Updated Sept 24, 2001

Cool Air Induction

          Years ago I tested the temperature at the inlet of my modified stock 89 airbox. I had disconnected the air tube from the computer to the airbox, and I had enlarged the opening of the airbox. It was sucking in warmer under-hood air that way, but most of that extra heat was being pulled away by the intercooler, so I didn't really care.
         Nevertheless I wanted to see what the temp of the air was at the inlet as a base reference for future mods. On a 60^ day I took a 7 mile cruise, and at the end of it I recorded 88^ at the inlet, for a 28^ rise over ambient. The temp sensor was right up against the pleats of the K&N air filter.
         Later that week I recorded "cruise"  temps again. It was a 52^ day, and I recorded 80^ at cruise. I usually cruise with the cruise control set at 75 mph when I'm testing stuff. I saw 28^ over ambient at cruise once again.
         Very recently I moved my intake to the left front space where my battery used to reside. This space is the recipient of a small round cool air inlet that originally had a tube on it running into the computer (to feed it air). The computer tube is long gone, the long computer inlet has been hacksawed off the computer, and cool air *theoretically* shoots into the "ex-battery-area" where I've placed my K&N cylindrical filter. I tested again, but this time I tested temps right in between the pleats of my relocated K&N, on the side facing the cool air hole, and on the side facing away from it. The filter is laying down where the stock battery used to be.
         I cruised for 7 miles, and on the "cool side" of the cylindrical filter I recorded 2^ over ambient! Outstanding! I moved the temp sensor to the "warm side" of the K&N, and cruised home again... 5^ over ambient! This means that air in the filter is in the vicinity of 3.5^ above ambient, which is *far* better than I had hoped for. I didn't expect to see a big difference like that until I had sealed off the area with little walls under the hood. ...Which is great, because I didn't plan to make the little walls at all; I was moving the filter just to keep puddles from spraying water into it!. I've never experienced hydraulic lock up, and I don't want to start now!
         I truly didn't expect to see a 20^+ temp drop from an un-sealed filter just sitting in the open where the battery used to be. Surprise! The only mod to that open area is cutting off a corner of the un-used battery tray, and drilling about 10 little 3/8" holes in the fender right near the inlet of the computer (under the filter).

         Here's how I made a quick and easy low-buck 3" intake: I got the intake tube from an older 2.2 T1 car, maybe an Omni; I can't remember. The old style T1 intake tube is much larger internally than the newer 2.5 T1 intake tube. I mounted the larger intake tube over the same spacer ring that my K&N mounted onto at the turbo inlet. Same spacer, same clamp... sweet. I went to Home Depot and bought 8 feet of 3" aluminum flexible duct tubing for about $5. It will do 2 cars. I slid the end of the old T1 tube right into the metal tubing, and then put a ring of extra wide duct tape over the joint. I then used 3 tie wraps to REALLY hold the tape there forever. The other end of the metal tubing slips *right* over the K&N's inlet! A regular worm gear clamp holds it there.

 I'm not a fancy-parts worshipper, and had no intention of considering looks at all, but after all is said and done it actually looks fine.

If you haven't moved over your battery the space will be much tighter, but that aluminum ducting is VERY flexible, and does easy 90^ bends to go around things. You should be able to find a cooler spot than on the turbo inlet, where it seems to be 28^ above ambient at cruise (75 mph).

Restrictor Orifice
        What is it?
Restrict means "hold back"; Orifice means "opening" or "hole". So obviously a restrictor orifice is a hole that restricts or holds back something. In our case, it's holding back air flow.
        Why use one? Well, if you don't use one, when you try to drop pressure in a line you'll have to bleed out SO MUCH air that you'll be hard pressed to make a large pressure drop in the line.
        Where does the restrictor go? In between the source of pressure (like the intake manifold) and the bleed hole (or bleed valve).
        Here's why:

        In the above illustration air molecules represented by dots are leaving the intake manifold and heading for the actuator. Just as you can make the actuator "see" less pressure than you're really running, you can also make the MAP sensor see less pressure than you're running. Same deal with the MAP line; orifice goes between the pressure source and the bleed hole/valve. Now you know why.



Mandrel bent pipes are said to flow 35% more than crimp (or "regular" bends. Take a look below at two 3" pipes. Do you have any reason to doubt it??

Extra clamps can aid flow, when placed properly.

The hoses balloon just a little under high boost, but even when there's low boost present, you still have the pipe edges hampering flow.
The second clamp creates a smoother transition from rubber hose to metal tubing. I don't bother to use them when the flow is going the other way...

