what would happen if i turned the hf motor int o dpfi? i have an hfmotor & i want to put into a dx since the engine blew. Would it run ok? I could switch the dx to mpfi but if i dont have to i wont? any input? If i keep it HF motor MPFI can i put a SI im &TB or will that hurt ts reliability?


Modified by LEGUTKI at 9:50 AM 6/1/2004


Modified by LEGUTKI at 9:50 AM 6/1/2004

 

no problem - just use the DX intake manifold, the DX wiring harness, the DX exhaust manifold and the DX distributor

 

would it live up to its 62hpp potential?

 

I would say that it might actually put out a little more power than that since the hf intake manifold is very restrictive and I think the dx manifold might be a little bigger overall..

 

add the dx ecu to jlicrx's list. you prob dont have to replace the exhaust manifold, but it might be a good idea.

the only problem i see with dropping the dx engine, is the wiring to the intake manifold. if you can figure out the wiring(or replace the whole harness like jlicrx suggests) i say go for it. http://www.fourthgenhatch.com/mpfi.html -- that link has a great comparison of the dpfi and mpfi wiring differences.

another option you might be able to do is just swap the engine minus the intake manifold. slap the hf manifold onto the dx engine. then you can keep the hf ecu, dizzy, etc.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tilt &raquo;</TD></TR><TR><TD CLASS="quote">add the dx ecu to jlicrx's list. you prob dont have to replace the exhaust manifold, but it might be a good idea.

the only problem i see with dropping the dx engine, is the wiring to the intake manifold. if you can figure out the wiring(or replace the whole harness like jlicrx suggests) i say go for it. http://www.fourthgenhatch.com/mpfi.html -- that link has a great comparison of the dpfi and mpfi wiring differences.

another option you might be able to do is just swap the engine minus the intake manifold. slap the hf manifold onto the dx engine. then you can keep the hf ecu, dizzy, etc.</TD></TR></TABLE>

I think hes going the other way here.. Putting a hf motor into a dx car.. No need to change the harness.. Just bolt on the dx one and go..

 

Thanks guys thats what i was hoping to hear If anybody has any input on if the hp would be hurt let me know because i dont think i could sacrifice to much of that 62hp

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tilt &raquo;</TD></TR><TR><TD CLASS="quote">add the dx ecu to jlicrx's list. you prob dont have to replace the exhaust manifold, but it might be a good idea.
</TD></TR></TABLE>

you will need to swap exhaust manifolds - the HF uses a close coupled cat and different downpipe than the DX

the only reason i mentioned the DX harness was that some people try to use the harness that is on the engine they are putting in

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jlicrx &raquo;</TD></TR><TR><TD CLASS="quote">

the only reason i mentioned the DX harness was that some people try to use the harness that is on the engine they are putting in </TD></TR></TABLE>

Ahhh.. Didnt think of it that way..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by legutki &raquo;</TD></TR><TR><TD CLASS="quote">what would happen if i turned the hf motor int o dpfi? i have an hfmotor & i want to put into a dx since the engine blew. Would it run ok? I could switch the dx to mpfi but if i dont have to i wont? any input?</TD></TR></TABLE>

I don't think that the HF is going to make its stock rated 62hp setup this way. Remember that the HF is an 8 valve motor, and its not like the valves are any bigger really, it uses the same head casting as the dx or si motor. My guess is its going to run lean below 3k and rich above 4k. If this is just a temp thing, go for it, otherwise, just find yourself an Si motor and do a MPFI swap, you'll be much happier!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bunger &raquo;</TD></TR><TR><TD CLASS="quote">

I don't think that the HF is going to make its stock rated 62hp setup this way. Remember that the HF is an 8 valve motor, and its not like the valves are any bigger really, it uses the same head casting as the dx or si motor. My guess is its going to run lean below 3k and rich above 4k. If this is just a temp thing, go for it, otherwise, just find yourself an Si motor and do a MPFI swap, you'll be much happier!</TD></TR></TABLE>

My thinking was that the dx intake manifold flowed a little better than the hf manifold so there would be a power increase.. Its probably minimal +/- 1-2hp either way..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tgreaves &raquo;</TD></TR><TR><TD CLASS="quote">My thinking was that the dx intake manifold flowed a little better than the hf manifold so there would be a power increase.. Its probably minimal +/- 1-2hp either way..</TD></TR></TABLE>

I can see where you're coming from, but unless you took the time to tune it, its not going to have the right A/F ratio, if hondas were MAF instead of MAP, there wouldn't be as much of an issue.

