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MG TD TF 1500 - Front mounted SC

Have now run my completely overhauled XPAG together with a front mounted, direct driven, SC 12, meant to later be installed in my TD, currently run with an XPAW.

It gives 1.5 bar, as calculated, and I have made a belt gear in order to reduce the pressure. Intended to design the gear to give max 1.3 bar. However, would there be any disadvantages running it direct and drive carefully to make sure the pressure does not exceed 1.3 bar - maybe with a pressure relief valve, or will the higher speed of the CS reduce the efficiency in a considerable way?

I am not at all in a hurry and do not want to lug it and there are speed limits of 70 km/h almost everywhere I will use it. I just happen like the look of front mounted SCs.

The hose has to be reinforced with a spring internally, to prevent it from inflate at idling. Otherwise it seems to work well. As the SC will only be used for very short periods, I believe the hose for coolant will work. Will install a insulating plate between exhaust manifold and hose.

The pice of timber is for gauges for oil and manifold pressure.


YS Strom

I can’t answer your primary question but do have a comment tegarding your choice of hose. I would suggest getting hoses designed for turbo charger intercoolers

Bill Chasser
TD-4834
W A Chasser

Looks great! If I understand your 1.5 Bar to mean “absolute pressure” or 0.5 Bar over atmospheric (7.35 p.s.i.) then you have done well! Is your “Belt gear” a belt drive reduction? Lot’s of people use direct drive supercharging on XPAG’s, but usually only for racers as the front mounting requires lots of work with the body and blower drive. Your air delivery hoses must be fuel resistant, or they will soften and fail quite quickly. If you do go direct drive, be sure to incorporate a shear pin in the drive so if there is a problem with the blower, it is not torn to pieces by the engine.
A Peddicord


The sharp 90 deg. bends required makes it very difficult to find a suitable hose that does not inflate. Therefore, I am trying with the coolant hoses, that I intend to reinforce internally with springs, to prevent them from inflating. If it does not work, I might make a piping in steel with rubber connections.

The hoses are meant for use in engine bays, so I hope they are resistant to petroleum products, but it might be a good idea to put a piece in fuel for some time to make sure.

The 1.5 bar is an added 0.5 bar to the atmospheric pressure. I tried 1.5 bar with an Eaton SC once and blow the gasket. With solid copper gasket as now, will 1.5 be too much for an XPAG if max pressure is applied very rarely? Or can I interpret your comments Mr. Peddicord, as it is ok? It would also be interesting to know how much the timing should be preset.

A shear pin sounds like a good idea. It might solve the problem if one of the wedges is removed and only let the two stop screws opposite the wedge grove take the torque.

The reduction gear frame to be installed between radiator and engine is ready and made for two belts, but I have not yet decided if it is needed and if so, what ratio and pulley sizes will be required.

With the SC in place between grill and bumper, there will be 3 mm. space at each end of SC, so original spacers for the bumpers can be used.

As I see it now ?? no modifications of the body work will be required, apart from a new modified front apron and two bolt holes in the chassis.
YS Strom

Making a spring of 1.5 mm. steel wire in the lath and introducing it into the hose worked well, but unfortunately the coolant hose proved not to be fuel resistant, so I have to fit silicone hoses instead. A sample of the hose swelled 10 % just after a few hours in petrol.
YS Strom

The photo infers you got the boost without road testing? You might find you get much higher boost on the road. You need full throttle with load on the engine to see what boost you have.

When I fitted my first s/c in 1975 I calculated the gearing but when I revved the car in the driveway I got no boost. I then jacked up the rear wheels and ran it with left foot on the brake. I still only got a few psi boost so I fitted a smaller pulley to the s/c before track testing. On the track I got more boost than I wanted ... and that was at low revs and half throttle! I did one lap using only 4000rpm and part throttle before swapping back to the original pulley, which worked perfectly. (There must have been a flaw in my "left foot brake test".)

.5 bar (7 psi) above atmospheric sounds ok but you need to lower the compression ratio and retard the spark when supercharging. Fuel octane, boost, compression and spark advance must be such that you don't get detonation. Detonation will blow gaskets or worse!

Bob Schapel
R L Schapel

Schapel

Thank you for sharing your views and experiences reg. SCs.

