Thread: 99 ACR w/ exhaust dyno results

Reply to Thread
Results 1 to 13 of 13
  1. #1
    Enthusiast

    Join Date
    Aug 2010
    Posts
    10

    Default 99 ACR w/ exhaust dyno results

    Hey guys, dyno'd my car today at a dyno day.

    The car is a 99 ACR with cat-back.

    Below is the dyno:



    Seems like it is down about 20hp. There was another Viper there with similar mods that did 425hp.

    What I noticed on his dyno chart is that his AF was a bit leaner than mine (looked like a full point).

    Does the AF on my dyno look a bit too rich? Wondering why if thats why it only put down 404.

    Thanks.

  2. #2
    Viper Owner
    Join Date
    Oct 2007
    Location
    Portsmouth, Rhode Island
    Posts
    3,922

    Default Re: 99 ACR w/ exhaust dyno results

    I have a vec 3 for sale that you can throw on your car to tune it. Are you sure the other one didn't have a tune? 425 sounds about right with a tune.

  3. #3
    Enthusiast

    Join Date
    Oct 2000
    Location
    Palm Desert, CA, USA
    Posts
    397

    Default Re: 99 ACR w/ exhaust dyno results

    There were lots of discussions years ago regarding these dyno numbers, and whether just a cat back system would produce much gain. The answer is generally no. It varies of course but look at it like this, 404 hp divided by .88 (typical parasitic losses from flywheel hp as delivered) gives 460 hp. I know you don't like it but it means your engine is delivering the average horsepower as designed and that your cat back system did not add power, only improved sound.

    My Mopar cat back system delivered the same results when it was new, until more significant mods were added.

    Hope this helps.

  4. #4
    Viper Owner
    Join Date
    Jul 2010
    Location
    Bushkill PA
    Posts
    418

    Default Re: 99 ACR w/ exhaust dyno results


  5. #5
    Enthusiast

    Join Date
    Sep 2001
    Location
    alamogordo nm USA
    Posts
    449

    Default Re: 99 ACR w/ exhaust dyno results

    My 2001 GTS with just a cat-back did 399 rwhp on a dynojet

  6. #6
    Viper Owner
    Join Date
    Oct 2005
    Location
    Detroit
    Posts
    908

    Default Re: 99 ACR w/ exhaust dyno results

    It seams a little low, at least on the HP side, but it's not terrible. Go here for Dynojet reference numbers: http://forums.viperclub.org/threads/...no-Day-June-23
    There are two GTS's with your torque numbers spot on, but slightly more HP.
    It's apples to oranges, but my GEN1 pulled 405/443 with a catback. My GEN2 pulled 419/458 with a catback, both on a dynojet with stock tune, 580ft above sea level.
    Go on ebay, buy a brand new SCT tuner for $150, call up Sean Roe and get him to give you a 93 octane NA tune for a catback ($161), and you'll be amazed at the difference. I haven't dyno'd yet after my Roe tune, but I'm blown away by how strong my GEN2 feels now. It almost feels like my GEN1 with 100 shot of nitrous.

  7. #7
    Enthusiast

    Join Date
    Jul 2003
    Location
    GA
    Posts
    2,569

    Default Re: 99 ACR w/ exhaust dyno results

    You do seem rich at lower rpm, but A/F is about 12 (if I'm reading it right) at the top end... which is where you make max HP. Its a safe tune - you could shoot for 11:1 but introducing a piggyback tune for 20HP doesn't seem like a worthwhile tradeoff to me.

  8. #8
    Enthusiast

    Join Date
    Aug 2010
    Posts
    10

    Default Re: 99 ACR w/ exhaust dyno results

    Hey guys, here is a chart from member Viperguynick. He dyno'd at this dyno day as well. As you can see his car is quite a bit leaner than mine, and up about 20hp. I'm guessing the missing power in the AF? Similar mods on both cars.



    What do you guys think? Same dyno, same day, etc..so its directly comparable.

    My thought is since the dyno was using the tail pipe wideband, the reported AF is leaner than it actually is -- I.E. my 12:1 at the top could be 11.5 or richer. Nick's would be right on target then.

    The main thing I'm trying to figure out is if there is an issue I need to "address" (leaks, or something) or if its just a richer calibration on my car from the factory (variance). If its the later, it will just resolve itself as I mod the car and put a tune on it.

  9. #9
    Supporting Vendor

    Join Date
    Feb 2007
    Location
    LA, CA
    Posts
    1,120

    Default Re: 99 ACR w/ exhaust dyno results

    Your numbers are in the range they should be. Stock engines can vary about 5-7%. You could get some more power with a custom tune. If you run on 91 octane fuel then do not get a 93 tune. These engines are very knock sensitive. A tune with more timing may feel good down low but can damage the engine at higher rpm and heavier loads.

