My K1500 DD Tow Pig

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OutlawDrifter

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I can set the limiter wherever I want.



That's bass ackwards. My Z ought to be peaking around 6000 and without even data logging it I bet it's fastest shifted in the 6600-6800 range because it just hangs on and on. It feels flat behind the wheel, but that's because the tidal wave is over. I'd bumped the rev cut years ago from 6600-6900. But this is about my truck in this thread. I'll head out for a log in a bit and see how it likes being shifted 5400-5500.

No argument there. Short shifted at the track once and then just kind of mailed it in from there thinking it was a bad run...picked up 2mph, haha. Torque curve on this setup is awesome pulls like a freight train from 2500 on up.


I'll bet that huffer is definitely carrying it further. But probably falls of pretty quickly.
 

Supercharged111

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I get the point, but there is a non-arbitrary limit.

Your point actually is my point.

No argument there. Short shifted at the track once and then just kind of mailed it in from there thinking it was a bad run...picked up 2mph, haha. Torque curve on this setup is awesome pulls like a freight train from 2500 on up.


I'll bet that huffer is definitely carrying it further. But probably falls of pretty quickly.

I did just the opposite in a supercharged Corolla. Figured I ought to be shifting at 7200 with stock cams. Was out on a tiny course doing timed 150 meter runs and found a consistent chunk of time shifting at 7700 vs 7200. Went back and forth to confirm. That is so weird with your scenario as the mph does not lie.

I agree this truck should fall off peak like a rock, I just have to go more than 50 RPM past it to find it.
 

0xDEADBEEF

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It's transmission dependent (wide vs close gear spacing). Even though the engine output may be falling off, it might still be putting more power to the ground than in a higher gear.
 

Supercharged111

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100% correct. You're just trying to stay in the RPM band with the highest HP. I hate it when folks shift right at peak and preach that as gospel because power is falling off going higher, it falls off both ways!
 

L31MaxExpress

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I decided on my Z06 I wanted to log when hp was falling off to determine my optimum shift point after the cam swap. I'm thinking I want to do the same before the swap as well, I'd love to see the airflow curve before and after. So I figured out how to make a PID that would spit out hp. GM already calculates delivered engine torque. Who cares if it's accurate or not, all I need to know is how fast it's rising and falling to see where the optimum shift points are. I've been using V7.5, but custom PIDs look like witchcraft so I cracked into the V8 software I'd been avoiding using because I didn't feel like remaking all my histograms (which is super easy BTW). As suspected, V8 is a bit more user friendly once you get to know it. The custom PIDs don't require you to have a programming cert. But I was having connectivity issues with the Z06, so I said screw it let's try it on the truck and it worked so I went out for a rip and this is what I got on a 1-2 shift.

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I told myself the numbers didn't matter until it claimed it was cranking out 440# of torque and 362hp here at altitude. Who knows how optimistic those are. Torque peaked from 2800-3400 RPM and HP at 5250. I was commanding a 5200 shift, got a 5300 shift. I'd monkeyed around with that a bit end of last year and kept over/undershooting my target no matter what I did with the mph and RPM points. I'd had the limiter set then at 5400 and would occasionally bounce off of it. I bumped it by 200 up to 5400, we'll see if it shifts there or closer to 5500 and also how the hp is falling off up there. I'm curious @L31MaxExpress didn't you run the Ramjet cam with marine intake on a 350 at one point? Curious where yours wanted to be shifted at. Of course the blower could be artificially stringing this along too.

From memory on gasoline after I upgraded the valve springs, it peaked about 5,100 rpm and held decent power up to about 5,600ish. On E85 it had a beefier torque curve and made peak power about 4,900 rpm but it was still making more power all the way out at the shift point so shift points were unchanged. Prior to replacing the valve springs it fell off by 30-40 hp at the tires between 5,150 and 5,350 rpm. Before the spring upgrade I was shifting at 5,100ish because it just felt like it fell on its face there. After I was shifting about 5,300 rpm, I figured out it was quicker grabbing another gear and getting back to where it was making torque. I was moving about 280 gms/sec of airflow @ 5,200 at 92ish KPA MAP.

Keep in mind that mine had 906s with 2.02/1.60 valves, fairly stiff Pac1218 beehives and non self aligning 1.7 rockers with guideplates and hardened pushrods on it, so it may have had the torque and hp peak skewed a few hundred rpm higher than you would expect with a bone stock vortec head and the factory slinky toy valve springs.

I actually have someone in the know that was at GM Powertrain that told me why I was experiencing issues with that cam at higher rpms too. It was designed to purposely float the valves with the stock springs at about 5,300-5,500 rpm to prevent engine damage should a prop come out of the water. If you are not floating the valves by 5,300 with the stock springs consider yourself on the edge and watch for erratic map and maf readings indicating valve float. IIRC the Ramjet 350 tune I have looked at in the past had the limiter at 5,300ish maybe 5,500 but I remember it being less than the 5,600 on the stock Vortecs which I found surprising.
 
