lowering VTEC engagment

[fatboyz39]

We just finishing tuning a JDM k20a, vtec was at 4300rpm. Forgot the lower and upper boundary.

[mugsee]

What ecu do you have? If its vfac then don't bother. The only way you can really lower the vtec engagement without the loss of power is to have an ecu that can tune for cam angles and ignition timings. Vfac i think only does air/fuel which does sweet nothing for the DC5.

I only tuned for af and the power difference was nothing. DC5's make there power by tuning the ignition and cam angles.

I have to disagree with kookie on this; Honda's come tuned rich from factory so even a light AFR tune with a VAFC will give some gains. This would be proportional to modifications to your car and with each modification, lowering the vtec point maybe beneficial as the car now breathes differently. Vincikwan has already pointed out. I wouldn't go as far as to say that AFC's aren't a waste of time because clearly their not, but they certainly don't provide a better solution than a fully tunable ecu. Again it comes down to the $$$ game.

Kookie, did you tune your ECU yourself and see for yourself that tuning AF does nothing for the DC5? I find that hard to believe. Also, did you tune for a DC5 basemap or a predefined map by Hondata?

[kookie]

Yes I did tune myself and I found more of a power gain when tuning for ignition and cam angle then i did for af. I used a base map from kmanager and worked from there.

My tune is completely different to what the US base map is. When you first start out with the tune af makes a considerable difference, but thats because US base map works with 91 RON (Correct me if I'm wrong) and we have much better fuel here 98 RON.

Well AFC's aren't going to net you massive gains but as we all know. You get what you pay for. More gains are to be had with a full programmable ecu then a piggy back that changes your af.

[mugsee]

Yes I did tune myself and I found more of a power gain when tuning for ignition and cam angle then i did for af. I used a base map from kmanager and worked from there.

I thought you got your tune done from James...? Why did you feel the need to change his tune? Out of curiosity, how long have you been tuning your car for?

Well AFC's aren't going to net you massive gains but as we all know. You get what you pay for. More gains are to be had with a full programmable ecu then a piggy back that changes your af.

What ecu do you have? If its vfac then don't bother. The only way you can really lower the vtec engagement without the loss of power is to have an ecu that can tune for cam angles and ignition timings. Vfac i think only does air/fuel which does sweet nothing for the DC5.

I guess your retracting your statement about AFC's doing nothing here by saying that there are gains to be had with using an AFC?

My tune is completely different to what the US base map is. When you first start out with the tune af makes a considerable difference, but thats because US base map works with 91 RON (Correct me if I'm wrong) and we have much better fuel here 98 RON.

I only tuned for af and the power difference was nothing. DC5's make there power by tuning the ignition and cam angles.

Contradicting yourself just a bit? Show us a bit of consistency in your logic.

[ChargeR]

My tune is completely different to what the US base map is. When you first start out with the tune af makes a considerable difference, but thats because US base map works with 91 RON (Correct me if I'm wrong) and we have much better fuel here 98 RON.

You are wrong and I will correct you .

The method for rating octane of fuel in the US is different to Australia. We use RON which is an octane rating measured in a variable compression engine comparing the fuel's knock resistance to two known fuels with RON of 0 and 100.

The octane number the US uses is an average of RON and MON, MON being measured in a different way and is typically lower.

I suspect that 93 octane fuel available in the US is very similar or better than Australian 98 RON fuel.

[kookie]

Ohhh thanks for the correction.

[mugsee]

Its funny that Kookie says that Australian fuel is much better than American gas. When I was tuning my car, I found that even the Hondata basemaps provided (which are tuned using American pump gas) managed to run values with more advanced ignition than what I could manage down here with our Australian fuel pre-detonation.

Kookie, did you really tune your car to a fully drivable state or was it just tuned by someone else? It just surprises me that you've come up with false or bad information in this and previous threads that might have misled others when you've tried to provide tuning advice.

