GSlender's Track Beeotch!

[gslender]

Ahh bummer! Despite what others might say I'm not sure moving the booster alone would do the trick. A under twin master set up would possibly be required.

Not sure what you mean - what's a under twin master set up ??

Looks like I have a bit more space to play with so may get away with a fabbed airbox that tapers at the back to allow fitment.

How so? Is that due to the different ITBs ??

G

[sailaholic]

Sorry missed a word out there in the phone. Under dash twin master cyclinder. Like race cars. One master for each circuit (front / rear) with a balance bar between the pedal and the two masters.

I believe zossy has one in his race car?

Yeah my length to throttle body end seems to be a bit shorter.


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[gslender]

Sorry missed a word out there in the phone. Under dash twin master cyclinder. Like race cars. One master for each circuit (front / rear) with a balance bar between the pedal and the two masters.

I believe zossy has one in his race car?

Ok, not 100% sure about that, and unsure of cost/need compared to just removing booster and using a larger diameter master. Need to think more and consider all options (including custom fab my own airbox etc). Nothing seems easy with the ITBs hey!

G

[sailaholic]

Yeah I wouldn't think it would be cheap. Will removing the booster make the assembly short enough to clear the end if the manifold though? Doesn't really look like it in the photo.

If you remove the booster you need a smaller diameter master to keep pedal pressure down.
Pressure = force / area. So with no booster the applied force is less (assuming constant pedal effort) so area needs to be less.

A smaller master though moved less fluid so you need a bigger pedal stroke to actuate the callipers which can become excessive.

This is why they run twin masters in unboosted applications, keeps the piston size down to keep the pedal effort down but keeps the fluid volume up as you effectively have double the stroke.

It's a semi common conversion for hot rods and old muscle cars where they don't have enough idle vacuum to provide consistent brakes. You can even buy kits for corvettes and similar with firewall adapter plates etc. sadly while it appears this had been done in mx5s it's far from common, but did come up in one of magpies itb / brake threads.

Matt R will tell you an mx5 is over assisted anyway and just drive it with out the booster because his charger has no booster. But the charger system was designed around a optional booster, the mx5 was not.

Can always go for a drive with the vac line to the booster blocked. I could see it being ok for a race car where braking points are going to be easily anticipated but have concerns on the street when your going to have cold pads and some kid jumps out in front of you etc etc.

All pad dependant of course, but I know my a1rms are noticeably slower to pull the car up first thing in the morning coming up to that first intersection etc.


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[gslender]

Maybe remote booster then?


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[Magpie]

You could have a new base plate made up that moves the air box forward.

Another solution is a remote or custom booster.
http://www.hydroboost.com.au/index.htm
http://www.mako.com.au/ibm_custom/search_html/Brake_Booster_Main_Page_92.htm
http://www.chasebays.com/product/universal-chase-bays/chase-bays-brake-booster-eliminator

You can also change the lever point on the brake pedal to increase the lever force to compensate a small amount when you remove the booster.

I did look at the issue and thought of a booster delete, but since it has been proven that the ITB's provide sufficient vacuum to run the booster mine is staying. Plus a pedal box puts me out of the time attack class that I will be competing in next year. There is also the issue of a pedal box conversion being street legal.

I also looked at doing a complete brake system redesign to work without a booster, but again not cost effective.

Disconnect the vacuum line and take the car for a drive a see what it could be like. MattR will chip in and say do it (booster delete), but Sailaholic has already covered this . I also agree that track and road driving are different animals.

I know MX5 Plus is working on a solution to allow longer trumpets and an air box for Jenvey's, stay tuned!

[gslender]

Thanks guys - the feedback is great and really appreciated.

Yeah I wouldn't think it would be cheap. Will removing the booster make the assembly short enough to clear the end if the manifold though? Doesn't really look like it in the photo.

I think so, but obviously after laying down $500 on this and getting it wrong, I'm even more careful about thinking what the next step should be.

If you remove the booster you need a smaller diameter master to keep pedal pressure down.
Pressure = force / area. So with no booster the applied force is less (assuming constant pedal effort) so area needs to be less.

A smaller master though moved less fluid so you need a bigger pedal stroke to actuate the callipers which can become excessive.

Ahh yes, it will need to be a smaller diam master - so I wonder how bad the stroke would be before that becomes a problem? Would that mean I get more resolution - ie foot pedal pressure/movement is now a finer amount of brake pressure (so regulating is easier / less knife edge) ??

You could have a new base plate made up that moves the air box forward.

