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Mapping & Fuel Pressure issue

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  • Mapping & Fuel Pressure issue

    The last two times my 7 went to dyno we noticed that @ higher RPMs (6000-7000) the fuel pressure dropped from 3 bars to about 24 psi. More fuel was added to overcome the lower pressure @ higher RPMs. However, I view that as a bandaid solution and would prefer to have consistent FP. Caterham USA tells me that all of the cars come with the same pump, even the R500s, so it should work just fine. Has anyone encountered a similar problem while mapping their ECU? Can anyone offer a suggestion or two about fixing the situation/problem?

    Thank you very much, in advance, for any creative possibilities. 8)

  • #2
    I would suggest talking to people that know what they are doing. The guys in Colorado don't even know when to run high impedance injectors instead of low.

    I understand from SBD, Raceline, and Caterham UK there are two pumps. I looked in Caterham's parts catalog and these numbers appear:



    I do not know what the difference is but was told the r500 pump is higher volume and pressure.

    Of course if you change pumps you will have to map over completely. If you run a little lower pressure to start with the drop will be less. I would suggest 36 to 40 as opposed to 44 psi. Still you will need to map again. Of course if you want to see real pressure drops take a look at what the guys in Colorado are using with their injectors. They start with 60 psi (70 -85% of the pumps effective pressure), which starts dropping almost as soon as you start using it, and then it drops to less than 25 psi due to being oversized and over pressurized. The maps were so rich I have seen mine drop to almost zero. These are a complete mess as is the maps. But as they tell me they have 50 out there and no complaints. I guess I do not count. For real help I suggest you go to someone not connected to the guys in Colorado. See Public Service Announcement for Caterham Owners in this section.


    • #3
      There was a thread running on blatchat r.e. this issue recently.

      specifically about the fuel pump for a Duratec install but I think the Zetec could use the same.
      A day you don't go a hundred is a day wasted


      • #4
        Don't know if it helps Brad, but I can report that I've never knowingly experienced low fuel pressure in my R500. I don't have a pressure guage, but the engine is always eager for 9K. So maybe the pump isn't the problem.


        • #5
          Roll a 7
          On the Duratec cars I have built I've always used the R500 pump which works on the 250bhp cars with no problems.
          Early R500's had different pumps to the standard cars but I believe the later R500's use the standard pump.


          • #6
            Rich & Mick: Thank you very much for taking the time to reply. The car gets terrible mileage (12-15 at best), but is still fun to drive. The exhaust pipe looks black with carbon. Perhaps the existing pump will work since it seems to be delivering more than enough fuel. I'm going to check the lines for crimps/kinks, get a new lambda, new fuel filter and try a different FPR. More time on the dyno seems to be in my future. :x


            • #7
              Brad, not that I am an expert in any way. But here some opinion (forgive me if that is all common sense or bollocks):

              - If you don't have stable and reliable fuel pressure you can go and have your car dyno-mapped until the cows come home. From your first post I read that the pressure collapses to almost 50%. That would normally lead to an extremely lean mixture if not already compensated for in an earlier mapping session. I would not trust a dyno operator who keeps mapping after seeing the pressure change that much (assuming you meant the pressure at the injectors)
              - I know you complained about lousy mileage already when we met first in May 2003. But I can not see any reason why your engine should be worse than other Zetecs I have seen. Even my ancient Weber carbs get me to 25 mpg on the highway, 20 in the city and maybe 12 on the track. However, I was told that a black exhaust is normal for unleaded fuel. How do the plugs look?
              - If you want to see what the fuel pressure is doing in more detail you could temporarily hook up remote pressure sensor before and behind the regulator and watch what happens while driving. If it is not stable at full throttle it might be the pump but you might also have a problem with the pressure regulator and return system. If you need a remote pressure sensor I can borrow you one.
              - Once you got stable pressure I highly recommend a wideband lambda meter (the Innovate device I have is inexpensive and good). You can save a lot of dyno work just by driving around, logging AFR vs. throttle position and engine revs.
              - Alternatively: Take your car up to Woody's shop and have them fix it. On the way back stop at Infineon for a track day :P



              • #8

                I had similar mileage issues, with my “202â€‌ Hp Zetec, 12 MPG. The exhaust was pitch-black and the car exhaust reeked of unburned gasoline. I never let the car idle in the garage, the resulting cloud was way too toxic. I tried lots of stuff, but the only thing that worked was Woody’s guys.

                They changed a lot of stuff to make the engine run right. They changed the spark plugs, to ones they prefer. They changed the injectors to smaller ones so that the car could idle. The stock ones were too large and could not be accurately adjusted at the lower flow rate. Also the stock ones were low impedance, 2 ohms, and the Pectel ECU was made for high impedance injectors only. The TWM intake manifold was also not set up properly. They adjusted that. We discovered the catalytic converter in the muffler and they removed that and changed the car to side exhaust, saving about ten pounds of weight. They remapped the ECU and now the car runs like a dream.

                Before they tuned it, the engine would vibrate and make a lot of noise, so in town I tended to shift around 3.5K to 4K. Now it is smooth up to 7K and now I have to watch the tachometer so that I do not over rev the engine. Before, when I was cruising down the freeway, the engine vibration made if feel like I had my feet in a bee hive. Now it is smooth, and the modified sounds sweet.

                We did not see any issue with the fuel pressure while tuning, but based on my experience with MSI---Woody Inc, they will be able to tell you what the problem is. Also, while I have not accurately measured the mileage since I got the car back, it appears to have about doubled.
                Rod Swanson


                • #9
                  Rod: Your first two sentences are an excellent description of my car!

                  Idle is very smooth. I have high impedance injectors and 45mm Jenvey TBs, which I believe are much easier to deal with @ low RPMs because the air moves faster through the smaller orifice. TWM systems seem to be much more difficult to program @ low RPM levels.

                  I have no idea how good or bad all the internal settings in my Pectel unit may be. That part of the black box is pretty much a mystery----I just don't know what the correct settings should be.

                  I'm also thinking about changing to a side exhaust and dumping my catalytic converter.


                  • #10

                    I've gotten a quote for $600 for a good, custom made side exhaust made locally here in Costa Mesa. I'm thinking about it.

                    When they saw the stock header/catalytic converter setup I have, they shook their head in a sad little way and said that they weren't att all surprised over my reoccuring cracks.

                    /Magnus F.


                    • #11
                      Magnus: Welcome back, if you are on this side of the planet again!! Mine has no cracks, except possibly my head, but I do have some thoughts and passibly constructive suggestions for you. I'll return your call tomorrow. Brad


                      • #12
                        side exit

                        I do not have a place to post photos, but if you send me your email adress I will send you the photos of my modified muffler with the catalytic converter removed and the side exit.

                        [email protected]
                        Rod Swanson


                        • #13

                          I would suggest talking to people that know what they are doing. The guys in Colorado don't even know when to run high impedance injectors instead of low.
                          Delayed again, why now? V


                          • #14
                            Sock256,I disagree, I found Cody to be very knowledgeable and helpful. He helped quite allot, getting me parts after I stuffed my seven under a guardrail.

                            Other folks who have helped as well are, (in no particular order):

                            1) The aftermarket guys at Caterham, England to be very helpful in recommending car suspension and braking improvements.

                            2) Rich Kemp of Golden Gate sevens to be very knowledgeable and helpful. I highly recommend his work.

                            3) Woody at MSI has done a lot of work for me, and he not afraid to try something new.

                            4) The biggest single resource I have found is other Seven owners.
                            Rod Swanson


                            • #15
                              Is Sock256 only posting some irrelevant junk to push the gambling link?