Taking a rb25 to the limits of the stock engine

by

S-tec Motorsports

Going fast for cheap RB25det

How to make Japanese small displacement engines powerful cheaply. This article will be about the rb25. There is many ways to make this engine fast. It is strong and reliable. We abuse ours daily with no problems. By abuse I mean drag racing, drifting, any other ways we can think of torturing them. Since the rise and fall, of most of the aftermarket Japanese makers, from NISMO to Trust. Many overseas manufactures have learned how to make many of the parts that the Japanese makers claimed were their own. The Chinese are now making most of their parts, along with pretty much everything else in the world. This brought out a lot of direct from manufacture businesses. People started selling stuff for beyond cheap prices on EBAY. Some of this is junk, some of it is from the same manufacture as trust and companies alike.

On to how to make this engine fast cheaply, the RB25 in stock form has around 250 ponies, the block can take above 700hp, the pistons above 600, and even the stock head gasket above 500. So lets get to where the head gasket will not break and stop then. Well you need gas, and a Walboro can deliver. Get you a 255hp pump, be careful though there are Chinese copies out there that will not last longer than a day. They can be had for about 100$. Need something to control all this fuel, a fuel pressure regulator. I dont know if I would trust the copied ones on ebay, I would actually fork out the 70$ for a decent one. You will need an airflow meter from a twin turbo 300zx they can be used or new, long as it works. A intercooler, for 500hp you should really use a 100mm normal or a higher end cross flow, but since we are cheap, a 300$ kit from ebay is where it is at. Most of them are made in the same manufacture in China, this happens to be the same manufacture as Trust for all you name brand gurus. Your going need something to spray the gas, this and the clutch is where most of your money will be going. I buy good injectors, the ones off EBAY, if they do work they dont work well. I prefer tomei injectors for the rb25, Nippon Denso. 555 or 740s take your pick they both will support this much power. Get a good clutch period. Twin plates work well and dont have so much clamping force they break everything. A single, I dont care what your friend said, is not going to hold 500hp for long at all. A good clutch will put you back about a grand.

On to the turbo setup, there are a lot of choices out there, but let’s go with the biggest bang for the buck. One word HOLSET, these are great turbos available at crack head prices. A h1e or a hx40, with between a 18-21cm exhaust will get you there. Manifold, well just look here at the link below 400$ you have an exhaust manifold that wont crack. It can support almost any t4 turbo, and even has a flange for a very affordable wastegate. A 50mm wastegate is also needed, he sells them on his site or just pick one up off of ebay. I have found no decent rb25 manifolds on ebay, there are many people producing them in the states, but the price my god it is high.

Find you a POWER FC, they are getting hard to find I know, but you can still run across them for about 5-700$ Now that you have all your stuff, there is a lot of information on the internet on how to put this stuff together mostly yourself. If youre going cheap, which we are on this one, get as far as you can with it and then take it to your local friendly wielder, if he isnt your friend you need to make him one. You need piping made, a lot of it, exhaust, and intercooler to hook up to the turbo hanging off your new manifold. There are some bits and pieces that you will still need, oil hoses and such, this all can be had on ebay for cheap.

So now you got everything in, the car runs horribly because you have no idea what youre doing with the power fc. Take it some where that does know what they are doing with it, and get it tuned. This is the most important part of the whole thing. RB25 engines do not like knocking at all, their pistons are not designed to take it. They will melt easily, but dont break easily. You should be able to run about 1.5 bar of boost on either of those turbos with out hurting them or the motor. Run decent gas you need about 97 octane to support those compression figures.

You will notice I did not mention changing cams, head gasket, pistons, rod, or anything else people tell you that you have to change, because simply you dont at this power level. Even if you did without extensive port work, the head can only flow about 650hp, and then it gets stuck.

I would stay away from most ebay turbos for now, although I have used some of them with success. Mainly the t70 from xs power. It worked fine after locktiting the compressor nut on. I have seen the to4r copy that is sold on ebay. One word for that, that word would be junk. Holsets can be found for 120-800 all depends what you’re looking for. They spool up a lot better than most garrets I have seen or used.

Scott is the owner of S-tec Motorsports in okinawa Japan. He has been in motorsports for 20 years.

Article Source:

Taking a rb25 to the limits of the stock engine}