Acceleration

[faction]

I know this was mentioned a while ago, but someone said that the acceleration "responsiveness" was a product of "torque" (rather than how hard you hit the gas).Can some one explain this to me in automotive-retarded language?

and as I understand it, the manufacturer sets these cars up for a kind of average of what most people drive...so can it be adjusted to respond faster?

I live in an area with a lot of two-lane roads where there is very little chance to pass a car if you have to, so when you gotta move--YOU GOTTA MOVE! I need better acceleration quickness.

[Clipsed]

the problem is the car is drive-by-wire, the accelerator sends a signal to the ECU, which in turn sends a signal to the throttle body saying, hey the accelerator was just depressed by this much, so you need to open up this much. Well as we all know, it takes time for this to happen, and it is not instantaneous, and I don't think that even with a reprogram that it will ever be as instantaneous as the good ol cable driven accelerator.

[Rockhound]

I think we need clarification as to what you mean by 'responsiveness'. The responsiveness of acceleration is dependent on a lot of things, including torque - as well as gearing. It's complicated and I won't pretend to be an expert.

Clipsed is right in his description of drive-by-wire, but I have a sneaking suspicion that isn't what you were referring to. The throttle lag with the Versa is noticeable - but once the car is already going it's pretty much negligible in the scenario you describe (passing on a two lane road).

You say you want more "acceleration quickness". If all you're saying is that you want faster acceleration, then you'd need to modify your engine. Small mods like intakes and exhaust will probably only add placebo HP - as it's doubtful they'd shave more than a few hundredths of a second off the 0-60 time. More in-depth modification, like re-mapping the ECU, could be done, but I'm not sure if any company has tackled that project for the MR18 engine. A turbo would also help, but I think those are mostly one-off creations right now.

So as far as "adjustments" - I'm not sure what you mean. I'm sure there's probably the potential to unlock more power from this engine with a full tune, but for something that'll really add punch like you desire, you're going to have to pony up.

[CodeRed]

So as far as "adjustments" - I'm not sure what you mean. I'm sure there's probably the potential to unlock more power from this engine with a full tune, but for something that'll really add punch like you desire, you're going to have to pony up.

SR20 swap.

[Clipsed]

SR20 swap.

previously discussed, and as a mod, you should not start up the controversy again. It is not street legal to do it ANYWHERE in the US.

[TrustME]

SR20 swap.

[Rockhound]

previously discussed, and as a mod, you should not start up the controversy again. It is not street legal to do it ANYWHERE in the US.

Did I miss something?

I thought that as long as an engine was US-spec and built to pass US emissions standards (among other tests) that it was perfectly legal to perform an engine swap, as long as the new setup passed all applicable emissions standards (and state laws).

I'm not trying to be smart here, just asking for clarification.

I know Cali has some of the most stringent laws regarding car modification, but I thought it varied state to state as to the type of swap allowed, as I know some dictate it by age of engine and so on. But if this were the case everywhere, then it seems all kit cars and such would be illegal.

[Clipsed]

Did I miss something?

I thought that as long as an engine was US-spec and built to pass US emissions standards (among other tests) that it was perfectly legal to perform an engine swap, as long as the new setup passed all applicable emissions standards (and state laws).

I'm not trying to be smart here, just asking for clarification.

I know Cali has some of the most stringent laws regarding car modification, but I thought it varied state to state as to the type of swap allowed, as I know some dictate it by age of engine and so on. But if this were the case everywhere, then it seems all kit cars and such would be illegal.

bro, lets not hijack this poor guys thread, and start going into already charted waters. . . . . .

zerothread?id=259700

zerothread?id=262960

zerothread?id=212398

In a nutshell though if you don't want to take the time to read that, you can not put an engine from a chassis that is older than yours, i.e. you can not take an engine from a car that was built in say 99 and put it into your 07 vehicle, you could do the opposite though, or put in an engine from an 07 chassis or now even an 08.

[Rockhound]

Well, bro, to my credit I did search , just not NICO, as I find that process unnecessarily time-consuming and those posts came along before my time on here. I did some quick searches on Google and found many sites describing particular states' regulations regarding swaps, but I couldn't find federal laws. I wasn't aware of the "across the board" age requirement on swaps.

I definitely learn something every day.

The thing is, states like Kansas and Oklahoma do not have any emissions tests or inspections...so while I understand it may still be illegal in these states, it seems as if there wouldn't be any scrutiny as to what you want to do with your car (for better or worse - not saying it's a great thing).

As for the "threadjack", well, I'm not sure what more there is to add to the original question anyway..."minor" modifications probably won't result in profound acceleration increases and "major" modifications are, at the time, both exclusive and expensive. And even if a tuning company releases reprogrammed ECU chips, for instance, that'll always be a rather expensive mod.

[Nismo V]

Both clipsed and rockhound seem to have given you solid answers as to why your car response time is what it is.. But to answer the part about driving the two lane trying to pass .. it would seem better to leave earlier and avoid the stress and danger of trying to pass and potential injury due to accident to yourself or someone else...

