cewrx7r1

iTrader: (2)

Since I am bored at the moment "inbetween real testing", I started to experiment with the lag time correction for the primary injectors.

I have seen a couple of these done by XS for single turbos and thought I would play around some. XS made negative adjustments for the primaries.

Assumptions: since a larger injector has a greater lag time which means it opens slower, and APEXI uses a postive lag time correction, I assume that means the injectors are opened sooner by that amount, or later if the amount was negative.

Testing condtions: Air pump left connected and running but the O2 and Timing Idle controls were turned off. Fans fans tuned on for constant load and water temperature, engine was already hot from driving 16 miles, and engine idle speed at 850 rpm. Basic O2 voltage is .05 to .07.

First I entered negative values slowly working it down to -.12. At about -.10 the engine started to idling rough. Also the O2 voltage decreased while doing this to .01

Next I slowly entered positive values up to +.30. The idle actually got smoother at about +.10. O2 voltage was about .11. By +.30 corretion, the O2 voltage went up to about .60 but the engine was still smooth but not as much as at +.10 correction. It was still as smooth at my baseline stock was.

I left the correction at +.10 since the engine was smoother. If someone has access to an exhaust gas analyser, try this and verify what is happening. Is the O2 level changing due to better or worse combustion, and which way is the correlation.

SPOautos

Since your o2 went up does this mean it that the lag time corr values a/f depending on if you go neg or positive with the #'s? So is xs maybe running the negative values as a means of creating a leaner mixture??? If its changing the o2 is must be changing the mixture or am I missing something

Later,
STEPHEN

Tim Benton

iTrader: (1)

Did it have any affect at throttle tip in? cruising?

Tim Benton

cewrx7r1

iTrader: (2)

My assumptions which were not listed earlier are: If there is no misfiring, then; the negative lag adjustment which showed leaner O2 voltages meant that the fuel did not burn as well do to later injection timing resulting in more free oxygen. This is similar to using retarded timing at idle and low revs or extra fuel to help turbos spool faster. This is what XS did for two single turbos.
Helps turbos but is emissions dirty.

Positve lag adjustment meant better fuel burning thus using up more oxygen resulting in higher O2 voltage.

The O2 sensor measures free oxygen and the leaner(more oxygen) gives the lower voltage. Higher voltage means richer or less oxygen.

Besides the smoother idle with +.10 lag it also seemed to have a slightly better throttle responce.

I need more of you to do some testing and post your results. That is why I asked if anyone has access to a gas analyser.

twokrx7

iTrader: (1)

Chuck,

Did your experiment affect the idle vacuum? This would change the airflow at idle and could affect your O2 readings?

Kyle

cewrx7r1

iTrader: (2)

Vacuum was not affected nor was idle rpm.. I ran the tests a second time with the air pump also disconnected. Around +.30 the O2 voltage again started to go down showing injection timing was too soon. I now have it set at +.12.

The idle speed control only can be turned off by disconnecting the ISC connector. I think the PFC kept the the idle rpm the same thus idle vacuum remained constant because the ISC was still active.

Sidestick

iTrader: (1)

Does anyone have any idea what inj lag time I should use for 1300cc secondaries?

Thanks

twokrx7

iTrader: (1)

I suspect that changing the idle vacuum via changing the fuel injector timing/lag would affect rpm, the PFC would then compensate. Interesting thread though, I notice that XS changes the primary injector lag timing on their custom tuned PFC. I believe they change the PFC setting of 0 to a -0.12, punched out secondary 1300's are assigned a 0.16 ... big changes, anyone have an explaination?

Kyle

maxcooper

What is lag time?

My guess is that it is the time it takes to open the injector when you apply voltage to it. So, changing the lag time setting would probably change the amount of fuel delivered. Reducing the lag time (less positive, or more negative) setting would seem to lean the car out, and increasing it would seem to richen the mixture. I am not sure whether changing it would change the time at which the injector opens with respect to the eccentric shaft angle (it might, but it might not, depending on how the PowerFC times the injector pulses). I suspect that it doesn't change the time of the opening event with respect to the eccentric shaft angle, but rather just the length of the pulse.

