My Vettes tune is very good, but when cold it is very "cold" natured and doesnt really want to idle. It runs very well when warm. Even when in closed loop, until it hits around 160-180 degrees coolant temp, it wants to idle down and die. God forbid if I try to run the AC, it never does in or out of gear, hot or cold.
So, I can get TTS datamaster information, and I have a 93 with an auto, 2800 rpm stall, XE230/236 cam114LSA long tubes, heated O2's with a 396 cu inch displacement. If someone is willing to look at this and maybe alter my bin to help it idle better I would appreciate it.
I have Tuner Cat and a Moates prom burner to help. ALoha, Steve

 

Whats the commanded open loop AFR at idle when cold? Adding additional choke and increasing the AFR can help improve the cold idle. The stock tune is a bit on the lean side. The SA will also effect the cold idle. Too little, and itll want to die. These arent the only causes, but the fuel and spark are definatly the first place to look if it doesnt want to idle cold. Increasing the idle speed when cold can also help if the stock tune has the engine idling on the low side.

 

The tune is aftermarket, not stock. Is the open loop tune part stock? Or does the tuner change that. I will look at the AFR at idle when cold.
I have the ECM_DA2 file and I see open loop percent change. The table shows 14.7, but the open loop tables when cold show a percentage change. Am I looking in the right table?

 

I doubt they did much adjustment to the cold open loop tune. If its an aftermarket chip, Id start by first tuning the VE and spark tables and other basic items that are impacted most by a new engine. Was this car dyno tuned, or was it a mail order type chip?

I dont know much about the SD code in the vette's, but it sounds like its in terms of lambda if its in percentages.

If you dont have one yet, now would be a good time to get a wideband O2. When the engines cold it wont be an absolute, but it does give you a good indication if your too lean or too rich after startup. Id be willing to bet that once youve calibrated the computer to the motor, alot of teh cold drivability issues may fix themselves.

 

Hey, the tune smells rich when idling cold. So, it sounds as if it is needing more fuel as the ecm is adding fuel to compensate, or it wasnt adjusted much in open loop and the factory tune is still there. I guess I need a reference to match my tune in open loop to someone elses. I think I have some basics tunes for stock LT1's. I will do comaprisons.
In the VE tables, can you tune them in cold open loop mode? Or is based off temps only or Kpa? I am new to this game of tuning, and the acronyms are killing me still.
It sounds like I need to add fuel and timing to allow it to run when cold, or at least run smoother.

 

It would be easiest to do the VE tables with the engine fully warmed and get the warm tune dialed in. This is necessary because when the engine is cold, the AFR you see on the wideband wont be your actual AFR. The engine needs to be warm in order to fully burn the fuel to completion.

The base VE and spark tables are what the cold fueling and spark are based off of, so you want to make sure those are good before tuning any issues that come up when the engine is cold. Youll have to experiment to find out what AFR the engine runs best at when cool or cold, but Id guess it would be something like 13:1 at lower loads when its cool out, and richer in cold weather.

 

The warm tune is fine, as it runs real good and is very snappy. On the dyno, at WOT it was tuned to 12.7 to 1
I have to look for a wideband to borrow to see if I can datalog with an LM-1 or something.

 

The stock tune low rpm VEs of a cam over 230 are generally way too far high and the spark advance (SA) isn't advanced enough. I'd try to pull the VEs down first, and make sure it has a few more degrees SA than stock at idle.

John

 

By pulling the VE down, what percentage should/would you recommend?
And by pulling the VE down, does this richen it up?
Also, on the timing, how much should I advance it?

 

Thatll be something youll have to experiment with. Since you have an automatic, some of the VE cells are hard to tune as you cant really get to them. This is also a problem, because at low engine speeds, the engine will get into those high MAP, low RPM VE and spark cells and if their not right, itll want to die. Can you post some pics of the base spark and VE tables?

 

I am computer challenged right now, how do I copy apicture from tunercat and save it as a JPG?

 

Bring the tables up on your screen and hit the "print screen" key on your keyboard. Then in windows paint, copy in the screen shot. Open up a new windows paint pane and cut and copy the tables into that pane so just the tables are showing. Then do a save as saving the tables as GIFs or JPEGs. GIFs are grainy, but easier to read text wise.

