Jump to content
SAU Community

Why R&r At Partial Throttle And Not Full Throttle?

Andi

By Andi,
in Engines & Forced Induction

 Share

Recommended Posts

Andi Experienced

Andi

Posted
Posted

Hey all, I just took the car for a proper test drive and I've noted a few symptoms when the car is on higher boost. From what I've researched so far it seems that I am definately hitting the infamous rich and retard, but whats weird is that it only kicks in at partial throttle (70%) but does not at full throttle. The car viscously stops like power is cut at 5000rpm and then kicks back in and then does it again towards redline.

This is the true effect of R&R yes?

But when at 100% throttle the viscous cuts do not happen, what happens instead is that it doesn't feel like the car is pulling smoothly as it should. There would be very small and hard to feel stutters and flat spots towards redline.

If the above at 70% throttle is R&R, then what am I experiencing at 100%?

So why does the power cuts happen at 70% and not 100% throttle?

Car is R34 GTT. Mods are turbo-back exhaust, fmic, apexi pod and profec B2 set to 12psi. I tapped up the coilpacks earlier today and with those runs above I didn't hear any actual mis-firing but scenerio 2 (100% throttle) could very well feel like it.

Thanks,

Andy :)

P.S - yes I've done a fair bit of searching over the past few days but couldn't find anything directly relating to my partial throttle problem so please keep the 'flaming' to limited if this has been covered before. :)

AdamsR33 Mentor

AdamsR33

Posted
Posted

ECU sees throttle at a certain point through the TPS but reads more air going in through the AFM, works out that there shouldn't be that much air going in at that throttle position and whacks in R+R. When full throttle is used, sees throttle fully open, heaps of air should be going in so... you get the picture?

Andi Experienced

Andi

Posted
  • Author
Posted

I get the first part, but at full throttle shouldn't the amount of airflow the AFM is sensing still be more then what the ECU would usually allow? Of course there would be a higher threshold for more air at higher TPS but one would assume R&R is even more likely to kick in at 100%?

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

100% you have "X" air, ECU is happy with that

70% you have "Y" air, the ECU isnt happy, as it expect "X".

Its relative of the throttle position.

So @ 70% throttle ECU expects "X", and your running 12psi so its getting "Y" and its cracking the sads.

Make sense?

At full throttle there might not be enough air to trip the ECU over as its expecting around that amount because your at 100% throttle, and because your at full throttle the ECU doesnt mind it like it did @ 70%

T04GTR Grand Master

T04GTR

Posted
Posted

turn the gain don on the boost controler.

il tell you whats hapening. part throttle theres more boost in the piping compard to the manifold...

ie: your got compressor surge. wich is your turbo trying to push more air than the engines using.

please stop calling tis problen r and r, i cringe at the very thuoght of it, that is the gayest term ive ever heard. sory but it shits me all teser wanker terms floating aroud and to every mechanic is painful to read. :P

AdamsR33 Mentor

AdamsR33

Posted
Posted
turn the gain don on the boost controler.

il tell you whats hapening. part throttle theres more boost in the piping compard to the manifold...

ie: your got compressor surge. wich is your turbo trying to push more air than the engines using.

please stop calling tis problen r and r, i cringe at the very thuoght of it, that is the gayest term ive ever heard. sory but it shits me all teser wanker terms floating aroud and to every mechanic is painful to read. :P

so whats the name for it then smarty??

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
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • niZmO_Man
      R32 Nostalgia

      By niZmO_Man · Posted

      From my youth: GTi-R clutch change is a massive pain. The gearboxes are fragile? But the car is super cool and I want one 😢 
    • niZmO_Man
      New R32 owner soon

      By niZmO_Man · Posted

      Remember this is 1988 tech.
    • TurboTapin
      R32 GTST - 600KW+ RB28/CD009 Build

      By TurboTapin · Posted

      Driveline vibration is resolved. I ended up loosening all my engine mount and trans mount bolts, giving it a good shake then retightening everything and it's gone... Let's just say I was surprised that fixed it.  I've been happily driving it around again but unfortunately put zero time into my direct port/constant pressure WMI setup. I'm on vacation next week, so I'll try and finalize it then.  On a different note, I spent all week fuel/ignition mapping 2x 216L V16 engines. Turbo's were burning glycol and we swapped them out for larger units. We also had planned emissions testing on site, so I figured I'd be there the same week to use their instrumentation and massage any emissions issues out if needed. This was a first for me. Fuel management is similar in certain ways to automotive (i.e air density as load variable) but very different in others. It's all PLC based and AFR's are controlled by air and not fuel. They use a control valve between the turbo and air manifold to control pressure which in turn controls AFR's. Due to this, target AFR tables supplied by the OEM are in pressures and not mass which really through me off. They use air pressure vs fuel pressure tables. I also relied on an O2 concentration sensor the emissions team had in the exhaust. Ignition timing was also all over the place and we were losing a fair bit of power. They're now happily sitting at 16-40BTDC depending on load. We were making about 1600kw at 900rpm at 90% load. Engines were running a lot smoother as well.    
    • Duncan
      1992 R32 GT-R Race Car

      By Duncan · Posted

      heh, aint no R32 ever meeting modern targa cage rules unless the driver is veeeery short OP, good luck with the sale, since its already in the land of freedom I'm sure you will find a good buyer.
    • Duncan
      Oil pan for RB25DET NEO Stagea "version"

      By Duncan · Posted

      meh, it was a good video, clear about the issue and how he dealt with it. A bit heavy on the RTV and very brave to put an RB in anything without rebuilding it first, but otherwise I thought it was good Dose, I'm not sure that having the pickup forward is a big issue; yes of course the oil could shift under brakes but the sump should never be empty enough for that to be a problem (unless you also have a higher volume oil pump, and that oil can't return from the head to the sump quickly enough)
×
×
  • Create New...