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Discussion Starter · #1 ·
I've just fitted the moss Supercharger kit to my 'B'. It is fitted onto a new fully balanced 1798cc engine and runs perfectly except for the following fault.

when under load the engine hesitates giving the impression of fuel starvation for a short period if the engine is blipped hard or when the throttle is re-applied following gearchanges.

I've had HIF44 carbs for years and know my way around one but I've never encounted this problem before and its got me baffled. The other cause may be to do with the supercharger but this is all new territory and I'm at a loss.

Any help would be much appreciated.

James
 

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Do you have an oxygen sensor?? other than that aint got a clue.Have you tried cleaning the carb (use to work on my bike :D )
 

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Discussion Starter · #3 ·
No oxygen sensor mate it's old technology :D

and the carb is brand new as is everything else on the engine. :roll:

The hesitation only lasts for seconds, almost like its leaning off and needs a bit of choke. under normal conditions and acceleration everything is 100%

It'll be going on the rollers soon but there's no point wasting cash on a rolling road session and spending most of it chasing minor faults instead of setting up the finite points.
 

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TRR Motorsport said:
No oxygen sensor mate it's old technology :D
Thought that would be the case. :doh
 

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I've asked the question as per your pm, not had a response as yet.
However, over on the MG Enthusiast BBS there is a section dedicated to Supercharging and there are owners with huge amounts of experience on these issues, in fact a thread is going on right now re mixture.
http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs
In fact s/c sub-forum here:
http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=tlist&subject=115

There are several things to take into account.

Heat - Moss do a heat shield but my discussions with the s/c expert in Australia he suggested that unless you had a poor grade stainless exhaust manifold heat should not affect performance but I know of at least one Moss s/c B that has a heat-shield and Moss also offer one now.

Oil leaks - another factor with increased compression, you may need to fit an additional tappet chest breather otherwise oil will find its way out everywhere and we had an issue on the BGT with it getting into the exhaust wrap. We later removed the exhaust wrap and just went with a heatshield.

Mixture - we run the BGT with a wide band sensor and I normally see 10.1 under acceleration, leaning out to 16.0 or so on normal load. It was necessary to get a boss welded on the exhaust manifold to mount the sensor.

Exhaust - have you fitted a larger bore exhaust? This will help with the higher s/c.

I'll keep you posted on further feedback. You should be looking at an easy 105-110bhp at teh rear wheels, though! But it is the torque increase that is so noticeable, and turns it into an excellent Q car!
 

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TRR Motorsport said:
I've just fitted the moss Supercharger kit to my 'B'. It is fitted onto a new fully balanced 1798cc engine and runs perfectly except for the following fault.

when under load the engine hesitates giving the impression of fuel starvation for a short period if the engine is blipped hard or when the throttle is re-applied following gearchanges.

I've had HIF44 carbs for years and know my way around one but I've never encounted this problem before and its got me baffled. The other cause may be to do with the supercharger but this is all new territory and I'm at a loss.

Any help would be much appreciated.

James
Sounds like you may have a carb ice problem this was an issue that we had to deal with on my first blown Range Rover. Check to see if the carb is getting to cold.Do you have any vac pipes connected to the manifold as you could be getting pressure fed into the carb. Most likely you have a carb problem go for the simple things first a new carb does not mean it is not faulty, LOOK at the fuel pump supply is it up to the job. The symtoms from here sound like fuel starvation. Too many unknowns for me, give me a phone so I can understand the way you have fitted the unit. 01877331099 :beerchug
 

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Discussion Starter · #7 ·
Problem solved.

The HIF44 supplied with the kit has two brass plugs fitted in place of the holes usually found on the underside of the dashpot. these are have two 1mm holes drilled in them. I found that the dashpot was dipping before lifting and this was causing the hesitation. I swapped the dashpot for the one from my kit-car (that has the tow 1/4" holes on the underside of the dashpot and it worked fine.

Obviously the vacuum on the supercharged engine is greater and thats why the holes in the dashpot are smaller but perhaps too small. I drilled one out to 1.5mm and tried it. A slight improvement so I drilled to other one out to 1.5mm again, better. I settled on 2mm dia holes and the problem has disapeared.

At least it's now driveable so now to get it on the rollers.

:beerchug
 
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