 

I cant get the picture much bigger. Hopefully you can zoom in, and hopefully I have the right tables you want.

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I tried this too, the PDF file.

 

There's some good info here...mainly just subscribing. but...

A few things I've read...
For "pulling" VE, you are leaning it out. And, I read to go about 10% at a time to see how that effects your tune.
I think that I read to try to go about 2* at a time on SA.

I'm having some issues with my open loop tune with a big cam on my SD combo, too. Mine doesn't die (typically) but it runs horribly rich!

 

So when you go 10%, do you do the whole thing or just in the area of idle, including all the temps, or just in the temps you are dealing with?
On the timing, do you do 2 degrees throughout the idle, 800-1000 rpm regardless of temperature?
Also, do these changes affect open loop and closed loop? Or are there different tables of open and closed loop in a DA2 file?
Also, I did a trial run of VEmaster and it didnt touch idle, but it did changes above it.

 

I was looking at my Open loop%change tofurl/air ratio vs coolant chart/table and from 32C to 116C the change is 13.7 %, at 20C it is 18.8%, 8C 28.1%, -4C its 39.1%. So, since I live in Hawaii its in the 13.7% change all the time due to temperature, should I change this table a little richer, then add a couple degrees and work from there.
Or is it change VE tables and Timing?

 

for the 10%, just the area of the table that has the fueling issues (the temp, rpm, kpa, whatever your seeing on your datalogger at that point). same for the timing. Whether the changes effect open loop or closed loop depends on which table you're editing. Some of the more specific questions will need answers from someone with more experience than me. One other thing, you mentioned changing a table to make it run richer...it sounds to me like you're already running too rich but, I may have misunderstood something.

 

One thing I noticed was the timing. At low RPMs and high loads, you may have too much, assuming there are no SA bias' in the $8D. If its too much, especially with the added cool temp compensation SA, the engine might not like it. You may want to tinker with the timing in those areas. Also, under light load, you may want to hold the timing constant at low MAPs to the engine runs more steadily. Itll also probably want a fair ammount of timing to run well. Ive seen some stock computers give well over 40+ degrees at light loads.

FWIW, this was the general shape for the SA curve that I went with. The engine is close to stock, so it may not apply to yours, though.

 

Also, dont forget about the closed throttle SA table. Its not a 3D table, but rather a 2D table that has SA vs. RPM. That one is used when the throttle is closed. Even if the car is in motion, if the throttle is closed and below the threshold specified, that table will be used. Although, I dont think this is used when the engine is first started, only when its warm.

As for the VEs, tuning them in the low speed, high MAP areas where you seem to have trouble will be nearly impossible. What youll probably have to do is tune around that area and take a best guess as to what those cells should look like.

 

Thnaks. The richness on my LT1 is what I believe to not have enough fuel to begin with and the ECM is adding. The open loop may have not been adjusted from the factory. I dont have anything to compare. But, I went up 46 cu inches and put bigger heads and cam and induction, so I would think the engine would need more fuel. I need to find a factory LT1 table to comapre it too.
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I guess I can try timing first, and see what it does. I have the DA2 file also, not the $8D.
One change at a time.

 

The thing that is probably getting you is that the big cam, big heads,... will drop your vacuum. The lower vacuum will raise the fuel pressure at the regulator (assuming your car has a vacuum controlled unit on it). The extra C.I. will help pull a little more vacuum but probably doesn't make as much of a difference as the cam and heads do the other way.

 

I ought to see what it does with no vacuum at idle. Just for fun. I know it wont be any vacuum, but it wont be pulling a vacuum.

 

Vacuum regulators on port injection systems don't change the fuel pressure across the injector, which is the important pressure. That's the purpose. Keep the regulator connected.

 

LT1 files coming up!

http://www.bfranker.badz28.com/LT1Edit/LT1files.htm

 

What program will open these? TTS or LT1 edit?

 

I honestly don't know....but some are bin files so you should be able to open those with whatever.

 

I just want to see numbers to compare. I will try some other programs I have.
If anyone can open these and get data on a jpg or something, I would love to see the LT1 401 bin.
I have seen that car run, and it was very impressive and was very mild mannered. He also, at the time I saw it had no IAC. He had a Monoblade throttle body, and the IAC was laying on the side of the manifold.