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Supercharger Help


danielbrookes
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Hi,

I’ve been working on a supercharger project for my Zero.  It’s running on a Blacktop and I’ve spent ages researching, learning and now I’m stuck.

I made the bracket for the supercharger myself (with inspiration from posts on here so I really can’t take all the credit).  I also fabricated the inlet and outlet.

I am running an Eaton M62, it has a bypass valve and I have a throttle pre supercharger and the standard throttle in the GBS plenum post supercharger.

If I leave the outlet between the intercooler and plenum disconnected I have no issue; but clearly the supercharger isn’t providing boost.  I get no belt squeal and it sounds what I would say “normal”.

If I connect the supercharger to the plenum I get a very (and I mean very) loud mechanical squeal.  First I thought it was the belt or a pulley but I don’t understand how because disconnected from the plenum it works fine.

Any ideas? Just to clarify it’s a loud, really loud squeal.

Videos attached.  I am hoping it’s something daft.  I’ve already replaced the oil in the charger.  If the charger is broken that’s also fine but I want to be sure before I buy a new one.

 

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Cheers, it’s mostly his posts I’ve been following from here and a few other places . I would probably have taken it to him but with covid I couldn’t.  The thing that I don’t understand is if it was bearings then surely it would happen when not connected to plenum. Only thing I can think is vacuum increase. 

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I've always wondered why you'd have 2 throttles? The air only has one way in and one way out of the engine so there doesn't seem a good reason to have 2 in series.

If you just had a throttle and TPS upstream of the supercharger, wouldn't this be sufficient to control the airflow? 

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Hi, before I fitted a supercharger I had difficulty getting a decent idle as did my tuner. He blamed it on the volume of air in the plenum, I couldn’t get an IACV to work either.

Fast forward to me fitting a supercharger I opted for duel throttles to help with idle and throttle response, that’s my theory anyway based on the research I have done.  If you imagine a single throttle on the cold side of the charger there’s a large amount of air between it and the inlet. 

 

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7 minutes ago, danielbrookes said:

If you imagine a single throttle on the cold side of the charger there’s a large amount of air between it and the inlet. 

 

Yes, but compared to the displacement of the engine, it only equates to a few revolutions of the engine, which even at idle, is going to be a pretty small time interval to have any noticeable effect. 

Supercharged Jaguar V8's run a single throttle on the supercharger inlet. The path through the charge coolers is shorter because they're mounted either side of the charger, but it clearly works. 

Edited by richyb66
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Your probably right.  The other reason for me was the throttle I have has a TPS, it was easier to leave it where it is for wiring and I know it works with my ECU.

Ill see how I get on once I sort this damn noise out.  

Edited by danielbrookes
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No, I’m using the alternator and top idler pulley to adjust tension - although that’s on the opposite side of the engine to the charger.

Rich from Red Seven messaged me last night and he thinks it could be belt slip so belt tensioner could be a good shout.  It just sounds really loud for a belt and I also don’t understand why it’s only doing it when connected to plenum.

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Auto tensioner is a must. You'll struggle to get the belt tight enough without one and even if you did, if there's run out on any of the pulleys, the belt will squeal. In addition, a tensioner adds some damping effect between the charger and the engine to allow small variations in their speed. 

Consider one on a sprung arm if there's space. Compared to one built in to the pulley hub, you get a much greater range of movement meaning the belt length is less critical. Also the arms normally has a 1/2" square drive recess to move them making belt changes a doddle. 

P38 Range Rover V8 is a good example 

https://www.ebay.co.uk/itm/Range-Rover-P38-4-0L-4-6L-V8-Fan-Belt-Tensioner-Bearmach-Part-ERR6439/282617835102?fits=Plat_Gen%3AMK+II&epid=1134522428&hash=item41cd55ee5e:g:RawAAOSwrklU52jA

Mounting is via a single bolt and a cast lug on the back to prevent rotation against the belt tension. 

Edited by richyb66
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55 minutes ago, danielbrookes said:

It just sounds really loud for a belt and I also don’t understand why it’s only doing it when connected to plenum.

It's due to the inertia of the charger. Even disconnected there's a rotating mass that needs to be sped up and slowed down according to the engine speed. The drive between the two is just friction and if the belt tension isn't sufficient, it will slip on the pulleys. 

Big chargers on V8's often run a toothed belt because a multi vee won't transmit the power. In this case the drive is direct as the belt can't slip but it's essential to have some slack in the belt to take up shock loading. Usually this means being able to twist the belt 90 degrees at the centre of its longest length. 

Edited by richyb66
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2 minutes ago, richyb66 said:

It's due to the inertia of the charger. Even disconnected there's a rotating mass that needs to be sped up and slowed down according to the engine speed. The drive between the two is just friction and if the belt tension isn't sufficient, it will slip on the pulleys. 

Thanks for your help, gives me confidence that it’s belt slip and explains what’s happening. 

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Hey up Richy! Hope you’re well and keeping busy!

just to answer your dual tb query....it massively smooths out the power / torque curve.

somewhere in the mountains of photos, I’ve got a comparison graph someone did illustrating the difference....was going to do a comparison myself one day but never got round to it.

 

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Hi Rich, I'm god thanks. 

I guessed there must be some benefit but how are the throttles phased, do they both open at the same rate? The second throttle sounds more like a refinement to the system than an essential component which is why I wondered whether getting it to run with one might be a better starting point. 

With regard to flattening the torque curve, we both know adding 4 more cylinders is answer. 😉

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Ain’t no replacement for displacement!!
I suppose those huge V8 supercharger scoops with the 3 butterflies you see on drag strips are also a kind of pre-charger TB??

In essence, they both open at the same rate, although the precharger tb doesn’t close fully and needs to be a lot bigger then and post charger tb.

 

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