No bottom end power 5.3L

[leamangriffin]

Hi all,

I have a 98 tahoe with a 5.3 swap. 4l60E trans
Mods are Pacesetter Longtubes, Hot Air intake, No Cats, 3" dual Exhaust back to 2 Thrush Welded mufflers 2.5" out to turndowns.
E Fans, and a local shop put a "Base Tune" in it. Basically he said he upped the enrichment, took out the torque management, governor vats etc.. I dont have a wideband yet so he couldnt do much more he said.

My problem is the truck feels like North Korea under 2k rpms. No power lol. Pulls strong in the mid to upper range. I know headers and a free flowing exhaust will rob some low end power, but it feels excessive.
it wont spin the tires if i floor it from a stop in the rain. it wont spin if I powerbrake it (which I dont like to do but i tried it to confirm the lack of power.)

No CEL light
I get occasional 02 CELS but it seems it is because I have a "sluggish" o2. it cycles fine sometimes, and behind other times.

Here is a copy of my tune.
I havent done any logs with it but I can if it will help diagnose..
no tq mngt 1.3 pe ramp in plus1deg timing no neg no burst knock.hpt

[jaydubb71]

Ive only been using HPT for a year and a half so Im no expert...

Looking at your tune, you only have ONE DEGREE OFF ILDE. Now, without a log, its hard to tell what spark advance cell youre hitting when you floor the truck but at the higher airflow points and RPM points, youre getting some timing...

Log the truck and post your log. You might need to log with 2.24. It appears this tune file was created with 2.25...

[leamangriffin]

ok i did 2 logs...

first is from a dead stop full throttle through first and most of second gear
Attachment 53689

Second is a 30mph roll full throttle
Attachment 53690

Here is my config file
leaman tahoe1.cfg

[jaydubb71]

Cant get the log. Post it the same way you posted the HPT file. Upload it to the site...

[leamangriffin]

30 roll.hplfull throttle from stop.hpl

[jaydubb71]

Hey. I took a look at your log and as I suspected from looking at your tune file, you have no timing down low (full throttle from stop). Youre right in your peak timing area in your 30 roll log.

Take a look at the log (full throttle from stop) and see the cell area that your in at around 1600-1800 RPM. Add some timing in and around that area. Watch your knock retard and make sure you dont have detonation as you add timing. That should help your low end power woes.

[leamangriffin]

I understand what you are suggesting.. but could you be a little more descriptive on the actual procedure? And thanks for your help. Also.. why only in that RPM range? Is it not as safe to add timing below the 1600 rpm mark?

[leamangriffin]

ok i looked at the advance tables and compared them to the log file. I added 1 degree to the blocks in that area and I will try to log another pull and see what happens.. Ill add 1 deg at a time until i get any knock, then back out the block that seemed to hit when the knock occured. Also, everything I am doing is in the High octane table. I havent touched the low octane table. after some searching i found that the ecm uses both... can I just copy my entire high octane table to the low octane table? I always run 93 octane.

[Hotwire]

ok i looked at the advance tables and compared them to the log file. I added 1 degree to the blocks in that area and I will try to log another pull and see what happens.. Ill add 1 deg at a time until i get any knock, then back out the block that seemed to hit when the knock occured. Also, everything I am doing is in the High octane table. I havent touched the low octane table. after some searching i found that the ecm uses both... can I just copy my entire high octane table to the low octane table? I always run 93 octane.

Since you're running 93, go to the tune repository and download a stock 2002 camaro SS tune. Compare it to your current tune, copy over ALL the timing tables, base, low octane, high octane, etc. Save the tune as a new name, then upload it to your suburban. You'll be pleasantly surprised.

[jaydubb71]

can I just copy my entire high octane table to the low octane table? I always run 93 octane.

I copy my hi octane table over when Im tuning. Once I get it where I like it, I copy high to low and then hightlight the entire Low table and remove 4 degrees.

[Mods89]

Since you're running 93, go to the tune repository and download a stock 2002 camaro SS tune. Compare it to your current tune, copy over ALL the timing tables, base, low octane, high octane, etc. Save the tune as a new name, then upload it to your suburban. You'll be pleasantly surprised.

Could I do this on a 09 1500? The truck is stock and the thing is a dog under 2500-3k rpms.

[leamangriffin]

Since you're running 93, go to the tune repository and download a stock 2002 camaro SS tune. Compare it to your current tune, copy over ALL the timing tables, base, low octane, high octane, etc. Save the tune as a new name, then upload it to your suburban. You'll be pleasantly surprised.

Ill try that... should I do EVERY table? idle advance, High Octane, low octane, and base IAT spark correction, base ECT spark correction, and max torque timing? I have EGR disabled so EGR timing correction prolly isnt needed...

Edit I looked at an SS tune and there is a huge difference down low in the timing tables.... I like what I see lol... a little leary of copying and changing that much in one swoop, but i guess as long as im not saving over my existing tune..

[5FDP]

Could I do this on a 09 1500? The truck is stock and the thing is a dog under 2500-3k rpms.

Nope.

Two completely different computers and ways of thinking. A gen 3 pcm uses maf and a regular ve table where as your gen 4 pcm uses a maf with virtual ve and likely VVT. Both my 10 and 12 silverado's used VVT. Also the compression ratio's, cylinder heads etc etc are all different.


It's pretty simple to tune a 07+ NNBS truck that is stock, it won't have all the grunt in the world but making them come alive sooner isnt hard.

[nkautz]

It looks very rich up to 3200rpm. You have a blind base tune on it , you need a wideband and a real tune.

[Mods89]

Nope.

Two completely different computers and ways of thinking. A gen 3 pcm uses maf and a regular ve table where as your gen 4 pcm uses a maf with virtual ve and likely VVT. Both my 10 and 12 silverado's used VVT. Also the compression ratio's, cylinder heads etc etc are all different.


It's pretty simple to tune a 07+ NNBS truck that is stock, it won't have all the grunt in the world but making them come alive sooner isnt hard.

alright sweet. I dont believe my truck has VVT. I just wasnt sure where to start tuning my truck. lol If I could just toss the timing tables out of a f body it would be easy. haha

[leamangriffin]

ok i did a few changes to the tune and did another full throttle from a stop log... any thoughts? It feels better, but not where it should be i dont think. I put the Camaro SS advance tables in it... funny thing they made me significant gains in the upper rpm range on my butt dyno... Pulls alot stronger in the upper rpms now... maybe that is making me not notice the lower rpms... anyhoo. I plan on installing a cam and wideband soon so I will be waiting till then to "officially" have someone tune it. I just would like to see if there are any gains to be had where i sit now. Also I had problems a while back with IATs climbing super high... then out of the blue it stopped, now I am noticing they are still getting pretty high... I have a fleabay super hot air intake.. Does heat wrapping it help alot?

full throttle ater timing changes.hpl
no tq mngt 1.3 pe ramp in Camaro SS timing no neg no burst plus1 low.hpt
leaman tahoe1.cfg

[Fast4.7]

Upping the enrichment is dumb IMO. The LS tunes run rich to start with and even richer after headers. The 5.3 will never have the low-end power of the 5.7 that came in the Tahoe. If you are using the 98 trans, I would put atleast a 2,600-2,800 rpm converter in place of the ~1,400 rpm stall converter that came in the 350 truck.

[Fast4.7]

One other thing that happened to me with my 0411 swapped L31 when I put headers on it. I started hitting the torque limiting values at very low rpm and it would pull a ton of timing out of the engine and fall on its face.

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