-Max

cewrx7r1

iTrader: (2)

Max,


Lag time is the time from when voltage is applied to the injector and when the injector fully opens. LT correction affects timing of the injector pulse, not pulse width.

twokrx7

iTrader: (1)

What I think MAX is asking is ... does the ECU simply increase injector open time to account for an injector with a greater lag or does it tell the injector to open sooner to maintain the same start of fuel flow in time.

Dunno

cewrx7r1

iTrader: (2)

I redid my orig test but with the O2 pump also disconnected. This caused the starting O2 voltage to be in the .70s. The O2 voltage at -.12 lag corr was lower than at 0. From 0 to about +.20 the voltage went up. At about +.3 the voltage was coming down again. Thus I had a bell curve with the high point being the highest O2 voltage. If lag corr adjusted pulse width, the O2 voltage should have kept on going higher.

This leads to an indication of timing correction. If more of you do this test, maybe we could determine a pattern and know the truth. Same as I having been saying from the begining. It is an easy test but from what I have been seeing on this forum, most of you are lazy/afraid to do testing and increase our base knowledge.


One of my friends has suggested that I stop giving out free info/advice. After all, we have jointly spent about $3000 on test equipment so far and are not charging for what we find out.

So let us all start participating!

SPOautos

Well, over the weekend I played around with the lag time values. Mine were set from XS (-.12), I moved my pri up to .10 and if feels like it smoothed my throttle responce some. If I'm going down the road with my foot off the gas just coasting then give it just a little gas it's kind of jerky, that seems to have smoothed out a little. I wanted to check out my o2 but it seems to have gone nuts. My o2 reading is showing like 2.5 so I think its shot. It just started doing that this weekend and I know its not that rich. I need to replace it this week.

Sorry I dont really have much to comment on, I was kinda waiting till I replaced my 02 sensor so I could give you some more useable info.

Oh yea, it didnt seem to affect my idle any.

BTW - interesting thing happend this weekend, this is the first time I've messed with my lag time values and I moved them from -.12 up to .10. Since then my 02 shot and Sun my car flooded so bad I'm having to change my plugs. My car has never flooded before so I'm now wondering if the lag time had something to do with it. I had been driving my car for 30 minutes when I shut it off so it was warm and everything and it just wouldnt crank back up. You think there is a connection??? Or maybe my o2 sensor going bad had something to do with it? I know it all has to be tied in somehow.

Later,
STEPHEN

cewrx7r1

iTrader: (2)

Kyle has been doing analysis of what XS has done to two sets of single turbo maps, and how the DATALOGIT logs the PFC. XS is changing stuff all over the PFC. Things like how fuel and oil injection is affected by temp changes, plus other stuff. He says this makes it hard to really understand what they are doing, maybe trying to disguise "their" changes. Like change somthing whacy one place then correct it someplace else thus hidding the obvious. So that -.12 primary lag might be compensated some place else. That is his current impressions.

adax

iTrader: (2)

Yeah, my XS .dat file is posted on the datalogit group files section. They do change a lot of things, including injector overlap settings which are not clear to me at all and are likely influenced to some degree by lag time settings. Remember they changed the base fuel map a lot too. As I recall, the temp/oil changes were very minor. The only benefit I found to their setting was that the idle quality was better AFTER I changed primary lag time from -.12 to 0. Interestingly, their tuner code will activate the anti-lag feature in datalogit!

Alan

SPOautos

I think I'll put my injectors back to -.12 for now untill its more clear as to how it might affect other areas in the PFC. I've always been hesitant to mess with the setting of the XS map due to the way they tune things by adjusting other things. I dont know how all the setting interact with eachother and I'm always worried about changes since I dont really know how changing one thing is going to affect something else.

I should probably just load in another map instead of using this XS map. That way I'd be on the same page as most of the other datalogit users out there. I could just load in a stock PFC map and change my fuel and timing accordingly, that way I know what I have.

