Back on task... I fabbed up this nifty air cylinder to apply pressure at a certain PSI to the brake pedal. It is a 1.5" cylinder, so the pedal force (in lbs) is 1.77 times the input pressure. There is a petcock bleed off on the back side of the air inlet, so I can restrict the air and vent to dial in the desired air pressure.
With this tool I was able to set the input air pressure to a certain value and then take caliper readings with the engine off, then on. The input air pressures are pretty accurate (+/- 1 psi) due the good gauge resolution. The caliper pressures are probably +/- 25 psi due to the gauge resolution and the lowest mark on the caliper pressure gauge is 200 psi. It looks like that from 40 to 80 psi the booster is adding about 1000 psi to the caliper pressure. From 0 to around 40 psi input pressure, the vacuum assist probably is variable, but the shape of the curve is unknown.
code:
Caliper Pressure Readings for Stock 88 Booster:
Input Air Pedal Force Engine Off Engine On Vacuum Assist (psi) (lbs) Caliper (psi) Caliper (psi) (psi)
Originally posted by fieroguru: I figured that the pedal play was coming from internal to the booster - where the slop was between the banjo and booster/master pushrod assembly. To check this, I made this little tool...
the OE booster is adjustable. Check to see if the S10 booster is also adjustable... Likely it is then adjust it. Many aftermarket boosters needs adjusting and may need special tools to adjust w/o wrecking diaphragm. Rodney needs to ask his vendor. See service manual, booster section.
quote
Originally posted by Austrian Import: This doesn't actually increase clamping force.
Yes, it does... Simple math: Input Pressure at MC x MC/caliper ratio = clamping force.
Change pedal feel? Yes. Changing feel is a Good/Bad thing? It's Driver's preference...
quote
Originally posted by fieroguru: Pressure time! - all these readings are for the stock 88 booster setup. Back on task...
22P book says all Fiero uses same booster. see page J-4 thru J-8.
Just ignore 20 row and average vac assist column... IE 975psi. Why? vacuum assist at constant vacuum source get you X amount of assistance... (All test at idle but need a vac gauge to make sure engine vacuum is fairly steady. )
I'm not sure if the math/method is right or wrong but should still see OE vs. S10 if you to same steps.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Goes a bit against what I experienced driving purpose built GTR racecars, such as a Panoz, but if the general consesus is more assist = more stopping power, I'll go with it.
I'll ask the engineer that set up the racecar why he decided to remove the boost and upgrade the brakes. Now I'm quite curious.
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01:36 AM
Rodney Member
Posts: 4715 From: Caledonia, WI USA Registered: Feb 2000
Goes a bit against what I experienced driving purpose built GTR racecars, such as a Panoz, but if the general consesus is more assist = more stopping power, I'll go with it.
I'll ask the engineer that set up the racecar why he decided to remove the boost and upgrade the brakes. Now I'm quite curious.
We should all put on 18 inch or larger rims and upgrade to really huge rotors and calipers. How can you compare a race car to a stock Fiero? Talk about apples to oranges. I mean really. That race car probably even weighs less than a Fiero.
------------------ Rodney Dickman
Fiero Parts And Acc's Web Page: All new web page!:www.rodneydickman.com Rodney Dickman's Fiero accessories 7604 Treeview Drive Caledonia, WI 53108 Phone/Fax (262) 835-9575
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06:22 AM
Austrian Import Member
Posts: 3919 From: Monterey, CA Registered: Feb 2007
I was comparing the street Panoz to the race car Panoz. I wouldn't dream of putting a Fiero anywhere in that comparison.
Since I know now I'm wrong, I'm curious to see phase 2 of this test. Actual stopping distance before and after the booster upgrade. First with the same pedal effort, then absolute distance regardless o pedal effort.
If it improves I'll sign up to buy a Rodney booster. I'd be willing to give up some modulation for reduced stopping distance.
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01:19 PM
Firefighter Member
Posts: 1407 From: Southold, New York, USA Registered: Nov 2004
Is this all over complicating a relatively simple project? The S-10 brake booster idea came from Phil in Connecticut about 5 years ago. If you can successfully change the spark plugs in the V6, you can do the brake booster swap. Or have I missed a point in all those photos? A $100 rebuilt S-10 booster, some basic mechanical skill and the Fiero will actually stop.
If you buy a pre-made booster, yes it's so easy a caveman can do it (sorry, I just love that line). I believe the point here is safety. To you and others on the road. It's no joke when you are messing with the braking system. Rodney has a product in which liability can be a huge factor if someone gets killed or hurt from this brake upgrade. Now it's my opinion it's there own damn fault because they decided to do the upgrade in the first place and should know the risks that anyone takes modifying the brake system, but that's not the way it works legally, of course.
It's also a test of exactly how effective the bigger booster is...putting some data and numbers behind an upgrade that been around for a few years now, as stated.
[This message has been edited by mattwa (edited 03-27-2012).]
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02:47 PM
Msaby Member
Posts: 292 From: Allentown, PA 18104 Registered: Sep 2001
Just a quick question here. Is the booster you are testing an S10 booster or is this a custom built booster for the fiero? I ask this because the data you are compiling may be different from an S10 booster if this is in fact a custom built one.
Thanks Mike
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03:06 PM
PFF
System Bot
imacflier Member
Posts: 946 From: Levittown, NY, USA Registered: Apr 2002
I was comparing the street Panoz to the race car Panoz. I wouldn't dream of putting a Fiero anywhere in that comparison.
Since I know now I'm wrong, I'm curious to see phase 2 of this test. Actual stopping distance before and after the booster upgrade. First with the same pedal effort, then absolute distance regardless o pedal effort.
If it improves I'll sign up to buy a Rodney booster. I'd be willing to give up some modulation for reduced stopping distance.
Austrian Import,
OK, if you can already lock up your stock brakes, then absolute stopping distance will not be improved (since that is determined by tire and road interface) unless you are able to better modulate your brakes. Most people will modulate better if they do not have to 'stand' on the brakes to reach the edge of lockup and the improved modulation may result in reduced stopping distance.
Just a quick question here. Is the booster you are testing an S10 booster or is this a custom built booster for the fiero? I ask this because the data you are compiling may be different from an S10 booster if this is in fact a custom built one.
Thanks Mike
Please correct me if I'm wrong but Rodney's booster is the same as the S10 booster except it has the correct length and size pushrod for use in the Fiero, I don't think there is any internal differences other then they are "brand new" with a powder coated surface and not refurbished.
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04:52 PM
Austrian Import Member
Posts: 3919 From: Monterey, CA Registered: Feb 2007
If I undestand the way it works correctly, then for a given input x the brake will now apply pressure y, it pretty much magnifies my input by a certain multiplier. So logic would say now that minute changes in pedal pressure will now result in much larger changes in clamping pressure on the pads. Unless there is a way to compensate for this by allowing the brake pedal to travel more.
So let's say if you're trail braking to get the car to rotate, which requires very little brake pressure, since all you want to do is to transfer the weight forward off the rear wheels, applying more pressure than that will either slow the car down too much, or worse transfer too much weight forward and the back will spin out. Trail braking is very difficult (for me) to begin with, as if feels like you barely modulate the brake. (I visualize it as moving the pedal less than a millimeter, no clue how much I actually move it, as I'm focusing on other stuff.)
More common situation, easier to explain, same concept: I have the same issue with modulating the gas pedal on a rear wheel drive to hold the perfect slide. (not enough the car will straighten out, too much and the car will spin out.)
Hope that explains it better.
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06:48 PM
Austrian Import Member
Posts: 3919 From: Monterey, CA Registered: Feb 2007
OK, if you can already lock up your stock brakes, then absolute stopping distance will not be improved (since that is determined by tire and road interface) unless you are able to better modulate your brakes. Most people will modulate better if they do not have to 'stand' on the brakes to reach the edge of lockup and the improved modulation may result in reduced stopping distance.
Why would you expect loss of modulation?
Larry
In my experience one can lock up the stock brakes (as you said tires really) on a stock Fiero if the tires aren't grippy enough. On my old tires I had a hard time doing that, but I've done it in a panic stop on the paddock before. Now that I switched to 180 thread wear 18" 235mm tires, I'm not sure if I can lock up the tires anymore. (haven't tried, don't want to risk flat spotting the tires on purpose. - I'm sure I'll do it without meaning to some time, if possible. )
Now threshold breaking is really hard. Especially in a car without ABS. In a car with ABS it's easy to practice: squeeze (like a sponge) the brakes as hard as you can, until the ABS locks up. Now repeat, and ease off the brakes until the moment right before the ABS takes over. That's maximum braking (for the tires, brakes, suspension) for that given car. I tried practicing this on the Fiero (on my old set of tires) and it's quite difficult as there is no ABS like warning before lockup. From what I remember there is very little modulation before the point I feel lockup occurs. (I try doing this on wet surfaces as I'm cheap and it saves my tires)
Now if the S-10 booster Rodney makes allows for this at less pedal pressure, that would probably make life easier. I'd be willing to give that a shot.
