AJP Ignition map, one for Joolz I think
Discussion
Some years ago I migrated off the Emerald to a newer system with twin wideband support. After wrestling with the odd firing intervals (which was a pig to deal with) I finally got it all running well but was more than a little surprised by the advance map in the old Emerald. It was 32 degrees at full throttle circa 4k RPM and pushing 36 degrees by 7500. This is a lot more advance than I have ever seen on any other engine, especially one as good at filling the cylinders as an AJP. Today I spoke to another mapper who will remain nameless as he was telling me stuff that I don't think is public domain and he also indicated that the figures seem at bit high at the top end of the RPM range. More typically the advance is all in by 4k RPM and tends not to increase much above that.
The AJP turbo we built many years ago was certainly not in need of any more advance beyond 3k, even off boost and by 1bar we we were pulling out 10 degrees, which is pretty typical for a boosted engine and suggests that the AJP is not atypical in its advance needs.
Now to the point.. Does anyone have an ignition map for a typical AJP so I can compare notes/sanity check mine. I begin to wonder of the figures I saw on the Emerald had an offset built in and I have never had mine on a dyno to verify things.
The AJP turbo we built many years ago was certainly not in need of any more advance beyond 3k, even off boost and by 1bar we we were pulling out 10 degrees, which is pretty typical for a boosted engine and suggests that the AJP is not atypical in its advance needs.
Now to the point.. Does anyone have an ignition map for a typical AJP so I can compare notes/sanity check mine. I begin to wonder of the figures I saw on the Emerald had an offset built in and I have never had mine on a dyno to verify things.
I think the thing with the ajp is maybe that piston protrusion slowing the flame path ? certainly the figures you had in the emerald map are very typical of what i get when mapping anyway...
I know we don't have any fancy in-cylinder pressure monitoring like a manufacturer would use, but I map to give the engine what it seems to want, rather than what a pre-conceived idea might lead you to think it might want. Experience, watching the power out as you creep up on the timing map, plus det cans
and watching the exhaust for tell tale puffs of black smoke is all 99 percent of the aftermarket uses when creating their ignition maps on the rollers.
I know we don't have any fancy in-cylinder pressure monitoring like a manufacturer would use, but I map to give the engine what it seems to want, rather than what a pre-conceived idea might lead you to think it might want. Experience, watching the power out as you creep up on the timing map, plus det cans
and watching the exhaust for tell tale puffs of black smoke is all 99 percent of the aftermarket uses when creating their ignition maps on the rollers.
Edited by spitfire4v8 on Wednesday 1st September 12:26
Thanks Joolz, helpful.
I would be willing to bet TVR didn't have any fancy cylinder pressure measuring gear. They were never noted for the scientific approach. I take your point on squish. The standard engine has plenty and my turbo one had none, the pistons were some mm down the bores at TDC so it would be less tolerant of advance. I will tweak in a couple more degrees at the top of the table and make some nice det cans, then try to find a place to bolt them on, a weekend project to get my teeth into. I've got a TR6 that is easily provoked into detonation so that can be the testbed for the cans.
I would be willing to bet TVR didn't have any fancy cylinder pressure measuring gear. They were never noted for the scientific approach. I take your point on squish. The standard engine has plenty and my turbo one had none, the pistons were some mm down the bores at TDC so it would be less tolerant of advance. I will tweak in a couple more degrees at the top of the table and make some nice det cans, then try to find a place to bolt them on, a weekend project to get my teeth into. I've got a TR6 that is easily provoked into detonation so that can be the testbed for the cans.
Can you plug headphones into that unit? I would trust it more if I can also hear what it hears. I've tried a few knock sensors in the past which got triggered by all kinds of noise and others that wouldn't care if you walloped the block with a hammer. I think the human ear adds something to the reliability.
Where are the best places for the sensors on an AJP. I'm thinking the the two webs where the alternator bolts on. They seem to be a solid chunk of metal in the block casting.
Where are the best places for the sensors on an AJP. I'm thinking the the two webs where the alternator bolts on. They seem to be a solid chunk of metal in the block casting.
Yes Ive got a visual display and headphones which also plug into the system .. and yes the alternator bolts are perfect but I've even seen videos where people have gone onto the sump casing bolts on some engines ... I'm sure that closer to the top of the block is preferable but it doesn't seem to matter too much where you bolt as long as you're filtering the correct frequency range ?
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