When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
so I seem to have had this issue for a few yrs, it started with the powerfc and seems to have continued to my haltech.
right around 2500 rpms the car leans out (under vac cruising) till about 3000 rpms and seems ok.
with the powerfc I remember the afrs going as lean as 16-17! I always thought it was just tuned that way to save fuel (02 closed loop was deactivated)
fast forward a few yrs I now still seem to have same issue with my haltech elite. fuel map in that are required anywhere from 10 to as much as 20% more to get it to 14.7 as opposed to other part of map.
not chasing this issue I have replaced and upgraded fuel pump, injectors, rewired pump, upgraded coils, new wideband, new fpr. stock non ported tb
have tried several maps, and same thing. have replaced uim gasket, block off plate gaskets.
throttle plates on uim have been removed
still on stock engine harness which is a few yrs old.
looking at logs fuel pressure seems to be ok, tps seems steady
any ideas?!
on single turbo if it makes a difference
Last edited by AlexG13B; Jan 18, 2020 at 08:39 PM.
yea it requires alot more compared to other parts of the map to get to the same AFR
there is like a spike in fuel map in that section
it's a stock reman on stock ports with stock manifolds. only the plates were removed on the uim.
Maybe a longshot but if it's always at a specific RPM could it be a fuel pulsation issue? Are you running the stock damper or have an FPR with one built in?
Maybe a longshot but if it's always at a specific RPM could it be a fuel pulsation issue? Are you running the stock damper or have an FPR with one built in?
no dampener, fuel labs fpr.
I never thought about that honestly,
I may not be able to help but I'd be glad to look at it some.
What mods do you have? How much power roughly?
Do you have a picture of your base fuel map so we can see how it looks?
How about the ignition map?
Can you post your transient fuel settings and your injector settings?
What injectors are you running?
For reference, my car requires around 5-6% more at 3000RPM than the rest of the equivalent fuel areas. My car is heavily modified though.
I may not be able to help but I'd be glad to look at it some.
What mods do you have? How much power roughly?
Do you have a picture of your base fuel map so we can see how it looks?
How about the ignition map?
Can you post your transient fuel settings and your injector settings?
What injectors are you running?
For reference, my car requires around 5-6% more at 3000RPM than the rest of the equivalent fuel areas. My car is heavily modified though.
If you can provide the info above, or better yet a copy of your current tune file and logs we can help you out here. While every car is different, the data will be able to show us whether it is just suited for your car's fueling needs or if the fueling in that region is resulting from something else that isn't either setup right in the ECU file or of there is some other aspect of the fuel system that is possibly being overlooked.
I agree with the pulsation / resonance / harmonics theory and it might be the intake system rather than the fuel system. It's normal to have pressure pulses in the manifold as the ports open and close. At certain RPM and load the pulses can line up just right and sort of 'ring'. I've heard this can affect carbureted engines also, they call it fuel standoff. On a fuel injected system those ringing/resonating pulses can affect the MAP sensor line and the fuel pressure regulator's vacuum line. I've heard it can help to change the length of the vacuum line that feeds the fuel pressure regulator, or add a small restrictor pill (like a carburetor/nitrous jet) in the line between the manifold and the fuel pressure regulator. The datalogging from a PowerFC is probably not fast enough to catch it, but a Haltech should be able to log the MAP and fuel pressure sensors at pretty high speed.
For instance, here's a screenshot of a log from my RX7. This is a mostly-stock setup, stock engine with stock ports. Xcessive LIM, stock UIM and stock MAP sensor. Fuel pressure sensor is threaded directly into the secondary fuel rail so it catches lots of pulsations. The software doesn't show the min/max limits for the plot traces, but they are set to 0-200kPa for MAP and 35-65psi for fuel pressure so it's approximately the same vertical scale for both signals. The top plot shows the software-filtered MAP calculation (blue) vs the unsmoothed MAP signal (pink) which shows some of the pulsations. The middle plot shows software-filtered fuel pressure (green) and unsmoothed fuel pressure (pink). Bottom plot is AFR and primary/secondary fuel injector pulsewidths.
sorry I been busy. I did find a open vac port on back of uim.
didnt fix issue
I dont have access to map as it is currently locked but I do have a datalog I can post
It could be the time it takes between primary and secondary ramp up. Typically that occurs around 30ish% of total fuel capacity. Otherwise it could be the base map.