Hope it makes more sense now why I said in my original post that it doesn't improve brakes. I realize I didn't explain it quite well. I'm still trying to find the words to explain what I was trying to convey.
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06:59 PM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
Is this all over complicating a relatively simple project? The S-10 brake booster idea came from Phil in Connecticut about 5 years ago. If you can successfully change the spark plugs in the V6, you can do the brake booster swap. Or have I missed a point in all those photos? A $100 rebuilt S-10 booster, some basic mechanical skill and the Fiero will actually stop.
Everyone know this swap improves braking, this thread is more about understanding why, trying to quantify how much and seeing if there any other changes that Rodney could implement in his custom booster (like the proper length banjo) to make the upgrade better match the overall fitment and function of the fiero system.
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09:20 PM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
I picked up a smaller gauge (400 psi) to get more accurate readings of the caliper pressures with the engine off and changed the testing process. Before, I was checking each pressure with the engine off/engine on. But today I did all the testing with the engine off starting with the lowest input values going to the largest. Then turned the car on and did the same. There is some difference in the previous readings vs. these, but I think these are more accurate. With this data you can see the approximate rate of increase in caliper pressure with the rate of increase of the pedal pressure. You can also see some changes in pedal pressure didn't make a significant change in caliper pressure... this might be a resolution issue with the 3000 psi gauge so using a 1500 psi one would be more ideal.
Before I pulled the stock fiero booster, I removed the brake master, added my pushrod stop tool and took a pedal play measurement - ended up with 9/32" of free pedal movement before taking up the internal clearances within the fiero booster. (Fast forward - the S10 booster has 7/16", or 5/32" more than the fiero, internal takeup using the same process of measurement).
I used a pipe to touch the pedal, then marked the taped end against the edge of the L bracket on the floor. Scribed a mark with the pedal full retracted and pushed forward as far as it would go. Then measure the difference.
Once I had the stock booster removed, it was a matter of making the necessary clearance dents. My tools of choice were mini sledge and a piece of 2x2 wood with the end slightly rounded:
If your put a piece of blue painters tape along the bend in the sheet metal as shown (bend is along the right edge of the tape), that is the general area needing to be clearanced:
After a test fit, I also needed to scrap away some seam sealer and massage this area as well:
None of this massaging needs to be more than 1/4" of metal movement. I preferred to do multiple small hammer sessions followed by a test fit to end up with the smallest needed rework of the area. Then gave the area a coat of semi-gloss rustoleum.
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09:57 PM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
As I was connecting the banjo with the booster mounted on the other side, the banjo needed to be pushed into the booster by about 1/8 to 3/16" to line up with the brake pedal stud.
I didn't remember noticing this slight preload with the 88 booster, so I will check the length of the banjo on the booster removed vs. the one from the shelf that matched the Rodney booster banjo. I also have 3 other 88's in the drive/garage and will check one or two of them to see if the stock banjo has this slight preload.
Even with this initial preloading of the banjo, the measured pedal movement (brake master pushrod stop installed) was 7/16" and 5/32" more than with the 88 booster
Depending on when I get home on Wednesday, I might be able to finish up the installation/testing and take this car for a test drive.
[This message has been edited by fieroguru (edited 03-27-2012).]
Just ignore 20 row and average vac assist column... IE 975psi. Why? vacuum assist at constant vacuum source get you X amount of assistance... (All test at idle but need a vac gauge to make sure engine vacuum is fairly steady. )
Nope... I'm trying to find the right math. ___
This will help trouble shoot the booster. (Don't forget Booster's filter... 84-86 Duke, in engine bay.) Brake05 Brake Booster.pdf, source: Autoshop 101 also covers booster to mc push rod
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10:57 PM
PFF
System Bot
Mar 28th, 2012
Rodney Member
Posts: 4715 From: Caledonia, WI USA Registered: Feb 2000
As I was connecting the banjo with the booster mounted on the other side, the banjo needed to be pushed into the booster by about 1/8 to 3/16" to line up with the brake pedal stud.
