MODIFICATION , ENGINE COOLING PART 1 ( Intake Coolant Bypass )

[A20A1]

carb

here is the way i bypassed the intake manifold heater.
The efi and carb engines have simmilar coolant ports in about the same area. You will find all needed ports on both water pipes and thermostat housings.

differences:
A20a3
- has the temperature guage sending unit on the thermostat.
- has 2 thermovalve valve/sensor ports
a20a1
- has the temperature guage sending unit on the intake manifold.
- has 1 thermo valve port
anyways:
R1 - goes to the radiator.
R2 - goes to the radiator.
T1 - is the temperature sending unit.
C1 - connects to c2 directly or with a coolant "t" connector if it is used by the heater core.
B1 & even b2 can be plugged if you don't want to use the heater core.
There is a small coolant port near the center of the water pipe that runs under the intake manifold and feeds the carburetor base... When removing the coolant lines to the manifold you need to plug the small coolant port on the water pipe... Also plug the larger coolant port on the water pipe that is closest to the water pump. You bypass the manifold by running a short hose looped from c1 to c2 , although you can run a much longer hose from the port near the water pump... All the way to the port on the thermostat housing and it will do the same job.
The choke on the carb will need some vacuum rerouting to work. You need to relocate the thermovalve b (vacuum lines # 17,18,19) to the thermostat housing... And remove the thermowax valve a. With the thermowax removed you must connect a vacuum hose from the secondary diaphragm directly to the carb and remove the vacuum "t" connector or plug all ports and convert to manual secondary.
If you get the lxi thermostat housing then you can also swap in thermovalve a (vacuum lines # 17, 25) that controll the cold vacuum advance... You'll also have a working temperature guage inside the car since the temp sensor is now on the thermostat housing and has access to coolant

efi

this thread is based on this prelude free mods page describing free or dirt cheap mods. I found it referenced on a prelude forum (can't find link right now) where they agreed that some of them worked and were worthwhile (coolant bypass, egr block, ignition timing advance etc.) and some weren't worth it (flapper valve mod-caused loss of lower end power).
Egr mod has a thread: block the egr ignition timing advance has been discussed here quite a few times, though i still don't exactly get which screws i need to loosen. I will be referencing only the coolant bypass mod in this thread and intend to post pictures and make it into a well rounded how to.
Coolant bypass mod consists of two parts (at least on a prelude). The first is bypassing the coolant flowing through the throttle body.
The second is blocking the fast idle valve. Though the fore mentioned mod page doesn't mention it, it has been noted on the prelude forum that bypassing the coolant results in rough idle which is reportedly fixed by blocking the fast idle valve. I don't know yet if it will have the same effect on a 3g, but my fast idle valve was idling the car at 2200 rpm when cold so i wanted to block it anyway.
bypassing the coolant line through the throttle body is a simple process of disconnecting the hoses that run from the water pump to the throttle body and from the throttle body back to the engine (actually to a t or rather +connector) at the ends where they connect to the throttle body and connecting the two hoses to each other.
replacing the two hoses with one longer one was not an option to me as the water pump side was highly inaccessible. If you know of a simple way to do it, please let me know.
The problem i ran into was finding a 5/16 hose connector. I looked at 11 stores, all major auto parts stores and some local ones, the home depot as well as local hardware stores. The only 5/16 connector i found was in a $4.00 asorted vacuum connector kit at auto zone. can someone advise me if it is ok to use a vacuum hose connector on a water (coolant) hose?
i'm running late right now, but i will update this thread at a latter time with instructions and pics of fast idle valve block which i achieved successfully. I just wanted to get this thread started. I would like to make it into a well rounded how to.

[shepherd79]

wait a minute, where is your heater core?
it looks like you won't have heat in your car.

[A20A1]

yes... I don't need heat or the extra weight in my car.

but...

If you need to keep the heater core because of the cold, it's best to leave on the manifold heater as well till things warm up.

Well then don't remove the heater coolant hoses, other then that follow the diagram.

[shepherd79]

well, i am not going to gut my car like you did.

