Questions about tuning come up semi-regularly and I answer them as I get them. When the questions are focused on throttle response, there's often a request for clarification about how a tune compares to another product, like a Pedal Commander.
To get everyone on the same page, there are products out there, like a "Pedal Commander" that increase throttle response. One of the main reasons for getting a tune, especially on a 4.3L V8 Vantage, is to improve throttle response. So why get a tune when a module will do the same thing for 1/10th the price?
The short answer: Because it isn't the same thing. A tune is far more comprehensive than a throttle signal override.
The long answer...
Gas Pedal vs Throttle Body
The gas pedal isn't actually a gas pedal. It's an air pedal. Yes, it's semantics but I'm gonna be petty about it. It's my blog I'll do what I want. Anyway, moving on. You press the "gas" pedal and the throttle body opens to allow more air into the intake manifold (thus, air pedal). More fuel is added to compensate for the extra air, and voila you've got more power.
It's simple enough, but the amount you press the gas pedal isn't the same amount that the throttle body opens - at least, not on modern cars.
Drive-by-Cable vs Drive-by-Wire
Up until sometime in the 90s, cars used drive-by-cable systems. That means a cable physically connected the gas pedal and throttle body. When you pressed the gas pedal, the cable would physically pull the throttle body open, allowing more air into the intake manifold. Sensors in the intake system would read the amount of air coming in and adjust fuel accordingly. (Prior to the sensors, carburetors would add fuel based on the physical movement of air.)
Modern cars use what's called drive-by-wire. This means that a signal is sent electronically via a wire to the throttle body, which then opens according to what that electronic signal is telling it. You press the gas pedal, the computer reads that input, and then sends a signal to the throttle body telling it to open in accordance with how the computer is programmed.
Drive-by-Wire vs Throttle Response
The relationship often is not linear. Let's put that into very round, fictional numbers to make this easy to understand.
Say you press the gas pedal 25% of the way. The computer might tell the throttle body to open only 15% of the way. This is done for a number of reasons: improved fuel efficiency, better emissions, smoother acceleration, and so on. However, it isn't the best for performance.
The amount the throttle body opens gets more equal to gas pedal input as you get further and eventually when you floor the gas pedal, the throttle body is open as much as it can go. It's that lower RPM range that the engine is sluggish to react to throttle inputs.
When I press the gas pedal, I expect the engine to respond accordingly. I wrote a thing about it and you can (should) read that article, so I won't rehash it. The point is that I want throttle response and the factory tune basically "numbs" the signal going from gas pedal to the throttle body at low RPMs.
Throttle Signal Override vs Engine Tuning
The most recent iteration of this question included a reference to a product called "Pedal Commander" so that's going to be the term I use. There are many products like it on the market. I've never use a Pedal Commander so I can't comment on it as a product, or compared to other similar products. I use it as a generic term for the sake of comparison between that type of product and an engine tune. It's like saying "Kleenex" for facial tissue, even if it isn't the Kleenex brand.
A Pedal Commander (and other products like it) change the signal being sent from the gas pedal to the throttle body to make it seem like the pedal is being pushed more than it is, making the throttle body open more for low-input pedal movement. In other words, it takes the slack out of the throttle response by telling the throttle body to open more than the factory tune would otherwise tell it to open.
When that happens, your ECU is reading the signals from various sensors to see how the engine is running. It notices more air being brought into the engine and then responds by increasing fuel flow to maintain a certain air-fuel ratio (AFR). The factory tune is still controlling how the engine runs, but it reacts to how much the throttle body opens, which is at a quicker rate than the factory settings.
An engine tune, like that available from VelocityAP, goes through the actual tune programming and changes it so the throttle body opens more quickly, but the rest of the tune is already expecting it and acting with it, rather than in response to it. When a factory tune is trying to compensate for increased air flow from a Pedal Commander (etc), a new engine tune will adjust the throttle input signal and have the fueling, timing, and other factors already acting in accordance with it.
An engine tune will also change the rest of the computer's programming so you get better AFRs (the factory tune runs very rich), which gives you lower emissions, more power, and better fuel economy in addition to the improved throttle response.
So, in summary, a Pedal Commander (etc) changes one signal (the throttle input) and the factory tune reacts to maintain factory settings. This happens at a quicker rate, thus the improved throttle response, compared to the factory tune. An engine tune, like the one from VelocityAP, changes all the settings (throttle input, fueling, timing, target AFRs, etc) so you get a better overall tune than factory with all the extra benefits, including quicker throttle response.
Redpants Tech Day - Austin 2019
I’ve put together an Event Page for the next Redpants Tech Day! Please take a look to see what’s included and involved, and the pricing for installations to upgrade your Aston Martin’s infotainment system.
I’m about to publish a sign-up form for those of you wanting installations, so keep a look out for that and please contact me if you want some work done! It’s incredibly worthwhile and is one of the best investments you can put into your Aston.
In Other News (GENEVA)
Aston Martin Lagonda debuted three new cars at the Geneva Auto Show this weekend. The first was code named AM RB 003, which is a natural evolution from the Valkyrie hypercar, the second was the Vanquish Vision - a rear-mid engine revolution of the Vanquish, and the third was a full-size SUV to be offered under the Lagonda brand.
I wasn't surprised to see the Vanquish Vision or Lagonda SUV - I predicted both of these vehicles verbatim a year and a half ago based on my observations of the brand, as well as some comments made by CEO Andy Palmer during an event at the British Embassy in Washington DC. The other major predictions I made back then were the return of the DBS and that Aston Martin Lagonda would go public with an IPO, which both happened not too long ago.
The AM RB 003 reveal was only surprising in that it came so soon on the heels of the Valkyrie, which itself was quickly followed up with an up-rated track-only AMR version. The Valkyrie is an ultra-pure design. That is, the body is purely for aerodynamics. The engine is purely for performance, both power and weight. The vehicle is entirely pure in that it's purpose-built for speed without any fluff whatsoever.
It's an overused cliche to say that times change and the world changes with them. It was obvious that AM RB 003 would be a hybrid. The influence of the Valkyrie is clear but it has its own design ethos, which runs true to the way of the world right now: hybridization.
I’m going to try to cover both the AM RB 003 and Lagonda SUV on their own, but this blog post is long-enough as-is so I’ll be stopping here.
In Other Other news
Exterior lighting packages are continuing to ship out. I’ve still got a lot of them to get through, so thank you all for your patience as I get them sent out.
Please don’t hesitate to contact me if you have a pending order, especially if you had a custom invoice as those were handled by someone else and I’m still trying to get that bit of the past unfucked.
In Other Other News News
I’ve got some extra help with packaging and shipping orders, but they’re going out slower because of the extra time it takes to train someone to do it how I want it done. I tend to over-package things to make sure they’re safe during shipment, and I don’t want that to change as things are being packaged by someone else. I go a bit overboard, but I’d rather spend the extra time to make sure your parts arrive safely, and the extra time I spend with wrapping up and labeling individual items makes it easy for you guys to know what you’re actually getting and what to do with the parts you receive.