Rev hang explanation... - Hyundai Genesis Forum
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post #1 of 22 Old 05-25-2009, 03:04 PM Thread Starter
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Rev hang explanation...

By Jay at SuperDrift

"Well, there has been many speculations and researches by shops, but we got this "unofficial" explanation straight from the horse's mouth. We can't name who, but he/she worked on the Gen coupe project.

The rev hang (partial opening of the throttle) was put into the throttle body control in order to lessen the blow by gas emission. During the development Hyundai researchers experienced that if a throttle body closes immediately, pressure inside the engine(crankcase) becomes so great, it caused more oil vaporization than usual. This is quite normal for any turbo charged engines, but Hyundai wanted even better emissions and didn't want to deal with the "oil loss" issues. Thus by partially keeping the throttle body open even after gas pedal has been completely released, pressure can escape from engine.

So, here is what we found out. Solution to the rev hang issue will be to fix the throttle body control codes in the ECU, install oil catch can and add oil every month.."

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post #2 of 22 Old 05-25-2009, 06:35 PM
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i can handle adding a little oil every month.

i cant wait for this reflash
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post #3 of 22 Old 05-26-2009, 08:11 PM
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good find. makes sense too. here comes the $20 home depot catch can mod lol
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post #4 of 22 Old 05-26-2009, 09:21 PM
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Jeez I havent even asked PowerAXEL if their reflash solves this. Will do for sure tomorrow but be sure to stay tuned, there WILL be a solution!

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post #5 of 22 Old 05-26-2009, 10:43 PM
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We've known for a while it was because of emissions but this is the detail a lot of people wanted.. thanks for posting this.
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post #6 of 22 Old 06-26-2009, 04:57 PM
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Well, for all you 2.0T owners, after I replaced the OEM BOV with the HKS SSQV, it eliminated my rev hang completely. That was the very first thing I noticed immediately on the test drive.

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post #7 of 22 Old 06-26-2009, 07:05 PM
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This is the second case that I have heard that just putting a better BOV on the car almost completely eliminates the rev hang. I guess if the BOV is more efficient it can effective reduce the pressure faster than the stock one and eliminate the need for the throttle to stay open for so long.

HGC Light Blue 2.0T Built on 12 / 23 / 08 Accepted on: 4 / 7 / 2009
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post #8 of 22 Old 06-26-2009, 09:32 PM
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boob.
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post #9 of 22 Old 06-26-2009, 11:18 PM
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MSUGeoman22: While we will look into it further, in the meantime 4TGEN may be able to give you his feedback on this rev hang. I believe after our reflash, he felt his rev drop faster than before.
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post #10 of 22 Old 06-27-2009, 06:34 AM
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Thanks Arvin, I think that it is completely attributable to the throttle mapping and the dual mass flywheel, not the BOV. Not having the throttle closed all the way when the pedal is at 0 throttle between shifts means that no matter what BOV/BPV is installed, the engine will still rev and all of the pressure will be evacuated from the manifold and pipes. Ideally, the throttle should be completely closed which would retain some of the pressure in the manifold and would give quick throttle response time but the factory programming does not allow this to happen. Hanging the throttle open essentially makes the turbo have to start all over again and makes the car feel lumpy and laggy. I can't wait to get some programming to see how this car SHOULD have been from the factory.

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