Build List

XPOWER SVR-S by Brian Payne - the 629 bhp SV!


I have to be honest the results were gratifying for all the effort and expense but I am running stronger cams etc; than what a OEM would run, and the boost way in excess of the Shelby and Roush Mustangs.
I think I may have found reason for slight stutter problem I have mentioned. In doing extensive data logging I have found that Bank 1 - 02 sensor occasionally throws up a fault code. Not consistent and no MIL light, but can now understand what route to go now for hopeful cure.

Twin plate clutch due today, so will post a couple of pictures later for anyone interested and once installed, up the anti a little more to 20psi boost and go for a nice round 650bhp....................................


The Dyno Run.

Following the 1st run on the Dyno Dynamics rolling road I queried the BHP output figure. The dyno operator said that they were all correct and then conducted a further 2 runs which gave readings all within 10bhp.
He then conducted one further run (4th run) but with engine temps rising slightly and intake temp rising the result was down by 20bhp.

Had a break and a cup of coffee, engine cooled and then we commenced the final run. Output back up to 629.7bhp with 585 ft/lbs torque. The power and torque curves are nice and smooth, with a boost pressure reading from the dyno of 16.2 psi (in car gauge shows 17psi. A/F ratio stable and no excess water temp issues, staying steady between 80/90 C.

Smelt rubber on last run which would suggest tyre slippage on rollers!!! Definitely rubber and not clutch smell.
Below are 4 attachments:-

  • Original R/R dyno result, FEB 2006 R/R day, with 5.0L N/A engine. Hummmm!!Todays R/R dyno showing BHP and Torque figures.
  • Out of interest, all be it not exact to a fine detail but to produce a comparison, superimposed the results of today alongside the 99 Cobra/SHM/Roush graph posted earlier by others.
  • I was going to include an extract showing a dyno result of an 03 Cobra with similar S/C and cams, but uncertain as to publicity rights? so refrained! If anyone interested I could PM you. Included instead today's FWHP and the RWHP figures for comparison.

All the above has been achieved in having fun developing this wonderful motor car and whilst every effort has been taken to ensure accuracy, there is no accountability should there be any errors attached.

Next stage, to rectify a slight off idle niggle within the engine management, install smaller S/C pulley to go to 20psi if possible, and install the Motec800 software to fine tune further, if at all possible. In cruise mode (ie legal to just above!!!) the mpg return shows 20/21mpg. On rollers or track drops a little to 7-8 mpg.

This post concludes the article on taking a standard 4.6L 4V from 310/320bhp to the present performance.

 Before - 358 bhp After - 629 bhp After - 629 bhp SV - SVR - SVR Comparison



As weather is really good and my son came round to see me I took him out in the car. He is always a good passenger (loves trackdays, but then he does ride a big Yamaha) and a good judge on where I am at present on performance. I can then concentrate on keeping the car in a straight line while he looks at what all the dials are doing. 2nd gear, foot to floorboards, 17--yes 17psi of boost, fuel pressure 70psi, smoke off rear tyres, Tracction Control Off, 6500rpm and into 3rd, pressures all the same again and beauty is the Air/Fuel ratio good at 11.5/11.8, into 4th and then I looked at speed.

Dare not publish on open forum but well into 3 figures. My son says that he is certain that the acceleration matches my Holden HSV.

Next step the dyno. Promise to keep you informed. Below are pictures of the finished binnacle and the cockpit ready for business.


A technician is visiting on Sat to:

a) disconnect the Omnitec which he says will not involve cutting any wires, like the sound of that and,

b) to reprogram the ECU relating to the new engine, ie,a Ford Mustang Cobra untouched by others!!! to the existing security system.

If this all works out ok I can then see to mapping and flashing this ECU which I hope will not have the MG and other and other etc 's inputs into the s/w.

Attached a couple of pics showing the rain cover for the Alternator, and the moulded 3 gauge pod binnacle to accept the Boost, Fuel and Oil pressure.

Spoken to Anderson & Ryan who will recover my binnacle. They will supply clips and have been told that I can see what else I might need for these redundant, bespoke interiors.


