Twin Charging & Gasoline

Funny thing is that Twin Charging never seems to make the power as well as going with one or the other. Most cases its Turbo Charging that gets you the best results. All those rich jerks rocking 1500+ HP Lambos, 1700+ Vettes and Vipers, and all the muscle car guys with LS motors rocking upwards of 2000 HP just by running a hardcore Twin Turbo setup. Not sure if its just research and development that causes this or a systematic issue. I know many times that Twin Charging tends to cause HP loss from overheating the intake air. I havent looked into it all that much though. Mostly going off what Ive noticed from random encounters with them.

True, but you know why twin charging is becoming more looked into, yes? Turbos lag at the low end and superchargers don't flow as well at the high end. Why not the best of both worlds?

Rotrex superchargers are going about the problem the best way they can think of working within the constraints of today. I've said it before, these superchargers really do look like the best iteration of a belt driven turbocharger … so far. These are the superchargers Koenigsegg is using.

There's also Bosch's solution with variable flow turbochargers (seen on some Porsche models and the Acura RDX). These use a flapper valve to block some of the intake tract at low RPM to allow what little exhaust gasses there are at those engine speeds, to spin the impeller faster.

One solution, and one seen in the '98 Mustang Super Stallion is to have the supercharger on a clutching system. In the Mustang, the driver may turn on/off the supercharger at will. Other manufacturers (Volkswagen) have set it up so the supercharger automatically disconnects at RPMs where the turbocharger starts and they reconnect the supercharger once the engine comes back down through the rev's.

Right now twin charging might be seen as a gimmick, just like right now humans live to circa 88 years old. Give science and research more time and neither of those statements will be true. I am all for people tinkering more with twincharging because in their 'tinkers' will come the solution.

http://www.torquecars.com/tuning/twincharging.php

Chrysler....ahem...Benz also used the supercharger a la clutch on the Crossfire SRT6.

Nope I aint givin no stoopid scientologist no money or time. I want it all right NOW! The turbo lag issue is hardly an issue anymore though. Tandem Turbo and Bi-Turbo setups have basically made it so minute that its hard to notice any. One big Turbo and one small Turbo gives you at the moment better overall performance and reliability. And true, given time along with R&D and I bet we will have amazingness. Pretty soon we will have cars that during rush hour traffic will drive for you while the flow is under 37mph(converted from KPH). I believe it was Audi that was pretty hardcore into this tech and further along into road testing than many other companies at the moment. That would be neat. Auto pilot that is selected based on your mood and toxicity level. Now you could get home shit faced on auto pilot to avoid DUIs. So Im sure that Compound could become a thing. My point was only that so far I hadnt heard much favorable info on it. Maybe the helmet makes it hard to hear and I just missed it

Ex US Squid wrote:Funny thing is that Twin Charging never seems to make the power as well as going with one or the other. Most cases its Turbo Charging that gets you the best results. All those rich jerks rocking 1500+ HP Lambos, 1700+ Vettes and Vipers, and all the muscle car guys with LS motors rocking upwards of 2000 HP just by running a hardcore Twin Turbo setup. Not sure if its just research and development that causes this or a systematic issue. I know many times that Twin Charging tends to cause HP loss from overheating the intake air. I havent looked into it all that much though. Mostly going off what Ive noticed from random encounters with them.

Alot of that is because many of the people who use twin turbo's use two identical turbos.

You are supposed to use two different turbos: one that spools easily to provide boost at low rpm and one that spools later to provide boost at high rpms. You're really only using one at a time, but that's the correct way to do it. It better emulates a supercharger.

Personally, I love superchargers and feel they are the way to go for forced induction. However, they do not make use of wasted energy, like turbos do. Ideally, I would design an engine what limited wasted energy by using a supercharger to boost the compression and fuel temp so high in the chamber that almost no fuel escaped into the exhaust system (as heat or otherwise). It's possible. Ever heard of Smokey Yunick? Hot-Vapor Cycle Engines are the real deal... But they wear out alot faster...

I did not know the Crossfire SRT6 used that system; thanks Tux!