Think about it bro...

[lain]

There are also no emissions laws in Arizona, so clipse if you wanted you can just go to there get your Arizona ID and have your car registered over there and just get insurance over there too (btw insurance is alot cheaper in arizona too). Say that you travel back in both quiet often but live in Arizona. This way you can get away with any laws to do with your car here in CA. I know people that have been doing this for years with the same car. Only probably is you have to know someone in AZ and use there address

[Rockhound]

There are also no emissions laws in Arizona, so clipse if you wanted you can just go to there get your Arizona ID and have your car registered over there and just get insurance over there too (btw insurance is alot cheaper in arizona too). Say that you travel back in both quiet often but live in Arizona. This way you can get away with any laws to do with your car here in CA. I know people that have been doing this for years with the same car. Only probably is you have to know someone in AZ and use there address

And we thought an engine swap was poor advice...

[marleyfan]

the problem is the car is drive-by-wire, the accelerator sends a signal to the ECU, which in turn sends a signal to the throttle body saying, hey the accelerator was just depressed by this much, so you need to open up this much. Well as we all know, it takes time for this to happen, and it is not instantaneous, and I don't think that even with a reprogram that it will ever be as instantaneous as the good ol cable driven accelerator.

Has this been tested? Is this statement a result of actually physical realities or is it an opinion or assumption? Not picking on you Clipsed...I'm seriously questioning if this this is fact or assumption. On the surface what you are saying make sense but is it fact. Electrons move pretty fast. Most modern airliners are moving toward fly by wire. So the question is...is a lag (if there is one) as a result of drive by wire rather than cable actually noticeable. Or is the lag in the Versa (if there is one) a result of other factors.

[Clipsed]

like I said, the accelerator needs to send a signal to the ecu, which in turn has to process that signal, and than send out another signal to the TB for it to open, this takes time.

Does your computer instantaneously open an application when you click to open it? No it doesn't, it sends a signal which then gets processed, and says hey this was clicked, we have to open it, and then it loads up, which takes a few seconds.

Same concept.

[Clipsed]

also if you don't believe me, when you are at a red light or a stop sign, floor the accelerator, you will notice a time delay in the time the engine revs up fully. Even at cruising speed, I could notice the reaction delay since I am not 100%, but the throttle body more than likely is actuated, and that also takes time. It is a very complex system, and I don't think it will ever be an instantaneous reaction.

[marleyfan]

So it is an assumption that it MUST take a noticeable length of time. It is not necessarily true. My computer is much more complex than a few signals being sent. There is lots going on. How long an application takes to load depends on many factors such as the size of the program, speed of my hard drive and processor, how much ram I have, how many processes are running and so on. When I push my doorbell button it rings right away. Again, all I'm asking is whether or not a noticeable lag due to drive by wire has been tested and proven. It is possible that all of the things you said must happen upon pressing the accelerator could happen without a noticeable lag. And by the way, I've had many cars that used cable to the accelerator that had a noticeable lag. I'm just asking whether the drive by wire can really be blamed for any lag in acceleration the Versa may have.

[Clipsed]

alright, I'm not going to turn it into a big ol' thing, I will just leave it at that.

[marleyfan]

Clipsed, I'm not looking to pick a fight. It is a legitimate question as to whether or not there has been side by side comparisons of cable throttle vs throttle by wire. All of what you said makes sense but has it been tested. If not then any difference is based on assumption. I'm not saying that they may not be legitimate assumptions in the absence of testing. I'm just asking if anyone has seen test results that indicate that throttle by wire is in fact noticeably laggy compared to cable. Please don't take it as a personal attack.

[Demonspawn]

Hasnt the Corvette been using throttle by wire for a few years now?

[Ever Victorious]

Actually, you kind of answered your own question with your last analogy.

Your doorbell, which is all hardware, rings as soon as contact is made by contact in the switch. Since there is no programming involved, it is just dependent on the presence of current, the doorbell goes off immediately.

This is how cable throttle works. You push down the accelerator and the cable physically pulls the throttle mechanism on the throttle body. this happens in real time.

Your computer, which is a combination of hardware, software, and firmware, takes a while to open a program because it has to receive the information, process it, and then respond to the request (in the form of opening the program).

This is how drive-by-wire throttle works. You push down on the accelerator. A sensor (usually something simple like a potentiometer, but can be any type of mechanism... hydraulic, pneumatic, optical, etc...) sends an analog signal to the ECU. This analog signal is received, processed into a digital signal, then sent to the appropriate processing command for throttle. Your throttle is then received, calculated, and an output is sent to the servo on the throttle body telling it how much to open. The servo receives the digital signal from the throttle body, and changes it back into an analog output in the form of distance it opens the TB.

Because there is software/firmware directly controlling the servo, there is calculation time involved. This is what generates the lag in a drive-by-wire system.

