Twin charged bp

[sketchman]

Ahh OK.

Just found this. Backwards from my idea, but anyone know how well this works?

[Advancedynamix]

That blows into the turbo with a roots style blower and a diverter/bypass valve, exactly as I stated. I wouldn't take advice on supercharging from VW, need I bring up the G-lader?
This system would work better with a centrifugal charger for our cars. VW has a multimillion dollar engineering budget to get the tuning correct on that to make it a boring fuel efficient family car engine.

[koRnhead]

It's just not logical to twincharge things anymore.....it's never worth the headaches. If you simply want the wow factor....Twin turbo a 3.2 sho motor in the rear.

[Advancedynamix]

One huuuge factor that needs to be considered here is the application. We are talking about an ultra lightweight, low rolling resistance FWD car. Big bottom end torque is only going to cause trouble. Engineering an engine for a big heavy RWD car is not going to be a good idea. The trick is an ultra smooth boost curve that pulls for a long time. If the car feels fast, it's probably slow.
Keep in mind that the fastest documented festiva on this site uses a rear mounted turbo! This provides a nice smooth and controllable boost curve. It's no mystery why this car is so fast. I've been next to it on the freeway, pulling to about 100mph and I could hear how seamless and smooth that turbo was. Tractable power is fast. Abrupt and inconsistent torque is destructive and slow.

[bhearts]

One huuuge factor that needs to be considered here is the application. We are talking about an ultra lightweight, low rolling resistance FWD car. Big bottom end torque is only going to cause trouble. Engineering an engine for a big heavy RWD car is not going to be a good idea. The trick is an ultra smooth boost curve that pulls for a long time. If the car feels fast, it's probably slow.
Keep in mind that the fastest documented festiva on this site uses a rear mounted turbo! This provides a nice smooth and controllable boost curve. It's no mystery why this car is so fast. I've been next to it on the freeway, pulling to about 100mph and I could hear how seamless and smooth that turbo was. Tractable power is fast. Abrupt and inconsistent torque is destructive and slow.

Is the term "smooth boost curve"turbo lingo for turbo lag? Or having a big enough turbo to not run out of ooomph on the top end

[koRnhead]

No its having boost thru the Rev range. Lag isn't an issue in a properly set up turbo car. And not having major spikes in power delivery.

[Advancedynamix]

Some may call it lag. It should be timed perfectly for the available traction. When I think of a laggy turbo I think back to a Porsche 930. They didn't come alive until 3-4 grand and they came on really hard. This was the early days of small cars with turbo gas engines and the tuning was not very usable.
Today, we can build a well balanced system that is traction friendly and not laggy. With Ball bearing turbochargers and programable waste gate control, it is possible to build versatility into a turbo system that was unheard of 15 years ago. OEM manufacturers have now stepped up this technology even further with direct injected high compression turbo gas engines that can produce a flat torque curve throughout the rev range.

[Advancedynamix]

No its having boost thru the Rev range. Lag isn't an issue in a properly set up turbo car. And not having major spikes in power delivery.

Or if you want to get complicated, you can explain it like this. Haha. :p

[bhearts]

This is quoting from an outside source over roots styled twin charged setups

To suggest that anything other than the engine itself is the restriction in a boosted setup is completely ridiculous. The fact that everything else significantly outflows the engine is precisely what makes boost. If there was a bottleneck, boost would fall off.

[sketchman]

But one booster can outflow another.

[bhearts]

I'll just have to do it. Just to prove everyone wrong

[koRnhead]

Your quote is taken our of context and if you think that proves anything related to what you have suggested in this post you need to do way more reading on how a twin system works. This isn't a situation where you run to the junkyard grab a diesel turbo and an m90 from a gtp and throw them on the same afternoon.

You stated you're a dreamer.....that's what this is. A dream end of discussion.

