Home At Last

Chris Nordon dropped off my car yesterday after passing IVA. I called my insurance company to get cover now that the car is ready for registration. I now have 30 days to register the car, so will send the documents off over the next few days.

As the weather is not the best at the moment and the tyres wont be much use in the wet or at such cold temperatures, it gives me a good excuse to do a few jobs. 

Fit the 3.14 LSD
Set suspension ride height
Remove the cylinder head, grind the valves, replace valve stem seals etc. 
Fit the SBD throttle bodies & itg filter
Fit Tillett seats when they arrive.

Forced Induction Comparison

Based on my requirements I have compared the options of supercharging and turbo, I have now a better view on which way to go. Thoughts on the functionally that is important to me:

Linear power delivery:
Supercharger - This is achieved very easily by the supercharger by the way that boost increases with the rpm of the engine, then to make maximum boost at high revs. Boost is directly proportionate to the engine rpm with little boost at low rpm and high boost at redline. Controlled by the pulley and adjusted by different pulleys and selecting the correct compressor map.
Turbo - previously I thought that a linear power delivery was not possible with a turbo, however this turns out to be an issue where the turbo is undersized and ramps up the boost too early. With a larger turbo, a smoother power delivery can be achieved and is controlled by the waste gate actuator to a desired level. This can be controlled at different levels by a boost controller or the ECU.

Target power of 350 wheel hp:
Supercharger - 350 wheel hp is possible with a supercharger as shown in the attached Dyno chart from TTS, power delivery looks progressive.
Turbo - The turbo can achieve switchable boost levels that produce power outputs of 230 wheel hp to 450 wheel hp.

Good torque low down in the rev range:
Supercharger - Supercharger uses low compression pistons and a thinner barrel spacer to raise the compression a little to just less than stock. The supercharger also is running at all times so makes low levels of boost that adds torque at low rpm. The supercharger makes about 90 ft/lbs of torque at 3000rpm.
Turbo - The turbo also uses low compression pistons which are at a much lower level than stock. Power at 3000rpm is slightly lower at about 80 ft/lbs torque and builds as the turbo spools up more, however this is plenty and more than a stock engine.

Reliable and safe power:
Supercharger - At 350 wheel hp there is debate as to wether or not updated rods are required as well as pistons. My thoughts are to go for a built engine to be safe. Generally to make the same level of power the supercharger requires more boost. Running at high rpm at high boost for a prolonged period of time will put additional stress on the engine, this is partly to do with the overhead of driving the supercharger. The supercharger is driven off the end of the crank and is belt driven with pulleys which sometimes need adjustment.
Turbo - With a turbo, 350 wheel hp is achieved at relatively lower boost and can be managed with only pistons and updated head bolts, rods are not necessary. Again I'll go for a built engine to be safe. To keep inlet temperatures down I will install an intercooler. The turbo is driven off exhaust gasses so no real losses or moving drive parts. Only problem is heat generated from the turbo, which can be mitigated by fitting the turbo externally in the airflow. However this can be unsightly compared to a supercharger solution.

Option of different maps to load in to the MBE ECU:
Supercharger - The boost level is controlled by the gearing of the supercharger and the pulley sizes. The ECU cannot change these, however the fuelling can be controlled. With this option I cannot choose different maps for different power levels.
Turbo - With at Turbo the boost level is controlled by the ECU and there is total flexibility in choosing different maps and even limiting boost in different gears to support traction on higher boost applications. 

Ability to adjust the power level based on conditions with switchable boost:
Supercharger - Switchable boost is not easily possible with the supercharger, the boost is controlled as described above and builds as the rpm increases and provides maximum boost at the redline. There is a possibility to bleed boost using an external waste gate linked to the ECU to reduce the boost over the rev range.
Turbo - Switchable boost is easily achievable with the MBE ECU. The MBE 9A4 supports one target boost map and also additional in gear limits. The way to achieve 2 stage boost, is to control the first stage of boost by disconnecting the control signal to the boost valve via a switch and then to let the turbo control on the waste gate actuator. The waste gate actuator can be set to 9 PSI which is 0.6 Bar and would control happily to this all the way through the rev range. When higher boost is required, the boost valve would then be switched in and the ECU would control the boost to the target set in the boost map, typically as a rule of thumb can be up to two to three times the waste gate rating dependant on the quality of the actuator. Different maps can be created to set different boost maps, but need to be loaded via a laptop. I will look to see if the ECU has the capability to have switchable maps via a selector switch. Failing this, I can fit a boost controller which can control to many different boost settings.

