TB supercharger boost gauge

[jzr291]

Bonjour tous, With the supercharger I fitted came a greenish boost gauge stamped British Jaeger x26699. (Is the dial photoshopped and the gauge a new one not British Jaeger ?) Whatever it is, it reads 0 at the top center and on the left 0-14 VACUUM and on the right 0.-25 PRESSURE. I run in the engine carefully (300 kms since rebuild) and it usually reads about 8 vacuum and very rarely goes the needle to the right as I don't push the throttle pedal to the floor. Where can I find explanations on these readings, especially regarding torque and fuel consumption ? Can you compare them  with what happens with a carburettor, only the flow of mixture blown into the engine being bigger ? Thanks, Jean in Gascony

[joecurto@aol.com]

Either tha tgauge is not working or the supercharger is not producing boost, can you purchase an inexpensive Vacuum /Boost gauge ( one for a modern turbo will do or an old fashion  vacuum fuel pump test gauge)   and hook it into the system the gauge should be after the supercharger Joe Curto 718-762-7878 www.joecurto.com -----Original Message----- From: jeanvignau@orange.fr [mg-tabc] mg-tabc-noreply@yahoogroups.com> To: mg-tabc mg-tabc@yahoogroups.com> Sent: Fri, Sep 15, 2017 11:42 am Subject: [mg-tabc] TB supercharger boost gauge   Bonjour tous, With the supercharger I fitted came a greenish boost gauge stamped British Jaeger x26699. (Is the dial photoshopped and the gauge a new one not British Jaeger ?) Whatever it is, it reads 0 at the top center and on the left 0-14 VACUUM and on the right 0.-25 PRESSURE. I run in the engine carefully (300 kms since rebuild) and it usually reads about 8 vacuum and very rarely goes the needle to the right as I don't push the throttle pedal to the floor. Where can I find explanations on these readings, especially regarding torque and fuel consumption ? Can you compare them  with what happens with a carburettor, only the flow of mixture blown into the engine being bigger ? Thanks, Jean in Gascony #ygrps-yiv-112498640 #ygrps-yiv-112498640AOLMsgPart_2_3737737c-0bb4-4cf3-b40e-9a7bacb95b45 td{color:black;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mkp hr {border:1px solid #d8d8d8;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mkp #ygrps-yiv-112498640aolmail_hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mkp #ygrps-yiv-112498640aolmail_ads {margin-bottom:10px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mkp .ygrps-yiv-112498640aolmail_ad {padding:0 0;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mkp .ygrps-yiv-112498640aolmail_ad p {margin:0;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mkp .ygrps-yiv-112498640aolmail_ad a {color:#0000ff;text-decoration:none;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-sponsor #ygrps-yiv-112498640aolmail_ygrp-lc {font-family:Arial;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-sponsor #ygrps-yiv-112498640aolmail_ygrp-lc #ygrps-yiv-112498640aolmail_hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-sponsor #ygrps-yiv-112498640aolmail_ygrp-lc .ygrps-yiv-112498640aolmail_ad {margin-bottom:10px;padding:0 0;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_actions {font-family:Verdana;font-size:11px;padding:10px 0;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_activity {background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_activity span {font-weight:700;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_activity span:first-child {text-transform:uppercase;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_activity span a {color:#5085b6;text-decoration:none;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_activity span span {color:#ff7900;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_activity span .ygrps-yiv-112498640aolmail_underline {text-decoration:underline;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody .ygrps-yiv-112498640aolmail_attach {clear:both;display:table;font-family:Arial;font-size:12px;padding:10px 0;width:400px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody .ygrps-yiv-112498640aolmail_attach div a {text-decoration:none;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody .ygrps-yiv-112498640aolmail_attach img {border:none;padding-right:5px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody .ygrps-yiv-112498640aolmail_attach label {display:block;margin-bottom:5px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody .ygrps-yiv-112498640aolmail_attach label a {text-decoration:none;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody blockquote {margin:0 0 0 4px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody .ygrps-yiv-112498640aolmail_bold {font-family:Arial;font-size:13px;font-weight:700;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody .ygrps-yiv-112498640aolmail_bold a {text-decoration:none;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody dd.ygrps-yiv-112498640aolmail_last p a {font-family:Verdana;font-weight:700;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody dd.ygrps-yiv-112498640aolmail_last p span {margin-right:10px;font-family:Verdana;font-weight:700;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody dd.ygrps-yiv-112498640aolmail_last p span.ygrps-yiv-112498640aolmail_yshortcuts {margin-right:0;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div.ygrps-yiv-112498640aolmail_attach-table div div a {text-decoration:none;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div.ygrps-yiv-112498640aolmail_attach-table {width:400px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div.ygrps-yiv-112498640aolmail_file-title a, #ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div.ygrps-yiv-112498640aolmail_file-title a:active, #ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div.ygrps-yiv-112498640aolmail_file-title a:hover, #ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div.ygrps-yiv-112498640aolmail_file-title a:visited {text-decoration:none;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div.ygrps-yiv-112498640aolmail_photo-title a, #ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div.ygrps-yiv-112498640aolmail_photo-title a:active, #ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div.ygrps-yiv-112498640aolmail_photo-title a:hover, #ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div.ygrps-yiv-112498640aolmail_photo-title a:visited {text-decoration:none;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody div#ygrps-yiv-112498640aolmail_ygrp-mlmsg #ygrps-yiv-112498640aolmail_ygrp-msg p a span.ygrps-yiv-112498640aolmail_yshortcuts {font-family:Verdana;font-size:10px;font-weight:normal;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody .ygrps-yiv-112498640aolmail_green {color:#628c2a;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody .ygrps-yiv-112498640aolmail_MsoNormal {margin:0 0 0 0;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody o {font-size:0;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_photos div {float:left;width:72px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_photos div div {border:1px solid #666666;height:62px;overflow:hidden;width:62px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_photos div label {color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_reco-category {font-size:77%;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_reco-desc {font-size:77%;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody .ygrps-yiv-112498640aolmail_replbq {margin:4px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-actbar div a:first-child {margin-right:2px;padding-right:5px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mlmsg {font-size:13px;font-family:Arial, helvetica, clean, sans-serif;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mlmsg table {font-size:inherit;font:100%;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mlmsg select, #ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody input, #ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody textarea {font:99% Arial, Helvetica, clean, sans-serif;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mlmsg pre, #ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody code {font:115% monospace;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mlmsg * {line-height:1.22em;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-mlmsg #ygrps-yiv-112498640aolmail_logo {padding-bottom:10px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-msg p a {font-family:Verdana;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-msg p#ygrps-yiv-112498640aolmail_attach-count span {color:#1E66AE;font-weight:700;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-reco #ygrps-yiv-112498640aolmail_reco-head {color:#ff7900;font-weight:700;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-reco {margin-bottom:20px;padding:0px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-sponsor #ygrps-yiv-112498640aolmail_ov li a {font-size:130%;text-decoration:none;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-sponsor #ygrps-yiv-112498640aolmail_ov li {font-size:77%;list-style-type:square;padding:6px 0;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-sponsor #ygrps-yiv-112498640aolmail_ov ul {margin:0;padding:0 0 0 8px;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-text {font-family:Georgia;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-text p {margin:0 0 1em 0;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-text tt {font-size:120%;}#ygrps-yiv-112498640 .ygrps-yiv-112498640aolReplacedBody #ygrps-yiv-112498640aolmail_ygrp-vital ul li:last-child {border-right:none !important;}

