John L Posted July 11, 2017 Report Share Posted July 11, 2017 I was interested to see what my car CP PI was capable of, as I have no idea of the engine build, or state, so took the plunge and had a run, so now there are some questions to how to improve/correct it further. I see my overall power is a bit lower than others I saw tested, but I have no idea how long ago the engine was rebuilt or whether it has been rebuilt. The part I'm most interested in, is improving is the lower end AFR, and why it dips as much as it does, it did have an effect on the power and the Torque curve. I cannot confirm what camshaft is fitted, this I think will be a job for this next winter. The vacuum at present is just a little over 10"Hg. at idle. Can anybody tell which rings I should adjust or which internal springs should be changed, at present I have the silver pair as advised by Neil F. I would be interested if others who had runs would share their results as well please? Quote Link to post Share on other sites
Bill944T Posted July 11, 2017 Report Share Posted July 11, 2017 If I've read it correctly, the graphs suggest that the engine was run to 6000 rev/min. Is that appropriate for the engine? Regards Bill Quote Link to post Share on other sites
Tim D. Posted July 12, 2017 Report Share Posted July 12, 2017 Although the AFR looks a little wavy at low revs I'd say it wasn't to bad and bare in mind that snap opening the throttle to start the run will lead to a transient lean mixture. The PI system doesn't have an accelerator pump mechanism like many cards. Cheers Tim Quote Link to post Share on other sites
John L Posted July 13, 2017 Author Report Share Posted July 13, 2017 Anybody got a graph to compare with mine, just really out of general interest. Is my engine in the std ball park? @ Tom D, mine is showing a very rich spike at 2300/2400 which was killing the torque and power curve This is also the speed usually being used in driving so leaning this off a bit I think would also help. I need to do some tests with a vacuum gauge to see what is actually happening at that speed. I do have a much higher vacuum that the std for the CP engine. I need to change the springs in the vacuum unit and see what happens then. John Quote Link to post Share on other sites
stephen cooper Posted July 13, 2017 Report Share Posted July 13, 2017 (edited) Hi John, You would be best off using a rolling road where the operator can also tune your engine to get the best out of it. What correction factor was the RR using? No wheel power figures? I see they did it in 3rd gear which would give you a higher wheel power figure than 4th. Too many variables with rolling roads to make any assumptions other than with cars that were on the same rollers and the same day if no correction factor used to to negate on the day conditions. It may be rich there or alternatively could something else be going on in your engine where it's not as efficient at that rpm and subsequently makes it rich? Edited July 13, 2017 by stephen cooper Quote Link to post Share on other sites
Peter Cobbold Posted July 13, 2017 Report Share Posted July 13, 2017 (edited) Anybody got a graph to compare with mine, just really out of general interest. Is my engine in the std ball park? @ Tom D, mine is showing a very rich spike at 2300/2400 which was killing the torque and power curve This is also the speed usually being used in driving so leaning this off a bit I think would also help. I need to do some tests with a vacuum gauge to see what is actually happening at that speed. I do have a much higher vacuum that the std for the CP engine. I need to change the springs in the vacuum unit and see what happens then. John I doubt AFR12 would kill power, 12-13 is pretty much ideal for power. Spark timing could cause that power dip. I'd leave the MU alone and focus on sparks, eg strobe the centrifugal advance. Peter Edited July 13, 2017 by Peter Cobbold Quote Link to post Share on other sites
John L Posted July 13, 2017 Author Report Share Posted July 13, 2017 Thanks Peter, I wish in hind site now that they should have recorded vacuum and spark advance, that would have covered all eventualities, what is the best real AFR ratio for these 6 cylinder engines? John Quote Link to post Share on other sites
Peter Cobbold Posted July 13, 2017 Report Share Posted July 13, 2017 John, Its around 12 -13 for max torque on most si engines.This richness makes best use of the air.Its to do with combustion not detailed engine design. You can easily check the centrifugal advance in the garage with a strobe light, with a helper running up the rpm. BUT keep your hands/sleeves away from the fan ! Post 26 gives the curves: http://www.tr-register.co.uk/forums/index.php?/topic/24915-tr6-ignition-timing/page-2 Peter Quote Link to post Share on other sites
GT6M Posted July 14, 2017 Report Share Posted July 14, 2017 The PI system doesn't have an accelerator pump mechanism like many cards. said it befoer, It has, but folk just cant grasp where its at its no rocket science, if looked at logically,!!! M Quote Link to post Share on other sites
Peter Cobbold Posted July 14, 2017 Report Share Posted July 14, 2017 The PI system doesn't have an accelerator pump mechanism like many cards. said it befoer, It has, but folk just cant grasp where its at its no rocket science, if looked at logically,!!! M Marcus, I do look at it logically and there is no 'acceleration charge'. I explained it here: https://supertrarged.wordpress.com/2013/06/12/the-lucas-pi-lean-spike/ Where do you think transient enrichment happens upon suddenly flooring the throttle? Peter Quote Link to post Share on other sites
BlueTR3A-5EKT Posted July 15, 2017 Report Share Posted July 15, 2017 (edited) - deletedPeter W Edited July 15, 2017 by BlueTR3A-5EKT Quote Link to post Share on other sites
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