To put the power down to the road in a controlled manner with minimal wheel spin: 
Supercharger - The power delivery with a supercharger is progressive, which supports good traction off the line and through the rev range. When running higher boost and different gearing, traction will become more difficult and can be managed by dropping the gearing to lower the boost.
Turbo - A linear power delivery can be achieved similar to the supercharger if a larger turbo is selected. The boost can also be limited in each gear to provide lower boost in the first few gears and then full boost for the rest. Traction and launch control can also be provided by the ECU, the only problem is having enough spare inputs to achieve this.

To be able to drive at motorway speeds off boost:
Supercharger - The supercharger provides boost all the time based upon the rpm it is running at, so at motorway speeds at say 6,000 rpm it will be delivering around 10 PSI boost, which is good for power but probably not good for fuel economy or engine wear.
Turbo - A turbo can be driven at 6,000rpm off boost based on the amount of throttle applied. It is possible to hit the redline at part throttle.

Modulate boost based on throttle position up to full boost:
Supercharger - Not possible, boost directly proportionate to the engine rpm not throttle position.
Turbo -  The MBE boost map can be set to provide no boost up to half throttle and then progressive after this. My Noble was mapped in that way and gave exactly this functionality, I was able to balance the boost via the throttle position, on the other hand it was mainly 100% most of the time.

To be able to increase the power in the future if required:
Supercharger - Provided that the supercharger selected has capacity to provide additional air volume, a higher power output can be achieved by re gearing of the pulleys. Sometimes superchargers can be over spun to get more boost out of them, however they are on the limit and this would impact on reliability. If I go for a built engine then it would cope with the additional power.
Turbo -  Again, provided a turbo is selected with a compressor map that has capacity for more boost, then it would be fine for additional power. With both solutions the aim is to pick a unit that is small enough to spool quickly but big enough for more power in the future. 

Quiet enough for Track Days:
Supercharger - Should be ok with the right exhaust system and induction piping. May need to replace the silencer with a Raceco system. Induction noise is supposed to be louder.
Turbo - Should be quieter than the supercharger due to the turbo impeller sitting between the engine and the silencer. There is an opportunity to go for a larger bore exhaust as back pressure is not required in a turbo application.

Fast enough to scare me :
I'd say that either route would be enough to deliver plenty of power to keep things interesting.

Summary:

Potentially the maximum power that could be used in my application will be limited by traction, which is estimated at being about 320 wheel hp, any more than this is likely to cause poor  traction and loss of drivability.  Based on the above and the flexibility it provides I feel that I am going to go with a built engine and a larger turbo.

Here are a few dyno graphs from turbo and supercharged installations:

Forced Induction - Supercharger or Turbo?

I have been doing some research for a while and trying to find the best way forward for my build to give increased but useable power.

Functionality that is important to me is:

1. Linear power delivery
2. Target power of 350 wheel hp
3. Good torque low down in the rev range
4. Reliable and safe power
5. Option of different maps to load in to the MBE ECU
6. Ability to adjust the power level based on conditions with switchable boost
7. To put the power down to the road in a controlled manner with minimal wheel spin
8. To be able to drive at motorway speeds off boost
9. Modulate boost based on throttle position up to full boost
10. To be able to increase the power in the future if required
11. Quiet enough for Track Days
12. Fast enough to scare me

I have spoken to quite a few companies who offer supercharging and turbo conversions, along with an amount of research on the internet. As I expected there are mixed opinions and arguments to go either way, however one thing in common was that for 350 wheel hp I really need as a minimum, a built engine with upgraded rods and pistons along with a barrel spacer and adjustable can verniers.

One good post I found was on Hayabusa.org in reply to a question about "Pro's & Cons of a Supercharger". Seems quite balanced from someone who sells both solutions.

Post reads:
" I both turbocharge & Supercharge motorcycles for a living. When you compare the two there is a lot in to take into account.

