Loss Of Power Over 4k?

[Drakey]

Ok im confused all.

At first i thought it might of been adjustable cams were out. But i dont think it is that anymore.

So i have great power up till 4 k. I hit 3K and boost comes in strong and then hits 4k and it goes no where!

Even when im running 13psi instead of 9psi it makes no difference in power i have the same effect.

Im thinking its a fuel delivery problem? It feels as if there is not enough fuel after boost has come in to satisfy the amount needed.

I have bought a fuel filter to swap because that one looks old. After that im thinking fuel pump? if it isnt enough pressure.

I have also noticed my fuel economy go to shit! where i was getting 100k to 1/4 of a tank i now only get about 70km.

Could it be a timing issue at all? or a blocked exhaust? thats another thing i was thinking. Any help is appreciated....

mods are:

rb20det

r34 turbo

cooler

r34 fuel pump

running 9psi and 13psi

dump into 3inch all the way

Edited March 14, 2008 by Drakey

[Ultimategtr]

Could you describe the problem? is it spluttering, missing, flatspots??

Youre running the factory ecu? and the factory injectors?

my guess would be the injectors maxing out. have you tried running eg 7psi?

in saying that, it could also be a spark/coil issue - what plugs are u running(gap). have you had a GOOD look at the coils?

I would first turn check out the plugs and coils closely.. inspect the plug tips closely( i think white means the cylinders leaning out, brown is rich and black is oil). if that checks out ok, try putting new plugs in eg NGK .7mm coppers HR7(you would want a colder plug perhaps).

if the tips are ok, then i would suspect it to be ur injectors maxing out.

in saying that, it could also be a collapsed cat.. do the easy ones first as ur problem will most likely be something simple.

[FATAZZ]

get your spark plugs re-gapped to suit.

good chance your got 1.1mm plugs and the extra air flow is blowing out the spark hence causing your flatspot/missfire/splutter

[Drakey]

Could you describe the problem? is it spluttering, missing, flatspots??

Youre running the factory ecu? and the factory injectors?

my guess would be the injectors maxing out. have you tried running eg 7psi?

in saying that, it could also be a spark/coil issue - what plugs are u running(gap). have you had a GOOD look at the coils?

I would first turn check out the plugs and coils closely.. inspect the plug tips closely( i think white means the cylinders leaning out, brown is rich and black is oil). if that checks out ok, try putting new plugs in eg NGK .7mm coppers HR7(you would want a colder plug perhaps).

if the tips are ok, then i would suspect it to be ur injectors maxing out.

in saying that, it could also be a collapsed cat.. do the easy ones first as ur problem will most likely be something simple.

it has the tiniest flat sport just passed 4K and then smooth as all the way up just no power!

I dont know about what spark plugs are in, ive only owned the car 4 or 5 weeks. I havent tried 7psi.

The thing that gets me is it was running fine at 14psi up until a couple of weeks ago when it all changed and it was a gradual change also.

[race_snooze]

compression test time

[Ultimategtr]

hmmm it was running "fine" before. that doesnt necessarily mean the injectors werent maxing out. There could have been a problem before which maybe wasnt as bad as it is now..

anyway, check your plugs. i bet $2 its your plugs. splash out for some new plugs!

[abu]

Injectors wouldn't max out running 13psi on a R34 turbo

Probably just needs new plugs and a tune

For plugs I recommend BCPR6ES - pregapped to 0.8mm

[Drakey]

ok cool..

thanks for ur quick responses..

ill get some plugs tomorrow and see how we go.

ill keep you all informed with the outcome

[R338OY]

Turn the boost down real low. Like 5psi. If it goes better then you have an idea of the issue. Boost would be fine in this case, it could be 1. Coilpacks 2. Spark plugs 3. Old fuel pump

I'd look into all those anyway. Every one of those issues has made me lose power. The car just gets tired with age and you need to upgrade the fuel and spark components.

Pump- Get a new one, price ranges from $200-$400. Check the DIY threads if you're mechanically minded.

Coilpacks- Get splitfires $5-600 new (SAU trader threads have them) or read the DIY/Maintenance sections and see the coilpack repair section.

Plugs- NGK coppers, 0.8mm, $24 for 6. Do them anyway.

Also make sure your cat isn't collapsed. That can strangle the motor.

G'Luck.

[abu]

Can you put boost down to 5psi because isn't the actuator from an RB20 turbo 10psi and 7psi from an RB25 turbo?

[bubba]

R33 actuator is 5psi.

[abu]

R33 actuator is 5psi.

Are you sure?

I understood that the actuator from an RB25 turbo held 7psi but the standard solenoid was setup to run 5psi below a certain RPM then once it reached that RPM (4,000rpm or whatever it is) it went up to 7psi?

so the soldenoid acts as a restrictor but the actual actuator is 7psi?

Maybe I'm mistaken..

[The Mafia]

Are you sure?

I understood that the actuator from an RB25 turbo held 7psi but the standard solenoid was setup to run 5psi below a certain RPM then once it reached that RPM (4,000rpm or whatever it is) it went up to 7psi?

so the soldenoid acts as a restrictor but the actual actuator is 7psi?

Maybe I'm mistaken..

You can't make the boost go lower than the actuator rating.

The R33 is a 5psi actuator, and there is a factory solenoid that bleeds it so it increases to 7psi at 5,000rpm.

[Drakey]

Hey guys,

Plugs changed.... still no good...

Fuel filter changed... still no good.

Does anyone have a pic of a skyline cat... cause it looks like i have got a 3 inch pipe the whole way and that the cat casig is just welded on the outside so it looks like a cat...

Any other ideas guys?

[Drakey]

Hey guys,<BR><BR>Plugs changed.... still no good...<BR><BR>Fuel filter changed... still no good.<BR><BR>Does anyone have a pic of a skyline cat... cause it looks like i have got a 3 inch pipe the whole way and that the cat casig is just welded on the outside so it looks like a cat...<BR><BR>Any other ideas guys?

[justin911]

enter button works better than html codes i think

[Drakey]

haha sorry...

Hmmm no one??

Ive got it booked in for the tuners on saturday.

Im thinking maybe a sensor or something seeing as my fuel economy is down by like 30% with the other issues aswell?

[Drakey]

haha so i start my car yesterday.

notice my fuel economy is really good!

so i put my boot into it and hey presto i got all my power back! until i hit likr 6250rpm and then it cuts out again.

So yeh i dont know.. lol im stumped. It might be knocking and causing the computer to go back to limp mode?

Maybe bad fuel has caused it DET. Anyone else got ideas?

[stomper]

haha so i start my car yesterday.

notice my fuel economy is really good!

so i put my boot into it and hey presto i got all my power back! until i hit likr 6250rpm and then it cuts out again.

So yeh i dont know.. lol im stumped. It might be knocking and causing the computer to go back to limp mode?

Maybe bad fuel has caused it DET. Anyone else got ideas?

My 33 GTST had a real flatspot at 5000rpm and bad fuel economy 250 - 300km's a tank on.

tried an ECU reset helped a bit, then noticed that she was running super rich.

Turned out that my AFM needed replacing. It was working, but not great, it improved after being cleaned internally but not enough. Then new spark plugs as they were fouled from the rich running. Now operating on stock maps, so next stop Power FC.

Try swapping out with an AFM that is definitely working tip top????