The V8 Owners Forum -

Just a quick question lads. RV8 4:6 with the normal goodies, in the process of converting it to fuel injection (Mega Squirt) in-keeping with the Eaton needs, inlet manifold/trumpets bored out from standard to 44mm ID, shortened trumpets as per V8 developments pattern. Made up a twin plenum cover. Now I have two inlet holes and two superchargers available just wondered what effect fitting two units would have; firstly re CFM, Eaton as above runs around 720 cfm @ 12,000 rpm I think also would this affect the boost as I don't want to run really more than 8psi as only have cast pistons 8:4.1 CR.

Any help would be appreciated chaps.

The only bonus I can see for twin SC is that each one will only be working half as hard so there may be less heat generated in the charge.....

I doubt it would run cooler as your would be right on the lower limit for the M112.

My calcs show that at 6200rpm you would be just into the sweet spot.

At 3000rpm your adiabatic efficiecy would be down around 30-40% which means loads of heat being generated. In fact somewhere around 130 degrees centigrade of added heat without an intercooler as opposed to about 85 c if you used a single M112.

If you want a twin setup why not look at two M45's

Did some math on the setup you’ll mention.
With your 280ci engine and the 112ci blower you’ll get:
Single Eaton 112 setup:
8.3psi with 2.25 overdrive ratio, that’s 13500 blower rpm @ 6000 engine rpm.

Dual Eaton 112 setup:
7.8psi with 1.1 overdrive ratio, that’s 6600 blowers rpm @ 6000 engine rpm.

The actual boost can vary by cam profile and head design. For example, I lost 2psi when I switched over to Merlin heads but it delivered way more horsepower. Boost readings are only a measurement of backpressure in the intake.

Single Eaton112 is possible cause they’ll become inefficient above 15000 blower rpm.
Dual Eaton 112 means that they’ll have to run half the speed meaning less heat and more long livety and less noise.

For your interest, the calculated corrected CR for your engine will be 13.1 :1

JP. wrote:

Dual Eaton 112 means that they’ll have to run half the speed meaning less heat and more long livety and less noise.

The killer here though is the very low inefficiency of the twin setup at such low rpm and boost. At 30% efficiency you'll generate more heat than if you were running a single M112.

Don't make the mistake of assuming that just because a blower is running slowly it's running cooler. The airflow at the lower end of it's efficiency range is very turbulent and this turbulence generates a huge amount of heat.

Problem with even running two m45's is the parasitic loss. Stick to a single 112 IMO.

Eliot wrote:Problem with even running two m45's is the parasitic loss. Stick to a single 112 IMO.

Would agree with that statement.

Only suggested two M45's as the guy seems to want to go twin blower route.

Can understand that.......still looking at a twin M112 setup for mine

Rossco wrote:Can understand that.......still looking at a twin M112 setup for mine

I would suggest you wait till you get it in N/A first. Over 400bhp/ft-lb in a Range rover induces comedy chassis twist and comedy handling. Just ask the guys who went to the dyno day.

Oh dear looks like I'm in for some chassis stiffening.

The 455 is 510 ft-lb in standard trim and probably well in excess of 600 with the alloy heads and cam I've got.

Perhaps some 8mm plate welded onto the chassis rails may stop the twist?

You ideally need round tube for chassis twist, more round tubular cross sections would make a big difference

I think Rosco will will need a spaceframe chassis based around a full roll cage, similar idea to the Bowler chassis. Should make one h3ll of a golf GTI scarer though .
Mike

Yes I've already started looking at some form of subframe to replace the gearbox cross-member and another to tie the rear end a little more tightly.

An tubular chassis for LR like this :
http://www.ppcages.com/displayimg.php?u ... in/006.jpg

Wotland wrote:An tubular chassis for LR like this :
http://www.ppcages.com/displayimg.php?u ... in/006.jpg

ooooo now that's sexy

Many thanks gentlemen for your calculations and advice. Did actually purchase two new M45,s a while back from Speed Shack Westdrayton but advice from a serious blown Cobra owner was much the same as yours re heat etc so I sold them on.

The idea for twins mainly came from this site some months ago re a 4:6 Mustang with twin M90's, apparently it was reported to have more Torque than the Queen Mary! I shall stick to a single unit then and no doubt will be back with many more questions as the mod's progress next year, cheers chaps.