How to TBI

[Sam Powell]

So what is your cranking pulse width? Don't hold back. I have bared my soul on this forum sharing all the successes and (many)failures, hoping these would be of help to others. Of course I was also looking for some ideas, and support as well. For that I thank you.

Share with us. Can you look in your configuration file and see what you have your crank pulse width set at? Does it have a modifier for ECT temp? What are the values of your modifier for the crank pulse width for startup? That would be information of great value to us all. In my opinion, it is much easier to install this stuff than it is to tune it. Dialing in the best numbers would be much easier with some working systems documented. The start up tune is especially hard, and everybody says that right up front. The manuals, the tech lines, all the books, all online articles, and those posting here say this. Don't hide your light under a bushel man. If it is not perfected yet, just say so when you share what your crank pulse width is now. Share your tuning process with us, and let us now how it is going. I haven't talked to anyone with an EFI system that is 100% satisfied that they have everything completely dialed in. So we can all help each other here. Thanks.

Sam

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A REAL professional is someone who knows when to hit it with a bigger hammer.

[runvs_826]

Well, I'm more than a 100% satisfied with my EFI and it truly isn't tuned perfect yet. The biggest problem I had is it would take exatcly 3 seconds of cranking and than it would fire up. First the timing wasn't advancing till lately which most likely isn't a cranking problem, and second we got a idle control something that will hold the idle at let's say 1200rpm till it gets warmed up.
This is my cranking setting for milliseconds.

The injectors are 55lb/hr at 15psi. This is the norm for the 350tbi, except for the police packages. The next step after it fires is it jumps to my VE map at the idlish at has an enrichment table that takes the percentage of the already given VE value per temp.

I hope this is a starting place and welcome more questions that I will look over with my Dad this weekend and try to help out as much as I can. So far I got a good starting place and I have to adjust the cranking table a little at a time try it for a week and than live with it or change it. The warmup is fine. Once again this isn't perfect, but a lot better than the carbs I've have had on this engine. Sam any direct questions you can PM me or boedighw@onid.orst.edu and we can discuss.

[Sam Powell]

Thanks man. That kind of informatio is really where it is at. This will give us all a starting place to work from. I appreciate your willingness to share, and your e-knowledge as a youth to get these table loaded up for us to see.

Sam

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

[Wizard]

Either you have too much fuel, a trick: crack open throttle while cranking did it fire off faster?

I had this problem (crack slightly on throttle while starting) on two old used up J-body caravliers that I had. No big loss as I only 120 for each and didn't do anything else as I found out they needed more than 2,000 in repairs to pass both E-test and safety so I got this 1987 caravan instead (for $700) that still needed work but body, carbed 2.2L, low KM (97,xxx KM) in 2003 was worth getting.

Otherwise too lean or way too little air.

Cheers, Wizard

[Sam Powell]

Runs, can you tell me what size, and how many injectors you are running? Maybe you have shared this before. If so I appologize for asking again. I have 6@ 36 lb injectors and would like to figure what would correspond to your 6.4 MS time at 40 degrees. Also, are there any modifiers at work on your injector plusewidth besides the ECT chart there?

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

[Matt Cramer]

Here's a basic rundown of the Megasquirt cranking cycle in action.

First, when the engine starts turning, it uses a straight pulse width table that only depends on temperature - the cranking pulse width. Once the RPM rises above the cranking RPM set point, it transitions to the main tuning, which is VE based. It will apply two enrichments. One is the warm-up enrichment, which is based on engine temperature and stays in effect until the temperature climbs over 170. Then there is after-start enrichment, which starts at one value (or a temperature dependant value depending on the code being used) and tapers off to zero after a set period of time.

