datamaster, glowing red headers. gurus please help
Safety Car
Joined: Jun 2003
Posts: 4,250
Likes: 656
From: San Diego Ca
Just a note. Brian still has stock injectors so the car will go lean at wot with them, but are certainly not a problem at idle and that is what we are chasing now.
I have looked at a number of tuning files and logs I have from when I did this a lot. All the LT1s in the 383/396 NA and the SC variant idle at less than 60 kPa MAP. Even my max effort LS2 402 would idle in the mid 40's. Now it started in the 60's but i was able massage the timing, VE, and MAF tables to get it back to the mid 40's for smooth idle.
For spark advance all of the LT1s I have got are running 30 deg advance in the idle range or more. My LS2 would idle at 21 deg advance but we are talking an order of magnitude more efficient head design.
So at this point the only things I see out of sorts on the log are the 60 kPa MAP and the 21 deg advance. Now the stock 94 tun gives you 20-23 deg of advance at 800-1000 rpm and 60 kPa but the computer is expecting you are there on deceleration not idle. At 40 kPa and idle rpm you will see more of a 30 deg advance or more in the tune.
Brian, what are the specs on the cam again? And was it degreed straight up?
I have looked at a number of tuning files and logs I have from when I did this a lot. All the LT1s in the 383/396 NA and the SC variant idle at less than 60 kPa MAP. Even my max effort LS2 402 would idle in the mid 40's. Now it started in the 60's but i was able massage the timing, VE, and MAF tables to get it back to the mid 40's for smooth idle.
For spark advance all of the LT1s I have got are running 30 deg advance in the idle range or more. My LS2 would idle at 21 deg advance but we are talking an order of magnitude more efficient head design.
So at this point the only things I see out of sorts on the log are the 60 kPa MAP and the 21 deg advance. Now the stock 94 tun gives you 20-23 deg of advance at 800-1000 rpm and 60 kPa but the computer is expecting you are there on deceleration not idle. At 40 kPa and idle rpm you will see more of a 30 deg advance or more in the tune.
Brian, what are the specs on the cam again? And was it degreed straight up?
Thread Starter
Racer
Joined: May 2014
Posts: 489
Likes: 66
Just a note. Brian still has stock injectors so the car will go lean at wot with them, but are certainly not a problem at idle and that is what we are chasing now.
I have looked at a number of tuning files and logs I have from when I did this a lot. All the LT1s in the 383/396 NA and the SC variant idle at less than 60 kPa MAP. Even my max effort LS2 402 would idle in the mid 40's. Now it started in the 60's but i was able massage the timing, VE, and MAF tables to get it back to the mid 40's for smooth idle.
For spark advance all of the LT1s I have got are running 30 deg advance in the idle range or more. My LS2 would idle at 21 deg advance but we are talking an order of magnitude more efficient head design.
So at this point the only things I see out of sorts on the log are the 60 kPa MAP and the 21 deg advance. Now the stock 94 tun gives you 20-23 deg of advance at 800-1000 rpm and 60 kPa but the computer is expecting you are there on deceleration not idle. At 40 kPa and idle rpm you will see more of a 30 deg advance or more in the tune.
Brian, what are the specs on the cam again? And was it degreed straight up?
I have looked at a number of tuning files and logs I have from when I did this a lot. All the LT1s in the 383/396 NA and the SC variant idle at less than 60 kPa MAP. Even my max effort LS2 402 would idle in the mid 40's. Now it started in the 60's but i was able massage the timing, VE, and MAF tables to get it back to the mid 40's for smooth idle.
For spark advance all of the LT1s I have got are running 30 deg advance in the idle range or more. My LS2 would idle at 21 deg advance but we are talking an order of magnitude more efficient head design.
So at this point the only things I see out of sorts on the log are the 60 kPa MAP and the 21 deg advance. Now the stock 94 tun gives you 20-23 deg of advance at 800-1000 rpm and 60 kPa but the computer is expecting you are there on deceleration not idle. At 40 kPa and idle rpm you will see more of a 30 deg advance or more in the tune.
Brian, what are the specs on the cam again? And was it degreed straight up?
the cam was this kit off ebay
"CHEVROLET PERFORMANCE PARTS LT1 / LT4 / 5.7 350 HOT CAM KIT 12480002 GM OEM
( 131313083572 )"
i did not use a degree wheel. lined up the dots and installed. Was that a no no?
Thread Starter
Racer
Joined: May 2014
Posts: 489
Likes: 66
I havent hooked up tuner cat yet cuz ive just been busy the last couple days but i was walking past it after work and i couldnt resist.... I took it for its first spin to see how its reacting. By quick spin i mean like 100 yards down the road and back. It has an initial pop/backfire/bog out the front air cleaner. Like a back fire. Then responds fine i didnt give it to much gas but the get up and go seemed decent. After parking it again and moving the throttle it would do the pop thing every time i gave it a little gas. Also the idle is not consistant. Will idle smooth then drop down and sound like theres a tad bit of bog for a few seconds then smooth again etc. just hopi g so e of that helps.
Racer
Joined: Aug 2014
Posts: 287
Likes: 9
From: Toledo
I would try another computer. I know, I know. Not that easy. Did you have your heads worked on? Are the knock sensors installed and working?
Last edited by chadk; Jun 30, 2015 at 10:52 PM. Reason: wrong thread.
Thread Starter
Racer
Joined: May 2014
Posts: 489
Likes: 66
Oh boy... That would mean i would have to pay for another tune right? Or does the tuner cat tune? This is the same computer that was in it before. Pretty much everything is the same other then refurbishing and upgrading.
