Anyone know what the boost is for the diff pully sizes on a M90? And is the M112 capable of bolting to a L67 and if so what are the boost levels for those pullys? Just trying to figure out the build I will do. Cant touch my engine for another 30k miles but I can at least start to get ready.

 

boost will vary depending on various other mods (i explain below), i am at 14-15 pounds (mods are listed in my garage if you're curious).


for example
the s/c will push the same amount of air with the same size pulley on 2 very different builds

build 1
3.4 pulley
stock heads
stock blower
stock lower intake
stock rockers
stock cam
headers

build 2
3.4 pulley
stage 4 heads
stock blower
ported lower intake
stock rockers
stock cam
headers


in this situation the s/c will push the same amount of air through on both engines (assuming a good seal in the s/c), but engine 2 will flow through much easier making less pressure in the lower intake, creating less draw from the s/c and far less heat, engine 2 will make far more power but have less boost, change any one of those variables plus a few others and boost levels will change, basically what you want to work toward is lowering the boost while using a pulley size.

basically 2 different l67's with the same blower/throttlebody/pulley will make different boost levels, generally the one with the lower boost makes more power because that engine flows better

which means my being at 14-15 pounds is a BAD thing, i need ported heads pretty badly, which will lower my boost and make way more power

 

So it works diff then a turbo?

 

Like on a tuner car a set size turbo will push 16 psi boost. Im looking for like a 3.6 will push 12 psi, 3.5 13psi, 3.4 14 psi, ect. my goal is around 18 psi. I looked at other superchargers but I cant seem to find many for the l67. mp112 I saw could fit but it would have same parasitic effect as our m90 or more. the tvst R1900 is basically equivalent to our m90 but cant find that either. novi, and procharger I have seen but cant find what supercharger to use and there doesn't seem to be anywhere that compares the parasitic effects and heat generated from them to use as a comparison. I did see that the TVST R1900 is less parasitic and creates less heat but eaton does not sell them directly and magnuson is the only place I found it. I was thinking a 2.8 pulley would get me the 18 psi I wanted but needed to make sure. I know getting it to breath more reduces the back pressure the supercharge fights with but I didnt think that had to do with the psi boost numbers.

 

why do you want to run 18psi? whats your hp goal?

 

18psi is a crap ton of boost..... im making 384whp on 13psi boost on turbo monte..... hopefully this winter i will upgrade my turbo for more volume not pressure. right now my turbo is capable of making 20psi but the air mass is just not there so i need a bigger turbo to have more air volume not more pressure..... hope this helps you out a little

 

i like all that i'm reading

 

Though i dont own an L67 im glad i read this, i was always under the impressino that more boost ment more power.

 

To sum up what 2003l67ss is saying is you need support mods to drop a pully size

if you where to jump strait from a stock pully to a 2.8 you may as well kiss your motor good bye unless you get it tuned but then they weill just be pulling a ton of timing and adding a ton of fuel to combat the KR

support mods are more important than a pully

 

I know this much. I know all about the supporting mods. On a turbo you buy it and set it for a psi boost level. What I am asking about is the pulley size I would need for the 18 psi goal. I would have all supporting mods I am going to build the engine from the bottom up out of a bare block. The horespower number I am not real sure I am just going to build what I got in my head and see if I am happy with the numbers.