You can set it to pretend the MAP sensor reading is a constant for a short period after starting, further modifying this.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
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[runvs_826]

Ok, well I replaced the motor mounts this weekend with High Density Molecular Plastic, it was quite an adventure. Went to start it up and was watching it for the start up to help all those who are reading this.
It started with going through the normal VE tables and Timing. The timing is backed down from 15 to 12, pop's was expirementing. The pulsewidths seem to be great. I was firing right up after a second, which is where the computer checks to see if I have oil pressure for two rotations. The wierd thing is it was jumping around on the VE table, but I don't think it was taking readings from that. It quickly would die right after I started the engine. I have an actuator that will hold the throttle a little bit open to help the engine warmup, but haven't installed it yet. Wanting it to start right away and not need a lot of operator input I looked at the AFR table while I was cranking and right after the fire. I was 16:1 as soon as the engine lit, soI changed my After Start Enrichment by a small factor and it started right up. I choose not to increase the warmup wizard cause I knew that wasn't where the problem was. To change the warmup wizard the engine needs to be fired up and running for a little bit that alter it to keep your AFR in range and warmup the engine.
The cranking pulsewidths should be good for right now, they are a detuned 350 since I'm using that TBI but on a smaller engine. For most warmup problems I would look at this table. Once you get a foundation stick with it for a little while and change factors you know effect the engine and can be accepted no matter what. The VE table and the Pulsewidth seem to be the biggest players, while the others are backups. So rough these guys out and work with the other tables. I now go back and change the VE table a little here and there while keeping almost everything else constant. In fact I mostly run the EGO correction with a 5% step and the engine runs smooth. Once I correct the rear diff angle (vibbbbbbbbration) I will come back with all my final tables and updates.

[Sam Powell]

What size and many injectors?

Sam

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

[runvs_826]

Two 55lbs injectors in a 90's (?) TBI off a 350. Stole it off a van, the guy looked at it, asked what it came off and took 30 of my dollars. Took it apart, carb soak, and put her back together. Get several injectors from the junkyard to make sure you got a good one.

[Sam Powell]

Thanks Runs. What kind of pressure are you running? My total injector sizing is almost twice what yours is. I would assume then maybe injector pulse widths of about half of yours would put out the same fuel. Am I thinking right here? Any body know? My 6@36 idle at 40 PSI. If Runs has 2@ 55 that is a total of 110. My 6@36 would be 216. If his pressure is the same then the pulse width on my injectors should be half what his is to deliver the same fuel. No? I'm trying to translate from your charts you published here to my setup.

Sam

_________________
A REAL professional is someone who knows when to hit it with a bigger hammer.

[runvs_826]

Got to take her for a short drive this weekend (really need those rear axle shims). She fired right up, you still have to hold the pedal for alittle bit while it warms up. I would think on paper your thinking is correct. My only worry is that at idle we should have the same pressure in our manifold. Because I'm already walking the limits of to much fuel you might want to cut it in half like you metioned, and than not be afriad to cut a little more. I have no idea how your firing, but I had to lean mine out during cranking and right after fire. I kept thinking like a carb, just give it a little more fuel till it fires, than I started working backwards.
However, your numbers do add up for supplying your engine while under lets say 10 pounds of boost. keep firing the questions we might figure this darn thing out.

[tommj55]

I need to fabricate an adapter plate for my dual-injector TBI to my Clifford 4-bbl intake. Although my 2-bbl intake has the holes oriented east-west, it seams like the fuel distribution for my injectors would be better if they are oriented north-south.

Any thoughts?

Thanks,

TJ

[sandy in BC]

click to view full-version

Heres my version.

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http://www.arrowtipi.com/My%20Webs/index%20Valiant.htm

[tomj55]

Thanks, Sandy.

That's how I was planning to set up mine.

- TJ

[runvs_826]

That's approx how mine is set-up but I had to tilt mine a little bit to clear the throttle pull, and maximize the two holes when I cut the manifold to the two barrel (it was a standard one hole not super six).
Lesson to the wise, you can very simply fry the HEI with the Megasquirt computer. My pop's bless his soul changed to Megatunix and sent my ignition module to the graveyard. I would suggest a crank trigger which is what I'm doing next time, or an MSD set up. My uncle is sending me his Jacob's box cause he's switching to something else. I would update with what I got, but the computer did a total flip and it isn't running right at all. I somehow managed a 117% VE at cruising so will be back soon to give more updates.