<FONT SIZE="4">EDITED 7/19/05</FONT>
Any tech questions please create a new post, this is too old and people simply take it as another free bump and a
good job reply.
SOHC BABYÖ.Cause itís cheap
First things first, enabling the engine to breath; after all, engines are nothing but air pumps.
: To start off, we look at the filter and piping. Cold Air Intakes (CAI) although some assume just relocate the air filter into the front bumper, are actually acoustically tuned to the engines they are made for and allow for a rather comfortable bump in the mid-range horsepower. K20s (RSX-S for this example) have been dynometer (dyno for short) proven at +20 whp (wheel horsepower) with a CAI as apposed to the 5 whp with a "short ram" design. The AEM V2 although costs more is also designed and tuned for both mid and upper RPM acoustics. If you donít have to worry about water, get a CAI made with acoustic testing. (Read: AEM)
Following the air flow we come to the throttle body. This is more of a throttle response upgrade than a horsepower upgrade. UNLESS the stock throttle body is too small to allow all the air the piston chambers can pull in at wide open. Basically, adding a larger throttle body allows you to be a "full throttle" faster because of the larger volume of air. Any throttle body for an H series B series or D series are interchangeable, with one catch; you need to pay attention to where your IACV (idle air control valve) is. For example, the D16Y8 (96-00 EX) has different mounting points and uses a 2 wire IACV. On the automatic, the IACV (which is a 3-wire) is mounted on the throttle body and the manual has the IACV mounted on the back of the intake manifold. The later model VTEC B series and B20 (CRV) throttle bodies are all 60mm in size. Except for the ITR, this is 62mm. The H22 is also a 60mm throttle body, while the Civic gets a puny 56mm. Make sure when you add the larger throttle body that you port match (make the holes the same size) the opening of the intake manifold.
Next in line is the intake manifold. For those of you who want OEM, you want the D16Y8, often referred to as the Type R manifold for the D series. It has somewhat short and fat runners and a large chamber to allow the air to distribute to each cylinder properly. The Y8 IM has the common horizontal throttle body. Here is a link Courtesy of VTC_CiViC with a complete how-to: http://www.makuragi.s5.com/civic_99/Y8maniswap
/ NOTE: This will not work for the D17's. Honda had the bright idea to make it a return-less fuel system. Recent research has developed aftermarket IMs for the N/A SOHC. Edelbrock is at the top of the list on this one. Not only does it fit better than the Skunk2. You do not have to raise the fuel pressure to get more power on the Edelbrock IM like you do have to with the Skunk2 IM. Lastly, there has been a recent interest in taking motorcycle Individual Throttle Bodies and attaching them to an OEM intake manifold cut at the runners. Find an example at http://www.homemadeturbo.com
In my personal experiences, I had a AEM short ram intake when I was asked by Edelbrock to test out their Intake Manifold. So I needed a before dyno. With a AEM short ram, DC 4-2-1 header and a 2.5" Cat-back: The D16Y8 put down 116whp. Once we had the Edelbrock Intake Manifold installed, peak horsepower jumped to 121whp, with the only loss in power being 2whp just before VTEC crossover for a simple 25rpms. Once that was completed, the car was loaned to AEM for design and fitment of a CAI. After a week of research, the CAI was designed and not only did it add 10whp with the "AEM HUMP" (a term used for the mid-range increase in HP) but added another 5whp overall! This brought the total to 126whp! To put this into perspective, a stock Civic EX puts down 109whp.
Lets start off with the exhaust manifold (header). There is not a single OEM exhaust manifold out there that doesn't need work. But, for those of you who want to budget a used aftermarket manifold for the EX is where you want to go. There are a lot of people out there who by the time they can swap have already put a header on there D series and now need to sell it. If you have a DX, LX, or HX, You will have to relocate your catalytic converter under the car to use this header configuration (which happens to be illegal in some states). There are two different designs for a header. The 4-2-1 (or Tri-Y) and the 4-1. It is said that the 4-1 costs you low-end torque to give you more power up top. However, if you follow this link http://www.automotiveperforman....html
you will see that some 4-1's have better low and mid then the 4-2-1. Header designs on stock engines are so good that this is more a preference thing until you start building. One advantage of the two-piece 4-2-1 is that you can remove the lower half when you need to pull the oil pan, instead of pulling the entire header. There are some new designs for the SOHC headers as well, they are all well designed but also tested and designed for built engines. I suggest speaking to each company and seeing what the recommend before deciding. Bisimoto is one of these designs. Available through http://www.exospeed.com
The HF (all Civics other than the EX and SI) exhaust manifold can be modified to add a turbo. Then you don"t need to spend the extra money on a turbo manifold. See http://www.homemadeturbo.com
for more information.
