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Thread: Cold idle RPM gems V8

  1. #21
    Join Date
    Aug 2018
    Location
    Brisbane
    Posts
    34

    Cold idle RPM gems V8

    That dont state the LSA but if it has a decent amount of overlap most EFI systems donít know how to cope

    Essentially overlap is when the exhaust and intake valve overlap and both are open

  2. #22
    Join Date
    Jan 2016
    Location
    Netherlands
    Posts
    256
    A final update (I think :P)

    If I understand http://www.pipercams.co.uk/Technical-Advice/ this link correctly I need to add 44+44 and I get 88 degrees of overlap? Don't know if that makes sense...

    In any case, I have been using the car for another week and the idle is slowly creeping up into useable territory. I tried an old honda trick, which I'm fairly certain does not work the same on our P38's but it has had some positive result so I'll share it here: I disconnected the battery for about 10 minutes (when cold) and then turned on the ignition, manually filled the air tank to the brim (making use of an external power supply) made sure the brake booster did it's thing, turned off the AC and any other electrical users and then started the engine. I let it run for 10 minutes or so without doing anything and with no (or the smallest amount possible) electrical users or aircon.

    The end result is that the car can idle fairly normally when cold, the only bothersome behaviour that remains is the creeping forward idle. When I lift my foot of the brake the car starts creeping forward and when it reaches it designated idle speed the idle drops to around 200 rpm. The engine no longer stalls but it idles along very very slowly. The ECU does recover from this point within a few seconds, the car picks up speed again and bang the idle drops down to around 200.

    Like I said; I can live with this but I hope it will over time correct even further. Changing the cam is not my first choice but it does indeed seem that the gains I got from this setup have a few downsides as well, the most bothersome beeing the MOT beeing barely met.

    Cheers!
    -P

  3. #23
    Join Date
    Aug 2018
    Location
    Brisbane
    Posts
    34
    The problem I believe is that the ecu canít adapt to the cam, previously it was ok because it had some adaptive values already from the OE cam

    OE cams have an LSA if 112 for a smooth idle with 110 on the newer engine management systems with drive by wire. 108 LSA is what I would call a cammed engine with a good throb and rough idle

  4. #24
    Join Date
    Jan 2016
    Location
    Netherlands
    Posts
    256
    David, would changing out the EFI to a megasquirt or eq. which can be completely tuned by hand make any difference? It's been on my wishlist for some time so maybe the time has come to deal with that

    I did find the CAM on the piper website, it has different value's but it at least seems to contain an LSA figure:

    Camshafts Car

    if I read that correctly the LSA is 110. should still kinda work, right?

    Thanks!
    -P

  5. #25
    Join Date
    Aug 2018
    Location
    Brisbane
    Posts
    34
    110 LSA is very very mild, should idle close to stock with a very very slight lope

    I'm actually thinking of looking into a megasquirt, mainly to get around the ****ty GEM coils and sensors and use modern LS coils and modern sensors, either that or a really really cheap entry level haltec in wasted spark (only need the 4cyl model as I don't care for individual injection, just fire all the banks like stock)

    I think on the Gems if you go with LS coils, LS maf, NTK O2 sensors stock water, generic air temp and bosch injectors you would get much better everything and in my case remove the last obstacle from believing I can take this thing anywhere! already have coils, all i need now is to remove the GEMS and swap sensors over

  6. #26
    Join Date
    Feb 2010
    Location
    Townsville, QLD
    Posts
    2,522
    Why not just put an LS motor in?

    Green 2000 P38 Range Rover HSE - Gone
    Blue 1999 P38 Range Rover HSE - Gone

    Silver 2002 P38 Range Rover HSE - Sequential LPG, BCDC Charger, TPMS, Rear Locker, Wheel Carrier, Bullbar & Spotlights, General Grabber AT2's, Too Much to Mention!

  7. #27
    Join Date
    Jan 2016
    Location
    Netherlands
    Posts
    256
    In my case: an LS is not common down here and I could get a new crate engine but I "just" (30k ago) put in this completely rebuild engine which already cost me a bloody fortune I would like to get rid of the GEMS ECU but I know the BECM is a bit of a difficult thing to deal with. I'm not sure just ripping out the GEMS ECU will play nicely.

    Then again, getting rid of that bloody BECM is even better. I can probably replace all the functionality of that thing with an arduino or similar. It's just a CPU with a bunch of inputs and outputs. That would also go a long way in waterproofing the beast. The only major concern is that I was not planning on replacing the stock ABS/TCS and EAS cpu's. Not sure how they will react or even work without the BECM. Though EAS could be considered for redevelopment into an arduino or whatever, I'd rather not touch the ABS. Though, removing that all together could be an option...

    I'll make a vid of my engine idling when I get the chance so you guys can tell me what's what maybe

    Cheers,
    -P

  8. #28
    Join Date
    Feb 2010
    Location
    Townsville, QLD
    Posts
    2,522
    Sounds pretty complicated haha! My comment above was to David, my apologies mate!

    Green 2000 P38 Range Rover HSE - Gone
    Blue 1999 P38 Range Rover HSE - Gone

    Silver 2002 P38 Range Rover HSE - Sequential LPG, BCDC Charger, TPMS, Rear Locker, Wheel Carrier, Bullbar & Spotlights, General Grabber AT2's, Too Much to Mention!

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