Motorsports Village

Dyno time
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Author:  Beretta [ Thu Nov 01, 2012 7:20 am ]
Post subject:  Re: Dyno time

nomad wrote:
Thanks for the explainations shrinker. For clarification I am running the BLP wide body 3 circuit metering blocks. These, for others information, have no idle tube in the main well.

On these metering blocks the intermidiate jet is smaller, .035 as opposed to the .040 plus, that I have seen in genuine Holley blocks. It must still be enough as I only run .118 BLP main jets.

I have tested both 16 hole and 12 hole booster inserts in my engine. I can tell you it seems to like the 12 hole better. I'm wondering if this is related somehow to your lesson above.

Bruce, Explain what difference the 12 hole compared to the 16 hole. What did you see??

Author:  nomad [ Thu Nov 01, 2012 7:29 am ]
Post subject:  Re: Dyno time

What you see with 12 hole and 16 hole is telling you that your engine likes larger drops and its for the reason I said above.

Kinda what I thought.

In a few weeks I hope to have my engine on the dyno to test between 12 and 16 holes. This way I can quantify the results and have a printout.

Author:  nomad [ Thu Nov 01, 2012 7:32 am ]
Post subject:  Re: Dyno time

Barry, 16 holes in my engine just didn't run as well. Going back to 12 perked the engine back up.

Author:  Milan.. [ Thu Nov 01, 2012 11:14 am ]
Post subject:  Re: Dyno time

Anyone know why 4150's dont have boosters (like dog leg type)with holes?? Then you could adjust how fuel is vaporized ?

Author:  Beretta [ Thu Nov 01, 2012 11:42 am ]
Post subject:  Re: Dyno time

Look at carb parts, down to boosters and on PG 1 there are some different types..

Author:  shrinker [ Thu Nov 29, 2012 4:47 pm ]
Post subject:  Re: Dyno time

Venturi tails have a definite optimum angle. There has been much research into what it is, there is a general angle that it can be made (6 to 8 degrees) and it will get it very very close to correct BUT the perfect angle for any venturi exit is effected by the entrance and the length of any straight section. Its also effected by obstructions to the exit. So it has to be found by experimentation.
The purpose of having a venturi tail is to recover the energy that was converted into a velocity increase (and thus lower pressure at the booster), back into pressure again. Thus CFM change etc.

When considering the throttle shaft it should be placed in a section that is increased in diameter compared to the venturi enough and at a distance so that its not a disturbance to the venturi tail above the shaft location.

The venturi tail does not have to be the same diameter as the entrance, the tail has finish somewhere obviously and after that its going to be a straight section to put the blade in. Once the tail is large enough its function basically disappears. The required length to achieve that is more that will fit under the bonnet =P~

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