Kristian G Posted April 23, 2015 Report Share Posted April 23, 2015 Im working on an RB25det, 6-cyl, 400whp setup, running a V44. Troubleshooting fuel pressure drop of. - Base fuelpressure is set to 310kpa (45psi) - Multipoint group, semi sequential 2+2+2 injectors. (ie. firing 2 injectors simultaneously at 1 injection events pr 360dg crank revolution) - 1000cc injectors, low ohm saturated drive. - Bosch 044 fuelpump - Aeromotive 1000 an6 FPR - Fuel rail is end fitted, i.e. one port in one out. Fuel setup; - An10 suction line 1ft from collector at bottom of tank to fuelpump - An 8 from pump to pressure filter, an8 to fuel rail. - An 6 line to FPR and an6 return line back to to the fuel cell. As you can see in the picture pressure is dropping severely, down up to -70kpa(10psi) from set pressure. At a slower acceleration sweep of 500rpm/sec the drop of is less, down up to -30kpa (4.5psi) The drop of increases with RPM / fuel flow, and higher acceleration rate. There is also pressure oscillation at high rpm. Have tested the following so far; - Replaced pump - Replaced filter - Moved return line position in tank to different positions bottom/top, furthest possible away from suction - Changed to a larger fuel cell - Replaced FPR - Checked and "length adjusted" vacuum feed to FPR to ensure same pressure to MAP and FPR. - Verified fuelpressure and MAP pressure with manual gauge (matches sensor logs) There may be things ive tried that i forgot to list. Any tips and thoughts are highly appreciated. Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted April 23, 2015 Report Share Posted April 23, 2015 Hi Kristian, does your fuel tank contain a swirl pot and the main feed from the tank to the Bosch 044 is supplied from there. Is your 044 gravity fed, these pumps do not like having to suck, pump should be mounted lower than the tank outlet. Is the pump noisy at all. Fuel pressure dropping under load, high power or heavy acceleration is normally a good indication of lack of flow. The fuel lines and everything seem to be definitely up to the job, but the pump location is critical here . Also it may seem silly, but just double check you do infact have an 044 not an 040 which i have had a few shocked customers with. Also try removing the fuel filler cap and recheck incase the tank is not venting. Also in regards to the pressure oscillation, as you are firing 3 x 2 , you may require a pulsation dampener. Regards Dave. Quote Link to comment Share on other sites More sharing options...
Kristian G Posted April 23, 2015 Author Report Share Posted April 23, 2015 does your fuel tank contain a swirl pot and the main feed from the tank to the Bosch 044 is supplied from there. It has a small pot that the suction is taken at yes. Is your 044 gravity fed, these pumps do not like having to suck, pump should be mounted lower than the tank outlet. Well, it is situated on the same surface/level as the tank, i would say the intake port of the pump is about 2cm/ 1/2" below the suction port of the tank Is the pump noisy at all. Not the one i put in as an replacement, but previous one really sounded like it was cavitating. Fuel pressure dropping under load, high power or heavy acceleration is normally a good indication of lack of flow. The fuel lines and everything seem to be definitely up to the job, but the pump location is critical here. I fully agree with these thoughts. Also it may seem silly, but just double check you do infact have an 044 not an 040 which i have had a few shocked customers with. Also try removing the fuel filler cap and recheck incase the tank is not venting. Yes, very aware of this, and it is the real deal pump. Also in regards to the pressure oscillation, as you are firing 3 x 2 , you may require a pulsation dampener. Currently on its way in the mail.. Kristian Quote Link to comment Share on other sites More sharing options...
JMP Posted April 24, 2015 Report Share Posted April 24, 2015 Is the 044 a genuine pump? One of the quicker way's I've found to check is to ensure the inlet port is helicoiled. Is there any voltage drop at the pump? Quote Link to comment Share on other sites More sharing options...
Kristian G Posted April 24, 2015 Author Report Share Posted April 24, 2015 Is the 044 a genuine pump? One of the quicker way's I've found to check is to ensure the inlet port is helicoiled. Yes, tried 3 different pumps, 1 copy pump, two real bosch pumps, VERIFIED Is there any voltage drop at the pump? Measured under load and no issues found, <0.1volts. Quote Link to comment Share on other sites More sharing options...
Kristian G Posted April 24, 2015 Author Report Share Posted April 24, 2015 PCL & Log file22.04.2015_001.pclLog 22-04-15 10;36;50 pm.zip Quote Link to comment Share on other sites More sharing options...
Steve Posted April 24, 2015 Report Share Posted April 24, 2015 Looks weird Kristian. Could it be that the FPR is not seeing the full manifoldpressure? I meen a slight leak in the vacumline between the plenum and the FPR? Maybe it has a small crack or a slightly loose fit on one of the connections. You got a 0.1v drop on the pump between...? Alternator and pump? Whats the voltage at the pump? Edit: Looking again at the log i can se differential fuelpressure dropping through the whole log where map is climbing. To me this indicates that the FPR isnt seeing true manifold pressure. Where is it hooked up too? Edit again... I now see you checked out my suggestions allready.. Well, i`ll leave this up anyway. Quote Link to comment Share on other sites More sharing options...
