Boosting Question

[Lilchief]

My question is concerning a supercharger. For instance a M90 with a 3" pulley yeilds 12 lbs boost on a 3.8. Now if I was to put this on a 2.8 would I get more boost or stay the same and why?

[ForcedFirebird]

It depends on the crank to pulley ratio. Look at compressor maps for an M90 and calculate the speed of the rotor to see hwta kind of air it's going to move.

[Joseph Upson]

It depends on the crank to pulley ratio. Look at compressor maps for an M90 and calculate the speed of the rotor to see hwta kind of air it's going to move.

When are you going to focus on your swap and finish it so I can hear it run? and copy it when I finally get around to installing my cammed 3500 into my cousins light weight courier S10 Blazer. I'm itching to finally get back so I can make the necessary corrections and test drive my hopefully sleeping giant.

Theoretically at the same rpm and pulley ratios his boost level should be higher on the smaller engine as you alluded to, since the displacement to boost level ratio decreased, in other words forcing the same quantity of air into a smaller space. In proper perspective he would actually end up with more potential since if there is a wastegate involved it's going to open at the same boost level setting which can be increased, provided that's how the SC works to help limit pressure.

[ForcedFirebird]

When are you going to focus on your swap and finish it so I can hear it run? and copy it when I finally get around to installing my cammed 3500 into my cousins light weight courier S10 Blazer. I'm itching to finally get back so I can make the necessary corrections and test drive my hopefully sleeping giant.

I would love to focus on my priorities, but when you have four kids and responsibilities, my priorities may not always be the best for the family.

The 3500 swap won't happen for a while, but a cam is holding me back at the moment. Then the next major item is the headers, but they won't take more than a couple of days. You are going to have a more difficult time putting the 3500 in a s-body than an fbody.

As you may know, a friend and I are starting a CNC machine shop. Between getting that going, my contracting company, and the family - time is most precious right now.

Besides, I'm planning on copying some of Dave's modifications to help speed the process up


I also am anxious to see the 3900TT running!

Theoretically at the same rpm and pulley ratios his boost level should be higher on the smaller engine as you alluded to, since the displacement to boost level ratio decreased, in other words forcing the same quantity of air into a smaller space. In proper perspective he would actually end up with more potential since if there is a wastegate involved it's going to open at the same boost level setting which can be increased, provided that's how the SC works to help limit pressure.

I was going to get into that, but was kind of feeling out the original poster (just in case you didn't notice the typos in the quick response, lol).

[Joseph Upson]

You are going to have a more difficult time putting the 3500 in a s-body than an fbody.

Actually I was thinking it will not be to difficult a problem as long as I can turn the lower intake manifold around so that the coolant exits out the front of the engine and use the old 2.8 timing cover the way I did on the 3100 block. I have a plasma cutter so I should be able to work around the mount pad difference issue to secure it properly. The truck is a bare hauler with no extras including A/C and anti-lock so there will be plenty of room for turbos and the needed air cooling accessories. I plan to have the turbos stick up slightly above the hood, and expect it to take about a week to finish, but it will a good while before it ever happens.

XS Power has a nice little direct site with some outstanding turbo prices and pre fabbed turbo exhaust headers for select cars, including the V6 Honda I drive and 3 different versions for the small block chevy at less than $200 a set so that all you have to do is mount the turbo and wastegate and finish the exhaust, WOW! Take a look;

http://xs-power.com/turbos.htm

[ForcedFirebird]

I'm very fimiliar with XSPower. I bought all my turbo parts from them for my first turbo kit (to4e, WG, BOV, boost controler etc). Everything worked flawlessly, but the turbo is/was advertised at a 57 trim and I measured it at a 46 after it was here. For $175 delivered I wasn't going to complain. In fact I may buy another and do a TT on the hybrid after changing the pistons to 3400 units after N/A testing is done.

I made my own pipes, the XS pipes are thin and I believe they are 304 SS. Many people have had sucess with them after modifying them for strength.

I would have turbo'd right away, but I'm curious to see what kind of numbers the N/A 3.4/3500 with 12.33 compression is capable of.

Side note: Thanks for suggesting for Loner to come down and have me help with his turbo.

[loner666]

Side note: Thanks for suggesting for Loner to come down and have me help with his turbo.

that was interesting wasnt it? lol..because of you i cant keep a damn trans..fired the first one now the one i just put in has no 3rd gear. I need that gear for highway fun!

[IsaacHayes]

loner: Didn't 3400-modified have a write up on when he rebuilt his trans? Either that or 5speed and be done with it.

Re topic: Also if your motor is more restricted than the 3800 then you could get boost stacking. Open up the motor and you have less PSI building up because you are moving more air.

[ForcedFirebird]

that was interesting wasnt it? lol..because of you i cant keep a damn trans..fired the first one now the one i just put in has no 3rd gear. I need that gear for highway fun!

Man, what a shame - we made your car too powerful to keep a tranny behind it

[Lilchief]

OK another boosting question since your keeping it active. Is the M90 a 90 cu. in. SC? If this is true is there a sizing formula for engine size? Would a 117 cu. in. SC be too big for a 3500/3900 ?