hesitation/delay at low rpm with quick and big change in tps

[steve40]

i'm confused if this is something in the engine tune, or if the trans is slow to react.

in the red boxed area, when going wot, you can see what feels like a delay in reaction by the engine, for a few seconds it feels like its coasting before it decides to wake up.....any ideas on where to look?

[Jetmech442]

Just looking at the pic you provided(thanks btw), it looks like your under quiet a bit of engine load before you even go wot. At 2100rpm, 21%throttle and 30ish mph, I would think Map should be more around 40kPa(depending on engine goodies ).

From what i can see, you go appropriately rich (can't tell the value), timing stays around 25.

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[joecar]

Your engine is under huge load, or you have an air leak into intake manifold.

[joecar]

( logging too many pid channels, you can get fastest update/sample rate with 24 or less pid channels ( see bottom of PIDs tab ) )

[steve40]

Just so I know what I'm looking for. How do you know how loaded the engine is?

Could it be that I have a decent sized cam with a stock truck 4l80e converter?

I'd have to check the intake over for any leaks

[Jetmech442]

I that pic, right before you go wot, your map is around 80kpa.to me at least ,that is a loaded engine, but your throttle blade is barely cracked open at 21%.

How big a cam is big? And are you running a bigger throttle body, injectors.. Etc?

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[joecar]

What are you cams specs @ 0.050" (intdur/exhdur lsa adv)...?

[joecar]

Usually bigger cams will raise idle MAP to around 60-70 kPa.

[steve40]

cam is 227/238 .613/.586 114 lsa

tick performance spec'd the cam. they suggested a 3200ish converter

[Jetmech442]

I'm running a 6.0l lq9 with a228 for both lobes. When I get home I can share my logs so you have something to compare to, if that would help.

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[steve40]

I'm running a 6.0l lq9 with a228 for both lobes. When I get home I can share my logs so you have something to compare to, if that would help.

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yes please, i'd like to take a look at it.

this is also a lq9 bottom end with ls3 heads and intake. i transplanted this motor from another car, i have an old idle log from it....it was in the 65kpa area at idle. even at the beginning of this log when the car was idling, it's in the same range.

[Jetmech442]

HeySteve40,
so mine is a stock head, LS6intake(should be same performance as truck intake), and I forgot to mention my cam is on a 114LSA as well.

You can see that I idle at 45kPa, and when cruising in the same range(ish) as you, I'm still around 45kPa, but when I go WOT it hits 95kPA. This is why I think its weird your MAP is high in the cruise range, however since you idle around 65kPA, maybe that 20 degree delta is appropriate? Sorry, I'm not entirely sure if it scales like that, just trying to put some thoughts out there, maybe someone else with a different configuration can let us know what kPA they cruise at....

Also, at 5300 rpm, you pull 294 g/s (from MAF sensor), at the same rpm I pull almost exactly that same amount. I'm thinking with LS3 heads /intake(what I originally wanted to do but ran out of cash), I would think your combo would consume more air. This is speculation on my part,I just want to make sure your confident the cam/rockers..etc were installed correctly and no vacuum leaks.

This also may entirely be a trans issue, of which I'm no help at all. :)

Edit: actually, when I was performing CALC.Vet I was using the brakes to load up part throttle areas, this owul give me the 20-80% throttle areas but also the higher map ranges. perhaps your trans is loading your engine at part throttle for some reason?

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[steve40]

i checked the vacuum at idle, i'm between 16 to 17" vacuum.

i worked around the shift points on the trans and i think i got it a bit better. it still feels sluggish to respond to wot. i left a message with the guys that do the trans controller....it's separate for the pcm. while waiting, i'm trying to hunt down the stock harness to try it from the pcm.