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dwightlooi

Should GM build a "Premium" version of the LT1 for Cadillac?

  

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  1. 1. The hypothetical LT5

    • Is a great idea
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    • Is a lousy idea
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LT5 Premium V8 (hypothetical)

The LT1 is a more than competitive engine for the Corvette and other GM vehicles. But, certain feature decisions pertaining to the LT1 were made to strike an optimal balance between costs and benefitsfor a wide array of applications – decisions which may or may not be optimal for Luxury Performance cars which are less price sensitive. Should a premium version of the LT1 be developed – every much like the LS6 was the to LS2 and the LS7 was to the LS3? Such an engine may fit well into the Cadillac lineup.

Features Added over LT1

  • 104.8 mm bore x 102 mm stroke (7.0 liters displacement)
  • Cam-in-cam independent intake & exhaust VVT
  • 2-stage valve lift control via concentric intake and exhaust lifters
  • Titanium intake valves
  • Titanium pushrods
  • Titanium connecting rods
  • Double wall 4:1 headers
  • Magnesium Structural Oil Pan
  • Magnesium valve covers
  • Trumpeted velocity stacks in air box with 8 linked throttle butterflies
  • Dry Sump lubrication (standard)
  • Raised Compression Ratio (12.2:1)
  • Increased Maximum Engine speed (7100 rpm)
  • Premium 91 Octane Fuel Required

Features Deleted from LT1

  • AFM Cylinder Deactivation (AFM lifters replaced by VVL lifters)

Performance

  • 550 bhp @ 6800 rpm
  • 512 lb-ft @ 4800 rpm
  • Redline @ 7000 rpm
  • Fuel cut @ 7100 rpm

2007-porsche-boxster-s-variocam-plus-variable-valve-timing-and-lift-system-photo-38014-s-1280x782.jpg

Porsche Variocam Plus lifters -- the VVL pushrod lifters will be similar in design except for the location of the camshaft.

Edited by dwightlooi

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Unfortunately, you drive to make engines 91 octane standard doesn't pan out it the real world, as the manufacturers are scared of what happened with that Caddy SRX 2.8, and other uninformed buyer.

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Unfortunately, you drive to make engines 91 octane standard doesn't pan out it the real world, as the manufacturers are scared of what happened with that Caddy SRX 2.8, and other uninformed buyer.

LS7 is premium required.

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91 Octane required does not mean the engine will blow up if you pump 87 octane in the tank. It practically never happens.

What happens is that the engine losses a significant amount of power, will probably fail emissions tests and may go into a limp mode (limiting throttle opening) if you pump 87 octane in the tank. Knock usually happens at high load, low rpms. And, the immediate remedy by the ECU is usually to go rich on the fuel-air ratio. Go rich enough and you can run 14:1 compression on 85 octane. It just means that power goes down, fuel consumption goes up and hydrocarbon emissions can go through the roof. If you do it for years on end you plug up the cat converter too, but this won't happen even with a few tanks of gas and when you lean back up the stuff tends to burn away in over time anyway.

There is no EPA or CARB requirement that a vehicle pass SMOG on the wrong fuel, so the emissions part is a non issue for certification purposes.

Edited by dwightlooi

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Premium fuel and synthetic oil is no big deal for a luxury car, all the German cars require it and people keep buying them.

What would you put this engine in though? CTS-V? A Cadillac flagship sedan has to register around 60 dBA at 70 mph, hard for a pushrod engine to do that. Even the Bentley Mulsanne and Brooklands with all their sound deadening run 65-67 DBA, while Rolls Royce Ghost is 63 and the Phantom is 59. The CTS-V is over 70 dba at 70 mph, too noisy to go head to head with an S-class.

Bentley is dropping the pushrod also in favor of DOHC for all models. That would leave Cadillac with the engine out of a Corvette/Camaro or Charger, while every other luxury car has something else. Hard to convince the masses why Cadillac is right and 12 other car companies that people pay high premiums for are wrong.

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Premium fuel and synthetic oil is no big deal for a luxury car, all the German cars require it and people keep buying them.

What would you put this engine in though? CTS-V? A Cadillac flagship sedan has to register around 60 dBA at 70 mph, hard for a pushrod engine to do that. Even the Bentley Mulsanne and Brooklands with all their sound deadening run 65-67 DBA, while Rolls Royce Ghost is 63 and the Phantom is 59. The CTS-V is over 70 dba at 70 mph, too noisy to go head to head with an S-class.