Turbos still inherently lag because their design depends on exhaust gasses to spin their impeller which pressurizes the intake air charge. An engine doesn't start producing exhaust gasses until it has taken a breath of intake air. In supercharging, as soon as that crankshaft spins the supercharger impeller spins. Via different pulley sizes on the blower one may spin the impeller to peak efficiency at low engine RPM, in the engine's mid-range, or at high engine RPM. Somebody might read that and think, "Hey, what about three superchargers? Each one providing their best efficiency at the three stages of engine RPM?" I wonder how long it is before someone creates a supercharger pulley that changes its diameter as it spins? Think: CVT, flex fan, thrown Koosh ball.

These only look like turbochargers; they get their impeller spinnin' via crankshaft … Well, turbochargers do also but these use a belt.
Click the picture for more information


Definitely agree with the different sized turbochargers when using multiple in a setup. Isn't there a way to make two identical sized turbochargers provide their boost at different parts of the engine's rev. range through various plumbing of pipes, in their mating to the exhaust manifold/header, blow-off valves, etc? Of course, there's always Bugatti, quad-turbocharging the EB110 and the Veyron.

Sim. What happened to Yunik's design? I got nothin' except this:
Since some big oil or big corporate mogul didn't like what was discovered, they buried it. See also: powering engines with water, the Fish carburetor, and the Pogue carburetor.

Carburetors can be highly efficient though even back then oil moguls didn't want people achieving high miles-per-gallon. If people are buying fuel less often, those who make the fuel get paid less frequently. http://roaring-twenties.com/the_fish_carburetor.htm -"60 MPG in a 1600cc Volkswagen" running one of these carb's.

Nah, it's got nothing to do with oil companies. It has everything to do with complexity.

Those old carbs work, but only for like 30 minutes before the catalysts have to be replaced. Alot of people have just heard that "oh, it doesn't work" line that people don't look into it that often.

On the Hot-Vapor Cycle Engines, they work, but they are expensive to manufacture. They run very, very hot, and at very high-compressions, so they have to be beefed-up. Furthermore, they require more maintenance. You can still make one today if you wanted. (We're making a partial Hot-Vapor Cycle engine for the SAE competition.)

http://www.hotrod.com/techarticles/engine/hrdp_1009_what_ever_happened_to_smokeys_hot_vapor_engine/viewall.html

Simcik wrote:Nah, it's got nothing to do with oil companies. It has everything to do with complexity.…
http://www.hotrod.com/techarticles/engine/hrdp_1009_what_ever_happened_to_smokeys_hot_vapor_engine/viewall.html

I crap you not, oil companies have some, shall we call them "very immoral folks" in decision-making positions. Anything [be it a different method of running an engine, a fuel additive] that adds to fuel economy is swept under the rug. Anything that means customers must buy less (quantity and/or frequently) is not good in their eyes. Referring to that Hot Rod article, this was June 1984 and that Fiero saw as high as 51 highway miles per gallon on 93 octane. If that Fiero earned 51 MPG today, it would be eligible for an HOV sticker so a solo driver could drive in a 'carpool' lane; that's a big deal in Cal.

Simcik wrote:Those old carbs work, but only for like 30 minutes before the catalysts have to be replaced. …

One doesn't run catalytic converters with those carburetors. Hell, catalytic converters didn't start appearing en masse until the 1970s and we had carburetion long before then.

Avanti, I meant "in the carb." Those old hypermileage carbs used catalysts in the bowls to break down the fuel before it entered the chamber.

And I still don't buy the oil company conspiracy. Hell, they make far more money off of plastic that fuel, they'd rather use more of it that way than let us burn it. And I know waaay too many people in the oil & gas industry who are working on fuel savings. It's not a conspiracy, the oil companies just have bigger things to worry about than debunking a few rumors.

Simcik wrote:Those old hypermileage carbs used catalysts in the bowls to break down the fuel before it entered the chamber. …

Gasoline has changed over the course of time- I'm familiar with the M.T.B.E. mess in the '90s. Would these carburetors work with gasoline's earlier chemical makings?

My dad and step-mom lived in the east bay area (Danville) until '01. They enjoy hosting parties (Super Bowl, dinner, and more) and they hosted about a half-dozen while I lived with them. The [then] CEO of Chevron, David O'Reilly came over a handful of times; he's a good guy. There are lots of good people in the petroleum industry; Hell, there are lots of good people on the planet. Many of the good people aren't in position to discuss the 'black book' stuff and these people work on the straight and narrow.