[Ian Linton]

Bonjour Jean, I am at present still running in my Arnott supercharger on my pre-war MPJG engine. You can read more about it in the latest edition of TTT2. It is designed as a low pressure system and the relief valve is set at 5psi. In operation the Boost gauge only goes into the positive region when pulling up a long hill when it can reach just under 6psi. The same gauge has been tried on an XPAG with Shorrock supercharger and showed similar behaviour. I would suggest your gauge readings are quite normal. Kind regards, Ian Linton TA3120 Lewes, East Sussex, UK

On 15 September 2017 16:42:48 BST, "jeanvignau@orange.fr [mg-tabc]" mg-tabc-noreply@yahoogroups.com> wrote:   Bonjour à tous, With the supercharger I fitted came a greenish boost gauge stamped British Jaeger x26699. (Is the dial photoshopped and the gauge a new one not British Jaeger ?) Whatever it is, it reads 0 at the top center and on the left 0-14 VACUUM and on the right 0.-25 PRESSURE. I run in the engine carefully (300 kms since rebuild) and it usually reads about 8 vacuum and very rarely goes the needle to the right as I don't push the throttle pedal to the floor. Where can I find explanations on these readings, especially regarding torque and fuel consumption ? Can you compare them  with what happens with a carburettor, only the flow of mixture blown into the engine being bigger ? Thanks, Jean in Gascony

-- Sent from my Android device with K-9 Mail. Please excuse my brevity.

[Steve S]

Ensure you have the gauge connected to the manifold, not to the carburetor.

