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4.5L V8 Turbo Corvette & 2016 Flagship Cadillac Sedan

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#1 · (Edited by Moderator)
We Learn GM Plans 4.5-liter V8 Turbo for Corvette, Flagship Cadillac Sedan Coming in 2016
Carscoops
September 18, 2013


We recently came across some interesting information from a credible source about future products for GM's Chevrolet and Cadillac brands, and which to some extent, are interconnected.

We'll begin with Chevrolet as we learned that the Corvette's immediate future includes a more potent version of the 4.5-liter twin-turbocharged and direct-injection engine that GM debuted on the Cadillac Elmiraj Concept just last month.

We're told that the new V8 will most likely be used in the successor of the Z06, rumored to be called Z07. While in the Elmiraj, it produced an estimated 500hp, in the Corvette, it could push out as much as 600 horses (unconfirmed).

Full article at link.
 
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#56 ·
The reality is that turbo motors will become more prevlent as time passes, thier power density, compact dimensions, low weight combined with the flat torque "curve" will make them the engines of choice for almost all cars. Expect to see engine families that have more than a single cylinder count, like the LT pushrod family including both a V6 and a V8 configuration. We will see the same thing in the current LFX family with V6 and V8 cylinder configurations and possibly a V10. GM already has plans for an inline configuration of 3 and 4 cylinder engines for small cars, displacing 1.0 to 1.5 litres. With the latest gen family II four gm has the capability to produce 2.0, 2.3 and 2.5 litre fours. We will see more technology in terms of turbos, low pressure, high pressure asymetrical, multiples turbos and sequential turbos. Additionally we will see variable valve lift become more common, the introduction of "Dual Mode" engines that can opperate as traditional 4 stroke engines and as Atkinsens cycle engines to reduce fuel comsumption. Start/Stop will become standard on just about every car and truck sold. Low cost Electric launch assit will be wildly available as will hybrid systems as battery/charge technology improves. The next 4 to seven years will see significant change in the way manufactures handle powertrain design.
 
#65 ·
There was similar rumors (about 2 years ago) that future Corvette (i'm not sure if it was C7 stingray or future ZR1) will get something like 3.x l V8 twin turbo 10000rpm or something like that.
I doubt there is any chance of Corvette getting this type of engine. I don't think it will even get this 4.5 l v8 TT.
I think 6.2 l v8 (n.a and forced induction) will be only v8 that Corvette will be using..
And for Cadillac. I think it would be nice if Cadillac would getsome sort of their unique engine..but does this 4.5 l v8 even exist? There is no pictures or any additional info on this engine. Maybe GM is just discussing about putting this type of engine in Cadillac..but are there any test mules or anything like that for this engine?
 
#66 ·
I'd like to throw out a question about supercharged engines. If a dohc engine breathes better than an ohv engine when normally aspirated, would that still be true when running 2200 psi fuel pressure and several multiples of normal air pressure? Wouldn't the supercharging create a far better breathing engine whether it has 2 intake valves per cylinder or only one?
Said another way, perhaps a supercharged ohv engine would be less complicated, more compact, lighter and more reliable than a dohc version, while giving equal or better power?
With that being a possibility, perhaps GM could use the sbc engine with thicker walls, large bore and short stroke to produce a 9,000 rpm monter that at 4.5 liters could pump out 200 hp per liter, while being reliable and able to fit into all its vehicles, but in particular withe corvette, the Cadillacs, and performance vehicles from all GM brands?
What do the engineers on here think?
 
#71 · (Edited)
It not only breathes better, but - presuming you are talking latest-tech on both it also combusts better with less hot spots, due to a better head shape and more even atomisation (and smaller cylinders mostly achieve better burning than large with better preignition control), and the ability to route ports to equalise flow. GM's smallblock V8 family achieves a very good tradeoff of performance, cost, size, weight. You can get a 6.0 litre plus motor that is externally physically small and light. For example, a BMW 4.0 litre V8 weighs within 10 or 20 lb of an LSx motor and is a similar size. The LS motor, due to a longer stroke and bigger bores will produce similar hp 10-20% more torque - but from 50% more capacity. HP is torque x rpm, the DOHC motor has more potential is it simply revs harder, also due to shorter stroke and lower mean piston speed. There is a mechanical limit in metres/second to how fast the piston can run down the bore without outrunning oil's capacity to lubricate. Plus loads on the crank, big-end bearings, rods and piston itself. Longer stroke, the piston is travelling faster and accelerating/decelerrating faster on change of direction to achieve any given rpm. That cycles stresses and loads through the assembly.

