Kenku

OK, I figure there's a bunch of people from different disciplines on here with different management schemes and so on and so forth. I've basically been building / running engines for SCCA EProd (carbureted streetport 12A or 13B with limited venturi size) with distributors with the advance locked out, with some dabbling with a peripheral port 13B with the same distributor.

So how much is being left on the table here, likely? For argument's sake, locked distributor compared to fully programmable ignition maps (MAP or TPS vs RPM, whichever) with everything else mechanically the same... if you want to pin it down more, call it a large streetport 13B with a 51 IDA, 42mm chokes, competent header (no I'm not going to quantify that) and as open of exhaust as meets noise restrictions. I'm trying to decide whether it's worth embarking on a project or not.

diabolical1

iTrader: (3)

an interesting question to which i am very much interested in seeing the answer to as well.

peejay

The main power to be had is in extending the torque curve as VE falls away at the top end.

Given how insensitive rotaries seem to be to a hair too much timing, you could probably get away with running a little extra timing when locked. Still not ideal, mind you.

(When I go with computer controlled timing, you can be sure that I WILL be doing WOT timing sweeps. Dyno time is expensive so I hope to get it done quickly )

Kenku

I'm seriously looking at building a standalone ignition controller as a project anyway; ye standard 36-1 wheel and COP with GM or whatever coils. It's probably worth it for starting, onboard DAQ and some other stuff, but more power would be nice too. Especially in the case of Prod motors at high RPM where torque is likely falling off fairly well due to the venturis.

j9fd3s

iTrader: (3)

its hard to say, really as it depends on the engine, but it is likely that with the locked distributor that WOT timing is pretty ideal, and that you're just running too much timing down low, which the engine doesn't mind much.

my experience is on an ITS car, and going from stock ecu to programable ecu, but we didn't see any more peak power, but we were able to get peak power to extend another ~500rpm, which is nice, AND we were able to pick up like 10hp in the 4000rpm range, as its a 6 port engine.

peejay

It's something that occasionally comes up when people discuss induction limited circle track engines. Some feel that the benefits of having a timing curve that comes up once past peak torque are great, others feel that it's something that can break and it's worth the risk. But this is also regarding engines that will pull a vacuum because it's 358ci pulling through a tiny 2 barrel carb, so cylinder filling is even worse than you'd expect just from VE drop-off.

I keep going back to what Mr. Hanover says about ignition timing... he recommends WAAY more timing than I have ever even thought about using. He is also talking about racing engines that spend all of their time well north of peak VE, so maybe 33 degrees is appropriate up there.

Rotary Powah

iTrader: (1)

This is something else I've wanted to know. I've got a distributor with only one magnetic pickup (wires to the trailing clipped) and a 12a with both ignitors on it. I'd like to use the single-ignitor if possible but I'm not sure that's a feasible idea. Can you fire both coils through one ignitor?

Rub20B

I would say better do not do this as it might overload the ignitor. what u could do is run 2 igniters of 1 pickup. that should work fine..

Rotary Powah

iTrader: (1)

Looking back on that post now, I worded that very wrong because i didn't fully understand what was going on. But now that i do, what I meant to ask was: I know that one pickup can trigger two ignitors in paralell (such as with dlidfis), but would the signal be strong enough to power 3 in paralell?
Then just run trailings through the distributor and effectively you have zero split. One could then also disconnect the leading pickup clip (3 connectors in paralell) from the trailing ignitor and put the trailing pickup clip back on to restore split.

Kenku

I think it should work; the magnetic pickup should just be acting as a signal and not powering anything.