I have been working over the last three months to resolve a long-standing problem of acceleration enrichment on modified FD's using aftermarket ECU's, in particular the Power FC, but this analysis and subsequent applied fixes may also help solve any acceleration problems using other aftermarket ECU's. What I have found through my testing and analysis of acceleration enrichment is that this function is highly dependent on the air flow or volumetric efficiency of the car's systems, including the engine (mostly porting and 2 mm vs. 3 mm seals), intake (including piping, manifolds, and turbos), exhaust (including manifolds, downpipe, cat, cat-back). My current setup is a street-ported 3-mm apex seal 13B, extrude honed LIM and UIM, RC ported throttlebody, Efini crossover pipe, Hitachi HT12-KAI SP turbos, extrude honed Greddy elbow, Autoexec airbox, and Australian dual bank U-type SMIC required pretty drastic changes to two of the three tables.




Mike

 

I have had this issue as well. Thanks for taking the time to research this!

 

Thanks for your hard work figuring this out and sharing it! My car has always gone lean on throttle tip in, stock ecu, pettit ecu, and worst of all power fc. I tried your setting today and it was darn close to fixing my car. Mid throttle tip in was perfect. Heavy throttle tip in was a bit rich. And light throttle tip in was still a bit lean but better than before. It use to go lean under all throttle tip in situations. I'll have to re-read your article on how to fix the light and heavy throttle without screwing up the mid throttle.

 

For light throttle, drop the TPS (V/t) lower in the last row. If you started at 0.049, drop it to 0.044 or 0.039. If still lean, you may want to instead increase the Setting in that row to 0.30, which is 30% more fuel at that level light throttle level. Or even both. For heavy throttle, I would raise the TPS 0.503 to .552. Try these things. I found after awhile, you tend to get a feel on what to do and how to balance everything out. Isn't it awesome to have the car accelerate like you always wanted it too. Quite fun!!!!
Mike

 

Yep dropping the TPS (V/T) in the lower last row helped my lean tip in at light throttle. I kept dropping it till I hit 0.010. My car use to peg lean at 20 A/F for a split second with about 5% throttle. Now with 5% throttle it maintains the previous A/F within a few points. 50% throttle is still good. Your numbers for 100% throttle fixed it going a bit rich. Now I'm only getting a lean spot somewhere between 5 and 50% throttle, maybe because I had to go so low with the light throttle number? Few more test drives and I think I'll have it dialed in. My RX7 is starting to drive like a modern car, no stumbles, surging, or hiccups. We will see what FC-tweak says about my map soon too.

Thanks for the help
Ryan

 

For all of you making these changes in your acceleration enrichment, let me help you by helping me. Give me feedback like ryansport22 did so that I can help come up with different tables for different modifications levels. I cannot know this without other's help since my car is unique in it's air flow mods as compared to almost all others. This way I can have set guideline tables listed for each modification level. I will then revise the write and to include all of these guideline tables which will make it easier for everyone else and easy to change the AE tables with less guessing before testing. Differences in mods include engine porting (small street, large street, half-bridge, etc.), manifold porting, intake honing or aftermarket LIM, throttle body porting, single vs twin turbo, downpipe, cat or not cat, etc. So if and when you report back, please give me a short list of your mods. Also, I found that all the mods together affects on air flow can be approximated by your idle vacuum value. This approximates your volumetric efficiency at least at low air flow. In example, my car idle at -310 at 780 rpm near sea level pressure on my current rebuild. My old setup was -410 at 780 rpm, much less air flow efficient and therefore would need much less drastic changes to the AE tables.
Mike

 