Following the exhaust stream out, we come to the Catalytic converter. Unless yours is old, don't worry about it. For those of you who can afford to upgrade the cat, tests have shown that a 3" free flowing cat is close to the flow rate of a 3" test pipe. In fact some people were shocked at how well a free flowing cat works (and it's legal but only on OBDI vehicles). Or go with the $10.00 test pipe from Home Depot (NOTE: Test pipes are not smog legal and you face a $3,000 fine). That's right, people have even made there own test pipes with minimal effort.
After the catalytic converter, is the Cat-back. Most people recommend using a 2.25" sized exhaust for the little 1.6L. And a lot of the aftermarket exhausts are 60mm or 2.3 inches. I believe that you should actually use no less than 2.5 inch. My dyno results proved that it adds more power than the 2.25 and I gained another 1 whp throughout the power band when I removed the silencer from the muffler. But, you also want to make sure you get mandrel bent piping and straight through designs on both the resonator (if you have one) and the muffler. If you don't get the straight through designs, you will loose power, it's that simple. However, with straight through designs also comes sound volume. A good compromise has is an exhaust that comes with a silencer. You can remove them for track days and leave them in for daily driving, as stated before, only losing about 1whp on a stock engine. NOTE: I seriously recommend a resonator. Who likes sounding like a bumblebee???? Exactly, the resonator will get rid of the sound and actually deepen the tone of the exhaust.
Remember this, the shorter the gears the better. It is easier for the engine to push/pull the car. The VTEC engines have always had the shortest gears and it is a "bolt on" part. The 96-00 transmissions will bolt on a 92-95 Civic. One small thing to consider is that the 96-00 transmissions have steel shifter forks instead of the aluminum forks that are in the 92-95 transmissions. For you cable transmission guys, there are the Hasport kits that convert your Cable to Hydro. And, SSR offers a 4.7 and 4.9 Final drive for the D series Hydro transmissions. HX/VX/CX owners, upgrading the transmission should be the first thing you do, this is a HUGE difference.
Once you get the shorter geared transmission or already have one, a limited slip differential is a great option for FWD cars that are putting down decent amounts of power. I recommend Quaife because its gears, not a clutch and it comes with an unlimited lifetime warranty. A lighter flywheel is also a recommendation. Not only do they increase throttle response, they "free up" horsepower by decreasing rotational mass. (Just like the whole argument of reducing wheel weight that goes around on H-T constantly) The aftermarket offers weights varying from 8.5 to 15 lbs. You can shave your existing flywheel to no less than 13 lbs. However, this is a controversial issue and if you search will discover how everyone feels about it and the dangers that can come with it. The clutch, although capable of handling up the 12psi of boost, should be replaced if you are considering more than 125whp. Personally, Iím running Centerforce Dual Friction on my Cobra (yeah no more Hondas for now) and itís holding up fine after more than a year of abuse.
Well, where the hell do we start? The motor mounts all have gaps in them. jimfab.com has inexpensive polyurethane mounts. And the mounts that they donít make you can go to hasport.com and get the rest. Okay, now that you got that sucker still, lets increase some power. On a naturally aspirated engine there are # things you can do.
