First, a quick back story. My 1979 Mitsubishi Lancer originally came with a power assisted brakes by way of a Firewall mounted brake servo (aka. hydrovac). When I upgraded the engine, the original brake master and servo were in the way of the bigger carburetor so I switched to a custom brake system using an AP Lockheed remote servo mounted in the front of the car where the battery used to be.
I can't really complain about the performance of the Lockheed system. Aside from the fact that is has a cool name and looks really trick (always starts a conversation when people see the setup for the first time) it actually performs quite well. It's really powerful, I'd even call it overassisted. You get full braking power with just a light touch of the brake pedal. I've used it for almost 5 years already covering a whole lot of driving, mountain runs, high speed runs and even slalom racing once. The system is not perfect though. Because the brake servo is remote from the pedal, it lacks feel, or more accurately, there is no feel. The pedal acts more like an on/off switch, although with enough time and experience, knowing how the car will react when I step a certain amount, I was able to learn how to control it, but I never could use 100% of the brakes without locking it up. Another disadvantage was that you lose the split circuit safety of the original brake system, because the lockheed is fed by a single line in, if you have a leak anywhere you lose all brakes. I had a slight scare once when the bolt of a t-fitting came off and caused one of the brake pipes to crack. I've been paranoid about it ever since. Lastly, it's an old-tech system. Even 5 years ago, we were selling the things 'new old stock' coming out of decaying boxes. I have sold the last of our stocks of the things even the one I was keeping as a spare, so I figured if it were to break it would be best to look for a more modern alternative. Although, I must give the Lockheed some credit there, as long as they have clean brake fluid, they seem to last forever.
For a while, I had been researching alternative options that can apply to the car, given the tight space constraints of the engine. There is no modern version of the Lockheed remote servo, and even the smallest thinnest firewall mounted servo from a Japanese Kei car will still be too long for our application. There was always the option of switching to a down draft car and manifold to get the space back, but I felt that would be giving up on the side draft system that already works so well. Eventually, I started looking into Motorsports solutions. I was drawn in particular to the Tilton design dual master cylinder brake system that had a separate master for the front and rear brakes and a balance bar for adjustment and tuning. This is where I first encountered unassisted brakes. I had always thought that unassited brakes were reserved only for really really old cars that date back from before the brake booster/servo/hydrovac was invented. My 60 Chevy has manual brakes and they were terrible. I learned since then that a large number of race cars actually remove the servo and run unassited brakes for better control. Also learned that one of my favorite cars, the early Porsche 911 also did not have any brake servo up to some of the earlier 930 series. So based on the logic that most race cars and Porsche's are faster than my car and they run unassited brakes, I figured that would be the way to go.
I had originally planed on making my own version of the Tilton dual master cylinder system (of course we could always buy one, but there's no fun in that), but as I later decided that I don't really need the bias adjustability it offers over the increased cost and complexity of making one. The simpler the better, I figured as less parts would mean less areas to R&D and less places where things could possibly go wrong. I decided to pattern my brake system after the early Porsche 911 design which is basically a 2-pot master cylinder directly actuated by the pedal.
Master cylinders actually work like gears, with a ratio in relation to the piston in the brake caliper. The smaller master cylinder actually applies more pressure while the bigger it is means it moves more fluid (you also have to consider your brakes, discs have big pistons compared to the wheel cylinders in drums). The idea is to find the balance between having enough fluid volume to move your brakes within a fairly short stroke and having enough pressure. I understood this to mean that you use the smallest master you can get away with. According to the Porsche experts and racing people, a 20mm master cylinder was best for unssisted brake applications (any bigger and you'll probably want some assist already) so I figured that's a good place to start.
I dropped by favorite local parts place (Alabang Parts Center in Las Pinas) because those guys are patient with putting up with my strange requests for parts. I asked them to bring out all of the master cylinders they had on stock so I could choose one, considering both the 20mm bore size I needed and the need to get the shortest possible one to clear our engine mods. I settled with one for a '89 Lancer (yeah, funny to end up with a Mitsubishi part again) 13/16" = 20.3mm so close enough and it was also physically the stubbiest master the had available.
