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Always on the lookout for good bits of writing that I can put up on my own site if I think they might be helpful or interesting to someone, and have found one right here.  The writer is a guy called Chris who’s a good friend and knowledgeable car guy who used to be here in Okinawa.  He’s writing about an Okinawan company called S-Tec Motorsports which is a tuning shop/parts manufacturer here in Okinawa, and in particular the exhaust manifolds they do for the Nissan RB20, RB25 and RB26 engines.  He’s done a great job with a clear unbiased review and anyone with an interest in one of these very competitively priced manifolds should have a read.

There seems to be a lot of questions and opinions about Stec manifolds rolling around out there lately. Some of the stuff said is opinion not really based in fact, and some of it is valid observations. I thought I would do a little write up since I’m constantly repeating the same points in different threads. I don’t want anybody to think I’m trying to sell these for him though. People have just bashed them at times, or expressed interest in them other times. I think it’s a pretty good option, but I’ll try and stick to the facts about them and not “sell” them.

A little background so nobody tries to say I’m being dishonest, S-tec (Scott) built my car and is a friend of mine. He’s an American dude living in Japan which is where his shop is. I used to hang out at the shop about every day, and have even helped stack these up and test fit them with him, so I’m pretty familiar with them and how he checks them. I’ve run both his side mount and top mount manifolds. I’ll try to cover all the good points as well as the stuff that could use some work.

RB20/25/26 Top Mounts

These seem to be the ones people are interested in the most here on NICO. The top mounts are basically a knock off of the HKS/Greddy twin scroll (split pulse) design T4 flanged design. All the piping is made with 321 stainless, which is much better then the 304 stainless most of the Ebay crap out there uses, and it’s all 2.8mm thick. There are also small braces where the primaries meet the flange, not that it needs them. They will never crack. He’ll back that up. If they do, send it back to him and he’ll fix it for you, but he’s never once had that happen. I’ve had mine glowing bright orange (bright enough to read from at night time and light cigarettes of the exhaust housing) more times than I can count and never warped a flange or had it crack. The primaries are pretty will port matched to the head. Not perfect, but not half blocking the port like a lot of the Ebay crap. The can’t really be perfect because the 25 and 26 ports are a little different and it has to fit both.



Also, the primaries go all the way through the flange, so you can really grind the crap out of them and match them up perfect if you want. I did it to mine.

The flanges are 12mm thick laser cut plate stainless, not cast, and everything is welded in a jig, so it’ll be nice and flat which means no exhaust leaks. Scott checks each one with a straight edge and test fits every single manifold against a head before he sends it out. Also, they are flanged and drilled to fit both the 20/25 bolt pattern as well as the 26 bolt pattern, not that that matters to most people (it helps Scott keep the price down), but if you ever step up to a 26, you don’t need to buy a new manifold. It’ll slide right onto the head with out having to wallow out the holes like you have to on some mani’s. There’s one stud that would be a huge pain to get a nut on if it was stock, so you’ll get a shorter exhaust stud to replace it and make it a WHOLE lot easier to get it all bolted up.

The wastegate runners are twin 43mm primaries coming into a 52mm collector, which necks down to a 4 bolt HKS style 50mm flange. As far as clearance of the valve cover goes, I’ve seen TO4r’s, Holset H1E’s w/18cm housings, HX40’s with 16 and 19cm housings, Ebay “Super T70’s”, and even a T88 fit on the stock T4 flange and clear both RB20/25 valve covers as well as 26 valve covers.

Now I’ll talk about some of the issues people have brought up about these. One thing mentioned is the collector looks a little rough on the inside. It is. These are, in fact, made in china in a factory, all be it with much better materials than normal and with much better QC. Scott has actually flown to China and spoken with the dudes at the factory, showed them how he wants things, and paid extra for some of his specifications. He’s also refused to pay them when they screwed up a batch and he basically had a pile of expensive scrap metal which he wouldn’t ship out. These aren’t “one off each time you order it” manifolds like 6boost or full race. Those are $1000-$2000 manifolds and they look like it. The collector on the Stec mani could use some work with a die grinder to smooth it out a bit and remove some excess material.

Here’s the S-tec collector

Here’s a 6boost

Obviously the 6boost looks much better, but I’m not sure how much difference it would make in flow.

Another thing about them is the fact that these probably will have clearance issues with left hand drive vehicles–specifically the wastegate flange will likely hit the steering column depending on the mounts you use. These manifolds are designed for a right hand drive skyline. I’ve seen them in a bunch of RB’d Sylvia’s over in Japan, but again, they are RHD. You’ll almost certainly need to have the wastegate runners chopped and re-welded to clear everything. That segway’s me into another thing…..

