Don Terrill’s Speed-Talk

anybody running a rochester 4 barrel with nos 500 hp with 200 shot cheater plate

Just a few NHRA stock and super stock racers

As I look at it I have thought a Q-jet was not good for NOS at that carburetor favors the rear cylinders over the front. A fogger type system would work better IMO.

Does the carb loose some vacuum signal when the NO2 is shot into the manifold?

the carb isnt all that important while nitrous/fuel are being injected by a plate. someone probably has an accurate number, but amount of fuel/air a carb feeds while a plate is injecting nitrous drops by like 90%. i'd be more concerned with the quality of the manifold.

lefty o wrote: ↑Thu Sep 17, 2020 5:21 pm the carb isnt all that important while nitrous/fuel are being injected by a plate. someone probably has an accurate number, but amount of fuel/air a carb feeds while a plate is injecting nitrous drops by like 90%. i'd be more concerned with the quality of the manifold.

Although I don’t have the CFM data In front of me from our dyno on a back to back NOS/NA comparison, I doubt there is much reduction in the airflow demand when the engine is, “on the bottle”.

rustbucket79 wrote: ↑Thu Sep 17, 2020 9:02 pm

lefty o wrote: ↑Thu Sep 17, 2020 5:21 pm the carb isnt all that important while nitrous/fuel are being injected by a plate. someone probably has an accurate number, but amount of fuel/air a carb feeds while a plate is injecting nitrous drops by like 90%. i'd be more concerned with the quality of the manifold.

Although I don’t have the CFM data In front of me from our dyno on a back to back NOS/NA comparison, I doubt there is much reduction in the airflow demand when the engine is, “on the bottle”.

look at the bscf from the carb go to near nothing. the engine is still demanding "air", but the bulk of it is not coming form the carb.

So if that’s the case then the turbine should show a subsequent reduction when on the spray. We don’t have many dyno customers with nitrous, but I will definitely isolate the fuel solenoids from the carb supply turbine to see what happens.

Of course I am referring to cheater style kits, maybe an engine running multiple big kits don’t flow much through the throttle body, I’ve never been involved at that level.

lefty o wrote: ↑Thu Sep 17, 2020 5:21 pm but amount of fuel/air a carb feeds while a plate is injecting nitrous drops by like 90%.

That sounds like a 300 HP shot of nitrous is making 90% of the power. 333 HP total.

So I looked at 2 runs with a 540 BBC, NA and a 200ish shot of nitrous. The NA run drew 1087 CFM at peak, 957 CFM peak on the bottle. Looks to me about a 10 to 15% reduction in airflow through the carb on the bottle.

rocketracer380 wrote: ↑Tue Sep 15, 2020 1:54 pm anybody running a rochester 4 barrel with nos 500 hp with 200 shot cheater plate

https://www.facebook.com/HKMotorsportsD ... 8669910632

rustbucket79 wrote: ↑Fri Sep 18, 2020 8:48 pm So I looked at 2 runs with a 540 BBC, NA and a 200ish shot of nitrous. The NA run drew 1087 CFM at peak, 957 CFM peak on the bottle. Looks to me about a 10 to 15% reduction in airflow through the carb on the bottle.

Is there a carb jetting adjustment required when nitrous is used?

Not in the instance I mentioned