Twin or single supercharger on RV8 ?

Wotland · Post by **Wotland** » Tue Dec 26, 2006 9:48 pm

Hi All,

Someome here has already tried to put two small superchargers on Rover V8 EFI ? I have two 1Litre twin screws superchargers in my garage

. My engine capacity is 5.3

If I use two superchargers I will use something similar to siamised plenum.

Or it is better for effiency to use one single large displacement supercharger like eaton M112 ?

Thank for your advice and happy new year.

Cheer.

stevieturbo · Post by **stevieturbo** » Wed Dec 27, 2006 6:53 pm

First off, the M112 is not a twin screw.

The Rootes types do not perform anywhere near as well as an equivalent twin screw.

So...assuming blowers of the same trpe. I dont see why 2 small ones would be any better than one big one. They would just be far more hassle to fit and get working.

Eliot · Post by **Eliot** » Wed Dec 27, 2006 9:41 pm

Too much trouble and probably produce less power than a single. Eaton 112's come up on UK ebay quite often - stick to that.

kev_the_mole · Post by **kev_the_mole** » Wed Dec 27, 2006 10:01 pm

....but you could then put "Double Supercharged!" decals on and that would give you tons of virtual performance down the pub

Post by **katanaman** » Thu Dec 28, 2006 1:00 am

kev_the_mole wrote:....but you could then put "Double Supercharged!" decals on and that would give you tons of virtual performance down the pub

Has to be worth more pub HP good thinking!

Wotland · Post by **Wotland** » Thu Dec 28, 2006 8:31 am

Hi All,

Yes I know it will be a lot of work to be reliable.

I have bought a set of three IHI Lysholm Superchargers 1000CC (one is already sold).

I would like to build a plenum similar than AJ6 Engineering Intercooler plenum but with twin inlets.

Wotland · Post by **Wotland** » Thu Dec 28, 2006 11:58 am

Here an exemple of twin Sprintex mounted on Chevy 350 : http://www.v8914.com/

JP. · Post by **JP.** » Thu Dec 28, 2006 12:05 pm

IMO the two 1000cc superchargers are to small as is the single Eaton M112. You need loads of overdrive to feed an 5300 cc engine. The restriction on such large capacitie engine will be the superchargers itself.

You'll need about 130% overdive on your blower to reach about 7psi but I don't thinks these size of blowers have the capacity to fill up and boost these figurs on high capacity engines.

I am running a M110 (1800cc / rotation) and running it already on 60% overdrive to feed my 3500 V8 and archieve 6.8 Psi overboost @6000 rpm.

GreenV8S · Post by **GreenV8S** » Thu Dec 28, 2006 3:32 pm

JP. wrote:IMO the two 1000cc superchargers are to small as is the single Eaton M112. You need loads of overdrive to feed an 5300 cc engine. The restriction on such large capacitie engine will be the superchargers itself.

You'll need about 130% overdive on your blower to reach about 7psi but I don't thinks these size of blowers have the capacity to fill up and boost these figurs on high capacity engines.

I am running a M110 (1800cc / rotation) and running it already on 60% overdrive to feed my 3500 V8 and archieve 6.8 Psi overboost @6000 rpm.

Not quite sure what you mean by 'overdrive' etc. If you mean that the blower is running faster than the engine, that's how you would normally use them. The maximum throughput of the blower is determined by the blower's displacement and rev limit. The bigger Eatons are rev limited to about 12,000 rpm (the smaller ones will rev slightly higher). An M112 displaces a little over 1.8 liters, given an engine rev limit of 6000 rpm the highest gearing you could run would be 2:1 which corresponds to 3.6 liters per crank revolution, which is what a 7.2 liter 4-stroke with 100% VE would consume. You can get a rough idea how much boost that's going to produce from the capacity of the engine it's connected to. I.e. it would produce no boost at all on the 7.2 litrer engine, 1 bar of boost on a 3.6 liter engine, and so on assuming the base engine has 100% VE. In practice the engine VE is likely to be far less than 100% so you would expect to get slightly higher boost (backpressure) than this.