The Eaton 45 I have in the car, geared to give only slightly more than 1.2 bar gives that pressure immediately when giving full throttle at any rev. even when parked. The inertia of the moving parts then gives the load. Your experience with the SC is very puzzling.

Intend to find or make a pressure relief valve and set it to open at 1.4 bar, to protect the engine. Have had a realy nasty experience with piston blow thru, probably due to sot formed by oil, dawn in via the valve stems. Below a very interesting link explaining this problem.

https://www.youtube.com/watch?v=soJea7xEt-8&feature=youtu.be

The set up engine and SC is now fitted with a 1.5 mm solid copper gasket, to allow for ground head and block and also a little for the SC. Timing is now set to mark at idling. Will also get high octane fuel.

Have tried running it with a bottle of fuel 1 m above the engine, but a pump is required to get enough pressure to get it working properly.
YS Strom

My thought and if I understand your statement is if you burned a piston it was from detonation or a lean fuel mixture

Bill Chasser
TD-4833
W A Chasser

Looks promising!

One advantage of front mounting is the intake of cool air. I have used thermocouples measuring temperatures in the exhaust as well as above and behind the exhaust manifold in regions of normal air intake. Under extreme conditions, exhaust has gotten to 1350F / 732C and under the bonnet temps can get up to 250F / 131C under extreme running. With boost, the hot air temps rise higher still which can lead to preignition. I'm currently assembling a S.Co.T. blower for our car and might try installing a thermocouple below the blower to satisfy my curiosity.

We've run a Moss Magnacharger for over a decade (max 5 psi steady boost) and always filled up with regular 87 octane gas without pinging*, and a lot of miles were at 230F / 110C water temp. Recoring radiator cut that way down, thank goodness. Old MG low compression ratios are good for supercharging.

This brings up another feature of front mount, intercooling, which is typically not practical with the typical MG blower. There are plenty of aluminum short radius elbows available for turbocharger intakes along with silicone couplings. Your hoses won't shed any heat, but then again, intercooling isn't a big deal in our cases. By the way, I used short radiator hoses on a Honda motorcycle carburetor swap onto a Honda car that has lasted 20 years.

If you try a relief, route it back into the intake or you'll be losing fuel discharging boost to outside air. It would be a real challenge to fabricate and, if you have boost jumping up and down under power, it'll likely create a bad throttle control issue. I have a Jackson Racing Eaton on a Honda that has a built in bypass but not to limit pressure, just the opposite, eliminate boost at low speed. I disabled it because it would add boost suddenly driving at low speeds, during shifts and highway cruising. At low speeds and shifting, it was just noticeable but actually made it difficult to cruise on the highway at a steady speed. And this is messing with boost at low power. You might just try a restricting orifice for the intake gasket behind carb to cut maximum air flow.

On the other hand, experience with my turbo diesel trucks is their boost relief opens and closes gently enough (approx 7 psi boost) and doesn't create a driving problem, but it is discharging air only to the atmosphere, no fuel.

* used a "Knock lite" for years with no indications of preignition.
JIM N

W A Chasser

The mixture gave a CO content just below what is allowed here - tested at different speeds and loads. There were a number of eroded spots and soot particles on all pistons, as described in the video and there was a leak along the stems that ceased when ground to size Volvo umbrella type seals were fitted. It seems that the soot particles on the pistons acted as a number of spark plugs - no pinging could be noticed - i.e. burning but no explosions.

Enclosed pics of the SC with homemade intake I am using now. First geared to 1.5 bar, but now reduced to + 1.2 bar. Pulley is split and can be chimsed for desired speed.

JIM N, Michigan

Very interesting findings about temperatures, but do you have pressurized cooling system as you get a water temp of 110 C?

Interesting that the water hose lasted so long for you. This will make me install the hoses I have and see how it works. The springs I installed tilted, so the hose inflated at idling. Therefore I introduced thin walled steel pipes in the hoses and used springs only in the bends. Could of coarse have used only pipes and bends.

Return the fuel mix from the relief valve to the inlet - before the SC - was a good idea. A whistle on the valve or a pressure sensor and a progressive audible signal would also do the job - if so you, always have the extra power for a shorter period should need arise .
.



