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Very interesting then.....must be a combination of things, mainly cams being the difference, but same turbo, I made [email protected], same dyno.


I'm sure it drives absolutely fine, just seems a little low to me.


Wouldn't think an exhaust manifold + cams would give an extra 55hp....

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Yeah, I thought it was a bit odd because it was only 10hp more than a mates with a 2871 at 16psi.


This engine has always been laggy, even with the t25 and t28 on there so it's pretty flogged out, current plans are to get another sr and rebuild it on the side anyway. I can deal with the lag for daily duties in the mean time though, gate keeps my mind off it.


Thanks for that though, I did have my suspicions.

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Fracking silvia's.


Knowing that this engine isn't performing at its full potential is irritating, it's like a little voice in the back of my head, constantly taunting. I really want to get it going good again with full compression on all cylinders and #1 spark plug not bathed in oil. I'm torn between getting an engine on the side to rebuild or getting a cheap run around and fixing this one.


I'm leaning towards rebuilding this one because I'd rather fix something and have fun knowing that I brought it back to life and kept it going rather than just buying a new one to replace it. New pistons, rings, HG and bearings aren't exactly expensive through Nissan and Taarks, but I have a tendency to get carried away (this was originally going to be s15 t28, 550's and a nistune) and I've already stopped myself from working out a saving strategy for the Tomei block on FRSport. Shh, don't tell the missus haha.


In saying that, I also like the idea of a second engine so that if something does happen to go wrong I haven't just killed the daily. Resulting in it not being so much of a daily and snowballing into a very expensive, albeit pretty, driveway ornament for months on end.


I don't know, that's a quick look at both sides of the argument, any opinions?

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What are you using for a boost controller?


Is the oil you found on the top part of the spark plug or below it inside the cylinder?


Trev makes more hp with the same turbo and boost because his comp ratio is higher with 9:1 pistons, a decked block and head. All of these things raise compression. That means if you run 18psi and he runs 18psi his cylinder pressure is higher than yours so it has the potential to make more hp.


If you look at this chart http://www.ztechz.net/id1.html and find your turbo vs your friends gt2871 you can see your comp wheels are almost the same size but your turbine wheel is significantly larger. That means yours has the potential to make much more hp than the 2871 but it also makes it laggier because the bigger wheel is physically heavier so it takes longer to get it spinning.

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For the boost control I'm using a new greddy profec and a tial mvr. Before I had it, it was using a turbo smart boost tee and, as most manual boost controllers, it liked to spike very now and again.


The oil is on the combustion end of the plug, in the cylinder.


Didn't realise Trev had 9:1 forgies, makes a bit of difference haha. I expected the td06 to be laggy because of the turbine and housing difference, hence why I went external wastegate, but just hitting full boost at 5500 seemed a bit over the top to me.

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No, nor a leak down test. In the process of finding gauges and equipment for them though.


When I was hand cranking to TDC for the cams you could hear it gargling through oil and hissing on compression.


EDIT: More so than the usual air/pressure leaving the cylinder, I've done another set of cams since then.

Edited by DonkeyKong
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  • 4 months later...

A sad update, I haven't done a whole lot with it recently.


A couple of weeks back I ended up doing a warm compression test which read 120,115,115,110 and now it wont even fire up. Figured it was finally time to get that rebuild started so I went out and bought a charade to get me around while the sil played driveway ornament. Then began hunting for a fresh engine to be my base, my mate had offered his old sr as he was going rb, did the compression test 150,150,150,150. Fracking beautiful I thought, then it turns out his rb was a dud so that didn't happen.


Enter spirited charade drive of heat, I was just taking a casual drive through the canning dam/ McNess area when it decided to rage quit in the heat and throw up it cooling fluids just as I got onto canning rd, I limped it to kalamunda where I parked it up, got a double extra shot large cappuccino and made a little bit of a spur of the moment decision. I walked from Dome to Kalamunda Toyota, within half an hour I drove a pegasus white 86 gts off the showroom floor.


This is where I sit at the moment, over heating charade, a silvia that won't even crank over and a new 86.

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  • 8 months later...

Not too sure mate, I sold it to a guy who went through his plans with me, had good intentions but I haven't seen it around since.


Ground up, monster rebuild? Fingers crossed haha

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  • 5 years later...
  • 1 year later...

Annual update. 

The RB25 sileighty is still in pieces BUT is somewhat more complete than last time.

Now maybe also have an s13, the red one from the start of the thread.  The first s-chassis I ever owned, now rebuilt and resprayed in seafoam. 

Until next year when I post in the empty forums, peace my dweebs 🖖

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