Category Archives: Tips

Understanding Torque Specs

It’s important to understand that when working with moving parts, the amount of force in which you tighten a screw or bolt is important. The parts you are attaching are designed by an engineer to stay together when tightened to a specific measurement, commonly referred to in the US as foot pounds of torque (ft-lb). These readings can also be performed in Newton meters (n-m) and kilograms per meters (kg-m). If you open a factory service manual (FSM) you will see an exploded diagram of various parts of an engine, and where the bolts are referenced you will typically see a small range of numbers. These numbers indicate the tolerance range that you should follow when tightening you bolt.

The easiest way to ensure a proper torque reading is with a torque wrench. There are a few different types, but I like the break-away style. They look like socket wrenches, but the handle will turn to set the preferred torque and then when you exceed that limit the head will click, indicating you have reached the limit and to stop tightening.

If you do not follow proper torque specifications, there is a good chance your engine, suspension, wheels, or other moving parts of your car can come apart causing serious damage or injury. So when working with an engine, don’t tighten it by feel or until you can’t turn it any more. Over-tightening can be just as bad as under-tightening.  Follow the specs!

I am attaching a PDF showing some diagrams from the RB25DET head for your reference.

RB25DET Head

Seasonal Change

When the season changes I find myself not driving the 240sx quite as frequently. Tonight I was adjusting my ride height (and somehow my driver side rear was quite a bit lower than the passenger side). When I was finished I re-torqued all of my wheels (a good practice when the weather changes) and checked my tire pressures. The pressure on my Nitto NT01 had dropped down to 20psi. Don’t just check these things on track days. You should be checking them fairly regularly, and at the very least check everything over when the weather starts to change.

The weather had changed enough around here that my IC piping actually got a bit loose and I blew a coupler off when driving on the highway this week. So it’s probably a good idea to check anything that can contract or expand with weather change. If you plan on parking your car over winter and not driving it, you may consider a fuel stabilizer to prevent start-up issues in the Spring.

Remember, if you’re like me and you have performance or track tires that are not all season, be careful driving them when the temperature is near freezing. They will not get enough heat in them to grip the road and you could find your project car in a ditch quicker than you know it. Be safe!

Calculating your actual gas mileage

One of the more common questions people ask when doing an engine swap or upgrading your turbo is “What kind of gas mileage do you get?”

Well, this answer is going to depending on a few things:

  1. How is the engine tuned? If you’re running pig rich then you’re going to get terrible gas mileage.
  2. How do you drive? If you’re constantly mashing the gas pedal and generating a lot of boost then you’re going to get terrible gas mileage.
  3. Are the fundamentals of your car set up properly (i.e. are your tires inflated to the correct psi?).

All of these things will contribute to your gas mileage. My recommendation is to do a controlled test that incorporates your typical driving habits so you can get a real, true answer as to how much gas mileage you’re getting.

This test is so ridiculously easy!

  1. On your next fill-up at the pump, reset your trip counter to zero. This test assumes that your trip counter is in working condition.
  2. Put a full tank of gas in the car.
  3. Drive your car as you normally would until you’re ready to fill up again.
  4. At your next fill-up, write down (or take a picture) of your trip counter and the number of gallons of gas you put into the car.
  5. Divide the trip counter by the gallons (use decimal points for accuracy).

The result is your actual miles per gallon.

Trip Counter
Gas Pump

Using my example above, I would take 230.1 / 13.699 = 16.796 miles per gallon.

My driving habits included a lot of rapid accelerating, some downtown driving, some highway driving. My AFR is typically 15 at cruising speeds to help. This low mpg is likely due to my own driving habits. When the weather is nice I drive the 240sx for fun, not for gas mileage.

Do this test yourself and see what kind of mileage you’re actually getting. You might be surprised.

*** EDIT ***

I did a more thorough test without hammering down and here are the results for casual driving: 17.9 mpg City and 22.1 mpg Highway. It’s not bad as long as you aren’t getting into the boost a lot.



How to Tighten Nut on Camber Plates

When I was installing the KW V3 coilovers on the S14 240sx, I ran into a couple of minor roadblocks. The purpose of this post is to help other DIY folks out there avoid this problem.

  1. The KW V3 coilovers do not come with camber plates. They assume you will either provide your own or use the factory mounts. My factory mounts were long gone since I already had coilovers.
  2. Not all camber plates for an S14 are going to be the same. The inner diameter of the coilover shaft is different from a KW V3 when compared to a K-Sport, for example.
  3. Removing and installing camber plate nuts is not an easy task if you don’t know how it’s properly done.

So I removed the K-Sport coilovers (that was pretty easy because I had this handy write-up showing me step-by-step instructions), but then I realized I had no mounts or camber plates for the KW V3. Tangent – This was a nice time to do a brake pad swap, so I installed a new set of Hawk HP+ pads while the wheels were off. Ok, so the logical thing to do was try the K-Sport camber plates. Unfortunately, the front did not match up but the rear mounts did. Not all are created equal, remember? I came across a set of used front mounts that did the trick, but they had no camber adjustment. So I bought a set of DC camber plates that were supposed to be for factory struts, but those did not fit either. Grrrr….

