Drag Race Optimization.

Discussion in 'SRT Hellcat Performance' started by CasualObserver, Feb 10, 2015.

  1. CasualObserver

    CasualObserver Senior Hellcat Member

    Joined:
    Feb 7, 2015
    Messages:
    100
    Likes Received:
    54
    Trophy Points:
    68
    Vehicle:
    Charger SRT Hellcat
    I just took delivery of a hellcat and plan to hit my local drag strip when the weather allows ~late April. In the mean time I would like to glean some information on what works and discuss the efficacy of some ideas on what my help get the pig moving (with a focus on optimizing what you have as opposed to modifying). I am new to the dodge/challenger platform; any information would be appreciated. I have however drag raced quite a few times in my day;-)
    1. Does anyone know of an 18" or 19" rear wheel fitment? There is a lot more to choose from as far as drag radials are concerned in those sizes. Also the other benefits of running a smaller wheel are 1. more shock absorbing sidewall and 2. less rotating weight/inertia. As an example I know that it is possible to squeeze even a 17" rear wheel onto my GTR with STOCK sized brakes. The 20" radials are ok, but there is more to be had with a smaller wheel. Thoughts?
    2. Race gas. Is there anyone here familiar enough with how the stock ECU deals with boost/timing/knock adjustments to comment? I am curious as to whether or not filling the tank with VP MS109 and pulling a battery terminal would allow the ECU to relearn on high octane fuel I suspect this may be part of what allowed the hellcat that ran into the 10.40s trap so high??
    3. ICE. From what I gather the hellcat has an intercooler/ heat exchanger coolant loop that is divorced from the engine cooling loop (HOORAY!). My car is in storage for the moment so I cant run out and check. Assuming there is a decently sized coolant reservoir, does it look like Ice can be added to temporarily raise IC efficiency and drop IATs? If not that may be one mod I would make and do. Nothing wakes up a car with an air to water intercooler like a little ice. Also, it is safer since it lowers IATs. I suspect that this in conjunction with high octane fuel will give us everything the stock tune has in reserve.

    Any one else with experience/insight, please do share!
     
    • Like Like x 1
  2. wolfmann442

    wolfmann442 Silver Member

    Joined:
    Feb 17, 2015
    Messages:
    119
    Likes Received:
    82
    Trophy Points:
    198
    Vehicle:
    Challenger SRT Hellcat
    As soon as the weather breaks, i am going to try lighter wheels, 109 unleaded, icing the intake, etc...
     
  3. CasualObserver

    CasualObserver Senior Hellcat Member

    Joined:
    Feb 7, 2015
    Messages:
    100
    Likes Received:
    54
    Trophy Points:
    68
    Vehicle:
    Charger SRT Hellcat
    Sounds great, let's compare notes. I too am waiting for the weather to break.
     
  4. Top Cat

    Top Cat Gold Member Hellcat Car Club Gold Supporting Member Fastest Cat/Record Holder HCC Charter Member

    Joined:
    Nov 26, 2014
    Messages:
    1,925
    Likes Received:
    1,079
    Trophy Points:
    768
    Location:
    Doylestown,Pa
    Vehicle:
    Challenger SRT Hellcat
    Save yourself a lot of work and run a 100 shot of nitrous, it will do two things.
    1 lower ATI's
    2 add HP with a denser charge of O2 that the ECM will add fuel for, it can make small changes as needed.

    As far as wheels, 17,18 will fit over the stock Brembo's
     
  5. hellcat1

    hellcat1 Gold Member

    Joined:
    Sep 27, 2014
    Messages:
    10,668
    Likes Received:
    2,026
    Trophy Points:
    778
    Location:
    Michigan
    Vehicle:
    Challenger SRT Hellcat
    I have always heard bad things about using that stuff,, heard it was really hard in the internals of the engine
     
  6. Top Cat

    Top Cat Gold Member Hellcat Car Club Gold Supporting Member Fastest Cat/Record Holder HCC Charter Member

    Joined:
    Nov 26, 2014
    Messages:
    1,925
    Likes Received:
    1,079
    Trophy Points:
    768
    Location:
    Doylestown,Pa
    Vehicle:
    Challenger SRT Hellcat
    Only if you get stupid and run a big shot without proper tuning, keeping to a 50-100 max there should be no issues, hell we do it now on the 6.1 stock engines...and they are not forged..

    BTW, if you do add it also run some 109 mixed in with the 92-93
     
    • Like Like x 1
  7. CasualObserver

    CasualObserver Senior Hellcat Member

    Joined:
    Feb 7, 2015
    Messages:
    100
    Likes Received:
    54
    Trophy Points:
    68
    Vehicle:
    Charger SRT Hellcat
    The ECM Will see the lower ait temps but doesn't necessarily know how much oxygen is being carried in additionally, that sounds like a great way to lean it out unless you can command the ECU to add more fuel, additionally there is no way to pull timing as of yet.

