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data-logger help

ok i finally got my datalogger running, thanks keydiver. my vr4 has the following mods,K&N air filter, fuel pump upgrade, turbo xs mbc set to 17 lbs of boost. running on 94 octane pump gas did a few 3rd gear pulls to 7k rpm and these where the resultd from the logger:

injector pulse 25.1 ms
knock sum 13
o2 sensor .43 volts
t.p. sensor 95%
timing advance 12 deg.

can someone help me understand these better, maybe give me a few tips.and again thanks to keydiver for taking care of my ecu.


Those are really strange numbers. What RPM is that snapshot from?

My initial guess is that the car has some issues to work out. You shouldn't be getting that much knock on a 14b @ 17psi. 12 degrees timing advance is also very low, and inj pw of 25ms is insanely high. .43 volts from the O2 sensor is extremely low, and there HAS to be a problem if you're seeing readings that lean at WOT.


Well-known member
Jun 8, 2001
Vacaville, CA
O2 only .43V?? wasn't our car at WOT should be around .8-.9?
the injector is 25 ms?? I am around 11-12ms at WOT also.... oh well

yea im not really sure about the #'s thats why i asked. i will have to do another run to get the actual engine speed forgot that one. forgot to mention the car has 3" downpipe no cat and 3" exhaust. i did read thad the the o2 voltage should be higher.


ken inn

Well-known member
Feb 23, 2001
krum texas
assuming the log was a true flat out run to 7k rpm, the first problem is you are not getting 100% throttle position, which will make everything lean. second, the o2 reading is just about worthless on a wot log. if your inj pulse width was 25.1 at 7k, that would put the duty cycle at like 150%. i suspect instead you now have mas overrun. knock sum is not bad, but timing sucks. another possible mas overrun. first off, you should lower your boost to about 12, and then do some runs. max timing should be well above 20. the last run i did got me 28 deg @ 0 knock, the next one will get me 29, which is max. the fuel maps get a lot better once the tps is at 100%. so, imho;
boost too hi
mas overrun
tps not getting 100%, ecu not giving enough fuel
you also need to upgrade to the latest version, where inj duty cycle is now shown converted to percentage.

Which software are you using? I think the logging speed of the Palmenstein and that Russian program are pretty slow, so you want to turn off as many items as you can while logging. Like Ken said, turn the boost down and work your way up, watching the knock sum and possibly the O2, but the O2 voltages seem to vary alot from car to car and with temperature of the sensor. With the ignition turned on, but without the engine running, try to find out why you can't get 100% tps.
Good luck.

im using the tmo program. i will work on the tp sensor tonight and see whats up with it. does tmo have a newer program that will show the inj. pulse in percentage instead of Ms. well thanks for the replies.


ken inn

Well-known member
Feb 23, 2001
krum texas
at 7k rpm, 100% duty cycle is 17 ms. 25 ms is gay. when i had the stock injectors, running 18 lbs boost, i was getting mas overrun at about 5500. water injection had NO effect on it. turn your boost down, fix the tps, and i bet everything becomes normal. it's the mas, you've overflowed it. you can hack it, but you need bigger injectors and fuel control. you can 2g mas it, which is what i did, HUGE improvement, or maf translator. but you will still need injectors and fuel control. also, if dont have an adjustable fpr, the tuning is harder because of inconsistent fuel pressures.

quote:Originally posted by hecdws:
does tmo have a newer program that will show the inj. pulse in percentage instead of Ms. hector I think the only newer version is one that allowed you to log boost by connect a MAP sensor to the (unused) EGR temp sensor input. But, it was real buggy. I think Ken was referring to the Pocketlogger new version.
As Ken said though, at 7000 rpm anything over 17ms and the injectors are maxxed out. If you can, post a short log that we can look at. As the rpm's climb, watch what the O2's and knock are doing. At wide-open-throttle, the O2's should remain fairly flat at .91 or .92 volts. Try to keep the knock under 10. Do you have any way of tuning the A/F? Like an AFC, or adjustable fuel pressure regulator?

i will be getting a maf translator and running either 550 or 660 injectors. once thats done i will be trying to figure the logger out some more.
thanks for the help guys.hector

quote:Originally posted by hecdws:
i will be getting a maf translator and running either 550 or 660 injectors. once thats done i will be trying to figure the logger out some more.
thanks for the help guys.hector
Good luck with that. I guarantee you, if it don't run right with stock parts, it REALLY ain't gonna run right with aftermarket parts.

Howard's right Hector. You really should familiarize yourself more with the logger now. The translator is a wild card that throws in a whole bunch more variables. The better you can get it to run now, the easier it will be when you swap to the translator.
Jeff O.

since you don't have a version of software that shows duty cycle as percentages, you may find this page extremely helpful... i know i did.

for what it's worth (personal satisfaction, in most cases) a little searching on either this board or dsmtalk (can't remember which one i found it on) will leave you with the formula for calculating the percentages yourself. i wish i could remember it by heart, but my brains not functioning at the time. what it amounts to is using rpm to figure out the maximum possible time for the injector to be open, then dividing duty cycle by that.


Well-known member
Apr 22, 2002
Asheville, NC USA
Howard and Jeff-

It sounds like he has no way to tune the car and that's why he's getting the translator. If that's the case, what do you guys suggest?



Staff member
Jul 29, 2002
Chicago, IL
From Tuning Tips using the TMO Datalogger on

Duty cycle is roughly defined as the ratio of the amount of time a signal is "active" to the amount of time available for the signal to be active. A couple examples. In the examples that follow, the amount of time available for the signal is 20ms (milliseconds).

