WHat lower pulley should i go with on a built MP truck?

[MEANSVT]

As the tittle says im already running a 2.75 upper and a 11" lower i want something more street friendly and reliable but still fun so what do you think i should change my lower to? I plan on getting the truck tuned soon by swanson performance. and changing the lower one im down there? what are you daily driven built guys running for boost? Im more about reliablity these days i jus want my truck to work every time i get in and not push the envelope.

 

[FordFanStan]

So you decided not to sell :thumbsup:

How much psi. are you seeing now? It all depends on your engine, but typically I'd recommend a 8lb. lower w/ 3.25" upper or a 6lb. lower w/ a 3" upper, with that type of setup. Good luck with the tune. Let us know how it goes. FFS

 

[hellokitty889]

Thread Guidelines

GOOD Writing! The Combat Formula thread. This is a recreation of the previous combat formula thread. In this thread, we discuss the formula that calculates one's combat level, using the levels in the combat skills. This formula is not exact, but it does have a very high accuracy. Our goal is to improve it so that it becomes exact. The formula runescape gold can help you calculate your combat level, for any combination of combat skills you like. INTERESTING NEWS: Jagex puts up a Wallpaper containing something that appears to be an estimate of the combat formula Runescape money. Our data suggests that it is not the actual formula, but it does seem to confirm bits of our formula. Feel free to discuss it here in this thread Want to buy rs gold pls check it~~keep working!

 

[Dr. Matt]

GOOD Writing! The Combat Formula thread. This is a recreation of the previous combat formula thread. In this thread, we discuss the formula that calculates one's combat level, using the levels in the combat skills. This formula is not exact, but it does have a very high accuracy. Our goal is to improve it so that it becomes exact. The formula runescape gold can help you calculate your combat level, for any combination of combat skills you like. INTERESTING NEWS: Jagex puts up a Wallpaper containing something that appears to be an estimate of the combat formula Runescape money. Our data suggests that it is not the actual formula, but it does seem to confirm bits of our formula. Feel free to discuss it here in this thread Want to buy rs gold pls check it~~keep working!

:wf::cuss:

To the OP:

How much boost are you seeing with what heads/cams? I'm curious myself since I have yet to install my MP. I plan to swap between a 6# and a 10# lower with my 2.76 upper depending on the need/time of year.

Matt

 

[MEANSVT]

So you decided not to sell :thumbsup:

How much psi. are you seeing now? It all depends on your engine, but typically I'd recommend a 8lb. lower w/ 3.25" upper or a 6lb. lower w/ a 3" upper, with that type of setup. Good luck with the tune. Let us know how it goes. FFS

Yeah im keeping it for now it's just to much fun to get rid of it. ive seen around 18 psi on my gauge before but i really dont know cause i have'nt really got on the truck since i bought it cause it needs to be tuned for 91 oct. im told it will hit 22 psi with the 11" lower. But im not concerned with being the fastest i just want it to be reliable and not push the truck to hard. and im not comfortable spinning the blower like that on a truck i daily drive id be happy with around 500 WHP it made 552 WHP at PSP on 93 oct with a #10lower and 2.75 upper. it has never been dynoed with the 11" lower that is currently on the truck. So do you guys think a #8 lower with the 2.75 upper would be ideal for what i want?

 

[Zak Attack]

I would think that the 8lb would be optimum with the 2.7 upper. Thats like a 11lb increase (IIRC) from stock, and you would still get good belt wrap.

 

[FordFanStan]

If you're are seeing 22psi max on that setup, supposedly, and you swap to an 8lb lower, than you should be decreasing max boost by approx 6psi and you should see a nex max of approx 18psi. For a street tune on 91 octane we do not like to recommend that much boost, so I would still either change out a 6lb. lower, or what I would recommend is using the 8lb lower or and swap the upper to a larger. It does not make any sense if you're not trying to squeeze absolutely every last bit of air/boost out of it to use such a small upper. The smaller the upper, the more slip you'll have. I ran a 2.75 upper a long time, with my magnum powers idler brace, and I still had slip at 14psi on my street tune. Change the upper out to a larger upper is my suggestion. Wow did any of that make sense lol? Let me try again haha

All numbers approximate:
11" lower = +14psi *what you have now
10" lower = +10psi
9.5" lower = +8psi
9" lower = +6psi
8.5" lower = +4psi
8" lower = +2psi
7.5 lower = stock

3.5 upper = -4psi
3.25 upper = -2psi
2.93 (3") upper = stock
2.75 upper = +2psi * what you have now

+14 +2 +8stock = 24psi but you are actually seeing 22.5 supposedly

now change out the different combos and see what you come up with, but remember you might see a little less than what in theory it does (ie: 24 = 22.5psi)

+8 +0 (3") +8stock = 16psi or maybe around 15psi

That would be super safe to run on Cali 91 octane with a good tune and you shouldn't have to worry about anything then. It should still have a decent amount of power as well. 22.5psi - 15psi = 7.5psi loss. In theory 7.5psi x 10hp = 75hp loss. 550 -75 = 475on a street tune.

You could also use that same method and try a 10psi lower with a 3" upper, but I wouldn't recommend running over 16-17psi MAX on 91 octane, sure its possible but it isn't the safest thing to run that much pressue on that little of octane even wth the spark set low. Hope that helps some. FFS

 

[MEANSVT]

Thanks stan that was a very helpful post.

 

[Ct.TOPGUN]

Once you have experienced the thrill of low end power with the high pulley ratio it is hard to be happy with less. I run my 2.7 upper and 11" lower combo full time. Mine is a "weekend warrier" and I can get 93 octane pump fuel here. I run 14* timing in the warm weather, 12* in the winter.
For 91 octane fuel I would run the 11" lower and a stock upper(2.92) . For track days you can swap the upper for full boost on race fuel. This will gain the most belt wrap and allow full power when desired. I would create a street tune with 14*-16* timing in the low RPM range, and 12* in the upper ranges. This should allow you to feel good power but be safer from detonation under load (such as a high gear pull).

Jim:coolman:

 

[04troublez]

when you change pullies does your MPG decrease

 

[Zak Attack]

lol wut?

um depends on the tune, driving habits, and if you decide you want to use your new found pulley