Two S/C questions about the V - 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 2 FirstFirst 1 2
Results 16 to 23 of 23
Like Tree6Likes
2009-2014 Cadillac CTS-V General Discussion Discussion, Two S/C questions about the V in Cadillac CTS-V Series Forum - 2009-2014; Originally Posted by 6104696 in other words, the best 0-60 and performance times for any given CTS-V (or any other ...
  1. #16
    MacBuster is offline Cadillac Owners Fanatic
    Join Date
    Jul 2012
    Location
    Calgary
    Posts
    355

    Re: Two S/C questions about the V

    Quote Originally Posted by 6104696 View Post
    in other words, the best 0-60 and performance times for any given CTS-V (or any other car with an internal combustion engine) will be attained in New Orleans or in Holland (or in a sub-sea level tunnel?), in cool weather (and proper tires for the temps).......
    But your V will have an advantage at higher altitudes.

    Frankly, it's one of the reasons I don't own a C63 right now.

  2. #17
    M5eater's Avatar
    M5eater is offline Cadillac Owners Connoisseur
    Automobile(s): ATS 2.0T RWD FE3
    Join Date
    May 2011
    Location
    Suffolk, VA
    Age
    26
    Posts
    4,484

    Re: Two S/C questions about the V

    Quote Originally Posted by 6104696 View Post
    in other words, the best 0-60 and performance times for any given CTS-V (or any other car with an internal combustion engine) will be attained in New Orleans or in Holland (or in a sub-sea level tunnel?), in cool weather (and proper tires for the temps).......
    Or @ MIR. I think DA was -1347 that day.

    I managed 12.001 with cold PS/2's and me as a crappy driver.

  3. #18
    Jayfrigginjones is offline Cadillac Owners Member
    Automobile(s): 2009 CTS-V Black, Auto
    Join Date
    Aug 2012
    Location
    Albuquerque, NM
    Posts
    51

    Re: Two S/C questions about the V

    Quote Originally Posted by larry arizona View Post
    The easiest way to come to understand this is no matter if your car is NA or FI, for the same set-up/mods you will always make more HP/TQ at a lower altitude. Density Altitude is a huge factor in performance.
    OK now you mentioned density altitude. This is an aeronautical term for what your aircraft's engine "thinks" the altitude is (the way I understand it). This is a reference to Standard Pressure which is at sea-level.

    These definitions can get confusing so please tell me if and where you disagree with the following:

    Your gen2 CTS-V is in Florida, therefore ambient pressure is ~1bar. The ECM will allow the S/C to create a max additional 0.6bar so the cylinders experience 1.6bar.

    You drive to Colorado where the ambient pressure is ~0.8bar.

    Now there can be 2 scenarios:

    1 -- The ECM measures boost relative to ambient pressure so still only allows an additional 0.6bar, therefore the cylinders experience 0.8bar + 0.6bar = 1.4bar (a 15%loss)

    2 -- The ECM measures absolute pressure and wants to see total pressure at 1.6bar, therefore it allows the S/C to compensate 0.8bar + 0.8bar = 1.6bar

    I would like to think scenario 2 is true, but i'm not so sure. It completely depends on how the ECM measures pressure.

  4. #19
    larry arizona is offline Cadillac Owners Connoisseur
    Automobile(s): 10 V 4DR,6M,Blk,2.55,airaid,160t,W4M HX & tune Eibachs
    Join Date
    Feb 2012
    Location
    Metro Detroit
    Age
    42
    Posts
    1,347

    Re: Two S/C questions about the V

    First off the SC is dumb to the ECM. The ECM and MAF only communicate pressure and temp for proper fueling. The bypass valve is only open under part throttle to help mitigate heat and boost that would effect driveablity. At WOT the bypass is closed and the SC can only spin as fast as the pulley ratio/ engine RPM. So with that understood your two scenarios are simplified:

    At sea level you will have close to 9 lbs of boost stock at WOT and at elevation it will be less obviously.

    Density Altitude is just a formula that takes elevation, temp and humidity on any given day/condition. The lower the DA the better power you will make.

