Crazy turboshuffle of doom.

[Samwest]

Hi guys, i have really big problem.

I went to my mapper yesterday with my new mods for the season:

1. HKS hardpipekit.
2. Tomei poncams B
3. NISMO AFMs

I have 2 problems right now:

1. When driving the car of boost it goes really really strange, its almost undriveable, a bit lean to, but as soon as i come on boost the car starts to shuffle, when it shuffles the AFR goes in step with the shuffleing and it goes much richer. I need to change down a gear to get rid of the shuffle, to build fast boost.

On WOT the car pulls like a train but if i manage to make it to hold the boost for a longer time it starts to shuffle either way.

2. When pressing the throttle after a WOT run when pressing the clutch the engine RPMS dips down for about 2-3 secs anf goes really rich, then work its way back to normal rpms and afrs.

Need help whats my problem here? leaking boostpipes? leaking vacum? AFMs not setup properly?

[Frankyy]

If you Havnt tuned the car with the nismo afm, then that's 1 thing
Also sounds like a boost leak in the Ic piping and what about fuel? What kind of fuel pump? do you have a fuel pressure gauge?

Can your car build any boost at all?

[NismoS-tune]

I'm surprised no one answered yet on the gtroc post you made!

Anyway what turbos? Is the car tuned by a competent person (tuner car obviously better to tune after every mod), but more importantly he should be able to tell if the issue is a sensor I'd think.

If your turbos are -10 and your engine is rb26, there will be some shuffling but it sounds like you have something else causing issues. I recall when my timing was way out and ran way rich, my turbos shuffled all the time, even idling

What ecu? The pfc doesn't have a predetermined setting like the oem or z32 mafs.

[Skym]

Going by the mods you have had done, fluctuation in A/F ratio can be caused by a intake airleak near AFM's (loose intake hose clamps on AFM's or piping after AFM's) and usually happens at low rpm only (makes engine stutter). It's probably stuttering which is causing the shuffling.

[Samwest]

Okay guys thanks for the replies. Here goes my theory:

ive installed my oilcatch breather hoses wrong. Ive connected one hose from the hks inlet pipe(rear turbo inlet) and connected it to a open catchcan breather with filter. This way air is sucked in to the turbo after the AFM therefore the fuel/air mix gets ****ed and changes for the three rear cylinder. wich leads to one turbo spooling different then the other. Also this could explain why it dips when light rev on neutral?

[Samwest]

Going by the mods you have had done, fluctuation in A/F ratio can be caused by a intake airleak near AFM's (loose intake hose clamps on AFM's or piping after AFM's) and usually happens at low rpm only (makes engine stutter). It's probably stuttering which is causing the shuffling.

Really impressive how you managed to guess the problem by just reading my description! Dont know how my mapper missed it or even i

[Skym]

As far as I know it's a common known problem (even I have encountered this stuttering problem with my car a few times when exiting motorway and had to replace rubber intake piping due to common cracking problem under intake hose clamp, inbetween ribs), even mechanic at Nissan Dealership (Skyline specialist that sells, services Skylines) I talked to knew about that airleak problem (also others I have talked to who deal with Skylines alot have encountered this problem) and said it was common with Skylines.

When I get out of the blue missing / stuttering from engine (similar to coilpack failure), it's one of the first area's I check (I check it nearly every time, as intake hose clamps can work themselves loose).

If want to stop intake airleaks being caused by intake hose clamps, you need these type of intake hose clamps (as used on Gibson Group-A R32GTR racecar in link below) that are not cheap -

http://www.speedhunters.com/2013/02/godzilla-attacks-the-gibson-group-a-gt-r/

Also this type of problem (too much air to MAF's caused by reversion / air reversing direction from turbo's, towards MAF's making MAF voltage fluctuate) is also common with vent to atmosphere BOV's, hence why HKS made this device -

http://www.hkseurope.com/electronics/sld.asp#eids

[Samwest]

The car is mapped now
But the shuffleing is still there, i advanced the inlet cam 6 degrees and it helped very much. But still there, i hate shuffle, what should i do to make it stop?

[RXXXII]

It sounds like you need a minor modification to your "twin turbo" pipe. RB26DETT turbos run in parallel. This means that they boost at the same time vs one boosting then the secondary turbo kicking in afterwards. Because the stock "twin turbo" badged pipe on the hot side of the engine bay is not divorced (splitting airflow between turbos) when you constantly boost at certain PSI you will feel the turbulent shuffling of airflow from the front turbo's charged air hitting the rear turbo's charged air.

The fix is simple. take the "twin turbo" pipe off... find a fabricator that can cut a slit in the pipe and weld an aluminum sheet within that slit to split the air between the front and rear turbos' charged air.

If you have more money spend. HKS and GREDDY make "suction kits" that include a different piping setup for the hot side of the turbos... each turbo get's it's own pipe for airflow and the long rubber Intercooler coupler next to the air filters is replaced by an aluminum "Y" pipe.

Hope that helps.