Phil's thoughts on Supercharging

The Birth of the GTK 

So Why Supercharged?

My fascination with forced induction, particularly supercharging goes back to my childhood, learning about old ‘Blower Bentleys’ and the big Mercedes’ etc.  I found supercharged and turbocharged racing cars far more interesting; also I quite enjoyed the audacity of various historical motorsport teams taking a smaller engine in a tiny car, supercharging it and going out on a track each weekend to hammer seven shades out of bigger heavier cars with engines the size of a garden shed!  I really wanted to do something like that with my BGT and I really wasn’t that fussed with a V8 conversion.

I started to research all I could about the actual theories and practicalities about supercharging.  Most people I knew assumed it couldn’t be done and reckoned I would have to get a whole of parts fabricated etc so why bother?  “Just stick a v8 in” <yawn>…  One night during another search for supercharging info, I came across Hi-flow in Australia and their kit which they had fitted to a B (and, believe it or not, an Austin Landcrab – see?  The audacity of it!  Gotta love that!).  I also found out about a guy who had actually fitted one of these to his car, Dave Munroe, who I subsequently emailed and who provided me with ample amounts of nutty enthusiasm to go ahead and try it.  He came with a warning though, he had gone through one block already with his supercharger because at the time he didn’t really appreciate what he was dealing with.  I knew if I was going to do it, then I had to know a bit more than I did.  So, back to the books and asking peoples advice…  

Seems a bit odd all of this preparation, considering one can just go down to Moss these days and buy an off the shelf unit and fit it within the weekend!  Back then though, there was no hint of Moss even considering such a unit and most people were not too keen on the idea anyway.  Some MG enthusiasts are a funny bunch and don’t take too kindly to a young upstart like myself wanting to do something different – I can recall being called a fair few names on internet BBS forums when I brought up the suggestion of forced induction; these people suggesting I sold my B to someone who “knew” about their history and got myself an MX-5 (or Miata as the Americans call them…).  Odd attitude I always thought, because MG has a history of supercharging going back to the dark ages!  Incidentally here is a picture of my favourite supercharged MG (well apart from the GTK I mean)…  

Once the Moss kit came out, all of that changed of course and now supercharging is an accepted form of tuning for the B!  Even so, I had a lot of fun designing my system around the hi-flow kit and I would suggest anyone thinking about going the supercharger route to think carefully about what they want to achieve.

When the Moss unit came out, just before I put my order in for the Hi-flow I had to seriously think about it, given their UK introductory offer price being only about two-thirds of the hi-flow cost, but the Moss unit was not my philosophy.

The difference in the Kits as I see it is roughly this:

The Moss kit is designed to fit a standard tune MG engine.  Moss will basically sell you an ‘off the shelf’ kit that you bolt on the engine within a weekend.  They have done all their homework and worked out what boost you can run and won’t sell you any parts to go higher than that boost.  It basically goes as far as you not even needing to check your engines health before you try it!  Now, there is nothing wrong with this per se, its engine tuning for people who don’t really want to have to think about it.  Its easy to do and convert back to standard when it is time to sell, thus really giving the owner his cake and allowing him to eat it too!  To give Moss credit, their unit outsells the Hi-flow, particularly in the US and UK and they have produced excellent results within their product placement (thankfully most people do at least make sure their engine is in good shape before fitting it).  Also I should mention that the US Moss guys in particular, regularly help out with technical queries on the supercharging forums and are enthusiastic owners of their own product, which I think is testament to what they are trying to do.

The Hi-Flow however, is a bit more in tune with what I hoped to achieve.  It is built around an Opcon twin screw unit.  When you contact Hi-flow they tell you to think carefully about building the engine to suit what you want to get from the supercharger and will sell you any range of pulleys to achieve whatever power you want.  They also do a range of other tuning parts which you can use to build an engine specifically designed to use the supercharger as an integral component – not just a bolt on accessory.  There is definitely a difference, take note!

So, Hi-flow kit for me it was! 

Starting it Off

By early 2004 it was definite that I was coming out to Australia to start my Masters Degree.  For me to be able to afford this (having spent far too much on the MG as it was) I started a contract position for that year and work as many hours as I could.  Unfortunately on my return from the successful job interview I blew the engine on the BGT, although to give it credit, I did drive from South Wales to Wrexham on a blown motor that was dropping its insides everywhere, only needing a tow on final expiration for the last 10 miles to Chester – destination Martins garage…

The car laid up on Martin’s driveway for a while I worked out what to do with it.  I needed a new, cheap engine; however instead of going the stage 2 route that I was advised to given my travel aspirations, I found myself placing an order with Octarine Services for a cheap budget block designed around a measured compression ratio of 8:1.  They did a good job on the engine, although I think they thought I was nuts and made sure I was aware of the limitations of the warranty service – at the time we didn’t know of anyone else in the UK with a supercharged B for advice and so there was an air of intrigue, if not mild panic about being associated with the project, I think!

