How accurate is your tach compared to RomRaider logger

OC_Nooby · 08-19-2012, 01:07 AM

Hey Guys,

I'm just curious to know how accurate your tach is. I ask because my redline rev limit is set to 6900 "on" and "off" at 6700 in RomRaider but with the logger my measured redline is 7200. That's also where I shift around.

So I want to put my stock 2.5L redline at 7000.

So the settings would be "on" at 7000 and "off" at 6900 (stock 05 sti map). I'm just worried that it would now record the redline at 7300-7400rpm. Not sure if the tach is really reading correctly.

Could my tires cause this confusion? 225/50/16 (unsure of the stock 2003 wrx rim/tires). Its an STI swap in a WRX.

Any help would be nice!

* Registered users of the site do not see these ads.

lukeskywrx · 08-19-2012, 12:27 PM

Trust the ECU, the RPM is detremined by the engine the wheels and tires have nothing to do with it. The error comes in when the signal must be converted to a gauge needle position for the tach display.

There is no accuracy expectation on the stock tach, they are usually within +- 200 RPM. When I spin out to ~8K on the tach datalogs usually show ~7800. so mine reads a little high, but who cares.

OC_Nooby · 08-19-2012, 02:37 PM

I have a blue printed 10mm oil pump so I don't think I'll have any issues but what your saying is trust the ECU and put back the STOCK STI redline rev limit back? I think I will and record to see what it goes to then.

ppayer38 · 08-19-2012, 04:49 PM

RomRaider lags back around 150-200 rpm as you have to give time for the data to transfer from ECU to laptop. This has been focussed before if you would have searched. The tach is a calculated measurment made by the ECU, etc.

OC_Nooby · 08-19-2012, 05:41 PM

I tried to search via google and typing nasioc at the end of my search. Usually I have great success like that, not so much in this case.

ppayer38 · 08-19-2012, 07:37 PM

Quote:

Originally Posted by OC_Nooby

I tried to search via google and typing nasioc at the end of my search. Usually I have great success like that, not so much in this case.

You are 1 of few haha. But as I've stated already go off the tach not RR and remember that it does lag behind. Do a few logs and take some quick glances and you'll see that it shows if the evidence isn't enough by your logs now. Don't want you to blow the car up cause of over revving

OC_Nooby · 08-19-2012, 07:55 PM

Tach shows roughly 7200, RR shows the same. Ecu programmed for 6900. Lowered value compared to what it should be 7000 stock. Maybe I'll just put it back up to stock. I'm using a WRX tach with an STI swap. Doubt it matters but no need to be paranoid.

lukeskywrx · 08-19-2012, 08:05 PM

Quote:

Originally Posted by ppayer38

RomRaider lags back around 150-200 rpm as you have to give time for the data to transfer from ECU to laptop. This has been focussed before if you would have searched. The tach is a calculated measurment made by the ECU, etc.

Electrons do not work that way!

The O2 sensors lag slightly depending on position because it takes a little bit for the exhaust gasses to move. The crank trigger has to be extremely precise to deliver fuel and spark on time and that is where RPM comes from. The data to romraider is just a snapshot taken of the values several times per second.

The tach is just an approximation for the driver to use, DO NOT trust it over the values you are programming into the ECU.

OC_Nooby · 08-19-2012, 08:17 PM

Quote:

Originally Posted by lukeskywrx

Electrons do not work that way!

The O2 sensors lag slightly depending on position because it takes a little bit for the exhaust gasses to move. The crank trigger has to be extremely precise to deliver fuel and spark on time and that is where RPM comes from. The data to romraider is just a snapshot taken of the values several times per second.

The tach is just an approximation for the driver to use, DO NOT trust it over the values you are programming into the ECU.

Would you trust the values RR provide you then? or just program her back to 7k and be done with it, I think I'm too paranoid

izergfx · 08-19-2012, 09:33 PM

Luke and ppayer both have points.

If you're logging with RR and you have a TON of parameters, expect the maximum RPM reading to be inaccurate in the lower gears (1st, 2nd, maybe 3rd on a 6MT) due to the poor sampling rate. However, if you take an RPM-only log, that's as accurate you're going to get aside from logging a CAN car with the OpenPort + CAN logger patch.

In any case, both are more accurate than the tach.

ride5000 · 08-20-2012, 09:17 AM

Quote:

Originally Posted by OC_Nooby

Would you trust the values RR provide you then? or just program her back to 7k and be done with it, I think I'm too paranoid

put it this way:

i've been running an 8k redline for nearly 10 years on an ej205.

do i play up there often? no. but i have, and i will on occasion.

lukeskywrx · 08-20-2012, 11:01 AM

Quote:

Originally Posted by ride5000

put it this way:

i've been running an 8k redline for nearly 10 years on an ej205.

do i play up there often? no. but i have, and i will on occasion.

