Boost limits

Discussion in 'The Comp Buzz' started by Jeremy Tanksley, Jul 15, 2013.

  1. Jeremy Tanksley

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    Until a week ago I had not heard that NHRA set a boost limit for the turbo pro mod cars that they (NHRA) control using a now required boost controller. Why did they do this and what advantage does the turbo car have for NHRA to want this ruling of a boost limit? I'm curious as to what NHRA's thoughts are on doing the same for comp?
     
    #1 Jeremy Tanksley, Jul 15, 2013
    Last edited: Jul 16, 2013
  2. Justin Rosen

    Justin Rosen Member

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    http://www.nhraracer.com/content/general.asp?articleid=53523&zoneid=132

    Didnt hear this either. It seemed to work though; looking at the fields they definitely tightened up. I would say that the turbo cars have a big advantage with a boost controller over a blower car; not so much a nitrous car, due to the fact that they can up the boost as they go down the track.

    I wouldnt personally vote for this to be put in effect for comp. We dont have blower, nitrous, and turbo cars all running on one index.
     
  3. Jeremy Tanksley

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    True, but cars in different classes in the other lane racing against it have an index of their own.

    It's the boost limit ruling that raises questions for me.
     
    #3 Jeremy Tanksley, Jul 15, 2013
    Last edited: Jul 15, 2013
  4. comp 670

    comp 670 Active Member

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    It would be tough for NHRA to do the same thing in Comp because there are so many different turbo combos in comp. I ran 30lbs of boost in the t-bird, Milhovets runs over 50lbs I am told, I think Bruno is over 40 lbs or more... Each one of the cars I listed have totally different turbos on them both in size and design and how many (1 or 2 turbos).. In Pro Mod they have a spec turbo they HAVE to run so it's easy for NHRA to police them with a boost controller to keep their performance the same as the other combos in Pro Mod..
     
    #4 comp 670, Jul 15, 2013
    Last edited: Jul 15, 2013
  5. Mark Lelchook

    Mark Lelchook Member

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    Instead of limiting boost, they should just have an inducer wheel size maximum for each turbo class. That dimension will eventually become a restricton.

    Mark Lelchook
    D/ED F/SA
     
  6. Jeremy Tanksley

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    Mark I see your point, but just thinking about it, if the rulebook stated pounds of boost per cubic inch then me and you would be moreso on the same page. However, it's pounds of weight per cubic inch.

    NHRA has the freedom, per the tech directors words, to go in and review each cars data. Thus, with only eight classes in comp running a turbo combination I think they can make a legitimate ruling based on quality data as they did in pro mod to make a boost limit for each of the eight classes. Also, what strikes me as interesting is that most of these classes have been seen to run the same engine combination regardless of slight differences in max turbo size.

    This would be a piece of cake for NHRA.

    P.S.- The way the rules are set up now, a legal NHRA turbo pro mod could come over into comp and run faster.
     
  7. Topsportsman341h

    Topsportsman341h New Member

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    But only if they were going to add 450 lbs
     
  8. Jeremy Tanksley

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    If you're putting some of the current turbo pro mods into AA/AT, then you'd be correct.

    However, there are smaller engines that run competitively in pro mod. One of which is a small block and we got a nice glimpse of it's potential in ennis this year when it was stickered as a AA/AT entry. Under 400 cu. in. and reportedly can run with the big block cars in pro mod at the same weight. To be technical about it, some of these cars could remove weight and up the boost if coming over to comp.
     
    #8 Jeremy Tanksley, Jul 16, 2013
    Last edited: Jul 16, 2013
  9. JustinatAce

    JustinatAce Member

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    NHRA Limited the boost because they didn't want to add any more weight to the cars.. stability and slowing them down becomes the issue.

    The only reason I can see NHRA limiting boost in Comp is if it becomes a safety issue with engines grenading or speeds approaching 300mph.

    You still think it's just as easy as turning up the boost and going faster?

    Why don't you just rev your motor higher?

    They are about equal statements. More boost equals more attrition too.
     
  10. Mark Lelchook

    Mark Lelchook Member

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    There really is no limit on a turbo car that can use any size turbo (s), until the crank falls out the bottom. Boost is pretty much a useless controlling factor, almost a non issue, you have to limit the inducer size to create a restriction. We are revving our engines higher, but we are still limited to atmosphereic pressure, and what little extra we can draw in on the 5th cycle.

    Mark Lelchook
    D/ED F/SA
     
  11. Jeff Childs

    Jeff Childs Member

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    If the NHRA pro mods are currently running 45lbs of boost and then get limited to 20lbs nothing will change? Boost control is much easier and cheaper than reducing the turbo size. Those things are not cheap.
     
  12. JustinatAce

    JustinatAce Member

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    Keeping the rods and pistons in it is the limit.. And limiting boost is limiting atmospheric pressure as far as the engine is concerned. It only allows so much pressure in the intake and pops the wastegate open to keep it at that level.

