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PostPosted: Wed Nov 29, 2017 11:29 am 
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Joined: Tue Dec 31, 2013 10:40 am
Posts: 307
Location: Huntsville, AL
R. J. Sorensen wrote:
David Vizard managed a 22% HP increase using a turbo, and a 41% HP increase using a Roots type, on a 1275 BMC. British Leyland put a turbo on the Metro and INCREASED the compression ratio (to help fuel efficiency)

Unlimited budget I suppose.

No mention of reliability. (Roots type used on drag racer)

Interestingly, venturi shape changes significantly over naturally aspirated, to make carbs boost sensitive as well as velocity sensitive.

RJS


So it made 100hp? Still probably made more torque than a Honda motor though.

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Brett W
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PostPosted: Wed Nov 29, 2017 3:36 pm 
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Joined: Sun Nov 08, 2009 12:58 pm
Posts: 452
Location: SJ
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Interestingly, venturi shape changes significantly over naturally aspirated, to make carbs boost sensitive as well as velocity sensitive.


It effects NA engines too. Look at a modern racing Holley. Booster shapes / positions, venturi shapes, etc. All flow more and produce as good or better jet signal than they do "stock". You can do the same with any carburetor. I saw someone thru-bore a SU, which produced a ton more cfm and using design cues from motorcycle carburetors, improved the jet signal. Win-win.

Interestingly enough, both NHRA Pro-Stock and NASCAR engines lost power going to fuel injection due to losing charge cooling caused by the fuel evaporating in a wet plenum. NASCAR gained most of it back via individual cylinder timing. The NHRA builders were using internal fuel rails in the manifold that had some 'leakage' to fog the plenum, and thus help gain back power. NHRA caught on to that and now they have to run external fuel rails. :D

In both cases, the rule makers specify the locations of the fuel injectors (in the intake runner), and aren't ideal for the applications.

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PostPosted: Wed Nov 29, 2017 7:10 pm 
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If I read the chart on turbo correctly, 99HP @ 6 PSI, 117 HP @ 10.25 PSI

Article indicates head gaskets were 1st casualty.

RJS


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PostPosted: Sat Dec 02, 2017 3:50 pm 
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Joined: Tue Dec 31, 2013 10:40 am
Posts: 307
Location: Huntsville, AL
R. J. Sorensen wrote:
If I read the chart on turbo correctly, 99HP @ 6 PSI, 117 HP @ 10.25 PSI

Article indicates head gaskets were 1st casualty.

RJS


The safety valve for the crankshaft? HAHA

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Brett W
Huntsville, AL


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PostPosted: Sat Dec 02, 2017 11:15 pm 
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Joined: Thu Dec 10, 2015 12:55 am
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I have an MGB with a Moss Supercharger. Drove it to the Runoffs in 2015 in Daytona and liked the drive so much I made my vacation that year a cross country drive from Tennessee to the Oregon Coast. Its been super reliable. It Only Used 1/2 Quart of oil in 3000 miles and got 24.75 MPG! I have sold a few other Superchargers for MG's. They are amazing and make power everywhere. Its a great cure for the horrible limitations of the head of the A and B series engine. One of my customers who purchased one from us summed it up nicely that you actually find you are far easier on the motor because you have so much power in the mid range you don't have to rev it to death. Though the dyno shows that for the supercharged Midget and MGA-MGB the power is still climbing at 6K with a stock cam and head when you have a supercharger. So you have to be carefull. On mine it wants to float the valves a bit before 6K because the motor is bone stock and still has the original single valve springs. THe one common British motor too weak on the bottom end for the supercharger is the Spitfire and Midget 1500. Moss has built a few protoypes but they break cranks and throw rods even on rebuild motors. Not good. The Triumph 1300 I think would be OK but 80% of the Spitfire street cars left are 1500's. But the 1275 Midgets hold up fine.

On the topic I have a friend who on multiple occations has put in a 4 temp sensors setup under the hood on an ITA STL Miata and the results are interesting. He has been able to redo the box and move the intake location to drop 20 degrees from the common way people do ITA Miatas. And he is still playing with it.

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FP Mazda Miata
IT7 RX7
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