F1technical.net

Hiya,
I have been trying to workout why f1 teams ran a throttle body infront of the turbo as seen below in pic. Does anyone have and ideas or definitive answeres? It would be greatly appreciated.





thanx

Mick

Rules/regulations I'd imagine.

Try put your hand in front of a vacuum cleaners nozzle. Notice it will rev higher. That is because there is no mass, nothing, to suck. This is the reason why the throttle is positioned there, close the intake and you take away air from the turbo blades so the blades would spin easier and slow down less when the throttle is closed then you have less turbo lag. It also makes the turbo spin faster when the throttle is closed compared to the usual set up. You also won't need those annoying blow off valves Problem with this set up is is creates a lot of vacuum when the throttle is suddenly shut, so much vacuum that if you have the wrong bearing set-up, it will suck oil from the bearings.

The throttle valve is there to regulate the amount of air entering the engine. When burning gas, an optimum stoichiometric ratio of about 14.7:1 is required. The fuel quantity is controlled by the injectors, but there has to be some method of controlling how much air is entering the engine.

Same thing as on that BMW here on Renault V6T

Also, for the same reason Porsche and most bike racers use slide throttles. Eliminating the butterfly and it's shaft from the intake tract reduces turbulance and a major restriction. Here, with the throttle outside of the turbo, the pressurized air has no restriction other than the intercooler.

Still has to go through the same amount of air though. By the way, throttle in front of turbo was banned later in F1. On other motorsport series that do not ban such a set-up, you still don't see competitors using it. It seems that turbos are highly sensitive towards intake air flow and better to have it undisrupted.

Try put your hand in front of a vacuum cleaners nozzleNotice it will rev higher. That is because there is no mass, nothing, to suck. This is the reason why the throttle is positioned there, close the intake and you take away air from the turbo blades so the blades would spin easier and slow down less when the throttle is closed then you have less turbo lag. It also makes the turbo spin faster when the throttle is closed compared to the usual set up. You also won't need those annoying blow off valves Laughing Problem with this set up is is creates a lot of vacuum when the throttle is suddenly shut, so much vacuum that if you have the wrong bearing set-up, it will suck oil from the bearings.

that was along the lines of my thinking, lag reduction especially with the relatively primative turbo design.

Eliminating the butterfly and it's shaft from the intake tract reduces turbulance and a major restriction. Here, with the throttle outside of the turbo, the pressurized air has no restriction other than the intercooler.

this would make sense however they also run individual throttlebodies per intake as seen in this pic

All this stuff is in '1000bhp Grand Prix Cars'. I have it, but unfortunately I don't have it nearby!

well, Formula SAE still demanded that rule today.
any throttle device must be before the Turbo and restrictor.

first thought came into my mine is elimination of using blow off valve to prevent compressor surge... another than that I never thought of being an "anti-lag" purpose

The spatial velocity across the inducer plane will have an effect upon compressor efficiency. A small amount of swirl can actually increase efficiency but this will only be at one point on the map. Generally the effects are detrimental to efficiency and linear flow is desireable.

I have seen compressor efficiencies drop up to 20% on poorly designed compressor inlets during dyno testing, even though on the flowbench the inlets displayed minimal pressure drop. Flow visualisation and CFD analyses showed there to be a change in velocity across the plane of the inducer.

Or something like that...

When a throttle body or carb is placed in front of the turbo its called a draw through set up. When the turbo blows throw the TB or CARB its called a blow through set up. Blow throughs are far more efficaint and produce much more Hp with less lag. The only logical reason for having a draw through set up is if its required by the rules.

I have found some of the information I have. Most of these throttle bodies infront of the turbo were run inconjunction with normal throttle bodies next to the engine. They were added to reduce turbo lag buy inducing a partial vacuum in the manifold. This did two things: firstly, it allowed the turbo to spin longer and at a higher rpm because of the reduced pumping losses; secondly, the partial vacuum helped accelerate the air through the turbine, rather than just relying on the turbine to pull it through.

The main throttle bodies were retained because the response time to the drivers input was faster; imagine a fast moving mass of air moving through the turbine, the intercoolers and all the manifolds and trying to stop it by grabbing its tail - it takes a while to over come the momentum. It may only be a couple of 10ths of a second but it could just be the difference between catching a 1200hp slide and not! With the throttle bodies next to the engine, the cut off was instantaneous.

Thetwo may sound like they contradict each other but they managed the relative openings quite well enough to see some sizeable advantages, hence their wide spread addoption.

Definetly the slide throttles used to provide more power than the butterflies.
Everything changed with the electronic fuel injection.