Thread: Tuning into audible knock, timing and more!

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

    Join Date
    Dec 2008
    Location
    TEXAS
    Posts
    140

    Question Tuning into audible knock, timing and more!

    Background:
    I am tuning the fuel/ignition timing on my Roe GTS. The previous owner was at higher altitude and only had 91 octane available. The timing was way retarded and the AFRs were pig rich high 10s, low 11s. Now I'm leaning it out to 11.8-12.2 as recommended by Sean Roe and advancing the timing. The timing is a trickier subject. I am planning to try out the ignition maps from viperacr.com. Here's a link:
    SOME TIPS AND INFORMATION ABOUT VIPER TUNING

    I am concerned about tuning into audible knock and causing engine damage. Is this how you get to the edge of the tune and then back off?

    Car specs:
    96 GTS
    Roe w/ 5psi pulley, VEC 3
    93 octane
    50/50 water/meth injection with stock jets (325 mL included with Roe kit)
    AEM wideband on after bank 1 collector before cat
    B&B headers, RT hi-flow cats, Bellanger exhaust
    Mobil 1 15w50 (included this because someone mentioned this may be too thick - feedback?)

    Log conditions:
    80s ambient
    70F dew point
    Night
    Sea level
    114 IAT

    Log graph:
    See attached for a recent log. The AFR is still rich and I'm leaning it out. The timing is set at the values provided on '96-02-Viper-SC-L53-9D-A3-S108.cbc' from the VEC cd.

    Ignition timing:
    I also attached a graph showing the piggyback timing alterations for different tunes. I'm currently using the ROE timing and am considering moving to ACR91 then ACR93.
    Legend:
    PAT - Previous owner's
    ROE - from VEC CD
    ACR91 - From viperacr.com 91 octane tune
    ACR93 - From viperacr.com 93 octane tune
    ACR94 - From viperacr.com 94 octane tune

    Path forward:
    Set AFR to 11.5
    Advance timing to ACR91
    Advance timing to ACR93
    Lean AFR to 11.8 or 12.2

    Each step will be checked with runs to check for knock-free operation. I will advance the timing while in the mid 11s AFR because advancing the ignition will increase the AFR due to a longer combustion time in the cylinder.

    Feedback on the plan? I also may have access to a dyno this Saturday. Others have mentioned that a dyno tune will vary from a road tune. I have access to both to get the best results.

    I also have the complete log and tune files. Where is a good place to post them?
    Attached Images

  2. #2
    Enthusiast

    Join Date
    Apr 2004
    Location
    Canada
    Posts
    1,618

    Default Re: Tuning into audible knock, timing and more!

    Hi Eric,

    The PCM of the Vipers dates back from the 90's. This is a very simple computer with limited capabilities. However this makes the tuning much easier since there is not much to tune (only ignition and fuel in function of the RPM and load).

    The weakness is the missing knock sensor. The only way to detect it is through your ears around 2000-4000rpm. Once you get knocking (sounds like sand hitting the fenders) back off 40% the ignition everywhere. If you never heard knocking you can test it under mild load. Retard the ignition and listen ...

    Basically the ignition tuning is based on experience. Sometimes when you buy 93 oct fuel it will knock until you retard the ignition like for the 91 oct fuel => you was just robbed by fuel station

    The ignition tuning is really based on safety. Also leaner AFR will knock easier or it will just bang once (That will be a loud noise and your engin is gone).

    Regarding AFR most power is around 12.8 but the head of the cylinders get very very hot and even a mild knock can kill the ring lands.

    So the most important is to be always on the safe side and never hunt for the last 10-20HP. Those last HPs are very very risky.
    Personnally I always used 94 oct fuel (you can get it in Canada) and was running 92oct ignition map. Then depending on the air temperature I was playing with the AFR map to adjust it around 11.7-12.2.

    Also the Viper is sensitive to air and intake temperature changes. If you do drag racing you will have a different AFR map than for road racing. If you have the Roe air duct it will cool your engin like a fridge when you are on road. That<s a very good addon to lower intake temperature.

    Personnaly the best electronic game that I ever owned was my VEC2. It became like a drug. I spent an entire summer speeding like creazy from 5AM to 6AM every Saturday and Sunday morning on the empty highways tuning my Viper to get the most of torque out of the engin. I was really really lucky and never got a ticket in spite of my high tripple digit speed.

    Finnaly on the advise of my wife and started renting race tracks and our club is the largest private track promoter of the region



    Another Note: since 2 years I am running a supercharged BMW (budget constraint). I learned a lot from my Roe experience and that BMW runs rocket solide because of the mild boost and conservative ignition tuning. I beat the hell out of that BMW and still it brings me every morning to my work.


    Keep the boost low at 6.5 psi and the ignition safe and you will have a lot of fun.


