What's so great about the 4.9 engine? - Page 2
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Page 2 of 3 FirstFirst 1 2 3 LastLast
Results 16 to 30 of 42
HT4100 4.1, 4.5, 4.9 Discussion, What's so great about the 4.9 engine? in Cadillac Engine Technical Discussion; Originally Posted by 03EscaladeAWD I dont understand why an engine with 4 valves in one cylinder has less power down ...
  1. #16
    ckucia is offline Cadillac Owners Fanatic
    Join Date
    Feb 2003
    Posts
    127

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by 03EscaladeAWD
    I dont understand why an engine with 4 valves in one cylinder has less power down low than an engine with 2 valves in one cylinder. It seems like there would be greater exhaust and intake flow which means more power. Someone educate me about this
    Do you have comparable figures for the 4.9 and the 4.6 at various RPM? I don't know what they are, but I suspect the difference at a given low RPM is pretty minor.

    Think of an engine as an air pump. The 4.9 can process 4.9 litres of air per revolution. The Northstar can do 4.6 litres. At a slow speed, like 1RPM, the amount of air that has to flow through the valves in order to move 4.6 or 4.9 l of air is pretty minimal. However, at say 1000rpm, the 4.9 is flowing 4900 litres of air per minute and the N* 4600. As RPMs continue to increase, the total amount of air flowing through the engine (and thus through the valves) will reach the limit of the capacity of the valves. It is here that multivalve engines have an advantage - they increase the upper limit of how much air can flow into the cylinder, thus they also increase the effective operating RPM of the engine. The valves are essentially the "doorway" into and out of the cylinder.

    In other words, at low RPMs, the engine has excess flow capacity through the valves, so having more valves offers relatively little advantage - the engine isn't using the capacity it has.

    Of course, all things aren't equal. There are all kinds of other considerations including the intake runner characteristics, exhaust characteristics, plus the control and ignition systems, compression, bore, stroke, etc. I'd suspect the 4.9 to have more bottom end torque mostly because it has a slight displacement edge over the Northstar. i.e. its a bigger engine (although only slightly). Because of the other design characteristics, the engineers can build the engine to meet a given specification. The 4.x engines were designed to have lots of torque on the low end and to have an overall lower operating RPM than the Northstar. That's the way they're supposed to be by design.

    There are several reasons why Cadillac put pushrod V8s in their vehicles. A big one is that the technology for a OHC multivalve V8 hadn't yet matured enough to be able to deliver the performance, longevity, and quiet operation that Cadillac owners expect. Pushrod engines have been made for so many years now, that they're nearly bulletproof. The N* is quite a technologically advanced engine, especially in the details, but its also a complicated engine. Also, its easier to make an engine quiet at low RPMs, so an engine that has lots of low-end torque doesn't need to rev high to pull around a heavy car. Cadillacs haven't had a stick since the 40's or 50's until recently, so running a parasitic automatic transmission (with lots of slip to give smooth shifts) was also likely a design consideration.

    All in all the 4.1/4.5/4.9 engines did exactly what they were supposed to do - haul around (relatively) heavy, sedate, FWD cars quietly, with decent performance, and respectable fuel economy.

  2. #17
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
    Join Date
    Dec 2002
    Location
    Fort Lauderdale, Florida
    Age
    49
    Posts
    9,577

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by Panther
    Could the 4t80 tranny be mated to a 4.9, or not? or is there a way to make the 4t60 more heavy duty?
    Can anyone answer Panther's question? I'm interested in knowing the answer too...
    If this site has helped you save money, please consider helping it continue to do so. Click here for information!

  3. #18
    ckucia is offline Cadillac Owners Fanatic
    Join Date
    Feb 2003
    Posts
    127

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by Sal Collaziano
    Can anyone answer Panther's question? I'm interested in knowing the answer too...
    I don't know if they will physically bolt up, but that isn't the big issue.