Nah, the problem is that the #4 trumpet is just too close to the booster and I can't swing or insert the airbox to fit. I've actually got a blank base plate so I can make it fit anyway I want, but the issue is not being able to get around the #4 trumpet. As an example, if having the trumpet at all was optional, then I'd just run without it and all would be solved.

Another solution is a remote or custom booster.
http://www.hydroboost.com.au/index.htm
http://www.mako.com.au/ibm_custom/search_html/Brake_Booster_Main_Page_92.htm
http://www.chasebays.com/product/universal-chase-bays/chase-bays-brake-booster-eliminator

I'm thinking about this. If I leave the master in place, and relocate all the lines to the hot side and mount a remote booster, that would work and may not cost too much. The lines last time were only a few $$ so I can't seeing this being too much of a job.

You can also change the lever point on the brake pedal to increase the lever force to compensate a small amount when you remove the booster.

I'll have a look at that - can you remember what specifically is needed - ie make the lever longer or shorter, all depends on where the fulcrum point is right? I need to get my physics hat on...!! (oh boy and I failed the master diam size quiz earlier!!)

Disconnect the vacuum line and take the car for a drive a see what it could be like. MattR will chip in and say do it (booster delete), but Sailaholic has already covered this . I also agree that track and road driving are different animals.

I'll do this, just to at least rule this in or out (and whether I feel with a minor improvement I could live with it). I have two (2) NA6 so I can do a back to back too.

I know MX5 Plus is working on a solution to allow longer trumpets and an air box for Jenvey's, stay tuned!

Interested. Do you know more? Do tell... where is Danny?

[gslender]

Something like this is only $400 and might be smaller enough to fit everything. I'll have to do some measurements and check a few things.

[gslender]

Another option is to run with a remote booster... $500

[sailaholic]

Smaller master will give you extra travel yes but it should really be pressure that your modulating on.

With that said removing the booster will make the brakes much more linear and I know manga blue as said he always felt the NA brakes were over assisted.

The real issue with pedal travel comes back to can you move enough fluid in one stroke to get full brake actuation with out hitting the floor.

I also find a very long pedal harder to use with out lifting your heel of the floor and loosing a high degree of modulation control.

The math will tell you though. measure pedal travel with someone mashing the brake pedal (no need to have the car moving but do it running to have vacuum). Then work out the volume of fluid used. Then just solve for pedal travel with the new master syize and equal fluid volume.

Running with no trumpet is an option on #4 it will just hurt the VE of the cyclinder. Everything is a compromise just have to work out the best compromise for your $$ / effort / desired performance.


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[Magpie]

Call Jason and ask about the plus ITB possible solution. It is being developed for a race car that has a pedal box and is mainly a solution for using 100mm trumpets. However Jason is confident that it will translate into non race cars and work with a booster. Early days! Enough interest and it could be a stock Plus item

LOL on the $'s for a non working air box, I know that feeling! Oh to be not right hand drive

Interested in your above possible solution, a smaller booster. I have posted previously what the booster adds to the brake pressures. This info would help you choose an alternative.

[sailaholic]

The other option is to have a box like the mazdaspeed one. Box goes in first then you fit the trumpet afterward. You still need clearance but you don't need the fitting space.


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[plohl]

I am just putting it out here.... ITBs are way too much work.

G - Make something like this - I think Nigel has an AC tig now haha.



http://clubroadster.net/vb_forum/59-irtb-individual-runner-throttle-bodies/39898-toyota-ae101-ae111-4a-ge-miata-itb-resources.html#post734127

You wouldn't be able to have the space it has around cyl 4 but it gives enough room to clamp the box between the trumpets and the bodies. Fuel lines and that would have to moved.

[gslender]

Here's an interesting position - 949Racing offer a wilwood master cyclinder replacement and they recommend going from a smaller stock diameter (of 7/8ths) to a 1 inch - and state that yep, it makes for harder foot pressure, but state the reduced travel is a good thing!?

http://949racing.com/miata-wilwood-master-cylinder.aspx

I think my first step needs to be confirming if indeed the air-box can even be used with the booster removed - if so, then it is worth while investigating options to do that and how much room I need. If the air-box is still a struggle to make fit, then practically the only option is a custom box.

G

[sailaholic]

As I said most people find It easier to control brakes based on pedal pressure rather then travel. More pedal pressure means more feedback in simplistic terms so easier to tell almost enough brake from too much brake.

Also note that it's meant for bigger calipers which need more fluid. On a stock master this can mean excessive pedal travel.


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