The mani is a dual scroll (split pulse) design, but down at the end of the wastegate runners, the two halves of the engine pulses can come together and muddle a bit. How much this hurts is a subject for debate, but when I went to two completely separate wastegate runners and wastegates, it helped my spool times drop by around 200-400rpm in 4th gear. That’s significant. If you are going to chop and re-weld the wastegate runners anyways for fitment, you might want to consider setting it up like this.

One last thing I’ll mention is a problem that I have had, but I’m the only one anybody has heard of this happening to so far. I experienced boost creep on my RB25 with cams and a Holset HX40 with a 19cm housing and a single 50mm wastegate (one of S-tec’s HKS knock-offs). Scott said he thinks it’s because the HX40 with the 19cm housing was just the right balance of flowing enough to make a crap ton of power (and exhaust gas), but not enough to let out all of the exhaust gases, so the boost just kept climbing. Again, nobody else has had this problem. I took the mani off and noticed inside the collector, where the wastegate runners joined the party, it looked like the hole wasn’t as big as the wastegate runner pipe (43mm).
I took the die grinder to the ports and opened them all the way up (as best as I can tell with my precision fingerometer). After we reinstalled it, the creep issue was better, but the boost was still zipping up to 1.5 bar which is the size of the spring I had in there, staying put until around 7k rpm, then creeping up to about 1.8-1.9 bar by 7800rpm. To be clear, if you want to grind on them, you will need something like a die grinder and a stone. A Dremel isn’t going to even make dent in these things. The final solution was to take the mani off again, and re-design the wastegate runners into two completely separated runners with twin 50mm gates. As you might guess, I no longer have boost creep issues LOL. An added benefit was the better spool times.

In conclusion, the Stec manifolds are solid, quality manifolds at a damn good price. They aren’t perfect, and do not have the same level of attention to detail during manufacture as some of the high end $1000+ manifolds but they aren’t meant to compete with them. These are basically the best “budget priced” manifolds you can buy. I always say they are 95% of the high end mani’s for 20% of the price. They fit and they won’t crack, and I’ll stake my “internet cred” (for what that’s worth) on Scott standing behind what he sells 100%.

So, now on to the T3 flanged sidemount manifold.

They are made of the same 321 stainless that the top mount is made out of, but the primaries are a little thicker coming in at 3.0mm thick. Flanges are made to the same standards as the above top mount and also welded in a jig. These put the placement of the turbo in the exact same place as stock. If you can bolt whatever turbo you want up to a stock manifold, it’ll fit on this one too. That means it’s safe for LHD cars right out of the box, unlike the top mount. I ran one of these with my stock turbo and it bolted right up. Again, S-tec test fits each one up to a head and checks the flanges with a straight edge before it goes out. One thing I wish these were is split pulse (dual scroll) manifolds, but most of the smaller framed T3 turbo’s you’d bolt on in the stock position are single scroll anyways (including the stock turbo) so it wouldn’t help there anyways. Also they are already significantly improving how quickly a stock turbo spools, which is already pretty quick, so I don’t think it’s that much of an issue. The primaries aren’t huge, so while it’ll outflow a stock manifold significantly, if you are chasing big HP numbers (like 500hp+) you might want to look at something else.

The one I had was heat wrapped for about 2 years and never cracked. I was running it in combination with one of S-tec’s “turbo elbow’s” and put a bunch of other things on my car at the same time, so I can’t really say how much just the manifold added. I have spoken with a lot of friends who added the manifold last on an already completely opened up exhaust from the turbo back, and they said the difference was noticeable.

One quick story I thought was pretty cool and showed how resilient these things are. S-tec had some Japanese drop his R32 GTSt off at the shop and say he was leaking tranny fluid all over the road every time he got up to speed and couldn’t figure out why. Scott put it up on the lift and started looking for a leak and couldn’t find one, although the entire underside of the car was covered in tranny fluid. I suggested looking at the fluid level, and when he did, the problem was obvious. Old dude had fill his tranny to the top of the shifter hole with tranny fluid LOL. Scott drained it, put the proper amount in, and put it up in the air on the lift with a poll on the gas in 5th gear and let it run for 5 minutes to make sure it didn’t leak any more. After that was done and he was lowering the car, we saw this……….

Stock tune = to little timing and really high exhaust temps. Keep in mind that picture was taking during the day in a well lit shop. I’ve had mine glowing like that before too after a couple of back to back sets on a twisty road we call Takoyama. Anyways, that manifold is still on the same car to this day with no cracks or leaks or anything like that. They just won’t crack. It’s scary to think of what mine looked like under all that heat wrap when I had my sidemount on there and was beating on it. Must have damn near been white hot!