Check and see if moving the brake light switch outward eliminates this. If not look up at the bracket to see if something is stopping the pedal from retracting. The pedal should move out some. It may be the switch? There should be plenty of room for the brake pedal to move backwards some.
------------------ Rodney Dickman
Fiero Parts And Acc's Web Page: All new web page!:www.rodneydickman.com Rodney Dickman's Fiero accessories 7604 Treeview Drive Caledonia, WI 53108 Phone/Fax (262) 835-9575
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06:25 AM
Rodney Member
Posts: 4715 From: Caledonia, WI USA Registered: Feb 2000
I was comparing the street Panoz to the race car Panoz. I wouldn't dream of putting a Fiero anywhere in that comparison.
I'm guessing this street Panoz has brake calipers with multiple inner and outer pistons in each caliper? This is a discussion on increasing the caliper force on the stock Fiero brake system. How does this relate to the brakes on this Panoz car?? This is like apples to eagles.
------------------ Rodney Dickman
Fiero Parts And Acc's Web Page: All new web page!:www.rodneydickman.com Rodney Dickman's Fiero accessories 7604 Treeview Drive Caledonia, WI 53108 Phone/Fax (262) 835-9575
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09:07 AM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
Check and see if moving the brake light switch outward eliminates this. If not look up at the bracket to see if something is stopping the pedal from retracting. The pedal should move out some. It may be the switch? There should be plenty of room for the brake pedal to move backwards some.
I will do this this evening. I suspect it is the brake switch, but it didn't move from booster removal to booster install (so either the 88 pushrod had the same preloading, or the banjos on the two 88 boosters are a slightly different length). My concern is that if the switch allows the pedal to move closer to the driver, then the amount of pedal play should increase from 7/16" to a much larger number.
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09:26 AM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
I was able to pull the brake switches back further and that eliminated the booster banjo preload... but it increased the needed pedal travel to hit the pushrod stop. The distance went from 7/16" to 7/8" or doubled. The stock fiero setup only had 9/32, so this pedal free movement increased by .59" or nearly tripled from the stock fiero setup.
I am pretty sure this excessive pedal movement is internal to the booster and it either is a manufacturing clearance issue or just how the S10 boosters are designed. I am leaning towards this being just the way the S10 boosters are based on the feedback from others that they noticed an increase in pedal play.
Here is a video of the new movement:
[This message has been edited by fieroguru (edited 03-28-2012).]
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06:20 PM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
With the booster installed, I was able to do the same round of pressure tests with the car running to see the differences. I didn't swap in the smaller guage, so the lowest data point is missing.
code:
Caliper Pressure Comparison Stock 88 Booster vs. Rodney S10 Prototype:
Average of 10psi to 50psi input pressures: 963 1230 267 28%
As we look at the individual pressure data, it is obvious that there are some rounding issues with the +/- 25 psi accuracy on the caliper gauge. Using a 2000 psi gauge for future test would be very helpful.
If you look at the average caliper pressure excluding the outer limits of the input pressure, the new booster is providing an average gain of 28%. It is also noteworthy that the gain at low pedal pressure inputs up in the 35% range (I think there is a round off issue in the 41%, 21% 41% sequence). Once the booster is "all in" (or providing maximum gain) the S10 booster is increasing the caliper pressure by about 300psi over a wide range of pedal input pressures. If you look at the caliper pressure, the S10 booster allows a lower pedal input force to have the same caliper pressure... this helps with the feel of improve braking, same stopping force, but less pedal pressure required.
Time for a drive...
[This message has been edited by fieroguru (edited 03-28-2012).]
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06:34 PM
Alex4mula Member
Posts: 7403 From: Canton, MI US Registered: Dec 1999
It probably is my OCD and knowing that the pedal has more travel before braking happens, which makes me notice it, focus on it, and not care much for it. I prefer more instant brake action and would recommend having the booster builder look into options for reducing the larger internal clearances (maybe send them a fiero booster with the S10 one). Since this swap has been around for quite some time and I have never seen anyone make a comment about this increased pedal slop/travel, it might just be my nit-picky nature and the fact that I now know it is there that makes me focus on it. If you drive the car daily, I am sure this is something that you could get accustomed to (if you notice it at all), especially if you are used to swapping vehicles with other makes/models that have different pedal take-up characteristics.
Once you get past the pedal travel issue, the brakes do respond surprising well. Even at light pedal applications you can feel the brakes wanting to stop the car at a faster rate. It just gets better the harder you press on the brake pedal up to the point of locking the wheels up (which was easy with the stock formula wheels/tires on this car).
I think this mod has very good bang for the buck potential (I have no idea of Rodney's target price, but assume it will be reasonable). In my opinion, this upgrade would be ideally suited for those daily drivers/cruisers who are looking for more confidence in their fiero brake system without having to stand on the brake pedal or spend the $$$ for a full brake upgrade. This upgrade would also be beneficial for those with large camshafts and lower engine vacuum, the larger surface area could help restore the boost assist back to stock levels or slightly above (depends on how large of a cam, or how little vacuum you now hove vs stock).
The trade off for the low cost/simplicity of this upgrade, is that all it does is increase caliper pressure. By itself is does not do anything to increase brake fade resistance which would be more of an issue when you drive your fiero like you stole it... with higher/repeated/prolonged application of the brakes. It could be a great compliment to other brake upgrades.
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09:16 PM
Austrian Import Member
Posts: 3919 From: Monterey, CA Registered: Feb 2007
Originally posted by Rodney: I'm guessing this street Panoz has brake calipers with multiple inner and outer pistons in each caliper? This is a discussion on increasing the caliper force on the stock Fiero brake system. How does this relate to the brakes on this Panoz car?? This is like apples to eagles.
Fair enough. I just compare it what I am familiar with. I've never driven a Fiero without brake boost. (braking with the engine off doesn't count as one is fighting the booster.)
That said, going back to the Fiero after driving the Panoz at the track day felt like the Fiero clutch and brakes were broken. It felt like my leg went straight through the floor board when I first turned it on. I also learned from that, that on a street driven car, assisted brakes are a good thing.
Anyway, back to our regularly scheduled programming. I'm eager to learn more about this mod, and so far the approach is pretty scientific. Could we also do a test with maximum brake pressure? Press the brake pedal as hard as you can (or have your contraption do it), then repeat with the increased assist. Also it would be cool to record the maximum brake pressure the average user can exert on a Fiero brake system. (while sitting in the driver's seat simulating drivers) Maybe ask a few friends and write down average and median pressure.
Originally posted by Austrian Import: Could we also do a test with maximum brake pressure? Press the brake pedal as hard as you can (or have your contraption do it), then repeat with the increased assist. Also it would be cool to record the maximum brake pressure the average user can exert on a Fiero brake system. (while sitting in the driver's seat simulating drivers) Maybe ask a few friends and write down average and median pressure.
Careful, you can do major damage... Pedal design and driver's ergonomics is to remove most of leg effort so you can't generate line pressure so high that you blow a line. Even weight lifters can't do it most time. That tool maybe can blow a line...
Check Line pressure and working load pressure for soft and hard line first...
Number posted above is max from most drivers. OE Pressure above are within spec's... 1200-1500 psi is panic stopping pressure. I think, 1700 psi maybe a bit high but still w/in most spec's... Normal driving generate 400-900 psi max.
[This message has been edited by theogre (edited 03-29-2012).]
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02:38 AM
Rodney Member
Posts: 4715 From: Caledonia, WI USA Registered: Feb 2000
Is this all over complicating a relatively simple project? The S-10 brake booster idea came from Phil in Connecticut about 5 years ago. If you can successfully change the spark plugs in the V6, you can do the brake booster swap. Or have I missed a point in all those photos? A $100 rebuilt S-10 booster, some basic mechanical skill and the Fiero will actually stop.
The point is you have to cut and weld (extend) the banjo to make the S-10 booster fit in a Fiero. Personally I do not want a brake booster in my 88 Mera with a welded banjo. I would not feel comfortable and safe driving my Mera with a cut and welded banjo. Would you?