I dont have access to map as it is currently locked but I do have a datalog I can post
Sadly this sounds like an issue you will have to take up with the tuner or you need to ask them to unlock the map. It is possible it has been setup to try to provide the best possible mileage by being close to 14.7 AFR while in vacuum.
update to post.
issue still there
have fixed vacuum leaks, added extra grounds. rewired fuel pump and wideband. tried different elite ecu, and 3 different maps and still same problem.
and I started thinking, I believe I also had this issue with my older powerfc as well before going haltech. cruising it would go to 16 or 17 AFRs at times. I thought it was the map tuned that way but now I'm wondering if this is the same issue.
it does it running on primary injectors (these are brand new ID injectors now)
even just revving it in neutral to that rpm range would require 15% or more fuel to get it to 14 afr in those cells compared to adjacent cells.
anyone ever seen this issue before?!
If all the modifications have been the same and the different ECUs have shown the same symptoms, I guess the best question to ask you may be the simplest. What's your exhaust system made up of? (Down pipe diameter? lengths? pre-cat removed?) and what's the placement / location of your wideband O2 sensor? (Pre or Post Turbo manifold? Stock Location?)
There may be a chance that your exhaust is open enough that around 2500 rpm is where the exhaust flows it's best and the O2 sensor isn't getting a good reading but you're still in the safe zone for fueling?
I know it sounds a little left field, but I noticed something similar on my factory narrow band after removing my air pump and replacing the stock twins down pipe pre-cat with an RE Amameya 3" to 2" power expander dp. Idle AFRs read 20+ on my Gague, yet my eyes are burning in the garage from a fuel rich exhaust gas and flooding is more common now with the Air Pump removed. Anything above idle is reading correct AFRs though.
I've used 2 different 3" downpipes and 2 different widebands, 3 different locations. cutback has been the same though.
engine harness has been the common dominator, and the factory grounds. I've added grounds from battery straight to engine and engine straight to chassis. an exhaust ground, updated the firewall ground. battery was upgraded when I bought the car to rear bin.
uim has been swapped, still the same lim, tb and idle air control. same ffe fuel rails.
I've contacted haltech about situation and the guy I spoke to seems to think problem may be mechanical. he specifically mentioned to look at my throttlebody.
I have sweeped tps with multimeter and I didn't see any strange dips in voltage. it's a factory tb with no porting.
The guys at Haltec are usually on the ball, do you still have the double throttle actuator connected? It might not be operating smoothly or sticking open?
It can be cleaned out by removing it, putting some diesel into the port and hand pumping it. A full TB clean may clear it up?
it's got the stock primary and secondary plates.
coolant stuff removed. the other plates were removed and blocked off
the extra throttle plates on uim were removed
If you haven't already tried adjusting the injector firing angle in the Haltech software, the injector pulsewidths are low enough in your log that you could be spraying onto a shrouded side port if the firing angle is far off. Lots of info in this thread: https://www.rx7club.com/haltech-foru...inued-1101069/
It's not clear to me if this is a steady state issue or a transient issue. A loading dyno would be best, but on the street, can you put it in 5th gear at the rpm you are concerned about, preferably driving up hill, with throttle steady? If you are encountering this issue when TPS is fixed (no change, throttle stead), then it is a steady state issue. Fuel delivery is off or VE has a resonance point. If every time this is happening, you are going through the gears (transient manuever), it is probably a combination of steady state VE not characterized correctly and improper transient fueling. That's if it's not a mechanical issue. You've already covered a lot of bases with mechanical checks.
If possible you want to log each 2500rpm cell with a steady throttle for a good 10 seconds at least. That will tell you the steady state VE (try to keep air temp controlled). It's much easier to do on a loading dyno but that gets expensive.
It's not clear to me if this is a steady state issue or a transient issue. A loading dyno would be best, but on the street, can you put it in 5th gear at the rpm you are concerned about, preferably driving up hill, with throttle steady? If you are encountering this issue when TPS is fixed (no change, throttle stead), then it is a steady state issue. Fuel delivery is off or VE has a resonance point. If every time this is happening, you are going through the gears (transient manuever), it is probably a combination of steady state VE not characterized correctly and improper transient fueling. That's if it's not a mechanical issue. You've already covered a lot of bases with mechanical checks.
If possible you want to log each 2500rpm cell with a steady throttle for a good 10 seconds at least. That will tell you the steady state VE (try to keep air temp controlled). It's much easier to do on a loading dyno but that gets expensive.
yea it will do even do it with the car sitting still.. i hold rev at 2500-2700 rpms and it requires more fuel to hit that 14 afr target. driving steady down the road same thing.
if I load someone's map, at that range the short trims on haltech will go up 10-15% positive to get to 14 afr
