Individual Throttle Bodies and Improved Airflow

[Dessertrunner]

I have been checking the race rules for my car and we are now allowed to install multiple throttle bodies, 1 per cylinder. As a result of this I want to look into what I can do to improve this area.
I am concerned that we don't have the height above the injector manifold to set it up in the normal way. Any suggestions would be greatly appricated.
Have read that 42mm is the size if I am chasing 56hp per cylinder. What does everone think. Looking at these units due to height.
http://www.efihardware.com/products/...hrottle-bodies
Tony

[svxfiles]

Originally Posted by Dessertrunner

I have been checking the race rules for my car and we are now allowed to install multiple throttle bodies, 1 per cylinder. As a result of this I want to look into what I can do to improve this area.
I am concerned that we don't have the height above the injector manifold to set it up in the normal way. Any suggestions would be greatly appricated.
Have read that 42mm is the size if I am chasing 56hp per cylinder. What does everone think. Looking at these units due to height.
http://www.efihardware.com/products/...hrottle-bodies
Tony

At the split between our "stacks" and the "spider " or our stock intake manifold , the runner opening is <1.8", or <45.72mm.
(For simpilicity I will use inches/feet as I am more comfortable with them)
PI X R²=2.5446879", X 6 = 15.268127 SQ/in S.A.
Our twin 60mm throttle bodies have two 2.5" bores as measured at the intake manifold.
That gives 9.8174686 SQ/in for the stock oppenings.
Obviously you can have alot more flow at 15 SQ/in, than you can at 9.8 SQ/in.
There is somethig to be said for lessening restricion.




But I have read that our TBs flow 900 CFM as they are...
More later.

[oab_au]

Originally Posted by Dessertrunner

I have been checking the race rules for my car and we are now allowed to install multiple throttle bodies, 1 per cylinder. As a result of this I want to look into what I can do to improve this area.
I am concerned that we don't have the height above the injector manifold to set it up in the normal way. Any suggestions would be greatly appricated.
Have read that 42mm is the size if I am chasing 56hp per cylinder. What does everone think. Looking at these units due to height.
http://www.efihardware.com/products/...hrottle-bodies
Tony

The rule change does open up the possibility's. I don't think there is much to be gained from having 6 throttle butterflys, it could be a real problem to arrange the throttle linkage and air cleaners.
There is a lot to be gained by reducing the length of the inlet tract, to allow it resonate at a higher rpm. This will allow the torque to be developed at a higher rpm, and develope more hp.
It would need a new manifold with shorter tracts, feeding off a larger plenum, using the original throttle bodies.

This is what has prevented the engine from using the upper rev range, as the torque peak will always stay at around the resonate rpm.

Harvey.

[TomsSVX]

They do have these though... Look like a high quality part, wonder how well the work in comparison with Nismo injectors

Tom

[Dessertrunner]

Harvey read in Autspeed or some where that there is a big improvement not having all clyinders calling for air at the same time. THe vacum is reduced by so much you have issues finding somewhere to get he vacum for the brakes. That said I was wondering if the way to go would be 2 SVX throttle bodies one for each bank or two from some other local car that would be cheap.
Tony

[TomsSVX]

Originally Posted by Dessertrunner

Harvey read in Autspeed or some where that there is a big improvement not having all clyinders calling for air at the same time. THe vacum is reduced by so much you have issues finding somewhere to get he vacum for the brakes. That said I was wondering if the way to go would be 2 SVX throttle bodies one for each bank or two from some other local car that would be cheap.
Tony

Not only that but you would need an engine management system capable of blending load readings. Considering the lack of vacuum present in any individual manifold it might read as the car being under load for a MAP based load sensor. So you would need to rely almost completely on TPS for idle and MAP for load after a certain throttle position is achieved. I tend to agree with Harvey in saying there is not going to be that much gained from ITB's and more to be found in a tuned manifold designed for higher RPMS

Tom

[Dessertrunner]

Have asked the company for more info on this one as I think it will work in better.
http://www.efihardware.com/products/...universal-45mm

Tony

[oab_au]

The engine in good standard trim, will achieve 106% Volumetric Efficiency. That is it will get 583cc of air in the cylinder, there is not much that will get more air in there, other than forced induction. Increasing the intake area will not make the cylinder draw more air in. I have seen a VE of 110% in simulation, that equates to 605cc of air. This is about all that we can achieve in the way of increasing the torque.
What we can do is to ensure that the engine can still induct the same amount of air, at a higher rpm in the shorter time. Longer duration cams will only help if the resonate rpm is raised to allow the cams to keep filling the cylinder, at the higher rpm, it will produce the HP that is needed.

As we can't increase the air pressure acting on the outside of the cylinder, we can increase the negative air pressure inside the cylinder to increase the flow. If the inlet, and exhaust tracts are shortened to resonate at the same higher rpm, the exhaust will provide a strong start to the inlet flow, and the inlet will cause a strong negative pressure inside the cylinder to induct the air.

Harvey.

[Dessertrunner]

Okay spoke to the guys that make the throttle bodies and they can build a unit like I first looked at that has 3 bodies on it. They are 20mm thick so I am going to try to sandwich them between the intake manifold and injector manifold. Then remove the existing throttle. My guess is that the existing manifold will give enough flow to satisify the need for air.
Tony

[oab_au]

Originally Posted by Dessertrunner

Okay spoke to the guys that make the throttle bodies and they can build a unit like I first looked at that has 3 bodies on it. They are 20mm thick so I am going to try to sandwich them between the intake manifold and injector manifold. Then remove the existing throttle. My guess is that the existing manifold will give enough flow to satisify the need for air.
Tony

What is that going to achieve? You will increase length the inlet tract, to lower the rpm that it will resonate at, and there will be no vacuum for the Fuel reg, brakes, purge, etc. How is it going to do the Idle control? Not .to mention the complication of setting all the throttle butterflys to work together.

Harvey.

[TomsSVX]

Originally Posted by oab_au

What is that going to achieve? You will increase length the inlet tract, to lower the rpm that it will resonate at, and there will be no vacuum for the Fuel reg, brakes, purge, etc. How is it going to do the Idle control? Not .to mention the complication of setting all the throttle butterflys to work together.

Harvey.

I am with you on this. Maintaining the stock manifold in any form with ITB's would be a step in the wrong direction. Play around with varying length velocity stacks and you are getting somehwere

Tom

[Dessertrunner]

Okay I get your point Harvey but I still think it is worth doing the excerise as regards individual throttle bodies. As to if I use the top manifold I will see. I need to decide if I am going to use ram pipes or not.
Any way sounds like there is a lot of negitive as to the whole thing so I will not bother keeping you guys updated with posting.
Tony

[AppStateSVX]

i think it's a great idea.

i've never heard of a motor not benefiting from them.

the bmw s54 comes with them stock

[subbieatnz]

I like the thought of ITBs.
Im intrested in updates on this

[Dessertrunner]

Originally Posted by AppStateSVX

i think it's a great idea.

i've never heard of a motor not benefiting from them.

the bmw s54 comes with them stock

I am in total agreement with your statement on this and that's why its worth trying.
Tony