Thread: Supercharging a P38

There are/were two on the northside being serviced by MR, they may be able to point you in the right direction


Cheers


Rushy

Tasi devil on this forum has a nice looking Eaton setup. Check out the mix: Tornado,Haltech,Eaton & Austune

I personally think that a M90 would be too small for a 4.0 or 4.6. An M112 off the cobra from america can be picked up dirt cheap on eBay US and you wont be working the blower as hard to acheive the same results. Given the already silly under bonnet heat in these things, the efficiency of an M90 in those conditions wouldn't be that great.

By the way, blowers do produce a huge amount of heat and given that I can't touch anything on my engine for over 30min after it's been running, I wouldn't be putting any more heat in there. I'm already scared something is going to melt.

We used to run an M112 on our burnout car, and that was just feeding a 4.0 Lexus V8. This was geared up to around 10psi, and if you need any proof of how hard it was working, listen to these vids...

[ame="http://www.youtube.com/watch?v=uLmZBYv2COY"]http://www.youtube.com/watch?v=uLmZBYv2COY[/ame]
[ame="http://www.youtube.com/watch?v=U3idI7tgR2c&feature=related"]http://www.youtube.com/watch?v=U3idI7tgR2c&feature=related[/ame]

Ok, we did hit the wall in the first one, but you can hear that blower SCREAMING to produce that power. Granted, it is revving to about 7500rpm (engine revs, not blower revs), but you get the point. If a 112 is working this hard to produce 10psi on a 4.0, a 90 would be a molten blob.

But then again, I like things to go FAST

Cheers,
Keels.

Link is a guy using an M112 on a Rover 4.6 in a Disco.

A tyre-shredding LandRover Discovery? This can't be serious...* September 2000

if you Google it a bit there is a bit of info around, Triumph spares had a 4.6 Supercharged for sale a few months ago.

Originally Posted by Steinzy

With the AU dollar being so hi against the US $ I have been thing about super charging my P38 again.

I figure if I can by a Eaton M90 or sumular out of the states for cheap and maybe the adaptor manafolds it could be a fun exercise.

Has anyone done any research or put a supercharger on their rangie? Or can someone point me in the right direction?

Thanks in advance!

I have heard that supercharging the Rover motor can be a problem, as per the attached quote from RPi Engineering - V8 Engine and Component List

"Those with supercharges, will also discover this. On most supercharged engines, Especially those using the Eaton M90), poor fuel distribution and weak mixtures eventually cause detonation that will collapse the ring grooves on the rear cylinders and cause partial engine seizure, and eventual piston breakage"

They also have some awesome engine builds on this page, up to 5.2l

Originally Posted by RoverHse

I have heard that supercharging the Rover motor can be a problem, as per the attached quote from RPi Engineering - V8 Engine and Component List

"Those with supercharges, will also discover this. On most supercharged engines, Especially those using the Eaton M90), poor fuel distribution and weak mixtures eventually cause detonation that will collapse the ring grooves on the rear cylinders and cause partial engine seizure, and eventual piston breakage"

They also have some awesome engine builds on this page, up to 5.2l

This is a common problem on most motors with non factory blowers. The problem is that because of the design of the rotors (basically 2 screws spinning together, hence the term twin screw), the air is forced to the back of the motor more than the front. This makes it very hard to tune properly. There is an old speedway trick they use to fix this, but I was sworn to secrecy when told it

Those speedway boys know a hell of alot more than people give them credit for. A drag racer has his engine wide open throttle for 10sec, a speedway guy makes the same power at wide open throttle for 30 laps... Who ya gunna trust :P

Cheers,
Keels.

PS. Just for curiositys sake, an M90 making 8PSI on a 4.0 will be spinning roughly 2 times the revs of the motor, an M112 will be spinning about 1.7 times the engine revs. On a 4.6 @8PSI, M90 2.4x engine revs, M112 1.9x engine revs.

This is assuming 100% volumetric efficieny which isn't the case, but just for demonstration purposes.

so assuming the S/c was for a tad more poke on a Thor 4.6 in the flat zone in top gear (1700-2500 rpm) this would not over stress engine nor would the M112 be anywhere near capacity. would it (M112) have sufficient puff at 3x1.7 =5,100 rpm to make a difference? in other words, what's the pressure curve (psi vs rpm look like?

There was discussion elsewhere here about an additional injector to reduce risk of lean mix towards the back of the engine...how does that work?

As an aside, I see Bruce Davis is offering an engine ECU chip flash upgrade for the Thor 4.6 for $850... any info...and would it be needed for a s/c upgrade?

(I obviously have nothing better to do given all the rain we've had of late... )

Edit: I have a fair understanding of the water injection principles... any idea how much water is used and does it have to be demineralised/distilled?

If you're going to go into pressure curves of chargers, there's a lot more info that needs to be taken in. Port size, runner length, total volumetric efficency, head chamber shape, piston dish, spark plug location, lots of crap....

Because a SC is is belt driven, the boost curve is effectively linear. While this is mostly true, blowers do suffer "lag" like a turbo if the blower is too big for the motor.

Lets say that the Thor 4.6 has 80% VE. Using the above calculations, for a desired "8PSI", the actual PSI would be more like 6.4PSI. If the power range you were hunting for is 1700 - 2500, the actual revs of the blower are 3230 - 4750. Now the M112 @ 3000rpm and "8PSI" has a VE of around 70%, @4750rpm its more like 75%. So lets call it 73% average. This equates to around 4.7PSI. At that speed, it takes around 18hp to drive the blower. With the added boost, correct fueling and tune, you're probably looking around an extra ~50hp at the treads. At full noise (5000rpm engine, 10,000rpm blower) the VE of the blower goes up around 90%, so you'd be back up the around the 6PSI mark, which is enough for a stocko motor :P I've lost my charts for the M90 and am too drunk for any more maths

As for the additional injector, basically, because the blower is forcing more air into the rear cylinders than the front, that means the rear runs lean compared to to the front. Shoving an extra injector at the back, when tuned properly, will account for the extra air and apply more fuel as neccessary to acheive a good air/fuel ratio, and bring it to the same stoichiometric level as the front. This decreases the chance of detonation and lunching a motor/melting a piston. While a good idea, it's much harder to set up this kind of system properly than it is to tune your car right. Most people just kind of jerry rig the setup and pray for the best. While more often than not this seems to work, it's not an efficient or pretty way of doing it.

If you were to supercharge the motor, an ECU upgrade would be pretty much useless unless it was designed for the the blower/motor combo you were using. A piggyback or stand alone fuel management system is deffinately recommended.

As for water injection, we used to run a VR commodore 3.8 with a vortech supercharger kit that had water injection. It got driven hard on a daily basis at around 12PSI. The 2L tank for the water injection seemed to last forever. We used normal tap water, some people say used distilled, it doesn't really matter. What you should be using is methanol injection

Cheers,
Keels.