It is not terrible on a car with shimless buckets, although the 205 valve springs are softer than the 207 springs made to spin that fast. Even on my 207 I rarely take it past 7K because the torque is just not there.

ride5000 · 08-20-2012, 04:17 PM

^^agreed. it's basically only touched during "no-time-to-shift-right-now" moments in the low gears.

lukeskywrx · 08-20-2012, 08:48 PM

Quote:

Originally Posted by ride5000

^^agreed. it's basically only touched during "no-time-to-shift-right-now" moments in the low gears.

LOL, "I WILL make this light!"

08-19-2012, 01:07 AM	#1
OC_Nooby Scooby Specialist Member#: 311781 Join Date: Feb 2012 Location: Canada Vehicle: 2003 WRX w STI V8	How accurate is your tach compared to RomRaider logger Hey Guys, I'm just curious to know how accurate your tach is. I ask because my redline rev limit is set to 6900 "on" and "off" at 6700 in RomRaider but with the logger my measured redline is 7200. That's also where I shift around. So I want to put my stock 2.5L redline at 7000. So the settings would be "on" at 7000 and "off" at 6900 (stock 05 sti map). I'm just worried that it would now record the redline at 7300-7400rpm. Not sure if the tach is really reading correctly. Could my tires cause this confusion? 225/50/16 (unsure of the stock 2003 wrx rim/tires). Its an STI swap in a WRX. Any help would be nice! * Registered users of the site do not see these ads.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

08-19-2012, 12:27 PM	#2
lukeskywrx Scooby Specialist Member#: 59837 Join Date: Apr 2004 Chapter/Region: SWIC Location: Arizona Vehicle: 2004 Spec-C Type RA What MAF? -Speed Density!	Trust the ECU, the RPM is detremined by the engine the wheels and tires have nothing to do with it. The error comes in when the signal must be converted to a gauge needle position for the tach display. There is no accuracy expectation on the stock tach, they are usually within +- 200 RPM. When I spin out to ~8K on the tach datalogs usually show ~7800. so mine reads a little high, but who cares.

08-19-2012, 02:37 PM	#3
OC_Nooby Scooby Specialist Member#: 311781 Join Date: Feb 2012 Location: Canada Vehicle: 2003 WRX w STI V8	I have a blue printed 10mm oil pump so I don't think I'll have any issues but what your saying is trust the ECU and put back the STOCK STI redline rev limit back? I think I will and record to see what it goes to then.

08-19-2012, 04:49 PM	#4
ppayer38 Scooby Specialist Member#: 234407 Join Date: Jan 2010 Chapter/Region: MAIC Location: Smithfield, VA Vehicle: 04 Self-tooned STi	RomRaider lags back around 150-200 rpm as you have to give time for the data to transfer from ECU to laptop. This has been focussed before if you would have searched. The tach is a calculated measurment made by the ECU, etc.

08-19-2012, 05:41 PM	#5
OC_Nooby Scooby Specialist Member#: 311781 Join Date: Feb 2012 Location: Canada Vehicle: 2003 WRX w STI V8	I tried to search via google and typing nasioc at the end of my search. Usually I have great success like that, not so much in this case.

08-19-2012, 07:55 PM	#7
OC_Nooby Scooby Specialist Member#: 311781 Join Date: Feb 2012 Location: Canada Vehicle: 2003 WRX w STI V8	Tach shows roughly 7200, RR shows the same. Ecu programmed for 6900. Lowered value compared to what it should be 7000 stock. Maybe I'll just put it back up to stock. I'm using a WRX tach with an STI swap. Doubt it matters but no need to be paranoid.

08-19-2012, 09:33 PM	#10
izergfx Scooby Newbie Member#: 308012 Join Date: Jan 2012 Chapter/Region: International Location: Evil Empire Vehicle: C# & Java Devs* PM me*	Luke and ppayer both have points. If you're logging with RR and you have a TON of parameters, expect the maximum RPM reading to be inaccurate in the lower gears (1st, 2nd, maybe 3rd on a 6MT) due to the poor sampling rate. However, if you take an RPM-only log, that's as accurate you're going to get aside from logging a CAN car with the OpenPort + CAN logger patch. In any case, both are more accurate than the tach.

08-20-2012, 04:17 PM	#13
ride5000 Scooby Guru Member#: 32792 Join Date: Feb 2003 Chapter/Region: NESIC Location: lincoln, ri Vehicle: 2003 GGA MBP 12.9 / 105+	^^agreed. it's basically only touched during "no-time-to-shift-right-now" moments in the low gears.