    It is a matter of time before I will own another Roe supercharged Viper .... "I will be back"
    (I have just to pay my house)
    Last edited by Schulmann; 05-07-2009 at 07:59 AM.

  3. #3
    Enthusiast

    Join Date
    Mar 2003
    Location
    Eastern Shore of Maryland
    Posts
    274

    Default Re: Tuning into audible knock, timing and more!

    I have been looking for a solution to detect knock for a while, but haven't come up with anything.

    The problem is that damage can be done even by inaudible knock.

  4. #4
    Enthusiast

    Join Date
    Dec 1997
    Location
    Silicon Valley, CA and Portland, OR
    Posts
    1,810

    Default Re: Tuning into audible knock, timing and more!

    Quote Originally Posted by ViperBing View Post
    I have been looking for a solution to detect knock for a while, but haven't come up with anything.

    The problem is that damage can be done even by inaudible knock.
    Kenne-Bell has a knock sensor that I'm sure you could make work with the Viper (you'd have to drill and tap a threaded hole for the sensor). The full "Knock Out" system is wired into the PCM so that it pulls timing back HARD when damaging knock is detected. It also has a graduated LED gauge that shows the level of knock. In the 'green' range, knock is generally inaudible; in the 'orange' range you can hear the knock and timing is pulled back a little; in the 'red' range it is heavy damaging knock and the timing is pulled back like crazy. I have this system on my Jeep, and it works... I don't think they have a system that's wired into the PCM for the Viper, but at least you could have the sensor and gauge and rely on your right foot to pull back on power if you get into knock.

  5. #5
    Enthusiast

    Join Date
    Apr 2004
    Location
    Canada
    Posts
    1,618

    Default Re: Tuning into audible knock, timing and more!

    To be ownest I think it is a waist of time to install any knock sensor. It won't be enought reliable. The best is to use the ignition maps provided by Sean. They are 100% reliable. And if you are racing or having a dyno session you better buy 5 gallon of VP race fuel and poor it into your tank. That will keep you 100% safe. I used to heavily race my GEN2 Viper and never had any knocking.

    Those last 30HP are very dangerous to get. This is where you make those stupid mistakes and blow up your engin. I prefer to have a 560rwhp reliable Gen 2 Viper that I can race 24h than a 700rwhp Viper that needs special care and fuel.

    Anyhow above 600rwhp the GEN2 Viper will not hold down very well onto the pavement. The suspension and the frame are not as good as on the GEN3. You will need MT tire for drag race or Hoosier for road race above that range of HP. HP is like drugs we never have enough of them

    And don't forget, more HP you put into your Viper more it costs because you have to upgrade stock componants.

  6. #6
    Enthusiast

    Join Date
    Dec 2008
    Location
    TEXAS
    Posts
    140

    Default Re: Tuning into audible knock, timing and more!

    Schulmann,

    What was your tuning methodology to create the ignition maps?

    Did you tune into audible knock and then retard timing? I haven't heard knock before in my car so I'm hesitant to tune it into knock and backing off until I hear that's worked for others.

    When you mention the ignition maps provided by Sean, I am using the only one from the VEC cd. Are there others more tailored for specific fuel octanes? The graph I posted shows the difference in timing between that Roe map and the ones you have posted on viperacr.com. Your 93 map is much more advanced than Sean's.

    My goal is to have a safe tune that gets most of the hp on the table. I'm fine leaving the dangerous 20-30 on the edge, but I want the 70 or so easy ones before that!

  7. #7
    Enthusiast

    Join Date
    Dec 2008
    Location
    TEXAS
    Posts
    140

    Default Re: Tuning into audible knock, timing and more!

    Quote Originally Posted by ViperBing View Post
    I have been looking for a solution to detect knock for a while, but haven't come up with anything.

    The problem is that damage can be done even by inaudible knock.
    Here's some info I've come across is learning about knock detection:

    Guy records knock sensors output onto tape - Knock Sensor Sounds
    Here's one of his recordings of knock - http://home.netcom.com/~bsundahl/kno...rtb11_1_10.wav
    DIY knock detection - DIY knock detection, how?
    They mention some interesting ides such as a 'det can':
    A rather bizzarre and very cheap method is to run some relativly solid plastic tubing onto the engine ( like onto the end of a stud) and the other end goes into the cabin / outside the test cell and is attached to a large open ended tin can with a pipe soldered to the bottom to fix to the other end of the pipe. The pipe is drilled through to give a hole into the pipe from the can base You can then hear det usually as a sharp crackling noise.

