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Discussion Starter · #1 ·
I recently purchased a 2005 SRT4 has a .70ar ebay turbo, 3" turbo back exhaust, big fmic, emusa wastegate @ 6lbs, stage 1 injectors, 255lph pump, aem wideband.
When got the car it ran good afr stayed around 10.5-11 wot running about 15psi. When pulling it it started going lean, sputtering out, until you got the throttle up to above 1800rpms. I bought a Diablo i3 to try a stock tune and the i3 lost the tune and car wouldn't start. Had to send the tuner and ecu to diablo and they said they loaded a stock srt4 tune to the ecu but now its running 10.0 afr at idle and it barely idles. The car was doing just fine before I hooked the i3 up to it now I can't can't drive it. Tried changing plugs and wires to no avail.
Anyone have any ideas? I'm thinking O2 sensor, when I monitor on the diablo the voltage jumps up about 1500mv and back down. Any help would be greatly appreciated
 

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Check for 3BAR sensors first, but I'm not familiar with that wastegate. It's possible your custom tune modified the wg duty cycle as well (though that spring is pretty close so probably not). 02 voltage is maybe related to your rich condition. I really thinking your looking at another CMR tune.
 

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Discussion Starter · #5 ·
Stock map and tip sensor. It started kicking a code for being lean and check engine light was flashing along with the chime sound. No pressure at the fuel rail so I ordered a new pump but I remembered how everyone suggests the rewire for the fuel pump so when i checked the voltage it was only showing 2.1 volts so I went ahead and did the rewire with some 10ga and 30a relay and put the walbro 255 back in it and get fired right up seemed to Auto pretty smooth or like it did before little lopy but guy claims the car has cams I just haven't checked put a gauge on the fuel rail and it was showing right under 60 lb I drove it down the road and it done good and then after about 30 minutes it started to running rich again and missing real bad and undriveable again
 

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Have you taken another log since upgrading the fuel pump wiring? That might show what difference a pump running at ~60 psi makes. Also, does the Diablo read the AFR from the AEM wideband or is it still reading the stock narrowband sensor?
 

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Have you taken another log since upgrading the fuel pump wiring? That might show what difference a pump running at ~60 psi makes. Also, does the Diablo read the AFR from the AEM wideband or is it still reading the stock narrowband sensor?
I believe you have to have a DiabloSport Trinity and use the Holley Expandable Accessory System in order to log wideband inputs these days (that's how I'm doing it at least). Though, AEM can log on its own I believe.
 

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Discussion Starter · #9 ·
ill get a new log in a few. this is the last log i made. I put a new fuel pump in and now Im only making 30psi. im sure i missed something simple its just pouring the rain so i havent had a chance to go over my work. quick question though, on my fuel pump rewire i used the green/white from the original plug to turn on the new relay but was there anything i needed to do for old wiring? When i turn the key to the on position without cranking the engine the fuel pressure gets up to 30ish then you hear the relay under the hood kick and the fuel pressure goes back to 0psi. I know the pump only gets power for a brief moment when you turn the key over but i thought it was suppose to hold the pressure or slowly leak off.
730newest.log
 

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Using the green/white wire to power the relay is the way I did mine also.
The other side of the relay coil was just grounded as shown in the diagram.
The old green/white wiring is fine for the relay.
The original 18 gauge is now only handling 175 ma of current in the relay rather than 10-12 amps for a fuel pump.

Key ON, engine off primes the fuel pump for about 2 seconds. This is normal.
Stock fuel pressure should be 58 psi.
The stock pressure regulator is on top of the fuel pump carrier. This regulator is also a fuel filter.
You mention the fuel pressure is only 30 psi and bleeds down rapidly. It should hold near max pressure for a while and bleed down slowly.

If you have a fuel pressure gauge (sounds like you do), then this car is likely set up with an aftermarket fuel pressure regulator and a fuel return line.
The stock pressure regulator would have had a block off installed to keep the stock regulator from controlling pressure.
In any event, the pump should be running at 58 psi pressure and the aftermarket regulator set at that level.

Because the original stock pressure regulator was also a fuel filter, perhaps it is time for a new one.
Darrell Cox Racing has a replacement filter that has block off already installed that seals off factory bypass.

I'll have a look at the latest log when I have more time.
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Based on the latest datalog, it looks like a larger-than-stock cam in this engine.
The idle vacuum is quite poor compared to stock and the boost comes on a bit later than the 3200 rpm for a stock engine.
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Looking at the spark advance and knock retard plots, there is knock occurring at peak boost (20 psi) and elsewhere.
The data log does not have the wideband AFR readings, but I wouldn't be surprised if it was leaning out at max boost.
The injector duty cycle is hitting almost 84% at peak boost, so there is no room left to increase boost from 20 psi and have adequate fueling.
Also, at these boost levels, RPM is limited to about 4700 rpm.
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Discussion Starter · #12 ·
its stock fuel system with the exception of the 255lph. Long story short i ended up swapping in a old fuel pump from a 1st gen I have and now im holding 58psi. I guess the new pump i installed today was bad from the get go cause it wasnt building any pressure at all. When i bought the car the guy said it had a custom tune and bigger cams but i thought he was just full of crap. Boost is controlled by pcm so im gonna throw a mbc on and bring it down to 15 or so til i get it figured out. Now that i got my fuel pressure back to where it was im back to my original problem, pig rich at idle. The wideband is at 10 and you can smell the gas really bad. Here is a log i pulled on the way home after i swapped the pump out.
25013_01.log

25013_00.log

Ill try to get a better log tomorrow. I was tired of going around with diablo over my I3 and bought another one thats locked and I wasnt sure what it would log and I didnt have my laptop with me so idk if the wideband will show on the logs or not.
 

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The first two charts are Time vs [ RPM, MAP, TPS, PW, SPARK ADVANCE and MAPxRPM (airflow)]
The third chart is a recommendation.

On the 1st two charts, we have highly volatile (choppy) segments and a smoother segment in the middle.

CHART #1:
Lower right hand corner is showing averages of the segment between the big horizontal arrow.
RPM: 800 rpm plus or minus 200 rpm
MAP: 70kPa plus or minus 10kPa
TPS: flat, no change
SPARK ADVANCE: 11.5 degrees plus or minus 11.5 degrees (goes from 0 deg to 24 deg)
Rectangle Slope Font Screenshot Line

CHART #2:
Lower right hand corner is showing averages of the segment between the big horizontal arrow.
RPM: 1600 rpm plus or minus 70 rpm
MAP: 39kPa plus or minus 2.5kPa (the cam is in a sweet spot and making good vacuum)
TPS: higher than chart #1 but also flat, no change
SPARK ADVANCE: 40 degrees plus or minus 1.5 degrees
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I do not know why the spark advance is so choppy at the 800 rpm range, but that isn't helping the idle.

CHART #3:
A summary of those areas with high volatility and low volatility over the time period of the log.
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Recommendations:
While we try to figure out if there is a way to change spark curve under 1000 rpm, let's try
setting target idle RPM at 1000 rpm. Log the results and make notes on wideband AFR and on idle smoothness.
I can't see wideband AFR, so your notes are needed.
Move the target idle up using 25 rpm increments and log each result and make notes, until you think it's stabilized.
Don't go higher than 1100 rpm.

This should find an idle sweet spot that you can live with while figuring out how to change spark and maybe VE (volumetric efficiency) table in the idle range.
By the way, if there is a PID that has the letters VE in it, log that one also.
 
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