The point about downsizing the smallblock to 5.5 or 4.5 litres even turbo'd is silly. Why would you do it? It will be the same size/weight as the large capacity versions, pretty much but give away it's capacity advantage. The OHV motor cannot rev as hard, or use as aggressive cam profiles as there is a lot of inertia in the pushrod, rocker and large single valve which reduces it's overrev capability. So you aren't going to get 8000 streetable, reliable rpm out of it.

The large single valve and port shape actually impedes ingress into the cylinder, and per cylinder 1 large valve and port does not flow cfm of air or mixture so well. One big port flows less than two smaller ports added together whose valves fit into the combustion chamber - and port velocity can be most critical at low rpm to optimise low-end power. Idle quality of a large 2v OHV setup is harder to achieve - especially combined with large capacity.

All things being equal - and manufacturers have single cylinder slave engines to check this out - if you take the same bottom end assembly and fit it with an OHV 2-valve head, it will be lighter, cheaper, more compact which are all advantages in some respects. With 4v DOHC - talking about best practice in both architectures - it will rev harder, have slightly more friction (cam drives and tensioners, bearings, followers on buckets) althought lower valve drive inertia per valve and better valve control which will allow higher rpm. So capacity/capcity it's 'easy' to get good power/torque out of a VVT DOHC layout - at greater cost of manufacture. All the time, makers are going smaller and smaller with forced induction. If you were planning a small four today, you'd use 1.2-1.6 litres, DOHC, variable valve timing 4v, DI, maybe turbo. You wouldn't build a OHV 2.0 litre, for the cost savings on manufacture and reduced weight and component count, because it would make your emissions/economy/performance targets harder to hit and your car harder to sell, which is being penny-wise, but pound foolish.

The issue - and it's one that stings the smallblock increasingly in the urban world - is around town economy. 30+mpg hwy is amazing from a V8 in a Corvette. But really, is it? Not when the same car is probably down almost in single digits in heavy traffic, where it's light weight and low rolling reistance via aero can't help it. It's why Audi went from V8s to supercharged sixes. It's why BMW is dropping the V10 from the big Ms in favour of turbo eights and the V8 from the M3 to go back to a turbo six, Merc will drop the 6.2s for smaller turbo motors. Big motors (and you can't use AFM at idle or high-load/low speed because of NVH issues) suck fuel when idling and at slow speeds - especially, performance versions. Even if you fitted stop-start.

I don't think they'll go to a turbo 4.5 for the topdog Vette - the new car in stronger than ever and been made to take supercar power so it will get the forced induction version of the LT1. The 4.5 is also not a bored/stroked HFV6. It could only go to 3.8 litres with no liners and coated bores (nikasil) and you wouldn't achieve cylinder sealing for turbocharging without bigger spacing between cylinders, not reliably for certified powertrain standards.

They could use the 3.6 reciprocating assemblies in a new motor but if so it will need a new block and heads so they aren't going to bother with 60 deg, split crankpins or dodgy balancing acts. It'll just be a 90 deg. conventional quad cam V8 and achieve a perfectly-balanced V8, is my bet. Probably the Ultra program resurrected. The HFV6 is very compact for a DOHC design, a V8 off it would just be slightly longer.

A twin turbo 4.5 makes sense for a large Cadillac, as does the 3.0 for China. Few people know, but the Caprice sold in China as the Park Avenue and the same car sold as the Daewoo Veritas in Korea came with a 3.0 V6 as the base motor. In Europe, A8s come with FWD n/a V6s for fleet duty. The BMW 5 and 7 both come with the 3.0 turbo. 3.0 litres is a magic number for many countries. High fuel price, CO2 taxes or both simply mitigate against large displacement motors. Urban congestion makes big motors superflous, largely. A Smart ForTwo is just as fast in a traffic jam as a Lamborghini - probably faster.

