Supercharging a Bagheera

[andyowl]

In December 2009 Stig wrote.. Another valve idea just popped up.
The drain valve in a standard wash basin.....

I have abandoned my plan to use a magnetically closed explosion relief valve on Baggy Joe and used instead the principle of Stig's idea of a "wash basin drain valve". Thanks Stig!

The magnet to keep the valve closed at 1.5 bar was so big there was no room for the exploding gases to flow around it. Our magnetically closed pressure relief valve was originally designed to open at 50 millibars and it worked very well. 1.5bar is much harder to hold closed!

Our aluminium manifold box, with its flat sides, becomes the body of the "valve" with the valve disc on the outside and the stem pointing inwards. Over the stem is a spring pressing on the inside of the box and the end of the stem has an M8 nut and a large washer holding the other end of the spring. Tighten the nut to compress the spring and we have an adjustable explosion relief valve which opens outwards to relieve the pressure! Just like Stig suggested!

I did a trial assembly yesterday and it seems to work. Today the Neoprene seal gets added and time to take some pictures.

Tomorrow we rebuild the Blower Drive shaft with the new universal joints and go racing again on March 21st at Aldershot at the FDMC "March Solo". Seven entrants in the Historic Class so far including: MGB, MGBV8, Mini Cooper S, Austin Healey Sprite (2009 Class Winner), a "Kougar Jaguar" whatever that is, and a 1592cc Supercharged Matra Simca Bagheera S! Should be fun!

Andy

[andyowl]

The backfire explosion pressure relief valve is finished but yet to be "tried in fire"! That will follow in a few days I'm sure. But here are the pics for those wanting to do their own...

The inlet manifold is a simple rectangular box (beautifully made by a welder friend) and the relief valve is located at the centre under the inlet elbow facing forwards (so the driver can see in the mirror the flames and slow down?). It could also be used to limit the maximum supercharge pressure but that would mean unburnt flammable mixture being discharged into the engine compartment looking for something else to ignite it. Not a good idea!

The pics show the spring centred on the compression plate with its M8 tapped hole in the centre. The 4 off M3 screws at the back keep compression on the spring so that the M8 central bolt can be removed without the internals falling out of alignment e.g. to allow replacement of the neoprene valve seal. The compression plate is assymetrical to stop it rotating more than 90 degrees when the central bolt is turned to adjust the level of compression and hence the opening pressure.

The outlet has five 14mm holes for the escaping gases - they should have been 15mm diameter but my 15mm drill went missing! They can always be drilled out later. The five small countersunk screws protrude into the manifold and keep the other end of the spring centred. They also form a "stop" so that the spring cannot be over compressed and prevent the gases getting out.

The view through the inlet hole shows the spring at about half travel which should give an opening pressure of 0,5 bar / 7.2psig. This is lower than I want but better to start with a lower opening pressure and build up the power slowly! A stronger spring is on order but is on a 4 week delivery.

More pics of the new drive shaft arrangement to follow shortly.

Andy

[andyowl]

The backfire pressure relief valve works! Trying to start the engine yesterday there were two backfires! I eventually got the engine running and although the mechanical noise is much reduced with the new universal joints the engine itself was very "rough". I looked at the "Supercharger" pressure gauge on the instrument panel and saw that it was showing zero even when I slowed and speeded up the engine. I realised that I had failed to reconnect the gauge to the manifold! Not only that but I had not even replaced the 1/8R (BSP) gauge connection and now had a 10mm hole in the inlet manifold! Not surprising therefore that it was difficult to start!

With the gauge reconnected the engine started happily with about -0.6bar in the manifold at 3 000 r/m.

I cannot get the engine to run at less than 2 500 r/m without slowly stopping. I think it is a carburettor  problem but my last experience of a SU carb was 40+ years ago on my supercharged Vauxhall Viva HB. Too long ago to remember! Through a local British car restorer friend I have found a man who knows about SU carbs and we have arranged to see him on Monday. His name is Alan Hill who is a specialist in restoring Morris Minors of all vintages. His business is called "Over the Hill Motors"! Neat huh?

Before fitting the manifold back on the car I made some "debris guards" as you can see in the pictures. I am worried that some part of the relief valve may fall off (despite using Locktite Threadlock on all the threads) and to prevent debris falling into the engine I thought some wire mesh might be a good idea.

The pictures show the new universal joints and their black rubber gaiters. I have thought about what might go wrong with this drive shaft and the most likely failure point seems to be the 16mm aluminium shaft on the blower adaptor. All the rest of the drive system is stainless or mild steel and well strong enough. If that ally shaft breaks I will have the drive shaft still rotating loose until the engine stops but potentially doing much damage. So I have left in place the intermediate bearing carrier that was fitted to try to reduce the bad vibration we found originally. I have simply taken out the bearing itself and left the surrounding ring to restrain the drive shaft if the ally blower shaft breaks. I hope I never find out whether it works but it is reassuring that it might not destroy the valve cover or the bulkhead!