Idle has never been what I would call OEM perfect on the standard engine. Up and down on RPM and hesitant. SnR improved it but did not become perfect with MIL light on and off. With the new installation and new engine harness installed and a little tidy up no DTCs shown and MIL now behaves. Now I have the modified the  engine the new program in the ECU is no good on idle so having to look to remap. This Supercharger ECU program has a chip installed, which while the supplier feels should be ok this cannot be guaranteed.

I have never been a great fan of chipping, prefer to re-flash ECU with modified settings. This is where:

a) I get a new ECU to talk to the remainder of system and then start a remap programme,

b) stay with a chip but get the necessary to rewrite new chips, or.

c) go the whole hog and get a Motec engineer to install my M800 and the have the best of all worlds in mapping the ECU.

Fitting addition gauges is for my peace of mind, so as I can see what's going on so yes this is something I proposed following decision to go down the Supercharger route. However, I do  require the 3-gauge pods to look OEM.


Carried out a couple of short road trials. In short the s/w setup not to good on idle and pickup. Seeking further map setups and going to talk to Roush or consider a Motec800 installation, which I have sitting here doing nothing at present. Need to find a reputable guy who knows Motec setups. Have a guy coming to remove the Omnitec and possibly reprogram a ECU to the security system.

That's the preamble, now once off idle and say less than 1/4 throttle, press throttle for say normal acceleration and the boost comes in immediately. Will require a far better setup than the existing on/off MGR unit. As its a new engine with lots of new components I don't wish to push at moment, but 10psi comes up easily on these small throttle openings, so what will WOT produce

Pleasing bit is that all the work I have carried out has effectively turned out as planned and the engine is a lot quieter than the original engine.

Also replaced the cold (in winter/hot in summer gear knob). Never liked the alloy one so fitted a original leather Cobra gear knob.

When I get idle/pickup problem resolved I will let you know on performance, and the final decision on gauge mounting. I'm talking to upholsters who know these cars and discussing various options, regarding gauge pod and the upholstery.


Fitting a 3-gauge pod for the following - Fuel pressure, Oil Pressure and Boost Pressure.

Fuel Pressure, which I add is electric operated inside the car, but is mechanical to the pressure sender and then driver friendly wiring inside the car. Oil pressure is similar.

I now have to remove the rear panel upholstery to access to the fuel pump/filter (what a poor thought by MGR in not making the fuel filter easily accessible) to install the BAP to give increased fuel pressure when on boost.

Turn on key, hit the start button an "walla" she fires up immediately, now that I have set throttle body stop screw and adjusted TPS to read .96/.98Volts at idle. 1200/1000/900/all in about 2 mins.

With low temp stat: fitted the fans come on at about 75 C on idle and at 85C the high speed comes in. Keeping cooler restricts detonation and will hopefully give better Air/Fuel ratio.

Still have to run on road yet (Air con being charged next Weds) so following this I will fit clamshell and then see how it runs on the road.


Fired her up and after clouds of smoke (I'm a stickler for swamping everything in oil on a rebuild) and following a) a rattle in area of water pump which was an air lock that was easily rectified and b) a knocking which was a sticky hydraulic valve lash adjuster it settled into a nice lumpy idle.

Idle area requires some attention, ie blip throttle and when dropping down goes into a semi stall situation, but my diagnostics show no fault codes other than 1000 which is the Ford ECU learn cycle which require a systematic drive cycle or at least a long varied run for the ECU to learn.

There are quite a few pictures of the normal daylight so as you can all see a clearer picture. Do a slave fit of clamshell and everthing clears, having seen to replace washer bottle, modify MAF sensor position, modify top radiator water hose pipe and a few other minor bits.

If you study the pictures and are familiar with the under bonnet layout you can see the modifications and  alterations. The oil pressure on start up dead cold reads near 100 and when hot at idle 50 psi.

The air intake will be right down low at front of clam and I have opened up and wire gauzed the o/s blanked of air vent to give more air to intake.

The idle definitely has the slight lobe effect due to the higher lift and greater duration on the camshafts fitted.

Now put to bed and going to sink some well earned beers over Xmas and will resume in New Year.


Accompanying photos will show you that I am at the final stage in he quest of more power (Sorry about the poor quality but in the garage and no high intensity lighting and all the black bits makes for poor pictures. I will take some outside in natural light over Xmas).

As can be seen the engine and gearbox are now installed. The electrics for BAS, BAP, oil pressure, fuel, boost gauges are coupled up. Also coupled up the water system for the intercooler. That little episode took a while deciding where and how to fit.

