jakeoster Posted January 27, 2011 Share Posted January 27, 2011 Alrite guys, as much as I'd like a gt35 on a beautiful full race manifold, I want to be driving my Z sooner rather than much later. I have come across a setup that is affordable and with as little of compromise as my budget will allow. I wanted your thoughts on it before I started making purchases. Keep in mind I don't have thousands to spend so I am making some compromises where I can. The turbo is a Precision 5431, journal bearing and I was considering going .82a/r as I want more top end. It's externally gated with a T3 flange. Precision a reliable unit? The wastegate is a Tial 38mm unit. The manifold is an eBay top mount with a T3 flange and 38mm wastegate flange. Would the cutting of the wastegate downpipe be trivial to clear the steering shaft? What bracing should I do to make it a little more sturdy? Would heat wrapping it be a good idea? Finally; an "Isis" greddy knock off plenum as I've heard they are the "best" knock off available. My future goals are about 400rwhp down the line. Thanks for your thoughts. I wanted to consult you guys before I make any moves as I have the funds available, am back at work after we opened again for the semester, and have paid off all my school fees and books. Quote Link to comment Share on other sites More sharing options...
GTZ Posted January 27, 2011 Share Posted January 27, 2011 Alrite guys, as much as I'd like a gt35 on a beautiful full race manifold, I want to be driving my Z sooner rather than much later. I have come across a setup that is affordable and with as little of compromise as my budget will allow. I wanted your thoughts on it before I started making purchases. Keep in mind I don't have thousands to spend so I am making some compromises where I can. The turbo is a Precision 5431, journal bearing and I was considering going .82a/r as I want more top end. It's externally gated with a T3 flange. Precision a reliable unit? The wastegate is a Tial 38mm unit. The manifold is an eBay top mount with a T3 flange and 38mm wastegate flange. Would the cutting of the wastegate downpipe be trivial to clear the steering shaft? What bracing should I do to make it a little more sturdy? Would heat wrapping it be a good idea? Finally; an "Isis" greddy knock off plenum as I've heard they are the "best" knock off available. My future goals are about 400rwhp down the line. Thanks for your thoughts. I wanted to consult you guys before I make any moves as I have the funds available, am back at work after we opened again for the semester, and have paid off all my school fees and books. precision is a good turbo. If I am not mistaken they use garrett turbo's and modify it. I don't know how much top end you want because if you can I would recommend the .78 a/r twin scroll housing. Fast spooling and great flow without choking topend. I am using the ISIS and have no complains. Clean up some of the castings on the water inlets. If you will be pushing bigger boost I recommend you go bigger than the 38mm wastegate. Good luck Quote Link to comment Share on other sites More sharing options...
jakeoster Posted January 27, 2011 Author Share Posted January 27, 2011 Thanks for the advice; glad to hear precision makes legit stuff. However since this is a smallish turbo wouldn't higher boost not warrant the need for a larger wastegate? In my mind, since higher boost is being run through the turbo, the gate would need to be opened less and less pressure released. I could be way off but I just wanted to clarify. The reason why I'm curious is because I can get a deal with that particular turbo and wastegate together. Thanks. Quote Link to comment Share on other sites More sharing options...
Oddmanout84 Posted January 28, 2011 Share Posted January 28, 2011 I've seen some of those "knock off" ebay top mount manifolds on some guys cars work pretty well. HOWEVER, one of the recurring problems seems to be that (depending on the turbo size), it will sometimes allow the turbine section of the turbo to butt up against the valve cover. Sometimes the clearance issue is serious enough that people have had to grind away a small amount of material from the turbo and the valve cover just to get it to fit. It seems to be a hit or miss thing, but I sure as hell wouldn't want an item that regularly glows cherry red directly against that part of the engine. Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted January 28, 2011 Share Posted January 28, 2011 Thanks for the advice; glad to hear precision makes legit stuff. However since this is a smallish turbo wouldn't higher boost not warrant the need for a larger wastegate? In my mind, since higher boost is being run through the turbo, the gate would need to be opened less and less pressure released. I could be way off but I just wanted to clarify. The reason why I'm curious is because I can get a deal with that particular turbo and wastegate together. Thanks. Keep in mind PSI and Flow are not the same. Your coolant system holds a certain PSI, but it has nothing to do with coolant flow through the system. Its the same principles with slightly different dynamics. Max and Min boost pressure is dictated by flow as there is a max and min flow for the turbo before it cavitates or stalls(I believe those are the correct terms). Flow has a range that is specific to each motor. So when determining turbo sizes and waste gates you can calculate what works with about 5 mins of work and a calculator. The turbo you are looking at is new right? The manufacture should have design specs to help determine what size waste gate to run. If in doubt try out their tech assistance line. You should also be able to get a flow map graph for the setup you want while your at it. Then you can crunch some numbers for your RB and determine how well that turbo will be supported and what flow rate ranges you fall into by plotting your specs at RPM on the compressor flow map and determine what boost pressures are optimal. Takes most of the guess work out. As an added bonus you can dial a turbo size to your motor at a given PSI and keep the flow in the sweet spot... This requires you know what boost pressure you want to run before hand. A tech assistance line should be able to do all this with you on the line if you have your engine specs. You may need to determine your engines "volumetric efficiency" aka "VE". Google that one and see what you can find. I didnt memorize how to figure all this out so some of this info may be a little flawed. I use to have a hot rodding book with a complete break down on the subject. If I ever find it I need to scan it and post it up here for you guys. Its one of the best tools Ive come across for help with turbo decisions. Im sure there are basic programs out there that will help figure this out if you google it... but you need the flow map still so you can plot it. Quote Link to comment Share on other sites More sharing options...
