Honda D-Series NA Performance

The Honda D Series motor was in production and put into a ton of cars from 1984 to 2005.  They have varying power levels and trims but the basic motor is the same.  You can check out this Wikipedia article on the web for all the different variations of the engine. 

What I am more interested in is increasing the power levels of this lower end engine.  Achieving cheap speed and not spending a ton of money to accomplish this is my goal.  This engine is found in tons of cheap Honda’s all over the internet and can be a nice little project for someone, me included.

Keep in mind that adding power to any motor is fun.  Increasing the power even a little bit can improve the driving experience of a vehicle by leap and bounds.  Even more so if there is some suspension tuning and other items involved.

Let’s start by going over what kind of modifications you can do keeping the motor in a naturally aspirated configuration.  Basic bolt-ons come to mind like and intake system and exhaust.  It seems that a basic header can improve drivability and increase mid range torque quite a bit to give the engine a little bit more grunt.  It is also possible that the header can give you up to 5 HP more at peak.

You can put on a Cold Air Intake or a Short Ram intake and maybe see 1-2 HP gain, but putting a K&N filter in the stock air box may accomplish the same thing.

They make intake manifolds for these motor a plenty.  This seems to be where you can actually gain some power so there are a couple of options from many different companies.  I was able to find a dyno sheet on the Edelbrock Performer X for the D-Series that showed a 5+HP gain using their intake manifold.  I am going to make the assumption that the others will gain around the same.

At this point, you’ve put the easy bolt-ons to the D-series motor and you’ve bumped up HP to maybe 12 more than you had before.  That is not too bad, considering they don’t make much power to begin with, if you are looking at percentages, it would be in line with doing those same mods on any other motor.  If you started with 100HP and now have 112HP, which would be a 12% gain.  Not too bad!

If you are interested in keeping the car Naturally Aspirated, there is more you can do to increase power some more.  A nice camshaft will gain you some more power as well.  Bisimoto and Crower both make camshafts of varying capabilities both offering street and race performance cams.  I have not found any dyno sheets that show what the gains might be but a stage 1 cam would seem to net you about 10% more HP and a stage 2 around 15%.  Adding another 10-20 HP to the naturally aspirated motor is not too bad.  If you had all of the items listed above you might have that little D pushing around 120-130 HP.  Keep in mind; by percentage increase all these modifications are worthwhile.

There is some more you can do if your goal is a Naturally Aspirated D Motor.  You can change out the pistons to increase the compression ratio.  If this is a route that you want to go in, you can pretty much exchange any D-Series piston into any motor since all D-Series are 75mm bore.  There is power to be found here but not much and is probably not worth the money.  The general rule of thumb is that for every point of compression, you gain approximately 4% more power.  Making such little power there is really no need to strengthen the internals when staying Naturally Aspirated.  If you went from the average of 9:1 to 11:1 you would only gain another 10HP.  If you had all the money in the world, this may be worth the cost, but I know I’m not doing it…..

That is my D-Series All Motor post, and I would probably go as far as putting in the Cam to get to that 120 HP number in my stock d-series.  I would definitely pass on changing the pistons for higher compression ones as that would not be very cost effective.

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