KEVWRX95

I have a Jap WRX 95, with modifications the list as follows:
Forged internals
MD309 TURBO
Blitz air filter
Hks dump valve
original 380cc injectors
H+s up pipe
HKS exhaust/down pipe (no cats)
Samco hosing
Uprated fuel pump/fuel filter
FSE fuel regulator
Fuel rails now running 3 bar of pressure
Parallel fuel feed
Original ecu was at 12 psi
Now running a prodrive chip upto 16-17 psi
Iridium hks spark plugs
When I drive the car under boost I get 16-17 psi on my boost gauge but when I get to about 4500 to 5000 revs I get a massive stutter and either I have to change gear or completely back off the gas, even in fifth gear when I get up to about 5000 revs I get the massive stutter and almost headbutt the steering wheel.
Can anyone confirm that either I'm hitting fuel cut (which I thought was at about 19 psi),or because I have a Hybrid turbo thats bigger more powerful, etc etc, that my little 380cc injectors cannot keep up??????? after 5000 revs? Does this all mean I have to go for a proper re map?
If anyone else can advise me it would be much appreciated as after fitting this turbo I was looking forward to a bit of fun!!!!! Cheers Kev.

iain atkins

Kev

one vote here for fuel cut!! Remember boost gauges are not always 100% accurate, and i would have thought that 17psi would have been getting very close to the MY95 ppp fuel cut. Does it hold 17 or spike to 17. If it holds 17 then when pulling hard in 4th or 5th etc it's gonna spike a bit (maybe 1 sometimes 2psi) which would definately be enough to give fuel cut IMHO

Cheers



Iain

KEVWRX95

Thanks Iain,
How do I combat this then?
How do I raise the fuel cut as the ECU is not re mappable?
Kev.

nom

Not sure it's fuel cut - quite possibly simply more fuel than the injectors can supply is needed! MD309 with 380cc injectors is an interesting mix...

KEVWRX95

The 380cc injectors are not by choice, it's just the bank balance has taken a bit of a battering with the recent mods, so in the future I would love to get bigger injectors,front mount and then the link or motec...............I just have to try to live with the car for now.However driving today rather than flooring it in every gear I slowly built the speed up in each gear and managed to get past 5000 revs on the motorway and reach speeds slightly above *cough* 70mph, so I just have to drive it in a certain manner............still good fun though.

Trout

iTrader: (1)

Agree with nom.

On my car - with an MD309 and 740inj I run around 70% duty cycle at 4 bar fuel pressure!!! So your little 380s must be really struggling

Rannoch

dhorwich

I think the fuel cut on an MY95 WRX is around 15.5psi..!!

Dan

jonny gav

iTrader: (1)

sounds to me like fuel cut too, if you have some sort of boost controller on the car try running it at around 1 bar (15 psi) as fuel cut on the standard ECU is at around 16psi.

RB5108

That's the conclusion we have reached too.

Oh well Kev looks like the cupra will be staying just behind you until you get a link/motec and bigger injectors, just need to sort the handling out

Revo'ed cupraboy

dhorwich

or just buy a fuel cut raiser

Dan

KEVWRX95

As mentioned before I have the prodrive chip which I thought takes the boost upto around 16-17 psi and I thought fuel cut was around 19 psi
However thanks for all the views and I probably agree that my injectors are maybe working at 100% and they need to be enlarged!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! I take it then in the future 740cc injectors are what I need to buy?
At the moment my fuel rail is running 3 bar of pressure, as mentioned earlier is it worth upping that to 4 bar or won't that make any difference at all as you believe my injectors are struggling?
Hello Bryan speak to you later.

RB5108

I would leave it at 3 bar any more may cause bore wash, what do you guys think?

[Edited by RB5108 - 8/23/2003 10:08:12 PM]

Omen1

fuel cut defencer from HKS price about $100.00 USD

Dyney

Kev,
Call me (Bryan has my no.) I think I have a way to prove if it's Fuel cut or not

tweenierob

Your fuel cut is 17.5psi, that is all the std Map sensor can read to.
When i had the old 380's in my scoob i used to max them out day in day out without any stuttering..
When you do upgrade your injectors in the future 740's may be slightly overkill the first step up from 380's is normally a set of 440's from an STI car. Anymore than 3bar on 380's wont give borewash i would run more pressure than that anyway.. prob or not..