[POS carb]

oh shit I was going to hack my thermostat to mount the sensor but looks like I can just grab an LXi one then... thakns

[shepherd79]

if you want to keep the heater, you will have to connect the C1 to a black pipe. I just ran the long hose to the other side, where the another pipe was.

[88 Accord DX]

screw this im confused

[POS carb]

lol it would be easier if someone sold plugs

[shepherd79]

you can buy coolant plug at any autoparts store.

[88 Accord DX]

i dont know what im plugging. maybe cuz ive never looked for this part in my car.

[POS carb]

hey something I was interested in is setting up a seperate cooling system on the manifold for the carb people since the carbs run all weird b/c of the changing temps. Maybe something similar to the oil coolers they sell with fans.

[shepherd79]

why would you do that?

[thundertank]

You know it would save alot of hassle if they would have given the accord more than 98 horses!!!

[POS carb]

aak subaru stole my idea (or I subconciously imagined it) only they use it to cool the intercooler (water jets)
I have a waterjet setup intercooler in my garage lol

[sixgears]

I bypassed the intake heater and converted to thw lx-i thermostat housing to relocate my temp guage pickup, but shouldn't the temp/vacuum switch near the brake booster with three ports also be relocated to make a20a1's digram function. it still needs to be in coolant flow, am i right. In a20a1's diagram, it has lines #17,18 and 19 connected to it. thanks.
On a side note, the Kehin will soon be gone and in it's place (or below it) a pair of sidedraft Mikunis.....hehehe

(thermovalve a)

[POS carb]

hey I have a bypass valve installed on the return line from the manifold. I got it at Home Depot. I didn't say anything earlier b/c I wasn't sure it would work but so far so good, it is holding up. It's a brass water valve with a blue lever-style handle. I'll send a pic. I'm also thinking about using a heater core as a manifold water radiator.

[k-roy]

I have a question. What exactly are the benifits and downfalls of bypassing the manifold heater? I live in a warmer climate with mild winters. I would like to know what problems could occur at colder temperatures below 50 degrees. I am always up for bastardizing my car. It allready has parts from 2 dozen differant 3gs.

bump

[POS carb]

the worst that can happen is the fuel doesn't atomize enough and it just gets shot out through your exhaust, kind of like running lean, but once the motor is warming up the carb will be warm enough from the air around it to still work ok. On cold days your car will probably run too lean Kroy. I would try hooking up a valve like I did so you can try it out.

About those thermovalves, if you are one of the few who's choke still works normally I think this mod will cause problems with the choke staying closed and the fast idle staying on. My motor hasn't seen an ECU in a few years so I can't tell you for sure

[A20A1]

Yeah I'm not sure what I did with the choke... It plugs into a different thermal sensor though, right? The one on the intake manifold was for the guage cluster... I think the choke is on the block.

[POS carb]

oooooh, I remember seeing a plug on the back of the block, I was like WTF is that for

[A20A1]

Post your engine cooling modifications
*Serious Mods Only!
*Must Include Pics!

- Dual Radiator Fans

-- Stock radiator fan, operates using toggle switch, hooked to battery.

[A20A1]

My next mod

- Dual Automatic Transmission Coolers
2 B&M Super Coolers

Radiator cooler isn't used.

[bobafett]

mike do you have 2 of the bigger fans? i assume u ditched AC, and the smaller fan.

i am gonna run a switch for my fan too, i like the idea of 2 fans that are bigger though.
is there any way to keep stock functionality AND also give you manual control, or is it EITHER OR?

[A20A1]

well just use the A/C fans wires to operate the larger fan... I'm not sure if the larger fan fits with the A/C compressor there though. You'll need some long zip ties or wire to hold one side of the fan to the radiator since there are not many bolt holes that the larger fan can use.

Use a 3 way switch if you want to have the fan come on automaticly or manually, just use one wire from the thermo switch and one wire from the battery and then they both use the same ground I believe... or the same power wire depending on where the thermoswitch is located within the wiring.

[TWOLOUDNPROUD]

High Valume Trany Cooler need it for my 2900Rpm stall with out it will do this