Signal is never active = 0ms/20ms= 0% duty cycle

Signal is always active = 20ms/20ms = 100% duty cycle

Signal is active for 8ms = 8ms/20ms = 40% duty cycle

Now, for the question of injector duty cycle. Well, the logger spits out how long the injectors are being opened in ms. What we need is the time available to the injector.

One might think the max amount of fuel an injector can squirt into the cylinder would be limited to the time that the intake valve is open. But that is a very short time relative to the entire four-stroke time that is really available. The injector can squirt fuel onto the back of the injector while it is closed and let it pile up there. This is actually done almost all the time at RPMs over 5000 (maybe lower, too) and is the reason why the intake valves get all crudded up over time with an accumulation of carbon. This is also why you should check and clean your intake valves occasionally.

Anyway, if we decide to use all four cycles of the engine and call that the max time period, we need to find the period of four cycles. That is simply equal to 1/RPMs times two, because it takes two rotations of the crankshaft to complete four cycles of the engine (1/RPMs because period is the inverse of frequency).

An example - what is the time available for the injector at 6000 RPM? Now, charting the time in terms of minutes just isn't convenient, so we first convert RPMs to rotations per second.

6000 RPM = 100 rot/sec

Inverting and multiplying by two, we get

0.010 seconds * 2 = 20ms

So, at 6000 RPMs, the time available to your injectors is only 20ms. But that isn't the whole story - it gets worse. There is a thing called injector dead time. This is the time it takes for your injector to respond to an "open-sesame" command from the ECU. It gets complicated because this time varies with the voltage at the battery. The ECU has a lookup table of dead-time vs. battery voltage and really is the main reason the ECU looks at battery voltage in the first place (there are other less important reasons). This time can range from 0.65ms to 2.1ms. Anyway, you have to subtract this from the time available to get the true time available to the injector.

Note: subtracted from this dead time is the time it takes to turn off the injector. But, when people talk of injector duty cycle, they never include this time. Well, they do, but they say things like, "Never run an injector over 80% (or 90%)." But such a thing is really kind of silly to say, as duty cycle is a ratio that doesn't take into account the times involved.

For example, would you want to run at 90% duty cycle at 2000 RPM?

1(2000/60) * 2 = 60ms

90% of 60ms = 54ms

Now, 54ms of fuel would probably be ridiculous for most applications. But I'm just using it as an extreme example. 54ms would probably also burn out the injector - I do not think you are supposed to keep them on that long. They do have a limit. You need to watch for that, too.

It just so happens that at 6000 RPM, 90% gives you 18ms, which leaves you 2ms of available "dead time", which is probably a good thing. At 8000, you only 15ms available, so 90% gives you a paltry 13.5ms (dead time of 1.5ms still probably okay on a good battery).

Of course, what is missing from this is what does 13.5ms mean, in terms of fuel? Not easy on the first generation, because 450cc/min injectors are further derated by the 1G low fuel pressure. That 450 rating is at 42.7 psi, not the 36.3 psi that the 1G fuel regulator uses. 450cc/min * sqrt(36.3/42.7) = 415cc/min injectors! Multiply this by 13.5ms = 0.093375cc of fuel. You need to figure out if this is enough for the air you are pushing through the engine.

Multiply this number by, say 11:1 A/F mass ratio and the mass of 1cc of fuel, and you get the mass of the air this amount of fuel will support. Now, if I had a way to flow-bench the MAF, I could figure out what the actual air-mass/sec rate is, and I could log it. And you could figure out if you are getting enough fuel into your engine to match the air.

Either that, or you could look at your O2 sensor readings!

BTW, by using the injector pulse width number along with the RPM value, I should be able to produce a nice duty cycle plot. I will add this data type in the future. But keep in mind what it really means. Personally, I find pulse width a hell of a lot more useful because it directly correlates to the amount of fuel entering the engine - duty cycle does not. -todd-

I have personally run my 450s on my 1g up to 27+ms and have a calculated duty cycle of 130% from 4K to 7500rpms. This seems confusing but it works. If you look at all the available charts and formulas we as DSMers may be running our injectors way too hard on PUMP gas.

450cc's @ 80% = 275hp, @ 100% = 342hp

550cc's @ 80% = 335hp, @ 100% = 419hp

650cc's @ 80% = 396hp, @ 100% = 495hp

720cc's @ 80% = 439hp, @ 100% = 548hp

This is using a B.S.F.C (Brake Specific Fuel Consumption) of .50lbs/hr/hp (that is .50lbs of fuel per hour for every horsepower it produces). It is recommended turbocharged engines run a B.S.F.C. of .60 or more which means even lower numbers. This is with PUMP gas. If you run race gas you can go with a lower B.S.F.C. but who knows how low, maybe .40 or .45. As you can see, if you are trying to run fast times off of 550's and PUMP gas you are probably running them too hard. Most people are probably running their 450's and 550s too hard on the street and are running them past 80% duty cycle. Is this a bad thing? Maybe, but you can't argue with success.

The one thing I will add is at WOT you want a value to be a smooth, straight curve. If the value is jumpy at all your injectors are not squirting a smooth pattern and you will get detonation from this. If you add fuel through your VPC, AFC etc. and you notice the injector open time did not increase at high rpms, you might be in need of bigger injectors as you're probably pushing the ones you have to the max.
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