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-Dan- · 8th June 2009, 19:44

Throttle-Body Setup *Section taken from GMC Motorsport*

Instead of going down the boost route, you could also go down the N/A route and still get pretty big power. This will come in the form of throttle-bodies.

Why fit multiple throttle bodies?

The purpose is to allow unrestricted flow of air to the cylinders, which is often a problem with standard inlet manifolds, plenum chambers when searching for maximum bhp. Having said this too many people jump to the conclusion that this what is holding their car back and want a throttle body kit. There is no point fiting throttle bodies on standard engine or on one that is only mildly tuned, as unless you have a high lift cam, head work, performance manifold and exhaust system, etc your engine will not be able to use the extra capacity of air you are throwing at it.

Sure it will go better but the money for a throttle body kit would give more power if you used it for the above mentioned parts, the only big benefit would be the fantastic sound that only throttle bodies give. It must be remebered when going for throttle bodies, the vast amount of other parts needed to fit them, the parts usually needed besides the throttle bodies themselfs are, inlet manifold, fuel rail, adaptors for trumpets, trumpets, air box, filter, throttle switch, linkage etc. For a rough guide most throttle body kits cost over £1000 plus fitting, plus you will need some form of programable management and the cost of programing time on the dyno.

Most relativley highly tuned engines do need throttle bodies, an example is the British Touring Car Championship, they are forced to use 1 single 64 mm throttle body and they still get over 280 bhp. I am noy trying to put anyone off the idea of multiple throttle bodies, just trying to make you aware that this is not be all and end all of serious tuning.

Another example is the full race Saxo VTS engine GMC Motorsport built for a racing series in Taiwan, this engine made 150 bhp at the wheels, OK a lot of money was spent to get this and would have been a lot cheaper to get this power by not doing certian things and using mulitple throttle bodies. The reason I mention this is that many people are worried about insurance and the fact the insurance engineer will be able to see the engine has been mwage tuned if he sees throttle bodies on it, whereas you can stiil have an enigne that looks reasonalbly standard from the outside and give good power on the standard throttle body.

So what is a throttle body set up worth over the standard single unit. Assuming the engine has been well sorted first, 15 bhp is usually the extra gained, on a basically standard engine, probably about 5 to 7 bhp. These comments are based on saxo engines, some engines have terrible inlet manifolds and plenum chambers, the Vauxhall Corsa 16 valve being one where far more could be expected.

Asuming you have decided to go for a mulitple throttle body set up, which throttle body do you specify. The best we have seen are the weber and Jenvey units and recently we have been favouring Jenvey more, as they do a far greater range of sizes and fitting applications, particularly short bodied units, which are a must when fitting to a front wheel drive car that has the induction system pointing to the bulkhead.

The reason I mention this is that just fitting a throttle body kit on any car, is only going to work well if certain rules are followed. The three main things you must achieve are an inlet length (from cylinder head to the end of the trumpets) of at least 15 inches, as if this is not achieved, all the power will be at very high revs and a reduction in low speed power.

Secondly, it is no good having a system that makes the trumpets nearer than 2 inches away from the bulkhead as this will restrict air flow and finally it is no good sucking hot air from the back of the engine. So unless you can fit an unrestricted air box that draws air from the front of the car you are wasting your time. If you were to fit a throttle body kit that does not achieve all these functions it is doubtful it will be of much if any advantage over the single one it replaces.

8th June 2009, 19:44	#9
-Dan- Established Member Join Date: Jul 2008 Location: Taunton, Somerset Posts: 1,182 Car(s): Millenium Falcon iTrader Score: 2 (100%)	Throttle-Body Setup Section taken from GMC Motorsport Instead of going down the boost route, you could also go down the N/A route and still get pretty big power. This will come in the form of throttle-bodies. Why fit multiple throttle bodies? The purpose is to allow unrestricted flow of air to the cylinders, which is often a problem with standard inlet manifolds, plenum chambers when searching for maximum bhp. Having said this too many people jump to the conclusion that this what is holding their car back and want a throttle body kit. There is no point fiting throttle bodies on standard engine or on one that is only mildly tuned, as unless you have a high lift cam, head work, performance manifold and exhaust system, etc your engine will not be able to use the extra capacity of air you are throwing at it. Sure it will go better but the money for a throttle body kit would give more power if you used it for the above mentioned parts, the only big benefit would be the fantastic sound that only throttle bodies give. It must be remebered when going for throttle bodies, the vast amount of other parts needed to fit them, the parts usually needed besides the throttle bodies themselfs are, inlet manifold, fuel rail, adaptors for trumpets, trumpets, air box, filter, throttle switch, linkage etc. For a rough guide most throttle body kits cost over £1000 plus fitting, plus you will need some form of programable management and the cost of programing time on the dyno. Most relativley highly tuned engines do need throttle bodies, an example is the British Touring Car Championship, they are forced to use 1 single 64 mm throttle body and they still get over 280 bhp. I am noy trying to put anyone off the idea of multiple throttle bodies, just trying to make you aware that this is not be all and end all of serious tuning. Another example is the full race Saxo VTS engine GMC Motorsport built for a racing series in Taiwan, this engine made 150 bhp at the wheels, OK a lot of money was spent to get this and would have been a lot cheaper to get this power by not doing certian things and using mulitple throttle bodies. The reason I mention this is that many people are worried about insurance and the fact the insurance engineer will be able to see the engine has been mwage tuned if he sees throttle bodies on it, whereas you can stiil have an enigne that looks reasonalbly standard from the outside and give good power on the standard throttle body. So what is a throttle body set up worth over the standard single unit. Assuming the engine has been well sorted first, 15 bhp is usually the extra gained, on a basically standard engine, probably about 5 to 7 bhp. These comments are based on saxo engines, some engines have terrible inlet manifolds and plenum chambers, the Vauxhall Corsa 16 valve being one where far more could be expected. Asuming you have decided to go for a mulitple throttle body set up, which throttle body do you specify. The best we have seen are the weber and Jenvey units and recently we have been favouring Jenvey more, as they do a far greater range of sizes and fitting applications, particularly short bodied units, which are a must when fitting to a front wheel drive car that has the induction system pointing to the bulkhead. The reason I mention this is that just fitting a throttle body kit on any car, is only going to work well if certain rules are followed. The three main things you must achieve are an inlet length (from cylinder head to the end of the trumpets) of at least 15 inches, as if this is not achieved, all the power will be at very high revs and a reduction in low speed power. Secondly, it is no good having a system that makes the trumpets nearer than 2 inches away from the bulkhead as this will restrict air flow and finally it is no good sucking hot air from the back of the engine. So unless you can fit an unrestricted air box that draws air from the front of the car you are wasting your time. If you were to fit a throttle body kit that does not achieve all these functions it is doubtful it will be of much if any advantage over the single one it replaces. Last edited by -Dan-; 2nd December 2009 at 22:28.