    The 4t80e is fully electronic controlled. All 4t80e controls are integrated into the ECM (Engine Control Module) to the extent that GM renamed it the PCM (Powertrain Control Module). As far as I know, you can't make the transaxle portion standalone, and since the 4t80e only came with the Northstar, the 4.9 wouldn't be compatible, at least for street use. Even if you could get an early PCM that ran a speed/density EFI system (early N*s were speed/density, later were MAF) and were able to tweak around the engine management incompatibility via changing fuel pressure, etc., you'd need a custom ignition, as 4.9s used a distributor-based ignition, while N*s used a coil pack.

    I'm sure if you could figure out all the above issues, physically bolting the transaxle is easy enough. If it isn't a direct-bolt, then an adapter plate could be fabricated without much trouble. Depending on the clearances, a different torque converter might be required.

    The 4t60 is essentially a beefed up 440t4. You can get transgo kits for them. If the trans is high-mileage, than a rebuild is prudent. Here are shift kits
    http://www.bulkpart.com/cgi-bin/miva...y_Code=440T4sk

    Here are rebuild kits and hard parts
    http://www.bulkpart.com/cgi-bin/miva...ory_Code=440T4

    Here's a place that has transaxle controllers (standalone, I presume) for the 4t80e (among others)
    http://www.transmissionadapters.com/Pricing.htm

    BTW, the 440t4 and 4t60 are electronically controlled, to an extent. ECM signals the torque converter lockup and there are solenoids that manage the shifts. However, with those its more a matter of the ECM telling the transaxle "shift now", and the transaxle uses its own mechanical modulator to determine the shift characteristic. With the 4t80e, the PCM is able manage the characteristics of the shift electronically. I don't know the details, but its more complicated than the half-dozen relays and a vacuum modulator in the 440t4/4t60.

  4. #19
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
    Join Date
    Dec 2002
    Location
    Fort Lauderdale, Florida
    Age
    49
    Posts
    9,577

    Re: What's so great about the 4.9 engine?

    Thank you. So the best bet would be to work on the transmission that comes with the 4.9.. I doubt I'll ever take on something like that - but this is good information to know...
    If this site has helped you save money, please consider helping it continue to do so. Click here for information!

  5. #20
    03EscaladeAWD's Avatar
    03EscaladeAWD is offline Cadillac Owners Fanatic
    Join Date
    Apr 2003
    Location
    Raleigh, North Carolina
    Posts
    244

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by ckucia
    Do you have comparable figures for the 4.9 and the 4.6 at various RPM? I don't know what they are, but I suspect the difference at a given low RPM is pretty minor.

    Think of an engine as an air pump. The 4.9 can process 4.9 litres of air per revolution. The Northstar can do 4.6 litres. At a slow speed, like 1RPM, the amount of air that has to flow through the valves in order to move 4.6 or 4.9 l of air is pretty minimal. However, at say 1000rpm, the 4.9 is flowing 4900 litres of air per minute and the N* 4600. As RPMs continue to increase, the total amount of air flowing through the engine (and thus through the valves) will reach the limit of the capacity of the valves. It is here that multivalve engines have an advantage - they increase the upper limit of how much air can flow into the cylinder, thus they also increase the effective operating RPM of the engine. The valves are essentially the "doorway" into and out of the cylinder.

    In other words, at low RPMs, the engine has excess flow capacity through the valves, so having more valves offers relatively little advantage - the engine isn't using the capacity it has.

    Of course, all things aren't equal. There are all kinds of other considerations including the intake runner characteristics, exhaust characteristics, plus the control and ignition systems, compression, bore, stroke, etc. I'd suspect the 4.9 to have more bottom end torque mostly because it has a slight displacement edge over the Northstar. i.e. its a bigger engine (although only slightly). Because of the other design characteristics, the engineers can build the engine to meet a given specification. The 4.x engines were designed to have lots of torque on the low end and to have an overall lower operating RPM than the Northstar. That's the way they're supposed to be by design.