The Superchargers just like Turbochargers come in various shapes & sizes but on road going motorcycles there are only two truly available ones that work effectively. The Rotrex & the Procharger. The Procharger will make more beans at the same level of boost because it is relying on moving volumes of air rather than the speed of air. The turn ratio in the procharger is less than the faster Rotrex but the Rotrex does not have as big an impeller or as big a scroll or as big an inlet & it does create more heat through the fact is moves less air faster. The Rotrex is much quieter & a lot easier to fit as the prochargers are more bulky. So they both have their plus points.

With both these types people should not fool themselves by comparing to the old wipple & roots style units that give instant boost. These are in effect turbo impellers driven through gearboxes & a belt from the end of the crankshaft. Neither in a decompressed engine make any more than a stock motor upto 3500 to 4000rpm on a Busa nor do they make any more low down than a correctly sized turbo. The reason is the airflow needs to build via rpm speed to a suitable level where the engine turns from vacuum to positive.

Superchargers are hindered in daily use by the requirement to adjust belts, & replace pulleys, & engine seals & bearings all of which have to be designed to rotate at 11,000rpm under load.

Yes superchargers loose power in their driving by the force needed to rotate the unit.

Superchargers boost all the time after going positive from vacuum. You have to think about this. It means if you are accelerating quickly or slowly or constant cruising or even decelerating or bashing down the gearbox going into a bend the boost is linked with the rpm & thus it is boosting even on deceleration though it may be vented off the hot air is still there...

That is the principal reason why I would never consider bolting a Supercharger to a stock engine they heat soak & are more liable to give engine failure due to the increased boost usage. A turbo by comparison only boosts when you load it. In other words pull the the throttle back. You can red line a turbo at 10% throttle & make no boost at all & obviously at a cruising speed on roads it remains off boost.

This then means that the turbo can be mapped with much less fuel usage than a supercharged engine as the enriched state only needs to be when it is generating boost which unfortunately for the supercharger is every throttle position from 3500 onwards.....

Supercharged engines will naturally make more exhaust noise than turbo engines. A serious consideration at certain race tracks. This is because the increased exhaust gas from aspirated is unchecked & at a higher level, so if your aspirated engine was marginal these will be mucho noisier on the exhaust. The turbo naturally quietens the exhaust by the spinning of the impeller.

Turbos can be linear in boost delivery & should not suffer lag on motorcycles. If yours does then you are using the wrong size or something is crap. if you feel you need immediate power from a set of lights just put it on full throttle & lob the clutch. You will soon realise its too quick anyway when its flipped over backwards. Superchargers do have that instant feel on the throttle that a turbo does not have.

When comparing supercharger power with turbo it is important same as in rotrex v procharger to do it boost level for boost level. Remember with the turbo you can just add more boost by a controller without the need to swap pulleys. You will find the all important inlet temp is much worse on the superchargers than on the turbos this again will restrict the boost on usable road fuels & the power potentials."

IVA Pass

The car went in for a re test today and I'm delighted to say that it has now passed.

Marc took the car to Beverly for the re test on noise and brake balance, the exhaust is now below 99db and at an acceptable level.

A good job well done.

IVA Failure #3

Car is booked in for it's re test next Thursday on the 14th November. Will be tested on the brake bias and the exhaust noise levels, looking forward to better results this time.

3.14 Differential Refurb #4

Pressed on the bearings at a friends garage, quick job with the right tools. Cleaned up the bearing carriers and gave the threads a good blast with carb cleaner to make sure that the threads were clean. Fitted new o rings and greased the carriers before fitting. Had to remove some of the diff casing on the inner left hand side to allow the LSD to be maneuvered in to place.

Put the diff back together and tightened both carriers until they were roughly in place and were holding the LSD bearings tightly in place but easy to move. Applied engineering blue to the crown wheel and rotated the diff until there was a good amount of coverage on the crown wheel teeth. Adjusted the bearing carriers in and out until I got a good spread of blue across all teeth. I noticed that if I over tighten the carrier near the crown wheel too much it makes the pinion and crown wheel lock together, I then backed it off a little, then the diff turned with the right amount of resistance. Next tightened the other bearing carrier to take up the slack. 

Re fitted the locking pins, re assembled the back plate and greased the drive shaft seals. Ready to fit over the winter.