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changing harness

Discussion in 'FAST Support Forum' started by jaros44sr, Nov 12, 2012.

  1. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    first off, let me tell you about myself.....
    Restoring a 1972 GMC Jimmy 4X4. 350 with vortec heads and 1985 Corvette TPI! TH350 Trans. at the moment. Finished most of the rust, now starting mechanicals. FAST XFI 2.0
    PCM, two guestions on the harness
    1. There is a ground lug right where the grommet comes through the firewall, my understanding from the directions is that ALL grounds must go to battery. Why would fast put a grounding lug that far away from its intended source, and why would they put a bolt lug on that wire if it wasnt intended to ground to the firewall at that spot

    2. My wide band O2 senser has an extension of about 3 feet, both ends plug into a designated connecter. One to the harness and one to the O2 senser. Can i get rid of the cableextension, and just wire the O2 directly in the harness

    Ireally like where my hasness is running, but it is running to close to the coil...is there any shielding that can be done to protect from interferance

    Can the ECM be mounted on the radiator core support, in side engine compartment

    I will post pics after i get 10 posts
     
    Last edited by a moderator: Nov 12, 2012
  2. TurboNova

    TurboNova Active Member

    Joined:
    Jan 30, 2009
    Location:
    Lake Havasu City AZ.. but mostly travel tuning
    1. That loop is the shield drain and should be connected to the block.
    2.you can buy the female connector for the fast harness to go directly to the O2 sensor and remove the old one then install the connector but it is kinda a bitch to do. I would shorten your extension instead.

    There is no real shield from the coil. keep the coil, coil wiring, spark plugs, distributor, msd boxes ect all away from the efi stuff.

    You can mount tje ecu where ever you wish but remember it isnt made to get wet.
     
  3. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    quick reply ty

    as you can tell i am new to the ecm stuff, 50 years around mechanical things and i have never had to deal with electrical noise.....
    Is there anything i can wrap my harness in to eliminate noise

    Just started efi a few days ago, had my harness layed out to go down the middle of my truck. Then, i decided, i had better read the directions! Found this forum, and have read all the way back to page 20, i have a way to go.

    Having a sbc, it seems that every thing should come in from the front of engine, but then my fuel injecter harness would be backwards, suppose i could rewire this....
    If i do mount it to the core support, would a waterproof enclosure for the ecm be acceptable, or should i buy the marine ecu.

    Does anyone have advise, or pics, of where they layed there harness out ina sbc?

    I usually hang out at the 67-72 chevy truck forum, but no one over there has ever done a fast xfi, so maybe i can bring this info. back to my build

    Turbonova, do classes ever come to the philadelphia area?

    Thanks for looking

    1. Can i splice the shield drain to lengthen it?
     
    Last edited by a moderator: Nov 13, 2012
  4. TurboNova

    TurboNova Active Member

    Joined:
    Jan 30, 2009
    Location:
    Lake Havasu City AZ.. but mostly travel tuning
    If routed properly there is no real need to shield it anymore than you have now.
    The gm tbi harness that it comes with is meant to have the ecu inside of the car with the grommet drilled just to the inside of the valve cover between it and the distributor. Most of your wires can run down the valve cover towards the front.

    On the inside you have room to mount the ecu between the firewall and mid passenger door somewhere. The battery wires are long enough to reach the trunk area if your battery is there or can go back out the front to a battert there.

    The injector harness plug should be coming out of the loom behind the intake in front of the distrbutor.

    This is the normal install but it can be done anyway you wish.
     
  5. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    good advice

    But, that is the way i was going to mount it. Then i started reading about problems with running wires to close to the distr. and coil. If i understand you correctly, you are telling me to run my harness directly in those areas

    Could you explain speed density, and what is needed. I was told, when i bought the fast xfi 2.0, that i could run this....

    Thank you for your time
     
    Last edited by a moderator: Nov 13, 2012
  6. kevin87turbot

    kevin87turbot Member

    Joined:
    Jul 27, 2012
    Location:
    Ripley, MS
    As long as you don't route harness wires too close to the distributor or coil, you'll likely be just fine.