So - and it is not a bad thing - GM builds a highly-refined OHV alloy motor that enables people like Holden to stick it in a mainstream passenger car and sell it for 1/3rd what an equivalent German car cost. Or, HSV can bring out a LSA-engined car that costs 1/3rd of it's European counterparts and be within smidgeons of their performance. The problem is, regardless of merits, the market for it is going away.

At one time during the life of Gen IV, there were about seven or eight versions of the engine: alloy 5.3 for cars, iron 5.3 for trucks, alloy 6.0 for cars, different 6.0 for trucks (not counting Holdens L76 and L98). 6.2 for both, LSA, LS9 and LS7. I'm betting there will be only four versions of Gen V. 5.3 and 6.2 for trucks, LT1 and the supercharged version. The US don't use a 5.3 in cars anymore. They aren't going to need a ridiculously and insanely powerful V8 motor, just a maniacally-powerful one. The LT1 will produce similar practical performance in Alpha to the LS7 in the Zeta Camaro.
 
#73 · (Edited)
I take the opposite view to the OP article,

It gets back to why do people buy V8s in premium products and what are their expectations...
why have a small more complicated V8 in a high series vehicle when in recent times, buyers have
shown a desire for the complete opposite, large capacity V8s with lots of torque....

If GM was going to do a small capacity V8 twin turbo engine, it would be as a diesel alternative
in Silverado, Suburban and Tahoe, primarily to amortize costs more quickly. Such an engine with
450 hp and over 500 lb ft of torque in an efficient large vehicle - what's not to like..
 
#76 ·
Smaller displacement with turbos is the way the competition is going, and with good reason. A good combo of power and fuel economy. GM will have to go the same way to keep up. And hey, if we can still get good power with the bonus of better fuel economy, then that is great! This 4.5 L turbo sounds great to me, though I doubt it will reach 600 horses.
 
#79 ·
DOHC engines make more horsepower per displacement (generally) due to their head flow raters. This actually comes from having two intake valves and 2 exhaust valves and not from being DOHC as opposed to OHV. Some of the port gen IV SBC heads have flow rates as high and higher then DOHC 4 valve head designs. For example the stock LS3 heads flow at 315CFM, while some after market LS3 heads flow as high as 360 CFM. LS7 heads can flow at over 400CFM, though this is only one part of the power equation, it does show that some of the OHV head designs are nearing parity with the DOHC head designs when it comes to flow.
 
#83 ·
Real World fuel economy does NOT show improvements with smaller displacement twin turbos versus the new gen 5 v8

EPA fuel cycle maybe but not always.

This argument of ohv vs Dohc is sooooo old.....yet the corvette continually whips the competition...

I'd suggest the cost size weight and performance of the 52 grand c7 speaks for itself..

As a c6 z51 owner the ohv 6.2 liter engine is a blast and the real world reliability and fuel economy are amazing.

I'd never want a twin turbo Dohc 4.5 liter instead of the new LT4 that's planned as a supercharged 6.2 for the z06 ...

We'll see the details at the January Detroit show.
 
#88 · (Edited)
guionM

My "proposal" does not create more issues than it's worth.

"Changing the banks from 90 degrees to 60 creates a whole new engine, and therefore all parts from crankshafts to heads from existing engines can not be used."

I was not suggesting that the engine should be changed from 90 degree V to A 60 degree V. The LFX engine case is a 60 degree V6 and I am suggesting that a series of 60 degree engines would make the cost of limited production "premium" engines far less than the cost of developing an all new engine. I was quite specific about the engines I was suggesting.

"It makes it easy to produce 3 very different engines, a 60 degree V6, a 60 Degree V8 with a split pin crank and a balance shaft, and a 60 Degree V10 with a split pin crank and a balance shaft. At 3.6, 4.8 and 6.0 respectively they share the same internals except for the crankshaft, further reducing the cost to produce."

As to turbos and heat in proximity to aluminum the issues are doable, after all aluminum heads have cumbustion chambers that see the flames of cumbustion and exhaust ports that carry hot exhaust gasses. With the narrower 60 degree block there is more space for the turbos and heat sheilding and cooling ducts.
 
#90 ·
Ford's 4.6/5.0/5.4/5.8 OHC engines are virtually the same width as the old 427 SOHC and BOSS 429 engines, dressed! Remember, the raised block 5.8 currently used in the GT500 does NOT fit in the next-Gen Mustang, while the LT1 certainly WILL fit in the Alpha-based ATS and Gen-6 Camaro, with or without a supercharger...

