Rev-hang revisited - fix may be available soon

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stevenj
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Re: Rev-hang revisited - fix may be available soon

Post by stevenj »

If I could get a canned tune for 2013 Yaris (Vitz) with 1NZ-FE engine, I would. So far I was not able to find it anywhere.

As for "fooling" the ECU, I am not changing values of any sensors the ECU is getting feedback from. The RPM sensor always reads the actual engine speed and the ECU makes the same "decisions" about its output whether my box is connected or not. Thanks to that I am getting no error codes.
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Shadow
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Re: Rev-hang revisited - fix may be available soon

Post by Shadow »

stevenj wrote:If I could get a canned tune for 2013 Yaris (Vitz) with 1NZ-FE engine, I would. So far I was not able to find it anywhere.
If you can't find a canned tune, you can always get a custom tune instead. Canned tunes are available for most cars, but custom tunes are available for ALL cars that are computer-controlled.
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stevenj
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Re: Rev-hang revisited - fix may be available soon

Post by stevenj »

Any suggestion who offers custom tune for my car model? I sent out some mails but did not get far.
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Shadow
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Re: Rev-hang revisited - fix may be available soon

Post by Shadow »

Greddy does a lot of custom tunes for Toyota engines. They might even have a canned tune for your car as well. You can also try Cobb if you can't find anything from Greddy.

Edit: Better yet, why not join the Yaris forums and ask those guys? I'm sure there are people who could point you in the right direction.
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potownrob
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Re: Rev-hang revisited - fix may be available soon

Post by potownrob »

InlinePaul wrote:Also, isn't it the last bit of throttle closing that counts for the pollution reduction, so that you could have it close about 85 to 90 percent, then go slowly. I think that was what the old dashpots did. So if that were the case, rev hang would not be a nuissance as it would close to near idle right away.

(I was once told the dashpot was to prevent the throttle from snapping entirely shut so suddenly that the engine would stall--presumably total misinformation anyway.)
i'll put all the pot and/or pots I want on my dash, thank you very much.

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daleadbull
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Re: Rev-hang revisited - fix may be available soon

Post by daleadbull »

potownrob wrote:i'll put all the pot and/or pots I want on my dash, thank you very much.

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Hence the name POTownrob
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stevenj
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Re: Rev-hang revisited - fix may be available soon

Post by stevenj »

To Shadow:
thanks for suggestion to check out GReddy and Cobb about tunes. I am not having much luck with either of them so far. The Gredy.com shows they sell "piggy back" tuning system e-manage for $690 +$230 for required harness (for 2002-05 only, not 2013) and the website does not show what parameters it can change in ECU. They do not have any authorized dealers in Australia. The Cobbtuning.com lists several makes they support but not Toyota. This confirms my suspicion that Toyota (DENSO) ECU has not yet been cracked.
To Inlinepaul:
Closing throttle just above idle will not eliminate rev hang. Before building my CUREVS box I experimented by installing a damper similar to an old-style dashpot to the throttle pedal of my fuel injected car. The reason is that modern car ECU mimics the operation of the old dashpot by sending injector pulses after throttle was closed, as shown at the graphs I posted earlier. These are much shorter than normal injection pulses, but still long enough to cause the rev hang. Closing throttle to say 10% of full opening generates pulses that are longer than that and in effect the rev hang then gets worse.
My box works a magic and I consider the issue of curing rev hang in my car solved.
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Re: Rev-hang revisited - fix may be available soon

Post by Rope-Pusher »

Rev hang is not just about fuel injection - that would just enrich the mixture if the corresponding amount of air was not also allowed to enter the cylinders.
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stevenj
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Re: Rev-hang revisited - fix may be available soon

Post by stevenj »

Agreed. Throttle pedal sends a signal to the ECU and the ECU then controls both the air and fuel. I was not interested in the air side of things when I managed to kill the rev hang by cutting the fuel. Of course, if I was trying to achieve the opposite - make the engine run longer - then I would have to control the air as well.
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Re: Rev-hang revisited - fix may be available soon

Post by Rope-Pusher »

stevenj wrote:Agreed. Throttle pedal sends a signal to the ECU and the ECU then controls both the air and fuel. I was not interested in the air side of things when I managed to kill the rev hang by cutting the fuel. Of course, if I was trying to achieve the opposite - make the engine run longer - then I would have to control the air as well.
The Rev-hang was added by not allowing the amount of air coming in to drop down to typical amount needed to idle. If you had cut the air, the fuel would have followed along.
'08 Jeep Liberty 6-Speed MT - "Last of the Mohicans"
stevenj
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Re: Rev-hang revisited - fix may be available soon

Post by stevenj »

It looks like an interesting possibility but feedback from O2 sensor to reduce the amount of fuel when mixture became rich after shutting air is a slow link. Shutting air to kill the rev hang would have one disadvantage: the throttle valve is an electromechanical device and has longer response time than injectors. Killing rev hang required instant response.
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Re: Rev-hang revisited - fix may be available soon

Post by Rope-Pusher »

stevenj wrote:It looks like an interesting possibility but feedback from O2 sensor to reduce the amount of fuel when mixture became rich after shutting air is a slow link. Shutting air to kill the rev hang would have one disadvantage: the throttle valve is an electromechanical device and has longer response time than injectors. Killing rev hang required instant response.
I'm sure the throttle plate and/or the idle speed control could cut the revs quickly enough.
'08 Jeep Liberty 6-Speed MT - "Last of the Mohicans"
stevenj
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Re: Rev-hang revisited - fix may be available soon

Post by stevenj »

Strong words "I am sure...". Even if shutting the air dropped the revs instantly, injectors could continue squirting fuel in the intake for some hundreds of milliseconds longer and if the air supply was then reopened quickly by stepping on gas, air/fuel mixture would be super rich at that moment, possibly causing unwanted effects like hesitation or backfire.
Last edited by stevenj on Thu Jan 02, 2014 5:07 pm, edited 1 time in total.
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Squint
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Re: Rev-hang revisited - fix may be available soon

Post by Squint »

stevenj: You might not be aware since you haven't been around, but I'm fairly certain Rope-Pusher works in auto engineering. Not saying you aren't correct, but giving some weight to his statement.

Question: how different is the Australian Yaris from a US/North America Yaris?
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'11 Ford Fiesta Hatchback SE 5MT
'14 Giant Escape City 24MT
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For Pony!
stevenj
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Re: Rev-hang revisited - fix may be available soon

Post by stevenj »

Thanks for that information. I gathered I had the pleasure of discussing technical issues of rev hang with a fellow professional with in-depth knowledge of engine control systems. I did not mean to be disrespectful but I only claim to be sure of things I tested, examined, measured or otherwise verified.

I do not know if there are any differences between the AU and US Yaris.
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