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Old 17th May 2010, 23:22   #1
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Default NHC engine revv limiter not working?

Recently i got my NHC serviced at 20k, i has felt jerking at rpm of around 1100-1200, but my dealer refused to accept the problem so i asked him to scan my ECU and as it was covered in warranty i was not charged, yesterday i has a chance to drive it on highway and i felt that the jerking to be still present, but the acceleration has improved and engine is now a lot smoother, but to my surprise the engine crossed 6000 rpm limit in 2nd gear, normally the limiter would cut the rpm at 6k earlier but this time it almost went 6200-6300 before i realized that limiter didn cut in. i haven dared to try it again as i know it would damage engine.

i wanted to know if dealer has spoiled my ecu setting or might have just changed them to VTEC one? and how come theres so much difference in acceleration?
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Old 21st May 2010, 11:01   #2
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You know, some of us would pay good money for that . Increasing the revv limit, that is.

I swear my Vtec revved to 7,400 rpm on some occasions, and Shantanu had reported the same with his car. This was only temporary though. I suggest you drive a couple of kms; good chance that the ECU was reset and still in a learning phase. However, if the limiter still doesn't kick in, and you aren't comfortable with that, have the authorised service center look it up.

Just for the record : As long as you have your oil changes on time, redlining a petrol engine once in a while hardly makes a difference to its long-term reliability. I high-revved my OHC Vtec (running on Mobil 1) for more than 1/2 its life, yet at over 70,000 kms, it showed 106 BHP at the dyno (still a healthy engine). Modern engines are built to last over 2,00,000 kms. Again, basic maintenance practices like timed oil changes, keeping the revvs low when cold etc. are more important.
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Old 21st May 2010, 12:35   #3
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With the stock cam on the OHC VTEC, you're already running out of power at 7.1k RPM. And going a good amount beyond that on stock valvesprings will most probably destroy your valves and whatever they come into contact with. I actually lowered the redline on my OHC from 7100 to 6900 once I had my ECU connected to my laptop.

Don't know the redline of the NHC, but if you feel you can overrev, don't take it beyond the stock redline and get it checked soon.

Last edited by pranavt : 21st May 2010 at 12:36.
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Old 21st May 2010, 12:50   #4
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Quote:
Originally Posted by pranavt View Post
I actually lowered the redline on my OHC from 7100 to 6900 once I had my ECU connected to my laptop.
Is OBDII cable the method you used ?
or you have any special tools/cables to do it ?
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Old 21st May 2010, 12:57   #5
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Quote:
Originally Posted by GTO View Post
You know, some of us would pay good money for that . Increasing the revv limit, that is.
very true .

And regarding rev limiter I guess for NHC its safe till at-least 6.5k. If the limiter doesn't cut in even at much higher rpm's, parts may not withstand the additional stress generated. Better get it checked.
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Old 21st May 2010, 13:19   #6
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Quote:
Originally Posted by ghpk View Post
Is OBDII cable the method you used ?
or you have any special tools/cables to do it ?
Special tools on a chipped and remapped Honda P28 ECU.
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Old 23rd May 2010, 04:13   #7
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Anyone knows the factory rev-limit of an NHC? OP, Is the rev-limit mentioned in the owner's manual? Where is the redline marked on the tachometer?
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Old 23rd May 2010, 21:03   #8
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Hi,

Do you mean peak power, yeah maybe! (peak power on our cars come at 6800rpm if I am not wrong) But otherwise,its not like the car will start running out of power. Technically, if you have the correct fuel map and ignition map to support, you will definitely not feel out of breath.
I have been taking my OHC Vtec to 8000rpm almost every second day, on stock valvesprings, stock cam. Nothing happened. As a matter of fact, I know of many OHC's running to 8000rpm with the stock cam and springs.

Just my 2 cents, dunno abt others.

Cheers
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Quote:
Originally Posted by pranavt View Post
With the stock cam on the OHC VTEC, you're already running out of power at 7.1k RPM. And going a good amount beyond that on stock valvesprings will most probably destroy your valves and whatever they come into contact with. I actually lowered the redline on my OHC from 7100 to 6900 once I had my ECU connected to my laptop.

Don't know the redline of the NHC, but if you feel you can overrev, don't take it beyond the stock redline and get it checked soon.
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Old 23rd May 2010, 21:31   #9
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Quote:
Originally Posted by ssjr0498 View Post
Hi,

Do you mean peak power, yeah maybe! (peak power on our cars come at 6800rpm if I am not wrong) But otherwise,its not like the car will start running out of power. Technically, if you have the correct fuel map and ignition map to support, you will definitely not feel out of breath.
I have been taking my OHC Vtec to 8000rpm almost every second day, on stock valvesprings, stock cam. Nothing happened. As a matter of fact, I know of many OHC's running to 8000rpm with the stock cam and springs.

Just my 2 cents, dunno abt others.

Cheers
Shrey
Yes, peak power. We both know how long it takes to bump up the revlimit with our fancy ECUs, so I'll just get to the practical bit about saving the engine. A few hundred extra revs for a few seconds is definitely not worth the broken parts that can result from it. And with open loop, iffy maps beyond the stock revlimit and no knock sensor, I do not wish to test the thermal efficiency of my engine's cooling and ignition system.
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