we did back-to-back dyno runs way back in 2003, stock vs 61mm throttle body at Helix. no perceptible power or torque differences. My rig at the time was not a heavy breather (pre-head mod), although it had 15% pulley, header, exhaust, intake. We even did a full throttle run with the intake removed to peek in the TB to determine if the bfly was full open. It was and it was hairy.

 

Just installed a 59 TB, made by another company that I won't mention, and it made a really big difference. Assuming all TB's are the same, I can only imagine what a 63 would do....

'02 MCS with BMP air intake, John Cooper Works kit, and the new bigger throttle body.... my car is now fully capable of scaring the bejeezus out of me speedwise. An amazing additon the tb was, and one that I don't think enough people give credit to.

 

Dinan makes a 59.75mm throttlebody for the MCS that they do recommend to MINIs with JCW kit. Funny how the dyno tests done do not substantiate your perceived gains. I'd like to see more testing done to figure out under what setup will the rebored throttlebody and in what size will allow for gains that "ARE" measurable on dyno.

A larger bore throttlebody does not ensure any better performance. It's the total design fully tested that will tell the tale.

 

Actually, perceived performance can be quite different than measured performance in this case since a larger TB opens allows more air in at a given throttle angle. This results in a sensation of "better throttle response". A similar sensation could be enjoyed by sawing the gas pedal in half.

 

OMG, here comes "Operation Half Pedal".

 

The top half or the bottom half? I've got a hacksaw at the ready and am prepared to go....

 

no, no, no. Straight down the middle. That's how I just did mine...

 

So in other words it's worth the $300

 

 

I don’t doubt the validity of sensation when it comes to perceptions of enhanced performance. I just want to share some observations I’ve made of the supercharger intake duct (the throttle body mounts on one end) and some of the thoughts provoked by it in relation to changes made upstream. The duct varies both in shape and volume throughout its length. By nature of the duct’s convoluted shape and rough fitment of the supercharger end piece, laminar flow is disrupted; shear forces imposed and ellipse induced volume losses experienced. There is a section of the duct between the vent tubes boss and bypass valve insert that is almost 10% smaller than the stock throttle body opening. The venturi effect of this restriction would result in a pressure loss at that section. The transition from the duct to the supercharger has numerous form and fitment limitations that reduce the effective intake area to something close to the stock TB bore.

Because of the duct’s restrictions, I think changes made upstream would be negated. However, based on reports of other’s significant power deltas, I would think the duct despite its shortcomings is not a major bottleneck in the air needs for a 1.6-liter engine. As far as I can tell, pressure readings taken by others that show a decrease in pressure drop using this or that mod have been measured at a point closely behind the TB. If someone has taken before and after measurements further downstream, please chime in. The few dyno charts I’ve seen tend to support the relative ineffectiveness of TB or intake modifications. In regards to intakes, just going from a dirty to a clean filter makes a difference, so I tend to view dyno results of different intakes with a jaundiced eye.

Since this is a first posting on this forum I think a disclaimer is in order. This posting is not an attack on the M7 throttle body or any one’s satisfaction with it. The thread has evolved into a general discussion on throttle bodies so I felt an extra opinion might be OK. This is only a theory based on observations, sensations and didactical enquiry. Please put your pitchforks away before coming after me. :smile:
Keith

 

what's up with the text formatting being explicity displayed?


I agree about there being other restrictions offsetting most intake improvement gains (mainly the head, exhaust valves(, and it probably varies from car to car.

what is "ellipse induced volume loss"? a flow in-efficiency due to the tighter radius at the ellipse small ends?

 

Having started this thread I'd like to clarify my position by stating that the M7 throttle body seemed to or at least "felt" like it respond better. Unfortunately, I don't have any dyno numbers to back any performance gains, or losses.

Nonetheless, having spent the last few days doing dyno runs (as you can see from the following post towards the end of the second page of the thread https://www.northamericanmotoring.co...t=29218&page=2 ) I think we, as a MINI enthusiast community, need to start documenting each of the different modifications, much like Randy of M7 did with their thermostat and Andy of Ross-Tech does with his HAI mod, and putting up real numbers here or a web page linked to here.

AMPR

 

I'm sorry about the formatting display.

Once a perfect circle becomes distorted (ellipse) it loses volume (ellipsis of area) even though its perimeter measurement remains the same. I realize there is nothing regular about any of the oval like shapes in the duct. Perhaps those are incorrect terms to describe the effect shape has on volume. In those portions of the duct that have close to the same or even larger perimeter measurements as the TB, the internal area has been reduced by its bent shapes. The section that has a perimeter measurement smaller than the TB bore is easily identified as a constriction.
Keith

 

I think what k-huevo is describing is known as "hydraulic diameter". The idea is that and elipse may have the same perimeter as a circle, yet the flow through it becomes worse. Imagine putting a round hose into a vice and slowly tightening the jaws. As the jaws are tightened, the cross-sectional area of the pipe becomes less and less while the perimeter remains exactly the same. Eventually, the hose will be completely flat and there will be no flow through it. Hydraulic diameter is an expression used to represent the diameter of a round pipe that would have the same flow characteristics of the ellipse in question.

http://www.lmnoeng.com/PipeDuct.htm

 

Yes, very good analogy, thank you. I sectioned the duct into six pieces. I chose interior perimeter measurement (for the sake of simplicity) as a means of comparison between each section. The very odd shaped sections would require tracings on graph paper to get truly accurate comparative results.

Keith

 

Quick question:

If you install a T/B after other mods (MiniMania stage II + unichip), do you need to "remap" the chip for optimal performance?

 

I would love to know which size TB to get for a MCS with unichip, Dinan intake, 15%, Borla exhaust. Is there an ideal size? What if you p[lan on a header, cam and maybe a head? Does that make a difference?

 

We have tried 61,62,63 mm TB's and have settled on the 62 for most applications . We have installed them on what could be called a basic stage of modification cat back exhaust, some type of improved intake and 15 % pulley as well as our fully modded cars some of which have posted on here with big valve ported and polished heads,tuned header, port matched intakes , modded TB manifolds, 15% pulley, light flywheel , cam ,400 cc injectors, LSD, NOS etc. In both situations the car starts perfectly , idles at 800 rpm +/- 5 % , does not load up nor fowl spark plugs. As a matter of fact with the exception of a slightly lower exhaust note you really can't tell you have made a change from the stock 58 mm behavior wise . We will provide 63mm on special order but really haven't seen a need for that yet. Hope this provides some insight.

Randy
Team M7

www.m7tuning.com

 

So, No proof of ANY gains ? I will wait on the NEEDED DATA to be displayed

 

That means that I would be paying $600 plus shipping
bummer.. hope the prices fall soon. Or maybe not coz of the work involved.

 

The cost of the TB has been reduced to $ 350 . It is now shaped similar to a velocity stack and is 64 mm reducing to 62mm at the plate. This is the reason we describe it as a 64/62 TB. The core charge of $200 can be avoided of course by sending in your TB prior to us shipping you one. I know it is more down time for you but that is one way to keep your cash outlay lower. Feel free to ask anything else you may want to know.

Randy
M7 Tuning