Look at a play: you attend the theater and you see actors on stage. There are more actors on stage than there are members behind the curtain. The people behind the scene make the performance look and sound fantastic. At the closing of the play the actors bow / curtsy and the front curtain drops. So you watched a play and didn't see everybody who made that play possible.

There are bad people pulling strings in high dollar businesses like banking and oil. Whistle blowers work to release information but what good does that information do if the vast majority of the public won't listen?

The stuff I am talking about occurred in the 20s and 30s..

A little back to the compound boost topic.

As far as the turbo is concerned, if its mapped properly and sized apporpriate to its usage, lag should not be an issue.

Even in a max effort, high rpm spool situation, the weight of the vehicle, and the gearing can compensate for much of the lag that may or may not be there. If you are overly concerned with low end power and lower rpm, then the turbo should be sized for those needs and lag will not be an issue.

Another point about sizing and usage. My dad had the Incon Systems 800TT kit on his 91 LX 5.0, it used 2 smallish turbos of the same size. Capable of supporting 800 HP@ 20 psi. in a V8 application. He ran his at 10 psi. to make just over 400 on the stock motor. By 2200 rpm it was making boost, and by 2800 it was at full boost. What lag?

As for compound boost, the supercharger becomes a restriction once the turbo gets rock'n.

Sim, I wonder what issues they ran into in the 50s and 60s? Something or someone sure swept that carburetor technology under the rug.

Stalker, that's what Squid was saying too, where aptly sized turbochargers can reduce the lag a driver feels. The lag I speak of is the lag inherent to the design, where the turbocharger's intake impeller doesn't start spinning until the engine "passes gas." The answer specific to your dad's application would be, "the build up pre-2200 RPM." Since this is only ≈1300 RPM off idle it's not perceived by the driver. That's a good design, I've read lots of cool things about the Incon products.

I'm not knocking multiple turbo setups (see what I did there?), rather I'm intrigued to see companies looking at other setups.

http://www.torquecars.com/tuning/twincharging.php wrote:Most Twincharging applications will follow a few common routes.

Asynchronous or Series, where both work together simultaneously. This is probably one of the easiest set ups to build.

Then we have the inline or Parallel setups, as used by the VAG group where the supercharger provides boost at low RPM and the turbo takes over at a set point into the higher end of the RPM range. A diverter or electronic relay is used to cut between the supercharger and turbocharger.

Just thinking out loud here: Since a supercharger becomes a restriction to a turbocharger, how about making use of relief valves? Routing the piping separately? Or something else …?

I swear howstuffworks.com had a page on twincharging, where the user could click and see the different pieces working separately and then ultimately as a whole unit. This video isn't the one I was trying to find though it shows what Volkswagen did to relieve the bottleneck in the system and have each piece work to its strengths. Question: why couldn't this exact design be up-scaled to the >270 cu. in. crowd?

Here's a diagram of it

Depends on your application I guess.

But if I want to make a shit ton of power and in a car capable of using it, a properly sized turbo will more than get the job down.

Plus all the extra weight of piping, relief valves and whatever else you need to make a compound boost set-up function seems like a waste.

I guess if all you want to do is prove a point, then thats different.

Again: with today's *cough* limited technology- limited in comparison to 15 years from today *cough-ahem* twincharging may be seen as a gimmick but give it time. As with everything the more research put into something the more we'll learn about it.

To loop this back to Forza Motorsport, it contains the 2011 VW Polo GTi, a car equipped with that 1.4 TSi engine. The Polo's upgrade flow chart is interesting. The game calls the car turbocharged, the car doesn't have aspiration conversions and the turbocharger upgrades increase the TQ & HP lines exactly as if one was upgrading both components. The only turbocharger upgrades are sport and race, as the stock setup is better than the street upgrade.

Any-chargers are always a restriction. Turbos block the exhaust flow, superchargers draw crank power. So in the stacking example, if a supercharger is a restriction to the turbo once it gets going, the turbo is a restriction to the supercharger as well.

And, again, no Avanti, it wasn't swept under the table - it's still out there. You can build one yourself and get the same results - but it's ridiculously expensive to build and time consuming to maintain.

Gonna disagree there Sim. I agree they both draw power from the engine to make power.

But a well thought out turbo design and size is more efficient and will make more power than the supercharger. Hence, the supercharger is limiting the turbo, as the intake charge from the turbo is being restricted by the vanes/rotors and or compressor of the supercharger.

Ditch the blower.

