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  • ka24 n/a or sr20 n/a

    I race a s13 ka24de n/a in chumpcar, There are several sr20s n/a running there and they are a lot faster than my car. How can a engine that on paper is smaller and has less hp and torque go faster.

    I am trying to make up my mind to try and make more power out of my ka or buy a sr20

    Any thoughts or sugestions ?

  • #2
    Power isn't the only thing that makes a car fast.

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    • #3
      They are most likely revving higher and geared differently.
      Originally posted by Matt93SE
      in engrish, it's all about the length of your shaft... :P

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      • #4
        The likely reason those SR20 powered cars are passing you is that they probably weigh a lot less. Switching to an SR will just be a hassle. Either you need to get a RWD SR, or put a ton of work into making a FWD SR work.

        How much does your car weigh right now? Do you have windows in the car? Our first race we didn't have lexan and the car was terrible on the straights. Now with lexan in the car our fastest driver put down the 6th fastest lap time out of 84 teams.

        Another thing is are you entering the straight at the same speed they are? If they are going a couple mph faster out of the corner they will walk away from you. There were some cars that I could pass on the straights if I got a good run out of the corner like an E36 and an SR20 powered Datsun 1600.

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        • #5
          Originally posted by KA240SX808 View Post
          Power isn't the only thing that makes a car fast.
          Yea I know total weight handling tires drver skill but when a sr engine goes past you down the straight well????

          Are you sugesting sr power isnt faster than ka power?

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          • #6
            An na sr20 that's not built to the hilt will have a hard time pulling off a corner faster than a ka due to.the lower torque and displacement. If the car is lighter then its a different story.

            Even then, corner exit speed is everything in racing. Even if you're 2 cars ahead coming out of a corner but the other guy has 5mph on you, he'll beat you to the next turn.

            I can pull spec miatas on the straights all day long in my s14 ka, but I can never seem to get a good enough run off a corner to get to them by the next braking zone.
            Originally posted by SoSideways
            I don't care what color they are as long as they are LONG AND HARD.
            '04 G35 Sedan 6MT- The DD
            '96 240SX- The Track Toy

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            • #7
              Originally posted by knate View Post
              The likely reason those SR20 powered cars are passing you is that they probably weigh a lot less. Switching to an SR will just be a hassle. Either you need to get a RWD SR, or put a ton of work into making a FWD SR work.

              How much does your car weigh right now? Do you have windows in the car? Our first race we didn't have lexan and the car was terrible on the straights. Now with lexan in the car our fastest driver put down the 6th fastest lap time out of 84 teams.

              Another thing is are you entering the straight at the same speed they are? If they are going a couple mph faster out of the corner they will walk away from you. There were some cars that I could pass on the straights if I got a good run out of the corner like an E36 and an SR20 powered Datsun 1600.
              Hay Nate

              I have the other 240 the 38 car..I am not sure how much the car weighs. I dont know how to make it any lighter. I have lexan windows. I know you were quite a bit faster than us.

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              • #8
                If you can provide us specs of the motors n cars we can tell you why. Chances are he's revving about 1500rpm higher then you making most of his power up top. Like stated earlier the N/A SR's have slightly different transfer gears. If the Final Drive is shorter then yours that gives them even more an advantage on the straight. Also IIRC a N/A SR is some 20+lbs lighter correct?

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                • #9
                  Originally posted by joefish View Post
                  Hay Nate

                  I have the other 240 the 38 car..I am not sure how much the car weighs. I dont know how to make it any lighter. I have lexan windows. I know you were quite a bit faster than us.
                  Is this Jonathan? Those fwd SR20 cars can get down to probably 200-300 lbs less than a 240. Besides aero we also changed up suspension this time and had stiffer springs and shocks. Last time we had blown shocks which didn't help driver confidence or traction. I think our tires really play a big role in our car being faster. Well, that and the Feigions, they were both running great lap times.

                  In April you guys had a best lap time of 1:40.7, this time a 1:43.6. Was the headgasket maybe slowing the car down before it blew? I would definitely try some Star Specs before you start thinking engine swap.. Also, what is your front camber at? Watching your videos from April it looks like the car has a decent amount of understeer. We chopped our LCAs and lengthened them ~1/2" to gain some negative camber and it seems to work pretty well.

                  Getting a good run on the straight is everything. Looking at datalogs of Nathan Feigion compared to my runs, just taking turn 7 a little differently makes a massive difference on the back straight. I uploaded a video of one of his faster laps (1:38, left) versus my fastest (1:40, right) to show how much driver can make up with the exact same car. Also, I find it really helpful to video what the driver is doing.

                  http://www.youtube.com/watch?v=OW2TsVrFW3A
                  Last edited by knate; 11-18-2011, 11:45 PM.

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                  • #10
                    Hay Nate

                    I am Joe Jonathans dad. I think you have really good points. I know corner exit speed = strightaway speed,,grippy tires help that,,good driving puts it all together. May be the head gasket was slowing us down till it gave up.

                    I think our camber is somewere around 2 neg the allignment guy slottted holes to get that. I agree about the car pushing I have been thinking of moving the engine back to get a better ballance, Then there is my springs cut stock and the shocks are old and wore out.

                    So looks like I have plenty to do before I go looking for a different engine, That is a gerat way of side by side in car video,

                    Thanks for all the replys.

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                    • #11
                      Good luck with the car, we'll see you out there in March!

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                      • #12
                        Don't forget that a FWD car will make about 3-5% more power to the wheels with the same power at the crank. FWD SR guys just think they have "magical" JWT tunes to put down more power than RWD guys with the same turbo/boost/cams etc... hah

                        Another thing is an S13 is a bigger car than something like a B13, so your aero drag is going to be higher even though the S13 has a slightly lower Cd (i.e. your CdA is higher). So on a higher speed straight you could be making a hair more power than the B13, but he's got you on weight and on aero drag so he'll seem to slowly sail by you.
                        '18 Chevrolet Volt - Electric fun hatch for DD duty!


                        DefSport Koni Sleeve and Spring Perch Buy!!!
                        http://www.nissanroadracing.com/showthread.php?t=5902

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                        • #13
                          An SR20DE with mild cams (JWT S3) on track sucked. I think everything Def threw out there is about right with one addition being the gearing, they just never seemed right NA.
                          -Monty

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                          • #14
                            Don't mean to thread jack, but I always wondered what's AIV on S13's?

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                            • #15
                              Air Injection Valve. Injects Fresh Air into the Exhaust for emissions purposes.

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