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Discussion Starter #1
First off, Thanks for a great forum and thanks for having me!!!! This will be my very first post and I know this has been asked hundreds of times but here goes; My all stok 89 CRX si D16A6 is due for a rebuild (347k) and I want to get idea's and recommendations on how to squeeze a little more HP out of it without sacrificing drivability, fuel economy, and keeping the D16A6 factory head. This car is my daily driver and my commute is 70 miles round trip 5 days a week and I love getting 40 mpg but I would also love more throttle response at the red lights. Thanks to all!!! Greg
 

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a CAI and exhaust setup wont have a reasonable effect on gas mileage.


Taking the head off and shaving it down a little bit to increase compression will make a better difference.


The biggest difference for fuel mileage will be in making sure all sensors are in correct working order, all ground wiring is in good condition adn free of corrosion, and all the forgotten things such as partially dragging brakes or wheel bearings are inspected.

Blocking off part of the front grill in the bumper will help with aero a little bit.


In my 1997 civic, I was missing the condenser block off panel, and not knowing its effect, found own locally and installed it. Surprisingly enough, it was worth probably a good 2-3mpg on my car (I drive on the interstate quite often)
 

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.020" off the head and run a Y8 HG

Roughly 1mm total difference which will retard the cam one degree for slightly more top end power.

You'll want to replace the all the valve guides in the head as well.

Z6 intake would help some.

See if you can get 75.5mm or 76mm pistons and have the block bored and honed to fit them.

My 89 HF with D16A6 stock bottom end, Y8 head, intake, and gasket would get 48 mpg highway at 65 mpg with a close ratio ZC trans and a good driver....I'm a really good driver.



Tires make a 3-4 mpg difference. Prius LRR tires on Miata super light weight rims helped to get that 48 mpg on stock ECU. 4-2-1 Ebay header and 2.25" exhaust with cat...nothing special.

D16a6/Y8, VTEC not hooked up...

 

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Discussion Starter #6
Thanks Transzex! I'm sure an overbore will be required with the excessive mileage on the block. Any recommendations on a quality set of pistons? Will stock rods with new bolts be ok? Would you stay with the stock cam or go up a step or two? Sorry for so many questions. Thanks again!!!!
 

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Also check rarely changed items like the fuel strainer, fuel filter, and clean the injectors.
Along with regular maintenance items like plugs wires fresh clean oil and oil filter at all time along with an air filter.

Make sure anything that sucks, blows, or rolls does so freely.
 

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Discussion Starter #8
Anyway, for the immediate time being I'm thinking I will just replace the oil pan gasket and install a DC header along with a cold air intake. Other projects have arisen.
 

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make sure if getting an intake, you get one with a tube size that fits the throttlebody.

Not of that 3inch ebay nonsense that hurts power and fuel mileage

depending on which throttlebody, 2.25 or 2.5" tubing, a simple 45 degree coupler for a bend, and a velocity stack style filter will enable a bit more efficiency.

I have a blox filter and stack kit that uses a 6" cone filter mounted to the 6" to 2.5" velocity stack, that then mounts on a cut piece of exhaust piping with a 45 degree long sleeve coupler (simply means straight bits are roughly 4inches long) that is connected directly to throttlebody.

Its on my automatic civic, and it gave me around 25-40 miles per tank improvement during 90% highway driving. It snorts pretty good, so gas mileage usually suffers when traffic is minimal and weather conditions are good.
 

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I rebuilt with PG6B pistons, so half mm overbore and flat top, head was slightly milled, new bearings, new oil pump, arp rod bolts and reconditioned stock rods. metallic headgasket. With the stock cam I had to back ignition timing way off due to pinging, it was better with a crane stage 2 cam, and then even better with the Rocket stage 4. I put isky springs and new oem retainers/clips in the head as well. Skunk2 alpha header, pwm test pipe, edelbrock intake manifold and throttle body. arp head studs as well. h22a4 injectors, and tuned it with hondata s300. my fuel consumption says I could be making a theoretical 170 crank hp. but without dyno tuning to get the correct ignition timing I suspect based on performance it is 150-160 hp. Originally I had the smaller intake tubing for a cold air intake, but after going with the larger throttle body I put a 3 inch which was shorter and had a velocity stack and saw much improvement. I am very happy with my engine, and sometimes when I cant drive the car I think about selling it. then I go for a drive and never want to sell it.
 

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Discussion Starter #12
Thanks a lot v4!!! That is some great information for me to adhere to!!!
 

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It has worked for me and can at least give you ideas how others did it. Pretty much except for a dyno tune I have decided I am done with performance and will focus on not letting rust catch my car now!
 

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Discussion Starter #15
First off, Thanks for a great forum and thanks for having me!!!! This will be my very first post and I know this has been asked hundreds of times but here goes; My all stok 89 CRX si D16A6 is due for a rebuild (347k) and I want to get idea's and recommendations on how to squeeze a little more HP out of it without sacrificing drivability, fuel economy, and keeping the D16A6 factory head. This car is my daily driver and my commute is 70 miles round trip 5 days a week and I love getting 40 mpg but I would also love more throttle response at the red lights. Thanks to all!!! Greg
Would a Z6 intake and throttle body be a plug and play affair and would the power gains be worth the effort?
 

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The extra power and response is worth it, you will have to check out what is needed to swap to obd1 intake stuff. Id limit yourself to spending no more than $100 on the setup though, including the IACV

I forget if you need to KEEP your current fuel injectors, as I have forgotten if your d16a6 fuel stuff is saturated or peak-and-hold style.

Im sure there are some guides or DIY info out there, its a lazy weekend for me.
 

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I did a d16a6 with mild ported head, overbored, 4-2-1 ebay headers and a good ecu tune for fuel economy and a can get almost 40mpg and picked up some HP :)
 

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Discussion Starter #19
Anyway, for the immediate time being I'm thinking I will just replace the oil pan gasket and install a DC header along with a cold air intake. Other projects have arisen.
The time is now and I have begun the engine removal process. I only get to work on it for a short time after I get home from work and I don't have the luxury of a shop so I won't be quick in getting this job finished. I have never built anything other than old Mopar's and Chevy's so I need recommendations for quality parts (brand names and suppliers) including pistons, bearings, gaskets, and a lightweight flywheel.
 

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Discussion Starter #20
No recommendations so here is what I bought;
CP pistons
ACT lightweight flywheel
ACL bearings
Genuine Honda gaskets throughout along with a Y8 head gasket.
Suppliers are Honda Parts Now, Summit racing, and various e-bay vendors.
 
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