Also noticed that automatic transmission engines have more retard specified. I notice too, that there is some difference in the distributor advance curves for California models. Since the Bentley specs include different timings for California cars, it must be that pollution control standards had a hand to play. Right now, i have my engine set at 8 degrees BTDC, and that gives me much better acceleration response than 2, and interestingly, the engine at idle seems to run a little more comfortably than if I advanced to around 12. I have tried the factory spec of 2 degrees BTDC, but the engine is very noticably flat, especially in higher gear. I have an aftermarket carb setup on my carb. Actually, timing spec for my car is missing, so there should be 13 specs. There are 12 timing specs for idle timing as given in the Bentley manual chapter 5 page 87. Specified timing is 2 degrees BTDC, + or - 1 degree.Ħ degrees BTDC for 83 and 84 FI with manual trans ģ degrees ATDC for 1983 cars with auto trans What puzzles me me is the range of static advance ranges specified for the MK1 engines.įor example, my 84 rabbit was an OE carburetor. Since I have removed the vacuum advance mechanism, my distributor only uses the mechanical centrifugal advance, and thus I do not worry about the initial timing at 800 to 1000 RPMs as the engine does not idle smoothly due to compression and camshaft. On the race Wabbit, I set the total ignition advance to about 34 to 36 degrees at about 4000 RPMs with an adjustable electronic timing light, such as the Sears unit. Each distributor will have a timing advance curve that increases with engine RPMs. ![]() Once the RPMs become greater than about 3500, then the mechanical centrifugal advance takes over to give the total ignition timing advance.įor a non-crossflow engine, the maximum total timing advance is about 34 to 36 degrees at WOT.Īs expected, the total timing advance does not occur instantaneously. Since the engine vacuum is highest at low RPMs, the vacuum advance occurs at initial and partial throttle settings. However your distributor may use vacuum advance and vacuum retard in addition to the mechanical centrifugal advance. The ignition distributor typically uses both vacuum advance and mechanical centrifugal advance to achieve total timing advance. For example, you set the initial timing to 12 degrees BTDC and the mechanical advance timing enables another 24 degrees, then the total timing advance would be 36 degrees at typically WOT. Total ignition timing advance is comprised of the initial timing and mechanical advance timing. This is wasted energy, unburned fuel, high emissions, and lost power. If the spark occurs too late, the ignition of your fuel mixture occurs after the piston is traveling back down the cylinder. This causes detonation, lost power, much higher combustion temperatures, backfires out the carburetor, and early internal engine part failures. If the ignition spark occurs too soon, it can actually push against a piston traveling up the cylinder as it is compressing the fuel/air mixture. Ignition timing is controlled by the relationship of the position of the piston to when the spark occurs. Re: Q: How to set the best timing for performance (BFDeihl) I'm expecting 50-70 times perhaps in the 2 second range. Once I get my Lysholm Cabby intake manifold I will be using this method before and after as well (prior to taking it to the dyno). I found 6% gain in the 3000-4500 rpm range with this method. I would typically do 4 runs total (2 each way) and average. Do it the same way the other way and average results. The moment you floor it start the stop watch. ![]() coast at around 35 steady in 3rd.stop watch at the ready. The way I used to do this (before and after adding a part back in 1992 or so). In a sense this can be a more accurate way of figuring out what advance works best. as you are basically using the cars inertial mass as a sort of dyno to put load on the motor. I'm used to hitting the knock limit before running out of possible advance but on your low compression JH you might not have that kind of problem! Count yourself blessed.Įither way you will need to run the intervals to determine best wide open throttle advance. start at 6btdc initial and advance in 2 degree increments. I would suggest running the intervals to see what the motor likes. Re: Q: How to set the best timing for performance (chickenfriend)
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