I've modified the brackets for the engine electric box so as the rather nice induction manifold/intake lays nice and straight with no severe bends as per the standard layout.

Also, decided to fill box with Redline D4 ATF as this works better in colder climates and improves shift quality, apparently. 3 litres of fluid was required to fill to 0.75 below filler plug as recommended by Tremec and Mustang owners. This improves the shift quality I am told.

Need to Bleed the brakes, fit the Propshaft, exhausts, EVAP canister, and lots of connections to gauges/ancillaries yet. The next most important operation is to fit the clamshell to check for clearances. Most important as I want the car to remain original looking from the outside.

Could possibly fire up over the Christmas period, or maybe not if the engine management do not talk to each other. Fingers crossed.


Fitted the new supercharged engine and gearbox into the SV today. I can tell you it is a struggle to get all lined up and secure. In reality this engine mass wise to large for engine bay but it does fit after a struggle. the pictures show empty engine bay and engine gearbox assembly. Now trying to remember where everything came off.

The bright glowing unit on the centre picture is the boost-a -spark unit. It doubles the normal spark to prevent the spark from blowing out under boost. Also fitting the BAP to assist fuel pressure. Some tuners pooh-pooh this unit but I have used similar units on various Supercharged engines and for power I have needed these units to meet requirements as only work on what boost you set for the BAP to come in.

Also have a shift light unit coming from the States, which I personally found very useful in my HSV when thrashing around the track. I don't have time to look at rev counter, so this is a very good, cheap, and relatively easy to install unit.


Located where the engine management ECU resides and a difficult task to remove it. If any one has problems removing their dash for whatever reason ask me and I'll explain how to gain access to the ECU and remove it (if required). Plus those who are consider upgrading to later production air vents and need assistance please call!


Well, I have started to strip down  the SV-R and well what a task. I have removed many engines/gearboxes in my time but these engines in our SVs are something else. I bet SnR guys were glad that these cars came to them with running gear installed. I keep taking off brackets, the wiring is a nightmare, taking lots of photos so I can remember how if all goes back together. I've removed the chassis X members to make it easier, and if you look at picture of the wiring to the alternator, this was as I found it. Note the nice new scissor jack!


The Fidanza camshaft adjustable sprockets are engineered very nicely. The adjustment available is 12 degrees, so should enable cam timing to be exact.

Attached is a picture of the Kevlar clutch plate I am thinking of fitting, capable of 600 ft/lbs torque/bhp. Still in the indecisive stage at this moment as not sure how easy street driving with be, even though Fidanza state, bed in on street driving for 700 miles and all will be ok. I will let you know on this one when I bolt the gearbox to the engine. Also have a H/D organic/ceramic clutch but not rated to accept such high torque.

Cost Breakdown

Not including the base SV engine, however I've up upgraded most of the components to date!

Kenne Bell S/C kit with addition pulleys and boost and fuel gauges, boost a spark, boost a pump, 8 rib pulley set and belt, intercooler etc, ran out at $8710, all the parts ,ie,pistons, rods, cams, bolts, studs, gaskets, clutch ass, cam sprockets, flywheel, etc at approx $4900. So about $13610 @ $1.86 to £ = £7317.00.


Quick update, engine now fully assembled and just starting to fit the blower. Found a few niggles such as nuts and bolts missing and brackets not quite the fit that is required but generally good, and nothing that I cannot rectify. Attached pictures show:
  • the cam chain arrangement

  • single roller not double

  • View of the Kenne Bell blower mounted in the V8 valley.

Pictures below show the pulleys/belt and other ancillaries fitted. The alternator fitment/bracket required major surgery to ensure correct alignment of the belts/pulleys..


Further info on rebuild of engine. Pistons, rods, camshafts with stronger springs all installed with ARP bolts/studs throughout fitted. Installed Billet steel oil pump assembly; and ignition trigger wheel, as apparently original prone to break up at high rpm.

The valve springs used with the Crower cams stage 2 for supercharge are really strong so I had to manufacture a special valve spring compression tool to refit the collets.
The pictures  show the engine with the RH head fitted and the LH ready,ie the ARP studs as against std bolts used by OEM.

