How to get a 4.8 off the line if it has an electronic throttle

[chevyman08]

I have a 4.8 and it needs help off the line and it has an electronic throttle. How do i get it to go faster off the line.

[ScarabEpic22]

Post your tune up.

[efizjb]

Chevyman408, everytime I've needed help and posted a tune or log there has been help, but starting multiple threads on the same thing after they've asked for your tune multiple times is gonna wear on everybody, it's a "help me, help you" kind of a thing

You're in the best place for help....

[chevyman08]

ok man

[joecar]

Yes, post your tune... many eyes -> many ideas.

[chevyman08]

Okay, here is my stock tune, is this what you're looking for or would you like the current tune that is loaded in the truck? Please forgive me I'm new to all of this, but I certainly appreciate the help guys. My main concern is of course being able to get some more push right off the line, the high end is great with the current tune. Again, I appreciate the help guys

[BlackGMC]

The current tune would be better... Reason being is because some of the adjustments you made could not be correct (no offense), we are all learning here so, no need to worry about anyone bashing your tune or anything like that..

[chevyman08]

Okay I'll have it on here by tomorrow for sure for you guys to check it out...thanks

[BlackGMC]

Cool, in the mean time you might want to post up some mods/specs on your truck, for example: gears, tire size, headers, intake, etc....

[chevyman08]

The truck has true dual flows, a cold air intake, 265/70/17 tires, throttle body spacer...thats about it

[chevyman08]

O and it has 373 gears

[chevyman08]

Okay, here's my test tune...keep in mind it's all still new to me so don't make fun please haha

[joecar]

Hi CM08,

Looking at your tune file from post #12...

I would set:
- B3616 to 35% across,
- B3618 to AFR 13.0 (EQ 1.13) across,
- D0961, D0962 to 100% across,
- D0926 to 33 mph or less,
- D1108, D1109 to 0.3 s across,
- D0701, D0702 increase slope from middle and up,
- D0703 increase at left (no flat spot),

If you want to run fully open loop then set B4206 to disable.

Also post some logs.

How is shift feel at various speeds...?

Hey, we're all newbies at some time or other, so no one here will make fun of you, they're all good people...:cheers:

Cheers
Joe
:cheers:

[chevyman08]

Okay guys thanks for the help, I'll give those adjustments a shot, in the meantime here's a 0-60 log from the current tune that was loaded in the ECM in case you're curious.

As for the feel of the shift at various RPM's it doesn't seem too bad, pretty firm when it kicks down in the higher RPM range, 1st to 2nd felt a little spongy though

[ScarabEpic22]

Hey man, Ive taken Joe's advice and a little of my own trans experience and thrown this .tun together for ya. Its not much, and its a hybrid of your stock, modified and joecar's ideas plus mine but it should help you in the right direction.

[chevyman08]

Ok we tried all of joe's ideas and I still really need help in the low end range

[joecar]

From your log in post #14, the HO2Sx1 voltages indicate you are lean at WOT thruout the range.

You are running OLSD, so you will need to increase your B0101 table.

To do this you will need a wideband to see by how much.

[chevyman08]

Can we just change the table and guesstimate how much...ya know trial and error?

[joecar]

Try raising it 3% and see how it goes.

[joecar]

Where can he get a wideband and what is the best price...?

[chevyman08]

IS there anyway to change from an ETC to a cable throttle

[dfe1]

IS there anyway to change from an ETC to a cable throttle
Easiest way is to buy an older truck. Why would you want to do that? ETC is far superior to cable because it provides so much more control. You can tweak the relationship between pedal position and actual throttle position, for better feel, but wide open throttle is wide open throttle-- regardless of the throttle control method, you can't get more than 100% throttle position. Seems like you may be expecting too much from a 4.8-liter engine in a 5,000 pound truck with (I assume) a stock torque converter.

[chevyman08]

No i am not expecting to much. When you floor it off the line it seeems as though it doesn't go to wide open throttle. I beleive most of my problem is my torque converter

[chevyman08]

If i make my injectors work 100 percent will that help my performance or is it better if they run about 50

[efizjb]

Injector duty cycle of 100% does not equate to more power, 100% means they can not flow any more fuel, they are open full or say "static". It's how much they are flowing vs what the max capability of the injector is.

[chevyman08]

out of which table does most torque come from

[joecar]

Collectively from these tables working together:
VE B0101, MAF B5001, IFR B4001, CFOL B3605, PE B3618, HO spark B5913.

[dc_justin]

out of which table does most torque come from
As long as fueling is in a certain range, the power is in the timing.

Your 4.8 isn't being hindered by the tune, it's mechanically limited. RCSBs do alright, but ECSBs and Tahoes with the 4.8L are a bit overweight.

If you post up your most recent tune, I'll give you a few pointers.

Justin

Edit: If you want any reasonable level of fuel economy, I'd suggest having table B3616 be around 75% throttle, rather than 35%. At 35%, you'll be in PE mode just outside of cruising.

[LBZoom]

Here is Chevyman08's currently loaded tune guys :cheers:

[chevyman08]

Anyone?

[chevyman08]

Someone please help wtih the tune

[joecar]

It looks to me like your timing B5913 is low... you can increase timing to 24* at peak g/cyl...

altho you have to verify that it does not knock when you do this.

I can't remember... do you have a wideband...?

What is the compression ratio of the 4.8...?

[chevyman08]

No I don't have a wideband but I do intend to get one. How Do I verify that it does not knock.

[joecar]

Audible knock can be heard by ear.

Audible/Inaudible knock can be detected by the PCM (displayed as knock retard).

Either method is not foolproof and may not always work.

[chevyman08]

Is it danderous to the motor?

[chevyman08]

And the compression ratio is 9.50

[chevyman08]

so where do I need to add this timing and how much is safe?

[joecar]

B5913 is the high-octane spark timing table.

You need to log DYNCYLAIR_DMA since this is one of the indexes into that table (see how that table says it's a "link" pid).

About 29* total (absolute) advance would be considered the upper limit... but it depends on the motor and whether it wants to ping.

Yes, knock is dangerous... it is responsible for holed/melted pistons, broken/missing ring-lands, blown head gaskets, fuzed/missing spark plug tips... and more...

At 9.5 you can run on 87 or 89 and not get any knock which means you can advance the timing which improves efficiency/power/torque... but pay close attention to it (and log KR)...

Also, combustion efficiency increases [exponentially] as the static CR increases... you won't make as much torque at 9.5 as you could at 10 or 11... this is where a blower comes in handy (it increases the cylinder air fill thereby increasing the dynamic CR)... but if you want to make 300+ HP NA (no blower) then you need to get the CR to at least 10 (which has the side effect of increasing the "ability" to knock... which is why 91/93 is recommended).

Whatever yo do, pay attention and make sure it does not knock...

Disclaimer: If that doesn't make sense or you are not familiar with this, then leave it alone.

It is not easy to tune someone else's spark advance and/or fueling remotely, which is why people aren't jumping on it.

[chevyman08]

OK but if I dont mess with the timing im not going to get any gains?

[joecar]

Fueling needs to be right... and then timing.

[LBZoom]

What do you recommend for checking the compression ratio after modifications are made?