I think I'll download Adax's file from the datalogit group and see if our base map and other parameters are similar. I know that our timing was different at one point and we basically have the same mods. You would have thought XS would tune them the same.

Later,
STEPHEN

twokrx7

iTrader: (1)

Guys,

Be aware of the intake temperature corrections in the PFC. If you study the datalogit screens you will find that the base PFC maps will adjust fuel by a couple of percent based on intake air temperature. Why is this a concern? My testing indicates that our intake air temp sensor does little more than measure the temp of the manifold itself, not the air. Even when my water injection kicks in it doesn't register on the intake air temp!!!

For example, the stock PFC INJ vs INTAKE AIR TEMP correction pulls out 7% fuel from 50 degC to 10 degC and XS pulls out 14%. Be careful driving hard in the winter months after your car has heat soaked for a bit, the PFC will lean out the fuel while your intake air is nice and cool. Gotta watch the intake air temps, or, change the correction values, and/or relocate the sensor away from the manifold.

Kyle

maxcooper

Is the position of the injector pintle symmetric? If so, it does seem that lag time would not affect the amount of fuel delivered, but rather just the phase of the pulse.

If not, it probably affects the amount of fuel delivered for a given pulse length.

_____|----------|_________ (pulse)
______/----------\________ (just the phase)
______/---------|_________ (or also the volume delivered?)

-Max

adax

iTrader: (2)

FWIW, RC Eng. told me that when they enlarged my 850's to 1300, that they increased the "lift" a little in order to get the desired flow, and therefore increased lagtime. I assume they mean lift of the pintle? Wouldn't this mean that the pulse width would need to be increased since it would take a little longer for the pintle to complete it's travel? I really don't know enough about injectors to be speculating, I'll try to find the old SCC that had a great tech article about injectors.

Alan

SPOautos

Kyle,

What type of test did you do to check that. Did you use an additional temp sensor? Where was it mounted? How much difference was there between the 2 sensors?

I'd like a little info on that because I've speculated that the sensor heat soaking was the prob but dont have the extra air temp sensor/gauges to check it.

Thanks,
STEPHEN

Leadfoot

I may just be off today, but the lower the O2 the leaner it is, then lower O2 could indicate detonation? or possible detonation? Then if that is true, and the lag time correction advances or retards the pulse, then it would be possible to get max efficiency with lower settings, but not low enough to create detonation.

This could invariably givve better response and better gas milage? withouth the risk of detonation? I don't know.

I will try and play with the numbers a bit and see what happens, but it would also be nice to have a knock sensor available to see if it is also affected by the changes.

Am I screwed in my thinking, or forgotten something?

cewrx7r1

iTrader: (2)

My next test of this will also include the ISC solenoid connector removed. If all automatic engine idle adjusting parameters are prevented from working; then any manual fuel or timing changes should affect idle speed, vacuum, and O2 voltage. Then if you could adjust the primary injector timing, you could adjust for the best posible clean combustion. This would give you a higher O2 voltage because the fuel would be burning more completely and use up more oxygen.

If the timing was too soon or too late, combustion would be worse and more free oxygen would raise the O2 voltage.

These is where an exhaust gas analyzer would also benefit as you could monitor CO, CO2, and hydrocarbon emissions. Wonder if I could pay an inspection station to let me do some tuning as they ran an unoffical test.

spyfish007

I didn't notice too much of a difference when I adjusted up and down but I'll do some datalogging soon for some hard data.

j9fd3s

iTrader: (3)

most gas stations want to pre check your car before a smog test, at least here in ca. im sure if you paid them for a test or 2 they would let you play

mike

machinehead

Chuck, you are right, XS does a bunch of wierd **** to thier maps. One of those on the datalogit group are mine and I have been comparing them to the base and the other XS maps. I am very curious to see what your friend comes up with. The better we can understand this the better off we all are. My maps for example they added aditional retard with air temps over 60C plus added oil injection. Kepep us posted on the results.