1. Increase the compression
2. Increase the displacement by bore (size of pistons) or stroke (crank)
3. Add more aggressive cams or cam for the SOHC.
One way to up the compression is to mill the head. It is very important for you to not remove more than .03. If you do, you risk timing issues because the timing belt is going to have slack and you will risk jumping teeth on either the cam gear or the crank and your timing will get screwed up. You can also get thinner head gaskets, the Y8 is cheap and is the thinnest metal
OEM head gasket that you can get. Now that we have covered some inexpensive increases, let us move on to pistons. The 1988-1989 D16A1 Engine came with some really high dome pistons, they will increase your compression ratio as follows:
d16a1 pistons (stock bore) in the following with a y8/z6 metal head gasket (no mill):
d16a6= 11.0: 1 compression
d16z6= 12.0: 1 compression
d16y8= 12.6: 1 compression
Obviously high compression and you 91 octane folks should consider a thicker head gasket. However, 12.5:1 can be driven daily on 92 octane. Since you have decided to open that sucker and upgrade the pistons you should also consider upgrading your rods. Whether you decide to shot-peen your stock rods or upgrade to some LS rods, it's up to you. The LS rods can fit a D series piston simple by removing a little material from the inside of the piston. When upgrading these, you should consider new OEM bearings and ARP rod bolts. Strength is always a comfort, right? The head is what traps all of the power in any engine. Be it naturally aspirated (N/A), nitrous injected, supercharged, turbocharged or all three. It has the valves that allow the air in and out of the combustion chamber and the cam that opens and closes the valves. Porting is the process of removing material to make the holes for the valves larger to allow more air even if you use the stock cam. But, within the head you have all of these moving parts that rub against each other, even with oil there is friction. To reduce friction, you can get bronze valve guides, coated valves, and roller rockers. Roller rockers are cam followers that have wheels instead of a contact point. They greatly reduce friction and, the D16Y5 (HX) has them! Unfortunately, it only has a 2-lobe cam instead of a 3-lobe cam. Again another crazy topic that has been discussed a few times. Still with a custom cam, This VTEC-E head could theoretically produce more power than the D16Y8 VTEC head ever could. Since the rollers would allow for a cam lobe so aggressive that the regular followers would fail. Adjusting the cam with a cam gear can also change your power band to what best suits your driving, some drive easy, some drive hard every now and then, and some visit 6800 with every stop light and every shift. Well, almost. Remember, an engine is an air pump, the more air it moves the stronger it is. And the best way to move air is to open the valves really high (lift) for a long time (duration). (well to a certain extent) A good quality camshaft maker is Crower, my personal choice. There is also, Zex (comp cams), Crane, and Skunk2. Some companies that make regrinds are Hondasaver and Gude. I personally don't like regrinds. They were stock cams that had material added then reground off.
If you decide that you want to build a monster engine, the D16Z6 head has the best design for port flow. The ports are straight and easy to work on. The only draw back to the Z6 head is the combustion chamber, but there is a solution. You can have material welded into the chamber to not only increase resistance to detonation but also increase your compression ratio by decreasing cylinder head volume. Again, refer to http://www.exospeed.com
for combustion chamber work.
Hey, in case you didn't know, heat kills. Keeping your engine cool is not just the radiators job though. The water pump, thermostat, your coolant/water mix, and even the radiator cap affect your ability to cool the engine. If you change one you affect the whole system. Radiator caps pressurize the coolant to raise the boiling point (good) but, if you over-pressurize; the radiator could fail because of the plastic tanks on the sides.
There are two radiators that you can use for the Civic; there is the Del Sol, which is a dual core. Or it has two cooling cores, one in front of the other. And the other is the Integra. You have to make custom mounts but you will have your needed cooling for sure. Or you can purchase an aluminum aftermarket radiator that is a very efficient.
For you track guys, since antifreeze isn't allowed, there is a product called water wetter. You mix this and water, no coolant. It is discussed in the racing forum if you haven't been over there. DON'T use this on the street. Antifreeze does exactly that, when water freezes, it expands and will crack your block, radiator and head. You've been warned.
Fuel isn't as easy as we all would wish; a fuel pressure regulator (FPR) isn't necessarily a good thing. Too much fuel can cost power, and forcing your injectors to flow more than what they were made for can hurt them as well. I personally believe that you should upgrade the system as a whole, injectors, fuel pump and regulator, to what your setup is requiring. http://www.edelbrock.com
has a bunch of listed formulas to calculate if your injectors are going to be at 100% or not. The stock Civic (other than 99-00SI) and Integra LS fuel pumps only flow 79lph and the SI, GSR, Type R flow 135lph. In fuel tuning, the DOHC ECUs, can feed more fuel than needed as well. The best way to figure the needed fuel out is to tune on a dyno that also has the capability of reading your air to fuel ratio. Whether you're using a FPR or a fuel controller. Apexi makes a VAFC or VTEC Air Fuel Controller. This allows you to adjust your fuel amounts in the RPM range. These are good but there is something better, Hondata. That's right, Honda is in Hondata, and they are making great amounts of power on the SOHCs. Supplying fuel is just one part though. You have to ignite it. Fortunately, Honda made a great ignition system right out of the box. And Erik's Racing proved this by using an OEM ignition in their 10,000RPM 9 second Civic.
Well, that just about sums it up for now; feel free to add any knowledge. However, if you have a question about something, please use the search or call attention to yourself and post a new thread. Thank you for reading.
Don't waste your money on a B16!! It's still a torque less 1.6L engine. If you truly want to swap an engine save for a B18C1, you've saved this much already save a little longer.
Modified by Spade at 5:23 PM 7/19/2005
Modified by Spade at 5:23 PM 7/19/2005