More later!

Andy

[Anders Dinsen]

Hi Andy

I really enjoy reading your progress reports. Thanks also for sharing the funnier experiences! We've all tried that, so I don't feel bad laughing over the missed connection of the pressure gauge

About the mesh, on N/A engines, mesh is usually not recommended as it disturbs the airflow quite a bit. The mesh itself of course reduces the area through which the air flows, but more important it also creates quite a bit of turbulence, reducing airspeed. Mesh used to be popular on competition cars in front of carburettors instead of filters, but it's not a good idea - a proper filter is always better if you don't dare running without. I understand why you want it, but you're after power... I'd remove it and accept the risk. Besides, nuts don't just fall off if tightened correctly - and especially not when done with loctite

Keep up the good work and good luck with mr. Hill

/Anders

Just noticed one other thing: You don't need the heat insulating carb bases with your new setup. A simple paper gasket will do.

[andyowl]

You make good points about the undesirable side effects of the mesh. It will be very easy to remove when I have built up some confidence of the valve's reliability. I try to work on the principle of "Safe with one fault" rather like the concept of modern twin circuit braking systems.

The point about not needing the heat insulating spacers fitted below the inlet manifold is also well made. However heat build-up is still a potential problem with a blower as the compressing action of the blower itself will increase the temperature of the inlet mixture and, as another forum member mentioned, a water injection system to cool the inlet mixture is something quite close to the top of my development programme. If we start to inject water when the manifold pressure rises above atmospheric the engine is already working hard and should not complain about water in the fuel! I have already obtained a pressure switch to control the water injection and a vacuum switch for the blower lube oil system

wbw

Andy

[Spyros]

Andy,

This afternoon, I was looking at the pictures I took a week ago.
What types of brake pads do you use ?
Since already some times, I converted mine to EBC Green stuff

Regards

[andyowl]

Spyros wrote...
What types of brake pads do you use ?

It is some time ago and I will need to look back at the papers.

I don't remember at this moment, although Green Stuff has been recommended within the MECUK.

Andy

[andyowl]

I road tested Baggy Joe with the supercharger several times in the last week. The power increase feels HUGE! It was at least an hour before my knees stopped vibrating after the last run with the relief Valve opening pressure increased to about 0.8 bar. The car just flies and the "Blower Howl" makes my spine tingle. There are too many things happening at the same time to register them all. Wow!

There have been some problems however. During one of the first runs I could hear the Relief Valve ("RLV") opening with about 0.2 bar on the boost pressure gauge. I screwed down the spring a bit and the maximum boost pressure rose to 0.5bar. Feeling brave I gave it a last adjustment to the limit of the thread on the screw. 0.7bar was seen briefly but it started to drop back again. I looked at the neoprene valve seal and saw that it was dissolving! Despite the "material compatibility charts", which suggest that Neoprene is OK with unleaded gasoline, my neoprene foam gasket doesn't agree! As a short term fix I have made a very thin (0.05mm) brass disc to go between the foam and the manifold body. I hope this will reduce the contact between the gasoline and the rubber. I have not driven this solution yet.

At long last I have wired up the "Low Oil Pressure Warning Light". I had forgotten that I had done most of the work already and the hook up was very quick. The light itself is a 25mm lens where the cigar lighter normally sits. I can see it through the lower half of the steering wheel. It should be very visible if it lights up during an event. The oil pressure gauge also works but that requires "looking at" whereas the bright alarm light should attract attention. I hope it never needs to operate. The big worry is that the Shorrock blower consumes engine oil and it may not take long before the oil needs filling up again. In the heat of competition I may forget. The warning light is the last chance! What I really need is an oil LEVEL warning system.

Oil leaks in the nylon pipes feeding the oil pressure warning light switch and the blower lube oil line have also been a problem. I have used "Legris" pneumatic push-in fittings for over 30 years and found them very good if installed correctly. If air leaks out nobody really cares or noticed. Oil dripping out is a very different matter and easy to see especially if it results in smoke (Oh my God, its on fire!) or "What is that puddle on the floor" or worse "If your car leaks oil on the race track you will be banned and hated by everyone else". Not a good scenario! So I think I will have to re-pipe the system using compression fittings and/or use copper pipe. I checked in the RS catalogue last night and only Enots/Norgren compression fittings are listed. I loathed these fittings when I was a site engineer in the '60's and I don't feel much happier about them now. Apart from expensive USA Oil Industry compression fittings, anyone got any ideas on better systems? Wade and Simplifix were two competing brands 20 years ago but I haven't checked recently. Using copper would seem to be a good idea but I worry about fatigue cracking. Maybe I should be using oil-resistant rubber pipes?

