Jrsc Euro ctr surging/fuel on closed throttle

[Lewvr6]

Hi,

New to the forum but had my Honda a couple of years- could really use some help with my problem as it is driving me mad currently.

I have a uk 2003 civic type r, JRSC, RC650 injectors, Toda Race Header, Fujitsubu exhaust, Gruppe M Induction, Kpro v1, tuned by a very experienced and trusted tuner over here. I cannot pinpoint when the problem started as it has been doing it for a while now, and I didn't (until recently) drive the car daily.

It has a problem with surging/bucking on closed throttle deceleration. I have tried replacing the TPS-set to correct voltage and carried out various other checks but to no avail. I recently started datalogging and notice that when the surge occurs-data shows that (for no apparent reason!) that the injectors spike from nothing( as i guess they should be) to 1.4ms and duty cycle is 3-4%. This occurs at any revs/speed but always on deceleration and totally off the throttle. It is usually some while after the tps reads 0 and the throttle is closed-so intially on closing throttle it is fine and behaves normal with injectors dropping then 3,4,5 or so seconds afterwards the injectors go 1.4ms and duty cycle a couple of percent?!

Below is a datalog that is very short but around 23-24 secs, the problem that I see constantly is occurring. Also the calibration.

Any help or suggestions of where to look much appreciated.

[Hondata]

Reset your overrun cutoff MAP tables to default.

[Spunkster]

The engine is not a proper operating temperature and that could have something to do with this. The highest temp is 168F. It should be no lower than 180-190 at operating temp.

[Lewvr6]

I have tried changing overrun cut-offs to 15 across all, which had no change. One thing I was curious about-in the various kpro calibrations (within kmanager), the table range goes up to 3000rpm, where my table goes to 8000?

The coolant temp I did wonder about, I removed a spoon low temp thermostat from the car last summer and replaced with a genuine oem Honda thermostat. Would you suggest the coolant temp sensor may be incorrect?

[Spunkster]

Is that the highest temp it ever gets to?

[Lewvr6]

In a couple of other datalogs-the highest ECT is 170, and all datalogs are after driving for a good period of time. I will check later and look at the temp, and will see if it gets hotter stood still after a drive (no air flow through rad).

It seems a good starting point, appreciate the input. What's the theory behind the mystery fuel injection relating to ECT? I understand that there is fuel compensation correlating to ECT (however this shouldn't apply in close throttle?), but even if its not at temp (for whatever reason), it should not be doing it at closed throttle decelerating?

Also still baffled at why it is behaving normal on initial closing of the throttle, then the problem is a few seconds afterwards. If decelerating from higher speeds with throttle shut, it can do that same injector spike 2 or 3 separate times-each time seconds apart.

To be honest, I am looking more for a mechanical/sensor problem, as opposed to something in the calibration/kpro. I am fairly confident this problem wasn't present when i bought the car (already with modifications and tune fitted) plus the tuner is well regarded, so have no reason to doubt the cal. itself. Would you agree that the calibration looks good, with no anomalies?

Thanks again for the help

[Lewvr6]

Ok, to follow up I monitored ECT this morning on a drive, and as seen above 170 it's where it sits whilst moving. If I park and idle afterwards it will reach 180 in a minute or so. Given that the ECT warms quick until 170 the thermostat is functioning as expected so I can't explain the low temp.

I can't remember the o.e thermostat temp rating off the top of my head?? but as said before it was brand new from Honda dealers around 6 months ago. It would look as though the temp sensor is giving reasonable and true data, just that it's running cool with airflow through rad.

Only other point of note is that I removed the Aircon at the same time as doing thermostat and coolant flush- usually the Aircon condenser(rad) sits I front of the engine rad so obviously flow through the engine rad is improved a fair bit now so better cooling.

Still unsure of how this relates, in calibration terms, to a closed throttle/0% tps situation? but would like to get it running at correct temp as a first job.

[Spunkster]

It may be a thermostat that is stuck open and its just not allowing it to warm up properly. You should let it idle from a cold start and record the datalog and see how long it take to get up to that 170 degree mark. That may give you an indication of what is happening.

[Lewvr6]

Will try that, how long would you say is normal?

[Spunkster]

do the test and post the datalog first

[Lewvr6]

Datalog below, as suggested.

It does seem a long time to get up there, however ambient is quite low here and it was just idling. Interested to see your thoughts

[Spunkster]

At about the 15:37 mark you can see that the ECT goes down. That could be the thermostat opening. It looks like this may be a low temp thermostat. You may want to see if your fan is coming on at that time. I do not see the ECU turning the fan on.

[Lewvr6]

100% o.e Honda thermostat straight from the dealer, picked up and fitted by myself, so unless there are different rated o.e Honda ones then it's just whatever the standard temp is.

I will remove and check it anyhow now and probably just replace it again.

[Corey872]

I tend to run around 172-174 on OE Honda thermostat in the cold, too. Don't see that as a big problem. Though I am actually a bit surprised your fuel shuts off. You need to have manifold pressure below the cut-off set point for injectors to cut off. You have a cut off set point ranging from 0KPa at 8,000 rpm to 1KPa at 1875 rpm. Your manifold pressure never drops below the low 20's, so fuel should never cut off. I suspect the only reason you injectors fall to zero is your air/fuel command (AFRCMD) and your air/fuel ratio both happen to be exactly 14.7. for most of the coast phase (possibly you don't have wide-band hooked up?)...the injectors back down to 'zero' because fuel demand is satisfied (AFRCMD = AFR), not because they are actually 'cut off' for manifold pressure.

During the 'blip' - for what ever reason- the ECU calls for fuel and AFRCMD dips to 13.6. Since the injectors aren't 'cut off', they fire up to satisfy this demand. The ECU then goes back to AFRCMD of 14.7 and the injectors shut off again.

Not sure what is driving you to put 0 / 1 in the cut off table, but something a bit above the highest pressure you see during coast would put the injectors in an actual 'cut off' mode. That would suggest something in the 25-28 KPa range for starters. If you get bucking at very light throttle, I would actually raise the cut off pressure slightly - you want a clear differentiation between on and off throttle, but not so high you get a massive 'hit' when the injectors do kick back on.

[Lewvr6]

Thanks for the input,

To clear a couple of points-here in the uk we have the PRA narrowband ecu hence the afrcmd/afr.

I have today ordered another new thermostat in a quest to get the ECT to the 180-190 that hondata seem to favour. It's seems the opening temp is rated at 172 alledegally so my 'warmed up temp does seem a little low. I think the relevance of the ECT relates to the fuel compensation tables as it needs to be over 172 in order to not compensate any value.

The calibration was done by a pro tuner here, so I have no idea why the cut off values are what they are. Your logic regarding these does make a lot of sense, and it is something I would be happy to play with.

Regarding the cut off values though- I am under the impression that surely if the tps value is 0 then injectors should be shut off by that value alone anyhow? Maybe I'm mistaken though.

Thanks