"Size matters". And so does displacement. Someone here mentioned the horsepower race, as we've come to know it over the last decade or so, is coming to an end. Witness Porsche's 918: BIG power through technology and hybrid utilization. Do NOT expect massive weight-to-power improvements, generally, with the exception of the ZR1 (or whatever the highest hp Vette is called).

Why?

CAFE '16. Fuel economy IS a significant factor. For EVERY model and manufacturer. Without exception.

Supercharger vs. turbo(s): Engine-driven superchargers have a parasitic effect on hp AND fuel economy AND, therefore, emissions. The engine must work harder to create that extra boost. Exhaust-driven turbos have less parasitic losses and, with modern-tech turbos combined with improved electronics, can create boost with far less "turbo lag" than previously experienced and only "as required". With multiple turbos, lag can be almost non-existent. And less parasitic losses means better engine efficiency, aiding the fight for better mileage and lower emissions. The trade-off, with multi-turbos, is expen$e...and HEAT.

In this marketing climate of 5-year/100,000 mile warranties, building 4.5L V8s with 6-700 NET hp strikes me as being a fond wish. Those who have such power plants (regardless of whether DOHC or otherwise) do NOT warrant them to this extent.
 
#97 ·
You're on the right track, but you're (much like Ford), not realizing one thing:

Turbo in gas engines cannot be sized for as broad of a powerband as people expect. So, you can make a smaller turbo that does well for fuel economy (like the 1.4L Cruze), or you can build one for all-out horsepower (GTR). The size of the turbo dictates the sizing of the exhaust to it, which greatly changes the engines torque curve. A modern supercharger, when not in use (idle, highway crusing/etc), has about as much parasitic drain as an a/c compressor and alternator, usually less than 1/2 of a horsepower. Thanks to controls avaible to bypass a supercharger, you can add boost without changing the engines NA powerband nearly as much. In a diesel, the narrow powerband works better for turbo sizing.

On a side note, It has been my personal experience that 2v motors general get better fuel economy than 4v ones of the same size. Furthermore, 4v singlecam engines tend to get better fuel economy that dual cam 4v engines. Despite seeing this first hand in the real world, I have not seen it reflected by EPA ratings, much like EPA ratings seem to claim normal automatics do as well as manuals when they simple do not.

(Case in point: Mitsubishi's 2.4L 16v SOHC versus 2.4L 16v DOHC and their 2.0L 8v versus 2.0L 16v[lancer engine but NOT the evo model])
 
#98 ·
Not going to fit Dohc engine under the low corvette hood.

Gm looked at all engine possibilities and chose what they feel is the best.

The gen 5 v8 is an amazing power plant. Those wishing for Dohc twin turbos need to shop other brands. What other sports car capable of the corvette total package performance gets as good gas mileage or costs the same?

None and that's why the corvette continues its iconic existence.
 
#99 ·
I'm happy to hear that GM is finding ways to spread out the cost of developing a HO DOHC V8 for Cadillac, but does its inclusion in the Corvette spell the death of the LS7? I mean, I'll probably never be able to afford a car with either engine, so it's a little irrelevant, but the LS7 just seems like such a wonderful engine. I'd hate to see it go.
Also, is the inclusion of a DOHC V8 an evolution for Corvette or a major change in the car's character (maybe both)?
 
#100 ·
Dohc v8 is never happening for the low hood line of the c7 and the LS7 production is over with the z28 I believe in January.

Twin turbos not coming for the c7. Gm prefers the packaging with supercharger s for corvette.
 
#110 · (Edited)
^^^ This. Forced induction or actual AFM that is. I think a CTS-V with a Twin-Turbo V8 600HP with AFM would be an absolute marvel of engineering. I believe that can be achieved with the LT1 or this DOHC 4.5L. I think that it is an absolute neccesity for Cadillac if they are going to have vehicle in this class with CAFE only a spit away

Supercharged 6.2 for the win...(kidding)
Turbo 6.2L would be better.