- Steve Simmons, TC8975

On September 15, 2017 8:42:52 AM "jeanvignau@orange.fr [mg-tabc]" mg-tabc-noreply@yahoogroups.com> wrote:

  Bonjour tous, With the supercharger I fitted came a greenish boost gauge stamped British Jaeger x26699. (Is the dial photoshopped and the gauge a new one not British Jaeger ?) Whatever it is, it reads 0 at the top center and on the left 0-14 VACUUM and on the right 0.-25 PRESSURE. I run in the engine carefully (300 kms since rebuild) and it usually reads about 8 vacuum and very rarely goes the needle to the right as I don't push the throttle pedal to the floor. Where can I find explanations on these readings, especially regarding torque and fuel consumption ? Can you compare them  with what happens with a carburettor, only the flow of mixture blown into the engine being bigger ? Thanks, Jean in Gascony

[Tim Bloomfield]

Good day Jean.  A healthy engine at idle will give around 18" hg vacuum (depending on cam etc.)  Your boost/vacuum gauge reading of 7 is probably 7 psig of vacuum which is about 14" hg vacuum.  This is very likely a good reading considering a rebuilt engine with a slightly over-driven supercharger and the fact bourdon tube gauges that indicate both vacuum and pressure are notoriously inaccurate.  I would like to know how much positive pressure you get at full throttle at 5000 rpm (once you have completely broken in your engine).  Also, I would be interested in your boost reading at part throttle cruise conditions at around 3000 or 3500 rpm.  There are technical articles in www.mg-tabc.org on supercharging that can give you an idea of power versus boost readings.  The old Moss brochures have some graphs in them too.Tim BloomfieldTB0613 (unblown) Sent from Yahoo Mail on Android

[Tim Bloomfield]

Sent from Yahoo Mail on Android

[Jean Vignau]

Merci tous, especially Graeme to whom I seem unable to answer via the Group.

 

You convinced me the readings are normal with the needle going to the right and starting to show boost when I get to 3,000 rpm.

The engine has done over 500 kms now and I ll try 4,000 for once soon to see and tell you, Tim. 5,000 later...

I ll look at the articles on s/charging in the mg-tabc.org.

 

Up to now, I am very happy with the Eaton, the TB going uphill as easily as on the flat in 5th gear, accelerates well in 5th from very low speeds

and mixes well with modern trafic at 3,500 where you get closer to the car in front.

Showing there is more power, there is a real engine brake you feel as soon as you lift your foot from the throttle pedal, even in 5th.

I may try a longer axle ratio to still lower the rpms. I should say it runs  about 6/700 lower now than before (3,500 against 4,0001/4,200)

and I d love to go down to 3,000. Anybody did it ?

Great improvement indeed.

 

What I am not happy with yet, also it improved when I turned the shims back to front, and I ll have to get used to it, is the VW steering.

The car is still wandering sometimes, probably according to the tarmac condition and I did not remember the TABC so much wind sensitive, is it really ?

Light when parking, all right, the steering is too much overgeared on our twisty country roads and keeps you very busy at the steering-wheel.

That will never change and it makes me unhappy yet with the VW conversion.

 

Jean and TB0592

 

 

[Jean Vignau]

Sun was out after 2 rainy days and I could not resist going out with the TB and try 4,000 rpm. With a good acceleration, the boost reads 5 pressure going left to 14 vaccuum and back to 5 pressure very fast when you change gear.

On a flat road, when you maintain 4,000 with the throttle just open, it reads 4 vaccuum that goes to 14 vaccuum when going downhill with no throttle.

It all looks quite logical.

 

The Eaton is said to work up to 6 lbs/sq. inch, leaving the margin from 5 to 6 for harder driving, or 5,000 rpm ?

 

Jean and TB0592

[Jean Vignau]

I have read (the part I understood of) your article and we can agree we d try improving the torque at the lowest possible engine speed.

More cc, a supercharger and a 5-speed gearbox is an easy way for aa amateur.

Jean and TB0592

[Graeme Louk]

Attachments :

[*][url=file:///C:\Users\Steve\AppData\Local\PG Offline 4\Attachments\\image1-88885.JPG]image1-88885.JPG[/url]

G'day Jean, I'm happy that you found the information helpful. Now your challenge is to let us all know what the boost is at 7000rpm. You need to see at least 20 pound before it'll get lively. In all seriousness though I would be very careful trying to lower your cruising rpm that low. The engine will reach a point where rpm is too low at cruising speed and will require that you get busy changing down every time you want to accelerate as the engine will tend to detonate slightly on acceleration. You can reduce the tendency by fitting vacuum advance so that light throttle/ lean cruising economy is good and ignition retards enough on opening the throttle to avoid detonation. Also run heavier oil in the SU dash pot to richen the air / fuel mixture on acceleration.