That started it all off, now all I had to do was earn enough money in ten months to go to Aus AND supercharge the BGT…

Obviously, this budget engine was not the all singing, all dancing mother of high boost I had always envisaged it would be.  It couldn’t be – I simply could afford it anymore, but I argued once I had bought the Hi-flow unit, I had it and could change the engine design at a later date.  So I drew up this plan, which I could follow at a pace suitable to my circumstances of being in Aus for a couple of years…

1. Build a budget engine block; comprising overbore as necessary, standard bottom end, timing gear, valve gear etc, standard cam shaft.  New cast pistons designed to give a measured CR of 8:1.  Standard head and exhaust.  Boost to give around 6-7psi. 
2. Run engine in with standard carbs on, and then fit Hi-flow.
3. Get the engine with supercharger up to Peter Burgess for a tune up and subsequently run it for a time to get used to it; learning power, fuelling, boost, ignition timing etc – ironing out any teething troubles on the cheap engine.
4. Once happy with the engine, up the boost to around 9psi; reset tune, ignition timing, fuelling etc.
5. Strip engine.  Rebuild using new block if required; lightened, balanced, forged bottom end including toughened crank, forged pistons to run a measured 8:1 (maybe 7.5:1 – undecided yet) CR.  Adjustable timing gear.  New design cylinderhead, new larger bore exhaust, Hi-flow special cut camshaft, roller rockers of 1.55:1 ratio, 9psi boost.  Measure if any change in power/behaviour over the standard engine also using 9psi boost.
6. Up the boost to as much as it will take – re-tuning as required!!!!

So far there we have reached Stage 3 in the master-plan, and with my imminent return visit to the UK during May 2006, there may be chance to move to Stage 4.  Along the way however, a couple of changes did occur:

The head I had hoped to use on the budget engine cracked again when the engine went and it had already been repaired once, so I had to have a re-think.  About a year earlier when I was drawing up the specs for the ‘good’ engine, I had spoken to Peter Burgess about what I might need to consider in terms of cylinder head design, in order to get the best from a supercharger and would he build me a one off to that design.  In between my talking to him and buying the unit, Moss had brought out their kit in the states (but not the UK) and Peter being a savvy bloke took it on himself to develop a cylinder head straight at the supercharging market.  In the end I purchased what I think is “supercharging head” #2, as a good friend of mine in the states who bought a Moss supercharger a couple of months before I got off the ground, bought #1 after I tipped him off!

 Once I knew I was getting the head, I ended up with a custom built 2.25” bore straight through exhaust from Frontline.  This thing is mental – you can feel the exhaust gasses exiting, with the engine at idle over 3 metres from the back pipe!  Doesn’t sound too bad either, still at least in part an MG sound…

I also bought the roller rockers, but decided not to fit them whilst I was still using the standard camshaft.

Fitting the Unit

As part of my job change, I moved to Bath, which meant losing Martins garage.  After much deliberation I used Frontline to fit the supercharger unit.  They did an ok job, and were very helpful during the work.  Tim’s Dad did most of the work and his final set up of the engine timing was very close to how Peter Burgess eventually set it up on the Dyno.  I have to say though that for the most part I regret not doing the work myself.  

I could have done it, its not that hard to do, plus I feel that as I had been researching the subject for so long I knew as much as anyone.  Also I probably would have done a few things differently to Frontline, but hindsight is a funny thing; at the time I was working as many hours as I could and often worked weekends to earn as much as I could for the Australia fund, so I am not sure really how much time I would have had to do it all, if I am honest. I wouldn’t have had to pay labour charges though (except maybe to Martin of course…).

The car was finished in time for the MG80 celebrations at Silverstone and it received a place on Frontline's stand there.  The drive up to the show was my first proper drive in the car!  The newly crowned GTK received much attention that day and I was quite shocked by it all – I have to apologise for not speaking to many people about it, but I was somewhat embarrassed by the attention!  I remember when I was walking around the show at the other exhibits, every time I looked back towards the Frontline stand I was never once able to see the car for the number of people standing looking at it!

Teething Troubles

So far we have had a number of teething troubles – some as a probable result of the fitment and others a bit more confusing; nonetheless, the car is running very well indeed at the moment and I am confident at being able to up the boost soon!  A short run down of what we have been through so far:

1. Heat problems.  Frontline told me that during their initial runs of the car it got rather hot.  I was not too concerned because I assumed that the ignition was out and it was a function of this causing lean running and heating everything up and that it would be sorted once we got it tuned up.  Also the large bore exhaust caused problems both under the engine bay and below the floor, probably as a result of the hotter combustion gasses and the fact that it sat closer to the metalwork being a larger diameter. 

 FL fitted heat shields in these trouble areas, plus after much umming and ahhing I bought some heat cloth to wrap around the exhaust headers – some, including Peter Burgess do not consider this a good idea, in case the wrap traps too much heat into the head, which may cause the head to warp.  I wanted FL to fit a ducting hose from the radiator grille to the carb mouth and in doing this they removed the radiator surround, which they said should help cooler air flow over the engine from the outside.  I was never happy with this arrangement as I felt the air should flow through the radiator – particularly as we had fitted two electric fans to the radiator to aid cooling efficiency, which took up a large portion of radiator surface area and therefore I was worried that the removal of the surround panel would bypass the radiator altogether.

