Vince99FRC

This question was asked of me today and I had no clue. I wonder what a 9.5:1 compression 408ci car would do with this blower? The person tried to tell me it would work on my car with straight 100 octane. I think that would be asking a bit too much. LOL!!!

Chris@East Coast Supercharging

I have not personaly tried a mag with that many cubes but I think you would have a hard time keeping the cylinders full. I think the biggest I would try would be a tight 383 with a smaller cam.

Vince99FRC

Hmmmm. I guess a bigger root style blower would be best?

BlackMagicC5

How about the kenne belle?

Automag928

Vince, just leave it alone man... You car is plenty fast!

STAGED

If the heads are up to par, you're at sea-level, I think 408cid and a 2.8" upper pullied Mag will net 5.5 psi non-intercooled or ~4.75 to 5 psi with intercooler. With 5.5 psi, you have to keep compression at least 10.1:1 non-intercooled at the minimum or at least 10.6:1 at 4.75 psi with intercooler. This assumes your CR calculations are correct and your heads are CNC ported such that each chamber is within a fraction of a cc from each other. Don't let the low boost throw you off, that actually means less resistance and parastic losses to turn the blower FOR GIVEN VOLUMETRIC FLOW RATE.

The higher IC'd Mag + H+Cam posted was 53x rwhp. If you keep compression high enough you should gain a whole lot just on cubes/geometry alone not to mention lower boost means less blower drive losses for given airflow delivered. And torque from idle to 4000 rpms due to aggressive blower drive ratios, cubes, and high compression ratio will be sick.

vettewreck

with that motor you need to spin the hell out of the Mag. You will have no option but to get the IC mag b/c of the AITs. You will probably need a 2.7 or a 2.8 pulley. Id also run an alky inj. kit. I think it would be ok but you will have to spin the crap out of the Mag. The Mag was tested to 18,000rpms so even with the 2.7 pulley you are way under the rpm limit.

AVB

The word for the day is "Potential"

There are some of us.. myself being one, that aren't too thrilled at having anything maxed out (overspinning it). The mag is great on stock bottoms and staying there. I'm assuming this is a built 408 and since you've invested in that, I would think you would want to reach it's potential.

Vince99FRC

I agree with all of you. I will figure it out eventually. I am just taking suggestions right now..

STAGED

If you want me to benchrace your setup that's currently doing 555 rwhp/520 lb.ft., I estimate with:

1.) 2.8" upper pulley
2.) 4.75 psi boost with Mag. intercooled pkg.
3.) 10.6:1 CR
4.) 408cid
5.) milder cam but still appropriate for an F.I. 408

Bench raced expectation: 600 rwhp (45 rwhp gain) but 635 lb.ft. torque (+115 lb.ft. torque) plus you'll pick up lots of refinement with a blower grind cam. This all assumes mechanically sound, proper tuning, proper blower cam, etc.

As I said earlier, higher 346cid Mag+H&C I saw was 53x rwhp.

STAGED

If the car ends up gettin 635 lb.ft. at the wheels peak, you can bet based on the flat Mag. torque curve that you'd be making 550+ lb.ft. (640 lb.ft.+ flywheel, far more than a stock or slightly modded Cummins turbodiesel at the same rpms) from 1500 rpms; that's what 400+cid and PD boost does. It'd be interesting to instantly liquify the tires on a cold winter asphalt surface in 3rd gear from 1500 rpms.

mdhmi

Don't be a wuss. Add an F1C to your 408 and be done with it. :-).

Cheers,

Mark

Vince99FRC

You guys are terrible.. A blower would be nice, but I would be running race gas all the time..

DOUG @ ECS

No you wouldn't Vince,
Not if it built correctly, heck even if it's not add an alky kit, you would be amazed at what it lets you get away with. (at least I was)

Vince99FRC

Let's see here.. My current compression is 11.75 to 1. I am keeping my heads, so I will need to change pistons. No way a blower will work with what I have now w/out the proper fuel. Alchy would help, but I would need it all the time. You guys are talking about running less than 18 degree's of timing just for mid to low 600rwhp.. I make more than that now on my first stage of nitrous. If you are going to sell me on going boost you have to do better than that

DOUG @ ECS

Oh, o.k. nearly 12:1 does changes things a bit
I thought you were looking to be 9.5:1 sorry

Vince99FRC

In the future I am going to drop my compression to something around there 9.1:1 to 9.5:1.

auctiondepot

I have to agree with your statement
"I think that would be asking a bit too much"

The power created from a Roots Blower (positive displacement) is relative to RPM and Size, the displacement of the engine is not particularly relevant, LET ME SAY THAT AGAIN, the size of the engine is not relevant for the potential power with a positive displacement Blower.

This is what a positive displacement blower does; it fixes the MAF (Mass Air Flow) relative to RPM. So no mater what displacement you put behind the Blower you can only make combustion with the same fixed amount of MAF.

An intercooler does not create additional potential power; it is a detonation provention device. It is a power draw not a power adder. It is also a flow restriction and manifests in higher manifold pressure for a given rpm. There are some EPA considerations when cooling the manifold also.

People have install the MP112 on big blocks and seen exactly the same power potential as on a small block.

I saw a dyno here a few weeks ago which illustrates that between a 3.5 and 2.8 inch pulley the 20% increased RPM of the blower creates a relative power increase at below 4000 engine RPM but almost no increase at above 6000RPM. At a blower speed of 15000RPM the power draw is about equal to the power created from the additional MAF.

http://forums.corvetteforum.com/showthread.php?t=974711

The guy usually wins the day with the biggest blower not the biggest block.

But then again I could be wrong.

STAGED

Bigger cubes --> lower boost for given blower speed -->

--> less resistance to turn the blower for given blower rpms --> less drive losses from pumping air in

and...

--> more compression ratio allowed --> greater amount of torque extracted for given charge thanks to greater efficiency associated with higher CR

Also IC'ing allows for more CR and/or timing advance.

A large centrifugal mechanical SC or well-sized turbos seem fit to fill the 408 past 4k rpms (that's why I estimated huge torque gains). A Mag. will have no issues filling a 408cid below 4k rpms but above it I estimated minimal gains (~40-50 hp peak gain).

Edit: If going Mag. with a 408cid, I won't go 9.1:1 to 9.5:1 CR with just 4.75 psi as it would make no more hp than a 10.5:1 CR 346cid LS6

Vince99FRC

Are you sure about that? I think if I dropped my compression down to 9.1:1 my car would make between 470rwhp and 490rwhp. Unless you go ***** to the wall with the 346ci you will not see those numbers. So, how will they make the same horsepower? Are you talking about making the same horsepower gains or the horsepower will be exactly the same?