ZenVirZan

Hey gang

From my reading here across many of the threads discussing the related topics, I've understood the following fundamentals:

1. Full/half Bridgeported Renesis engines don't make any extra power, due to the fact that the overlap isn't on the expanding chamber side of the stroke, and thus any intake area gains are neutralised by exhaust pulse reversion with no added benefit. There is no physical way to create useful overlap without punching a custom hole in the housing (if possible at all, timing-wise. I haven't investigated it as I don't really care).
2. The Renesis is designed around significantly advancing the port timing compared to its predecessors due to its 0-overlap design. Renesis-RX7 hybrid engines don't make much sense due to the fact that the stock Renesis intake ports begin to open something like 20 degrees earlier than their older brothers (can't find the post to confirm as it was an image ), causing far more overlap than is useful when paired with a peripheral port GSL-SE housing and becomes detrimental (amongst other issues).

iirc most of that info is courtesy of Team.

And while I understand these facts of the universe, it doesn't stop me from wanting a Renesis-based engine, with rotary brap, and also turbo noises (down the line). Primary issue being the brap. No, I don't want to do an FD conversion.
I have a rebuild coming up this week after being on the wait list for a few months (minor coolant seal failure, no smoke or anything, hopefully it hasn't caused too much chaos) and my original intention was to get a full bridge while its out, even though I knew they don't make any extra power. But after reading around, now I'm not so sure I want one (full bridge, that is).

From my understanding, those that have only bridged the secondaries and auxillaries don't experience much of a brap. I'd expect this is to do with the fact that both the APV and SSV are closed at idle, so the only reversion comes from the air space available in the secondary runners acting like a buffer. I'd imagine bridging the secondaries and auxillaries is not a good idea in general, as it exposes the SSV and APV to exhaust directly and may damage the secondary intake manifold. I'd expect the APV is a bit more resilient but still less than ideal and would probably gum it up over time.
My understanding is those with a full bridge do experience a brap, which I assume is due to the primary bridge.

So here's my thought: street port, with the most aggressively bridged primary possible.

The Renesis doesn't need extra intake volume (via bridge, anyway), so the secondary and aux bridges won't be missed.

At idle, there should be significant exhaust reversion via the primaries, which I'd hope is enough to get it brapping. The difference is that once the SSV and APV open, there shouldn't be any reversion backing up those ports as they're not exposed to exhaust at all, which allows them to still flow unobstructed (or at least, relatively compared to a half/full bridge). At a stretch, perhaps that the reversion up the primary could actually provide a small scavenging affect once the secondary and auxillary ports open, using the momentum of some of the reversion to pull additional air in from the other intake ports. Additionally, when it comes time for turbo, the secondary and aux ports should have significantly less reversion to fight, and ideally less power is lost. Yes, some power will still be lost overcoming the reversion and pushing fresh air out the exhaust, but I'm hoping it's not as catastrophic as we've seen in the past.

Thoughts? I'm not sure I've seen any info about how a primary-only bridge behaves.

Please leave "don't bridgeport renesis" comments at the door.

Brettus

iTrader: (2)

I've seen where primary port only has been aggressively bridged and yes ...they do brap.
Concern is how thin the irons are on the primary. When I did my ported engine, I put a 'bridge' halfway along the bridge just so it all held together. That engine is currently in my blue 8 with the small PP exhaust. It has seen plenty of abuse and about 15000kms.
BTW, you will lose power on a turboed Renesis with a bridge ... guaranteed.

ZenVirZan

I'm aware I'll lose power, fingers crossed it's not as bad as on a bridged secondary and auxillary engine. Not aiming for peak power here, I just want something that's a bit more exciting to drive. Glad to hear bridging only the primaries gives the brap.

I'm curious why bridging causes such catastrophic power loss in turbo applications, when many performance engines with overlap manage okay, including older 13Bs. Is that due to the fact that the overlap only affects the exhaust side of the stroke?

Brettus

iTrader: (2)

It's because the exhaust can pollute the intake but can't get that loss back once rotor passes TDC
Not a huge loss ... a small loss versus a stockport though.

TeamRX8

iTrader: (25)

going half-tard is still the same as doing it fully.
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ZenVirZan

When you did your turbo half bridge, did you run into any detonation issues due to the exhaust gas reversion and excess heat in the intake?

Brettus

iTrader: (2)

Not that I was aware of no.

TeamRX8

iTrader: (25)

oh, you were more aware than perhaps you perceived …


half is still the same as full …
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Brettus

iTrader: (2)

I was aware of a power loss .... undoubtedly caused by increased exhaust gas in combustion chamber. So yes that could cause detonation ....but I didn't detect that.
Happy now?

TeamRX8

iTrader: (25)

It was appropriate for a thread that the OP acknowledges the mod as a fail, but still wants to pursue it any way. Whether it creates detonation or not depends on other factors. I don’t recall if you had engine failures when this mod was present or not though.
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Ricky SE3P

iTrader: (10)

Remember that phrase whenever you come around with your snide, egotistical demeanor half the time

TeamRX8

iTrader: (25)

The words only demonstrate that you often fail to perceive the full truth of the matter as well.

i.e. a half Renesis bridge fails just as much as a full Renesis bridge

again, he even acknowledges it as a fail, yet still wants to do it. At some point you have to call it as it really is. You believe yourself to see it as it really is, yet you do not.

I would have said the same thing about yourself if you had proceeded to have the sides of your Renesis rotors machined off as was about to be done. Yet you were wise enough to take heed and not make that mistake. So you’re not utterly without being able to see the truth, yet still stumble into the snare of deception.
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