The S/C LS3 (LSA and LS9) were quick, but effective fixes for GM's need for mega powered V8s as a low cost option that was both effective for them, and satisfying to us buyers. Its time to move forward, and GM has quite frankly the best engineers in the world under its charge and Dan Akerson has apparently allowed them to get the lead out and do what the must to compete. By best engineers I mean not only super-competitive performance product, but super-competitive performance product that does not break down on the regular. My CTS-V Coupe has been perfect (knock on wood) and I push her like you would not believe every change I get.

Having an Audi, BMW, Benz, Land Rover, or Jaguar is a beautiful experience until your neighbors or colleagues start saying to you on a regular basis "I thought you had a white one..." because you're in a Black Loaner so often. That's not great engineering
 
#122 ·
There was never a Glamour "concept car". Concept cars are what's shown to the public or guests. "Mockups" are the physical clay or foam models that reside in design studios and never see the light of day outside of those making decisions on design and production. Then there's also computer animation (Ed Welburn had a small movie theatre-like place at GM design where he...and certain other executives... can view realistic computer rendered design presentations from all over the world).

The so-called "Glamour" was most likely one of those animations, and at most, it was a clay or foam mockup. There isn't an "Elmaraj" running, get-in-and-close-the-door "concept". If there is a mockup, then like every other mockup, they'll be pictures taken for archives or future ideas, and the lump will either be destroyed or recycled for another vehicle.

corvettes share the same engines with pickup trucks,just tuned for more HP
Nope. More than just tuning. Different heads and cam. I believe connecting rods are different too.

guionM

My "proposal" does not create more issues than it's worth.

"Changing the banks from 90 degrees to 60 creates a whole new engine, and therefore all parts from crankshafts to heads from existing engines can not be used."

I was not suggesting that the engine should be changed from 90 degree V to A 60 degree V. The LFX engine case is a 60 degree V6 and I am suggesting that a series of 60 degree engines would make the cost of limited production "premium" engines far less than the cost of developing an all new engine. I was quite specific about the engines I was suggesting.

"It makes it easy to produce 3 very different engines, a 60 degree V6, a 60 Degree V8 with a split pin crank and a balance shaft, and a 60 Degree V10 with a split pin crank and a balance shaft. At 3.6, 4.8 and 6.0 respectively they share the same internals except for the crankshaft, further reducing the cost to produce."

As to turbos and heat in proximity to aluminum the issues are doable, after all aluminum heads have cumbustion chambers that see the flames of cumbustion and exhaust ports that carry hot exhaust gasses. With the narrower 60 degree block there is more space for the turbos and heat sheilding and cooling ducts.
1.V8 engines balance best at 90 degrees. V6s at 60. That's why these engines are made at different angles.

2. The Aluminum cylinder head is cast, thick, and heat treated. The aluminum rails on the Corvette are thin, and hydroformed. It's kind of like comparing your aluminum pan in your kitchen to aluminum foil.

3. Light a Bic lighter under the aluminum pan, and then light one under the aluminum foil.

Again, twin turbos create a lot of problems.

GM engineers aren't amateurs, nor are they a group who know less than you and I, and I'm pretty sure they have pretty decent IQs. There is a reason they went with strapping a supercharger on the top of an engine over hanging a pair of high heat turbochargers right next to thin aluminum rails. From a weight and fuel economy standpoint, they have all the incentive in the world to use them.... yet they didn't. Nor did they (or Ford) incorporate 60 degree angles when they made their OHC V8 engines (even though it would make assembly and parts sharing easier).... there's reasons these happened.

We all like to think we have all the answers, and that the people who actually are doing this every day and have been for many years for their livelihood simply are lazy, or taking the easy way out. Hardly. As with anyone who is in to their job, they want to take things to extremes and push the envelope, and create new masterpieces.

But realities set in. They have to create engines that fit into a certain space, for vehicles that have to cost no more than a certain price, that can put out a certain amount of power without melting anything, lighting anything on fire, affecting crash standards, can last 200,000 miles, get targeted fuel economy, and can be incorporated into an assembly line with all the space tolerances in tact.

A DOHC, Twin Turbo, V8 will not fit into a space designed for an LS (or now LT) V8.

Someone mentioned that a DOHC V8 will fit in any space designed for a DOHC V6. The person used the logic about compartment width. However, that person completely missed the fact that a DOHC's greatest height and width is up front....right where the hood is tapering down! That's where your cam cover is, and it's the tallest and widest part of the block. As big as a Mustang is, when you look at it's hood from a profile, it's almost unsightly because it bulges upward, and continues almost to the very front of the hood.