To make your own intercooler tubing, see: intercooler tubing

 Reading Spark Plugs:  Mild detonation, that you might not hear, is evidenced by small "salt & pepper" specks on the center electrode insulator. (white porcelain) They're tiny specks; the light ones ("salt") are tiny molten droplets of aluminum that have hit your insulator, then cooled off and hardened on it. The dark specks ("pepper") are carbon specks that have been blasted off of the cylinder head and piston top.
 Another common bad sign is a slight rounding of the edges of the plug's electrodes. The corners of the electrodes should be sharp 90 degree angles, not rounded. This is actually a sign of leaning out, but leaning out leads to detonation. If your plugs are OLD, this is normal. But if you put in fresh plugs, and a few passes later they're slightly rounded at some corners, you're too lean.
 These signs beg for more fuel, and/or less timing advance, and/or less boost.
 Ever wonder how even your fuel distribution is, but can't tell by the white center insulators, because of today's unleaded gas? Just throw a little 104+ octane booster in your tank and drive around for a while. You will then have a reddish residue on your plugs. The reddest ones are getting the most fuel. The whitest ones are the leanest cylinders.
 Downdraft Tube (PCV vent): The stock pvc setup sends a lot of dirty oil to your air filter. And if you put a cone filter on your turbo, there's no more airbox to run it into.
 Put a .75" ID radiator hose or fat garden hose onto the PVC outlet's metal tube (coming out of the valve cover). Clamp it on *loosely*. Run the hose down to near the road. Cut it to the proper length. Now remove it again to modify it.
 About 5 " from the bottom of the hose, put 2 skinny nails through the hose, criss-crossed, so that they form an X through the hose. Bend the ends over, so that they can't come out. Buy a stainless steel scouring pad for pots & pans. Take a SMALL amount of SS pad, and pack it LOOSELY in the bottom of the hose. Then 2" from the bottom, make another nail cross to stop the SS pad from moving up or down the tube.
 Now clamp the whole tube on tightly.
 The SS mesh will pick up oil vapors, and get damp with oil in no time. Then it acts as a filter, preventing nasty road stuff from getting sucked up the tube when it's in vacuum. I split mine open lengthwise after one year of use, and it was clean above the SS mesh.

 Ignition: You will hear people say that you need a super ignition to run high boost.  Well, then, the stock ignition is super; I've run 27+ psi on hundreds of races with no trouble.  Get good low impedence wires. I like the spiral-core wires; I've used several different brands from expensive to cheap, and they all work well. Move the coil close to the distributer so that the coil wire can be shortened to a foot or less.  Keep the wires from touching each other.  Use colder plugs than stock.  Gap the plugs at .032".
 If you experience misfire at high boost (over 20 psi) gap them at .030".
 If you experience misfire at low boost (under 20 psi) something is wrong with your stock set-up.  Investigate your cap, rotor, etc.

Cam Timing

        I'm using the "line of sight" method. I put a socket wrench on the cam sprocket and rotate it until the little extra hole in it is pointing up, and then get the timing mark to sit on "0" degrees. I stick a LONG socket on the crank pulley's center bolt and let it stay there on it's own, sticking out sideways.
         Then I look straight down from above the cam pulley, and close one eye. I move my head until the
center of the cam sprocket bolt is lined up with the long socket. If the little extra hole in the cam pulley is right in line with the cam pulley
bolt and the crank bolt, it's OK. If it's NOT lined up, you have to remove the belt and rotate the cam pulley in the direction that will
line it up.

Here's the relationship between 0-60 and 1/4 mile times. This was *NOT* a calculated table. We are dealing with the real world, here. I went through many magazines and pulled out the 0-60 and 1/4 mile times from road tests. I plotted the times on graph paper, and the result is a "real life" graph of 0-60 vs 1/4 mile. You can see that a car with a 0-60 time of 8.0 seconds is predicted to run close to 16 seconds flat. A 12.25 second car, like mine, is predicted to have a 0-60 of 4.0 seconds, although my computer program predicts 3.842. But the computer knows that I have good slicks (I told it). The "real world curve" doesn't know about my slicks. Darned close prediction, anyway! : )

Note that each light line is worth .33 seconds as you go from left to right, but each light line is only worh .25 seconds when you go up or down!

