Cam Design (Or lack thereof) for the MZR DISI

Discussion in 'MZR Knowledgebase' started by Realgib3, Oct 19, 2016.

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  1. AYOUSTIN

    AYOUSTIN Silver Member

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    Just a little bumpity bump. Got bored last night and found that Kelford now offers cams for us. They're pretty well loved in the evo community and others. I will say, I'm not too sure about how I feel about their grinds. Kind of odd their B grind has more lift on the exhaust side. Looks like they kept overlap to a minimum as well. Fortunately they offer custom grind options!

    http://www.kelfordcams.com/global/camshafts/mazda/mzr-2-0l-lf-ve-2-3l-l3-vdt-disi-turbo?engine=3

    Edit: Looks like they also offer 62lb and 84lb beehive springs:

    http://www.kelfordcams.com/global/kvs17-valve-spring-set.html

    http://www.kelfordcams.com/global/kvs17x-valve-spring-set.html
     
    Last edited: Apr 20, 2017 at 9:08 AM
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  2. Enki

    Enki Motorhead Platinum Member

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  3. Realgib3

    Realgib3 Greenie Member

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    Not a fan either, but likely for different reasons that you. I think the durations are overall "ok", but they lifts are designed to be used with stock or stock style pistons that do not have provisions for larger valve reliefs. I would just never go through the trouble of putting cams in a stock engine, so that's useless to me and if I'm going to build, I would use pistons that could take a real cam, lift wise.
     
  4. Enki

    Enki Motorhead Platinum Member

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    I don't think you need huge amounts of lift to make power though; huge duration is all well and good but not if you're just dumping air back out into the intake or opening the exhaust before the piston has fully harnessed energy from the power stroke.

    I mean, look at the cam grind difference between stock:
    Stock:
    Stock cams.PNG
    Kelford Stg 3:
    [​IMG]

    Its bleeding pressure from more of the power stroke and allowing more air to leave the cylinder during the compression stroke. There's also a bunch of overlap which won't be good for reversion depending on the exhaust setup.

    Hell, even Piper does that (stage 2):
    piper stg 2.PNG

    Overlap in the cams can be pretty bad for us, considering direct injection and all.
     
  5. AYOUSTIN

    AYOUSTIN Silver Member

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    1. You can't really map out a cam profile like you have unless you know your ramp rates.

    2. Having a longer blow down period is done to minimize reversion during overlap. So in this case opening up the exhaust valves earlier isn't hurting much.

    3. Same thing on the compression stroke, the air is still filling the chamber and closing the intake valve later doesn't necessarily mean you're losing air charge.

    There's easily 50whp on a middle of the road cam like the piper S2 for most people who have built engines.
     
  6. Enki

    Enki Motorhead Platinum Member

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    I realize that and I know I'm just using a generic ramp rate for everything but all the ramp rate will do is plateau out the lift profile; in some cases a more aggressive ramp rate reduces power output on the sim. As a side note, there's enough information for the piper cams to calculate a close approximation of the ramp rate since they provide both seat to seat and .050 numbers.

    Also, just about any non factory cam grind will produce more power; that's not what I'm trying to say. I'm just saying that the grinds that are offered don't appear to be very good in terms of valve event timing for our displacement/headflow/rpm numbers.

    It will be very amusing to me if I put down really good numbers at low boost with less intake valve lift than stock.
     
  7. Maisonvi

    Maisonvi Silver Member

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    You kids and your crazy attempts at VE. Just do it the old fashion way, more boost


    Sent from my SM-G900V using Tapatalk
     
    Maisonvi, via a mobile device, Apr 22, 2017 at 12:47 PM
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  8. Enki

    Enki Motorhead Platinum Member

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    Actually I wanted a little more DCR too, which is part of the reason why I went the route I did. I spent quite a bit of time figuring out what would be good and what wouldn't in the engine sim and came away with a compromise that I'm pretty satisfied with. If it works out well for me, I'll release the grind info and part number.
     
  9. KCi

    KCi Greenie Member

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  10. Enki

    Enki Motorhead Platinum Member

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    Yep, you're right. The sim didn't allow a negative intake valve open number in the mode I was using to fill in data. I've corrected that and the new map/numbers are below.

    Nice bump in VE:
    Kelford VE.PNG

    And power to boot (360 chp 320 ctq @ 15 psi):
    Kelford Power.PNG

    This is with an otherwise stock engine and head (without factoring in intake manifold restriction). Still room for improvement though; a quick iterative test generated a cam profile that at 15 psi pushes 456 chp and 384 ctq but it falls way outside of what I personally consider acceptable cam timings for our platforms specific fueling requirements.

    If Kelford revised this grind to do nothing more than open the intake valve at TDC (all other numbers the same; this increases intake duration to 238 degrees), peak VE would remain just about the same, but the VE curve flattens out slightly and power production jumps to 395 chp @ 6500 and 350 ctq @ 5500 with HP remaining over 350 until right around 9200 rpm. Still not really a big fan of the intake valve closing when the piston is almost halfway up the cylinder (edit: for a daily) but eh, to each their own.
     
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