So does wiring the SAFC to the pressure sensor help to solve this problem since it reads boost in the form of voltage off the pressure sensor and then eventually learns max boost?

 

That would simply mean your low/high throttle points were set too high. You could make exacly the same mistake with the TPS input connected to the MAP sensor.

IMO the weakness of the S-AFC is not that it's too simple, it's that it's so much simpler than a full EMS that many people think they don't need professional advice or tuning to set one up.

Terrh, that's just a general comment, not aimed at you personally. Unless you think it should be...

 

But if it's on the pressure sensor, the S-AFC will directly know the boost pressure. So it's user error if the "TPS" points are not set properly.

Problem with the S4 is the 1/4 range TPS. Can make setting up the S-AFC...interesting.

 

Exactly, and I don't think many people fully understand how that affects their high and low "throttle" settings. The TPS and MAP sensors both have a 0-5V output (approximately), with the MAP sensor's output corresponding to about -1atm to +1atm. So instead of 0% meaning no load (closed throttle) and 100% meaning full load (WOT), you get a zero-load reading of ~20% at idle (~16inHg) and a full-load reading that depends on your max boost (~80% at 10psi). You need to adjust the high and low throttle settings to take that into account. It's not difficult to work out, it's just not immediately obvious.

Personally on a turbo I'd set the high-throttle setting at 50% (i.e. 0 psig, when boost begins). The low-throttle setting would depend on how fast your turbo spools, but I think about 40% would be about right.

Not really. Remember that the ECU already changes fuelling according to load as well as rpm; the S-AFC's throttle settings just give you a bit more tuning scope in that area. If you tune your high-throttle settings at full load (as you should), the worst that will happen is that you'll be a bit richer than necessary at smaller throttle openings that are still using the high-throttle map (i.e. over ~25% throttle). During normal cruising you'll still be under that point. A full-range TPS would be nice, but I don't think it's essential.

 

My car was set up with the TPS.

I had low set at 98% and high set at 99%, in practice, anything over ~15% throttle was in the high throttle map...

I think it happened at EXACTLY the 3800RPM changeover, but I'm still not sure what happened.
it's definatly blown though, you can see it in the boost/vacuum gauge.

I managed to limp it home (250KM!) only cost $60 on gas... hopefully the turbo survived without damage, I haven't pulled it off yet.


How can I prevent this from happening a third time? Obviously dyno time, but will dyno time be able to fix something that happened at part throttle?

Where should I set my timing to for the new motor?
I'm probably getting an s5 jspec, maybe an s4... whatever I can get the best deal on, because I'm out of money Going to get a payday advance JUST to get this motor, so obviously I can't afford another incident.

 

NZ: Good point.

Terrh: Timing should be stock. To prevent this is a little trickier. First step is to reference the TPS from the pressure sensor, and properly dyno tune it...But you know what I'm going to say with regards to the "final" solution....standalone.

 

For the price of a few blown engines, you can almost buy one of those useless EMS thingies

There's a real standalone EMS revolution going in with all the RX-7's Ottawa. Bout time.

 

eViLRotor: I dunno about that.. this engine was basically free (they practically paid me to take it away, $150 for it + the whole smashed TII it was in)

The last engine wouldn't have went if not for #@$)(* boost creep... I thought that going to an s5 turbo would cure that but obvioulsy not.. next motor gets a ported wastegate s5 turbo with a boost controller set at ~11psi

 

Its all good man
Just keep that baby running

Maybe if we show you a few well running EMS cars, you might consider it some day

 

I would LOVE an EMS..

the problem, as always, is that I work my *** off and am always broke anyways

 

Did the motor that just blew have a ported wastegate?

 

no, stock s5 wastegate

 

what fuel pump were you running?

 

FD pump/720 secondaries

 

Given the size of the pump and secondary injectors, and the OTT settings on the S-AFC, I don't think top-end fuelling is a problem. But you said it happened right at the secondary injector transition which may mean your primary injectors ran out of flow, or you got caught out by the brief lean condition you get at the transition when using mis-matched injectors with an S-AFC. You said you had +8% correction, but was that at all rpm/load points or just up top? What were the rest of the settings?

 

Why would you boost on an untuned motor with mods?

 

I agree that top end fueling definitely was not a problem, if anything at only 11 pounds on the stock turbo it should be retardedly rich. I personally think it makes a lot more sense to run a pair of 720cc primaries and keep the stock 550's in the secondaries for moderate mod's on the stock turbo.

 

Isnt the problem with 720s in the primary with an SAFC2 that they cannot be controlled during cranking and will probably cause lots of flooding.

 

I don't know how that myth got started. I've been running 4 x 720's now for nearly a year. First on the safc and now on the e-manage. I've never had flooding problems.