Suggestions for curing sluggish throttle response

[Joe_G]

I have a G5x3 cam. I purchased a mail order tune and have tweaked it myself quite a bit and have the car tuned pretty sharply both on the dyno and around town driving. LTFT's are -1 to +2 in all of the idling and cruising cells, and it starts, idles and cruises very well - almost like stock.

Overall I'm thrilled with my tune except for the throttle response. It's sluggish when you hit the gas. You have to hit the gas pretty hard to get it to rev up and then it revs slowly. I wouldn't care except that I like to heel and toe downshift and the sluggishness makes it hard to do.

I've attached couple of scans - one, a cruise to the local 1/8 mile track and a run on the 1/8th mile.

I sure would appreciate any advice on how to make the car's throttle response more "snappy".

[softy91]

I took a look at both of your files and saw the same issues on both files.

2050 RPMs were your staring places on both. You are too lean from 2050 to about 5300. I would also expect to see the same pattern down to idle. You appear to be 5 to 7 % lean so look at the individual cells and add fuel to the MAF table.

Before you go there you need to pick up your timing I would guess from idle to 3500 rpm.(about the time your cam will stop blowing down) from overlap. When your cylinder preasure comes on, you are getting knock retard. Again if you will pull timing on those cells in the table, your ride should come alive.

Your PE may be richened up some to hold down knock retard where it is happening, but since you don't have that table I can't give you a definite answer. Pull timing and/or add fuel.

Good luck and Warp 10 Always!

Bill

[S2H]

just because there are trims doesnt mean he's lean or rich..it means his vehicle has corrected for a lean or rich condition....

Honestly..all MAF vehicles are sluggish...only way around it is to switch to SD....which is not always easily done on all vehicles

I dont know enough about 2005 vettes to be able to tell you what to do to fix it...but changing the MAF table will not change throttle response in closed loop operation

I dont know if it exists in your car...but you could try to do what some LS1 guys hve done and change where the MAF has control and how much it has control...give more power to the SD calcs...that will crispen up the throttle response a lot

[rian_human]

I have similar mods to you, and I found my throttle response to be almost too sensitive.... The slightest movement of my foot will have my wife complaining about getting whiplash.....
This has been like it since I did the mods. I have used both SD and MAF tuning with pretty similar results..

So, the throttle response you are talking about, is it off idle or while driving? Low or high rpm?

Did you make any adjustments to tables other than VE and MAF?

[Joe_G]

Softy91, thanks for the response, I can try that. Not sure what you meant though, I've got lots of idle time in my posted logs? Also, when I'm idling or cruising the LTFT's are pretty low so I didn't think I'm rich?

Ruin the car is sluggish at dead stop or if I heel and toe downshift - pretty much any time I hit the gas it takes some time to actually rev up. It runs great other than that.

I've added a fair amount of timing, here's my spark table vs. stock. Appreciate further opinions.

[BBA]

I took a look at both of your files and saw the same issues on both files.

2050 RPMs were your staring places on both. You are too lean from 2050 to about 5300. I would also expect to see the same pattern down to idle. You appear to be 5 to 7 % lean so look at the individual cells and add fuel to the MAF table.

Bill

...add to the MAF table


Why? Do it the right way, add to the PE curve that takes a nose dive below 3K RPM. That way you don't hurt low speed economy.


But...to get rid of sluggishness, as well as PE or MAF table adjustment, increase air charge temperature coefficient filter values. In crease the lower 3 or 4 ranges to take about 75% of the difference between one table and the next higher table. This makes an unbeleivably good difference.

[BBA]

just because there are trims doesnt mean he's lean or rich..it means his vehicle has corrected for a lean or rich condition....

Honestly..all MAF vehicles are sluggish...only way around it is to switch to SD....which is not always easily done on all vehicles

I agree SD is the ultimate in response, but... setting the charge temperature filter table is what makes MAF feel like SD. It allows the PCM to calculate new charge temperature values much quicker, kind of taking the MAP to air mass flow lag out of the equation on throttle change.

[Joe_G]

...add to the MAF table


Why? Do it the right way, add to the PE curve that takes a nose dive below 3K RPM. That way you don't hurt low speed economy.


But...to get rid of sluggishness, as well as PE or MAF table adjustment, increase air charge temperature coefficient filter values. In crease the lower 3 or 4 ranges to take about 75% of the difference between one table and the next higher table. This makes an unbeleivably good difference.

Actually, my PE table is tuned to about 12.7 below 3k on the dyno.

Are you suggesting I change the "Cylinder Charge Temperature Coeff vs. Airmass" table? My table was left stock in my mail order tune and I've not changed it.