    How many miles are on the car?

    Hope this helps.
    Specialty Performance Team
    Dan Cragin

  10. #10
    Viper Owner
    Join Date
    Oct 2007
    Location
    DE
    Posts
    2,585

    Default Re: 99 ACR w/ exhaust dyno results

    Quote Originally Posted by DrumrBoy View Post
    You do seem rich at lower rpm, but A/F is about 12 (if I'm reading it right) at the top end... which is where you make max HP. Its a safe tune - you could shoot for 11:1 but introducing a piggyback tune for 20HP doesn't seem like a worthwhile tradeoff to me.
    Am i misreading your post or are you saying that he could gain power in going from 12.0 to a richer A/F of 11.0. That sounds wrong to me

    Max power for an N/A motor should be around 12.5-13.0.

    Keep in mind that most dynojet widebands read like .7 to lean. This means that if your reading areound 13.5 on your dynojet printout that you are actually running around 12.8 which would be good. (13.5-12.8 = .7)

  11. #11
    Viper Owner
    Join Date
    Oct 2007
    Location
    DE
    Posts
    2,585

    Default Re: 99 ACR w/ exhaust dyno results

    Its hard to give advice based on that watered down dyno printout. Sure that is good enough for what most people are looking for (a pretty picture with a max hp reading) but to me that is amateur night. I'd like to see a graph with a Usefull scale to analize what is realy going on with torque(the actual measured power) & A/F ratio.

    Get the .drf file from your dyno operator if he still has it and email to me. I'll do a screenshot of the important stuff at a better scale and post it here so people can give you advice based on more detailed info. Better yet, get me Viperguynick's as well and i will overlay them so we can do a direct comparison.

    This is what i am talking about. The following is my 1997 with headers & 3"exhaust. All of the power is from 400-500 so there is no need to start the scale at 0, all that would do is compress the data taking away detail from the viewer. I started the scale at 300 to spread the data out and allow room to display the A/F at a larger scale on the lower part of the graph.

    GREEN = Stock Tune
    BLUE = DCPerformance Custom Tune




    (If you want to see larger)

  12. #12
    Enthusiast

    Join Date
    Aug 2010
    Posts
    10

    Default Re: 99 ACR w/ exhaust dyno results

    Quote Originally Posted by Dom426h View Post
    Its hard to give advice based on that watered down dyno printout. Sure that is good enough for what most people are looking for (a pretty picture with a max hp reading) but to me that is amateur night. I'd like to see a graph with a Usefull scale to analize what is realy going on with torque(the actual measured power) & A/F ratio.

    Get the .drf file from your dyno operator if he still has it and email to me. I'll do a screenshot of the important stuff at a better scale and post it here so people can give you advice based on more detailed info. Better yet, get me Viperguynick's as well and i will overlay them so we can do a direct comparison.
    LOL...you da man.

    I will see if I can get the drf files.

  13. #13
    Enthusiast

    Join Date
    Jul 2003
    Location
    GA
    Posts
    2,569

    Default Re: 99 ACR w/ exhaust dyno results

    Quote Originally Posted by Dom426h View Post
    Am i misreading your post or are you saying that he could gain power in going from 12.0 to a richer A/F of 11.0. That sounds wrong to me

    Max power for an N/A motor should be around 12.5-13.0.

    Keep in mind that most dynojet widebands read like .7 to lean. This means that if your reading areound 13.5 on your dynojet printout that you are actually running around 12.8 which would be good. (13.5-12.8 = .7)
    Yep, I'm an idiot. Meant to go up 1 (to 13) rather than down 1 (to 11). Doh.

Similar Threads

  1. Day on the Dyno - Intake, Exhaust, Tune Results
    By 351carlo in forum SRT10 and SRT10 Coupe Discussions
    Replies: 53
    Last Post: 01-11-2012, 08:08 PM
  2. '98 GTS Ported Heads & Exhaust Dyno Results
    By TurboRob in forum RT/10 and GTS Discussions
    Replies: 18
    Last Post: 04-19-2003, 07:08 PM
  3. exhaust dyno results
    By Fast Freddy in forum Viper Racing/Dyno Results/Time Slips
    Replies: 1
    Last Post: 01-11-2003, 07:39 PM
  4. New exhaust - dyno results
    By Bob K in forum Archive Management
    Replies: 3
    Last Post: 04-26-2001, 04:51 PM
  5. Anyone with dyno results of exhaust upgrade?
    By Daffy in forum Archive Management
    Replies: 14
    Last Post: 03-18-2001, 10:43 PM
Bookmarks
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