Stock 90 CRX HF.

I think redline is around 6000. Is it something to do with the transmission? The 8 valves? Some other lighter/thinner engine parts that wouldn't handle higher revs?

Just curious. I enjoy the mpg, but want to know.

 

I think it's more like 5500, maybe lower. My guess is valve springs, considering the whole intake system is tiny the motor probably couldn't make use of higher rpm anyway. I had an E30 Eta that redlined at like 4500 because the intake springs weren't stiff enough to react any faster. The transmission shouldn't have anything to do with it.

 

With 8 valves and the valve lift/duration equivlent to a lawnmower engine, it would practically choke it itself to death above 5500. Honda never designed it to go fast, just get good MPG. And that it does, and VERY well lolol. -Later,BR

 

Weird, I got a reply in my email but it's not showing up here...

"Here is the message that has just been posted:

alx_90ef
***************
why are you reving up an hf anyways?

its not meant for that.

swap that weenie engine if you wanna mess around.
***************
"

 

It got said but HF= High Fuel Economy.......Honda litterally adjusted ANYTHING possible to cut weight and offer better MPG.

 

lol, what a clown.

 

No doubt about the HF. I enjoy it for what it is (in stock trim), I just wondered if there was a way to retain the fuel economy when below 5500, but get extra performance when revving. hmm... sounds like I am talking about VTEC...

Always wanted to (but it's not in the cards at the moment) to swap in the VX (92-95?) VTEC-E motor from the bubble hatches of that vintage. Probably not a hard swap either. But that's for another thread (search first, I know).

 

Friend of mine just finished that swap in a 91 HF a couple weeks ago. Runs great but you have to mess with the wiring a little to get 16-valve mode working.

 

Get a dx if you want mpg and pep.

 

It's more indepth then a couple of wires. Try 18ish for the engine harness, then double for an engine jumper harness, ~50 ecu jumper harness. That's off the top of my head.

I suppose the fuel injectors would be an additional 8, plus putting them all together is 9ish.

Timing belt bracket/mod.

I had to do a little more with my z1 swap in my rt4wd.

 

Wiring doesn't bother me if I get clear instructions (take these, re-pin into those).

I had a DX before. Only thing I never had was an Si (had 2 DXs, 2 HFs, and then this one, which is one of my 'original' HFs come home).

 

the ecu

 

?

As stated, valve springs aren't meant to go that high. Probably get a floating valve that smacks a piston. Then no more good gas mileage.

Honestly, if you want pep and speed and want to keep the HF. Then drop in an SI motor. Basically direct swap in with I think 1 depin.

 

no, if im not mistaking the hf shares the same d15b2 motor as the dx which due to the programming of the ecu has a higher rev limit, hf stand for high fuel economy which earlier quoted is why it has such a low redline and less power

 

dx and hf ecu's are not the same.

 

you wouldn't get the same mileage if you did any modifications to improve power, except if you put on a CAI and header. Those increased my mileage because IMO it frees up restriction. And the highest I ever heard of a DX getting is like ~40. In my 91 HF the highest I achieved was 64.1 mpg.

and it is true about the lightening up part. Not only were they going for economy but they were trying to sell the car to the people who couldn't afford the Si. Take for example the back trunk cover and the dash clock and even the passenger mirror. I mean those together have got to weigh 6 maybe 7 lbs. hehehe. They were really trying to lighten the load though.

and whats fun about the HF is that even if you do stress the motor and drive it hard you still get good mileage, but just not the extremely "Toyoto prius, Suck it" mileage that you can get if you drive it slow.

 

8 valves. enough said lol

 

My dx got 52 easily with a bad wheel bearing and an auto tranny! NOw I have a SOHC zc and a dx 5 speed tranny and I still easily get 45-50 mpg. I drive it 140 miles round trip to work everyday.

 

that's what i said

 

Aw got you.
They are not the same motors. Just to clarify that.

 

ok then you can get good mileage in a dx, but you still can't get the mileage that I am getting. Sorry but unless you lighten the load on the Dx you just aren't gonna get the High Fuel mileage of the HF.

 

You would be surprised what you can get when you tune for fuel mileage and not power. A buddy played with his zc/z6 minime and was able to get mid/high 40's.

 

x2



Also, if you want to get rid of your 5k redline, swap in an SI or DX cluster. lol

 

true...this should just about answer all his questions

D15A2
Found in :
1984-1987 Honda CRX HF Grifin
Displacement : 1,342 cc
Compression : 10.0:1
Power : 60 hp @ 5550 rpm
Torque : 73 ft-lb @ 3500 rpm *** Redline : 6000 rpm
Valvetrain : OBD-0 8/v EFI (HF Model)
Economy : 49/54 mpg
Gear ratios : 2.92/?/?/?/0.65
Final drive ratio : 3.58
Also found in 1984-1987 Honda CRX DX (USA)
Displacement : 1488 cc
Compression : 9.2:1
Power : 76 HP @5500
Torque : 84 ft-lb @3500
Valvetrain : 12v SOHC
Economy : 31-38 mpg










D15B2
Found in:
1988-1991 Honda Civic GL/DX/LX
1988-1991 Honda Civic Wagon Wagovan/DX
1988-1991 Honda CRX DX
1992-1995 Honda Civic LSi Hatch/Saloon (European Market)
1992-1995 Honda Civic DXi Hatch/Saloon (European Market)
1990-1995 Honda Concerto (European Market)
Displacement : 1,493 cc (91.1 cu in)
Bore and Stroke : 75 × 84.5 mm (3.0 × 3.33 in)
Rod Length : 134 mm
Compression : 9.2:1
Power : 92 hp (68.6 kW, 93.3 ps) @ 6000 rpm
Torque : 88 ft·lbf (12.2 kg/m, 119 Nm) @ 4500 rpm
Valvetrain : SOHC (4 valves per cylinder)
Cam Gear : 38 tooth
Piston Code : PM3
Fuel Control : OBD-O DPFI and OBD-1 MPFI
Redline : 7000 rpm, 6500 rpm rev limiter
Head Code : PM6
ECU Code: PM5/P04

 

Probably the crankshaft is much thinner and weaker too. I wonder what kind of MPG you could get, if you gutted out all of the interior.