Ryan,
I would not go that low on TPS for the third row. You will dump fuel a lot all the time even with very little gas pedal change. Instead, go back to around 0.024 or even higher and instead raise your Setting value to 0.30 (30%) or even 0.40 (40%)like I use. Then, when you need fuel, you get it at the right time rather than always dumping more and you get more at the exact right time. For your lean WOT, I would drop your middle row TPS value down some, mine is 0.122 and then correspondingly decrease your fuel (only a little like 0.5 mS) in that rpm to balance it out a little. This will tend to take care of the WOT, which seems weird, but the reason why is that you add more fuel earlier in the cycle as the pedal is going down and therefore need a little less as you approach WOT. Put your first row TPS back to 0.503. It is all a timing thing if you get what I mean. Eventually you will get the hang of it.
Mike

 

Ok I'll try that next test drive. I'll post up my full tables once I get something working correctly at all points.

Car- stock ports, non sequential twins, 3 inch exhaust with high flow cat, intake, SMIC, idle 800 rpm with -19 in/hg near sea level.

 

Ryan,
One thing I forgot to ask. When do you go lean at WOT? If it is 300-450 mS after the AE cycle starts, if can be you need more fuel later in the cycle. If you can log you can tell for sure. That would mean you need to make the AE fuel last longer and need to drop your Decay value some. If using 0.5 then 0.4 for that rpm. Remember, when you do this you will add to the total fuel at all levels of enrichment using this rpm, even mid and low pedal pressures will see more total fuel, and you will need to adjust accordingly your Amount value, which will need to be lowered some. It is again a big balancing act. I wish it was simple but it is not. That is again if all of us can now come up with guideline tables that would work for 90% of the people in that mod level, this would be much easier to do.
Mike

 

Stock 5.08 map went lean at full throttle but your first suggestion fix that just a bit rich. Your second suggestion was spot on for full throttle. Most of my problems in the past and less so now are with real light throttle inputs. FC- Tweak has some interesting ideas too. I plan on doing some logging tomorrow.

 

Ryan,
In my write up look at the Addendum A tip for loggers. See exactly at what light throttle you go lean. Then enter that value for Tps. Then go 30% or 40% for Setting.
Mike

 

I finally got my datalogit a few days ago, now I'm just waiting on the AFR gauge, that I ordered to arrive and it seems I'm going to need to acquire a new laptop since my current laptop can't last long enough on its own to log data.

I'm looking forward to trying out the improvements you've found.

 

Does this doc/thread only apply to twin setups?

 

Any setup. The changes in the tables are related to improved air flow efficiency from a completely stock car. Apexi almost certainly used a completely stock car to develop their tables. Most modified single setups would likely benefit even more than a twin setup since they are more air flow efficient.
Mike

 

 

Anyone on the RX7 Yahoo tuning group may have already seen this but for those not in that group, Xavier Borg is a very knowledgeable technical guy on that group who has developed a program called FC Tweak to help anyone using the Power FC improve their car's performance by fine tuning all the Power FC's maps and tables and eliminating any major red flags in timing, fuel delivery, ignition, etc. The reason I bring this up here is that he found that that TPS V/t default setting in the last row of the Inj vs TPS1 table is grossly inadequate as compared to AE (Acceleration Enrichment) standards used by most cars for the lower threshold to begin AE. The 5.08 default value of 0.098 compares to a standardized automotive value of 78%/s. The normal range given by Xavier is between 15%/s to 30%/s to begin AE on most cars. The default value is truly bad except for a completely stock car, if even that. My current working TPS V/t value of 0.02 compares to a standardized value of 16%/s, right in the lower portion of the desired range. My current recommended starting value of 0.039 for everyone corresponds to a standardized value of 31%/s, right at the upper range of normal. My extensive testing was right on the money and it is supported by the industry standards as per Xavier.
Mike

 

Bump.

yahoo groups moved to google groups

PM arghx to join.

Thank you mikejokich for this AE quick guide.

I will play with my values tonight - hope it helps.

FC-Tweak changed some of my settings from a tune I got from Daniel Kuo, but I have the lean throttle tip in issue no matter the rpm I am at.

