Guys,

I have an RTek 2.1 N351 ECU in my '90 NA. I've gotten the WOT tuning and most of the cruising areas of the map well sorted - I'm showing 13.1-13.3 AFR across the rev range at low vacuum readings (i.e. WOT) and am seeing 14.5-15 during cruise and slightly more rich in the light acceleration areas of the map.

Only issue I'm seeing is I'm getting a super rich condition at extremely small throttle openings and low RPM. RTek logger is showing low 11's A/F at 20-24 inches of Hg and between 2,500 and 4,000 RPM. I've pulled fuel in those areas of the map but it doesn't seem to change the AFR.

I did adjust the secondary injector staging point to a lower RPM (based on a suggestion by some forum members) so maybe that is an issue and I'll look into that soon.

Car also experiences some part-throttle bucking on occasion if that's a useful symptom.

Thanks for any insight.

John

 

Not sure if this is your problem, but when I was tuning my low rpm high vac areas I noticed that changing the -10 values affected afrs when my gauge/palm read 16-19 in/hg. Its like they are in -psi instead of in/hg... turbo2liter told me I was incorrect, but I clearly adjusted the 10in/hg and it affected my 16-19in/hg...

https://www.rx7club.com/rtek-forum-168/afr-tuning-methods-827389/page3/

 

The secondary transition is dependent on a few things; not just RPM. I believe something like -2 inHg manifold pressure is one of the requirements, so under high vacuum they should be staying off. You can always select the secondary flag option when data logging to be exactly sure when they're coming online.

 

I did some more logging and determined that I can just leave the staging RPM the same as stock.

However, the issue with the Rtek failing to adjust fuel at some vacuum readings is disconcerting. As a test, I tried playing with the fuel at idle. With the car fully warmed up I let it idle. Rtek is showing 850-900 RPM and between 16.5 and 17.5 inches Hg. I adjust the 512-1024 / 16-18 in Hg cell in the Rtek by 10 points, save the map, load it to the ECU and re-check the idle. No change. I revved it a few times and let it come back down to idle. No change in AFR nor injector PW.

What gives?

 

Log the "INDX" values to see what actual cell the ECU is using. Also keep in mind that the cells are interpolated so depending on where you are in the cell, the next cell may make a larger difference.

Additionally, there is no need to save the map and reload it into the ECU. I actually recommend against this. Saving the map on the PDA is fine, but no need to reload it into the ECU as all changes happen right to the ECU in real time.

 

I'll try logging the index and report back. Thanks.

 

Okay, that was the problem.

I fail to understand, however, why when the palm is showing 16-18 in Hg the index value references the 14-16 in Hg cell. RPM indexing seems to be correct, but boost indexing is one cell off.

Also discovered that the car wants to be around 13.0:1 AFR at and around idle or things get very ugly. Ugly as in it has a horrible lean surge.

I refreshed my Matlab code to reference the index values and compile the AFRs.

 

Following up on this...

I see MAP ("boost") values of -1 to -2 inHg showing up in boost indices of 13, 12 and 11.

I would expect +2 to 0 inHg to be index 13, 0 to -2 to be index 12, -2 to -4 to be index 11 and so on but it doesn't really work that way. I have to assume this is the ECU lagging behind the MAP sensor a bit.

Either way, I am getting good results now so I'm pretty happy.

 

Solo, I agree with what you are seeing and have noticed similar results on my RTEK 2.1 for an S4 NA. The relationship from index to actual load seem a bit fuzzy to me, but as stated above, there is a lot of interpolation between the cells. If you log the indexes, and tune based off of them, the RTEK works great.

I am going out to tune the car again tomorrow, and add a bit more timing. I added 3 degrees (leading and trailing) from 3000 RPM to redline and it really woke up the car. I will probably add a bit more in the midrange.

 

Yes, everything seems to be kosher now that I'm tuning based off the indices. The RTek is a great upgrade.

I don't think I want to add any timing because I have an S5 motor and the spark plug locations mean the timing is already a bit advanced, but when I get on the dyno it might be worth playing with. Did you play with the split at all?

 

No I left the split alone. I was unsure at first exactly how the RTEK adjusted timing.. I thought it kept the split constant, so I added 3 degrees to the leading only thinking it woudl advance the trailing automatically based on the split. The car felt noticeably better, but after doing more reading I added 3 degrees to the trailing map to retain the stock split value and the car felt better still.

My RTEK is great but my car has some weird fueling issues I have been fighting ever since I got the car. It is something electronics related.