    Here's some reading for you concerning Speed Density Mode vs Load Indexed Speed Density vs Alpha-A modes. I may have changed the wording on the Alpha-N mode just a bit... :)

    There are three modes of operation that your XFI can use to calculate the fuel requirements of your engine. They are: Speed Density mode, Load Indexed Speed Density mode, and Alpha-N mode. In most applications, Load Indexed Speed Density mode will provide the best overall performance for the least amount of tuning effort from inexperienced tuners. Load Indexed Speed/Density mode is something unique to your FAST XFI. In this mode, a “load” variable is formed from the ratio of manifold pressure to barometric pressure. This “load” variable is used to index into the VE, Target Air Fuel, and Base Spark tables. Barometric pressure is sampled from the MAP sensor prior to start up. Its advantages are for users that may drive in areas of vastly differing altitudes. For example, full engine load at sea level is approximately 101 kPa, but full engine load at 3000 feet above sea level is significantly less in kPa. This means that in regular Speed/Density mode the point of full engine load in the VE table is in a different spot for each of the two altitudes. Load Indexed Speed/Density takes that difference out of the equation and makes the point of full load the same no matter what the altitude, ultimately making the tuning process easier. Neither mode will produce more power than the other, but either Speed/Density mode will allow for much better drivability tuning than Alpha-N.

    Any turbocharged or supercharged engine MUST use one of the Speed/Density modes. The boost level in a forced induction engine is a critical part of the fuel calculation.

    You should use Alpha-N mode if you have an individual runner intake manifold such as a Kinsler, Hilborn, or Crower. However, it is possible to use speed/density mode with some modifications to the manifold. A small manifold with a vacuum connection to each runner can be created and used to provide a manifold pressure signal to the ECU.

    Alpha-N mode is Dumb. It's occasionally used on naturally aspirated racing engines with very long-duration camshafts that produce little or no engine vacuum at an idle. It is sometimes difficult to achieve decent drivability or idle quality with an engine of this type using Speed/Density mode because the amount of pressure in the intake manifold is almost the same at an idle as it is at wide open throttle. If your engine will not have more than 10in. of vacuum at idle then choose Alpha-N mode.

    Simply click on the radio button for the mode you wish to use.
     
  7. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    Am radio

    Also, where would a map senser usually be mounted. Thank you for explaining speed density

    Will check on the vacuum
     
    Last edited by a moderator: Nov 13, 2012
  8. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    map

    do i need map sensor with speed density....i bought a used1985 corvette tpi and the map wasnt included
     
    Last edited by a moderator: Nov 14, 2012
  9. kevin87turbot

    kevin87turbot Member

    Joined:
    Jul 27, 2012
    Location:
    Ripley, MS
    You will need a 1 Bar GM MAP sensor for a NA engine like yours. The FAST part number is 307007. You can mount it to your firewall or inner fendor or even make a bracket and install it on your intake. It just needs to have a vacuum line connected to manifold vacuum.

    You'll also need to have a coolant temp sensor, air temp sensor and the NTK O2 sensor connected.
     
  10. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    Ok, thank you! Been doing a lot of reading, chevy tpi fi swappers guide by john baechtel, explains alot about systems.

    Just talked to guy, found the sensor for 67.00, seems like 85 didnt have a map sensor, so i will have to modify...

    Can i use a plenum port, or do i have to go to base plate port, seems 90 model year is differant from 85 model year

    I cant express how much i thank you guys for taking the time to explain things to me

    What does NA stand for.....
     
  11. kevin87turbot

    kevin87turbot Member

    Joined:
    Jul 27, 2012
    Location:
    Ripley, MS
    A plenum port will give the MAP sensor the signal it needs.
    NA stands for Naturally Aspirated. That just means no turbo/supercharger/nitrous.
    Thanks.
    Kevin
     
  12. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    Confused?

    Thank you for that info.

    Dont understand, but my tuner told me what parts to buy for my fi system...msd distributor 8366

    In all my reading, seems like the common advise is to run an ignition box. Soooo.....called msd tech line and asked if i can hook up an ignition box to my distri. The answer came as yes and no! What? Yes, ican hook up the box to control spark, but no, i cannot control timing. Am i sol, or does my tuner know more than this forum, and isnt giving away his secrets
     
  13. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    Will the fast xfi 2.0 feed fuel to the cylinder that is being fired, or is it just bank to bank?
     
  14. Denis

    Denis Member

    Joined:
    Dec 2, 2009
    Location:
    Mendocino County, Northern Calif
    The msd distributor that you got is a direct replacement for the GM distributor that is used with the TPI. If you use this distributor you must do bank to bank injection rather than sequential that fires the injector timed to the opening of the intake valve for each cyllinder. This msd distributor is designed to provide the inputs to the GM ECU, and not a system like FAST. As I recall, I originally modified my GM TPI distributor to work with fast but was stuck in bank to bank injection since there was no cam sync available and it was a pain to figure out how to connect it to the XFI ECU.

