User Tag List

Thanks Thanks:  0
Likes Likes:  0
Page 1 of 2 12 LastLast
Results 1 to 10 of 11

Thread: Differences between a petrol and diesel exhaust??

  1. #1
    Forum Moderator John LE's Avatar
    Join Date
    Oct 2008
    Location
    Forfar, Scotland
    Post Thanks / Like
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    StatsVehicle Info
    Post Thanks / Like
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)

    Default Differences between a petrol and diesel exhaust??

    I asked this question a few years ago and got no real definitive answer to my question.

    Has anybody seen inside a Vectra petrol and diesel exhaust?

    Reason being that I fitted a petrol Irmscher back box to my last Vec (2.2 DTi) and while I didn't feel an instant drop in power rolling roads seemed to tell a different story

    Before fitting the exhaust I had 155bhp (can't remember the torque figure) and then after I had 143 (just before getting rid of the car)

    Now there had been a good 2 years between fitting the exhaust and getting the second r/r done so i'm not sure if it was the exhaust that caused the loss in power.

    Fast forward to this car (1.9cdti 150) and before getting my remap I fitted the exhaust.

    My before (remap) torque figure was 316nm (which is about right for a standard cdti right?)

    The after figure was 384.2nm which seems to be about 16nm down on what everyone else gets.

    The only thing that I can think is that the, exhaust was fine with a standard map but is slightly restricted by the exhaust when remapped.

    Would this make sense?

  2. #2
    North West Regional Organiser paulvectrac's Avatar
    Join Date
    Mar 2009
    Location
    morecambe
    Post Thanks / Like
    Mentioned
    23 Post(s)
    Tagged
    0 Thread(s)
    StatsVehicle Info
    Post Thanks / Like
    Mentioned
    23 Post(s)
    Tagged
    0 Thread(s)

    Default

    Tbh mate a free flowing or better flowing exhaust is better for eny car tbh but it does seem weired you would loose power especially after you did the exhaust then went for a map when a map is wrote everything in taken in to consideration including any mods is there a chance your using diffrent Dirv ?
    Vectra vxr custome remaps egr deletes dpf and diagnostic work all remaps are custome bench tuning avalible all genuine equipment PM for info

  3. #3
    Forum Moderator John LE's Avatar
    Join Date
    Oct 2008
    Location
    Forfar, Scotland
    Post Thanks / Like
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    StatsVehicle Info
    Post Thanks / Like
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)

    Default

    My before and after were both done at MAS, the rolling roads were done about half an hour apart.

    I just feel that the engine is getting strangled. I'm assuming that a petrol box will have more sound deadening in it than a diesel one and that with soot etc coming out of a diesel exhaust things are getting a bit choked up

  4. #4
    Regular Member rich r's Avatar
    Join Date
    Feb 2011
    Location
    Selby
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    StatsVehicle Info
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default

    A non-turbocharged petrol engine usually has an exhaust system that provides a certain amount of back pressure at low gas speeds, in order to help with scavenging of the exhaust from the cylinders (by promoting a low pressure region between the exhaust gas pulses). Making an exhaust system too free flowing will lose you torque at lower rpm as a result. You can move the peak torque band up or down the rev range quite a bit with just playing with the exhaust pipe diameter, and how the manifold links together. For what is effectively a family car like the Vectra, GM would have aimed to get a good amount of torque at low rpm to help prevent stalling at junctions and generally make it easier to drive at slow speeds such as parking and round town. Obviously that compromises the torque available at high rpm, but most Vectras are probably driven well under half the max rpm most of the time, even the sporty ones.

    Turbocharged engines (diesel or petrol) don't need this, as the turbo itself is a fair old restriction unless it's actually up to speed, and so the exhaust system after it should be as free flowing as possible, as you won't get much in the way of gains that way. The exhaust manifold design is about the only tuning you can do with regards to exhaust gas flow.

    So I suspect that the silencer meant for a non-turbo petrol car that you fitted may well be more restrictive than the original one, designed for a turbocharged diesel...

  5. #5
    Regular Member nutron's Avatar
    Join Date
    Jul 2005
    Location
    South Central England
    Post Thanks / Like
    Mentioned
    6 Post(s)
    Tagged
    0 Thread(s)
    StatsVehicle Info
    Post Thanks / Like
    Mentioned
    6 Post(s)
    Tagged
    0 Thread(s)

    Default

    I have had a couple of custom exhausts on the 1.9CDTI and have different results. The first exhaust they did what I asked them not to and put a big offset back box on which you could see a mile away and use small pipework. The result was firstly a noticeably poor performance low down and secondly I sued them and got my money back. The second exhaust I got was made much better but still a bit restrictive at the back, both were power flow but this one has worked well on two cars now.

    My exhuast at the moment is only standard diameter with no CATs or silencers.

  6. #6
    Banned for Being a Numpty
    Join Date
    Jun 2012
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    StatsVehicle Info
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default

    love to see a video chap

  7. #7
    Regular Member
    Join Date
    Jul 2011
    Location
    Leeds
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    StatsVehicle Info
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default

    On my old DTi the rear box was a straight though job. I dropped a spanner straight through it !
    I tried to fit a petrol back box because it was free and it just made the turbo whistle really loudly.
    I think they are only shaped the way they are so they fit the underside of the car,which is standard across the model range.
    I even ran my car without the back box and it sounded no different !
    Unlike a petrol model ?

  8. #8
    Regular Member Mark-R's Avatar
    Join Date
    Mar 2012
    Location
    Dundee
    Post Thanks / Like
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    StatsVehicle Info
    Post Thanks / Like
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)

    Default

    That was like mine when i was putting my dual on my cdti i fired it up with only the flexy pipe on and it didn't sound much different lol

  9. #9
    Banned for Being a Numpty
    Join Date
    Jun 2012
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    StatsVehicle Info
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default

    you would of thought it b real loud tractor like lol weird that

  10. #10
    Regular Member
    Join Date
    Jul 2011
    Location
    Leeds
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    StatsVehicle Info
    Post Thanks / Like
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Default

    Quote Originally Posted by vectraross View Post
    you would of thought it b real loud tractor like lol weird that
    Aye, the silencer is on the centre section.
    Dealers wanted £111.00 for basically ,a straight through pipe.
    How I laughed !
    I cut off the rusty pipe end and welded the good petrol pipe bit on,lasted 2 years until I part exchanged the car !

Page 1 of 2 12 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Petrol or Diesel
    By Madmarky01 in forum General Chat
    Replies: 5
    Last Post: 5th September 2012, 09:06
  2. Exhaust differences??
    By se4 in forum Vectra C / Signum Car Chat
    Replies: 8
    Last Post: 14th April 2012, 21:34
  3. 1.8 Petrol or 1.9 Diesel SRi
    By gavmckay in forum Vectra C / Signum Car Chat
    Replies: 79
    Last Post: 8th April 2011, 21:57
  4. MIJ exhaust noise differences.
    By Hyperhart in forum Petrol Engine related
    Replies: 2
    Last Post: 8th April 2010, 09:18
  5. The difference between a petrol and diesel exhaust box
    By John LE in forum Engine & Drivetrain
    Replies: 12
    Last Post: 24th March 2010, 19:10

Visitors found this page by searching for:

difference between diesel engine exhuast system and petrol engine exhaust system

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •