The throttle mapping is nonlinear so that something like 10% pedal gives you 50% gas, so it's really hard to control smoothly.
The 1st gear to 2nd gear shift also has really bad rev hang where you have to wait for a very long time in between 1st and 2nd gear before you can engage the next gear. This makes controlling the car at slow speeds to be really jumpy and uncomfortable. Lots of manual transmission cars made after 2010 have rev hang supposedly for emissions purposes.
One way of solving this is to buy a $700 Cobb Accessport and flash your car's ECU with a "stage 1" off-the-shelf Cobb tune. This makes the throttle mapping linear and removes most of the rev hang. These off-the-shelf maps are supposedly CARB compliant.
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Cobb also has a stage 2 tune that requires replacing the turbo-back exhaust of the car (a.k.a. a downpipe/j-pipe), which is less restrictive for emissions and adds a good amount of horsepower. Supposedly these stage 2 tunes and turbo-back hardware are CARB compliant nowadays, but the laws are fairly new so Cobb sold non-compliant versions up to a few years ago iirc. Tuner shops can also create their own non-compliant custom tunes using the Accessport.
It's a similar world with fuel injected dirt bikes. Although the throttle is mechanical, some specific fuel and ignition mapping choices the manufacturers provide results in huge amounts of acceleration with small amounts of throttle input. The exact reasons why aren't published, but the general consensus is it relates to emissions.
Remapping the factory ECU completely resolves the issue, albeit obviously a "defeat device" per the EPA
"Lots of manual transmission cars made after 2010 have rev hang"
I think this is similar to "skip shift". The idea is to force you to shift from 1st to 4th so you use the more efficient ratio. Stupid idea in my experience since it forced higher RPMs in an inefficient gear and can have some drivability issues in traffic and on hills. You technically don't need a tune to eliminate this. They make jumpers that sit between your computer cable and the transmission that eliminate the gear lockouts. You could also pullout in second and it would bypass the skipshift logic since you aren't in first.
The rev hang or skip shift isn't about unburnt hydrocarbons, it's about efficiency standards. It's a different problem - emissions efficiency is one thing and emission compound/type restrictions are another.
Incorrect. The engine speed hold is there to optimize mixture while the engine decelerates, instead of just slamming the throttle shut. Depending on where the fuel is injected, cutting off fuel and air instantly leads to either too much fuel or too much air in the cylinders. The electronic rev hang corrects this to reduce NOx and unburnt fuel. It does not improve fuel efficiency.
The difference between DI and port injection is only which thing is escaping the catalytic converter. With port injection the engine is rich after lifting off the throttle, and hydrocarbons escape. With direct injection the engine leans out, and NOx escapes. In both cases the rev hang exists to keep the emissions system in its effective air/fuel ratio range. Every hanging MT car I ever owned was DI.
That's very odd. DI should only be firing a full shot injector as the air is coming in, or already came in. It really shouldn't lean out. If your DI car had rev hang, it's for other reasons.
We were discussing the 2015 WRX after all, it is port injected. The guy who wants to delete the rev hang from his VA WRX is advocating to blowing unburnt gas right out of the tailpipe, like a psycho.
> Why do people install these parts? Do they improve performance somehow?
Yes. Most turbocharged cars come from the manufacturer with an enormous amount of left-over power. Many "Stage 1" (no hardware, only software) calibrations for a modern turbocharged car like a VW GTI will produce a 30-40% gain in peak torque. This is for several reasons:
* Emissions. A catalytic converter in some ways works as an oxygen capacitor - it "fills" with oxygen while excess O2 is present (for example, when fuel is cut on deceleration or when the car chooses to run lean-of-stoich) and "discharges" while converting excess hydrocarbons to water. There are other extremely complicated principles at play like catalyst light-off and heating, but this is the basic concept.
* This means that an OEM calibration is a careful balance wobbling between lean and rich of stoichiometric operation (called "catalyst stimulation"). However, this is not the ideal condition for producing power. Due to the flame propagation properties of gasoline-air mixtures, gasoline engines produce optimal torque at a mixture condition rich-of-stoichiometric (this is called, counterintuitively, Lean Best Torque or LBT). And turbocharged and high-compression gasoline engines are extremely vulnerable to unstable combustion conditions (detonations and preignition) which are also alleviated by running a richer mixture. The most common way to increase power on a turbocharged car is to change the air-fuel lambda target from 1.0 (stoichiometric) to around 0.84 under full load, then to increase boost to the safe maximum from the turbocharger (or beyond) and timing to the knock threshold.
