News

328 on the Dyno

Discussion in 'Technical Q&A' started by MManzonelli, Nov 4, 2003.

  1. MManzonelli

    MManzonelli Karting

    Nov 4, 2003
    73
    Columbia, IL
    Full Name:
    Mark Manzonelli
    First of all I want to thank everyone who responded to my question on how much rear wheel HP I should see on my 328. Of those that responded, I see the number should be somewhere between 210 and 220. This makes sense assuming a 17% loss through the drive train. 260 HP x .83 = 215.8.

    Here is the problem. I had my car on the dyno and it was a disappointment. I had 194.7 HP and 166.1 FT-Lbs. of torque.

    Here is what the charts are telling me. First of all, my peak HP is at 6700 RPM. This is not right. This should be somewhere closer to 7800 RPM. What I also see is that my Air/Fuel Ratio all throughout the 3500-8000 RPM is always between 14.4 to 14.8.. What this tells me is that the car never leaves closed loop.

    So I did some digging. As we know this is a BOSCH CIS-E Fuel Injection System. I found that the two microswitches at the throttle body were not working properly. The way they work are as follows. One microswitch closes when the car is at idle. This makes the car idle steady and be extra clean for emissions. The other microswitch closes at approximately 10 degrees before full throttle. This allows the car to go to open loop and enriches the fuel mixture. In between the two "points" (Both switches open) the fuel system is in closed loop mode and the air fuel ratio should be 14.8.

    What I found is that neither switch was activating and therefore 1) my idle was always fluctuating (hunting) and 2) I was never getting enough fuel at full throttle to get HP.

    I adjusted the position of the microswitch assembly and came up with the following:
    1) My car idles nice and steady....No more surging...So NO they DON'T "ALL DO THAT"
    2) If the second microswitch made any changes I can't feel it. I wired a switch direct to it and activated it manually while driving down the highway. I did not feel anything. Now if I am at idle and I open the idle switch and then close the "open loop" switch, there is a change. Not drastic but there is a change. Is this correct? Can anyone shed some light on this? I read that the "open loop" switch may only be active after a certain RPM. The computer dictates this? Can anyone verify this? Anyone real familiar with the BOSCH CIS-E?

    I want to get this car back on the dyno but before I do, I want to do some more checking. I plan on changing the fuel filter, checking / replacing the plugs and checking / replacing all the vacuum hoses. Any other ideas?

    I believe I am getting closer to finding my Horsepower. If anyone can shed some light on what to look for, I am all ears.

    Mark Manzonelli
     
  2. davequick

    davequick Formula Junior

    May 27, 2003
    307
    Bellevue, WA
    Full Name:
    Dave Quick
  3. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
    1,572
    Kalamazoo, MI
    Full Name:
    Rob Schermerhorn
    Mark,

    If you don't have it already, I highly recommend Charles Probst's book Bosch Fuel Injection & Engine Management. You can find further information in my article in Parts and Service section of FC: Technical Reference Books.

    Your car is KE Jetronic with Lambda.

    Best regards,

    Rob Schermerhorn

    Ps, thanks for dyno testing, great data.
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,479
    Texas
    Full Name:
    Steve Magnusson
    I thought US 328s were K-Jetronic with Lambda -- can someone confirm/deny?

    If so, you could try measuring:

    1. the voltage output of the O2 (Lambda) sensor -- if it's really going open-loop AND adding extra enrichment with the WOT switch closed, the O2 sensor output should go to ~+1.0V and stay there (although it's important that your open-loop tweak is not set-up to the lean side). If the Dyno-shop has extra data logging capability, ask them to monitor the O2 sensor output during the run (should give you another reference for when things are closed-loop vs open-loop).

    or

    2. the duty cycle of the signal going to the frequency valve -- which should also change behavior if the ECU is going open-loop and trying to add enrichment with the WOT switch closed.

    I don't recall any WOT switch effect/RPM dependence mentioned in the TR KE-Jetronic with Lambda literature (but that doesn't mean a 328 couldn't be different). I'd second Rob's recommendation for the Probst book, and add that the Aird book is a little simplier and might be a good pre-read.
     

Share This Page