and check to see how soft it gets.

Brettus

iTrader: (2)

It will depend a lot of factors . I wouldn't imagine the fuel in a stock system with stock pump etc will get more than 10 degrees hoter than ambient under racing conditions . But throw in a ffew things like :
Running it right down to empty
oversized pump
Lots of cruising at slow speed
High ambient temps
Exhaust modifications
etc etc

I imagine with the wrong combination the fuel could boil as skc mentioned earlier.

Brettus

iTrader: (2)

Anything at all to report ? Or do we have to wait till Sept ?

4DRcoupe

haha...sorry Brettus, only in Sept when i go to the track would be the ultimate test. i'm just hoping the hot ambient temps of about 35C wouldn't 'spoil' anything...

4DRcoupe

went on a drive to the track which is about 3.5 hours away, hoping to have resolved my fuel issues.

with a full tank on the track, all seems fine for the first couple of 'warmup' laps after which i really going for it.

Bam! high speed high G left corners, it happens again...my fuel pressure drops!
i went for it again a few times and it always happen the same thing until it will also happen on right turns and ultimately starts happening on the straights.

off the track and while slow speed and idle, my fuel pressure would drops too and car stalled. managed to start it up after a few tries and made it home with 3 stalls along the way.

once reached home, it stalled and never fire up again. Thank God!
Removed the DW and fit in a used working Walbro and car is working fine now at least.

my DW is only about 3months old and before this DW, i've replaced 2 new stock pumps due to the exact same issue.

what could have caused my fuel pumps to fail once and again? it always happen on track. due to the long drive to the track? rest of my friend's rx8 who travel the same long distances don't have any issues at all.

i've noticed that the circuit and fuel relays get quite hot, is it normal? what else to check?

sorry Brettus, couldn't really test out the bowl design yet...sad.

nycgps

iTrader: (1)

it seems like you have a wiring problem somewhere

Brettus

iTrader: (2)

Sounds like the internal high pressure filter is clogged ...... You need the complete assembly to replace it .............

If you get one , cut the old one up and have a look inside ..........

4DRcoupe

nycgps:
ya...thinking it could be wiring or maybe the relay?
but once i changed the pump, everything is fine, could the pump have been 'damaged' by bad wiring or relays? after i pulled the DW out immediately after it died, it was hot! the relays were quite hot too.
i'm thinking to run new wires and relays.

Brettus:
internal filter clogged? i don't think so as my previous 2 stock pump assemblies were brand new and both failed within 3 months at the track with the same issue.
after failures of the 2 new stock pump assemblies, that's when i decided to install a fuel pressure meter.

4DRcoupe

btw, when i pulled the pump assembly, i checked the HDPE bowl and it was softer...

logalinipoo

It sounds like there is an underlying problem causing pumps to go bad. Try checking pump voltage.

RotaryMachineRx

iTrader: (1)

I changed out my stock pump a couple years ago to a Walbro. I was seeing 60-61 PSI on the pressure gauge when eventually it started to drop lower and lower until I saw pressure ranges of about 52-58 PSI. I replaced the Walbro last year with a DW200 and I consistently see pressures between 52psi and 58psi. Typically runs around 56PSI then when I floor it and fully spool up I see the pressure drop pretty linearly through the RPM band down to about 52 or 53PSI. I always keep a close eye on my AFR's through both the COBB and my AEM Wideband and it doesnt seem to be affecting my AFR's so I chalked it up to being an inaccurate gauge (Autometer mechancial gauge). After reading through this I'm hearing people say that their pressure is increasing when they accelerate..... Is there a chance I am having issues with my pump kicking into high speed? or apart from seeming a bit low of pressure is this pretty typical for some of you other FI guys?

Brettus

iTrader: (2)

Ok . How about the first stage resistor ? Is it possible that is shorted out and running the pump at full speed continuously . Or the reverse , resistance has increased to the point it runs too slow and the pump motor overheats as a result of that ? What do you get when you run an ohmeter across it ?