Project Rb31dett. The Development Of My Open Deck Rb Engine And The Quest For More Torque!

[GTRNUR]

Update.

The engine still continues to go well and has a little over 500k's on it now. Ive been working on the tune a little in the response zone around 2000-3500 rpm, still keeping boost below .5 bar. Its a hoot to drive, but now its more responsive Ive encountered the next issue.

At light load around 2000 rpm in 6th the turbo's start to shuffle wildly. As in 1 to 1.6 volts variation between the two maf sensors, and they do this see-saw thing back and fourth. This does not help the tuning process at all!

The problem is less noticable if I start to load the engine up above 2400 rpm. Im hoping that the shuffling is being made worse by the fact that ive got the wastegate actuators set pretty loose at the moment, so im going to re-calibrate and tighten them up to 1.1 bar tomorrow. I suspect i'll have to do the twin turbo pipe modification as well to help control the shuffle, or alternatively invest in the sexy nismo intake piping... time will tell.

[zebra]

Is there room to fit an X-Pipe or a balance pipe for the intake, I have a feeling it would well and truly fix the GTR turbo shuffle.

My soarer runs a single intake pipe and has tiny turbos but I dont get the Choo-Choo train.

So I think that a balance tube after the AFM's would fix the issue.

[Deano45]

Update.

The engine still continues to go well and has a little over 500k's on it now. Ive been working on the tune a little in the response zone around 2000-3500 rpm, still keeping boost below .5 bar. Its a hoot to drive, but now its more responsive Ive encountered the next issue.

At light load around 2000 rpm in 6th the turbo's start to shuffle wildly. As in 1 to 1.6 volts variation between the two maf sensors, and they do this see-saw thing back and fourth. This does not help the tuning process at all!

The problem is less noticable if I start to load the engine up above 2400 rpm. Im hoping that the shuffling is being made worse by the fact that ive got the wastegate actuators set pretty loose at the moment, so im going to re-calibrate and tighten them up to 1.1 bar tomorrow. I suspect i'll have to do the twin turbo pipe modification as well to help control the shuffle, or alternatively invest in the sexy nismo intake piping... time will tell.

Try modifying the twin turbo pipe by putting a divider in there like some of the guys on the forums here and in the UK

http://www.skylinesaustralia.com/forums/Tw...um-t332449.html

http://www.gtr.co.uk/forum/107085-twin-tur...ting-guide.html

[Marko R1]

Try modifying the twin turbo pipe by putting a divider in there like some of the guys on the forums here and in the UK

http://www.skylinesaustralia.com/forums/Tw...um-t332449.html

http://www.gtr.co.uk/forum/107085-twin-tur...ting-guide.html

this works! i did this to my gtr

[GTRNUR]

Try modifying the twin turbo pipe by putting a divider in there like some of the guys on the forums here and in the UK

http://www.skylinesaustralia.com/forums/Tw...um-t332449.html

http://www.gtr.co.uk/forum/107085-twin-tur...ting-guide.html

Thats the plan. I spent a good few hours reading the 10 page "shuffle" thread on gtr.co.uk and came across that guide yesterday. I'll be dropping off a spare pipe to be modded tomorrow morning.

[N1GTR]

Mines doing the same thing, my modified pipe should be arriving tomorrow

[Beer Baron]

Is there room to fit an X-Pipe or a balance pipe for the intake, I have a feeling it would well and truly fix the GTR turbo shuffle.

My soarer runs a single intake pipe and has tiny turbos but I dont get the Choo-Choo train.

So I think that a balance tube after the AFM's would fix the issue.

that's not really the issue. in fact it had nothing to do with it. there are many reasons but surge never happens with small turbos like TT soarers have (plus they are sequential aren't they?). it usually occurs on set-ups with large-ish parrallel twins. it's partly to do with at a particular point the turbos start producing more air than the engine can ingest. hence why it happens at low rpm but high load situations. balance between turbine housing and wheel size and compressor size does it too and tune can affect it too but one thing in a GTR that is not helping it is the front turbos outlet feeds into the rear turbos outlet and right angles. you can do all kinds of stuff to the inlet pipe to the turbos and it probably won't fix it. lengthening the distance between the afms and the turbo inlets will reduce the haywire it plays on the afm voltage a bit but it's not the solution. the soluition is post compressor like the guys suggested. a divider in the standard TT outlet pipe helps as do trust and nismo kits that have very nice Y pipes. sometimes it can even be tuned out.

[GTRNUR]

I was also thinking a twin entry intercooler might do the trick as well as keeping the pipes divided from the compressor housing to the intercooler allows more air velocity to build, and as a result more stable and balanced airflow at the maf sensors. Of course that would I'd lose my stock apeparance engine bay too, not to mention that most of the twin entry cores are designed for drag and not the street and are way too big for my application.

[GTRNUR]

Went for a long drive today. The car continues to go well although driving around the shuffling issue is painful. Just under 600km on the engine now. While driving up the range the oil temps got up to around 95 which is getting pretty hot, water stayed on 75. Back on level ground oil drops back to 90. My components for a complete earls based oil cooling system should hopefully be here before the weekend. 19 row cooler, -10 fittings, etc.

I am loving the torque of the engine. Found a sweet spot that didnt shuffle to be around 2100 rpm in 6th, crusing at 100km/h. 14.7 afr's, 28 degress igniton and 1.00 on the knock gauge. The engine is still pulling a light vacuum at that load too. And lean on it a little and its immediatly into boost, and then mad shuffling . Drove the whole nearby range (now reduce to 60km/h thanks to the tourists crashing), in 4th gear at around 2000 rpm. Hills dont phase it at all. The same car with the stock 2.6 had to drop back to 3rd for the slow corners.

Ive re-set the wastegate opening point on the actuators to 1 bar though I still haven't leaned on it to experience that level of boost yet. I want to sort out the shuffle issue first. Speaking of which I picked up my modified twin turbo pipe today too. They estimated 2 weeks before they could get to do the job, but instead they had it done in 3 days. I swear the fabrication shop that does my alloy work just likes messing with me. I'd be testing it now but tonight is the night that the cops like confiscating imports, so i'll get to find out tomorrow instead.

That is all.

[zebra]

that's not really the issue. in fact it had nothing to do with it. there are many reasons but surge never happens with small turbos like TT soarers have (plus they are sequential aren't they?). it usually occurs on set-ups with large-ish parrallel twins. it's partly to do with at a particular point the turbos start producing more air than the engine can ingest. hence why it happens at low rpm but high load situations. balance between turbine housing and wheel size and compressor size does it too and tune can affect it too but one thing in a GTR that is not helping it is the front turbos outlet feeds into the rear turbos outlet and right angles. you can do all kinds of stuff to the inlet pipe to the turbos and it probably won't fix it. lengthening the distance between the afms and the turbo inlets will reduce the haywire it plays on the afm voltage a bit but it's not the solution. the soluition is post compressor like the guys suggested. a divider in the standard TT outlet pipe helps as do trust and nismo kits that have very nice Y pipes. sometimes it can even be tuned out.

Ahk cool, that clears it up ( the soarer turbos run parrallel btw)

Sounds a bit like a supercharger then....A plumbed back by-pass valve would work pretty well, but most of those are big and bulky.

[N1GTR]

That's funny timing, mine came today aswel!;

Really nice bend inside

Exhaust pipe did aswel, I won't put up all those pics in your thread but you get the idea;

[GTRNUR]

Steve, I'll be interested in hearing how your pipe goes, and how it affects/improves low speed stability, spool up time etc. I recall you telling me that you had your actuators set at 1.1 bar at lift off too. I presume you run some kind of boost controller to crank that up to 1.4 bar. Im interested in knowing how quickly your setup makes boost and at what RPM wastegate boost is achieved without the controller turned off.

Looks like you have enough pipe there to make me a system too. I wouldnt mind a nice 4" system. Being somewhat sick of fabrication though I'll probably just wait for a 4" racepace or some jap titanium system to come up for grabs. I do like sounding legal though.

Edited November 25, 2010 by GTRNUR

[N1GTR]

without the controller turned off.

Sure you don't mean with the ebc turned off?

I havnt ever tried that so I'd only be guessing sorry. Yes I use an ebc, the one I've got is a greddy profec B spec 2. Here's a pic for you although this is with ebc of course so I don't know if it will help you;

The top is 25psi, trails down cause the exhaust is too small. After this weekend that won't be a drama

There's enough there for a couple of them, I'll PM you details. I don't know how often a 4" Racepace system would come up, given that's the best they offer it's not like anyone would be selling one to upgrade to anything else. Heres the muffler;

I'll put a db meter next to it but hopefully its about 94db. Not long to go now, its been a long time coming.

I'm just as keen as you to see the result this has on response and spool etc, I'm happy to change turbos if need be or if I can get away with it on this setup. I'm off to japan on Thursday for NISMO fest and some shopping so I plan to have it all done and dusted by the time I leave. Hopefully I'll find a bigger ARC cooler to replace the one I've got as I have a feeling that could be holding it back

[GTRNUR]

The modified twin turbo pipe has helped the shuffle situation, but it hasnt eliminated it. It no longer shuffles at low speeds like 60km/h in 4th, where teh MAF voltage are generally within 0.2V maximum variation of each other. But in 5th at 80 and 6th at 100 it still gets progressively worse as speed increases while at light load. Still seeing 1+ volts of variation. Im guessing nismo maf sensors with their increased load range and resulting reduced resolution would also help make the shuffle situation less evident.

If I get off the throttle and then stand on it hard and both maf sensor voltages equalise and remain nearly the same as boost builds. So the next thing to try will be a HKS exhaust manifold with a balance pipe. Since they are rare as hens teeth and swapping the manifolds out is a prick of a job though I will probably just switch to MAP sensor based tuning and just ignore the light shuffle issue.

Boost response has improved. 0.4 bar by 3000 and .6-.7 by 3500, where i shift. It doesnt feel like the turbos are fighting eachother anymore. The car used to surge and falter when the shuffle was happening though a big part of that would have been the ecu freaking out about vastly differing maf sensor voltages..

Oil cooler still hasnt arrived yet. On the bright side ive got the aircon gassed up again now, which is desperately needed up here this time of the year.

The top is 25psi, trails down cause the exhaust is too small. After this weekend that won't be a drama

So Steve, does this mean your achieving full boost by 5100 rpm?

Edited November 26, 2010 by GTRNUR

[dysonest]

fark yeah looks the goods

[EWKC]

i am so jealous. i dont have budget to get this. =(

[N1GTR]

The modified twin turbo pipe has helped the shuffle situation, but it hasnt eliminated it. It no longer shuffles at low speeds like 60km/h in 4th, where teh MAF voltage are generally within 0.2V maximum variation of each other. But in 5th at 80 and 6th at 100 it still gets progressively worse as speed increases while at light load. Still seeing 1+ volts of variation. Im guessing nismo maf sensors with their increased load range and resulting reduced resolution would also help make the shuffle situation less evident.

If I get off the throttle and then stand on it hard and both maf sensor voltages equalise and remain nearly the same as boost builds. So the next thing to try will be a HKS exhaust manifold with a balance pipe. Since they are rare as hens teeth and swapping the manifolds out is a prick of a job though I will probably just switch to MAP sensor based tuning and just ignore the light shuffle issue.

Boost response has improved. 0.4 bar by 3000 and .6-.7 by 3500, where i shift. It doesnt feel like the turbos are fighting eachother anymore. The car used to surge and falter when the shuffle was happening though a big part of that would have been the ecu freaking out about vastly differing maf sensor voltages..

Oil cooler still hasnt arrived yet. On the bright side ive got the aircon gassed up again now, which is desperately needed up here this time of the year.

So Steve, does this mean your achieving full boost by 5100 rpm?

Sure does mate. I got your pm I'll reply tomorrow when I've for a chance, today was spent with the car so I have some work to catch up on (yes I'm procrastinating right now )

I think I know where one of those manifolds is located. I'll also keep an eye out next week in japan for one.

What ecu will you switch to?

Also maybe I missed it but what cams are you going to use? On the topic of cams I have 270's, I'm buying some 260's over there to do back to back testing to see if I can bring them on earlier by changing cams. The new exhaust should have an effect on this aswel of course

[GTRNUR]

Ive got an R34 Djetro here that I can use so i'll probably give that a go next week, but I am also considering Vipec. Cams changes are a ways off, but at the most it will end up being 260 poncams or possibly something custom.

[N1GTR]

Great minds-I'm going 260 poncams aswel on the next motor

Just quickly for your shuffle problem, mines got the new pipe on it, the shuffle is reduced greatly but in 4th up a hill starting from 60 using half or more throttle it is still there but nowhere near as loud

[GTRNUR]

Interesting that the pipe mod isnt a cure-all after all then.

Ive been thinking more about why the shuffle is so bad with my setup, and I think it comes down to the extra displacement. The GTRS's are an un-balanced turbo, known for having shuffling issues on everything from 2.6lt upwards.

I think the difference is however that the smaller displacement engines arent producing enough exhaust gas flow to get the turbo anywhere near spooling under light load or even load up a hill in a tall gear. But when you kick back a gear or two and rev from 5-9k, as engines with these turbo's commonly do, both turbos are spooling up evenly as a more or less matched pair with near identical exhaust restriction.

I've discovered that if I load up my engine up in a tall gear I can actually get positive manifold pressure (0.1-0.2 bar) below 2000 rpm. So the the moment the engine loads, up the gas flow is there and ready to start making boost. So on the bright side I have more or less achieved my "like stock" response, there is just the matter of the shuffle to resolve and thats it.

Ive also discovered that if I drive the car in what would be the "normal" rev range that the RB26's drive comfortably in (one gear lower generall), the shuffle problem isnt as evident. Because at a higher RPM in a lower gear the engine is under less load (running in higher vacuum), but when I stand on the throttle, the turbo's skip the shuffle and immediatly jump to 0.5 to 0.7 bar.

Im still driving the car to work every day. Only 300K to go till I can crank a power tune into it so Ive got to make a decision about a map based ecu soon.