    There are several reasons why Cadillac put pushrod V8s in their vehicles. A big one is that the technology for a OHC multivalve V8 hadn't yet matured enough to be able to deliver the performance, longevity, and quiet operation that Cadillac owners expect. Pushrod engines have been made for so many years now, that they're nearly bulletproof. The N* is quite a technologically advanced engine, especially in the details, but its also a complicated engine. Also, its easier to make an engine quiet at low RPMs, so an engine that has lots of low-end torque doesn't need to rev high to pull around a heavy car. Cadillacs haven't had a stick since the 40's or 50's until recently, so running a parasitic automatic transmission (with lots of slip to give smooth shifts) was also likely a design consideration.

    All in all the 4.1/4.5/4.9 engines did exactly what they were supposed to do - haul around (relatively) heavy, sedate, FWD cars quietly, with decent performance, and respectable fuel economy.
    Thanks for the info. So the one big reason that the 4.9 has a slight advantage down low is because of displacement. It has more air flowing through thier valves even though it has less valves. So if a pushrod Northstar was made, same displacement, same everything, then the 4 valve northstar would have more horsepower down low. (But only very slightly) All these factors are probably shadowed in performance by the different weights of Cadillacs from the early 90s to present day Cadillacs.

  6. #21
    03EscaladeAWD's Avatar
    03EscaladeAWD is offline Cadillac Owners Fanatic
    Join Date
    Apr 2003
    Location
    Raleigh, North Carolina
    Posts
    244

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by Sal Collaziano
    Is it better than the Northstar? Why? How much power/torque does it have? I'm just curious, really... I'd like to know more about it...
    Does anyone know why Cadillac went from a 500 (8.1 litre) engine all the way down to a 4.1 liter engine? Was it pollution control?

  7. #22
    Katshot's Avatar
    Katshot is offline Cadillac Owners Master
    Join Date
    Jan 2003
    Location
    Newtown, PA
    Age
    55
    Posts
    6,472
    It was that and fuel economy.

  8. #23
    Night Wolf's Avatar
    Night Wolf is offline Cadillac Owners 10000+ Posts
    Automobile(s): Unicycle
    Join Date
    Mar 2003
    Location
    Where I park it
    Posts
    11,009
    AFAIK pushrods have more low end tourqe then DOHC because 2 bigger valves are better then 4 smaller for tourqe....

    Think about geometry, 1 big circle has more area then 2 smaller circles, same thing applies to the vlaves in the engine..... there was a big discussion about this on the Grand Am fourms, maybe I can find it, there was alot of good info.

  9. #24
    Ralph's Avatar
    Ralph is offline Cadillac Owners 10000+ Posts
    Automobile(s): Cadillac
    Join Date
    Mar 2003
    Location
    Saskatchewan, Canada
    Posts
    16,028

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by 03EscaladeAWD
    Thanks for the info. So the one big reason that the 4.9 has a slight advantage down low is because of displacement. It has more air flowing through thier valves even though it has less valves. So if a pushrod Northstar was made, same displacement, same everything, then the 4 valve northstar would have more horsepower down low. (But only very slightly) All these factors are probably shadowed in performance by the different weights of Cadillacs from the early 90s to present day Cadillacs.
    Just be sure to use premium fuel in the 4.9 or it knocks like Mike Tyson in the ring!!

  10. #25
    03EscaladeAWD's Avatar
    03EscaladeAWD is offline Cadillac Owners Fanatic
    Join Date
    Apr 2003
    Location
    Raleigh, North Carolina
    Posts
    244

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by Panther
    AFAIK pushrods have more low end tourqe then DOHC because 2 bigger valves are better then 4 smaller for tourqe....

    Think about geometry, 1 big circle has more area then 2 smaller circles, same thing applies to the vlaves in the engine..... there was a big discussion about this on the Grand Am fourms, maybe I can find it, there was alot of good info.
    I see. They should make more cars without 4 valves. I personally like pushrods too. 99% of people dont rev up to 6000+ rpm daily, so its not really neccessary to have the extra hp up high. So how is gas mileage better with 4 valves if more air can flow through 2 valves?

