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Thread: Dyno results dont make sense!

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    Idling - Listen to it purr...
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    Dyno results dont make sense!

    So over the weekend our Miata club event here in CT was a dyno day and I was excited to see the results of my Exhintake mod that I painstakingly labored over because I wanted to make sure I did it perfectly. I have a '96 1.8 with a randall cowl intake, exhintake mod, and 78k on the motor and I topped out at..... 99.4whp and 99ft/lbs. For reference, another NA 1.8 that day with just an exhaust, no other mod and lots more miles on motor, recorded a 113whp. Does anyone have answers as to how this could happen? I am running 18 degrees advanced, and I am going to back that off to 12 or 14 I think, but would it even be possible that 6 degrees of timing is worth 15 whp? or is something seriously wrong with my engine.

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    2,000 rpm - light wheelspin, no bog here! DarylSibcy's Avatar
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    Nothings wrong with your engine bud.

    For starters, it depends on the car, the engine, how it’s been cared for, any mods that have been installed or carried out etc. People tend to assume that everything is built equally and will perform equally, there’s too many variables.

    The ex-intake mod is famously known to bump the power output of our engine’s with little to no extra work. Miata engine’s are naturally choked; as in, they’re not very free flowing, any mod that helps the car “breathe” better will add power - or more appropriately, free up any power it’s being choked of.

    Exhaust mods (starting from the back moving forwards) usually make the biggest difference. Switching to a standalone ECU can provide a big bump, purely from the advancements in technology though.

    You’ve got to remember that these engines were built for Turbocharging originally, meaning air flow was never a major priority as the turbo just stuffed compressed air into the engine anyway.

    Last time I dyno’d my N/A 1.6 I hit 130rwhp on a famously Conservative dyno. My engine is heavily modified, but proves that most of the gains are from breathing mods and not much else.

    Just my .02c
    You want a good car. I want a good miata.

  3. #3
    6,000 rpm - mere mortals would shift HarryB's Avatar
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    What Daryl mentioned is right; however... are you sure your cam timing is OK? Also a CR test would be easy to do for a piece of mind on that front.

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    DarylSibcy (04-23-2018)

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    Idling - Listen to it purr...
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    forgive me for my noobisms, but CR? compression ratio?

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    Idling - Listen to it purr...
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    Everything lined up correctly, 19 teeth between gears

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    6,000 rpm - mere mortals would shift HarryB's Avatar
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    Apologies; compression ratio, yes. Regarding cam timing; I am pretty confident that when doing the exintake mod you need to phase the ex-exhaust cam differently than what was originally intended...

    "If you're doing this on the cheap, you'll want to redrill a stock cam gear, otherwise just use an adjustable cam gear. A new hole will be drilled in the cam gear to reposition the locator peg on the front face of the cam 197.5 degrees from the I tick mark."

    Source: http://www.diymiata.com/exhintake.html

  8. #7
    Idling - Listen to it purr...
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    meaning drilling the locating hole at 197.5 degrees? once the locating pin is at 197.5 degrees CW from the I mark and the I mark on the gear and cover line up, that should mean that the "exhintake cam" is in the exact same location lobe-wise with regards to the valves as the original intake cam used to be in. The big fear and unknown for me is whether that drilled hole was exactly 197.5 or not and whether a slight variation is causing this big decrease in theoretical power, because I think a, pending compression test, "healthy" '96 engine with cowl intake and exhintake should be producing over 99whp

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