    We used this at Cosworth a couple of times would you believe
    *The det can let's the brain do the filtering*
    Knock detection with data out - Phormula - Engine Knock, Detonation and Pre-Ignition Detection and Monitoring Systems

  8. #8
    Enthusiast

    Join Date
    Apr 2004
    Location
    Canada
    Posts
    1,618

    Default Re: Tuning into audible knock, timing and more!

    --------------------------------------------------------------------------------

    Schulmann,

    >>What was your tuning methodology to create the ignition maps?
    I started from those provided by Sean and adjusted them either based on dyno runs or based on road runs using different logging tool.
    If you have an experienced dyno master he will be able to detect knocking from the charts ... On the road you will have to listen to the engine.
    Above 4500rpm you will not be able to detect knocking. The best is to start from the basic maps and never touch them until you are really really experienced.


    >>Did you tune into audible knock and then retard timing?
    That's a way of tuning but the best is to stay FAR AWAY from knocks. I often detected knocks after feeling up my Viper at a different fuel station that I am used to at my house. Really it is beyond imagination what some gaz stations can do to save $100. Beside the race track in Calabogie (Ottawa) the Fuel station had a big add saying that they serve 98 oct fuel. That was barely 92 oct !!!! I think they filled up their old 87oct tanks with 98oct fuel and that gave 92oct. Though they were saying that they sucked out the last drop of 87oct fuel from the tank ...

    However 95% of the time I was tuning the fuel map.
    The Viper is very sensitive to temperature change. Espetially in Canada temperature change can be very dramatical (60F within a couple of hours) with has an effect on the intake temperature.


    >>I haven't heard knock before in my car so I'm hesitant to tune it into knock and backing off until I hear that's worked for others.
    Test it. Use a 94oct map while you have 91oct fuel. Accelerate softly around 2000rpm in 4th gear and you will hear it.
    And other way to test poor ignition map is to put your Viper in 6th gear and push the pedal to the floor around 1500rpm. The noise will be different from the "sand hitting fender". In 6th gear and 1500rpm you will over load the engine in case of poor ignition map you will hear a strange noise.

    >>When you mention the ignition maps provided by Sean, I am using the only one from the VEC cd. Are there others more tailored for specific fuel octane?
    On my CD I had 3 maps: 9 degree, 6 degree, 5 degree. I also exchanged my programs with other Viper tuners. Ask Sean to provide you other programs.

    >>The graph I posted shows the difference in timing between that Roe map and the ones you have posted on viperacr.com.
    >>Your 93 map is much more advanced than Sean's.
    Actually maps are named according to the ignition advance given: 9D (91oct), 6D (93oct), 5D(94oct). I used the fuel octane naming to help people understand why we advance ignition. Fuel octane doen't mean the same everywhere (eventhought it is a standard).

    The fuel in Canada was better quality than the one in Florida (No ethanol).
    One thing that I have learned is that 93oct doesn't mean the same everywhere ... It is a fact. In Rural areas some people tend to dilute their fuel
    In addition I was using 94 oct fuel and W/M injection. W/M acts as a sealer and intercooler and increases the boost.

    >>My goal is to have a safe tune that gets most of the hp on the table. I'm fine leaving the dangerous 20-30 on the edge, but I want the 70 or so easy ones before that!
    Start by playing with the Fuel map. The programs provided by Sean are very good there is no need to modify the ignition.
    Last edited by Schulmann; 05-09-2009 at 06:37 AM.

  9. #9
    Enthusiast

    Join Date
    Apr 2004
    Location
    Canada
    Posts
    1,618

    Default Re: Tuning into audible knock, timing and more!

    Regarding your engine oil: 15W50 is a too thick oil. You will even loose a couple of HP. Stick with the factory 5w30 or 10W30. 15W50 is good for a BMW M3 which has very different setup.

  10. #10
    Enthusiast

    Join Date
    Dec 2008
    Location
    TEXAS
    Posts
    140

    Default Re: Tuning into audible knock, timing and more!

    I might be dropping the car on the dyno tomorrow for more tuning. Could someone send me these different timing maps from Sean (a 91 and 93 octane file)? I sent an email to him earlier in the week and am still awaiting a response.

    I'll advance the ignition and get the car to knock at low load to get a feel for the sound. Good idea to check it out in this way to avoid running the car in knock at high load.

    Edit: Here's my email for the 91 and 93 octane timing files: the 'dot' taaka @ gmail 'dot' com
    Last edited by Red Shift; 05-09-2009 at 02:36 PM. Reason: Added email

  11. #11
    Viper Owner
    Join Date
    Aug 2005
    Location
    San Diego, Ca
    Posts
    82

    Default Re: Tuning into audible knock, timing and more!

    Quote Originally Posted by Red Shift View Post
    I might be dropping the car on the dyno tomorrow for more tuning. Could someone send me these different timing maps from Sean (a 91 and 93 octane file)? I sent an email to him earlier in the week and am still awaiting a response.