    ----------

    Now a turbo at elevation is a different story, The wastegate can be in the PID loop to allow more boost to compensate for elevation losses. SC's are dumb and have nothing to give feedback and control or have a surplus of boost (overboost) on tap.

    That would be nice if that is how the SC bypass would work, but they don't. If the bypass was wired shut for example at part throttle and say 70MPH steady state on the highway, you would be creating boost which wastes fuel and creates heat. That heat would soak the IC system and when you wanted to go WOT and get max performance, the KR mode would kick in heavily hurting RWHP. So bypass is for part throttle MPG and driveability on a SC car.

  5. #20
    Jayfrigginjones is offline Cadillac Owners Member
    Automobile(s): 2009 CTS-V Black, Auto
    Join Date
    Aug 2012
    Location
    Albuquerque, NM
    Posts
    51

    Re: Two S/C questions about the V

    Quote Originally Posted by larry arizona View Post
    First off the SC is dumb to the ECM. The ECM and MAF only communicate pressure and temp for proper fueling....
    Ok I was missing this piece of the puzzle. How does one learn these things? Where could I get some reference materials on how this engine works?

    Thanks!

  6. #21
    larry arizona is offline Cadillac Owners Connoisseur
    Automobile(s): 10 V 4DR,6M,Blk,2.55,airaid,160t,W4M HX & tune Eibachs
    Join Date
    Feb 2012
    Location
    Metro Detroit
    Age
    42
    Posts
    1,347

    Re: Two S/C questions about the V

    One learns by exactly what you are doing, asking the question . This forum is VERY question friendly. Nobody on here will keep knowledge secret and are happy to share. I have had a couple turbo cars and SC cars with and without a bypass valve, plus I am a Mechanical Engineer by profession so most things mechanical (some electrical) make sense to me.

  7. #22
    MacBuster is offline Cadillac Owners Fanatic
    Join Date
    Jul 2012
    Location
    Calgary
    Posts
    355

    Re: Two S/C questions about the V

    Quote Originally Posted by larry arizona View Post
    First off the SC is dumb to the ECM. The ECM and MAF only communicate pressure and temp for proper fueling. The bypass valve is only open under part throttle to help mitigate heat and boost that would effect driveablity. At WOT the bypass is closed and the SC can only spin as fast as the pulley ratio/ engine RPM. So with that understood your two scenarios are simplified:

    At sea level you will have close to 9 lbs of boost stock at WOT and at elevation it will be less obviously.

    Density Altitude is just a formula that takes elevation, temp and humidity on any given day/condition. The lower the DA the better power you will make.

    ----------

    Now a turbo at elevation is a different story, The wastegate can be in the PID loop to allow more boost to compensate for elevation losses. SC's are dumb and have nothing to give feedback and control or have a surplus of boost (overboost) on tap.

    That would be nice if that is how the SC bypass would work, but they don't. If the bypass was wired shut for example at part throttle and say 70MPH steady state on the highway, you would be creating boost which wastes fuel and creates heat. That heat would soak the IC system and when you wanted to go WOT and get max performance, the KR mode would kick in heavily hurting RWHP. So bypass is for part throttle MPG and driveability on a SC car.
    This is a great response...even though I don't like the answer!

    So one can mostly conclude that our S/C is not helpful at altitude like, say, a turbo would be. That's actually disappointing. I'll avoid those new M5's now.

  8. #23
    larry arizona is offline Cadillac Owners Connoisseur
    Automobile(s): 10 V 4DR,6M,Blk,2.55,airaid,160t,W4M HX & tune Eibachs
    Join Date
    Feb 2012
    Location
    Metro Detroit
    Age
    42
    Posts
    1,347

    Re: Two S/C questions about the V

    It does NOT mean the SC is not useful at altitude. It DOES help alot! The question was did it fully compensate and make a car run the same at high altitude as say sea level. Turbos do a little better at altitude without tuning due to a wastegate, but a SC CAN do better at altitude but it just means you need to increase ratio (pulley) to get equal performance for a given altitude. You can run more overdrive on the SC at altitude. No car runs better at altitude than at sea level. Engines are just air/fuel pumps. Less air (higher altitude) means less power.

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