If trying to run 16/18 psi boost all these components will be necessary to stop head gaskets failure, from the information I've gleaned. PLUS the fitting of the Diamond Pistons with offset wrist pins (gudgeon pins to us limeys/poms) these forged pistons should hopefully not rattle (piston slap) to much on cold startup.

I have now sourced camshaft timing gears that are fully adjustable enabling + or - 12 degrees of adjustment. Await delivery (3 weeks) before I can fit and time up camshafts. Also ordered a puck type clutch plate to go with steel billet flywheel and heavy duty pressure plate.


Taken delivery of all bits required and decided to upgrade to a "puck" type clutch plate that I am told will handle in excess of 850bhp (I should be so lucky). Also received FPRC shorty headers, Centreforce Billet steel flywheel etc. At present I'm installing Diamond Pistons (forged 9 to 9.3 CR), Manley forged rods, ARP bolts, with a lot more goodies to come.

I believe the standard CR on the 4.6 is 10:1. The Diamond pistons I am fitting have a 11cc dish which will give me a 9 to 9.3 CR with the 53 cc head. Hopefully with this lower CR a boost of maximum around 16 psi can be possible, but I do have pulleys to take to 18 psi if I want to push the boundaries.  All this is way into the future, as I propose to gently increase power.

Shorty headers arrived today to replace the cast manifold fitted as standard. They look alright on the outside but will require some dressing up on the inside for better gas flow. The camshafts are specifically for supercharged application with far more duration than std: plus greater lift by 2mm approx. I have also some stronger springs to fit.


The rebuild of the engine and fitment of the supercharger I do not see a problem, but I will have to re-route certain parts of s/c ancillaries to fit within the clamshell/lid.

The plan is to:

  • build the revised engine,

  • install heavy duty clutch,

  • install new uprated gearbox and then

  • remove existing engine/gearbox.

Install new assembly: and possibly slave up certain items, turn key to see what happens!!!! If all is successful, bearing in mind that a different ECU with chip will be installed in the MGR electronics, I can then proceed to tidy up and ensure all components clear any obstructions.
Having purchased FPR shorty headers I am unsure as to the fitment and clearance to chassis members. There are lots of unknown questions at the moment at present. But  when complete, a run on a RR to see what the BHP figures are compared to our Silverstone results is a must.


Two very large boxes with Supercharger parts have arrived (see pictures). They parts are the slave assembly for the extra pulleys and for the resiting of the alternator. I discovered immediately that I will have to manufacture spacers to align the pulley tensioner so as the belts line up with all the idler /drive pulleys.
I purchased 2 crankshaft damper pulleys,

  • one standard size for boost to 12psi and a

  • second pulley that fits over standard pulley being larger to produce 16-18psi desired boost. Smaller alternative pulley fitted and all 8 ribbed as against standard 6 ribbed.

Apparently 6 is ok for up to 12psi but any higher and 8 gives greater grip with no slippage. With all the experience and work involved I will go for maximum output in the end and see where it all ends up. Still awaiting the remainder of parts to arrive so as I can start in earnest.


Just taken delivery of the  supercharger kit today. I have dealt with 3 different S/C companies when I ran my Holden HSV but I must say the initial inspection and comments on this kit (me being a retired precision materials/manufacturer guy) is excellent, and far exceeds the previous suppliers.  Not only is the workmanship spot on but the instructions and packaging are second to none. I now await to see if the engine parts turn up the same!


The newly acquired engine is ready and awaiting, new rods, pistons, cams, ARP studs, bolts etc. The supercharger kit is ordered and hopefully being despatched Tuesday. I'm awaiting the confirmation of my order for the above parts & components. I decided to go for a 9:1 competition ratio as I want some low down flexibility and a bit of grunt along with a half decent mpg. Because I've decided to fit "supercharger" cams along with uprated springs, I've have decided to polish and flow the ports too. These ports are as rough as a badgers ****. The SV for information has a std.4.6 cobra 99-01 engine.


New engine in process of strip down for fitment of all forged components to hopefully run to 18psi of boost. This will involve a period of time (sourcing parts plus a  delivery period etc).

The first picture is of the new engine a 4.6 99-01 Cobra engine.

copyright© 2008 MGSV-CLUB. Designed and input created by MGSV-Club Members 
Date last edited  10 November 2014