My dad and I put a 95 CX motor w/ Hf trans into a 91 Crx Si.

We did this for fuel economy...we were hoping to get 55+mpg. So far, mileage has been kinda disappointing as he's only getting 40mpg. (In a stock Crx Si my dad has been able to get 47mpg, using hyper mileage techniques.)

Currently, the setup is as follows.

Cx Motor. (bone stock)
91 Si Intake Manifold (Head matched to intake ports)
91 Si Exhaust Manifold
No Catalytic Convertor
HF Transmission
Si Ecu

Now, what can we do to get better fuel economy. Would going with an HF ecu yield better results?

In any case...suggestions are welcome.

 

hf ecu would probably help a little bit the hf crx actually have a shift light on dash that runs with the ecu an actually tells you when to shift to save fuel.. kinda funny honda was doing it in the early 90's what other manufactures are doing finally 20 years later. also with the hf ecu being for a 1.5 8 valve engine and not for a 16 valve 1.6 it should have alot less fuel going to it and running a little bit more leaner... i know when i changed my hf crx to a 1.6 it was slow as crap still till i put the si ecu in it and took the HF ecu out...

 

the car it was originally in only was rated for 42. the 1995 cx motor was 70 hp i believe. the crx hf motor made only 62 hp i think, that would account for part of the problem. and like 1990 crx said, a ecu swap might help as the tune is different.

 

Also you said that your running an SI intake mani and exhaust. So that means its trying to breath like an si, if you were to put on the HF intake/exhaust (super skinny) you would go slower (thus geting more mpgs).

 

I agree with you on this...and will switch once an hf intake/exhaust manifold are located.

Our next step will be the HF ecu.

 

1 prop you might have is the EGR system its only 3 wires that plugs up may not be necessary not sure if it would throw check engine code or not. i still have the original hf engine with the intake manifold injectors and egr attached pm me if your interested.

 

I think you should ask at ecomodder.com. You will get some very informed answers, especially about crx's.