the supercharger has a throttle body pre blower. the tb before the intake mani is replaced with a dummy tb
that's why you always hear about the "throttled volume" issues with superchargers and not turbos
Originally Posted by samnavy
(Post 116278)
I don't get it. I understand the theory in the second sentence, but it says in his sig he runs a JSRC. They're still a hot-side install in this order, right:
Filter-MAF-intake-compressor-charge pipe-TB-intake manifold-runners-engine. That would be sucking through the MAF and blowing through the TB. What am I missing? |
The fixed displacement pump is the biggest difference with a super. If flows a fixed CFM relative to engine RPM at whatever the inlet pressure is. If you lower the pressure at the super's inlet, you flow less air mass, and get less boost and less power. With the turbo, less inlet pressure will just cause less drag on the compressor wheel, causing it so spin faster, and still suck in nearly the same amount (mass) of air. The boost on a turbo being controled by a wastegate also ensures you still get the same boost pressure even with more intake restrictions. You will need more pressure in your exhaust manifold to generate that boost and you will loose some power, but not nearly as much as a super charger would.
Super chargers are much more sensative to air restrictions before the inlet of the pump, which is why a more free flowing AFM has more effect on them. |
I never knew that about the JR setup. It makes some sense now.
https://www.miataturbo.net/forums/at...6&d=1179892018 |
that's superchargers in general, not just the jrsc.
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From reading this forum it's my understanding there are a lot of dummies with superchargers. Now we know that sc's have dummies x 2.
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There are only two ways I know of to really tune an AFM. One involves a dyno and a spec Miata shop and they make 'adjustments'.
The other way is described here: http://forum.miata.net/vb/showthread.php?t=144196 The 'frankenmeter' is sitting on my shelf and is still available. (I don't have enough posts yet to use the classifieds, sorry!) |
Originally Posted by Braineack
(Post 116230)
those runs are at 12psi, ive taken multiple logs, with 203cc and 265cc injectors and couldn't get any good midrange AFR with an acceptable high-end AFR, so the compormise was 12.5:1 from 3-5K and 10.8:1 from 5.5-7K
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Originally Posted by Chris Swearingen
(Post 116263)
Let me start by saying my information is based off a Supercharged application which means that I am pulling air through the AFM not pushing it, but ...
I found the AFM to be a restriction. Swapping to an RX7 AFM made about half a pound more boost with no other changes. My before and after dyno runs show about 10 HP difference, but I had also added an EMU so my A/F ratio was much better. snip
Originally Posted by Braineack
(Post 116268)
snip
I don't doubt it your results; however, it also looks like (12) runs were done in between the comparison with the addition of the EMU, and there is a significant change in the AFR. To summarize what I was trying to represent, the supercharger saw less restriction with the RX-7 AFM as evidenced by the increased boost pressure. |
I believe it form the blow-through perspective, and even on turbo setups because talk of increased boost without and AFM or a larger one (i never really paid attention).
but I think on a turbo setup, since only a bit of vacuum even exisits behind the AFM at something like 12psi, it's not a big deal. |
I believe the results of DIY auto tune and link showed that afm removal made about a 10% difference in stock trim with out major timming changes, and just some more sorted fueling. So in short the only reason for rx7 afm is to modulate fueling better. I love to hear the noise of my intake sucking in the air from my filter. :D even with the AFM installed
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