    I'll advance the ignition and get the car to knock at low load to get a feel for the sound. Good idea to check it out in this way to avoid running the car in knock at high load.
    When I tuned carlo's car, it was very safe and conservative tune. As you can see "Pats' Tune", I want to try to give the performance, yet keep the car conservative. These motors enjoy the fuel, so high 10's / low 11's is fine. Adjust the tune as you feel, but I would save the tune that was done because lots of time was spent getting it as close as possible for his conditions (AZ heat, temps, etc..). WE had to pull about 5 degrees on the top due to the blazing summer heats..

  12. #12
    Enthusiast

    Join Date
    Dec 2008
    Location
    TEXAS
    Posts
    140

    Default Re: Tuning into audible knock, timing and more!

    Quote Originally Posted by RedSrt007 View Post
    When I tuned carlo's car, it was very safe and conservative tune. As you can see "Pats' Tune", I want to try to give the performance, yet keep the car conservative. These motors enjoy the fuel, so high 10's / low 11's is fine. Adjust the tune as you feel, but I would save the tune that was done because lots of time was spent getting it as close as possible for his conditions (AZ heat, temps, etc..). WE had to pull about 5 degrees on the top due to the blazing summer heats..
    That's good info to know for the coming summer heat. I remember the VEC 3 has IAT correction, but even if it does hold the same AFR (doubt it's right on), the increasing IAT will likely cause detonation if the tune was on the edge at colder temps. Does the PCM retard timing as the IAT increases?

    There should be room to advance the timing a bit moving from 91 to 93 octane. Running that rich is a new perspective to me. It's been getting stronger as I lean it out. I've got your tune saved and I compare updates to it.

    Boost-A-Pump Question: I remember Carlo saying the BAP never pulled through to push enough fuel for the 10psi pulley. It's hooked up, but I wonder how it's working. I've logged duty cycles as high as 98% when the tune was richer. That seems odd for the 53 lb/hr injectors. I haven't hooked up a fuel pressure gauge to see if the system is holding 55psi. That may be a possibility in the shop tomorrow on the dyno.

    Thanks again for the manifold. It's looking sweet in my place and it might help a buddy by giving him a core to get work on so he won't have long downtime on his car

  13. #13
    Viper Owner
    Join Date
    Mar 2006
    Location
    Valrico Florida
    Age
    55
    Posts
    1,654

    Default Re: Tuning into audible knock, timing and more!

    Eric,
    The 93 tune is pretty close to the 6.5PSI tune I was running at the time...but what doomed me was using the stock heat range plugs and a hot tune on a cold day (plugs and IAT make a difference!!!). When I was running more retard, I got some really bad rich misfiring above 5000 RPM. When I advanced the timing above 5000 RPM without doing anything else, the motor really came alive and the AFR came right in at 12.X. Now that I have the forged pistons and am in the 10 +PSI range, timing on the top end is kicking my butt since the revs come on so much faster and I want to make sure the VEC can keep up with the timing curve changes (thus why Sean starts timing changes deep into vacuum vice only during boost conditions)...and you can't hear anything regarding audible knock screaming near redline while simultaniously trying to control this beast (thus a dyno would be ideal). I'm also running the 2-step colder NGK plugs Sean recommends. From what I've read about the head/combustion chamber design, that equates to about a 2 degree retard in and of itself. Also, post your W/M profile so we can see when you are injecting W/M. I had it coming on full tilt at 2000 RPM and 4.5 PSI. As we've chatted about, my new progressive system adds another tuning dimension as well. But it is addictive!!! I would like to see some 10 PSI W/M tuning profiles so I can see where in the world I am..in the ballpark or on thin ice (again).

Similar Threads

  1. Audible Alarm For Private Messages ??
    By ruckdr in forum Board and Site Questions/Suggestions
    Replies: 4
    Last Post: 04-10-2007, 12:17 PM
  2. Knock, knock...New England / NYCT VCA Kart Racing Event @ F1 Boston
    By Jeff Torrey in forum VCA Viper Events and Gatherings
    Replies: 51
    Last Post: 03-19-2007, 08:49 PM
  3. High RPM knock detection and knock theory
    By Schulmann in forum RT/10 and GTS Discussions
    Replies: 10
    Last Post: 01-04-2005, 10:55 PM
  4. Knock, knock, knocking on 11's door......
    By genXgts in forum RT/10 and GTS Discussions
    Replies: 3
    Last Post: 09-17-2002, 09:03 AM
  5. Um, hello economy (knock knock)
    By Ken Larsen in forum Sneaky Pete's Place
    Replies: 6
    Last Post: 07-03-2002, 06:15 PM
Tags for this Thread

View Tag Cloud

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