[kookie]

I tuned it to a drivable state with increased power but then got it re-tuned because i didn't have the time to continually tune the car and plus got it tuned really cheap.

Well that was my experience when tuning my car, not sure why its different, but thats how i tuned it and got power. Take my advice with a grain of salt as there are more knowledgeable people on the forums. Just putting down what I have done with my own car and experience.

I'm happy to be corrected. learning is power right?

[ievaq8]

the only reason the manufacturer has it so high, is to pass emisions and noice regulations, the car was built to rev and be driven hard................thats why honda hand built the b18c7 type r motor............lower the vtec and have it tuned to suit...............or naturally tune the car to where it likes and responds best to vtec................my vtec point was at 5200 and it smoothed out the graph imensly and the car felt alot smoother to drive.............................

[MRK20A]

The engine they are referring to is a K20A...

[mugsee]

I tuned it to a drivable state with increased power but then got it re-tuned because i didn't have the time to continually tune the car and plus got it tuned really cheap.

Well that was my experience when tuning my car, not sure why its different, but thats how i tuned it and got power. Take my advice with a grain of salt as there are more knowledgeable people on the forums. Just putting down what I have done with my own car and experience.

I'm happy to be corrected. learning is power right?

Learning is well and good and most welcome in these forums but providing misleading advice can be destructive, eg. "take your car to 'so and so', because they're the best Hondata tuner in Australia"...

From what you've described, your tuning experience is no where near what it should be to be giving out advice like you previously tried to do.

Your should really get your information correct before trying to advise others.

ievaq8, are you sure the only reason why vtec is set so high is because of epa and noise regulations? What about fuel ecconomy? What about the power characteristics of the high/low cams?

Please read my message addressed to kookie above, because you too seem to be in the same boat as him.

[ievaq8]

ievaq8, are you sure the only reason why vtec is set so high is because of epa and noise regulations? What about fuel ecconomy? What about the power characteristics of the high/low cams?

Please read my message addressed to kookie above, because you too seem to be in the same boat as him.[/QUOTE]


sorri mate...............i didn't realise that this was only relating to k20...........
i was refering to b18c.................sorri....once again

[szymonsta]

im using a mugen n1 ecu and the high-cam engagement point ("when vtec kicks in" as some of you call it) is from memory 4800rpm vs 5300rpm stock, obviously mugen tune this ecu to have appropriate ignition and valve timing as well as air:fuel ratio to make use of the lower rpm point at which the high-cam is engaged to provide slightly more torque and power, most noticeable in the mid-rpm range but carried through all the wayto rev-limit.
when running the mugen n1 as opposed to the stock ecu, my fuel consumption is worse (~1L/100km worse) and of course the a/c doesnt work

[ChargeR]

ievaq8, are you sure the only reason why vtec is set so high is because of epa and noise regulations? What about fuel ecconomy? What about the power characteristics of the high/low cams?

I disagree here. If one decreases the vtec changeover point and gains torque in that area it is most likely due to improved volumetric efficiency. This means that at that engine RPM the high cam is doing a better job of filling the cylinders than the low cam. If this is the case the engine is operating in a more efficient manner due to lower pumping losses. This should result in better fuel economy or at least unchanged fuel economy.

The concept is the same for both B series and K series engines.

[mugsee]

I disagree here. If one decreases the vtec changeover point and gains torque in that area it is most likely due to improved volumetric efficiency. This means that at that engine RPM the high cam is doing a better job of filling the cylinders than the low cam. If this is the case the engine is operating in a more efficient manner due to lower pumping losses. This should result in better fuel economy or at least unchanged fuel economy.

The concept is the same for both B series and K series engines.

Sorry, I should have been more clear. My questions about fuel economy and power were rhetorical. I agree with your comments above.

The point that I was trying to make was that Honda did not raise vtec to its stock point (6000rpm?) because of noise and pollution. They raised it for 'volumetric efficiency' of the engine. They used small exhausts with restrictive exhausts to reduce noise and catalytic converters to minimise pollution.