[ZephTheChef]

Guys, I wish I had a laptop right now. I have so much to say about this topic. Particularly with respect to the M90 and what an incredible power adder they are. You can hate and speculate all you want, but I have several of them laying around so bhearts gets one for free, they ARE good for at least 500hp in terms of airflow (obviously you lose a ton driving it compared to a turbo and get maybe 350 tops to the ground, but I know for a fact they will spit out 500hp worth of air when overdriven) and will outflow a 16G any day, by a considerable margin, and will in no way, shape, or form, ever be a restriction on an engine of this size. With the bypass open, the pressure differential across the supercharger is nulll and power losses will be limited to whatever it takes to spin the weight of the rotors, or really a negligible amount at the power levels we are talking about. It will not choke the turbo because the rotors are still moving FAR more air than the turbo is putting out, and even if they weren't, the bypass door would begin to act as an actual bypass as opposed to a recirculation door (but that will never happen, all the air will always go through the supercharger and then leak back up into the supercharger inlet through the bypass door...it is not named appropriately for its actual function, it should be called a recirculation valve).

I agree, you make more power turbo only, every time. But I also think a 16G on one of these engines would be strictly a 4,000rpm+ powerband. The m90 on one of these engines is so oversized it may not even be workable, but if it could be driven without belt slip, it would give you a powerband easily from 1000rpm on up, and you would have huge flexibility in gearing. Yes, it's a stupid amount too much. But this is what we do. Because it's ridiculous and challenging and fun to answer the questions of what really can and can't be done.

Furthermore, who cares about "efficiency"? That's a reference to thermal efficiency, not how efficient a power adder is in terms of actual output. This is a completely irrelevant figure when you are properly intercooled. Completely. The only inefficiency then becomes that it takes more power to drive the supercharger so you burn more fuel and put more load on the engine to put the same power to the ground. But that higher loading and such REALLY spools a turbo fast and you can bypass the supercharger very early in the powerband. Does it take more power to spin a supercharger? Absolutely, which is precisely why you would want to bypass it after the turbo spools...you can get almost all of that crank hp back INSTANTLY when the bypass opens, without losing the bottom-end, instantaneous torque provided by having a roots supercharger. It really is the best of both worlds, with minimal compromises. I do think Bryan would be better off with a much smaller supercharger, but since we have plenty of m90s laying around already, the drive pulley will just have to be sized accordingly.

[koRnhead]

OMG you are a fool!!! They can ban me for this post but I'm past caring.....trying to blow boost thru a roots style blower is a restriction. Plain and simple. A turbo and a m90 on a 1.8 litre bp is stupid. An m90 is not a great supercharger it's just not. Are they fun in a Wbody yes. Can you grenade trannys left and right with one in a grand prix of course......but that doesn't make it a great power adder. If it was every big power Wbody wouldn't be switching to turbos. And if they were so great you wouldn't be giving them away for free!!! It's a great paper weight tho. Kinda like a 4g64 crank from a 2g dsm.
Is it great to dream about some crazy ideas, sure thing....you asked what issues you would have doing this and what the reason was no one has done this....that's been answered here many times over.
You do not posses the technical know how to do this. Which leaves you one option to make it happen. Pay someone....Probably looking at 25 to 30 grand when all is said and done to have a goid shop do this for you. Congrats you will have the most expensive festiva worth 500 dollars in the history of festivas. I can only imagine how awesome that would be. Woohoo you win!!!!

[bhearts]

OMG you are a fool!!! They can ban me for this post but I'm past caring.....trying to blow boost thru a roots style blower is a restriction. Plain and simple. A turbo and a m90 on a 1.8 litre bp is stupid. An m90 is not a great supercharger it's just not. Are they fun in a Wbody yes. Can you grenade trannys left and right with one in a grand prix of course......but that doesn't make it a great power adder. If it was every big power Wbody wouldn't be switching to turbos. And if they were so great you wouldn't be giving them away for free!!! It's a great paper weight tho. Kinda like a 4g64 crank from a 2g dsm.
Is it great to dream about some crazy ideas, sure thing....you asked what issues you would have doing this and what the reason was no one has done this....that's been answered here many times over.
You do not posses the technical know how to do this. Which leaves you one option to make it happen. Pay someone....Probably looking at 25 to 30 grand when all is said and done to have a goid shop do this for you. Congrats you will have the most expensive festiva worth 500 dollars in the history of festivas. I can only imagine how awesome that would be. Woohoo you win!!!!

I'm banning you. I hate that we got stuck on the m90 though. I'd be down for using a 62 or 45 if I could find one for a decent price. They aren't terribly smaller dimensionally though. Has anyone ever switched to serpentine on a b motor?