I'd like to get a discussion going on this topic. I been looking at the related tables comparing the TunerCats tdfs $6E and $32B, using the infamous ARAP bin for 6E, and my 1988 stock 350 bin ABYA. I have been using the 6E cal for a long time, (without cold start injector)but recently just switched back to a $32B bin, just to try some other things out.

First lets look at the tables, which are pretty much common to both bins. There is "crank fuel PW mult vs TPS", "crank fuel PW vs coolant temp", and "crank fuel mult vs reference pulses". The first 2 are identical tables between the 2 tdfs, but the 6E has 2 crank fuel mult vs ref pulse tables. One goes pulses 1-16, the other 17-24. But the $32B table goes out to 128 ref pulses. In my ARAP based bin, I did basically what everyone else does, and put some multipliers in the first table that had 0s in for the first 8 pulses. I haven't messed with any other table entries.

With the ARAP based bin, my car starts pretty good with engine cold. IE sitting overnight in garage or for longer periods. It would crank right up in a sec or less, just as you turn the key. But my when my engine is warm, like when I go somewhere and park for an hour or so, it cranks longer to start. Not real predictable either. Sometimes it seems like I crank forever.

So when I looked at the tables for my stock $32B bin, the numbers were different. It had a multipler of 1.0 for all ref pulses, and the crank PW would change as a function of the coolant temp. So what I did was setup a spreadsheet calculating all the PW for each temp vs ref pulse. Lets take a temp of 80c,(176degF) the PW was 3.9, 1.95 and 1.55 for the $6E, as the ref pulse increased.

For my stock 32b, it was 4.28msec, for all pulses. What I am saying is that the ARAP bin drops fuel off quickly, as the ref pulses come in, and my stock bin keeps it the same, AND they are larger PWs. Also my stock 32B setup HAD a cold-start injector, while the ARAP based bin is for NO injector.

Okay so now lets do some math. For one dist revolution you get 8 ref pulses, which is 2 crank revs. Right? If you crank the engine at 450rpm, that is 7.5 crank rev per second. So I figure at 7.5 rev/sec = 30 ref pulses/sec. The 6E tdf only goes out to 24 ref pulses! But the 32B goes up to 128. You have about 4sec of adjustability with the 32B, and less than a sec with the 6E. I would imagine if you crank longer than that, the ECM would use the last number in the table.

Now I been looking at some scan data when I crank, but kind of hard to really see when she starts, and get the timing down accurate. But lets say a 1 sec crank to run is a good starting point. Where would I start to help my long (warm enging) crank times? Since I started using the 32B cal, I THINK it is starting better. Should i increase the PW at higher temps? I am also thinking about taking fuel away (decreasing the mult) after 2 or 3 sec of cranking. It could be flooding the engine. The only thing I really can conclude is about he cold engine starting. At 8degC or 46F, the PW is 12.9msec. So that is my starting point.

If any of my math is wrong please correct me. I would like to get as much input on this as possible.

 

The crank fuel vs TPS, is mostly for being able to enter a clear flood mode. Rarely do it take playing with.

Crank Fuel vs CT is how much enrichment there is due to temp..

Crank Fuel Mult vs ref pulses, is how fast you want to dump fuel while the engine is cranking, and how to cut back on that initial dumping of fuel.

Probably a base PW time constant in there somewhere also. That might need dinked with if you change injector sizes.

Doesn't take much of change in the CT correction to make a serious change. I'd wager 90% of any starting problem can be taken care of there..

It's just another element that makes tuning an art form. Getting in there, and making changes, is where the understanding comes from. Lean might get a bad start situation, but rich will easily foul the plugs.

For initial run stuff, the added timing is also something to look at.

 

That's a good description, Grumpy. I didn't really talk much about the crank fuel vs TPS, that one is kind of obvious. But there is one thing mentioning here. In the normal ARAP bin, the mult is 1.0 up to the high %tps,where you go 0 to clear flood. But in my stock 88 bin, they actually increase the mult greater than 1.0 like upto 1.80 at 75%tps. Kind of like when you give a carb some gas to start a cold engine. But remember you are also opening up the throttle blades, letting air in as well. So not sure what the intent was there with GM.

I guess I might just play with the PW vs coolant, and see how it affects things.

Anyone else?

 

I think that even with the throttle blades fully closed, and the IAC in its park position, you are gonna be reading damn high load. Not sure how close to 100kpa, but probably not too far (because cranking speed isn't enough to really begin to pull a vacuum). So the extra fuel at a high TPS really would richen up the crank AFR even with the throttle blades open because it's not pulling much air to begin with...I think that made sense.

 

There is no intial engine vac when it starts. It takes about .2 sec to pull down the manifold. Somewhere is the archives is a datalog where I showed that.

