12 Volt to 1.5 Volt Resistor for LED?
Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=34406
Printed Date: April 28, 2024 at 2:00 AM
Topic: 12 Volt to 1.5 Volt Resistor for LED?
Posted By: Mick0005
Subject: 12 Volt to 1.5 Volt Resistor for LED?
Date Posted: June 22, 2004 at 11:00 PM
I am trying to make a VTEC indicator LED for those of you who know what VTEC is...for those who dont, its a special engine feature on honda/acura engines, basically, at a certain engine setting/behavior, 12 volts is sent to a solenoid, engaging oil flow which does all this VTEC business...the problem I am having is that the LED is coming on too early (like 4500 RPM compared to 5800 when it actually kicks in) I am using a 330 ohm resistor connected to the negative lead of the LED (i also tried connecting it to the positve lead) any ideas?? I will be greatful to you forever feel free to email, caliguy0005@hotmail.com THANX!!! -MIKE
Replies:
Posted By: Zx2guy
Date Posted: June 23, 2004 at 12:11 PM
A resistor to the LED will only decrease the brightness of the LED, it does not change the time it takes for the LED to come on. In order to change when the LED comes on you'd need to alter the programming of your car's PCM.
Posted By: Mick0005
Date Posted: June 23, 2004 at 3:15 PM
Yes, but if the VTEC does not engage until 5800 RPM, then 12 volts should not be going to the LED yet, correct? Why would it be lighting up at 44-4500 and not 5800?
Posted By: Zx2guy
Date Posted: June 23, 2004 at 4:41 PM
Chances are the 12 volts going to the LED (assuming it is 12 volts, it may only be 3.5vdc or less) is not the same source as the 12 volts going to the VTEC solenoid. Do you know for an absolute fact that VTEC will only engage at 5800 RPM? Or does it depend on throttle position and vehicle speed?
Posted By: auex
Date Posted: June 23, 2004 at 5:10 PM
If the led is lighting up then vtec is engaging, it is not because of the LED. What engine do you have, specifically, b16, b18C, z6, y8, etc...? Vtec will engage at different points depending on how you are driving, normal or WOT.
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Posted By: Zx2guy
Date Posted: June 23, 2004 at 5:25 PM
I'm not well versed in VTEC engines.. I'm in the Ford ZETEC department 
Posted By: Mick0005
Date Posted: June 23, 2004 at 5:30 PM
B18C1 - From what I can tell it consistently engages at 5800 RPM...the audible and physical effects of the VTEC engagement on the DOHC B18C is quite signigicant....however, I have been doing some thinking... perhaps my VTEC does engage at 4400 RPM in ideal circumstances, and perhaps it is the IAB (intake air bypass) that is switching over at 5800 RPM which would create the additional airflow etc... what do you all think? If so...if I connect another LED to the IAB wire, can I get the same effect (in essence indicators for both VTEC and switchover of the Intake) If I CAN do this...anyone know where the IAB wire/solenoid/sensor is on the Integra GSR?
Posted By: Mick0005
Date Posted: June 24, 2004 at 10:46 PM
For those of u who want to know...I was right- the VTEC comes on at 4400 under optimal conditions, IAB switches over @ 5800 ALWAYS...I hooked up another set of LEDs to my IAB... for those GSR owners out there, it is the pink and blue wire located in the 3rd wire cluster harness (farthest back) in the ECU. Tap into that and the true audible sound and kick that you thought was VTEC will now come on just as the LEDs light.
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