    Hellcat1,
    Nitrous is simply a way to make more cylinder pressure. The dangers typically have to do with 1. Too lean an air/fuel ratio, improper timing retard, running too big a shot at too low an RPM.

    Assuming the tune is good some people still get into trouble spraying too much at too low an RPM. A 150 shot is going to make cylinder pressure necessary to make 150 horsepower regardless of the current RPM of the engine. If you do this at 1500RPM vs. 4000RPM there will be a HUGE discrepency in cylinder pressure.

    Assuming nitrous is implemented properly it Is not particularly dangerous.

    As far as stock engines go the hellcat engine will probably cope well with nitrous. It is build from the factory to cope with the high cylinder pressure seen in forces induction use. That being said how much you can stack on top of the blower before going boom remains to be seen.

    Thanks for the tips on wheels I figured a 17" wheel will fit over the rears. Does anyone know what width and offset can be accommodated? I bet 1.4 short times could be seen with a 17" drag radial and its forgiving sidewalk, also it would be easier on the drivetrain.
     
  8. CasualObserver

    CasualObserver Senior Hellcat Member

    Joined:
    Feb 7, 2015
    Messages:
    100
    Likes Received:
    54
    Trophy Points:
    68
    Vehicle:
    Charger SRT Hellcat
    Good idea, in lieu of timing adjustment just throw more octane at it.
     
  9. hellcat1

    hellcat1 Gold Member

    Joined:
    Sep 27, 2014
    Messages:
    10,668
    Likes Received:
    2,026
    Trophy Points:
    778
    Location:
    Michigan
    Vehicle:
    Challenger SRT Hellcat
    But , you said don't run it without a tune,, the hellcat has no tune yet!!!
     
  10. CasualObserver

    CasualObserver Senior Hellcat Member

    Joined:
    Feb 7, 2015
    Messages:
    100
    Likes Received:
    54
    Trophy Points:
    68
    Vehicle:
    Charger SRT Hellcat
    It makes me nervous, as top cat pointed out though, the high octane fuel will make the combo of power adders more tolerant of advance ignition and leaner air fuel ratios.
     
    • Like Like x 1
  11. Nycsrt

    Nycsrt BANNED

    Joined:
    Nov 19, 2014
    Messages:
    1,651
    Likes Received:
    804
    Trophy Points:
    563
    Vehicle:
    Challenger SRT Hellcat
    His math is correct car has auto learn ecu wit knock sensor by which gas and automatically makes changes to timing
     
  12. CasualObserver

    CasualObserver Senior Hellcat Member

    Joined:
    Feb 7, 2015
    Messages:
    100
    Likes Received:
    54
    Trophy Points:
    68
    Vehicle:
    Charger SRT Hellcat
    The only concern I have is that the raised octane may prompt the ECU to throw MORE timing at the engine and potentially more boost than it would otherwise and then you would be spraying on top of that. In the mean time if your octane is high enough all should be forgiven hopefully... There is a lot to learn about the ECU Boost/timing/fueling strategies before we can make these assumptions.
     
  13. rw99

    rw99 Silver Member

    Joined:
    Feb 13, 2015
    Messages:
    192
    Likes Received:
    79
    Trophy Points:
    178
    Location:
    Castro Valley, CA
    Vehicle:
    Challenger SRT Hellcat
    Strictly speaking re: stock configuration (no nitrous), octane over 94 is unlikely to provide any benefit. As configured from the factory, "...on 93 pump octane, the vehicle spark curve is very close to MBT (Mean Best Torque), meaning there is little power to be had with higher octane fuel and its opportunity to advance spark further." That's straight from an SRT engineer.

    BTW, that lambda we see on the AFR gauge is from a true wideband... and the car does know what fuel you're using, obviously.

    So, for those of us limited to 91 from the "normal" pump :mad:, find somewhat higher octane for your trip to the drags. And remember that you don't need a heavy tankfull of the stuff when you get there.


    Rich
     
    • Useful Useful x 2
  14. wolfmann442

    wolfmann442 Silver Member

    Joined:
    Feb 17, 2015
    Messages:
    119
    Likes Received:
    82
    Trophy Points:
    198
    Vehicle:
    Challenger SRT Hellcat
    Hmmmmmmm, i have a Compucar bottle in a bag on the shelf...
    :cool:o_O
     
  15. Blackdevil77

    Blackdevil77 Silver Member

    Joined:
    Feb 1, 2015
    Messages:
    538
    Likes Received:
    132
    Trophy Points:
    153
    Location:
    Long Island, New York
    Vehicle:
    Charger SRT Hellcat

Share This Page

Search tags for this page

how to drag race hellcat