Jump to content
SAU Community

Recommended Posts

Hey folks,

got the rb20 back in my rx-7 and sourced a stock ecu to replace my mines tuned ecu. Seems to pull as hard, runs about 15-16 afr's running down the road and quickly changes to 10-11 when throttle is opened. If you back off it richens down to 8's and goes to the 14.5-16 again.

Which I can live with, car pulls very hard. and creeps around 14 psi high in the rev range. However the car feels like it is completely shutting off at about 6000RPM in 3rd gear and has done this consistently since i have swaped the ecu.

I do not have the transmission wiring wired as I never got the lower harness. As well my rx7 dash is run by the speedo drive and does output a signal to the ecu.

I am thinking it is one of three things.

AFM air flow cut

knock sensor

speed sensor.

Anyone know of a bypass or way to check these? if not I will have to put the mines ecu back in for drag weekend.

Rx,

Link to comment
https://www.sau.com.au/forums/topic/458133-boostfuel-cut-6000rpm-rb20det/
Share on other sites

The most likely suspect is TP cut, which is what you are calling AFM air flow cut. There is no way to bypass this without Nistuning the ECU, so you can raise the setting for it in there.

Knock sensor will not do a "cut". It will switch you first to the knock maps then it will go even further and cut ignition timing right back, but it will not actually "cut" the engine.

Speed sensor will do it at 180 km/h on a stock ECU. Assuming that you have the RB20 gearbox sender and drive cable and RB20 compatible speedo head from a Nissan installed, and that the wiring from that speedo head is connected to the ECU, then you could be having this cause a cut. But it won't do it at 6000rpm....it will do it at ~180km/h (depending on diff gearing). And I don't think it likely that you have every link in the chain I described above in a transplant to an RX7.

TP cut as in Throttle position???

Will the speed sensor not wired have the ecu reading different signals? or just one?

As I stated the mines ecu had never gave me this problem. And as far as I know they heighten the rev limit and delete speed cut, anything else? That's why I think it is speedo related.

I have no power steering, no clutch fan, no ac, rb25 turbo, fmic, ffp. fuel pump, 3" exhaust, etc. Pulls hard and was beating an overboosted tuned mr2 last night until boost cut at around 14psi.

TP means Theoretical Pulse. It is the fundamental load index for all maps in a Nissan ECU. It is driven by AFM signal, but it is not just the AFM signal.

The Mines ECU will have had the TP load limit increased along with those other changes.

It will be the TP limit, no alternative.

Okay, Thanks man. Explains a lot!

I've ran that mines ecu for a while and seems to work fairly good, I like the stock with the lower rev limit but I may switch back. Are they as bad as everyone says they are?

I have three ecu's; a mines tuned, stock and a chipped one for 555cc injectors and z32 maf which i do not have.

Thinking of nistune but cant shell the cash now.

Can you tell me anything from my Afr's above? Seems they should not be that lean cruising or rich as i back off the throttle.

Rx,

Mines ECUs are not inherently "bad". The problem is that they have been chipped to suit a particular set-up and cannot be tuned to suit your set-up. Some people say "my car runs great on my Mines ECU" when really all they know is that it starts and runs. If by some chance it does suit your car (and you can only really be sure of that by sticking it on a dyno to make sure AFRs and timing are correct) then you can run it.

Those are my thoughts skyrine, Thinking I'll post them up on ebay unless a member wants one

Timing is the unknown for me, my wideband shows it running rich in boost around 10's with 30psi fuel pressure. keeping the throttle in spot reads 16's with it though.

RX

What STATUS has said is true. There is a lower TP cut point for zero speed conditions, which is why the old Skyline trick of cutting the speed signal wire to beat the 180km/h speed cut problem was not a good solution. You might still hit a normal TP cut even after restoring a speed signal to the ECU anyway. This is because running even the stock turbo at 14 psi with enough other mods (exhaust, cooler, etc) can get you to that point.

Search for posts by me on the topic of the voltages and signal types involved in the speed signal. The speed signal sent from the Skyline dash to the ECU is a square wave 0-5v signal. If you can fake that then you can keep the ECU happy. But I still reckon that Nistune is required.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Yeah good luck out there! Will be good to see a mighty GTST going harder than the GTRs
    • i will be there 😁
    • Hello!  i just finished manual swaping my r34 skyline with a r33 rb20de box(RB71C)box  When the car is running it squeaks crazy loud and it was smoking from the gearbox area. The gearbox is fine it was tested. The clutch slave cylinder seems like it doesn't fully releases the clutch. I want to ask if this noise is from the throw out bearing or could it be the clutch assembly or disk att.xFliq87Gzw6kImKBVqDebXkj0fBqymk0JaYeP3_3SlM.mp4
    • A few small updates since the previous post and lessons. I decided to do a little interior light upgrade on the 110. I quite like the iilumo items, even if they're a bit of a premium over other brands. You'll also note the Stedi Fogs, that will go into the S15 fog lights as I needed to match the bulbs since I got the new ones earlier. I hope they fit as the body is quite a bit longer than your normal bulb.  Annoyingly, I managed to trip the fuse, which normally wouldn't be an issue until I located the fuse. I can't say I've ever come across this. I had lucked out that someone nearby had a spare, but oddly enough Toyota dealerships seem to keep this in stock. I ordered some to keep in my stash and as luck would have it, someone else nearby tripped the same fuse so I passed on the favour.  I also did a little service on the 110 ahead of some additional work coming up. It's been annoying that Goleby's stopped carrying this particular HKS filter for the 110, so now I need to keep them on order from Japan. I also took the opportunity to install a bash plate and number plate riser. The plate riser is such a cheap but nice fix to help really tidy up the car. I'm tempted to now also replace my headlights, on this car. Both items were from Project Aero.    I also needed to replace the rear tyres on the 110, and after trying to get it aligned learnt that I need to replace some bushes in the front end, so that's next.  Closing out this update with a nicer picture as always! 
    • Yeah mate, never miss it.
×
×
  • Create New...