YS Strom

Nonpressurized cooling system. It did boil antifreeze on a couple of hot days, but most of the time didn't. Replacing the radiator core with modern day soldered assembly made a world of difference. I'd like to think our new roller lifter cam with minimal overlap will promote more efficient, cooler running .

Our Honda (CRX convertible) intake hoses are straight and short. They turned hard but it is only an issue putting them on and talking them off. I've just been too lazy to replace them.

Image is not an "intercooled" but an "interheated" MG! The intake from carb to blower can be very cold. No sense in warming it up.


JIM N

Hi Y.S.

Perhaps the Eaton S/C has different characteristics from the Godfrey-Marshal I run. To this day I get almost no boost just revving at a standstill. The boost only shows up when under load. It could be the delay in the S.U. piston rising? I don't think it is the gauge.

What is your compression ratio? Boost of .5 bar (7.3 psi) should be ok if your compression ratio is standard and you have the ignition setting correct. (The factory tuning book quoted 6 psi in "stage 4".) Burn speed differences between modern fuel and 1950s fuel might be a factor too. It would be good to set the ignition on a "rolling road" so it suits your C.R. and boost. If you have a C.R. of 9 and run 7 psi boost, I am guessing you would want less than 30 degrees total advance.

There might be a thread in the archives about C.R. boost and ignition settings. If not, it might be a good thread to start and ask the question of other XPAGers.

Bob Schapel
R L Schapel


From Moss installation instructions for their Eaton superchargers.

Not for stage 4 thou

Set your cars timing at 1000rpm to 12 degrees BTDC
and verify that the total timing at 3500rpm stays
below 35 degrees. If you hear detonation or pinging
under acceleration, retard the timing 2 degrees.
Our vehicle’s advance curve measured out to the
following:

12 degrees @ 1000rpm
20 degrees @ 2000rpm
28 degrees @ 3000rpm
31 degrees @ 3500rpm

To be on the safe side I also think it is a good idea to set it to a bit below 30 deg.

https://www.moss-europe.co.uk/media/pdf/150-030_instructions.pdf

Here 4.5 CO is max allowed, but I think it would be good for the pistons with a bit richer.

Road tests will be made when the kit is completed and fitted to the XPAW in my TD.

Will come back later on some of the other issues.
YS Strom

Hi YS Ström,

Please send an email to me, Anders Dahlberg /Mariestad!

anders.dahlberg@cenva.se

And I will send some photos from my Dad's 1938 TA-

Special with a Volumex in the front of an XPAG Engine!

/Anders
Anders T Dahlberg

Mr Strom, My Eaton runs at 6psi and I use a 8.5:1 compression ratio. No problems with a standard cylinder head gasket, but I have had exhaust gaskets go.

I would recommend some sort of blower speed reduction - if you can keep the pressure down with your right foot, you're a better man than I am.

Very nice looking setup. I share the concern about hose material - hope it isn't a problem.

David
D A Provan

David and Bob

Very interesting to learn of your experiences.
The engine has only been run for a few minutes, so it has not been broken in which make compression tests irelevant yet, but seams to be around + 7 bar. With direct drive I get approx. 7.2 psi charge. Installing the gear frame made, with pulleys to give max. 6 psi is maybe a good idea to make the engine last a little longer. Instead of a light foot, a restrictor after the carb or on the throttle levers, or a pressure relief valve, might also do the job. Anyone who knows which will be the most energy efficient?

Your experience Bob with low pressure at idling and full throttle is very puzzling according to a friend of mine, with a lot of experience with of type SCs including Marchalls.

Jim

Should I interpret it as you have an antifreeze coolant with a boiling temp. higher than 100 C?

Anders

Address is on its way.

Bill

My burnt thru pistons, I believe, was due to sot formed from oil entering via the valve stems in combination with lean mixture, 4 %. There were no pinging and the youtube mentioned above gives an interesting description of the problem.
YS Strom

Image of frame for reduction gear to be bolted onto the engine.

YS Strom

Unpressurized 50/50 ethylene glycol/water mix boils right about 230F/110C, so it used to run that hot at 85 miles per hour on hot summer days, but having the radiator recored with the newer fully soldered core brought the temperatures down to more like 200F at extreme conditions.
JIM N

This thread was discussed between 14/02/2018 and 22/02/2018

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