AGreen

iTrader: (11)

I recently went back to a completely stock TII throttle body. The one I had before had the secondary butterflies removed and was heavily ported. I was having issues with fuel mileage because any small change in movement in throttle resulted in a large rush of air, which required heavy soaking down of the accel enrichments. I know... weird how someone with a standalone is tuning for both power and fuel economy at the same time. I didn't even notice a change in power after installing the stock unit, and fuel economy improved drastically

Anyways, the point is that now I'm faced with an interesting scenario. On cold starts, the thermowax is designed to completely block vacuum to the secondary plates, keeping them fully shut until warmed up. So even though the secondary throttle plates are shut, the engine is still fully capable of seeing the same manifold vacuum/pressure as when they're open. It just won't flow as much air. The warmup enrichments and accel enrichments are spot on, as well as the cold start acccel multiplier. The only problem is that if I have to make a quick move when the engine is cold, it bogs down REALLY bad because it's not getting as much airflow as when those plates are able to fully open. Everything's great up until about 0 inHg. It accelerates just fine, cruises perfect, etc. It's only when I get into a hairy situation while trying to drive somewhere before the car is fully warmed up that it really lets me down.

Keep in mind, I don't try to thrash the engine when cold or anything, I just know it doesn't do that when stock. It just drops the engine's power, which is completely fine with me, I just don't want it bogging down so bad that it makes the situation worse. And please don't answer with "remove the secondary butterflies" or "let the car warm up fully before driving it".

Hard to explain in words, but I think I got the point across. So does anyone know how to tune that out?

00020B

I don't have much experience with the ecu you are using but I can tell you when using Motec I needed to have the idle control valve 'pickup' the rpm on cold start when the revs dropped to keep it alive. You can do this closed loop or open loop if you play around with it a bit.

AGreen

iTrader: (11)

It's not the cold idle or anything, it's more of a "more than light throttle" issue. I can putt around and idle just fine, it's just when I need a to go, as in coming to a busy intersection without a red light and I need to get out in the road or get run over and the engine's still cold is when it's really bogging down. It's because the engine can get to that part of the fuel map where it's tuned for the secondary butterflies to be open (but they're still shut at this point) that it soaks it down with fuel and all I see on my wideband is 9.00 (lowest it reads).

Also, how can you determine % duty cycle? I now have a T04B hybrid with 550/720s and I would like to know if I'm going too high in the injector duty cycle.

Aaron Cake

iTrader: (1)

What version of the MS? Some of them (MS2 and MS3) have temperature modifiers to the accel enrichments, which I would assume would take a negative value so you could trim fuel when the tertiary throttles are still closed.

That said, I can't honestly say I've ever noticed a difference in MPG on a properly tuned 'Squirt with the tertiary throttles or without them.

One thing you may want to consider is removing the thermovalve to the tertiary throttles. That way they operate cold or hot, and you can use the coolant engine limiting features (I can't remember the name of them right now) to limit RPM/boost when cold.

For that matter, lose the entire cold start cam and thermowax system because under MegaSquirt control, the BAC valve can perform the same function (no idea why Mazda didn't just use the BAC in the first place). And same with the dashpot. Make it gone and use the dashpot function in Idle Control.

As for injector duty, just right click on one of the gauges in TunerStudio/MegaTune and then swap the gauge to Duty Cycle. There are loads of gauges available, including the very useful "testGauge", "test2Gauge" and "deadGauge".

AGreen

iTrader: (11)

I tried that. Like I said, I had the ported throttle body without the the secondary butterflies (I guess they could be considered tertiary?) and no thermowax, no fast idle cam, nothing. The BAC was completely unable to raise the idle when cold. I have no idea why, but for whatever reason it won't raise the rpm very much at all. There's no blockage, the valve fully opens, I tried all kinds of frequency settings, PID settings, etc. It just doesn't do the job for some reason... which is why I reinstalled the thermowax and dashpots.

Anyways, I guess I could bypass the thermovalve and limit the RPM when cold. I use a manual boost controller for now, so I can't limit that on the fly. Yet.

peejay

It's weird that you say you had fuel economy/bogging issues previously. Where were you sourcing vacuum? Sourcing at the plenum (not the OE location in a runner) I barely needed any acceleration enrichment at all.

Accel enrichment is a LITTLE tricky with the non-progressive Holley setup, it's a little not enough fuel off idle and a little too much fuel up top, but there's a happy balance (setting idle a little rich helps) and it still gets 24mpg...

AGreen

iTrader: (11)

Update:

I did disable the thermovalve, and everything works out better all around. There is still, however, a bit of compressor surge under partial throttle in boost.

peejay, which vacuum port do you recommend? I currently use the one right by the BAC on my S4 manifold, so it's probably right in a runner. Are all the vacuum ports right after the TB spacer plenum vacuum, or are some of them "ported"?

AGreen

iTrader: (11)

New update:

I got around to messing with the car again, and found something really interesting. I had the MAP sensor vacuum line routed to a nipple at the BASE of the intake, underneath the UIM. So it was right in a single runner, and in the absolute worst spot for intake pulses. I never thought of that... at all! So I pulled the vacuum hose, capped the nipple, and rerouted a new vacuum line (the previous one got rock hard after only a year or 2) to one of the vacuum ports right behind the throttle body. The vacuum reading at idle was 3" more, so I had to change the fuel map to compensate for it. Most importantly, throttle response is CRISP! I was even able to cut back some on acceleration enrichment!

Thanks for the help everyone. I keep thinking I've hit the end and that there's no getting better, but I keep finding more awesome stuff!

davlilly

Wow, it really pays to just sit here and read through as many threads as I can.

I thought I had a vacuum issue still but I didn't know about the cold engine blocking secondary, I bet that is exactly what was happening last night to me. Because today (very hot with good time before driving) it was smooth, fun, and perfect.

Thank you all knowing RX gurus!

Knowledge is power, literally sometimes.

Thanks,
David

Aaron Cake

iTrader: (1)

The vacuum nipples around the throttle body lead to the small plenum are behind the throttle body which is ideal for vacuum pickup. Smooth and a good signal as that's where the primary runners merge.

These days, as I will be doing on my Cosmo when I reach that point, I ignore the factory nipples and seal them off. Then tap into that area for a 1/4" nipple, which runs to a vacuum manifold mounted under the intake manifold. That's where I pull signal for things like the ECU, boost gauge, FPR, BOV, etc. Really cleans up the engine and assures a good signal.