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I drive a 1987 CRX with a D15A2 engine. The stock carb has been replaced with a Weber 32/36 DGEV. Set up for SCCA ITC class, the engine is basically stock. What simple changes can be made to increase horsepower and torque? Reading about various engines, the D15A3 is said to produce ~50% more hp and the only difference seems to be the head. Can I get at least some of this power increase by swapping to a D15A3 head? Can I continue to use my current Weber induction on the D15A3 head.
I dont know the restrictions on your class but headwork and a delta 272 cam would be the most bang for your buck. If you can find another head mill it .030 and you would be surprised what $200 can do for your single slam. If you can run a aftermarket crank pulley have a aluminum one lathed to just the alternator row and have the clutch, flywheel, and pulley balanced together. You can lighten the stock flywheel or run a aftermarket 9-11lb chromoly flywheel and ive had zero issues with the ebay flywheels. Shim the oil pump and rev the 1.5 until power drops. I know a oil cooler would be a good choice and the valvoline vr1 race oil is excellent. These mods are the most inexpensive, reliable, and are very gratifying from my experience. Some may shy away from the aluminum crank pulley but with the d15 stroke and balancing the items mentioned it will rev like a street bike compared to what your currently working with.
With your question about the difference in heads if you can run a 16 valve non vtec head and have it ported and polished you have lots of them sitting around pic a parts, offer up, c list, forums, etc. Just be sure to use the timing belt intended for the head your using.
The information you provided is greatly appreciated. It is pretty much a bullet point list of things I can do this winter to improve the performance of my engine. As for using a different head, is there any difference between the fuel injection and carbureted intake manifold design? Can my Weber carb and Honda intake manifold be bolted onto a head that previously had a fuel injection system?
I was going to bring that up but it gets a little more expensive. You would need to convert your car to obd0 or obd1, install a fuel pump, and go multi point injection. Theres plenty of info online and im leaving out a bunch of it. Doing so you can upgrade the intake manifold to a d16y8 which would make a very big difference. I had a dual point crx that was fuel injected and after wiring the car mutli point and using a stock crx si intake manifold the d15 woke up and made awesome power. Ive had d16 non vtec si crxs and the d15 was similiar on the top end minus some torque. This is the rabbit hole of tuning it can go on forever, send me a pm if you need any help.
Again, I appreciate all your information and the knowledge you are sharing. I really don't want to go to anything that calls for adding an ECU. Being old school, I like the simplicity of a carburetor. While I know this, the carburetor, will not give me the most power, it will do what I want. There are still several things on your list that I can do to increase my engine power.
Can you give me any leads on where to purchase things like a race cam, lightened flywheel or aluminum crank pulley? I spent a good bit of time on the internet this morning but was not successful on locating these parts for my '87 CRX.
Call up John at Delta camshaft in Tacoma Washington, the 272 grind is perfect for roadrace, he also has a grind for the Bisimoto 2.4 cam. Spend the money on a good header the 1320 randy monroe d15 d16 race header on ebay is less than $300. A 3" exhaust has been proven to make huge gains even on small displacement d series engines. Your battery is heavy replacing it with a lightweight race battery along with any weight reduction would help. The gift of your chassis is how light it is. Im sure its a demon on the turns but with some extra hp and tuning after cam, header, exhaust, etc, it will be even more fun to drive. Shy away from the aftermarket crank pulley if you can that would be a last resort but just search parts engine parts based on d15 keywords more so than searching by your make and model. The oem cam needs to be mailed to Delta, they grind it and ship it back to you. Hope this helps i enjoy the conversation.
All of your suggestions and information are appreciated. The car was built by Will Perry of Sale Creek, TN. He raced the car until parking it in his workshop in 2005 as he began campaigning a newer CRX. When I purchased the car in December of 2017 it had been well sorted out. As I am learning to drive the car towards its potential, I am thinking about getting just a little more power.
As for changing to a light weight battery, a $200+ battery will save me about 15 pounds. In the past several months I have personally lost almost 25 pounds at no cost.
NASA-SE event at Road Atlanta in June 2020. Passenger seat was added for NASA HPDE instructor. Recently added an AIM Solo 2 GPS Data Logger to help me see how I am doing and where I can get better.
10-15-2020, 04:36 AM
D15A2 power increase options
