Possible Stupid Question..

[c34Florry]

Hey guys, wasnt quite sure where to post this question.. also im a turbo/nissan/stagea novice. Have only had the stag (rs4s) a week and she's my first turbo.. (ive learnt a sh*t tonne of things from SAU forums btw).

Okay so i was being a little lead-footed on the way home tonight and found that if i sink my shoe through the firewall, at about 4500rpm in 1st and 2nd gear mainly, there seems to be a noticeable flat spot in throttle.. almost like the revs hit a brick wall then recover. What is happening here, is it normal and how would I overcome this annoyance?

Thanks for everyones help in advance

→Lorry

Ps: only mod (that im aware of), is a 3" cat back

Edited February 23, 2014 by staglover

[KiwiRS4T]

Depends what you mean by a flat spot. There is a noticeable dip in power when the VCT changeover happens.

On the other hand if you lose all power momentarily that could be the ecu protecting the engine against overboosting (do you have a boost gauge? do you know if you are running standard boost?) which could happen on a cold night. That's called R(ich) and R(etard) when the ecu dumps extra fuel into the system and pulls back the timing at the same time.

[coparts41]

check your airfilter if you have a Pod , my sons R31 (rb25t) was sucking in the primary pipe feeding the turbo and giving him a flat spot, told him to clean or dump the pod and now all OK.

[c34Florry]

what's VCT? Boost cut makes sense as it feels like a total loss of power.. I just thought it would have come on a little bit later than 4500. I have a stock boost gauge, the one in the center console. Full boost has never been more than 355mmhg (6.8psi or .47bar). Plan on getting an A/M one but I cant find a 52mm that even slightly matches (any ideas?)

I have the stock airbox with a brand spankin new k&n panel filter. I've read something about a rubber pipe on the intake somewhere that collapses under boost, would that maybe something to consider upgrading?

Edited February 24, 2014 by staglover

[scotty nm35]

Mmm, I don't know if the K+N is a good idea, it could be worth cleaning the afm, just in case the oil from the filter has coated the hotwire.

Usually the intake starts sucking shut around 200kw, you can either stick a small piece of 3 inch stainless pipe inside it by cutting where the corrugations are and clamping it, which will help a little, or I can supply a nice 80mm custom alloy intake that will allow any power your setup can make, and fit up to the stock bov/breather/afm.

Don't bother with the silicone intakes on Ebay, they are worse than the rubber ones.

[RBrennan25]

I'm with scotty, those K + N air filters are bad news for AFM's. ditch that and go back to a standard filter and clean the AFM. Should be a good start

[wolverine]

Don't over oil them, spray some electrical contact cleaner on the AFM wire when you change oil.

There is no problem using K&N filters. There may be better options out there but if you have one then just maintain it correctly and it will be fine.

Pay Scotty for a properly designed and made intake pipe.

[c34Florry]

Hmm. I thought all filters were oiled but obviously not.. ive got a brand new stock panel, ill put that on instead and clean the AFM.

Interested in the hard intake pipe scotty. May as well fix the factory flaws. How much would one of those set me back?

[scotty nm35]

PM'd.

[c34Florry]

PM'd.

Thaks man. I found some pictures around forums, looks pretty top shelf. Do you make them yourself? Im super keen for one but as I just bought the car, im a little short on funds unfortunately..Id definitely like to hit you up for one in the near future though.

[scotty nm35]

Yes, I make them amongst other parts, mainly M35 though.

[c34Florry]

Okay.. different question, But related to the OP. Since this boost cut thing happened, I have irregular boost. Seems normal (6.8psi) when ot has just warmed up. After about 20mins of driving, it only makes 3psi or less. I had a listen for boost leaks, replaced a vacuum line for boost gauge but can hear a 'pssssssst' noise when I turn the engine off. Sounds like its coming from the front right (intake side) of the engine.. anything specific i should look at? So much sh*t going in and out of it, I have no idea what many lines do.. my knowledge of working on engines stops at hemi 6's.. so I've got 30+ years of technology to catch up on even if someone could point me in the right direction. Thanks in advance

Edited February 26, 2014 by staglover

[scotty nm35]

Make up an 80mm plug to put where the afm sits, on the corrugated rubber pipe off the airbox. Stick a compressor fitting on the plug and try to put 10-20psi into the intake. This will show up any leaks and you will find them fairly quickly.

[533 RYC]

HKS Super Hybrid panel filter is the best I've found. Three layered foam insert (course, medium & fine).

Got mine off eBay from a guy in NZ. Someone over here must sell them though.

Direct fit into standard air box.