fuel cutoff during tip in of throttle

fvang · Post by **fvang** » Fri May 22, 2009 1:11 am

Hi

I have been trying to figure this out for quite some time now. It seems that when I tip in the throttle, there seems to be a threshold which cuts the fuel off and a threshold to allow the fuel to be back on. If I quickly tip in past that threshold, then the transition will seem smooth. I also get the jerky motions when I do a slight tip (if I get it right on some threshold). This seems to happen because of this fuel cutoff/turn on threshold.

Please take a look at my datalog.

I have a k20a3 block with z1 head & intake. All the rest are stock.

Post by **Hondata** » Fri May 22, 2009 7:12 am

The MAP looks a little low. What are your overrun cutoff settings? What injectors are you using?

fvang · Post by **fvang** » Fri May 22, 2009 4:24 pm

overrun settings are in the attached file. 17-15kpa.
injectors are stock - 270

It seems that the map is around 20kpa when no fuel. Once I tip in, there is fuel, which then makes the engine draw more air and the map drops down crossing some threshold which cuts the fuel. That threshold does not seem to be the same as the overrun settings.

I have also tried enabling the 0.5s delay in fuel cutoff, but the delay is not seen. I tried the button both ways(disabled or enabled).

I've played around with ignition - and lowering seems to help get rid of the violent jerks, but does not wipe it all away. It seems that I can only decrease so much to a point where it does not impact the jerk anymore.

I've set the tps to as close to zero already - dozens of time. Right now when it reads the tps sensor at ~0.5%. But it seems kpro rounds it to 1% which is why it is set at 1%.

Any help on this would be appreciated.

Thanks.

Bflaker · Post by **Bflaker** » Sun May 24, 2009 9:27 pm

I've been trying to figure out this problem for a while now. I've also noticed that Kpro rounds the TPS on mine as well. I wish someone would figure this out, cause now that I have Innovative Billet 75A's, the jerkiness is exxagerated drastically.

cranny · Post by **cranny** » Tue May 26, 2009 12:11 pm

from my experience this is a known Kpro problem and would be nice to see it as a priority as far as solution goes.

Post by **Hondata** » Wed May 27, 2009 6:57 am

In that case, can you link to any other problem reports?

For the original poster, why use the 270cc injectors? Why not the 310 cc injectors from the Type S? I believe the low MAP sensor reading is relevant also.

fvang · Post by **fvang** » Wed May 27, 2009 11:04 pm

270 injectors was used because it did not need the 310 - i never went lean at 8krpm full throttle. I believe the it only went to around 80% (from what I remember).

So, you are saying that the map sensor reading may also play a part in this. How low can I go(for overrun settings). I can try lower values, but from what I have seen this does not impact the jerking behavior ( maybe I am wrong, but I have not seen it). I do recall even do 10kpa across the board. Does not help. I also tried to figure out the vacuum at when tps reaches zero and set that to the overrun settings. I also tried setting that to 2kpa above & below my value. The jerkiness does not go away still. If there is a better method, please let me know. I also started to question the rpm values in the overrun settings, and from what I see - they don't correlate with the logs I captured - or maybe I just don't understand it.

From what I understand, the overrun settings will stop fuel once the map crosses the overrun settings - with the 0.5 delay or without depending if the "disable fuel overrun delay" button is selected.

Clear me up if this is not the understanding. Let me know what other kind of data you need, and I can try to provide it.

thanks.

Post by **Hondata** » Thu May 28, 2009 7:56 am

The low MAP reading is only an indication of the problem, not the cause. The question is why does the MAP read lower than a K20A2 engine? Is there a wiring difference between cars, or is it vacuum plumbing, or is the MAP itself different, or is it the throttle body?

Another factor is the injectors. For troubleshooting the ability to load a stock calibration would help - which would be possible using Type-S injectors.

fvang · Post by **fvang** » Mon Jun 01, 2009 12:03 am

For sure, I am mixing and matching.

I have an ep3- so ep3 wiring. ecu is prb. map is prb-type.

Is there a difference in the sensors between the cars, the sensor driving/reading circuits (the hardware), & behavior between the map uploaded to the ecu?

This might be the root cause of this problem. Is there a software solution to this? I don't want to use ep3 map because there are limitations in the options( there is no overrun cutoff map). I see that the map sensor is the same on 03 rsx and 03 si, so I will assume sensor reading circuit for this is the same.

For your question about why the lower map reading, do you think it is the above explanation. I forgot to tell you that I have a prc intake manifold, but I had this same problem even before the manifold change. Also, note that the head is z1 with ep3 k20 block. exhaust is ep3 stock. Don't you think that the mix and match can lead to a different map/vacuum response anyways or have you dealt with many of these k20z1head-k20a3block hybrids already and know from experience?

FYI - I changed over to the rsx map because I had more advanced features which I can play with - my engine is a hybrid- I don't match either ep3 or rsx completely.

Let me know your suggestion on what to do.

Thanks.

Post by **Hondata** » Mon Jun 01, 2009 7:25 am

Tuning wise, there is not much difference between your engine and a K20A2. Compression doesn't usually make any difference tuning wise. Put the standard injectors in, then load an unmodified stock K20Z2 calibration. If the engine does not run correctly, track down and fix the problem. Once everything is working ok, then start to tune the calibration.