Good afternoon Miata Turbo. Hoping this forum is slightly less dead than the rest. I come to you as an N/A user hoping to absorb some wealth of megasquirt knowledge. I'll start a build thread later tonight after I drink some beer.

I have recently installed corolla ITBs on my 1994 Miata. The motor is otherwise stock, save for a header and catback. Widebad being used is an AEM UEGO 30-4110, which seems to be working to the best of my knowledge. The car ran with no issue prior to ITB/MS2 PNP install, harness untouched, etc.

Frankly, I am lost. I was able to get the car started using both the included base tune switched to Alpha N, and a tune I have edited slightly that was provided to me by a stranger off the internet in ITB mode. Its tough to start, requiring playing with the throttle. Tons of backfiring. I have to keep the throttle cracked to keep it running, otherwise the revs drop to about 450, idles for a bit, then leans all the way out. I have not been able to get it running long enough to check base timing. I would love it if someone could look at my tune and datalog to point me in the direction of getting this car to idle. I am positive that I have not shared enough information but I am sure I can provide any information needed.

pic of car:

 

you can check the base timing by just cranking it.

 

I just needed someone to crank while I checked timing, which I was able to do last night. I corrected the base timing to 10deg BTDC, starts a bit easier now and runs a hair smoother with throttle cracked. Still no real luck getting it to idle. I might have a chance to fiddle with it tomorrow evening.

 

Only change one thing at a time when possible. Should have installed MS and set base timing with stock IM and injection. Then switching to ITBs so only one major variable.

ITBs are probably not evenly adjusted for idle airflow, my guess.

 

Yeah the initial plan was to do MS, get car running, then do ITB. The timing of shipping/upcoming winter sort of forced my hand and I became a bit ambitious, still wish I had done MS install first but hindsight is 20/20.

I've tried to mess with the idle screws on the TBs to get them sort of close to each other. I figure that it would at least try to idle even if they're not exactly synced. I have admittedly only skimmed the Mega Manual at this point, I plan to go through it fully sooner than later. What I have been seeing for idle tuning in my googling has centered around tuning the iacv (a thing I no longer have because of the ITBs), or just fixing a rough idle. Should my focus be on tuning the VE table in the idle range, are there other parameters I am overlooking associated with idle?

 

Warm Up Enrichment
After Start Enrichment
Cranking Pulse or something like that

If you had the timing belt off for any reason all bets are off because timing these things is inaccurate most times.

 

I have the Toyota itbs running on my car. It would definitely have been a LOT easier had you swapped the ecu first, gotten to know it well, and then swapped in the itbs. But as you mentioned, too late for that.

While you don't have to have an idle valve, you will want one. It is a fact that engines take a while to warm up and as they do the idle quality and speed changes. If you want/need a decent behaving car, get one rigged up. If you just want a show car then whatever.

Get the throttle bodies sync'd. Buy a sync tool. If you want a decent idle, this is not an option. Eyeballing it is not good enough.

Use idle fuel and timing. This will lock the fueling and timing into tight settings so the engine isn't surging and searching and looping into making itself shut off. Once you have a very good tune then maybe turn off the idle lock.

There are two ways to having an itb car run well: multiple fuel and spark maps or ITB mode. IMO, ITB mode is easier. However, having read how a couple of people have done multiple maps, I can see it being better. Both strategies require using a MAP sensor. So if you don't have a vacuum block yet, get one.

There are quite a few threads on the megasquirt forums that you may want to research.

 

Well said.

OP, for reference, just take a look at base tune idle valve duty cycle tables. Notice how the engine wants a bunch more air to initially start, and then to maintain idle quality until the coolant gets up to temp.

If you're not running an idle valve, you either have to live with a high warm-idle speed, or manage the changing airflow requirements yourself with the throttle pedal until it gets some temperature into the engine.