It did not run too badly like this though, until the onset of winter.  By this time I had fitted a wide-band air/fuel meter and new roughly the settings that the car was to run at for cruise and acceleration.  In the colder months, the air at speed would flow past the radiator as there was no surround and over the engine bay as predicted, but cause the carb to ice up!  This would cause the air/fuel mixture to go dangerously lean and would eventually stick the throttle open!  Many times I had to stop at the side of the road (by switching the engine off!) and let the engine bay warm up, and could actually knock off blocks of ice from the carb!

Eventually I took the air hose off and replaced the radiator surround and we did not have a problem again with carb icing.  I generally feel happier with this set up back to normal for the summer months too as I never found it overheated at all.  The temperature did rise in slow moving traffic but the massive flow from the twin fans always sorted this out. 

2. Clog up of fuel filter.  I believe this to be directly related to the carb icing, but I didn’t detect it until after that was sorted.  Even after the radiator surround was replaced, the a/f meter would suddenly register lean and the car would stutter and begin detonate – I would have to drive slower and slower, with a more delicate throttle until I could pull over – motorway inclines were a particular nightmare as I would have to go slower and slower so as not to start detonation.  When I jumped out to test the temperature of the float chamber though, I noted it was never iced (so the newly replaced radiator surround was definitely working!) and therefore could not understand it, but I knew the car was being starved of fuel somehow.  

I had a poke around the engine bay over Christmas and eventually found the culprit; a load of orange gunk lodged in the fuel line and filters!  I guess there was a lot of condensation produced in the engine bay when the carb icing was going on and some of this must have got into the fuel lines somehow, producing this rusty brown gunk.  I suppose the fuel filter did what it was designed to do, but the harsh throttle must have sucked this stuff against the filter mesh, thus not allowing fuel through.  Stopping or idling each time must have let the gunk fall off of the filter giving me fuel for a time again.  Anyway, change of filters sorted that out and we have not had a problem since. 

3. Oil surge.  This first happened on the way home from the tune up at Peter Burgess; the Monday after Silverstone MG80.  Now I was confident the engine was set up I gave it some hard right foot down the M1 to my Mum’s house, only to look in mirror and see a huge plume of smoke out the back – argh!  I pulled over, but mysteriously the smoke was not coming from the exhaust but the side of the engine…  I put it down to the stress of being on the rolling road for a few hours as cars do get quite harsh treatment on them and everything on the supercharger was still bedding in.  However, this was to plague me until I left for Australia the next January.  It was particularly bad after using maximum boost and then backing the throttle off to a cruise position, say for overtaking.

Eventually we worked it out as being excess positive crankcase pressure.  The standard MG crank-breathing system is not man enough for the job, with only one tappet chest breathing via a small bore pipe to the carb recirculation circuit.  A chat with Roger Parker of MGOC determined that apparently forced induction cars quite often have this problem and that any car that has been converted from normal to forced induction should have its crank breathing system.  The excess pressures were causing the rear tappet chest seal to blow, allowing oil vapour to escape on to the exhaust.  Of particular note here was that the oil mist was being soaked up by the exhaust wrap which is a dangerous fire risk!   

This is something we plan to do when I return in May, so update will follow; however I intend to modify the front tappet chest cover to breathe also, joining with the rear pipe at a Y-piece and then flowing into an oil catch tank.  This will also keep the oil vapour from the fuel circuit and should help on the performance part too as the recirculation undoubtedly lowers the octane rating of the fuel.  With both tappet chests breathing I am hoping there will be enough capacity so as not to blow the seals any more.

4. HGF.  In April 2005 I had an email from Martin telling me the car had suffered its third HGF in my ownership (the first two being a result of a dodgy head).  The cause has so far been put down to a combination of the above teething troubles (heat/cold and excess pressures), however it was noted that the gasket used when the head was put on was of an unknown make which may have also contributed.  See this page for more details.

5. Redesign of the heatshield.  This came about when Martin had the cylinder head off to repair the HGF.  We were never happy with the exhaust wrap, particularly as it could have been a contributing factor to the HGF, and once Martin saw the state of it with the oil-soak he basically refused to refit it anyway.

I had already been thinking about redesigning the heat shielding to something that I thought would work better, and relayed my ideas to Martin who built it up.  This new design works very well and although maybe it doesn’t look very pretty, during his use of the car last summer it did not overheat at all, which proves that the car is running much better now and I believe benefiting from the radiator surround, the repaired HGF and a bit of experience.  During my time with car in May we will also be having a think about doing the heat shielding again to look a bit better though…

Note by Martin - A comment made to me by Hans Pederson suggests that the stainless-steel manifold may not be the best choice.  In fact Hans' own car does not run with a heatshield despite the might of the Australian sun!  So Jet-Hot Coating it is!  

May 2006 - Update:  The car is now fitted with EDIS.

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