I am wanting to put a SI intake manifold on my 91 crx hf. WIll this fit? is it jsut a bolt on?

 

boltsup but you'd want to use the PM6 ECU and injectors as well. Not too sure that you would gain that much power because if you use the HF cam it can only handle 5K rpms and is geared for fuel efficiency, not power. HTH

 

actually the HF ECU should still work with the Si Mainfold... They are bout MPFI...

 

Two things.
First, the injectors are the same. Both HF and Si use 240cc/min injectors
Second, the HF manifold uses a EGR valve the Si doesn't. If you use the si manifold with the HF ECU you will get a CEL.
So use the Si manifold, HF/Si injectors, and Si ECU. DON'T over-rev the engine tough.

 

what would be over reving it? Redlining? or before

 

thanks for clearing it up...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91crxmachine_2 &raquo;</TD></TR><TR><TD CLASS="quote">what would be over reving it? Redlining? or before</TD></TR></TABLE>

HF cam redline = 5K
Si cam redline = 6.8K (IIRC)

 

just wondering, would it even be worth it to swap manifold???man, cause HF is problaly the slowest thing i been in...i'm waiting for my d16z6 to finish so i could swap that in my rex...but as for now...i'm stuck with the Hf motor...anything possible to free up some power???like switching tranny??heads?? etc??? thanks!!

 

um been there done that, it is totally pointless considering that the ports on an HF head are like half the size of the Si. You can only suck so much air through a small straw regardless of how big the person mouth is doing it.

 

any small thing will help, swapping heads should net you a nice powergain, provided the valves dont hit the pistons. HF's only have 2 valve reliefs per cylinder and they have dome top pistons..

 

the Si manifold will fit , but will not run right , the Si manifold is designed for a 16 valve head , the HF is 8 valve.

 

you cant do anything with the HF motor not even enough valve clearance for a mini me setup

 

thanks! guess i'll just keep saving gas money until my z6 is through.!!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by civiccrx21 &raquo;</TD></TR><TR><TD CLASS="quote">you cant do anything with the HF motor not even enough valve clearance for a mini me setup</TD></TR></TABLE>

ive got a head from a 96 dx and a pm6 ecu lying around... do you guys think it would work if i paired these with an si intake manifold on the hf block?... i also have a throttle body from a 91 ls... any gains would be fine cause it would cost me next to nothing

 

just spend some money and get a different d-series bottom end. the HF motor is crap, and if you try and use the HF block with a different head you will have problems.

 

ditch the HF motor

 

i can drop a SI motor and tranny in right, bolts right in
no mods?

 

Yup it's not worth it.
Still 8v still small ports.
I just took off the HF header and swapped it with the stock 4-1 Si Piece and messed up the Torque below 2500. Smells like gas too!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91crxmachine_2 &raquo;</TD></TR><TR><TD CLASS="quote">i can drop a SI motor and tranny in right, bolts right in
no mods?</TD></TR></TABLE>

yes, but use the PM6 (Si) ECU when you do because your HF is EGR equipped and the d16a6 is not. oh, and you might have to use Si axles and knuckle/hub assemblies too.

 

wow I'm glad I got a CRX DX instead of HF now....

 

DO NOT TRY TO PUT ANY OTHER HEAD ON THE HF BLOCK. as soon as u turn the motor over the pistons will come up and jack your valves ruining half of them. oh, and the Si motor is not a 8valve motor like that dude said it was.

 

oh yeah, if u swap the Si motor in and tranny u will have an entirely different car. do not listen to what that dude says, the si motor rulez! u will love it, i gaurentee it

 

and it will all bolt right in
i should be able to do this in one day if i have a garage that lifts cars right.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">ive got a head from a 96 dx and a pm6 ecu lying around... do you guys think it would work if i paired these with an si intake manifold on the hf block?... i also have a throttle body from a 91 ls... any gains would be fine cause it would cost me next to nothing</TD></TR></TABLE> Hey Reid the other day when i was talking to you about that head on the hf block. I forgot that the hf pistons only have two valve reliefs instead of four wich could be a problem. But there has been a few people on the board that done it and said it was fine.

 

well **** i guess ill be looking for another a6