Bentley is dropping the pushrod also in favor of DOHC for all models. That would leave Cadillac with the engine out of a Corvette/Camaro or Charger, while every other luxury car has something else. Hard to convince the masses why Cadillac is right and 12 other car companies that people pay high premiums for are wrong.

I don't believe the Pushrod configuration or the DOHC configuration affects the noise level. The valve train doesn't make any more or less noise. If you want to cut down on noise and improve refinement you may want to consider doing things like going back to port injection or better yet carburetion, or dropping compression ratio. If you pull all the cost and complexity concerns out of the equation, you may do what Lexus does --use both Port Injection and Direction Injection. Port injection for a quiet idle and cruise refinement, Direct injection cutting in at when maximum power is called for.

Dropping displacement makes the engine less noisy at any given rpm. But it also increases you minimum cruising rpms due to reduced torque.

Edited by dwightlooi

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This is nothing new here. Many of us have already stated GM needs a specail V8 for the new flag ship sedan and what ever variation they may come up with.

At this point it really matter little if it is a DOHC or based on the LT1 The one key element is that it can not just be some engine plucked from the Pick up trucks or Corvette As I have stated here many times it needs to have it's own tune and set up. Also it needs to be dressed up and with real polished/powdercoated aluminum and stainless bits and not just have some plastic cover slapped over it.

If you want a car to be more you have to give it more. Also you want Cadillac to be more than a fancy Chevy you need to give them more or something different. So far the cars have been doing that with the ATS and CTS now it is time for the engines to start doing the same starting with the LTS.

Anything less than a specificCadillac tuned and dressed engine in the LTS will be a mistake. If you want the car to be special then damn well make it special.

I think they dropped the ball on the Eco Turbo in the ATS as they should have given it more power and torque vs the GS.

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Interesting idea! But if you are to change out all those parts who not just develope some DOHC 4VPC DI heads? Or even better yet just take the Altra V8 off the shelf and Turbo Charge it for modern Cadillac use! Cadillac truly needs and deserves its own DOHC V8!

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If GM doesn't offer DOHC v8 (or maybe 3 valve heads on LT version for Cadillac) than this is a least they should offer in premium cadillac model. But i doubt we will see a 7.0 LT version. A 6.2 l supercharger is probably the best and biggest LT GM will have in their LT portfolio.

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What Cadillac really needs is a new transmission. 6-speeds are old news in the luxury market, they should have 8-10, that makes you not need huge engine for quiet highway cruise. Especially in the wake of them pulling the 6-speed manual since every car magazine bashed it. They need a new manual, might as well replace the automatic too. And the 2.0T ATS is slow, not sure if that is the transmission's fault of not, probably is.

I still believe Cadillac needs their own DOHC V8, and they should have a Cadillac only turbo or supercharged V6. Audi and Jaguar both have 3.0 liter supercharged V6s, Hyundai is working on a twin turbo 3 liter V6, BMW has a twin turbo six, so it seems like the boosted 3 liter with low end torque paired with an 8-speed is the hot item for mid-range luxury cars. On the top end, you need a V8 though.

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The transmissions are coming as GM and Ford have joined forces for them. The TT V6 will mostly be used in the Cadillacs for the most part. As of now I would be suprised if they are used in anything else than the Camaro and maybe a C8 or later Vette.

The TT V6 will not be in the Impala or Malibu or any other Buick at this point. That could change but GM is not saying any more.

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Interesting idea! But if you are to change out all those parts who not just develope some DOHC 4VPC DI heads? Or even better yet just take the Altra V8 off the shelf and Turbo Charge it for modern Cadillac use! Cadillac truly needs and deserves its own DOHC V8!

The LT1, for all it's merits, is already over weight. 211 kg vs 183 kg for the LS3 (15% gain in mass). If you switch to DOHC heads the engine gets even heavier (possibly around 240 kg). DOHC heads also make the engine taller and wider. Most importantly though, DOHC heads make the engine less fuel efficient by increasing the internal friction -- four times as many camshafts, twice as many lobes and much greater bearing surfaces in the valve train.