Tein to the rescue. The Tein camber plates and mounting plates for the rear ARE designed to work with factory equipment. They look great, are easy to install, and are relatively affordable. If you are spending the money on a set of KW V3, you might as well get a proper camber adjustment.

That leads me to the tricky part – removing and installing the camber plate nuts that hold them to the coilovers.

DO NOT USE AN IMPACT WRENCH. You stand a good chance of spinning the piston in the damper, and this will potentially ruin the internals of your suspension. If you want a quick way to test, you can try to compress and expand your damper with the adjustments (compression and rebound) full open or closed. If you feel the difference (i.e. it’s harder to expand or compress when you make that adjustment), then the coilover is probably still ok. This is not a scientific approach, but it’s better to make sure you didn’t ruin them before you put them back on the car if you did use an impact wrench.

The proper way to do this is using a hex key and a box wrench for some setups. Other setups require like an 8mm socket and a box wrench. The Tein were a little different, but the same general concept worked.

This picture below illustrates how the hex key is used to stabilize the shaft while you use the box wrench to tighten the nut. If you don’t stabilize the shaft then it will spin freely (not good). Some people have used a strap wrench to hold the shaft. This did not work well for me because it slipped. I tried a strap wrench with a vice grip over the strap for protection and that had some success. The trick is to not damage, scar, or scratch the piston shaft of the coilover. If you have to grab it for whatever reason, do it at the top. Never grab it with anything towards the bottom or you will ruin your coilover.

Notice how the hex key we use in this scenario is different than the smaller hex key K-Sport provides to change the compression. The hole is larger in diameter for the larger key to hold the shaft, but it doesn’t extend deep enough into the internals. You don’t want to use that or you’ll damage your compression adjustment capabilities.

Now the KW V3 coilovers are different. You don’t have the hex key ability. You have to use a box wrench and an 8mm socket on the outside of the top. The tricky part is that some of the mounting brackets and/or camber plates are recessed, meaning that you can’t easily get a box wrench down in there to adjust the nut once you have it installed. I didn’t have a tool that would allow me to do this so I used a trick. I took a deep socket and I pushed an extension for the small 8mm socket through it. I grabbed the deep socket for the larger nut with some vice grips really tight. I then was able to tighten it down pretty easily.

Check your instructions for torque settings on this nut. It varies from manufacturer, but the KW were around 26lbs of torque (i.e. not very much). You don’t want them rattling loose, but you don’t tighten these like you do the rest of your suspension.

I hope this helps. The whole process is fairly easy. It took me a little bit longer my first time, but swapping the suspension on an S14 240sx is at most a 2hr job for me now (without a lift).

p.s. Once you do a suspension adjustment like this, you’ll want to make sure that you get a proper alignment. Anytime you change the ride height it’s a good idea to do that.

What’s an Oil Catch Can?

So now that you have a performance motor you’re hearing about Oil Catch Cans and probably wondering what this is all about? Or maybe you know what they are but you’re not sure how to hook it up? No worries. This is a pretty common question and an easy one to answer.

On a car straight from the factory, they tend to re-route a lot of plumbing for environmental purposes, but this is not always the most efficient thing for the performance of your car. One of the things they reroute is the breather hose from your crank case. Inside the engine gases and sometimes a little oil will blow past a piston into the head of the engine. If this was not ventilated in some fashion, there would be a lot of pressure with nowhere to go. That’s not good. The factory solution routes these hoses using a one-way check valve back into the intake of your engine. So you’re feeding dirty, warmer air back into the engine. To make matters worse, there could be some oil residue in there and that’s going to gunk up things.

The aftermarket solution is to route those breather hoses to a catch can. The can itself can then be routed back into the intake, to atmosphere, or to your exhaust pipe to be sucked out. In a perfect world, you want some vacuum on the breather hoses to pull air and oil blowby out of the crankcase. So if you use a catch can and re-route it to the intake or to the exhaust then you achieve this result. However, it’s completely fine to just run both breather hoses to a catch can and then put a little air filter on the catch can and vent to atmosphere.

Oh, and in case you didn’t figure it out yet – the catch can accumulates the oil so that it doesn’t go back into the intake.

So here is the catch (no pun intended), you want to make sure that if you do re-route the catch can in some fashion that you are using one way check valves and that your catch can is baffled so that oil doesn’t go out once it has gone in. And remember, you’ll need to periodically empty the catch can. Once a month is usually about right for most builds, and it won’t be full.

Simple Catch Can
Nylon Braided Breather Hoses

Track Days

If you really want to have fun in your car once your swap is completed, you need to do some track events. There are four types of events (that I’m aware of) for you to participate in:

  1. Autocross
  2. HPDE (High Performance Drivers Education) Track Days
  3. Drag Racing (at the track, not on public roads!)
  4. Drift Events

I’ve actually yet to do a proper drag racing event or a drift event, but I’ve done 3 years of autocross and HPDE events. I recommend starting with autox to get a good idea of how your car handles with the new power and balance. Then once you are comfortable you absolutely need to do an HPDE event. This was the most fun I’ve ever had with my car. My theory is, learn to handle your car, then handle it under speed. Now when you feel confident in your driving ability go do a drag event. That’s my plan at least. This way, if your car gets loose on the drag strip you have a better chance of bringing it under control instead of crashing into the walls.

