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Torque or rpm and gearing

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  • Torque or rpm and gearing

    I'm trying to find what most 4-cylinder track car drivers are after. I'm building a 2.0 3SGE Redtop Single VVTI Toyota. Easy engine for an old Celica.
    So here's the debate. The valve train I have will handle 9000rpm. The cams will be ground based on what target rpm I choose. I can go stroker engine
    That will allow the engine to rotate 8300rpm and make good torque while displacing 2.2 liters. Or I can go a 2-liter long rod engine, spin to 9000rpm and make up lost acceleration by gearing t shorter. I want opinions of what you perefer and a reason why please. I'm not saying rpm or torque is better than the other, I just want to hear real world experiences.

  • #2
    Short gears and 9k sounds delightful to me.

    If your looking for more objective critique it’s tough to say with that info. I’m not sure how long or short the factory gearing is in a celica and gearing is generally track dependent. The other thing I value is reliability. So if you go long rod and think it can spin 9k safely cool. But if your stressing the motor at 9k but the motor is happy at 8300 with a little more torque I might favor that. Sounds interesting though. Post up some more info on the build as it comes together...


    • #3
      I'm just asking a general favorite really. The Celica is a 1987 RWD, the beams are rev happy and make just as much power as their turbo brother, by all engine. I will definitely post pictures and the such for the build. It's going to be an 8-month long build lol


      • #4
        I'd look at the s2000 for an example. It came in 2.0L and 2.2L with a longer stroke and lower rpm limit. The area under the curve even with close ratios seems to be superior with the greater displacement.

        From what I've read, the sbc is the same deal. You can do a short stroke and spin it faster, but generally you'll do much better with more displacement from the longer stroke.


        • #5
          I believe engines tend to last quite a bit longer with relatively small increments of RPM limits. Not sure what exact lifespan changes would be for your application.
          1991 Miata - Trogdor SuperMiata
          2011 Ram 2500 - all the torque


          • #6
            We always build for lower rpm power when possible within class rules. Lower RPM means less heat loss through friction, which means better BSFC (fuel economy) and lower operating temps, less wear. A cooler running engine requires smaller rad openings which improves aero lift to drag ratio.
            Primary target should be the broadest possible powerband, regardless of the RPM range. The more time you spend near peak hp on a given lap, the faster you go. That could be a 2000rpm powerband with gearing that allows 1200-1500rpm drops or a 4000rpm powerband with gearing that has 1800-2500rpm drops. Same speed.
            Now if you have a 4000rpm powerband and gearing that allows 1200-1500 rpm drops you encounter a situation where the driver legitimately has their choice of two gear ratios for most parts of the track with no difference in lap times. With a sequential, this is largely moot. With an H pattern box though, eliminating a few shifts per lap can make the difference between getting a run on another car in w2w or a few tenths during qual or TT laps.

            In general, our race cars always favor wide powerbands when the rules allow. Sometimes matched with close gears, again when the rules allow. Our PTE cars from a few years back made 95% of peak power from 4400 to 8500rpm with 1100-1600rpm drops between gears. Some tracks could be driven in one gear. We even had an average acceleration advantage over cars with greater power to weight ratios than us. Sanctioning body and other teams couldn't figure it out. They put their data aq system in our car thinking we had illegal horsepower. What they found was that we always made our class power cap everywhere on track, never falling below at any point on track.
            The rules were then re-written to keep teams from building engines like ours, having an "average power" cap instead of peak power.

            In Supermiata S2, we have a 140whp cap, 7000rpm rev limit, average power area cap and only one gearing option. I tuned my engine to make a bit less power near redline, shifting that power lower down. That allowed my car to exit the turns harder when off the relatively narrow powerband and get a run on other cars tuned to make peak power at redline. Once in front, it's easier to block someone in the braking zone. So highest peak power at redline doesn't always win races. w2w is all about track position, not always about pure speed.
            Last edited by emilio700; 06-08-2018, 09:58 AM.

            Aside from their cost I never understood why people race them.
            But obviously I just dont get it. -fatbillybob


            • #7
              Originally posted by emilio700 View Post
              We always build for...snip
              It is cool to read about what winners do to win. It makes lazy racers like me, who will never do more than show up and run what I have brung, feel a little better about where I am on the grid. Racing at the front of the grid is hard work.


              • #8
                So i spoke with my engine builder and I did a general dyno search. So far since on 3S based engines, the stroker 2.3 have been more powerful through almost all dynos some are even spinning the 2.3 to over 9K, which is too high for comfort with me on a 1.48:1 rod ratio. One dyno i looked at a Customer had a 2.3 3SGTE with a GT3071 single scroll turbo, making 200FTLB by 3200 RPM and over 350FTLB by 4K. Thats a great street engine! Also it would be a beast on the track as its reving to 8200. The gearbox being used is from an altezza, good close gears. So far I am leaning towards build a short rod 8300RPM engine as its also going to get driven on the street, and when the turbo finally finds its place in the build the displacement will only aid in spooling it up. i have differential gearing options of 3.58:1 all the way to 4.88:1. keep some responses coming as what YOU prefer and why. I love hearing what works and why. Some like torque and tires spinning, others like screaming engines and top speed.