As far as the new autos go, they won't arrive for another 2~3 years.

Edited by dwightlooi

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Interesting idea! But if you are to change out all those parts who not just develope some DOHC 4VPC DI heads? Or even better yet just take the Altra V8 off the shelf and Turbo Charge it for modern Cadillac use! Cadillac truly needs and deserves its own DOHC V8!

The LT1, for all it's merits, is already over weight. 211 kg vs 183 kg for the LS3 (15% gain in mass). If you switch to DOHC heads the engine gets even heavier (possibly around 240 kg). DOHC heads also make the engine taller and wider. Most importantly though, DOHC heads make the engine less fuel efficient by increasing the internal friction -- four times as many camshafts, twice as many lobes and much greater bearing surfaces in the valve train.

As far as the new autos go, they won't arrive for another 2~3 years.

Twin turbo 5.5 l,560+ hp, v8 DI DOHC v8 from Mercedes (m 157)- 204 kg

6.2 l v8 DOHC v8 from Mercedes , 570 hp (M159)- around 200 kg.

BMW 4.4 v8 DOHC twin turbo DI ,from 400- 550+ hp- around 220 kg

Viper v10 8,4 l 640 hp, ohv-around 220 kg

Coyote v8, 440 hp, DOHC -around 200 kg

Now put a supercharger on the LT1 (i doubt GM will increase displacement on this one) to have competitive HP&torque rating and you have an engine with over 220 kg and more. Now when small block has lost advantage on weight and if i have read correctly it is getting bigger in dimensions too (but still not as big as DOHC competition) ,i think GM should think about special engine for Cadillac premium vehicles.

I can see even a coyote v8 with supercharger or twin turbocharger having less weight than a LT1 (LT4).

Edited by dado

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The transmissions are coming as GM and Ford have joined forces for them. The TT V6 will mostly be used in the Cadillacs for the most part. As of now I would be suprised if they are used in anything else than the Camaro and maybe a C8 or later Vette.

Weren't the transmissions for FWD cars only? Or was there to be a rear drive version as well?

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The transmissions are coming as GM and Ford have joined forces for them. The TT V6 will mostly be used in the Cadillacs for the most part. As of now I would be suprised if they are used in anything else than the Camaro and maybe a C8 or later Vette.

Weren't the transmissions for FWD cars only? Or was there to be a rear drive version as well?

From my understanding there were going to be both.

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I think this could work for Caddy once they address the other needs in the product line.

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Well, GM did this with the current Z06 engine, right? IIRC it's a 7.0L hand built version of the smallblock... So doing it for Cadillac could be achieavable. Can't comment on the technical aspects of the engine though...

Edited by ZL-1

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The transmissions are coming as GM and Ford have joined forces for them. The TT V6 will mostly be used in the Cadillacs for the most part. As of now I would be suprised if they are used in anything else than the Camaro and maybe a C8 or later Vette.

Weren't the transmissions for FWD cars only? Or was there to be a rear drive version as well?

Both.

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Interesting idea! But if you are to change out all those parts who not just develope some DOHC 4VPC DI heads? Or even better yet just take the Altra V8 off the shelf and Turbo Charge it for modern Cadillac use! Cadillac truly needs and deserves its own DOHC V8!

The LT1, for all it's merits, is already over weight. 211 kg vs 183 kg for the LS3 (15% gain in mass). If you switch to DOHC heads the engine gets even heavier (possibly around 240 kg). DOHC heads also make the engine taller and wider. Most importantly though, DOHC heads make the engine less fuel efficient by increasing the internal friction -- four times as many camshafts, twice as many lobes and much greater bearing surfaces in the valve train.

As far as the new autos go, they won't arrive for another 2~3 years.

Twin turbo 5.5 l,560+ hp, v8 DI DOHC v8 from Mercedes (m 157)- 204 kg

6.2 l v8 DOHC v8 from Mercedes , 570 hp (M159)- around 200 kg.

BMW 4.4 v8 DOHC twin turbo DI ,from 400- 550+ hp- around 220 kg

Viper v10 8,4 l 640 hp, ohv-around 220 kg

Coyote v8, 440 hp, DOHC -around 200 kg

Now put a supercharger on the LT1 (i doubt GM will increase displacement on this one) to have competitive HP&torque rating and you have an engine with over 220 kg and more. Now when small block has lost advantage on weight and if i have read correctly it is getting bigger in dimensions too (but still not as big as DOHC competition) ,i think GM should think about special engine for Cadillac premium vehicles.