ZT-R Posted January 28, 2011 Share Posted January 28, 2011 and on the 7th day, God created HybridZ.org... i love this place Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 28, 2011 Share Posted January 28, 2011 (edited) To add to what Ray says, don't confuse a turbos hot side a/r with getting 'more power up top' in MOST cases all it does is delay boost onset making for LESS power under the curve. If you have an A/R that is too big or you have messed up sizing it and your slip ratio is off wastegate sizing may be more important...but that's a band-aid to an application problem. If JeffP could run a T3/4 hybrid to 500HP and 7000rpms with zero intake/exhaust delta-p and only use a 0.63A/R housing you might want to reconsider your 'need' for a 0.82 hot side. And that was on an INTERNAL wastegate! All a 0.82 will do is move your boost threshold from 3000 to 3500 or higher (depending on compressor-side mapping) and put the flapper into a less flow conducive angle. You may want to review the progression of Jeff's turbos, as he was making an honest 450RWHP on a stock housing ported to work with a different T3 turbine wheel, and a TO4 Compressor housing. That thing would give him 30psi at 3000rpms and pull well to 7000. And again, that was with the INTERNAL wastegate. If you are worried about too much compressor and want to blow off excess exhaust that is another way to go, but the staging of the wastegate is much tricker. I don't think it's needed. Frankly anything to 400 would likely not need an external at all if you do your sizing right. I think Jeff had some creep problems at the stock 8psi setting, but after that it was fine. Another thing you want to pay attention to at Jeff's site is the actual flowing of the Tial 38mm WG, it's not as great as it should be and their smaller unit actually flows more. It's all on his extreme280ZXT site at anglefire. I think you're going big in the wrong places, and adding complexity you don't really need at that power level. Edited January 28, 2011 by Tony D Quote Link to comment Share on other sites More sharing options...
jakeoster Posted January 28, 2011 Author Share Posted January 28, 2011 Good info Tony and Ray, two more examples of why this forum is head and shoulders above everything else out there. I'm not looking for a small lighting quick high psi turbo as this is going to be a street car mostly. I'm looking to keep the boost pressure down with a larger higher flowing turbo to limit the strain on all my components over the long term and to negate the need for a metal headgasket and resurfacing. I'm looking for some delay in the lower rpms so I'm not in the boost burning fuel and making a lot of noise when unnecessary or while making a quiet pass by a cop haha. Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted January 28, 2011 Share Posted January 28, 2011 (edited) Good info Tony and Ray, two more examples of why this forum is head and shoulders above everything else out there. I'm not looking for a small lighting quick high psi turbo as this is going to be a street car mostly. I'm looking to keep the boost pressure down with a larger higher flowing turbo to limit the strain on all my components over the long term and to negate the need for a metal headgasket and resurfacing. I'm looking for some delay in the lower rpms so I'm not in the boost burning fuel and making a lot of noise when unnecessary or while making a quiet pass by a cop haha. Some number crunching may result in a change of thinking... prepare to change your mind about how you think all about forced induction dynamics... Ive been content with 13psi on the stock turbo this far. Ive squeezed 300 hp and torque to the wheels with the stock turbo and minimal tuning(there is room for improvement). On stock boost with EVERYTHING as it came out of the R33 GTS-T I put down 265RWhp and 233RWtorques which is over crankshaft rated power specs for my RB25det. As you figure out flow you will also be better equipped to design the intercooler and piping systems as well. BTW you will never hear my car coming. We've tested this. All the noise is directed out the back. I dont know what I did right. We made several passes on the freeway and you literally hear nothing until the back of my Z passes you and then it sounds just like some of those RB drag videos you can find on youtube. Inline six/hoover on crack. Very Satisfying. Edited January 28, 2011 by rayaapp2 Quote Link to comment Share on other sites More sharing options...
jakeoster Posted January 29, 2011 Author Share Posted January 29, 2011 Yeah Ray, the stock turbo ain't too shabby. I would be sticking with it right now if mine wasn't blown and my several attempts at sourcing a stock turbo didn't fail, I'm done with that. I've done quite a bit of poking around and a high flowed one etc for the money doesn't really fit my goals, even considered an hks gtrs kit (for a second haha). After the advice you guys provided (thanks again, I'm glad I asked). I'm going to baby it with the blown turbo and save a little longer. And end up with Precisions equivelant to the T04S with a .63 hot side, 46mm Tial gate, mid range manifold with better quality, and the "Isis" plenum. Ohh yea haha, call me a ricer but I want to move foward from my hodge podge looking engine bay with the plumbing all over and what not. I would be lying if I said I didn't want a top mounted snail with the side plenum cleaning things up a bit Great info, I had misinformed myself about a/r sizes and a couple other things you guys cleared up. Thanks again. Quote Link to comment Share on other sites More sharing options...
ZT-R Posted January 29, 2011 Share Posted January 29, 2011 careful cleaning up the plumbing i got a grand easy in fittings alone but im an idiot too... it does look sexy though and can have the motor out in about 15 mins. Quote Link to comment Share on other sites More sharing options...
jakeoster Posted January 30, 2011 Author Share Posted January 30, 2011 Yea the Nickel and diming adds up. Price you have to pay I guess for an attractive engine bay =p Quote Link to comment Share on other sites More sharing options...
jakeoster Posted February 4, 2011 Author Share Posted February 4, 2011 (edited) When you want it done right, you have to do it right the first time. Today I bit the bullet and put in an order for the right way. Built to order, beautiful, well engineered, bulletproof, and couldn't even find China on the map. First piece of the puzzle for my forced induction solution. Ill update when I receive it in the coming weeks. Edited February 4, 2011 by jakeoster Quote Link to comment Share on other sites More sharing options...
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