Rob

Scott.T

iTrader: (2)

It's FUEL-CUT

Prodrive Chip is 13.64psi peak & fuel-cut is 15.65psi
So you ain't running a Prodrive Map.

The name rings a bell so maybe you are running one of my 16.5psi maps in a Z4 ECU, which has the fuel-cut set at 18.12psi.

Doh! just realised who you are....you are/where running a 14psi map that I supplied.

If you still have that chip/scoobuECU fitted then it sounds like something you have changed i.e turbo/induction/engine is causing the duty cycle to overshoot the target values in the map (probably the new turbo). Either that or your boost gauge is well in-accurate.

Also that's a shed load of boost for the timing in that map !!!!

Stick a volt meter on the Map sensor input to the ECU and see how it ties up with these values :
Best viewed in EDIT mode
kPa mmHg PSI Bar mv
-26.7 -200 -3.87 -0.267 2100
-21.36 -160 -3.096 -0.2136 2200
-16.02 -120 -2.322 -0.1602 2300
-10.68 -80 -1.548 -0.1068 2400
-5.34 -40 -0.774 -0.0534 2500
0 0 0 0 2600
5.34 40 0.774 0.0534 2700
10.68 80 1.548 0.1068 2800
16.02 120 2.322 0.1602 2900
21.36 160 3.096 0.2136 3000
26.7 200 3.87 0.267 3100
32.04 240 4.644 0.3204 3200
37.38 280 5.418 0.3738 3300
42.72 320 6.192 0.4272 3400
48.06 360 6.966 0.4806 3500
53.4 400 7.74 0.534 3600
58.74 440 8.514 0.5874 3700
64.08 480 9.288 0.6408 3800
69.42 520 10.062 0.6942 3900
74.76 560 10.836 0.7476 4000
80.1 600 11.61 0.801 4100
85.44 640 12.384 0.8544 4200
90.78 680 13.158 0.9078 4300
96.12 720 13.932 0.9612 4400
101.46 760 14.706 1.0146 4500
106.8 800 15.48 1.068 4600
112.14 840 16.254 1.1214 4700
117.48 880 17.028 1.1748 4800
122.82 920 17.802 1.2282 4900
128.16 960 18.576 1.2816 5000

[Edited by Scott.T - 8/25/2003 6:10:52 PM]

KEVWRX95

Tweenierob what is a safe pressure on my fuel lines, bearing in mind I have done the parallel fuel feed , so most of the lines are not metal but the braided 7mm rubber fuel hose? Will increasing the pressure improve the driving of my car as it does feel a little lumpy, and will it also mean that the fuel cut will still come in at 18 psi no matter what as the 380 inj are at their limits?
Scott, hello, yes you are right I have got one of your chips, does this mean that it is possible to raise the fuel cut limit on my chip to stop this happening? If you want to, e mail me privately, as this bloody fuel cut is annoying me, and for now I cant afford bigger injectors and a re map!!!!!!!!!!!!! S o if you can help with this it would be appreciated.
Kev.

Scott.T

iTrader: (2)

Could probably do a map to 16.5psi if you have a Z4 ECU or 15.5psi if not (There is a hidden value in the early ECU @ approx 17.5psi, that causes it to fuel-cut regardless of what you set the level to).

The map you have is set to 14psi, but the better performance from your new turbo is casuing it to overshoot it's target. Hence the increased boost and inevitable fuel-cut.

If you can manage to drive round the fuel-cut you my find that actual boost settles to either the target of 14psi or a little higher (dependant if the duty cycle can compensate enough).

I have recently had to remap a wagon that was overshooting the target due to it having a TD04. So I have a good idea of the percentage to decrease.

If you can make it to the sussex meet on Saturday then I will bring a couple of maps for you to try.

Mail me offline to talk more and also to talk money !!!!