I'm with Stalker on this one. As of right now, THE most efficient way to boost power is in turbocharging. Don't believe me? Reference Indycars and LMP1 turbo diesels. If the top tier racing organizations are turbocharging for power, there must be something to it. And, yes, I'm aware Top Fuel Dragsters use superchargers. They also run on the coolest shit EVER!!!!!!!! NITROMETHANE!!!!!!YEEEEEAAAAAHHHHHHHHH!! And the blowers rob over 300hp.

We’re in Forza Motorsport world
Power curves a la Excel calculator "Kitchen Sink" and some 7th gear pulls on the Mulsanne straight.

This is a 1.4L inline 4. Keep telling yourself that because these curves sure don't look like a typical small engine producing ≈175 horsepower. Many little engines producing these numbers generate more horsepower than torque and both peaks shift higher in the range. This engine has a generally flat torque curve starting circa 1700 RPM, which is where full boost (19.1 PSI) occurs and it maintains the same boost to redline. I must admit that Turn 10 nailed the seamless feel between supercharger and turbocharger. [And now confirming through pez2k, find Turn 10 couldn't model twincharging accurately so the coding treats the engine as if it's turbocharged.]

The real world video above claims 1.8 bar (26.1 PSI) at idle though it might be over exaggerating. Something may have been lost in the translation to Forza… we all know that’s possible. The video also speaks about the Golf not the Polo so the claim might be true because the Golf is to the Polo what the Corvette is to the Camaro. That is, even equipped with the same engine the manufacturer will make sure the flagship model has more power.

To get a feel for how this engine stacks up against other engines, let's look at some numbers. There are other cars with larger engines producing less power though I instantly removed cars older than the 1980s and selected a few from the remaining group. Power figures in green the Polo betters / red figures are better than the Polo.

Car	Engine	Torque	Horsepower
2012 Scion tC	nat. asp. 2.5L 4-cyl.	173	180
2007 Nissan Sentra SE-R	nat. asp. 2.5L 4-cyl.	180	200
2003 Hyundai Tuscani	nat. asp. 2.7L 6-cyl.	181	167
1995 VW Corrado VR6	nat. asp. 2.8L 6-cyl.	177	178
1990 Mercedes-Benz 190E Evo.	nat. asp. 2.5L 4-cyl.	181	235

This little engine gives more torque output than engines nearly twice its size and a couple of these cars have 50% more pistons. Granted the Polo engine makes use of a positive displacement supercharger. These type of blowers come rated with a volume labeled in liters: 0.8, 1.1, 1.4, etc. I admit I don’t know how many additional liters of air feed the VW 1.4, which is relevant; these blowers help smaller engines mimic output of larger engines.

I can extend Sim's line of thinking a skoosh. Some restriction in the exhaust before the turbocharger isn't a bad thing as that's what helps ramp up the induction impeller. The exhaust system after the turbocharger should be as wide open as possible.

In all of my recent reading webpages, I found (but can't remember where) a line about a centrifugal supercharger being the better method of increasing horsepower in terms of a single unit design. The reasoning they gave was that maximum boost could be achieved at the highest engine speed (so the blower is continually adding power as rev's increase), boost increases to the square of the engine speed (unlike positive disp. blowers where boost pressure is linear), and the impeller spins as soon as the car idles (unlike a turbocharger). There was more to it but I'll have to stumble over the page again.

Another train of thought: Available banks of cylinders may dictate what power adder is used. This 1.4L Volkswagen only has one exhaust manifold and four cylinders; the decision to install a second power adder on this engine is limited. How's one exhaust manifold bolted to a 4-cyl. engine, fixed at 84.82 cu. in. (which should be firing 1-3-4-2) going to spin two turbochargers? I know it's not physically impossible but there's only so much exhaust gasses 42.41 cubic inches (2 cyl.) can expel. You'd want a dual-Y design manifold pairing 1 & 4 and 2 & 3. In this case one blower assisting one turbocharger works and that could be said for other inline engines.

Many of us here are fans of the 'vee' yes? V-engines have two cylinder banks, you may as well twin turbo a V type engine. New GTR: TT V6. Lingenfelter Vettes: TT V8. Hennessey Vipers: TT V10 engines. A single turbo setup on a V? You could but you're going to be leaving one exhaust manifold [or header] without anything attached to it. Put the opposing four cylinders to work and slap a turbo on the other side. I was considering a twin turbo 377 or 383 stroked '96 LT4 installed in my Stingray. This is also where the twin turbo cars Squid mentions bring big power numbers. I'm not giving those manufactures and tuners a ration of shit, rather I like companies such as Hellion and Volkswagen coming up with alternatives to the norm.