It's hard to directly compare a DBW system to a cable system because, to my knowledge, there are no cars on the market where the same make, model, year, and engine of vehicle have two different types of systems installed. Usually DBW is refitted after a major model redesign (new engine, new body, etc.) so there are other factors that would affect the "feel" such as weight, aerodynamics, power, etc.

This doesn't change that there is a lag. Turn on your V in the driveway and put it in neutral. Push the gas in and hold it. doesn't have to be far... enough to get it to idle around 2000 RPM is enough. Notice when you push the throttle in that there is around a .25-.5 second delay between when you push the throttle and when it actually opens up. Notice that this same exact delay occurs when you let off the throttle... the RPM's don't drop at all for .25-.5 seconds. (BTW, it's NOT the flywheel doing this).

The challenge will then become finding a car with an actual cable throttle that is new enough that there is a point to testing it. If you can find one, do the same test. You will either not notice a delay in throttle at all, or it will be SIGNIFICANTLY shorter than the Drive By Wire throttle.

Someday DBW will be as quick as cable throttles... but they have to choose to use faster processors and more efficient code before that can happen.

[marleyfan]

Actually my doorbell is connected by wire to the dingy thing. Ring by wire you might say. But I get your point. Has this "processing" time been calculated. You say you "feel" a half second or so delay. This delay should be able to be calculated and measured, or is it just a "feeling." Actuallly....forget it. I just realized that I don't care any more.

[Rockhound]

The challenge will then become finding a car with an actual cable throttle that is new enough that there is a point to testing it. If you can find one, do the same test. You will either not notice a delay in throttle at all, or it will be SIGNIFICANTLY shorter than the Drive By Wire throttle.

Well, my G20 is not new by any stretch of the imagination, but it has a cable-throttle with very instantaneous results. I can open my hood while the car is running and yank on the cable and rev the engine - it's very responsive.

On the other hand, I still have not learned how to keep from making the Versa (CVT, no less) jumpy in stop/go situations, which I've attributed to DBW throttle lag.

Marley, I don't think there's any doubt in anyone's mind that DBW creates a bit of throttle lag...it's just the name of the game. It doesn't take much lag in the system to be noticeable, either. But I think you're right - it could probably be measured to an extent.

[reyes1212]

is it just me or have clipsed and codered been going at it at each other lately?

[Clipsed]

is it just me or have clipsed and codered been going at it at each other lately?

naw, we just nit pick eachother sometimes, you have to remember that we are about the same age, and I messed with him even before he became a mod. We also talk on AIM once in a while, so yea, inside stuff lolz

[BBISHOPPCM]

**not trying to add to the pissing contest** but even cable-activated throttles have a delay. The cable directly opens the butterfly valve, which allows more air into the intake; but in order for there to be a reaction, more fuel is needed (a combination of the MAFS an the TPS determine the correct amount). Once the computer processes this information, it will then determine the appropriate fuel injection pulse/time rating for the condition. If you floor the accelerator from a stand-still, just as much is taking place as a fly-by-wire system. I believe FBW is a smart idea, as it eliminates a few sensors and centralizes the fuel/air ratio system. If you want REAL TIME, retrofit the car with a good ol' fashioned carburetor. I suggest a quad-carb setup. Properly adjusted, a carburetor can outperform fuel injection.

[Jojo Versa]

I know this was mentioned a while ago, but someone said that the acceleration "responsiveness" was a product of "torque" (rather than how hard you hit the gas).Can some one explain this to me in automotive-retarded language?

and as I understand it, the manufacturer sets these cars up for a kind of average of what most people drive...so can it be adjusted to respond faster?

I live in an area with a lot of two-lane roads where there is very little chance to pass a car if you have to, so when you gotta move--YOU GOTTA MOVE! I need better acceleration quickness.

I worked for a heavy-duty Diesel engine manufacturer for years, when I started I remember an engineer with 40 years experience describing Torque in layman's terms as simply being ''the engines capability''. To keep it simple Torque is actually a force, as an example the force required to move something a certain distance, think of a very common tool a Torque wrench which permits you to apply a force to move a nut rotationnally a certain distance which can be measured linearly. You require engine Torque to start your vehicule from a standstill, you need torque to enable a vehicle to go up hills, engine HP will be felt after the Torque. On our 2008 Versa the lag or drag is almost unnoticeable, however there is a combination of factors contibuting to lag, yes there is the signal, there is also the current anti-pollution systems, the setup of the CVT, the quality of the gas you purchase, as well as the general onboard computer programming and setup. I would tend to believe presently that if you were to try an Altima equipped with a CVT but with much more HP you would probably experience less lag or drag with all factors being relatively equal. I find that I have more lag in another brand of car we purchased just 2 weeks ago equipped with a 5 speed conventional automatic transmission and this one has 40 more horses than the Versa. Manufacturers can also be setting up there vehicles to meet the most stringent emission controls and selling that same version in all 50 states instead of having 2 or 3 variations.

[faction]

so the answer is "no".



thanks

and not that I usually care, but it's "gal"