As another data point,as my car's an 05 I do have a VE table, and that's what I've adjusted from stock to make my mail order tune run well (it was left stock in the mail order tune). Here's the adjustments I made:

VE table 400 800 rows x.65
VE 1200 row x .65
VE table 1600-2800 rows x. 80

Remainder of the VE table is stock. I noticed one day when I flashed my VE table back to stock by mistake my car was REALLY sluggish. I wonder if I should take another 5% out of the table below 2800 where the car still feels a little sluggish? I'm hesitant to do so since my fuel trims are almost spot on.

Appreciate the input guys.

[S2H]

Actually, my PE table is tuned to about 12.7 below 3k on the dyno.

Are you suggesting I change the "Cylinder Charge Temperature Coeff vs. Airmass" table? My table was left stock in my mail order tune and I've not changed it.

As another data point,as my car's an 05 I do have a VE table, and that's what I've adjusted from stock to make my mail order tune run well (it was left stock in the mail order tune). Here's the adjustments I made:

VE table 400 800 rows x.65
VE 1200 row x .65
VE table 1600-2800 rows x. 80

Remainder of the VE table is stock. I noticed one day when I flashed my VE table back to stock by mistake my car was REALLY sluggish. I wonder if I should take another 5% out of the table below 2800 where the car still feels a little sluggish? I'm hesitant to do so since my fuel trims are almost spot on.

Appreciate the input guys.

you cant just guess at a ve table..you have to actually tune it using your wideband and using AFR error

[5_Liter_Eater]

But...to get rid of sluggishness, as well as PE or MAF table adjustment, increase air charge temperature coefficient filter values. In crease the lower 3 or 4 ranges to take about 75% of the difference between one table and the next higher table. This makes an unbeleivably good difference.

Can you explain this a little more? What is this actually doing?

[Joe_G]

you cant just guess at a ve table..you have to actually tune it using your wideband and using AFR error

Yea therein lies the problem. I have PE tuned with the wideband on the dyno but I made a HUGE mistake by buying the base cord that won't take the wideband. So I don't have one.

I was thinking since my LTFT's and STFT's are pretty close to 0 that I had the VE and the MAF pretty closely tuned? The car runs absolutely great except for the relatively sluggish throttle response. And please note, I can live with it, but when Mike Norris first tuned my car with LS2 edit a year ago the throttle response was razor sharp (bolt on only). I'd like to have that back again.

I guess I could fail the MAF and do the Ls1 instructions to tune the VE but I thought I'd read here that technique doesn't really work too well for the LS2 so I didn't want to waste the time.

I do appreciate all the advice though as I'm a newbie.

[BBA]

Can you explain this a little more? What is this actually doing?

Yep, I can.

I am talking about the table under: Engine>Airflow>General Airflow>Cylinder Charge Temperature>Filter

The description given is: This table determines the rate at which the temperature moves to the new bias temperature. At low airflows the termperature change is slower than at high airflows.

What increasing values in this table effects in reality: "Allows cylinder charge temperature changes to be calculated at a faster speed, thereby allowing the computer to calculate the proper AFR quicker."

At low RPM's, the stock calculations are filtered so much the new calculations take too long, hence the lag in throttle response. This is somewhat made up by the transient fueling parameters (which in my opinion dump too much fuel to the point of blowing black out the tailpipe when you rev the engine from low speeds to high speeds).

If you really want to dial in throttle response to get rid of the AFR over/undershoot, set the charge temp filter values higher and reduce the transient fuel maximum mass, transient map filter and enable delay. Using a quick reacting O2 sensor (as in the one's dyno's use) you can dial it in near perfect, almost to the point it will act like a SD tune but with better control under all atmospheric conditions) Of course I don't have a dyno or good wideband at my disposal just yet, so I tuned mine by SOTP and observing exhaust emmissions of black smoke (The old fashioned way).


I'll tell you: This is where drivability is greatly improved, and all around, in a BIG WAY. (But don't take my word for it, try it yourself).

[Joe_G]

Yep, I can.

I am talking about the table under: Engine>Airflow>General Airflow>Cylinder Charge Temperature>Filter

The description given is: This table determines the rate at which the temperature moves to the new bias temperature. At low airflows the termperature change is slower than at high airflows.

What increasing values in this table effects in reality: "Allows cylinder charge temperature changes to be calculated at a faster speed, thereby allowing the computer to calculate the proper AFR quicker."

At low RPM's, the stock calculations are filtered so much the new calculations take too long, hence the lag in throttle response. This is somewhat made up by the transient fueling parameters (which in my opinion dump too much fuel to the point of blowing black out the tailpipe when you rev the engine from low speeds to high speeds).

