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

Andi

By Andi,
in Engines & Forced Induction

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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??

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