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L31MaxExpress

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For your WOT shifting issue, this has always worked for me. Set your WOT/Full Throttle Shift MPH/Speed table to something low. With 3.73s and 30.5" tires my van is set for 1-2 = 25 mph, 2-3 = 55 mph, 3-4 = 75 mph. Do the same for the downshifts. 2-1 = 35 mph, 3-2 = 65 mph, 4-3 = 85 mph. Obviously, you want to look at these next to a gearing calculator to make sure that it is lower than your expected shift points by a good margin, but you get the idea. Then set your WOT/Full Throttle RPM table to where you want it to shift. Mine will overshoot for a couple of upshifts, then its right on the money every time. If you have your part-throttle shift table dialed in, you will still get downshifts as the throttle increases despite the WOT table being set to much lower values.
 

Supercharged111

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The tables were that way stock, it would hit the mph way before the RPM. It seems when you put them close together you take away time for the PCM to think about when to begin that shift execution. Tonight I plugged in those 5400 commanded upshifts with a rev limit back to 5600. No change, ****** shifted at 5200. Bumped to 5500 and it immediately ripped off a 5300 upshift. Still no better than I was. I decided to go for a couple more to see if it would trim its way upward and the truck pulled some serious crap on me. It shifted into 2nd at 4500, realized it fukked up, slung back into 1st and upshifted right around 5250. Went for another, same thing. Truck still seems to want more RPM as it's still climbing at 5300. I'm going to run the Bluecat shift tool tomorrow and make sure I don't have any values crossed anywhere. I don't think it's a tune issue though as it's not done this before. I will say the truck is devouring some timing with IATs under 100 degrees. 0 KR and 27.5 degrees of advance at 110kpa here where atmospheric is about 80. I think NA it took 32 tops. This is good truth data, when I start to see KR at higher IATs I can just pull it out of the IAT map instead of the main timing map.
 

L31MaxExpress

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The tables were that way stock, it would hit the mph way before the RPM. It seems when you put them close together you take away time for the PCM to think about when to begin that shift execution. Tonight I plugged in those 5400 commanded upshifts with a rev limit back to 5600. No change, ****** shifted at 5200. Bumped to 5500 and it immediately ripped off a 5300 upshift. Still no better than I was. I decided to go for a couple more to see if it would trim its way upward and the truck pulled some serious crap on me. It shifted into 2nd at 4500, realized it fukked up, slung back into 1st and upshifted right around 5250. Went for another, same thing. Truck still seems to want more RPM as it's still climbing at 5300. I'm going to run the Bluecat shift tool tomorrow and make sure I don't have any values crossed anywhere. I don't think it's a tune issue though as it's not done this before. I will say the truck is devouring some timing with IATs under 100 degrees. 0 KR and 27.5 degrees of advance at 110kpa here where atmospheric is about 80. I think NA it took 32 tops. This is good truth data, when I start to see KR at higher IATs I can just pull it out of the IAT map instead of the main timing map.
That is odd behavior.

My 11:1 383 devours some timing when it is cool outside on 93 octane as well. I finally ran the old E85 out of it and ran it tonight on pump 93. It was at 32* and no signs of detonation. Previously it had a little detonation if I brought the timing in too quickly in hot weather with the Rhoads lifters in it. I pull a fair bit out of the IAT tables as well. If you have not already done this, it would be better for you if you had the 2-bar T-Map. Hook up the IAT inside the T-map rather than the normal IAT. You could pull the actual intake charge temp post supercharger. I know how to calculate the Linear and Offset calculations from the data points Bosch provides with the T-map to work with the GM PCMs.

My predicted/delivered torque output runs low on my engine. Once I had it where the fueling was accurate, I was showing 50-100 ft/lbs less with the 0411 than it was making and the P59 is showing about the same. I ended up beefing up the line pressure map to make sure that I would not slip the clutches in the transmission. I think the issue is that the 383 is making really good BSFC numbers at WOT and thus my VE and MAF values are lower than an engine that has a higher BSFC. I am considering lying to the computer about the injector size, telling it that it has larger injectors than it does to lean it out and increasing the airflow calculations. The lower airflow values jack with alot of other things and I feel if I have to lie to it somewhere, might as well be the injector flow calibration.

This is what I have in mine timing wise now. Seems like alot of timing down low, but it is never under ~1,500 with any real load and the converter instantly flashes 2,000+ if the load is high enough to end up in that 0.60+ gm/cyl range at low rpm. The added timing really makes it come alive off-idle. It also really likes the high idle timing.
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