These are the maximum figures that the blower could produce, obviously you can gear it down to produce lower boost.

JP. · Post by **JP.** » Thu Dec 28, 2006 4:52 pm

GreenV8S wrote:
Not quite sure what you mean by 'overdrive' etc. If you mean that the blower is running faster than the engine, that's how you would normally use them. .

Nope a 6-71 needs to be underdriven on a 302 for example otherwise your boost figurs go bezerk

even like the 4-71 needs to be underdriven on a 3.9 V8 unless ofcourse you want to run more than 15psi boost but you won't run that on a bone stock engine..............(15 psi is about 1:1 driveratio on a 3.9 V8 with a 4-71 and thats a lot with 9.35 cr)

Normaly you choose a supercharger in comparison with the engine displacemend. So a 6-71 on a 350 engine runs 1:1 to deliver about 7psi boost and with 10% overdrive it delivers about 11 psi boost.
But on a 289 engine with 10% underdrive it also delivers 7 psi boost.

GreenV8S · Post by **GreenV8S** » Thu Dec 28, 2006 11:12 pm

JP. wrote:Nope a 6-71 needs to be underdriven on a 302 for example otherwise your boost figurs go bezerk

You're right of course, the point I was trying to make was that the gearing needed to be chosen to give the flow rate you want based on the blower displacement, engine displacement and desired boost. If you put a monster blower on a small engine, that might mean gearing it down. If you are using smaller blowers (as in the OP's example) you'd gear it up. It's perfectly normal for these small blowers to be geared up.

Wotland · Post by **Wotland** » Sat Dec 30, 2006 5:56 pm

Hi All,

Someone here can explain to me why two 1000cc are too small ?
I am completly new in supercharging engine.

In theory which supercharger displacement I need for an 5.3 ? I will run between 6-8PSI.

There is a little software on Sprintex website, I use often it. It is reliaible to calculate supercharger application ?

Thank for your help.
Cheers.

JP. · Post by **JP.** » Sat Dec 30, 2006 6:20 pm

Wotland wrote:Hi All,

Someone here can explain to me why two 1000cc are too small ?

Cheers.

Cause you'll need to speed them up till atleast 14000 rpm to reach about 7 psi @ 6000 rpm engine speed on a 5300cc engine.

Mine is running 9600 rpm at 6000 rpm engine speed on a 3500cc engine and you don't want to know how much it screams.........Have to say mine runs on a 8mm pitch belt which makes the noise even harder. I have an open exhaust system but above 5000 rpm engine speed you definetly won't hear the exhaust and engine annymore.

In your case, well you sayed your engine is 5300cc so at every rotation it wants 5300cc but your supercharger delivers only 2000 cc so it has to run very hard from the begining to forfill the engines needs.
On the other hand blowers don't blow more than they can which could result that you may never see the boost figurs you want to see cause the blower itself becomes a restriction.

Post by **katanaman** » Sat Dec 30, 2006 6:42 pm

5300cc engine will need 5300cc every 2 revolutions not 1 so that's 2650cc per revolution which means his 2000cc wouldn't have to be geared that much higher than engine speed. Or have I got it completely wrong?

JP. · Post by **JP.** » Sat Dec 30, 2006 7:11 pm

katanaman wrote:5300cc engine will need 5300cc every 2 revolutions not 1 so that's 2650cc per revolution which means his 2000cc wouldn't have to be geared that much higher than engine speed. Or have I got it completely wrong?

Yess......

JP. wrote:Mine is running 9600 rpm at 6000 rpm engine speed on a 3500cc engine

same topic...

JP. wrote:I am running a M110 (1800cc / rotation) and running it already on 60% overdrive to feed my 3500 V8 and archieve 6.8 Psi overboost @6000 rpm.

And we are talking about only a silly 7 psi.........
I can gear it up to 86% overdrive to see 9.6 Psi which means the blower have to run 11160 rpm versus 6000 rpm engine speed.