Booster Signal

[mike laws]

[jmarkaudio]

The target is always moving because each combo is different. And in some cases the same engine with two seemingly identical carbs can have variations, the Holley HP Dominator castings are a prime example. I've built tunnel ram carbs and tested individually, an often one may need some idle circuit tuning different than the other. T-slot size and location varies, sometimes small amounts, sometimes significant, and is why a t-slot restriction is sometimes added. And casting porosity issues have been a part in some cases, hard to find or determine when it's a small amount. Because of the small amount of fuel metered a small air leak or cross between passages can make a noticeable difference. Billet components have mostly fixed those issues, allowing for calibrations to be consistent from one to the next on the same engine. With 4150's the baseplate t-slot size and position can vary greatly between manufacturers, and have a profound impact as in the Holley HP Dominators on idle tune and quality. Even a race car with a high stall, idle and transition metering can be the difference in a dark or black plug at launch when rich, or a stumble coming up on the throttle when lean. Having correct t-slot fuel amount and exposure goes a long way. Then throw in different fuels, even similar fuels but different brands can have an impact. Their vaporization curves can vary greatly even with the same or near octane ratings. Pro Stock was thrown that curve several years ago when NHRA decided Sonoco SR18 would be the new spec fuel over VP C25. As soon as I saw that I looked up the specs, and warned a few to look out for it on another forum. I think my words were overlooked until they started tearing up engines, partly due to the differences, partly to the inconsistency from batch to batch. All of this leads to why I have looked at finding better booster signal, as long as the fuel curve and proper atomization for the combination can be met a better booster signal should be ideal.

[Rat Bastid]

Thank you Mike and Mark. I’ve been leaning towards AD boosters on most anything on pump gas any more. I could be living in a fools paranoid, but I seem to get better results with them in TR and and single 4 stuff using “a old” intake manifolds.

[Right hand drive]

[mike laws]

[Right hand drive]

[rgalajda]

Rat Bastid wrote
" is there a relatively constant ratio between the IFR/IAB, or is it a moving target? "

Doug Schriefer, Barry Grant's tech specialist wrote
Another important point that addresses any carb tuning is that the idle-feed restrictor and the idle-air bleeds are intended to work in combination. This means that major changes to one bleed should be accompanied by a change to the other. For example, if you are planning to lean out the idle-feed restrictor by making it smaller, it's a good idea to increase the size of the idle-air bleed as well. This also leans out the idle circuit by adding more air. To enrich the idle circuit with an air bleed, you make it smaller. Schriefer's recommendation is to start your tuning exercise with the idle-air bleeds just because they're easier to access. If you are making major changes, a 0.001- to 0.002-inch change to the idle-feed restrictor should be matched with a 0.006- to 0.008-inch change to the idle-air bleeds.

[mike laws]

[mike laws]

[Right hand drive]