Here's a Wide Open Throttle Switch that's just a cheap "on-off" microswitch. Even Radio Shack has them. This little switch allows you to switch from low to high boost automatically whenever you floor your car. It can turn on a relay to activate a booster fuel pump, or anything that you want on only when at WOT.

 Here's a quickie flow bench set up. It will not tell you how many CFM a piece is flowing, but it's *great* for direct comparisons of: "Which piece flows better than which??" If you have a regulated voltage supply, you can make comparisons of parts tested on different days. If your voltage supply is *not* regulated, you must compare the different parts on the same day, checking to make sure that voltage isn't fluctuating during the test, with a voltmeter. You don't want to test one port at 112V AC, then test another port at 118V AC; the leaf blower will slightly vary it's output.
        As long as you have steady voltage to the electric leaf blower, you get very meaningful comparisons. The higher the back pressure reading, the less the part flows. I've tested mufflers, cats, and filters this way.
        For a head, you'd just need to seal the leaf blower to the head with modeling clay, and hold it there during the reading of the gauge.

Here is some information that I derived on the homemade flow bench.  I used the electric leaf blower on the same speed, and same voltage, on every test.  I did the tests more than once to establish repeatability.  The backpressure readings are in inches of WATER, not inches of MERCURY, nor PSI.  An inch of water is roughly 1/13 of an inch of mercury, so the gauge is 13 times more sensitive to backpressure than a mercury gauge can be.
 I used a short straight piece of exhaust pipe as a baseline for comparison.  Since 2.5" exhausts seem to be extremely popular on turbo cars, I used 2.5" diameter pipe.  I shrunk the large leaf blower nozzle down to 2.5" at the outlet, and stuck on the following:

  2.5" short straight pipe = 2" backpressure
 stock Omni glht muffler = 9"backpressure (7" more than straight pipe)
 stock Omni glht cat = 9.5" backpressure (7.5" more than straight pipe)
 stock 89 Acclaim cat (shorter than Omni)= 8" backpressure (6" more than straight pipe)
 Products For Power cat ($59.99) = 5" backpress. (3" more than straight pipe)

       As you can see, the stock Omni cat produced 7.5" more backpressure than the straight pipe, while the hi-flo cat produced only 3" more backpressure than the straight pipe. Less than half the back-pressure!

 This is useful for anybody running a stock or Bosch BOV, or any BOV made of plastic. If you leave the factory's quick release valve in place, the stock BOV will lift off of it's seat and leak at 15 psi; the Bosch will lift off at 9 psi. If you leave the quick release valve out of the BOV line, the full boost pressure will eventually rupture the plastic housing and/or the rubber diaphragm. The pneumatic circuit below will send *part* of the boost to the BOV, but will still send full vacuum to it for a fast opening valve. Now your stock BOV will be good for over 20 psi.

         Here's the diagram for a simple manual bleed. For a more complex and versatile setup visit  Dempsey's Pages . The setups you'll see there can be fed off of the intake manifold, or off of the turbo's compressor nipple, if you have one on your compressor. When hooked to the compressor outlet, high vacuum will not be flexing the diaphragm backwards; it might help the unit to live longer.
        To see what the check valves and stuff look like in real life, visit Dempsey's general instruction Page . There are many variations, but look for something similar to what the photos show.
        For the latest & greatest boost controller, go to: Super Boost Controller

  Here's a simple way to stiffen a worn or weak bobble strut to keep the engine steadier under heavy loads. Common worm gear clamps hold on a split-down-the-middle iron tube. Mine's holding up great.

        I measured the extension of the strut at rest (the length of the shiny rod) and then cut a thick little metal tube to about 1/4" *longer* than the measured extension. I then took the strut off, split the tube lengthwise, and clamped it on the strut extension. This made it necessary to jack up the rear of the tranny a little to get the strut back on. Now my tranny is "pre-loaded", and is much more stable.
         Drawback? Yes, vibrations only during clutch engagement. Otherwise, no vibrations are felt while driving around.
         Gain? Yes, I went from severe wheel hop on street tires, when popping the clutch out, to no hop. (with a pair of long smooth black marks left on the road) At the track, on sticky tires, the wheel hop went from severe (10 on a scale of 1-10) to mild (3 on a scale of 1-10).

Shimming the driver's side swaybar will put more weight on the light passenger's side wheel, and help spin-free launches. Only one spacer nut (oversized nut that's the thickness of the wood you're using) is shown, but you really use two; one on each side. That keeps the rubber bushing from being over squashed.


To raise your boost cut-out point to whatever you want, go to:    Cut Out Raiser