    So you lose boost, so you just up the compression right? You never get the power back.. Don't believe me? Go tune or drive a turbo or blower car in Denver. You may not lose the .5 second an N/A car does, but you'll be every bit of .3-.4 off running on any fuel except Nitro. It's not pressure that makes the motor run... it's the oxygen and fuel. Typically the more pressure, the more oxygen there is to mix with fuel because of the air volume being compressed. But if the air is only 18% Oxygen, guess what? That 50 PSI of air in the boosted intake is still only 18% Oxygen.

    Where you guys are failing to see the point is, N/A motors could run harder too, but you'll be replacing parts more often... A turbo car is no different, and if anything, HARDER on parts than your N/A motor.
     
  13. Mark Lelchook

    Mark Lelchook Member

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    You are correct, I didnt realize that the pressure limit would be that extreme that NHRA is implimenting. I do believe though you could make most of it back by using a bigger compressor wheel and intake housing if the boost was only dropped by 10 psi. It has been probably 20 years since I was really into turbocharging, things have come so far. I was into it when a T04 with an H3 compressor wheel was the biggest you could buy. I do know that each housing and wheel have a map they like to run in. You can make similar power with a larger wheel and compressor at lower boost, it just takes a different design.

    Mark Lelchook
    D/ED F/SA
     
  14. JustinatAce

    JustinatAce Member

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    They are keeping them around 40psi as far as I know.. You are right about a larger displacement/better designed wheel turbo being more efficient because it's not going to rip at the air as much and create as much heat. Anything boosted has issues with intake temps, like the difference between a screw blower and a roots on the charge temp.
     
  15. I/D 744P

    I/D 744P New Member

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    just cool the air and you get to put more into the cyl at the same psi:D
     
  16. JustinatAce

    JustinatAce Member

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    That's why we run methanol.. A LOT of it.. :D
     
  17. Jeremy Tanksley

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    I really don't think anything. That's why I'm asking. I'll say that it does seem odd that if (a big if) a given turbo entry that's currently competitive were capable of adding an extra 5 psi of boost, then at 15 to 20 hp (or more) per psi of boost (at peak hp rpm using methanol), that's nearly an on-demand extra 75 to 100 hp. Justin, referring to your statement about rpm, to gain that kind of on-demand extra power naturally aspirated, technology needed for something like that, on engines over 300ci, would put F1 technology into the stone ages. Drag racing cylinder heads and valvetrain are at least 10 years behind advances like that. It would be a mess. My point is, it doesn't appear that naturally aspirated cars are capable of evolving as quickly as turbo cars can.

    But hey, what do I know? Maybe NHRA knows? Perhaps pro mod boost limits are their way of saying "Oops" or something to that effect?
     
  18. JustinatAce

    JustinatAce Member

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    I think you're dead on the money.. Blower and Nitrous guys were screaming because when the Turbo cars hooked up, they were gone... 10mph over the next closest blower or nitrous car.. So they hung weight.. Well, it gets to a point where the weight becomes too cumbersome to handle. So they tried spec turbos, then everyone accuses the spec turbo company of favoritism to some racers vs. others. Now they just do boost limits, which if the cam is right, 40 psi can go a long way.

    It's the same evolution you guys fight in comp to some extent. A guy tunes his car with a laptop, vs. nozzles, main jets, etc. Is it any easier? Well keeping the fuel system happy definitely is.

    I'm surprised with all the evolution in Variable Cam Timing that it hasn't been explored more in Comp yet. I understand it's a whole different can of worms and most everyone is in over their heads financially with the motor programs they already have.. But I bring something like this to your attention...

    http://www.fordracingparts.com/parts/part_details.asp?PartKeyField=23300

    Properly tuned on the factory PCM, can probably achieve 650 horsepower on premium pump gas and one of the flatest and fattest torque curves you've ever seen using the variable cam timing. With 11:1 compression and without a blower! Imagine putting it in the hands of engine builders of the Comp world out there.

    Take the factory PCM out, which limits it to 8100RPM, and put a real crank trigger and BigStuff or Motec type controller on it and part strength is probably your only limits.

    All this out of the same N/A motor they're using in the new Stocker CobraJets.
     
  19. Justin Rosen

    Justin Rosen Member

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    Drag race engines IMO could benefit, but its unlikely, from using VCT. My motor when i shift right, stays in a 1300-1500 RPM band. VCT is only useful over a large rpm range. RPM is HP, we are always after more RPM vs making more low end torque. Street cars are another story, with VCT you get the best of both worlds, but for us there would be no reason to make good torque at 3-6000 rpm, just set it up to make power up high.
     
  20. guitar builder

    guitar builder Active Member

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    Merlin tha Majician should post on this topic

    ...there is one person i'd like to see post on this topic, are ya listenin ya know who i'm referrin to, right, love your show too!
     

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