The park position, warm IAC park positions, max IAC count all play big roles in the start routine. The max IAC count often is what causes the intial flare on start up. But, you have to watch what you do there, since it means max total, and with some cars you want alot of Throttle Follower.

 

During crank, and I'm sure it might varies by code, the VE tables aren't used until the engine actually is running. Going 100% TPS with a 100% entry of 0, means clear flood which might mean no fuel, or just extremely lean, ie 22:1 AFR.

In some code, they give a cranking AFR, in addition to the above mentioned crank stuff.

 

I haven't seen the cranking AFR in the cal's I been using. I left most of the IAC stuff alone, or at least it as the same as my values in my ARAP bin. I have the IAC startup park position stock at 144, but I did change the steps vs coolant table, thinking I would help the idle flare up after start. It might have helped a little, but the one thing that helped more was the IAC startup delay time constant. Stock bin was 1000msec, ARAP was 400, I set it to 500.

One thing I did notice, was when I switched back to the 32B cal, I DON'T have the idle flare-up after start. The idle just goes up to about 800 on a cold engine, then slowly goes up to 1000, and then will work its way back down to normal as she warms up.

The park postion constant is the only IAC parameter that would affect cranking and engine start, IMO.

I think I actually like the ARAP bin better for idle control, the flare-up is manageable. I just switched to test out some other features of the 32B.

Since I been using flash chips, and I got the windows ver of PPII working good, making small changes just to try out an idea, is a real snap. Just wish I had more time for it!!

 

When you make a statement like that, it's universal in nature, and not always be true.

IMO, is an opinion, which is fine, but also can be misleading, and even wrong at times.

You have the Key-Off max IAC count, Park Position, and then the hot restart, park positions.

 

Here is the way that I got my car to start right up, like you described with yours in the "cold" state.

I used a romulator, so it made the changes about 100X as quick and I got it to start perfect in about 10 minutes.

My car after the engine swap would need to have the gas peddle depressed to start. From that I figured that the engine was not getting enough air and too much fuel.

I went to the crank PW vs Coolant tables and determines at what temp the hard starting was occuring. That is fairly simple in a vette, since it has the metric/english switch and all my gages turn to metric, so I just watched the temp gage as it climbed to each temp range defined in the chip. I would stop the car and make sure for not to long, or the coolant will get heat soaked. I would try to start the car. If it didn't start immmediately I would pull some pulse width. I could tell I was going the right direction since the starting was quicker and quicker with each adjustment.

I finally reached about 82*C where my car was a real bear. I just did the above and now I can reach through the window and turn the key for an instant start with no gas peddle needed. Another thing I noticed that the car did before, even if I did not have my foot on the gas and it started. It would rev up to about 1500 then settle back to 950 where I have it set. Now it starts and is almost instantly at the desired idle speed.

Just play around with the coolant table. It will adjust it enough that you can get a nice clean start.

 

Well I am glad I put "IMO" in my response, seems like that saved my bacon. I won't argue with you Grumpy, I am sure there are many other parameters, in many other cals, that can affect startup. But I only know what I have in front of me, and those tdfs are the 32B and 6E, as mentioned in my orginal post.

I emailed back and forth with TC over the winter, having them explain how the ECM and these tdf's start the car. I have the procedure all written down somewhere, but that is another topic.

Ski, finally some real world experience to possible help me with my problem. I like your method. It just might take me longer than your rom method. I tried a bin over the weekend with a PW of 6.6ms from 32c to 92c, and mult=1.0 for all entries in the $32B cal. Didn't seem to help, since today I had a chance to test it out, and kind of long cranks while warm. I did a scan with the coolant at about 138F, and the PW was exactly 6.6msec as in table, but engine crank was about 2.53 sec. I was able to set up my scan tool to look at 6 parameters at a time, to try and figure out what is going on. It showed me alot of info. The bat bolts drops to 9.6v while cranking!!

But the most interesting thing I found, is difficult to explain. With all my scans using a $32B bin, the crank PW was EXACTLY as I specified in the table, at xx coolant. When she fired, the PW went down, then settled out low at idle around 1.5ms. Crank times varied, with the shortest occuring at colder temps.

Then I looked at some scans using a $6E based bin. What I found was amazing. There was 0.0mS PW during all cranking!! Then when she fired up the PW went up, to little bit over idle PW. It didnt matter what coolant temp was. And yes, I have multipliers in all entries of that ref pulse table. Could it be that with a $6E bin, the engine cranks so fast that it goes beyond the table, giving no fuel at all? Is there a bug in the code? Some kind of delay hidden in the code that I don't know about? Maybe I need to send TC an email asking for other parameters.

What I did tonite was plugged in a lower PW for cranking, like 3.1msec from 32c to the end of the table. Have to try that out tomorrow.