What do you think a Corvette's going to look like with something the bulk of a Ford DOHC V8 boat anchor under the hood. It won't fit. When it was pointed out that Mark Reuss said this, the response from a member was that it was just "PR" and that he was just trying to sell cars. Fact is, he was telling the 100% truth. The key reason that GM sticks with pushrods is because of cost, performance, and most of all, PACKAGING. You simply can not do a low, sleek, front engine, rear drive sports car like Corvette with something the physical size of Ford's DOHC 5.0 in it. Look up pictures of the 2 side by side. Ain't happening.

As for Cadillac, the million dollar question is CAFE. GM can continue to do high performance V8s for Cadillac based on the LT1. But to do a special V8, it would have to have a long lifespan to be worthwhile. Northstar lasted nearly 20 years. GM can do continual updates to the LS/LT engine because it goes into a gazillion trucks and SUVs. Therefore it takes less time to make up the cost. GM can go on updating the OHV engines right through the decade every couple of years if it wants to. But a "special" V8 for Cadillac would need volume and or longevity. With NA V6s about to breach the 340hp mark and turbo V6s about to pass 400hp, the need for a regular V8 for the Cadillac line is pretty much gone. Therefore the only place for a special V8 would be on the high end performance cars. Top engines are shared with Corvette because it has the volume to make it worthwhile. If Cadillac gets it's own, say, DOHC V8, the first question to be asked is will it last in the lineup for at least 10 years (say, 2024 or 2025) or will it be obsolete. There's no question like that on the volume V8s due to truck use.

If I can offer anything here, it's that there's reasons for everything. Sometimes they may seem somewhat silly (ie: GM not offering manuals on Chevrolet SS because they're scared it might become too popular and GM will have to negotiate to order more manuals from the supplier), but on questions like why not use DOHC or DOHC and TT on the Corvette, or doesn't Cadillac create a unique DOHC engine for the brand (there was actually one put on ice when GM went bankrupt), then there's typically good reasons.
 
#111 ·
Remember when GM was playing with 3-valve heads? Love to see a 4.5 based on the smallblock architecture, but with 3 valve heads and the Viper's more sophisticated VVT. Add twin turbos and you'd have an unusual engine that's different enough to justify that it's not a truck engine. Focus on making it a smooth torque monster. No need to rev beyond 6000, with a torque plateau that starts just off idle. Maybe even do like Buick used to and name it off its torque rating rather than displacement: love to see a Cadillac with a 450 Eldorado V8!
 
#116 ·
Well TVS blowers will real world hit around 70-75% Efficient. Most turbos will hit 76-77% with some cresting 80%.
Where TVS is a problem is in parasitic losses. TVS blowers are capable of making real boost, and the boost pressure is what causes the drag on the system. While more compact as well the blowers and the space they make available for their intercooling is a packaging problem and are drastically prone to heat soak. That supercharger housing getting hot alone preheats the air quite a bit.

Icing down my blower on my GTP back in the day b/t a run would drop nearly 3 tenths!
The air may not spend much time in a compressor housing, but in a blower case air gets circulated and recirculated and re-compressed (a low percentage but it's there).

But yes, TVS blowers will work sooo much better than what GM typically puts in their vehicles. The TVS blower in the 3.0T (lol at the "T") Audi motors make great power.
 
#118 ·
TVS blowers are wonderful pieces of engineering I have had two different motors with this setup. The torque curve is phoenomal. The main difference is that a blower in the upper hp range may eat up 200+hp. Ie a 600 hp motor at the wheels is really making 800hp to pump that much air. Turbos are more efficient under higher boost levels as they don't pump air off the crank. You naturally need more fuel to run a supercharger at the same boost due to this issues although turbos also require substantial fuel as well. As engines get smaller turbos will be more efficient. Right now very similar.
 
#119 ·
If a smaller displacement turbo is offered (I'd be surprised), then it better be a significant leap in power from the 6.2L LT1 (which is hard to imagine in a production engine) otherwise just stick with the successful C6 engine formulas and make variants of the LT1 in displacement and/or forced induction.
 
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