    If possible I would consider returning the msd distributor and get a FAST Dual Sync distributor. I ran TPI with the FAST system and was definitely much happier with the sequential system in terms of drivability. Now I am using the Dual Sync distributor for cam sync and a crank trigger.

    The dual sync distributor plugs into the FAST XFI harness so it makes for an easy installation. You should probably consider a MSD 6AL ignition box for what you are doing and the white points lead from the ECU will interface directly to the ignition box points input. With this setup the ECU will control engine timing and you will have sequential injection.

    The 12 volt power and gorund to the ignition box need to go directly to the battery as does the 12 volts and ground to the ECU. If you do not do this you will have electrical noise that will mess things up.
     
    Last edited by a moderator: Nov 17, 2012
  15. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    good advice

    denis thank you for taking the time...

    Just dont understand why he would tell me to buy that distri. from him. Alright, ill put that behind me and buy the dual sync

    Where would the crank trigger mount, so i can start planning for that
     
  16. Denis

    Denis Member

    Joined:
    Dec 2, 2009
    Location:
    Mendocino County, Northern Calif
    The FAST Dual Sync distributor has both crank sync and cam sync, so you do not need a crank trigger. Just plug in and go. You may have to move the sensor in the dual sync dist for a 50 deegree refrence angle, but that is no big deal as they give you instructions on how to do it. Just remove two screws and move the sensor.

    My engine is making close to 500 hp so I went to a crank trigger because it is more accurate with regard to ignition timing. Attached are three photos of the crank trigger I am using. The reluctor wheel that goes on the crankshaft is only 1/16 inch thick so when it is installed between the crank pulley and the balancer the pulley allignment is usually ok. It is made by FAST for a SBC. I am using a hall effect device and a custom mounting because the accessory brackets on the fornt of my engine did not leave room for the fast setup. My sensor attaches to the two bolt holes next to the crank pulley on top of the accessory bracket on the driver's side of the engine.

    I have also enclosed a photo of the MSD 6AL wiring. Separate the wires going to the coil and twist them as shown and put heat shirink on them. Do the same with the points wire and the switched 12 V. Also, the 12 V and ground wires from the battery should be twisted and heat shrinked. By twisting the wires you minimize inductive interference from the ignition. Twisting the wires is not absolutly necessary but it is better to do it as a preventative measure when you are building the system rather than after the fact if you have a noise problem.

    The Dual Sync distributor needs switched 12 V from the Ignition circuit. I put switched 12 V on the 12V switched pass through wire in the harness. I filtered the wire with a 28,000 micro farid capacitor but that was probably over kill. I used the switched line for the distributor and my hall effect speed sensors. I put the 12 V going to the distributor on one of the pins in the distributor connector and removed the inductive pickup wire so that all of the wires going to the distributor were all in one connector.
     

    Attached Files:

    Last edited by a moderator: Nov 18, 2012
  17. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    Thanks denis for all the info. Ill start by getting the dual sync, and go from there.

    Ill talk to my tuner on monday and see what he was thinking
     
  18. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    tuner says

    ok talked to the tuner and he says the msd distri.8366 will work up to 2000 hp using adapter cable fastp/n301302 plugged into the cam hall

    Anyone?
     
  19. jaros44sr

    jaros44sr Member

    Joined:
    Nov 12, 2012
    Location:
    phila., pa.
    to close

    is this mount to close to my ignition switch? Final mount will be about 6" lower
    Ignition harness goes to the left
    [​IMG]
    20121119_102001 by jarosaj, on Flickr
     
    Last edited by a moderator: Nov 19, 2012
  20. Denis

    Denis Member

    Joined:
    Dec 2, 2009
    Location:
    Mendocino County, Northern Calif
    That mounting arrangement is ok. I have my ecu in the same basic location except under the dash. The proximity to the ignition switch or any of the wiring under the dash is not a problem. You would only have a problem if you decided to put your ignition box under the dash and run the wires out with the harness from the xfi ecu.

    I personally would have put the box against the fire wall behind where you have it as the cables would dress better and look nicer.

    With regard to the distributor, yes it will work. You are only going to have bank to bank fuel injection not sequential with this setup. You might as well use the stock gm distributor as that is basically what you are getting. Ask your tuner where he is going to get cam sync as that is what is required to go sequential. The msd distributor only has crank sync not cam sync. The FAST dual sync distributor has both and thats why it is used.
     
    Last edited by a moderator: Nov 19, 2012

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