I suppose I'll add DDMWorks to the list. This twincharged Ariel Atom generates 700 horsepower. Noteworthy: built on an engine with one available cylinder bank. … Hmm, twincharged straight 6 anyone?

There are some holes in that Geoff.

For one, there is a point where spinning a compressor faster doesn't help. Thats why there are different sizes, smaller turbos spool quicker, but lose efficiency as more load/rpm is placed on it. Larger turbos are capable of more boost and power in the correct application. If a faster spinning wheel was all we needed, then we wouldn't need larger units. Superchargers behave this way as well, otherwise, you would never have to upgrade to a bigger blower and/or compressor wheel to make more power.

Less cylinders vs. more. Again, sized approprietly, it will not be an issue. Also, some of those 4 cylinders are spinning lots of RPM, that is where all the extra airflow will come from. The 4 bangers in drag racing have HUGE turbos on them, they seem to spin them just fine. All about the application and usage.

Inline vs. V configuration. Lots of the big time drag racers running V8's with turbos are running singles. Less weight and more capability in that particular application. Both banks feed into the turbo, its not just one side spinning the turbo...

You can clearly see both exhaust banks feeding into the turbo on this drag car.... Single turbos are sometimes better depending on your application...

Centrifugal superchargers are great because they boost power output considerably for the cost and complexity of the system. Especially the ones with their own oiling that doesn't tap into the engine's oil supply. Having said that, there's no way around the physics of turbo vs. supercharger. Parasitic loss is greater in supercharging due to the crank running a compressor. Loss is present in turbocharging as well, however it's not as great.

Don't hear me knocking superchargers. They all have pros and cons. Consider this: an electric automotive A/C compressor takes much less engine power to run than a traditional crank driven one. They do the same job, however the method in which the compressor shaft is turned is different. It's very similar to turbo vs. SC.

Okay, we can escalate this discussion if that's where it's going.
Here, some variants of these things ran supercharged Merlin engines (a la Rolls Royce and Packard).

And if one engine is good, two (twincharged Allison V-12s) must be better!


I understand more of the ins and outs of artificial aspiration than written last post. I know blowers and their housings experience diminishing returns and small engines can spin more revolutions. The technology used by racing is cool as they push the envelope: drag racing, F1, the turbo diesel prototype cars, group B rally in the '80s, Can-Am, all forms of racing

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But um, I was simplifying and was keeping to vehicles one would see driving on the street. I didn't mention that before so I'll take that error.

I agree there Tux, Centri-blowers are cheaper, less hassle, and easy to mount over aturbo set-up. If all you want is a fun boost with minimal hassle, thats the way to go.

Geoff, I know I cited race cars, but it could be the circles I've ran in when I used to run on the street, single turbo cars were very common. My buddies 01 GT is packing a single turbo with a 5.4L from a truck, it has minimal lag, and its tons of fun.

Honestly, I'm an all motor guy myself. Too much BS in the engine bay with FI

In one of the pages I read they were saying centri- blowers (relative to positive displacement blowers) were great choices for the aftermarket companies because they're much easier to fit under a hood. Those positive displacement blowers can start actually becoming the intake manifold and hood clearance may be an issue if the blower is thought of in the aftermarket sense.

I like forced induction, though my first car experience was the Paxton equipped Avanti during my high school days. It has the S/C type Tux likes, as it keeps its own oil supply. It's a bitch to change fluid though because there's only one opening in the housing to access the fluid.

My dad has an air compressor and he hooks up a nozzle that looks like a larger version of a modeler's airbrush. The nozzle has a dongle underneath where we hook up a small flexible tube, insert the tube into the supercharger, and place the nozzle into an empty 5 gallon can with a diaper covering the top. Then it's time to push the spray button and out comes the old oil. If you're lucky you get most of the oil in the bucket, some of it on the diaper, and only a little bit blown elsewhere throughout the garage. I've only experienced one oil change and what made it into the bucket was pretty much the opposite of how I described. If you want to spray auto trans fluid all over the place, that's one way to do it.