2004

 

So yeah, same P59 PCM as me then.

 

Roger that! I’m not going to go crazy with it, but even a 40%-50% improvement would be amazing. Is that a reasonable goal while maintaining good drivability around town?

 

My throttle is still nowhere linear, but response is vastly improved. I feel I'm at the point of diminishing returns. Mine's a cruiser/fun car, not a race car, so I don't want to hurt its manners any. I can try and post up the stock map later. One look and it'll be very apparent why the throttle response is so lethargic.

 

The answer is yes. The tune will recalibrate throttle response in lower RPMs, reduce torque management, and if A4 firm up and extend transmission shift points.

And if you've made changes even as simple as a Vararam CAI it will maximize the benefit of the increased air coming in. You may only see a 10rwhp increase in an otherwise stock C5 but the car will be a totally different (improved) driving experience especially at low speed launches.

 

Here's the stock throttle map off of my car. I couldn't capture the whole thing, but at 93% (next highest load cell not pictured) it jumps to 100%. A linear throttle would have a 45 degree line so you can see how much throttle area is lost under the curve on the picture.

Edit: I can see now that the labels aren't present on the first pic. Top row is kpa, ignore that as they're all the same so for all intents and purposes this is a 2D map. Far left grey column is throttle input, values in green are what you get. So for example you give a quarter throttle input and get 3.8% of that in return. By half you're getting a whopping 15.1%, 75% input is still only 46.8%, then it shoots up to WOT from there.

 

This was a thing with cable throttles they would try some linkage tricks to get all that sensitivity at low throttle. They got it just right on the c5 and now people whine it doesn't accidentally jackrabbit start like an 85-hp kia.

From http://www.thinkfastbook.com (you don't even need the book, this is so basic it's right there online)


I'll wait to see some lap times showing a c5 with one of these throttle boxes is faster than stock on a road course. Or solicit comments from passengers and see how they like it

 

Throttle response is subjective and I personally didn't like needing to give it a half-plus stab to move. Nobody said it would be faster or slower, that's not what this thread is about. Besides, your table doesn't even show the same data as the one I posted, they're apples and oranges.

 

This info is mind boggling…

From my neophyte tuning point of view, I see the stock table indicate a serious lack of throttle control, or perhaps throttle input. Whatever, It sucks.

I never had a problem driving some pretty radical big blocks on the street, so I feel confident I can conquer a 350hp daily driver.

Im not going to roast the tires, but right now it feels like there’s a nerf ball under the gas pedal. I’d sure like to gather some feedback on finding the sweet spot in the table, so I don’t do what some GM engineer thought was beyond the drivetrains safe range.

 

They stuck a cable throttle on the Camaros and all they did fine. But like I said, my throttle is nowhere even close to linear. It's still very progressive. I don't think I'd want it linear on this car. My trucks sure, let them max out airflow with some input and leave the rest to force a downshift. What I've been wanting to find is how to calculate open throttle area percentage vs a given throttle position as a butterfly throttle will initially produce more with less, then peter out as it approaches WOT which is why ETC is progressive in the first place. I suspect the chart posted above uses some of that math.

 

Something to keep in mind for tuning these is that wide open throttle does not equate response for lower rpms. By managing the throttle opening a higher velocity (smaller opening) at low rpm and low hp output will provide superior feeling and more responsive from the engine than simply dumping a "wide open throttle" despite the pressure in the intake manifold being identical either way.

In other words, pressure is not flow, nor is it velocity. High velocity tuning efforts for same-flow and same-pressure situations are almost always superior when using lower throttle positions. Consider a 180cc classic head runner vs 220cc - obviously 220cc flows more on the big end but why does the 180cc version out perform the 220cc at low rpms and provide superior cylinder fill and low speed operation? Velocity at the same pressure is higher due to smaller opening.

 

Very interesting stuff. However a question comes to mind. Why do drag race cars come from the line at full throttle? For example, I had a 472 CI engine, 400 cfm heads, topped by two 1050 Holley carbs and immediate WOT resulted in near instantaneous acceleration. Zero bog.

Now I’m not disputing the examples you gave, as they contain factual information. Still, it’s not all the information. In other words, efficiency is not always the best evidence of performance.

Certainly there is a sweet spot allowing control at low speed, but it would be fun to regulate throttle with our minds, and not just with the computer controlled nerf ball under the pedal.

