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

    • Watermouse
      "Cheap" bolt on turbo on RB25DET NEO

      By Watermouse · Posted

      https://www.facebook.com/share/19kSVAc4tc/?mibextid=wwXIfr
    • Kinkstaah
      Airbox for +T

      By Kinkstaah · Posted

      It would be well worth deciding where you want to go and what you care about. Reliability of everything in a 34 drops MASSIVELY above the 300kw mark. Keeping everything going great at beyond that value will cost ten times the $. Clutches become shit, gearboxes (and engines/bottom ends) become consumable, traction becomes crap. The good news is looking legalish/actually being legal is slighly under the 300kw mark. I would make the assumption you want to ditch the stock plenum too and want to go a front facing unit of some description due to the cross flow. Do the bends on a return flow hurt? Not really. A couple of bends do make a difference but not nearly as much in a forced induction situation. Add 1psi of boost to overcome it. Nobody has ever gone and done a track session monitoring IAT then done a different session on a different intercooler and monitored IAT to see the difference here. All of the benefits here are likely in the "My engine is a forged consumable that I drive once a year because it needs a rebuild every year which takes 9 months of the year to complete" territory. It would be well worth deciding where you want to go and what you care about with this car.
    • GTSBoy
      Airbox for +T

      By GTSBoy · Posted

      By "reverse flow", do you mean "return flow"? Being the IC having a return pipe back behind the bumper reo, or similar? If so... I am currently making ~250 rwkW on a Neo at ~17-18 psi. With a return flow. There's nothing to indicate that it is costing me a lot of power at this level, and I would be surprised if I could not push it harder. True, I have not measured pressure drop across it or IAT changes, but the car does not seem upset about it in any way. I won't be bothering to look into it unless it starts giving trouble or doesn't respond to boost increases when I next put it on the dyno. FWIW, it was tuned with the boost controller off, so achieving ~15-16 psi on the wastegate spring alone, and it is noticeably quicker with the boost controller on and yielding a couple of extra pounds. Hence why I think it is doing OK. So, no, I would not arbitrarily say that return flows are restrictive. Yes, they are certainly restrictive if you're aiming for higher power levels. But I also think that the happy place for a street car is <300 rwkW anyway, so I'm not going to be aiming for power levels that would require me to change the inlet pipework. My car looks very stock, even though everything is different. The turbo and inlet pipes all look stock and run in the stock locations, The airbox looks stock (apart from the inlet being opened up). The turbo looks stock, because it's in the stock location, is the stock housings and can't really be seen anyway. It makes enough power to be good to drive, but won't raise eyebrows if I ever f**k up enough for the cops to lift the bonnet.
    • BuiltNotBought
      Airbox for +T

      By BuiltNotBought · Posted

      There is a guy who said he can weld me piping without having to cut chassis, maybe I do that ? Or do I just go reverse flow but isn’t reverse flow very limited once again? 
    • BuiltNotBought
      Airbox for +T

      By BuiltNotBought · Posted

      I haven’t yet cut the chassis, maybe I switch to a reverse flow. I’ve got the Intercooler mounted as I already had it but not cut yet. Might have to speak to an engineer 
×
×
  • Create New...