On a side note, I don't know how well that HF head is going to like being revved much past 5.5K... my guess is that those valve springs aren't too stiff.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bunger &raquo;</TD></TR><TR><TD CLASS="quote">

I can see where you're coming from, but unless you took the time to tune it, its not going to have the right A/F ratio, if hondas were MAF instead of MAP, there wouldn't be as much of an issue.

On a side note, I don't know how well that HF head is going to like being revved much past 5.5K... my guess is that those valve springs aren't too stiff.</TD></TR></TABLE>

Correct.. The air/fuel ratio will be off under open loop operation.. Not sure on the valve springs, I dont work with hf heads.. Just to be safe I would keep the rpm's at the stock rev-limit.. I know the pistons and rods can go up to 6800 but i doubt the springs can..

 

Well i guess ill change it to mpfi because i will be using it as my daily driver and using to drive back and forth home to fl (2000) mile round trip & since gas prices are rising ill probably keep it for a while. because it sounds like you guys dont think its too reliable if i change it to dpfi

 

Well the problem is your using an ecu that is tuned for a dpfi manifold on a 16 valve head.. Your wanting to use a dpfi manifold on a 8 valve head.. I would just convert it over to mpfi and run it just like a normal hf crx would be ran.. Get the pm8 ecu for it and your good to go..

 

well i alraedy have the pm8 i have an crx hf but i put a b18c swap in there so i have the complete hf swap over and i just bought this dx with a blown motor. so i bought it so my crx can stay in the garage. i was thinking that the dx ecu could just adjust itself to the right timing so it wouldnt be to lean or rich any thoughts on that?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by legutki &raquo;</TD></TR><TR><TD CLASS="quote">well i alraedy have the pm8 i have an crx hf but i put a b18c swap in there so i have the complete hf swap over and i just bought this dx with a blown motor. so i bought it so my crx can stay in the garage. i was thinking that the dx ecu could just adjust itself to the right timing so it wouldnt be to lean or rich any thoughts on that?</TD></TR></TABLE>

Under closed loop operation the ecu will adjust the air/fuel for stoic. but under open loop it will go with whats on the map which will not be correct.. If its just for now and you dont care about the motor I would say just go ahead and try it with the dx manifold and pm5 ecu..

 

Thanks for all your help i learned alot from your post and from what you told me ill just switch it to mpfi because i want the engine to last

 

Glad to help out..

 

yeah my buddy just did the whole HF-to-DX swap in his 90 used his DX mani and **** had everything in for about 2 months and the motor blew....my opinion just drop a Si motor in it and switch to MPFI.....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EF9Dreams &raquo;</TD></TR><TR><TD CLASS="quote">yeah my buddy just did the whole HF-to-DX swap in his 90 used his DX mani and **** had everything in for about 2 months and the motor blew....my opinion just drop a Si motor in it and switch to MPFI..... </TD></TR></TABLE>

True.. But I think hes going for the gas mileage on this one..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tgreaves &raquo;</TD></TR><TR><TD CLASS="quote">

True.. But I think hes going for the gas mileage on this one..</TD></TR></TABLE>

i'd rather waste the gas and be able to pass someone on a 2 lane road then save gas and be stuck behind idiots that drive to slow lol

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EF9Dreams &raquo;</TD></TR><TR><TD CLASS="quote">

i'd rather waste the gas and be able to pass someone on a 2 lane road then save gas and be stuck behind idiots that drive to slow lol</TD></TR></TABLE>

thats is what the JRSC b18c CRX is for in the garage

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EF9Dreams &raquo;</TD></TR><TR><TD CLASS="quote">

i'd rather waste the gas and be able to pass someone on a 2 lane road then save gas and be stuck behind idiots that drive to slow lol</TD></TR></TABLE>

I didnt say that I agreed with this.. Just that this is what hes going for..

 

Can i put a crx si IM and TB on there to give it a little more HP or will that hurt its reliability?