Thread Starter
Racer
Joined: May 2014
Posts: 489
Likes: 66
I have a local mechanic who will look at it but hes still a couple weeks out before he could. Id pay a mechanic to figure it out if i could find one.
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Racer
Joined: Aug 2014
Posts: 287
Likes: 9
From: Toledo
Oops " headwork" yes heads have ported runners, gasket matched and the bowls have been cleaned up as well. The intake was gasket matched and lighy ported as well along with a 52MM throttle body. I did the head work myself and it came out very nice. I have pics posted in the build thread. No they have not been flow tested but ive done quite a few heads and never had any troubles. Not saying i rock at heads but ive done enough.
I have a local mechanic who will look at it but hes still a couple weeks out before he could. Id pay a mechanic to figure it out if i could find one.
I have a local mechanic who will look at it but hes still a couple weeks out before he could. Id pay a mechanic to figure it out if i could find one.
Thread Starter
Racer
Joined: May 2014
Posts: 489
Likes: 66
Obx long tubes straight to mufflers. True duals with no cats.
Intake leak... I can check again but wouldnt it idle higher then it is if there was a leak?
Adjust my timing in closed loop.... How can someone give me a walk through on how to do this? Datamaster im figuring out but tuner cat has lost me a bit.
If i make an adjustment how do i know my motor is running at peak performance with the mods? Meaning is there something in the softwaer that can guide me or is this going to be a matter of experience and knowing, in which i would be lacking
I dont want to just make it run right, i want to feel all the mods ive done and have this motor putting out its max For the mods. I thought the car was pretty quick before the mods and with everything iv done to it .... It should be a beast.
Intake leak... I can check again but wouldnt it idle higher then it is if there was a leak?
Adjust my timing in closed loop.... How can someone give me a walk through on how to do this? Datamaster im figuring out but tuner cat has lost me a bit.
If i make an adjustment how do i know my motor is running at peak performance with the mods? Meaning is there something in the softwaer that can guide me or is this going to be a matter of experience and knowing, in which i would be lacking
I dont want to just make it run right, i want to feel all the mods ive done and have this motor putting out its max For the mods. I thought the car was pretty quick before the mods and with everything iv done to it .... It should be a beast.
Safety Car
Joined: Jun 2003
Posts: 4,250
Likes: 656
From: San Diego Ca
I agree on the 30 degrees at idle MAP and RPM.
If you will hook up TunerCat and download the file to your computer to me, I will adjust the timing for you and email the adjusted file back and all you have to do is load it.
Once we do that we can better isolate whether or not you have something mechanically wrong also. As I said earlier I think your tune likely has 30 degrees at idle baked in, but that your tuner was expecting you to be idling in the 40-50 MAP set of cells and you are idleing in the 65 kPA MAP range and those cells are for deceleration so command a much lower spark advance.
If you will hook up TunerCat and download the file to your computer to me, I will adjust the timing for you and email the adjusted file back and all you have to do is load it.
Once we do that we can better isolate whether or not you have something mechanically wrong also. As I said earlier I think your tune likely has 30 degrees at idle baked in, but that your tuner was expecting you to be idling in the 40-50 MAP set of cells and you are idleing in the 65 kPA MAP range and those cells are for deceleration so command a much lower spark advance.
Thread Starter
Racer
Joined: May 2014
Posts: 489
Likes: 66
I agree on the 30 degrees at idle MAP and RPM.
If you will hook up TunerCat and download the file to your computer to me, I will adjust the timing for you and email the adjusted file back and all you have to do is load it.
Once we do that we can better isolate whether or not you have something mechanically wrong also. As I said earlier I think your tune likely has 30 degrees at idle baked in, but that your tuner was expecting you to be idling in the 40-50 MAP set of cells and you are idleing in the 65 kPA MAP range and those cells are for deceleration so command a much lower spark advance.
If you will hook up TunerCat and download the file to your computer to me, I will adjust the timing for you and email the adjusted file back and all you have to do is load it.
Once we do that we can better isolate whether or not you have something mechanically wrong also. As I said earlier I think your tune likely has 30 degrees at idle baked in, but that your tuner was expecting you to be idling in the 40-50 MAP set of cells and you are idleing in the 65 kPA MAP range and those cells are for deceleration so command a much lower spark advance.
Thread Starter
Racer
Joined: May 2014
Posts: 489
Likes: 66
Thread Starter
Racer
Joined: May 2014
Posts: 489
Likes: 66
Thread Starter
Racer
Joined: May 2014
Posts: 489
Likes: 66
So I just heard from the mechanics shop on this issue. They said the ignition timing is right on but the "timing" is off. He said it looks like it's a tooth off or needed to be degreed.
This has to be physically done, correct? This can't be done with the pcm?
Anyone want to buy a corvette? $13k and its yours
This has to be physically done, correct? This can't be done with the pcm?
Anyone want to buy a corvette? $13k and its yours
Safety Car
Joined: Jun 2003
Posts: 4,250
Likes: 656
From: San Diego Ca
Sorry to hear that. No that needs to be done back at the timing gear if I understand their diagnosis correctly. You ought to be pretty savvy with getting at the front end of the motor with all you have done. 99% of the time you can line up the dots but that other 1% of the time you are happy you pulled out the degree wheel and found TDC.
At least that sounds like a definitive fix once it is redone.
At least that sounds like a definitive fix once it is redone.
Thread Starter
Racer
Joined: May 2014
Posts: 489
Likes: 66
Ya happy to have it figured out but this car is probably going to get a tarp thrown over it and sit for the next couple of years. I just have no desire to pull the motor back out of the car.To many other projects going on.
It couldn't be don't while still in the car could it?
It couldn't be don't while still in the car could it?