I can see even a coyote v8 with supercharger or twin turbocharger having less weight than a LT1 (LT4).

Dimensionally I don't believe it has grown. If anything the runner in box plenum is shorter in height than the current runner design. The engine is heavy though compared to the LS3 183-> 211 kg represents a 15% weight growth. That's a lot considering that there is no displacement growth and no bore spacing changes.

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The transmissions are coming as GM and Ford have joined forces for them. The TT V6 will mostly be used in the Cadillacs for the most part. As of now I would be suprised if they are used in anything else than the Camaro and maybe a C8 or later Vette.

Weren't the transmissions for FWD cars only? Or was there to be a rear drive version as well?

Both.

Is there an echo in here? LOL!

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Would this premium V8 LT1 be top engine for Cadillac?

Even if we are looking at a present V8 engines this "premium" version of LT1 is behind in torque,HP and weight. Just take a look at 5.5 l v8 TT (m157) from Mercedes. This type of a engine is what will future engine in Cadillac compete against. And not just in flagships. GM can make a DOHC v8,v12,v10 etc. but if it isn't better or equal to a engines from competition GM would be wasting time and money for nothing.

I also think LT1 version like 6.2 l v8 with turbochargers (maybe even a different displacement) would be a better choise for premium Cadillac. Also more important question is will GM be able to show this premium v8 as genuine Cadillac engine and not something which is shared with cheaper cars and trucks.

Edited by dado

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Would this premium V8 LT1 be top engine for Cadillac?

Even if we are looking at a present V8 engines this "premium" version of LT1 is behind in torque,HP and weight. Just take a look at 5.5 l v8 TT (m157) from Mercedes. This type of a engine is what will future engine in Cadillac compete against. And not just in flagships. GM can make a DOHC v8,v12,v10 etc. but if it isn't better or equal to a engines from competition GM would be wasting time and money for nothing.

I also think LT1 version like 6.2 l v8 with turbochargers (maybe even a different displacement) would be a better choise for premium Cadillac. Also more important question is will GM be able to show this premium v8 as genuine Cadillac engine and not something which is shared with cheaper cars and trucks.

An engine like this will fit in as the "Standard V8" for Caddy. Probably as the top engine on the ATS and the run of the mill V8 for the SLS or whatever they chose to call the large sedan. The CTS-V and Top engine for the SLS will probably need to be a supercharged version of the LT engine pulling in 600~700 hp, probably retaining the 6.2 liter displacement for the cylinder wall thickness. Supercharging is easier than turbocharging from a packaging standpoint -- less intake piping and less exhaust plumbing. It will be less efficient, but in that price and performance bracket nobody is actually concerned about fuel costs and "green fashion" buyers would be shopping at Tesla anyway.

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The CTS-V and Top engine for the SLS will probably need to be a supercharged version of the LT engine pulling in 600~700 hp, probably retaining the 6.2 liter displacement for the cylinder wall thickness. Supercharging is easier than turbocharging from a packaging standpoint -- less intake piping and less exhaust plumbing. It will be less efficient, but in that price and performance bracket nobody is actually concerned about fuel costs and "green fashion" buyers would be shopping at Tesla anyway.

Don't forget what top engine does the S class has.It is a twin turbo v12. So this supercharged v8 (if cadilac flagship will go against s class) must not be noisier (no supercharger whine in cabin) than the engine in the S class,Or at least is must not be heard in a cabin .Actually NVH should be on same level.

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Audi, BMW and Mercedes all sell 12 cylinder in their top end car. Porsche, Jaguar and Maserati go with a V8 though, so Cadillac could go the V8 route. Thing is, notice that the M3 V8 isn't used in a 5-series, the M5 V8 not used in the 7-series, the C63 AMG engine not found in an S-class, etc. The current CTS-V engine lacks the NVH needed for a flagship sedan, a CTS-V at 70 mph cruise is louder than the base V6 model. So it isn't as simple as saying the ATS-V or CTS-V engine can be put into a flagship sedan, Cadillac almost needs 2 different V8s.

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