I can still edit - I played with it tonight and I loaded both of your "recommended starting tables"
in the following table FC Tweak had an issue.
inj vs Accel TPS1
TPS (V/t) 0.039 = OK
FC Tweak flagged the setting 0.20 and said it was an invalid TPS setting? FC Tweak changed it to 0.30.
My throttle tip in is much better at idle, I will drive it this Friday 11/12/21 and see if the lean tip in condition went away on the move.

Thank you so much for your hard work and sharing this with the community.

Ben

 

Even though I had for years decently tuned the idle to cruise areas of my maps, FC-Tweak has made this so easy and much better than I ever had it.
It actually goes in and modifies other injection and timing related tables that were previously untouchable.
It is a great piece of software.

 

Update -

This AE quick guide solved my issue !!!!!!!!!

with the help from this AE quick guide table
google drive, Chucks PFC tuning notes and the people there
Apexi PFC / Datalogit / FC Tweak

Car runs amazing
Tip in is good at all RPMs
No more lean on Tip IN
Freeway cruise is 13.5 ish but WOT is in the mid 11's
Transitions great, no stumbles, hesitations - no weird stuff
Warm up and IDLE AFRs are good
Hot Starts are good

I have not done any Auto-tune yet, but it runs great as is.

I am on the 7 pound spring.

FC Tweak has my car running like a Pro tuned it.

Just so someone knows how good FC Tweak is and the payoff from all the hard work by people on here, my cars has the following.

BNR Stage 1 twins (drop in chra's), ported waste gate
Unknown Down pipe, RP high flow cat, Apexi N1 Dual
AzEKnightz custom solenoid rack - under the intake manifold
Used engine with external coolant o'ring leak near the rear exhaust port, ported exhaust and smoothed intake ports
550 pri, ID2000 sec with cj motorsports secondary rail with fuel pulsation damper, RP high flow fuel pump with fuel relay mod
new stock coils, #9's for leading and trailing, HKS Twin Power, custom MSD spark plug wires
Xcessive LIM
Rotary Extreme Twin Track Vm kit.
Fast IAT in Greddy elbow
Apexi PFC, FC Black Box Datalogit, FC Tweak Pro version.
Greddy Pfofec B T-eed into both the waste gate control and pre-control.
ISC, Thermowax and warm-up cam working great.
No Air Pump, No OMP, No emissions, no factory boost waste gate solenoids.

Thank you so much again for your hard work mikejokich

 

Hello,

I've used your settings on my FC. Initially just a copy paste, just had a decent drive since I've done this.

It picks up way nicer from a dead stop so I'm pretty pleased on that.
The drive today did show some areas that need a better look at but not sure when I'll do that.
WOT 1st, 2nd, 3th, it misfires a bit at 2nd at tip in. And tip in while cruising felt a bit slow or delayed.

engine specs
13B-T series 5, streetported
FD UIM and TB
Custom V-mount
Open exhaust
FD PowerFC
Factory modified coils due to FD powerFC, with ignition amp
old stage 4 BNR turbo

 

Since many of our engines are modified differently, our accompanying intercoolers, air intake systems, etc., are all different, you will have to adjust the settings from my original post from several years ago. If you use a wideband AFR meter, use it to do the adjustments, otherwise it is just trial and error (way harder to do).
I myself no longer have the same engine and I am currently installing a new engine that is more modified than my old engine. I will adjust my settings to match the new engine once it is up and running.
Mike

 

Yes, and it had to be expected.

I've got a wideband but it's stand alone and doesn't have a very high refresh rate. So it will probable be messing around unfortunately

 

consider getting FC-Tweak, it's game changing

 

This is an excellent guide, and I really appreciate the effort that went into it. I believe this information could be valuable not just for RX-7 Power FC users but for the wider community as well. I was wondering - have you considered using a platform like GitHub to create a shared knowledge base? This could help ensure the information remains accessible over time and allows more people to contribute. I'd love to hear your thoughts!