pulley fitment question!!!

[shinsonater]

I was wondering if the underdrive pulley from sohc is interchangeable with that of the dohc

[Ryan]

If I were you, I'd stay away from UDP's. There are a few reasons why...

If the belts are the same type (both serp) it will exchange.

[Limegreen mx-3]

I was wondering if the underdrive pulley from sohc is interchangeable with that of the dohc

Yes they are the same for the sohc and dohc.

are u looking for a OEM replacement or aftermarket replacement

[shinsonater]

aftermarket i plan on keeping my sohc but the pulleys online are only for dohc.

[Limegreen mx-3]

aftermarket i plan on keeping my sohc but the pulleys online are only for dohc.

they will work on a sohc and u will need to replace both belts of a smaller size. You won't notice any difference in a power gain..

[MapaX5]

Sorry to correct yall in here. but they are NOT interchangeable.
92 SOHC uses a V-belt design, while the DOHC uses a cerpentine belt.
Now, this is an easy fix.
You want to get a WATER PUMP pulley off a DOHC AND an alternator.
while you're are it, get a V6 alty and you should be good for an extra 40amps of power.
Now, the problem with UD pulleys is: NOT GOOD FOR FI! no turbos if you're going this route.
the OEM is not just a pulley, it's actually called a harmonic balancer, which is designed to get rid of the vibration generated by the crank.
Now, if you want a quick revving NA, this is the way to go. because of taking off about a lb of rotating mass off the engine can help the engine rev quicker. hence the use of lightened flywheels and a lighter aftermarket clutch with a different disc material.
You will feel a difference, not in power but in your throtle responce. your butt-dyno will lie to you. all it's doing is letting the engine rev quicker and thus reach your powerband quicker as well.
if you really wanna feel a difference, get headers/intake/UD all at once.
the extra torque/hp from the headers and intake will improve your engine breathing while the UD will let it rev quicker...and bam! lol.

[MapaX5]

if you really wanna get into it, get a set of IRTBs for your car, megasquirt, UD and a FW/clutch combo and prepare for a NASTY lil ride.
i've driven a miata with this setup (before and after) and you'd think it was a different car!

[Evo_Spec]

now you mentioned something about a harmonic balancer, could you explain more about that?
i've read in some places that UDP's do something and sometimes they blow up or something? they cause something to happen, i don't remember, if you know what i'm talking about and fill me in that would be awesome

[MapaX5]

sure.
here's a quick overview...
"A harmonic balancer (also called crank pulley damper, crankshaft damper, torsional damper, or vibration damper) is a device connected to the crankshaft of an engine to reduce torsional vibration and serves as a pulley for drive belts.
Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure.
To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft. The damper is composed of two elements: a mass and an energy dissipating element. The mass resists the acceleration of the vibration and the energy dissipating (rubber/clutch/fluid) element absorbs the vibrations."
ok, now, what this means...
it's like balancing your tires. if you don't, the UN-EVEN rotating mass creates vibrations that could destroy your crankshaft.
a lot of people stay away from UDs because of this. high-powered vehicles use an actual underdrive pulley that is made SPECIFICALLY for their vehicle. you're looking at a $500 part, but they warrant the vehicle's crank will not fail.

[MapaX5]

if you look at a stock unit, they are not just solid steel...although they look like it, if you look carefully, there is rubber in there, that rubber creates the dampening part, and allows the vibrations to be reduced. this is also has its weigh balanced out to counter the engine's specific resoinance. that is why you shouldn't use a pulley off another motor (say, a hon-duh motor on a mazda or V-V) because they are designed for the specific vibration at a specifi rpm range.
you CAN use one, but the major problems i've heard were oil-pump failure, not so much a crank shaft.
you should get a BRAND NAME unit, not one that is made in someone's back yard.
an Unorthodox pulley goes through some testing to make sure it is RELATIVELY safe for your engine, while the best your local machine shop can do is make sure it's even.
you also don't want to go too small with this, as the smaller circumference makes the accessories rotate at a slower rate. meaning, your water pump will not spin as fast, thus decreasing the flow. same with the alternator. it will spin less than necessary to achieve the necessary charging amps and this could be detrimental for your car.
the 12v needs to be constant on a car (for the sensors) because the ECU measures the difference between 12/5 v and ground.
less volts also mean less power to the primary coil and thus less spark.
that's why i suggested a v6 alty, which gives off 90amps instead of the wimpy 60 off the i4

[Limegreen mx-3]

Sorry to correct yall in here. but they are NOT interchangeable.
92 SOHC uses a V-belt design, while the DOHC uses a cerpentine belt.
.

I have a 1.6 sohc and i don't see how it ever had a v-belt design unless ur mistaking it for a bp underdrive pulley

[Evo_Spec]

thank you very much for that detailed explaination, i generally understand now

[MapaX5]

Sorry to correct yall in here. but they are NOT interchangeable.
92 SOHC uses a V-belt design, while the DOHC uses a cerpentine belt.
.

I have a 1.6 sohc and i don't see how it ever had a v-belt design unless ur mistaking it for a bp underdrive pulley

the 94 uses a Poly-v belt, which is a flat belt that has 4 grooves in it, part number 4040350
while the 92-93 use a V belt, which is just a different kind of belt. i'll see if i can take a pic of the pulley to show you.
How do i post pics in here again?
Now, you are correct on one part. the 94+ pulleys DO resemble the BP ones. in fact, when i got my UD for my '94 mx-3 i got one off a '93 DOHC protege.

[MapaX5]

thank you very much for that detailed explaination, i generally understand now

hey, no problem. that's wat we're here for