  11. #26
    Night Wolf's Avatar
    Night Wolf is offline Cadillac Owners 10000+ Posts
    Automobile(s): Unicycle
    Join Date
    Mar 2003
    Location
    Where I park it
    Posts
    11,009

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by 03EscaladeAWD
    I see. They should make more cars without 4 valves. I personally like pushrods too. 99% of people dont rev up to 6000+ rpm daily, so its not really neccessary to have the extra hp up high. So how is gas mileage better with 4 valves if more air can flow through 2 valves?
    AFA millage, well, it all depends..... I don't think that OHV vs. DOHC really effects millage, my 4.9 gets about 20mpg around town, and the Quad4 in my Grand Am (DOHC, what the N* is based off of) get's about 22mpg.....kinda low for a 4banger, but the enigne was designed with performance in mind.

  12. #27
    elwesso's Avatar
    elwesso is offline Cadillac Owners Master
    Automobile(s): 2005 CTS-V, 1994 Infiniti Q45
    Join Date
    Jan 2003
    Location
    Indiana
    Posts
    7,668

    Re: What's so great about the 4.9 engine?

    16mpg city on a Q45 DOHC with clogged air/fuel filters....... DAMN places dont carry stuff for FOREIGN CARS!!

  13. #28
    Ralph's Avatar
    Ralph is offline Cadillac Owners 10000+ Posts
    Automobile(s): Cadillac
    Join Date
    Mar 2003
    Location
    Saskatchewan, Canada
    Posts
    16,028

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by elwesso
    16mpg city on a Q45 DOHC with clogged air/fuel filters....... DAMN places dont carry stuff for FOREIGN CARS!!
    Wes, with mileage like that, you should just have your buddies push you around in it! LOL. PS, did you get the optional rear-end trunk mounted hand warmers as an option for cold weather pushing?? :basketcas

  14. #29
    Night Wolf's Avatar
    Night Wolf is offline Cadillac Owners 10000+ Posts
    Automobile(s): Unicycle
    Join Date
    Mar 2003
    Location
    Where I park it
    Posts
    11,009

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by Ralph
    Wes, with mileage like that, you should just have your buddies push you around in it! LOL. PS, did you get the optional rear-end trunk mounted hand warmers as an option for cold weather pushing?? :basketcas
    my mother, with her '89 Brougham currently gets about 10-12mpg

    We got the carb. rebuilt, but something went wrong becuase it takes forever to start on cold starts, seems like it lost power (307 with power...heh) and millage dropped big time, so we need to call the shop sometime.

    my fathers '85 Bronco with the 351 HO 4bbl get's a smooth 9mph cursing on the highway

  15. #30
    Katshot's Avatar
    Katshot is offline Cadillac Owners Master
    Join Date
    Jan 2003
    Location
    Newtown, PA
    Age
    55
    Posts
    6,472

    Re: What's so great about the 4.9 engine?

    Quote Originally Posted by Panther
    my mother, with her '89 Brougham currently gets about 10-12mpg

    We got the carb. rebuilt, but something went wrong becuase it takes forever to start on cold starts, seems like it lost power (307 with power...heh) and millage dropped big time, so we need to call the shop sometime.

    my fathers '85 Bronco with the 351 HO 4bbl get's a smooth 9mph cursing on the highway
    The '89 should net you approx. 20mpg highway/ 16mpg city.
    If it's got over 120K miles, it needs a timing chain and gears and a PROPERLY rebuilt carb. Those two items should make it feel like new again for you. If not, your mechanic screwed up. I've personally done close to 100 if not more of these and I'm telling you that they run GREAT if done right. Matter of fact, if done right, they'll run BETTER than new.
    And the Bronco should do better than that to. My '95 with the HO 351 got about 12-14 around town. I never checked it on the highway.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting