RB26DETT into 240Z Beginner Progress

[getoffmyinternet]

if u can cut a 3 inch pipe down the middle, weld on some 2 inch or so wide plates at the edges on both sides, you can then extend it to about 5 inches in diameter. then you can Y-weld a collector of two 3 inch pipes with a smooth transition (cause the strip you welded in the middle of the two 3 inch halves can be tapered to allow a widening or narrowing of the "short plenum" as i'll call it.)

 

That's a very interesting idea. It might also be easier in the long run. The good news is I already have a bunch of 3" tube. Making a true Y collector could prove to be too challenging for me, so I figure the easiest alternative is to make a triangle plate to angle out the two halves into a vault a little more than twice the original height with a flat plate closing the end and two individual tubes coming straight off of it. Actually, I could probably then taper the edges of the tubes before welding them on to angle the exits a little in favor of the direction to the mafs. I have to make sure there's enough vertical space for the two tubes to be directly on top of each other though. I would probably buy all the hoses and fittings that won't weld together, assemble it towards the center, and then figure out exactly how short this collector is to be made etc. Hell if I can figure out how to make a standard y union work it would be worth the money. It's just that they always split at 120 degrees and it would be a pretty tight fit that way. The ideal type would be more like a dual exhaust union flipped around... We'll see.

 

I drew up what I'm talking about to clarify, but my scanner doesn't want to work today!

[Careless]

yeah thats basically what i was getting at. its good that my typing got across, sometimes i read it and it doesn't make much sense. LOL

[getoffmyinternet]

Okay, so how about a hommade box for the intake? A 6x10x4" enclosure of sorts featuring a panel type filter and a duct out the front scooping air from the holes in the radiator wall. The mafs bolt right on to the back of it plumbed with a few hoses to their respective turbo inlets. The box would be relatively easy to make out of sheet aluminum and a lip on the inside under the screw on face to seal the filter down when it's closed.

 

To clean the filter I would have to unbolt the mafs and slip out the ic pipe, but it's not that big of a deal. I actually thought of incorporating a vacuum meter gauge on the back so I could see how the filter is doing. Wouldn't that be neat?

 

A 6x10 filter would be good enough airflow right? I'm sure the oem filter was a little larger but they always have crazy ducting rather than pointing straight forward, and are the cheap paper type--supposedly washable k&n filters do twice the flow rate as the disposable type.

 

Eh?

[getoffmyinternet]

Okay it's kinda late at night, so give me a break if I'm having a brain fart here, but I don't see the what kind of cfm ratings the stock engine intake has or should have.

 

Is it correct to take the displacement of the engine and multiply it by half of the redline to get the total (N/A) air displacement rate? If this is the case, 2.6L is equivalent to 367cfm@8000rpm. Something then has to be added for the turbos though because the mass air is going to be higher since it is above ambient (intake) pressure. Although, that would mean if you're boosting 15psi, your intake cfm is actually double that number. For stock (which I think is 7psi boost?), that would be 542cfm at the intake.

 

Who knows the actual number? My design calls for a 6X10 K&N filter, which looks like it's 450cfm-ish. The k&n website doesn't say what the ratings are, but I've comparing filters by looking at how much oil it says to use on them. Based on this the round cone filters seem to be better in general than the panel ones.

[Careless]

More like 220 untouched and 280cfm with some work from what I've read on various sites.

 

Not sure at what lift, but...

[getoffmyinternet]

So basically my curious hypothetical correlation between displacement and cfm is pretty debunked. Well that's good. I was skeptic when I saw such a high number. I mean it's an l6 not like a 440+6...

 

Well the panel filter should be able to easily support that much air, if I can make up my mind. Me fasha suggested building a rail inside the box and instead of making the face come off, give it a narrow lid and slide the filter down from the top so that when it needs a cleaning, nothing but the ic tube has to be removed. I made a "box" out of scrap styrofoam to my liking and we'll attempt to fab it to that shape once it looks like it will fit right.

[getoffmyinternet]

I haven't been around in a while so just a quick pathetic update. I drew up the plans for my air cleaner box off the styrofoam model I carved up using the 6x10 filter I ordered. It was $45 but I got 10% off and a $15 rebate. Just waiting for my dad to get the free time to tig it.

 

Other than that, I have pictures, but there's not much to see, I connected all the fuel lines finishing that part up. The radiator is finally connected but I still need to get a new overflow box (smaller--the one I had was already a generic replacement) and find a spot to mount it. I might do that tomorrow. The intercooler is disconnected one last time for the placement of the air box. It will pretty much go right in smoothly (I think) with a few more silicone hoses which I'll order after double checking with a fitting of the real box once it's made.

 

Also my dad is going to seal up a 6" aluminum tube to make the vacuum bottle for the brake booster. I'm really saving some money on all this welding of scrap pieces. Plus it will all look pretty nice together anyway, so I'm happy with the progress, just not the speed at which it is going. I want my car back! I'm already planning all my interior work with the money I made fixing another car, plus that little tax break, and a website I'm working on. It's going to look niiiiiiice! Eventually.

 

Cheers!

[Careless]

[getoffmyinternet]

I have pictres, too many, they probably explain themselves. Some of it has been discussed previously but I didn't have time to add pictures until now. I'll rant more in the final writeup.

 

[Bishopsrock]

I have just put my car together different to you and might be missing something?

 

 

Please can you tell us what the brass pipe coming out of the bung connects to and what its purpose is??? as I don't have one - yet?

 

Cheers

[Careless]

probably for a boost guage.

 

one heck of a fitting though.

 

Could be to test for pressure in the system, but it's not a petcock, so I don't see it being closed at all without something on the end.

[getoffmyinternet]

I have just put my car together different to you and might be missing something?

 

 

Please can you tell us what the brass pipe coming out of the bung connects to and what its purpose is??? as I don't have one - yet?

 

Cheers

 

 

It's kinda hard to tell from these pictures but when installed that fitting connects to a vacuum line rail that wraps around the back of the engine.

 

 

That particular vacuum sensing line is one of two lines connected to the turbo pressure regulator, which is labeled PCM Valve. The valve itself seems to have evaded the camera in all my pictures so far, but I can take one of it tomorrow if need be.

 

 

Originally, I believe there was likely a plastic or rubber hose that went where the plug now goes which bridged the intake lines between the two turbos. (If you saw my modification of the front turbo inlet into a straight pipe, the original inlet pointed off to the side and out of the top was a port about the size of this aluminum plug where the other end of that hose connected as far as I can tell from the engine vacuum diagrams.) Somewhere on that hose was an outlet to this vacuum line. For some reason I only got a piece of the hose and insulation foam with the engine where it was cut and have yet to see anyone else's pictures with it still intact, most likely because they go with aftermarket intakes altogether or at least an aftermarket boost controller that makes this line obsolete. I figured at least for now it would suffice to have the line go into one turbo and assume both are operating at roughly the same capacity.

 

If anyone has any insight into the matter, chime in! Are there any skyline owners in the forum?

[stony]

I'm pretty sure that is where the stock blowoff routes back into... let me do some looking

[stony]

OK found it in the R32 GTR FSM. That particular hole is where the blowoffs route back to and is not a source for vacuum. If I'm not mistaken you want to pull any vacuum signals from up in the intake manifold not the turbo intake.

[getoffmyinternet]

Oh, I wasn't sure which way the line flowed, I just new it led to the turbo controller. I took a guess and figured it used venturi to get a live relation between how much the turbos were taking in versus how much they were putting out. My chart looked like it said "vacuum sensing line" but it could have been overlapped because all I was looking at was the overhead view of the engine.

 

So that Y shaped hose in the center there leads to the front of the front turbo and the hole in the air hose of the rear collector? Then the hose I have going to the turbo controller comes off the needlepoint on that tiny hose just above center in your picture?

 

One question about the recirculation system though. Does having a recirculation valve mean that the wastegates don't unload the turbos completely and subsequently there has to be a blow of system downstream to dump excess pressure? I was under the impression that I wouldn't need an inline bov until I increased the boost or went to aftermarket turbos. I'm still very new to the concept...

[JSpecGC8]

I am a little confused here but I will chime in a little......

 

Recirculation of the BoV into the intake piping is because of Enviro issues, the excess pressure is vented back into the intake stream which is already calculated for from the ECU to prevent any back pressure being forced on the turbo.

 

BoVs are to help your turbo out really, at mid lvl tuning the stockers run just fine, most people want them because of the supposed cool sound they make.

 

Your right in the fact you really don't need one till you start pushing the envelope because most JDM manufactured BoVs are good for upwards of 400ps.

 

The only problem that might happen with an RB and I have not seen it much is a lean condition becomes present when an atmospheric BoV is introduced. Again this is not so much an RB problem as it is a EJ2X problem.

 

Good luck with your project

[getoffmyinternet]

I figured the recirculation system should be just for emissions. I've never dealt with them before. It was the funny wording and vacuum diagrams in the engine manual that got me. My main curiosity was if what I speculated was true--like you said the ecu must calculate for this recirculation, otherwise the mas airflow count would be off.

 

Do you mean however that a bov creates a rich condition rather? Since the ecu thinks there is more air going in than there actually is and schedules too much fuel. This would explain why it would be better to have the bov recirculate to the intake. Might it also be why people get map sensors instead of maf?

 

I did more reading on bov's, which proves difficult because everyone uses the term loosely and interchangeably, but I saw that the main reason is to prevent compressor surge on the turbo, and recirculating the air should be the best way to do that. Plus it keeps the ecu more on point with the maf sensors. Also, I HATE turbo chatter! And bov hoots are disgusting in my opinion. In this light, I don't see how the wastegate could prevent a stall, it seems that they are for different purposes. I'm just thinking out loud here, I seem to have been misinformed about people installing a bov in accordance with a fixed wastegate. Still, most of the things people call bov's that I see look more like plain old dump valves.

[Bishopsrock]

I'm just doing this now and also need to make the decision. Currently my turbos vent back through the MAFs. The way i'm driving that won't last long!

 

Below is a pic of the stock setup:-

 

 

I know I could vent a BOV directly into the existing intake 'Y' shaped pipe.

 

But - I wonder why Nissan chose to take the vent from the injector side of the intercooler when then could have vented at the turbo side and had a much shorter run of pipe directly into the intake???

 

I'm off the Glastonbury Festival now so won't be around to respond to anything till monday now.

 

Cheers

[Daeron]

God, I hope I don't muddy the waters here.

 

I've learned a good deal about BOV vs Bypass valves, and how they work in tandem with the wastegate, in recent months, and cleared up a few misconceptions *I* had had, that it appears may be affecting you as well. SO, I will go ahead and try to explain since I feel like your mis-understanding is similar to what I had held... I hate talking about a subject I understand only abstractly like this (no real turbo exp. to speak of here) but here it goes.

 

The short version is, your wastegate allows exhaust gasses to bypass the impeller wheel. When the wastegate opens up, the turbo loses the force spinning it and generates less pressure. The Bypass valve (whether it is a recirculating type or a blow-off type) eliminates excess pressure on the charge side that has already BEEN built up by the compressor wheel. The wastegate is step 1, and then the bypass valve is step two.

 

Bishopsrock, I am not entirely certain why the stock routing is the way it is... but it appears to me, from the diagram, that the "pick-up" for the BPV air circuit actually comes off the piping nearer to the manifold inlet, then gets routed down there to those two bypass valves mounted on that Y shaped pipe you picture. It gets popped off by one or both valves, then runs out into that Y-pipe, into the tube crossing underneath the IC, and thence back into the turbos, if I am not mistaken. In other words, the air actually moves down thru some tubes, from near your manifold inlet somewhere (look at the diagram, i've never seen a skyline) down to the two BPVs, then into the Y.. the intercooler is only involved b/c the air has in fact already gone thru it. I suspect that they did it the way they did to vent cooled air, straight back into the outlet of the turbo where the air is hottest, rather than venting warmer air there. Plus, proximity to the throttle plate in the point where your blow-off occurs, is good, when you are trying to eliminate the pressure hammer caused by closing the throttle abruptly after accelrating on boost.

 

Where are you recirculating to? you said "vent back into the MAF," by that you don't mean anywhere in front of the hotwire in the MAF, do you?? If so, then that air is being metered, then dumped to before the meter, and then being metered again.. essentially, the same situation as if the bypass valve was an atmospheric blow-off valve.

[getoffmyinternet]

Andy: Why is your current setup venting upstream of the mafs? That seems kind of strange, I don't know if generating a lot of heat around the mafs is an issue or not. But like Daeron said, every time you close the throttle, the ecu is probably going to get confused because the excess air is still counted and in turn will run the engine rich until it is rescheduled on the lean side. And true, venting upstream of the intercooler would make it run through the turbo twice without being cooled and thus generate more heat, while running the air through the intercooler twice will only help cool it more. Although I'm not sure how little air we're really talking about here--it's probably almost a moot point. Still, you'd probably be better off venting to atmospheric than into the mafs. The recirculation system is designed for emissions regulations and to keep the air count accurate.

 

Daeron: So basically I need both then? Again, I always thought bov's were to regulate pressure consistently, like if you had a fixed wastegate. But then I thought that would be wasteful because you're still spooling the turbo when you don't need to. However, it wouldn't be all that bad because if the pressure is dumped then the turbo isn't really under any load. Nevertheless... Anyway, the recirculation valve is just like a non-atmospheric bov, only not spelled the same? I don't want to wear out my turbos or anything by surging every time I release the throttle! My r32 doesn't have the ball bearing or the steel turbine, so I'd basically be screwed.