Finally, I have now cut two large holes in the engine cover (yesterday) for the top of the SU carb vacuum dome and for the carb air inlet filter. Not the prettiest jigsaw job I ever did but the first AutoSolo event is tomorrow and the scrutineers will want an engine cover in place, even with two holes in it! Today is time to stick the fabric back on the engine cover, re-fit the interior trim (door cards and original twin passenger seat) as they are also required. Adding weight is not what I want to do!

Wish us luck.

The event (Sunday March 21st) is held at the Montgomery Lines parade ground, off Alison Road in Aldershot, Hampshire. Entry is free to spectators. All welcome. Come to the motorhome and stay for coffee! We should be there around 0830. Action starts after the driver's briefing at 10am. You may get press-ganged into helping to marshal!

Andy

[Spyros]

Hi Andy,
You are progressing so quickly !
I'm not sure to understand how you made the low pressure light work ?
Don't we have, by default, the sensor, however unwired ?

If I understand well, you needed an oil supply for the blower.
Did you took it from the oil pressure sensor or elsewere ?
Like I'm doing here ?


Regards

[andyowl]

If I understand your picture correctly you have drilled and tapped the hexagonal head of the bolt that holds the oil pressure transmitter in place. My bolt head now has an M5 thread and a M5/6mm Legris stud coupling in place. What thread is yours?

When I think about it my "bolt" is in fact the remains of the low oil pressure switch which did not work. They are not intended to be taken apart but I did it anyway! Because the "bolt" head was concave the biggest thread I could make was M5 but yours may be 1/8"? That seems much better than M5 which looks very fragile especially with steel braided hoses.

Your hoses are  "Aeroquip"?  They look very good. Very professional! "Proper Job". I must find a local source of those hoses and get some prices. Do you buy locally or via the internet? Expensive?

You have inspired me again!

The picture below is of the finished engine cover complete with the "Supercharged" badge. I didn't want to fix the badge until I was satisfied that the car was good enough to enter the first event of 2010! Superstious perhaps?

I will put a report on yesterday's AutoSolo event under the "Roll Cage Wanted" Thread.

Andy

[andyowl]

"Rolling Road" testing....

Yesterday we visited TCS Performance Ltd., near Bishop's Stortford, who provided the rolling road on which Baggy Joe was tested last August at the Practical Performance Car "RetroRide" event at Haynes Motor Museum.

[Just in case someone is not aware of what a "Rolling Road" does here goes. The driving wheels of the car rest on two large rollers which are connected to generators. The driver runs the engine and accelerates the rollers through 1st, 2nd, 3rd and 4th gears. He then lets the engine slow down to around 1,500rpm and opens the throttle fully. The generators provide the load on the engine and the computer records the electricity being produced and converts that to "Horse Power". A graph is plotted showing the Horse Power at the wheels, calculates the HP at the flywheel i.e. excluding the losses of the transmission and tyres, and several other things. Air/Fuel ratio is important to a blower system as having a mixture with too much air can cause the pistons to overheat and melt! He also records the inlet manifold pressure (the Blower Pressure) and several other things if you wish.]

In August last year the maximum Horse Power recorded was 88.6HP. (I need to convert this Imperial figure to metric! Do you prefer kW or something else?). We now know that a 1592cc Solara engine had been fitted by a previous owner and that it is in reasonably good condition.

Having now fitted the supercharger and got it running reasonably well, I felt that we should have some proper testing done to try to maximise the power and check those things that are difficult to do while the car is stationary such as how the mixture varies throughout the rev range and check the ignition system working with the engine under high speed/high load  conditions. All these can be done on the rolling road with the car stationary.

The car was reversed onto the rollers and strapped down very tight to prevent it coming off and running down the road! Sensors were added including a "Lambda" sensor to measure the Air/Fuel ratio and a thermocouple to measure the inlet air temperature. My blower pressure gauge was disconnected and the manifold pressure sensor connected in its place. There must also have been a connection to the ignition system (to monitor the engine speed) but I don't remember seeing it.

The photoghraph of the computer screen below showed some of the many graphs the computer produced. I will scan the paper graphs he provided shortly but the main interesting figures are shown. At the top right hand corner are the maximum Horse Powers recorded with 98.2HP being the HP as first tested and 112.7Hp the best we achieved after changing settings. So we gained 14.5HP just for changing the mixture, changing the ignition timing and closing the spark plug gaps down to 0.65mm! He charged £60 (about Euro65). So compared with August 2009 we have increased the power from 88.6 to 112.7 a gain of 24.1 HP or 27.3%.

