John McCormack Posted September 12, 2019 Report Share Posted September 12, 2019 I apply a self imposed rev limit of about 4,500 on my stock 1970 PI. It is a 50 year old engine and in today's traffic I get plenty of performance at that limit. I just went out for a run and took her to just over 4,500 in 2nd and then changed up. It felt like it would have liked to go harder but I don't want to stress it. What do other owners rev their engines too? Quote Link to post Share on other sites
Tim D. Posted September 12, 2019 Report Share Posted September 12, 2019 Generally keep below 5 although I know it will go over. But then with the supercharger the fun is from the low down grunt and Not the top end. Tim Quote Link to post Share on other sites
matt george Posted September 12, 2019 Report Share Posted September 12, 2019 (edited) I generally limit myself to 5.5k as per the factory rev counter, but if you keep your foot in, it will pass 6k. Has a 6-2-1 exhaust manifold and Phoenix straight through system and it sounds great when working hard. However that is on an engine that had all the rotating internals balanced as part of the rebuild process. My 2500 saloon feels much less smooth when you get to 5.5k, put it that way. Matt Edited September 12, 2019 by matt george Quote Link to post Share on other sites
john.r.davies Posted September 12, 2019 Report Share Posted September 12, 2019 It's a convention of engine design that the mean piston speed should not exceed 20 meters/sec unless exotic materials or special preparations are used. This value is a surrogate for the piston acceleration, which is a much more complex calculation. The mean piston speed of the two engines at 6000rpm may be calculated, EG: At 6000rpm, the piston travels from top to bottom of the bore in half a revolution: Duration of stroke = 60/6000 x 2seconds = 0.005 seconds For the 2L engine, mean speed of piston = stroke disance/stroke duration (in seconds) = 76/0.005 =15200mm/s =15.2m/s 2L, 76mm stroke RPM Mean speed in meters/sec 6000 15.2 7000 17.7 7500 19.0 2.5L, 95mm stroke 6000 19.0 6500 20.84 Thus it becoms obvious why the 2.5L engine becomes unreliable at a speed at least 1000rpm lower than the 2L. John Quote Link to post Share on other sites
Nigel Triumph Posted September 12, 2019 Report Share Posted September 12, 2019 I rarely take my TR6 past 5,000rpm. If I go past 5k it's only very briefly and the rev limited on my electronic ignition is set at 5.5k. In reality a well set up PI engine delivers so much torque from below 2,000rpm, there's no need to take it to the limit on the road. Nigel Quote Link to post Share on other sites
John McCormack Posted September 12, 2019 Author Report Share Posted September 12, 2019 My 4,500 limit is conservative then. That is good but I might nudge it a bit higher on occasion. Quote Link to post Share on other sites
JochemsTR Posted September 13, 2019 Report Share Posted September 13, 2019 These engines are very robust. Currently I have a Rev Limiter at 6.100. 280 cam and C.R around 9.6. Engine #2 will go upto 7.000. However, this all depends on driving behavior and engine config. I prefer Rev, others keep it low.....so what. Jochem Quote Link to post Share on other sites
Peter Cobbold Posted September 14, 2019 Report Share Posted September 14, 2019 On 9/12/2019 at 7:39 AM, Tim D. said: Generally keep below 5 although I know it will go over. But then with the supercharger the fun is from the low down grunt and Not the top end. Tim Yes, and no need to wait for the rpm to cllimb...drive the torque. I get 6 psi boost at 2800 rpm and approx 100 bhp at the flywheel, so hardly ever exceed 4000 rpm ( and ca 8psi). Peter Quote Link to post Share on other sites
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