If you haven’t checked out this site, go do it now. It will tell you about most of the track events in your area.

Trying to hit the Apexes at Putnam Park

The Right Turbo

Most of the manufacturers producing turbos do a pretty good job. Your choice of turbo should not be decided based on one manufacturer over another just because you like their brand or the name better. What really matters is which turbo is best suited for your engine. I’ll give you an example. When I first built my RB25DET I was using a Bullseye Power (Borg Warner) S362 Turbo with a .85 a/r. This same turbo was producing 650hp on a Toyota Supra, but it was maybe hitting 400hp on a good day. When the turbo seals blew I went with a .70 a/r and had a bit better spool but still only about 421hp. So I started looking at compressor maps a little more closely and with a little help from a friend and some additional reading I determined that a smaller turbo like a GTX3076R by Garrett would be better matched with the RB25DET engine based on the math. Sure enough, the planning paid off because I hit 534hp with a SMALLER turbo that was spooling quicker.

So the key here is that a bigger turbo does not always automatically mean more power. Yes, if I would have continued to push the limits of my Bullseye Power turbo with race fuel and tons of boost, it would eventually make more power than the smaller Garrett. But that is just not practical for a street/track car hybrid and that power is not in the usable RPM range.

Be smart when selecting your turbo.  I highly recommend reading this book and running the numbers yourself. Maximum Boost

GT35R Knockoff, GTX3076R, Bullseye S362

Turbo Exhaust Manifold and Downpipe

If you’re working with a stock setup then you can probably find a downpipe for sale somewhere to bolt up for your swap. But if you’re working with a more custom setup then the downpipe is going to have to be custom fabricated to ensure a proper fit with your exhaust. The reason is because you’re going to want a custom exhaust manifold for the turbo application, and if you’re like me you’ll probably end up with a top mount turbo exhaust manifold.

There are a few things to keep in mind when selecting a turbo manifold:

  1. Never buy a generic EBay Manifold. You are asking for trouble. These are cheaply made, probably won’t support the weight of your turbo, and have a higher chance of cracking. Why take the risk of damaging your new swap?
  2. When planning for the manifold, be sure to take into consideration the downpipe placement with your steering column. There is not a lot of room for the downpipe or an external wastegate, but it can definitely be done.
  3. Not all manifolds will allow for the AC Compressor to be installed. If you want to keep your AC then you will need to make sure the exhaust manifold is built for that purpose.

You can spend a lot of money on manifolds, but the result can be worth it. Besides reliability, proper manifold design will allow for the maximum efficiency in airflow to your turbo. This means quicker spool and more power. Without going into a ton of detail, the main difference between a tubular, equal length manifold and a factory cast iron manifold is that you’re allowing the cylinder exhaust of each port to work in harmony to power the turbo. Otherwise you’re shoving air through the same area from different sources and those sources can fight each other, robbing you of power.

Here is an example of an Ebay manifold vs. two quality manifolds:

Cheaper EBay Manifold
McKinney Motorsports Manifold
Custom Built Lovefab Manifold

Engine Mounts

When doing a swap one of the first things you’ll need to tackle is how to mount the new engine in the vehicle. Fortunately, for common swaps there are usually several choices for engine mounts.

This is also true with the RB in the S14. Even though I had access to an R32 crossmember when doing my first RB20DET swap, I opted to go with the McKinney Motorsports engine and transmission mounts and retained the S14 crossmember. This allowed everything to mount up perfectly in the vehicle, including the shifter.

When it came time to install the RB25DET I ordered another set of mounts from McKinney and was equally as pleased. They really do a great job and they make the installation a breeze.

Used McKinney RB20DET Mounts

Carbon Fiber Hood

People have often asked whether or not a carbon fiber hood is a good upgrade. My opinion is that for a swapped motor in the 240sx it makes a difference in two areas:

  1. It helps with adjusting the weight distribution since you are adding in more engine and engine components in the front of the car. The carbon fiber hood weighs quite a bit less than the factory hood. At the end of the day you’ll want to corner balance the car anyways, but this does help. People laugh at me for saying it, but I can feel it when driving the car.
  2. I prefer a vented hood because it’s going to let some of that heat escape the engine bay. Remember, you’re stuffing a bigger engine in the car and you are generating more heat with performance additions, such as the turbo.

I have a Seibon hood with the vents in front of the engine and after the radiator. This allows the air passing over the hood to pull air through the vent. So the air is pulled off of the radiator and out through the vent instead of blowing additional hot air from the radiator onto the engine itself. This also means that the vents are not directly above sensitive electronic equipment, like the coilpacks.

I think it’s a great, practical upgrade, and it’s not something I did for the looks.

Just remember to install your hood pins to keep it from flying off at high speeds. I didn’t have them when this picture was taken, but I went with the Sparco hood pins for ease of installation. I still have a set of Aero Catch waiting to be installed. Maybe someday…