Barwick

So, since (I think) the only thing the stock ECU does when it sees boost is retard the timing (the airflow is measured by the AFM regardless of boost), wouldn't it make sense to...

Rather than buying an FCD, completely disconnect the stock pressure sensor (I've run a TurboII without it before unknowingly and it didn't blow up in the 220 mile trip), and...

Have an external box retard timing (anywhere from 1 to 3 (or even 4) degrees) for each pound of boost it sees.

Anyone done this, and wouldn't it basically do the same thing (since the stock "driver entertainment" gauge sucks, and with an FCD is useless anyhow), and what would this change? I can handle the extra fuel with either an S-AFC or a reprogrammed ECU. It seems this would offer a cheaper alternative (about $400 and no massive tuning necessary) to a full standalone.

gsracer

Henrik is working on a stage 1.5 ecu that would retard boost a certain degree/pound of boost past fuel cut.

gsracer

double post

Scott 89t2

problem is retarding both leading and trailling. you'd need 3 boxes.

dag

No, you'd just need one box with three outputs.

-David Guy

RETed

There no such beast that I know of.
One of the problems is that the firing sequence is not sequential and evenly spaced - this makes most of the multi-channel CDI boxes barf.

If there was such a thing that's basically a "dumb" 3 (or more) channel CDI box, then it'll work.  It's basically 3 CDI boxes in one chassis.

As for the retard thing, I think people are getting paranoid.  The stock ECU already does retard versus boost pressure, and retarding it even more is...retarded.  Unless you're working with an NA that can't do it by itself, a retard box on top of the stock retard function in the stock ECU is overkill.  I can imagine this would be a band-aid fix for bad tuning.  Have you ever tried messing with any of the boost-dependent MSD devices (i.e. 6BTM)?  It's VERY sensitive to how much you adjust the ****, and too much retard kills power.

The stock ignition timing maps are very conservative, and we run much more aggressive numbers with our Haltech tuning with no broken engines.  Stop trying to blame ignition timing for your problems and fix the actual problems first.  Unless we're talking about circumstances out of your control (i.e. bad gas), you're just suppressing power on the engine with excessive ignition retard.


-Ted

Barwick

No dude, I'm talking if you completely disable the stock ECU pressure input (so it retards timing not at all) and let an external box handle your timing retard and advance by pressure.

I'm trying to avoid blowing my engine up by the ECU not retarding timing above 8 lbs boost because of the FCD.

Barwick

bumP

incendui

I was wondering that too. How much does the stock ecu retard the ignition at 8lbs, and at what pressure is it not retarded enough?

It seems control over ignition is the largest reason people go to standalones, a cheaper fix would be nice.

Also, couldn't one box control it if you were running no split between trailing and leading (not sure what kind of wiring hack would be needed for it to run this way on a stock ecu...)?

Barwick

I dunno if it would work, I don't understand enough about the technicals of the ignition system on a rotary to say if you could run them at the same time or not... I don't think you can run them at the same time, there's a reason they run one a few degrees before the other one.

And plus I think the trailing plug fires twice as often as the leading plug because I think it fires halfway through the combustion cycle as a "waste spark" and plus it maybe possibly burns some other air/fuel mixture left over that somehow isn't being ignited by the massively hot combustion already taking place.

RETed

So, you're trying to trick the stock ECU then?
Why not just get a stand-alone EMS to have full control over the ignition timing instead of trying to trick the ECU?



-Ted

Barwick

Because a standalone is close to a grand whereas an S-AFC used is like $125 and an ignition retard box if I remember correctly are like $200 new.

That's $325 for basic timing control and injector control, and you don't have to worry about running 25 lbs boost with an FCD on the stock ECU and having the engine detonate because the timing wasn't retarded properly at that high boost level.

The stock ECU wouldn't do any timing retard or advance based on boost/vacuum.

My only concern is, I don't know how those boxes work and if it's possible to simply run the ignition all through one box and retard them all the same amount of degrees based on boost.

RETed

An MSD 6BTM used to cost over $300 new.
Most of the more expensive CDI boxes have external boost retard add-on's but it's not cheap.

In fact, doing a search for "boost" and "retard" on the Summit Racing site comes up with 4 hits.
Holley Performance Products, Inc.
HLY-91070 Electronic Boost Retard $324.69
MSD Ignition
MSD-6562 Boost Retard Control Multi-Channel for DIS Applications $396.39
MSD-7535 Ignition Box, Digital 7 Programmable, Digital CD, w/ Boost Retard Curve, Gold $699.95
MSD-8977 For use with MSD 6, 7, or 10 series ignitions, aluminum, anodized red, with boost retard, ignition controller $419.95


I dunno what cheaper boost retard boxes you're talking about?
Can you give a reference to them?


-Ted

Barwick

then apparently I was mis-remembering-correctly.

Would they work with a rotary like normal?