I fabricated an adaptor plate out of aluminum to mate it's 2-bolt flange to the 4-bolt hole in the cars firewall, which as you'll see in the pic, just barely clears the backing plate on the side draft carb.
I then fabricated a rod that connects the brake pedal to the master with an adjustable link so I had the option of adjusting pedal height and even preloading the master to shorten the pedal stroke if I wanted to. [no pics of that, I'm calling that a trade secret]
Took out all the complex brakes lines the old remote servo had and was left with a simple 'one for the front brakes, one for the rear brakes' setup. Still in the same armored copper pipe as before.
All done, there's a lot less clutter in the engine bay now.
I have to say that I like it a lot! In fact I've been driving the car all week just so I can keep testing it. Of course compared to any assisted setup it requires a lot more pressure to stop the car. There is nothing helping you so it's all muscle power. I would have to say it takes about 4 to 6 times more force from the right leg to stop the car. One noticeable difference is that there is now a progression in stopping. With a servo you just step, and the longer you leave your foot on the pedal the more stopping the car does. Without the servo you step and you have to step harder and harder to stop the car. It's not as bad as it seems though, as it's still quite easy to lock up the tires at speed if you step hard enough. I like it actually, and what I really like with the progression of the manual system is that it is very easy to modulated the brakes.
In order to use 100% of your braking system, you have to be able to brake at 'impending lockup' meaning any bit more pressure and you lock the wheels. On most cars I've driven with a brake assist this limit is very small, so you end up braking, locking the brakes, releasing, adding pressure, locking again and releasing, in order to balance the car at the limit. With the unassisted system, because of it's progression, it is SO easy to find that limit and keep it there, just perfect that you can hear the tires scrubbing just about to lock up but not locking up. I can imagine that this would be a great advantage at the track, which we may have the opportunity to test next year. For fast road use I am very satisfied.
In normal driving, the pedal does feel a lot harder than an assisted system. But after a bit of time to adjust to it, it feel normal and natural. City driving with stop and go traffic is easily handled without any more effort than if it had power assist.
In summary, I'm very happy with it. Pros: Great feel, excellent control and much simpler than the previous system. Cons: Very hard pedal (although I actually like that, it feels very reassuring to kick when your going for it) and more effort needed from the human to operate the car. So I don't think it's an mod for everybody and it probably won't be as easy if it was in a different application i.e. a much heavier car (remember our Lancer is like 750kg). I know a lot of people prefer over assisted systems because it makes the brake feel really strong, but really boosted pressure from the pedal does not make the actual brakes perform any better than if the pressure was manually supplied.
For a while, I had been researching alternative options that can apply to the car, given the tight space constraints of the engine. There is no modern version of the Lockheed remote servo, and even the smallest thinnest firewall mounted servo from a Japanese Kei car will still be too long for our application. There was always the option of switching to a down draft car and manifold to get the space back, but I felt that would be giving up on the side draft system that already works so well. Eventually, I started looking into Motorsports solutions. I was drawn in particular to the Tilton design dual master cylinder brake system that had a separate master for the front and rear brakes and a balance bar for adjustment and tuning. This is where I first encountered unassisted brakes. I had always thought that unassited brakes were reserved only for really really old cars that date back from before the brake booster/servo/hydrovac was invented. My 60 Chevy has manual brakes and they were terrible. I learned since then that a large number of race cars actually remove the servo and run unassited brakes for better control. Also learned that one of my favorite cars, the early Porsche 911 also did not have any brake servo up to some of the earlier 930 series. So based on the logic that most race cars and Porsche's are faster than my car and they run unassited brakes, I figured that would be the way to go.
I had originally planed on making my own version of the Tilton dual master cylinder system (of course we could always buy one, but there's no fun in that), but as I later decided that I don't really need the bias adjustability it offers over the increased cost and complexity of making one. The simpler the better, I figured as less parts would mean less areas to R&D and less places where things could possibly go wrong. I decided to pattern my brake system after the early Porsche 911 design which is basically a 2-pot master cylinder directly actuated by the pedal.