 

thanks for the commentary, I do plan on putting an iac in at some point, for now I would be happy with a high idle. I will plan to tune the car in ITB mode, I was on the fence as most of the threads I have been able to find about miatas/ITBs went with alpha-n. Granted these threads are from before ITB mode was available or when it was very new. I plan to sync the throttle bodies as soon as I can get the car to run without a foot on the gas.

When you say use fuel and idle timing, are you just suggesting just modifying the ~9 lower left cells in the VE/Ign tables? I am not seeing an option for "idle lock" in the manual or Tuner Studio.

I noticed my fuel and ignition tables only go down to 800rpm, how does the computer know how to operate between 0-800 if that is the case? is it a matter of interpolation? would it run better if I specified values for ~500rpm?

Thanks in advance, I really want to learn and I appreciate the information on this forum. I'm not a total moron I swear, took an ICE class in college and have a pretty comprehensive understanding of Mazda's BP in stock form. I'm just trying to get an idea of where to focus my attention at this stage. I don't want to overlook certain settings while incorrectly adjusting others to compensate if that makes sense.

pic of wheels that landed yesterday:

 

Yep, I have a 500rpm row. Nice to add a timing bump there to help the motor pick back up if revs get low.

Wheels look good! How much did the set run you, if you don't mind me asking?

 

I'll add a 500rpm row and toot around with the values in the idle zone of the maps. I'm thinking its too rich since it only starts with the throttles open about 12%. That being said, it starts most consistently if cranked until it acts like its catching, then opening the throttles. If I open the throttles before I start cranking it doesn't like to start.

I think ~$1900 after import fees and 5-day DHL shipping from japan? they are my favorite size te37 so I had to have them haha. they are also mint and look like they have never been mounted.

 

This is your car, time, and money and I am in no way telling you what to do but I think it is imperative to have a functioning idle control valve. It's not that difficult or expensive to do, so I'll just let you in on how I did mine. Get the IAC valve from a NB miata or from a 90's Ford. Just about any will do. JB weld, or epoxy, or whatever, two hose barb ends on the valve. Put a filter on one end and run the other to your vacuum block. The vacuum block doesn't need any sort of volume, just four nipples to connect the vacuum source from each cylinder, (which I assume you have a T3 adapter manifold) and the nipple for the IACV, the PCV,* and one for the MAP sensor. I got rid of the booster so I didn't need any other vacuum source. The NA connector on the IACV will have to be de-pinned and the appropriate plug installed. Done.

Having said that, I run a very high idle. About 1100 without AC on since that's where the AWR engine mounts loosened my fillings the least in what I would consider an "idle" and 1200 with the AC on since the compressor works better (still not great) at this speed. Without the IACV, no way could I have the AC compressor on at idle. But you get the point.

I mentioned idle fuel and ignition settings as I have MS3. I looked and it would appear it *may not* be available for MS2 but I didn't research it that hard. MS2 does have idle ignition setting though, so at least give that a shot. So basically this is a form of table switching. So if you are getting a surging idle, your ecu is going through all of the different cells and plugging in those numbers and it sometimes becomes a vicious cycle that never ends. By having idle fuel and timing on, you have another set of tables that are not part of the regular VE and timing table, so you don't use those numbers, or at least you wouldn't want to use similar numbers, which help stabilize the idle. So lets say at 900 RPM and 20% load or KPA (low rpm, high vacuum) you want a VE number of 40 and timing of 20*. Well idle is defined as low rpm, low load, no TPS action. So as long as those parameters are met you can stay in idle fuel and ign. and even though the engine stumbles causing the regular tables to go to opposite ends of the spectrum for fuel or timing or both, since you are using the idle tables, the surging and hunting is generally brought back in line quickly without going into a vicious cycle since it's giving the engine a steady amount of fuel and ignition. This is what I meant by "locking" in the settings.

Now, above is something I mentioned that you may want to check because it was causing an issue for me. Check your TPS for noise and make sure you are not falsely engaging acceleration enrichment. So if your tpsdot is 40 even with no pressure on the TPS, make sure your AE activation is at least 10-20 numbers higher. I was able to get the noise down a little to about 20 tpsdot so I have my AE activating after 40 tpsdot.