* There are also obvious warranty and longevity concerns. Running a turbocharger at 70% of its shaft speed maximum will make it last longer than running it at 120% of its shaft speed maximum. Putting 450 ft-lb through a transmission designed to handle 300 ft-lb will break it.
None of the comments at the time of writing this comment actually answer your question in regards to cobb tuning devices I’ll try.
It depends.
It’s not that these devices really significantly increase power, it’s that all the mods that do make power are near useless without a tune, and this device allows that tune.
Recent engines may suffer in performance due to the ever stricter emissions standards. Earlier engines from like 10 years ago probably benefited from emissions standards because things like direct injection, higher compression ratio and so on all both increase performance and reduce emissions(this is oversimplified)
So in a very recent car a device like this might actually be able to be used to give a “better” tune to the car that sacrifices emissions for performance. It’s like the government and the manufacturer of the car make choices on the trade off between engine performance and good emissions, this device allows you to make a difference choice.
However, that’s not really how I’ve seen these used because that would be a very expensive way to gain a small amount of power. The thing is that with any car from like the last 20 years or more, if you do modifications like high flow exhaust, bigger cams, adding a turbo where there was none or adding a bigger turbo, and so on, will all, almost certainly, decrease the performance of your car if those mods start to add so much air flow that the default tune can’t keep up. It should also be mentioned that running an engine like that will ruin it quickly. If then, you use a device like this to tune the car to suit the mods, you can double or more the performance of the engine.
I’m glossing over a lot of details here, like for instance ecus are sometimes closed loop systems that can to some extent adjust the fuel flow with increased air flow, but it’s likely that the engine will give you an error code and display the check engine symbol. It should also be noted that some ecus will go into open loop when you floor the car, which is when you want the most power. This can be really bad if you have mods that increase the airflow and volumetric efficiency of the engine. Point is, your mods are useless without a tune.
I have a few device(s) installed on my 2017 Turbo Lexus. Yes they improve performance. Newer drive by wire throttle controls are laggy as crap. 30 year old cars with cable driven throttles perform better than new electronics in some cases.
I've got an aftermarket OEM Toyota (Tom's) device sitting between my boost sensor and cam sensor to advance the timing and boost and I've got a throttle advance controller to get rid of the throttle delay in the drive by wire throttle.
And the car isn't fun to drive without those two things. I would just drive something older without all the throttle delay between pushing the accelerator and the car "going"
Yes we have a salvage model 3 Tesla - I'm saving the planet or something. I also have 5 other cars I like to tinker with on the weekends. This will keep happening most likely due to the RPM Act.
If you're not an OEM certifying the car, the EPA is going to keep going after aftermarket tuners; too much evidence to ignore.
>the EPA is going to keep going after aftermarket tuners; too much evidence to ignore.
Which will probably drive them off shore where the regulators don't matter and then people will be buying tuners from China or buying off the shelf commercial scan tools and loading new firmware onto them that lets them use them as tuners and do whatever.
The only reason this hasn't happened yet is because domestic tuners have generally satiated that demand at the right price.
Many of these tuners deal with all sorts of pesky chimes and idiot-proofing of which at least a couple specific features are a nuisance to any given person, default settings you can't change, etc, etc so the demand that's there is more than just enthusiasts and the people who'd rather turn off the CEL in software than replace a cat.
Any cats and whatever impede the flow of exhaust gases - by removing them you may get quicker turbo spool up
It used be that tuning turbos to run 'rich' (more fuel) was the safer move, because lean can cause engine knock; although I don't really know how things are nowadays
Your information is out of date like you suspected. The causation is now backwards from what you said.
Some people are removing the cats because they're running super rich tuns that trash the cat fast enough to be a problem. No cat on a vehicle this century restricts anything enough to matter when compared to the the rest of the exhaust system.
Some other people who intend to make so much power that they upsize the whole exhaust system they frequently just don't run a cat because the cat is a restriction compared to the now larger system and tuning it out in the software you already paid for is free and a new cat is expensive.
Interesting. The old belief was 'catback for noise, turboback for power'
I remember reading that some big power Lightnings blew motors when the seasons changed (guessing they tuned in the summer so in the winter it ran lean, but I can't recall).
All of this probably depends on how smart your ECU is...or isn't
If you did not change anything about the intake, installing a wider exhaust could be either neutral or detrimental. Many people have bought magic exhaust mods for their naturally-aspirated cars only to discover that the engine now guzzles fuel without being noticeably more powerful.
Quite ironically, turbochargers remove a big deal of sound from exhaust, because the energy is extracted back to do useful work. Otherwise it would be emitted as noise pollution, which some sociopaths cherish for some reason. I believe exhaust systems can (and most likely are) acoustically tuned to do similar thing by fluid dynamics too.
