Ok, so i reckon you guys might have some good feedback.

I have a 408(scat stroked 351c) supercharged to 4psi with an eaton M112 blower, in my 84 bronco.

its on straight LPG (propane to u yanks ), fed by 2 x GRA 400 CFM carbies.

and im thinking nitrous. after researching nitrous oxide, it seems to be a match made in heaven. i have a spacious post-boost intake manifold, just achng for some nitrous foggers/injectors. will it work? will it have to be a 'dry' system?

my engine's internals are pretty strong. Scat rods & crank, probe pistons, 8.5:1 comp, solid lifters, alloy 2v AFR heads.. all with less than 5k on the engine.
(engine link http://www.airflowdynamics.com.au/Pr...ngine_408c.htm )

- Sean

 

Why not just up the boost?

 

+ 1 on that.
I would just up the boost to 8 or 10 PSI.
But if you get a nitrous kit it's best to run a wet kit. and make sure your fuel pump or pumps is up to handle the extra HP.

 

I agree on turning the boost up as well, if you have the fuel system to support it. You've got the right compression ratio for it and a good air charge cooler (LPG).

 

I'd love to up the boost...
however I like my engine reliable, and low boost & low comp is very good for this... that and the eaton M112 is redlining at 4psi when my truck does 4500rpm, so it would require another, larger, supercharger... and eaton doesnt make them any bigger :/

the truck storms around the roads really well, and I cannot fault it, however if I ever see that AMG suv again I'd like to give it a surprise, nitrous style...
thought I'm wondering which would be cheaper/wiser.. complete nitrous kit, installed... or 4.11 gears.

-Sean

 

I gotta say that is the most original and cool looking set up I have ever seen..Nice work!
Stock Lightning comes with a M112 and 8# of boost from the factory. Guys on the Lightning site are running them a 15 PSI.
I used to run a M90 at 10 &1/2 PSI
With your low compression you would have no problems running more boost.
If your trying to decide on gears or nitrous. With the gears you'll have the extra power all the time.With the nitrous you have to keep filling the bottle.

 

Thanks Phil6608, i really appreciate the kudos

this is the technical stuff, which will explain why i cant run more boost on this charger;
the M112 unit I have redlines at 12,000rpm, I am running a 2.6 inch charger pulley and a 6 inch crank pulley, (which gives 2.3:1 ratio, for every 1 rotation of the crank, the supercharger rotates 2.3 times)
the charger puts out 1.84 litres of air each rotation... (maths maths calculations) *whazzam* this all means at 4500 engine rpm (my rev limiter) my M112 is doing 10384 rpm (close enough to redline for me)
.: running higher boosts means breaching my chargers redline, thus my desire for nitrous.. and/or lower gear ratio.
but I'll be damned if 4.11 x 2 (4wd) isnt expensive over here in Australia

anyone wanna ship it over for me? I'll pay, of course

 

Honestly, what burns up pistons and pops head gaskets is poor tuning. Unless the rest of the rotating assembly is old and fragile, running 2-4 more psi shouldn't hurt a thing if the timing and fuel are dialed in properly.

 

In that older thread of yours... we kind of decided it wasn't feasible to increase boost. But with 8.5 CR and 4lb you still have a fair window before you will start pinging. Whats your spark advance set at for 3k?

So, giggle gas huh?
You have to be careful you don't lean out... if you want to install a dry system that is.
What I think would be a good idea is have a supplentary propane injection system... like what a lot of diesels have, so when you "flick the switch" on your nitrous, you can still have enough fuel.


And your Bronco is your daily driver isn't it? I personally don't like lower gears, on anything that you want to drive out the gate at the track. But thats a personal thing, I like to have an engine idling while cruising at 60

 

Spray a small dry shot before the blower. It will drop your IATs tremendously and pick up a lot of power for ya. A 50hp jet will pick up around 100-125lbs of torque and 60 or 70hp simply from the cooler air charge.

A dry kit is either sprayed through the MAF and uses that to add the extra fuel or it is sprayed post MAF and bumps the fuel pressure up. Either way is fine, just make sure you throw a wideband on it, especially since you are supercharged. A wideband, Mallory 685 (which also has can accept a MAP sensor for boost timing retard), FPSS and some conservative tuning will go a long way in having a reliable setup.

 

^A good suggestion.... BUT... he ain't running EFI, his truck is using propane carbies...