Kristian G Posted April 24, 2015 Author Report Share Posted April 24, 2015 The FPR and MAP are connected to the same line (i always do this to ensure that MAP/FPR readings are in "sync". There is about 30cm of line from the manifold. then an Y-split that feeds the FPR with about 30cm line, and 50cm to the MAP (V44 with internal map so a little more lenght that way..) I can try to optimize this even more but i`ve checked and double checked the lines for any possibilities of leaks etc. I will redo the voltage test and report back on that with more details. (Alternator voltage vs fuel pump voltage) Next attempt now is to try with fuelfilter removed (tank-pump-rail straight lines), in-tank foam removed, fuel tank topped up. I will get back with results again after that. As the pressure drop increases with flow rate i can only assume this must be flow related and thus i question; - Fuel line restrictions? - FPR pressure signal? - Fuel rail pressure occillation? (remember 2+2+2 x 1000cc saturated injectors with 1 inj events pr crank rev.) I had ordered an Marren fuel damper to test, but just now got an update that they`re out of stock and it`ll be about 4 weeks before they can deliver. Any suggestion for other optional fuel dampers? or thoughs on that possible beeing the issue? Quote Link to comment Share on other sites More sharing options...
Steve Posted April 24, 2015 Report Share Posted April 24, 2015 I cant say that its NOT the 3x2 thing you got going on, but i find that hard to beleive as i see the differential pressure drop even when car is not boosting yet. Down that low i doubt that the injectors are open long enough to drop pressure. Even if there are two of them. Cant help but think something must be fishy about the FPR hookup.. Old dirty (partially clogged) nipples on the FPR or plenum? Way of topic but i cant help but notice the car is suffering from timingscatter. you can see it on the slightly bumpy RPM line, but it is really obvious when looking at RPM rate. Its the red line that sits just below the RPM line. This is your log Here is a log from my car that has a trigger fitted at the harmonic damper. Logs looking like that should help pushing a few cranktrigger setups on to your customers... Sorry! Back on topic. Quote Link to comment Share on other sites More sharing options...
Kristian G Posted April 24, 2015 Author Report Share Posted April 24, 2015 I cant say that its NOT the 3x2 thing you got going on, but i find that hard to beleive as i see the differential pressure drop even when car is not boosting yet. Down that low i doubt that the injectors are open long enough to drop pressure. Even if there are two of them. Cant help but think something must be fishy about the FPR hookup.. Old dirty (partially clogged) nipples on the FPR or plenum? I do agree, but so far im still at a loss.. Way of topic but i cant help but notice the car is suffering from timingscatter. you can see it on the slightly bumpy RPM line, but it is really obvious when looking at RPM rate. Its the red line that sits just below the RPM line. Yes, im aware of this, the car is running the original Nissan CAS, but with a 24-1 disc, without that i its totally useless.. but yes, its not optimal and a proper trigger solution is prefered but it comes down to the owner to go for that. Right now thats second priority.. Quote Link to comment Share on other sites More sharing options...
Kristian G Posted April 25, 2015 Author Report Share Posted April 25, 2015 Tested fuel flow.. removed the an8 ported 10micron pressure filter, problem solved :roll: Filter was new, and didnt look clogged when i disected it, but it was obvious that it was restricting flow, the filter element was really bulged. And i have no pressure issues after it was removed. Gonna get another filter and see if it works ok then or not. Fuel pressure relative to MAP is not the same at boost as on idle or vaacum. ie the ratio of the regulator is not perfectly 1:1, but that is not a problem as long as the ratio is stable with stable pressure. ie 1:1 at vaacum and 1:0.8 at boost pressure is ok, as long as it is stable. (By that i mean STABLE, also with rapid MAP delta og RPM delta changes)PCL and log files_without filter.zip Quote Link to comment Share on other sites More sharing options...
Dave Kriedeman Posted April 25, 2015 Report Share Posted April 25, 2015 Hi Kristian, well done mate, I knew it was going to be a flow issue. It was too obvious Regards Dave. Quote Link to comment Share on other sites More sharing options...
Steve Posted April 25, 2015 Report Share Posted April 25, 2015 Cool. Good find. This shows (again) that one can not trust a part even tho its new and should not propose a problem on paper. Is this one of the Aeromotive filters? In lieu of this, Anyone that can recomend me a GOOD aftermarket filter? Quote Link to comment Share on other sites More sharing options...
Sutkale Posted April 26, 2015 Report Share Posted April 26, 2015 Cool. Good find. This shows (again) that one can not trust a part even tho its new and should not propose a problem on paper. Is this one of the Aeromotive filters? In lieu of this, Anyone that can recomend me a GOOD aftermarket filter? Well, I've been using Bosch 4 micron paper inline filter for years without issues, and only on E85. Quote Link to comment Share on other sites More sharing options...
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