 

Drag cars do not go WOT when the light turns green, at least not a real drag car. A real drag car is programmed on a 2-step or some kind of limiter which allows the engine to build boost and momentum of internal rotating parts, and loads the vehicle chassis some way different than it is loaded at rest, and there is also a somewhat linear throughput for airflow (a peaking of airflow setting prior to launching for the tire & traction configuration) before the vehicle actually begins to move, thus there is no need for low speed response, dynamical or velocity based tuning efforts since those are eliminated in affect by the 'drag launch' setting which in essence creates a template for reproducible results. And then the best of those drag cars will change very little from start to finish, for example leave at high RPM and stay at high RPM for the entire race and never leave the high RPM when setup properly. They have no use or need for low speed or low RPM programming, response, etc... For example the turbo size and spool character is negligible when you spool on a 2-step with nitrous and a Trans brake, the response of the turbo and engine becomes insignificant.

Now, the term 'bog' isn't really applicable to velocity based tuning. The torque output differential- the rate of change of torque- is what we are really discussing. "bog" simply means improperly tuned. You can tune an engine to not 'bog' by going WOT but that does not mean the airflow throughput dynamical effort (the way the airflow changes with time in terms of resonance tuning 'water hammer' within the intake system and reversion affect of low rpm in leiu of long camshaft duration) is going to be optimal or provide best torque or airflow throughput. These need to be tested empirically, in general, and then set using the results of a dynometer or some measurement tool, whether its a dyno or a ET adjustment or lap progress or RATE based tuning of dRPM for corners or whatever... specific to an application. As not all apps are drag racing.

To give an example for tuning of rate vs the term 'bog' further let us review the influence of fuel cling. There is always some fuel cling to intake passageways which has an influence on engine tuning. When the pressure drops or increases suddenly the tuning of the ECU must take into account sudden vaporization or condensation of fuel as part of its rate based tuning for airflow changes made at low rates of dRPM (low rates of change of RPM where throttle is moved suddenly). This tuning is only FUEL based tuning- in other words, it has nothing to do with our airflow model or the rate of change of airflow throughput of the engine. By properly adjusting the fuel cling, boiling time, 'accel pump' function, etc... we can create ideal Air Fuel ratios but this will not improve our dynamical airflow model the way an adjustment of velocity or helmholtz tuning of intake passageways or exhaust system or camshaft overlap etc.... it is simply a measure of whether the fuel aspects are properly dialed in and cannot affect or alter the airflow model once tuned properly. In other words, it may 'bog' before being properly tuned for fuel, then no longer 'bog' with good fuel tuning, and yet we have not discovered or tuned our dynamical airflow rate model despite having an engine which no longer bogs- there is still something left on the table in terms of velocity tuning or intake throughput tuning efforts.

 

You must have worked hard on that essay, but way too many syllables to keep me glued in. Sorry. I mean that.

 

This died with the carburetor. But I know it's falling on deaf ears.

 

Not so much deaf ears as over taxed ears.. Alot goin on here. 😐

 

Oh you mean like why we don't put a 1000CFM carb on a 600CFM engine? Like why they make smaller carbs at all when a one-size-fits-all enormous version that can flow the most possible air at all times seems ideal? Or why gigantic throttle bodies on fuel infected engines are a no-no... huh Its been in front of us the entire time

 

Automatic transmissions... Well yeah... but one can recognize the cars lazy peddle, out of gear, stopped, and a fast ankle/foot rotation on the accelerator, with car AT REST.... Question.. Is it the auto transmission only that limits engine speed (rpm) at rest and in NEUTRAL? Seems so.. Y'all made knowledgeable understandable answers. the question that I struggle with ... Mash the throttle, at rest, with your LS1 w/automatic transmission. There is a time delay from ankle speed to engine speed... Notable comparing it to my partner's Volvo C30 T5.. Seems as every time I drive her Volvo C30 I spin the tires with my Corvette Foot! WOAH!...I'd like her throttle response on my C5!...... Or do I? 🤔

 

airflow controls RPM. Nothing to do with the transmission or gear. You want a higher idle you raise airflow. Timing has an impact but affect due to timing is related to combustion efficiency and cylinder temperature, air temp, etc... hotter engines are more efficient thus extract more energy from fuel require less timing to maintain some idle speed or cruise speed or whatever. E.g. the factory goes through great lengths to insulate airflow and the engine compartment to conserve heat, trapping heat, thereby increasing engine efficiency and improving economy. When you make modifications that extract heat such as hood venting and cold air intake tubes it will have adverse influence on economy and may even lead to airflow distribution, cylinder VE variance, fuel vaporization and carbon coating issues, not just economy related.

 

I'm not sure what the first part of your question is, but there are separate rev limiters for P/N and in gear. In the case of the M6, there are fuel cuts and throttle cuts for each gear. As to throttle response, a torquier motor will also have better response. I don't consider the LS1/LS6 to be particularly torquey, but there is still a noticeable amount of response to be gained with an automatic car with a simple throttle remap. Give the Chuck CoW booster a google, he advertises just that.