Lt1 timing tables

[jason k]

I found a stock lt1 timing table and I want to try to copy it into my main spark table as a starting point but the lt is rpm vs map I think anyways, makes sense to me, and in hp tuners it is rpm vs cylinder airmass (g/cyl) Is cylinder airmass and map a variable I can interchange. This is what the lt1 file looks like

[MikeOD]

The LT1 PCM (8051) did not calculate air mass for spark advance, it just referenced spark advance to manifold pressure...the LS1 PCM does not work the same way.

I will say you want to run an LT1 around 34-36 degrees of advance at full throttle if it's NA...what you need to do is log a pull at full throttle and see what airmass the engine hits...then set those cells to that spark value. You see stock it ran 33 degrees...but they always woke up for me going up to 34-36ish.

After that, you want to cruise around 45 degrees, and it'll probably idle nice around 22-25.

[jason k]

Thanks I'll try it out. Right now at cruise I'm 36 ish 22 wot and idle around 20-22. I'm trying to figure out if I have knock sensor issues before I advance to far I had It 2 degrees higher across the board but I started throwing misfire codes immediately after so I backed it down and they are still there

[edcmat-l1]

That's no where near enough timing for an LT1. You can add 10 degrees to it at cruise, and at WOT easily, if it's NA.

What mods? NA? Cammed? What's the compression?

If you're having misfire codes with the timing where it needs to be, need to address that, not kill the timing to cure it.

[jason k]

The misfire code came up immediately after I advanced it so I thought that might have been the cause. The car runs fine, Meaning I feel no misfire, but that means nothing there are counting in history according to my modis. I also am getting some knock retard I picked up scanning it last night I'm going to look at the scan when I get back to the shop and post the tune and scan.
It is a 95 lt1 with a lt4 hot cam 219/228 @ .050 .525 lift and 112 lobe, factory extreme duty timing gears, heavily ported stock heads, Manley valves, stock slightly ported intake, long tubes, no cats, 24x system, fuel pump, adjustable regulator, 36 lbs injectors, pulleys, k&n air intake, 10.5 comp stock bore and stroke, fully balanced 3.73 rear, built 4l60e,

[jason k]

here is my tune and a couple scans

[MikeOD]

I ran that exact cam for YEARS in my LT1 cars. 34-36 degrees at full throttle...10 more at cruise. Lambda ~0.87-0.85 (set the EQ ratio in the PE table to 1.148-1.176 and then tune for as low % error as you can get) with probably net you the best power, I think you'll find it at 0.87, no need for more fuel in there...you're commanding it to lambda 0.75 now, which is WAY too rich.

By running with the timing that low and that much fuel the thing must suck. You're probably 60-80 hp away from where it can/should be. I used to idle that cam around 800 RPM...but it'll probably idle lower than that if you really want it to...commanding 650 seems like you probably have crappy vacuum, and could be where the misfire codes are coming from.

[jason k]

That's actually great to hear mostly because I think the car hauls ass right now. Lol. I will try that's out as soon as I build another trans for it. Blew that again last weekend, Stripped another oil pump drive day before too. Thank you for your advice. Probably be a couple more weeks before I can try it out. I'm building a turbo 400 for it Tired of the 4l60 nonsense

[MikeOD]

Realistically, I think if you can achieve 360-370RWHP with that cam and a stock bottom end LT1...I think you're doing well...but that'd be through a stick shift. Through the auto, maybe suck 15-20 hp away from that number. And that's including your ported heads.

I hope you beat it though!!! At least send me a PM or post here or something when you work on it again.

I didn't look through the logs...if you think it's hauling ass now, it could very well be achieving something in the air/fuel I recommended and spark close to the 34-36 degrees the engine probably wants...but based on the tune, I don't think it is.

[540gts]

My set up is bout like your, is your IAT still in the stock elbow or have you moved it? or was it 65 degrees out? thanks

[jason k]

My set up is bout like your, is your IAT still in the stock elbow or have you moved it? or was it 65 degrees out? thanks

It is relocated to the k&n air box/ tube but yes it was also a night run and it was pretty cool out. And yes I've looked at ur tune and read most of your posts How's your trans doing? I got mine shifting awesome with some help from a couple guys here but I gave up on mine and I'm building a 400 for it right now, just can't keep a 4l60 together.

[jason k]

Realistically, I think if you can achieve 360-370RWHP with that cam and a stock bottom end LT1...I think you're doing well...but that'd be through a stick shift. Through the auto, maybe suck 15-20 hp away from that number. And that's including your ported heads.

I hope you beat it though!!! At least send me a PM or post here or something when you work on it again.

I didn't look through the logs...if you think it's hauling ass now, it could very well be achieving something in the air/fuel I recommended and spark close to the 34-36 degrees the engine probably wants...but based on the tune, I don't think it is.

Will do. Thanks for the help. The trans should be ready soon, then custom driveshaft time and back to tearing up oil pump drives!!!! Lol