If you really want to dial in throttle response to get rid of the AFR over/undershoot, set the charge temp filter values higher and reduce the transient fuel maximum mass, transient map filter and enable delay. Using a quick reacting O2 sensor (as in the one's dyno's use) you can dial it in near perfect, almost to the point it will act like a SD tune but with better control under all atmospheric conditions) Of course I don't have a dyno or good wideband at my disposal just yet, so I tuned mine by SOTP and observing exhaust emmissions of black smoke (The old fashioned way).


I'll tell you: This is where drivability is greatly improved, and all around, in a BIG WAY. (But don't take my word for it, try it yourself).

Wow thanks for taking the time to post all of this. I've never read anything along these lines nor have I seen anyone else adjust this, but it sounds on-point and I'm going to try it.

Any advice on how much to adjust these things? 10%? 50%?

By the way, I'll prove your point here - check out my car on the dyno - it puffs a ton of black smoke before it goes to PE. You have to sit through me demonstrating my cutouts to see it. The second car on the dyno is my buddy's 403, I don't have a FAST.



Also, on my dyno sheet you can see it going way rich before going to PE (this sheet shows stock, bolt on only, cam only):

[5_Liter_Eater]

Wow thanks for taking the time to post all of this. I've never read anything along these lines nor have I seen anyone else adjust this, but it sounds on-point and I'm going to try it.

Any advice on how much to adjust these things? 10%? 50%?

Ditto. None of these tables are intuative to me at all.

[kenny c]

Ditto. None of these tables are intuative to me at all.

Caught my attention too!

[deanm11]

Caught my attention too!

Bill- it is also confusing to me that the figures in your bias table (you sent me your trailblazer tune) are way lower than the stock values in vettes, gtos. The values in the vette/gto tables are close to 0.2, where yours are closer to 0.1. Hard to understand how you making small changes near 0.1 can have a big effect when our figures are so much different to start with. Thanks for the thoughts though and I may try a bit of your ideas on the transient fuel.

[BBA]

Bill- it is also confusing to me that the figures in your bias table (you sent me your trailblazer tune) are way lower than the stock values in vettes, gtos. The values in the vette/gto tables are close to 0.2, where yours are closer to 0.1. Hard to understand how you making small changes near 0.1 can have a big effect when our figures are so much different to start with. Thanks for the thoughts though and I may try a bit of your ideas on the transient fuel.

I thought the same about the C6 I did, but I still adjusted the tables to make up about 50-75% of the difference from one table to the next for the 4 lower tables and man what a difference it made.

Same with the 2001 Z06 I did. It's amazing how much different these motors run when they actually respond to the throttle.

I think the tune between the TBSS and car LS2's hae vastly different parameter settings, but the same tweaks work on both.

[deanm11]

I thought the same about the C6 I did, but I still adjusted the tables to make up about 50-75% of the difference from one table to the next for the 4 lower tables and man what a difference it made.

Same with the 2001 Z06 I did. It's amazing how much different these motors run when they actually respond to the throttle.

I think the tune between the TBSS and car LS2's hae vastly different parameter settings, but the same tweaks work on both.

Thanks. I am trying 75% in the lowest 4 cells. (75% of the way to what the next cell originally was).

[Joe_G]

Yep, I can.

I am talking about the table under: Engine>Airflow>General Airflow>Cylinder Charge Temperature>Filter

The description given is: This table determines the rate at which the temperature moves to the new bias temperature. At low airflows the termperature change is slower than at high airflows.

What increasing values in this table effects in reality: "Allows cylinder charge temperature changes to be calculated at a faster speed, thereby allowing the computer to calculate the proper AFR quicker."

If you really want to dial in throttle response to get rid of the AFR over/undershoot, set the charge temp filter values higher and reduce the transient fuel maximum mass, transient map filter and enable delay.

I'll tell you: This is where drivability is greatly improved, and all around, in a BIG WAY. (But don't take my word for it, try it yourself).

BBA, any guidance on what you've changed?

1.

Engine>Airflow>General Airflow>Cylinder Charge Temperature>Filter set the charge temp filter values higher.

(g/sec)

Labels 0 16 32 48 64 80 96 112 126
Filter
Coeff .1871 .2035 .2199 .2363 .2527 .2691 .2855 .3019 .3182

My table is above, and as you can see the adjacent amounts are less than 10% apart. Minimum is 0 and maximum is 1.0. How much are you changing these values?

2.

and reduce the transient fuel maximum mass

- Mine is set at 2085, the maximum. How much did you reduce yours?

3.

reduce transient map filter

- Help says "Filter coefficient for the filtered MAP calculation." Mine's at .25, min is 0 and max is 1.0. How much are you reducing it?

4.

reduce enable delay

- Help says "Transient fuel will not enable until this many crank reference pulses are detected" Mine's at 56, min is 0 max is 65535. How much are you reducing it?

Appreciate learning from your experience!

[BBA]

These changes made a nice difference to me. I may try a little higher on the filter table values next time I play with it.