As far as table limits, anytime you are operating below or above the limits, the last setting is used. So if you have 20* of timing set at 800 rpm, then you get 20* at 500 rpm. AFAIK, there is no interpolation after min and max, only in between.

As far as where to focus your attention, I already made the case for getting an IACV, a sync tool, and checking the tpsdot for noise. I would also check some mechanical things like do you have a vacuum leak? The T3 manifolds are notorious for leaks. And anything else that you may suspect. You might be thinking "tune" but the gremlins may be somewhere else. Never disregard the basics.

Oh, almost forgot. *= An ITB car at highway speeds will have about 25% throttle opening which equates to 90 kpa or not much vacuum. You will want to run a catch can and a very well ventilated crankcase breather system. Ask me how I know.

 

Maybe easier said then done, but rope in a friend who can control the throttle while you play around in the engine bay. It sounds like needing four hands is holding you back at this stage of the game.

 

I want to add that everything Hector has said is spot on. I ran my ITB motor without an IACV for a long time by opening the idle screw a lot, then decreasing timing to 5-10 degrees, and used timing to increase idle as needed for the fans and electrical loads. I had to hold the throttle to help it idle when cold though. Then I added the stock NB IACV and it was a night and day difference, I will not do it any other way.

There are a few things I find odd in your MSQ, maybe I loaded the wrong firmware? Regardless

Under General Settings:
- Barometric Correction you have "Two independent Sensors" selected, yet the same source. I don't think this would work well because ITB mode needs to know your actual baro to decide when to use Alpha-N or Speed Density. Try using "Initial MAP Reading" if you don't have a separate barometric sensor installed.
- You have Old baro calc > "Off", but your barometric correction table is set to all 0s. Switch those to all 100 for now.
- Incorporate AFRTarget is not enabled. This isn't a problem, but it would make your life easier if it was included, because later you can change the AFR targets without having to modify your VE Table.
Under Fuel Settings and Ignition Settings:
- Load axis in VE and Ignition tables go over 100, which is not the case with ITB mode. Re-scale them from 10 to 100 for ITB mode.

I think it might help if you re-scale your tables, include AFR, and increase your VE values. In the log I see that at 62 Load you had a VE of 39, which sounds really low for 71 MAP. Also from your log, I didn't see any barometric corrections, and your baro field was reading seemingly fine, so I'm guessing the tune was changed at some point, or something is not loading right for me.

And to echo what others have said, you need to make sure all 4 throttles are synchronized, otherwise you'll be chasing your tail.

Edit: I found what I did wrong loading your tune. The baro field is correct, but you should still decide if you want to use the new or old calculation method. I still think your VE values are too low for the cells you hit in your log.

 

Ah, one more thing. If you do change to the new baro correction method, you also need to change the settings in Tools > Calibrate MAP/Baro > Barometric Correction. Judging by what I see in your msq, you have it set to half of each across the dialogs.

In case it helps at all, here is my MSQ. I have an MS3Pro PnP, firmware 1.5.1

 

Hector, I know that this is old, but I'm working on an ITB system on a non-Miata, and I'm noticing just how much water I get in the catch can...I'm preparing to go to a bigger one...can you explain why it matters more for an ITB setup? (FWIW, Heavily modified Ford 2.0 Zetec in a Caterham)

 

IMO, it matters more because at cruise/highway speeds you don't have vacuum which means the PCV system isn't working. On a track car that spends a lot of time at WOT, same thing. You need crankcase ventilation and when we modify our cars we tend to forget this which is what happened to me and I was getting oil splatter everywhere.

The catch can is not really necessary if everything is well ventilated but having it prevents the oil it catches from getting back to the engine in a PCV system. In a non-PCV system having a catch can with a breather filter helps keep the oil splatter to a minimum. Again, this is all IMO.

The water in the catch can I can't be certain of. Obviously it's condensation but from the separation of the oil or simply from normal condensation build-up I don't know.