warthogdriver

ok first off i have read alot of the threads..even the 30 pager here. all of it is great info and been very helpful. i have my parts list but there are a couple of things i cant find a straight answer on..and maybe there isnt one.

basically this is my starting point.

i want to swap this onto a 99 stock v6, with low miles. i tossed it in when my 95 blew heads...i tore it down and replaced all gaskets and had machine shop check the whole thing over...they gave it a clean bill of health.
it is my daily driver so i am not looking to go crazy fast with it.
with that said i have a couple of questions:

1. how do i determine what pulley i have on an m112?
2. what udp do i need? i have seen 25% and 42% floating around
3. fuel pump svt focus 310 lph...yes / no? i am using the return style fuel system.
4. i have read that 10 psi on stock is "safe" limit, this goes back to the udp size...i would like to stay at or "slightly" below safe limit.
5. heat..is it an issue or not? lots of opinions on that too.

as for my end goals, keep the stock 3.8 till i can save for the 4.2 and forged goodness. it will take me a good couple years (maybe more) to do this at best...so i would like to gather up the m112 parts and use them till then.
also this car is only a summer driver that i put maybe 3000 mi on a year...so i expect it to last me a good while.

any help would be appreciated guys.
jared

jthorn9

You have to measure the pulley diameter. The larger the diameter the lower the PSI/boost. Once you know the size, compare that to aftermarket sizes to see which one it is. There are tons of charts on supercharger sites.

You do not use UDP with S/Cs. They underdrive the S/C lowering boost. I know this first hand as when I put a Kenne Bell on my 5.0 I forgot to remove the U/D pullies and my 11 PSI charger pulled 4/5 PSI. Once I swapped back out to factory I was right at 11 PSI.

Yes the Ford Focus pump is the correct pump. Don't forget to upgrade the fuel injectors too.

10 PSI with the M112 is good for around 7-9 hp per PSI. It's a little on the low side, but that's because the M112 suffers from heat soaking which reduces efficiency. So assuming 10PSI will add, we will call it 80 rwhp to be in the middle, that puts you at around 240 rwhp on an otherwise stock 3.8L. It could be higher, but that's the problem with the M112 and why so many Cobra owners sell it. The efficiency is all over the place due to the heat soaking issue and the natural reduced efficiency of the roots based charger. It's also the reason why so many V6 owners dump their M112 projects as the payoff vs time put in and money usually isn't worth it. The factory "safe limit" for the essex 3.8L is 300-350 hp.

As stated, the heat isn't an opinion, it's a fact, the M112s are a roots based charger and even with the heat exchanger, they suffer heat soaking which reduces efficiency of the S/C. It won't hurt the motor or the S/C in any way (unless it over heats through acts of God) but it does lower the efficiency. That's why when you compare a stock 03/04 Cobra with a M112 at 9-11 PSI to a 5 PSI twin screw supercharger, the twin screw makes the same to slightly more power than the roots based M112 due to the improved design and efficiency with heat discharge.

Remember hot air lowers air density, the less dense the air, the lower the hp number. That's why cars "seem" faster in the winter than in the summer. Winter brings denser cooler air and greater engine operating efficiency.

warthogdriver

thank you for the info.
for injectors i am thinking 39# seems to be the most commonly used.

i will look for the charts you mentioned. it seems that 42% Underdrive crank pulley is the ticket.

i am not sure where to measure the S/C pulley but from the outermost lip its dia. is roughly 3 7/8"

heat is an issue but not a damaging one..i live in michigan so its not all that hot most of the time. i have looked at meth kits...which is on my reading list. yeah i figured it would be similar to the purpose of the cold air intake...cool air is our friend.

thanks again for the time....i hate asking questions that are all over but sometimes you have to in order to sort the good answers out.

NYstang

J, Im going to correct you here since you arent familiar with the M112/3.8 combo.



You will WANT to underdrive the blower, as with the stock balancer pulley you will end up with 14psi, which is way more than you will want. these blowers work more than efficiantly at 7-8psi on the 3.8. Most actually see a boost in power.

With a 25% UDP and stock upper, expect around 7psi, give or take one.


Warty,

can you go over your driveline/fuel setup? Im confused as to if this is a 99 or 95. That changes a few things.

warthogdriver

its a 95 return style fuel setup. i modified the 99 rail to work.
so whole car is 95 except the motor...its 99 with the 99 injectors currently.

why not 42% pulley? i am new to this so the how and why of the math is all new to me.

this pulley?

http://www.americanmuscle.com/bbk-v6-9498-udp.html

http://shop.macperformance.com/MAC-F...lleys-3898.htm

i know i need a 94-98 balancer to make it work. seems there is no 99-00 udp


thanks for the help guys.

NYstang

stangsuspension.com carries a 99-00 pulley. a 94-98 pulley will NOT work.

you will also need a different fuel pump- i believe its a walbro 290lph pump for your system.

39ln injectors will work though.

warthogdriver

thank you for the link....now that is why i am glad i started this thread...i read several that said to swap to a 94-98 balancer to get to the udp pulley.
probably save me headaches for sure.

290 on the pump..ok
is that because the 310 wont work with my system?

NYstang

correct, its for a returnless fuel system. wont work with the return style tank that you have.

warthogdriver

Saved me again.
Thank you...i will have to put all this together in notes.

warthogdriver

if 94-98 are external balanced and my 99 is external balance couldnt i use a 94-98 harmonic balancer then get the 94-98 UDP. i know the bolt pattern is diff on the 99-00 but if both are external balance would it matter?
its a big detail seeing as how the 99-00 UDP is 250.00 and the 94-98 is 90 +/-