I confess this is not quite as much as I had hoped for as the conventional wisdom suggests that 40% increase should be achievable. Still it feels a lot better and I would be very pleased to improve the driver's performance by 27% in four months!

More pictures and analysis to follow later.

Have a nice Easter!

Best wishes, Andy Owler

[andyowl]

Pre-Prescott update...

The Blower is working well although I continue to have problems keeping the universal joints from slipping on the drive shaft. The shaft is stainless steel (type 304) and is drilled to accept the cylindrical ends of the M6 grub screws. The grub screws are High Tensile steel and harder than the stainless. In consequence they distort the stainless and need constant tightening. Lockite helps but that makes them hard to remove or re-tighten. Maybe a second or third screw on each joint is worth trying. Proper "Woodruffe" keyways are the right answer but they are expensive to produce.

I have recently realised that the stainless drive shaft is not a genuine 16mm diameter but 5/8inch diameter. This is actually 15.875mm diameter. This gives some very undesirable clearence and may encourage the locking screws to vibrate loose.

As I think I have already reported, I have replaced the original simple universal joints with better quality "zero - backlash" joints. The problem was that they quoted 6 weeks delivery time for the 16mm version (before I knew about the 5/8inch shaft) and I settled for 20mm bore with 20/16mm reducing bushes. This has introduced even more potential "slop" but now does allow me to upgrade the drive shaft to a genuine 20.00mm diameter. Next step perhaps?

The special 16mm aluminium adapter bush that connects the second U/J to the blower drive flange was replaced yesterday with a 20mm steel version. Maybe it is my imagination but already there seems to be less mechanical growling when the blower is working hard.

And it does "work hard" when asked! In 1st gear there is barely enough time to read the tacho and change gear into 2nd before I exceed 5,500 rpm. I have set this "on the road" limit as the blower is not intended to go faster than 6,000 rpm. The U/Js are already limited to 4,000 rpm but they were the best I could find. On the public road I struggle to keep this lefthand drive car out of the hedge and on my side of the centre of the road at the same time as watching the tacho and noting the blower pressure.  Perhaps I need a data logger! Nearly 50 years of changing gear with my left hand takes some un-learning. More practice needed.

I took Baggy Joe to the Builder's Merchant ("Bricolage") today. They know me quite well but in Grey Baggy and our other cars but not in something low, growlly and very yellow! Caused quite a stir - they all came out to look! My "street credibility" went up several notches especially with the young lads! Pity I am too old to go "pulling the birds"!.

With Best wishes,

Andy

[Spyros]

I just watched again the video I recorded from inside your yellow beast : Wonderfull 
The sound is not as frightening on the video than in reality

Thanks a lot for the drive !

I'm just wondering : Will BaggyGrey suffer from the BaggyJoe daily usage ?

[andyowl]

Spyros wrote...Will BaggyGrey suffer from the BaggyJoe daily usage ?...

Baggy Joe is not really in "daily use". Although I do sometimes use him during the week he is not really suitable for going shopping everyday!

The Four point FIA seat belts are awkward to put on and the total lack of security in the boot makes it a worry to leave tools (or shopping) in there. I don't like going too far without the tool bag as we are still finding "teething problems". The heat build-up above the exhaust manifold when the engine is switched off makes me open the engine cover each time we stop for more than a few minutes. This is not a problem in competition but is a pain in "daily use". If I do not open the cover the heat cooks or melts any shopping . Not very practical!

During the Spyros drive yesterday the engine, under pressure, started to be erratic with the pressure rising and falling for no obvious reason. We checked the engine when we arrived at the lunch Pub and the inlet box had a lot of oil on the top. This usually means that the explosion relief valve is opening when it should not.

The last time this happened I found that the spring holding the valve closed had weakened and distorted, I assume due to the residual heat build-up after the engine is switched off. I replaced it with another, stronger, spring and it worked well at Prescott. But today I think it may be damaged again.

I need to re-build the relief valve with the spring outside the inlet box rather than inside. A question of time (as usual!). Our next event is on July 11th so I have a little time for some more development!

Spyros... Can the video be put on the 'net? I would like to see it too!

Andy

[Spyros]

Spyros... Can the video be put on the 'net? I would like to see it too!

Andy

I wouldn't have done it without your permission 

You'll see that I took some freedom to try to fit all together

http://www.youtube.com/watch?v=0-eyKVzi66M

I just hope that soon we will benefit from bbs tags to incorporate video directly in the posts