Master cylinders actually work like gears, with a ratio in relation to the piston in the brake caliper. The smaller master cylinder actually applies more pressure while the bigger it is means it moves more fluid (you also have to consider your brakes, discs have big pistons compared to the wheel cylinders in drums). The idea is to find the balance between having enough fluid volume to move your brakes within a fairly short stroke and having enough pressure. I understood this to mean that you use the smallest master you can get away with. According to the Porsche experts and racing people, a 20mm master cylinder was best for unssisted brake applications (any bigger and you'll probably want some assist already) so I figured that's a good place to start.
I dropped by favorite local parts place (Alabang Parts Center in Las Pinas) because those guys are patient with putting up with my strange requests for parts. I asked them to bring out all of the master cylinders they had on stock so I could choose one, considering both the 20mm bore size I needed and the need to get the shortest possible one to clear our engine mods. I settled with one for a '89 Lancer (yeah, funny to end up with a Mitsubishi part again) 13/16" = 20.3mm so close enough and it was also physically the stubbiest master the had available.
I fabricated an adaptor plate out of aluminum to mate it's 2-bolt flange to the 4-bolt hole in the cars firewall, which as you'll see in the pic, just barely clears the backing plate on the side draft carb.
I then fabricated a rod that connects the brake pedal to the master with an adjustable link so I had the option of adjusting pedal height and even preloading the master to shorten the pedal stroke if I wanted to. [no pics of that, I'm calling that a trade secret]
Took out all the complex brakes lines the old remote servo had and was left with a simple 'one for the front brakes, one for the rear brakes' setup. Still in the same armored copper pipe as before.
All done, there's a lot less clutter in the engine bay now.
Finally. The most important part. How does it perform?
I have to say that I like it a lot! In fact I've been driving the car all week just so I can keep testing it. Of course compared to any assisted setup it requires a lot more pressure to stop the car. There is nothing helping you so it's all muscle power. I would have to say it takes about 4 to 6 times more force from the right leg to stop the car. One noticeable difference is that there is now a progression in stopping. With a servo you just step, and the longer you leave your foot on the pedal the more stopping the car does. Without the servo you step and you have to step harder and harder to stop the car. It's not as bad as it seems though, as it's still quite easy to lock up the tires at speed if you step hard enough. I like it actually, and what I really like with the progression of the manual system is that it is very easy to modulated the brakes.
In order to use 100% of your braking system, you have to be able to brake at 'impending lockup' meaning any bit more pressure and you lock the wheels. On most cars I've driven with a brake assist this limit is very small, so you end up braking, locking the brakes, releasing, adding pressure, locking again and releasing, in order to balance the car at the limit. With the unassisted system, because of it's progression, it is SO easy to find that limit and keep it there, just perfect that you can hear the tires scrubbing just about to lock up but not locking up. I can imagine that this would be a great advantage at the track, which we may have the opportunity to test next year. For fast road use I am very satisfied.
In normal driving, the pedal does feel a lot harder than an assisted system. But after a bit of time to adjust to it, it feel normal and natural. City driving with stop and go traffic is easily handled without any more effort than if it had power assist.
In summary, I'm very happy with it. Pros: Great feel, excellent control and much simpler than the previous system. Cons: Very hard pedal (although I actually like that, it feels very reassuring to kick when your going for it) and more effort needed from the human to operate the car. So I don't think it's an mod for everybody and it probably won't be as easy if it was in a different application i.e. a much heavier car (remember our Lancer is like 750kg). I know a lot of people prefer over assisted systems because it makes the brake feel really strong, but really boosted pressure from the pedal does not make the actual brakes perform any better than if the pressure was manually supplied.
You're probably the only guy I've read so far who would willingly choose unassisted braking over assisted braking :P. But as you say, this works mainly on lighter cars, so this is probably perfect for someone to try on say an MGB, or a Caterham, or some kind of open-wheel car.
ReplyDeleteYes exactly!
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