------------------ Rodney Dickman
Fiero Parts And Acc's Web Page: All new web page!:www.rodneydickman.com Rodney Dickman's Fiero accessories 7604 Treeview Drive Caledonia, WI 53108 Phone/Fax (262) 835-9575
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04:04 AM
PFF
System Bot
Rodney Member
Posts: 4715 From: Caledonia, WI USA Registered: Feb 2000
Just a quick question here. Is the booster you are testing an S10 booster or is this a custom built booster for the fiero? I ask this because the data you are compiling may be different from an S10 booster if this is in fact a custom built one.
Thanks Mike
It is a stock S-10 booster with a correct length banjo installed in it. The only custom part is the longer banjo.
------------------ Rodney Dickman
Fiero Parts And Acc's Web Page: All new web page!:www.rodneydickman.com Rodney Dickman's Fiero accessories 7604 Treeview Drive Caledonia, WI 53108 Phone/Fax (262) 835-9575
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04:05 AM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
Originally posted by Austrian Import: Could we also do a test with maximum brake pressure? Press the brake pedal as hard as you can (or have your contraption do it), then repeat with the increased assist. Also it would be cool to record the maximum brake pressure the average user can exert on a Fiero brake system. (while sitting in the driver's seat simulating drivers) Maybe ask a few friends and write down average and median pressure.
The ability to build pressure significantly higher than what it takes to lock up the brakes is pretty much irrelevant. Sure you might want to be able to go 25% to 50% higher in the event you add wide sticky tires and greatly improve traction, then it would take higher pressure to lock the wheels up, but it would also generate much, much more heat for the rotors to deal with.
From the test data you can see that the booster ramps up its brake assist, so small changes in pedal pressure at very low input loads makes much larger changes in caliper pressure. The larger S10 booster starts generating a higher level of assist almost immediately and has a similar ramp up to maximum assist. Both boosters appear to reach maximum assist at about 30psi input pressure (or 50ish lbs pedal force). The stock fiero booster increases caliper pressure about 1000 psi and adding the S10 booster increases it another 275ish psi on average. The data also shows that once the booster is "all in" from an assist standpoint, it can't go any higher and any further line pressure increase requires more pedal pressure.
The tests performed and data collected provides a very good general understanding of the booster dynamics, what the S10 booster actually does, and put some general values (+/- 25 psi on caliper pressure isn't super precise, but it does give you a overall directionality and approximate range) around the gain.
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06:51 AM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
Many kudu's and props! Nice job in quantifying something I never thought would be quantified.
Still, you said "...Sure you might want to be able to go 25% to 50% higher in the event you add wide sticky tires and greatly improve traction, then it would take higher pressure to lock the wheels up, but it would also generate much, much more heat for the rotors to deal with."
I do not understand where this extra heat would come from. The total heat to be dissappated by the rotors is based on the total kenetic energy of the car. Squeezing the rotors harder might increase the RATE that this heat is transfered to the rotors, but NOT the TOTAL heat transferred. Or do I misunderstand something here?
For what it is worth: so far the only negative I have found in my installation is the need to reeducate the driver. Yesterday, I had to make a down hill turning stop on a damp road. I tended to lock up the fronts unexpectedly by applying the same pressure to the pedal I had become accustomed to over the years. So, becareful when driving until you have become accustomed to the reduced force required to lock up the tires!
Originally posted by fieroguru: It probably is my...
Many reason why that could happen.... They weld the banjo wrong length Just didn't notice or GM Moraine doesn't have the issue PM send
quote
Originally posted by Rodney: The point is you have to cut and weld (extend) the banjo...
You can like move the banjo from OE Fiero to OE S10 but you need to take both boosters apart to do it. Taking apart etc can cause damage to the booster, and people too, w/o the proper tools. Not a good idea for nube or even most shops. For one, You take S10 apart and switch the banjo successfully but parts are old and won't seal and leak vacuum.
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12:15 PM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
Still, you said "...Sure you might want to be able to go 25% to 50% higher in the event you add wide sticky tires and greatly improve traction, then it would take higher pressure to lock the wheels up, but it would also generate much, much more heat for the rotors to deal with."
I do not understand where this extra heat would come from. The total heat to be dissappated by the rotors is based on the total kenetic energy of the car. Squeezing the rotors harder might increase the RATE that this heat is transfered to the rotors, but NOT the TOTAL heat transferred. Or do I misunderstand something here?
I should have said much more momentary heat... Conservation of energy still remains. The higher pressure will generate more heat for a shoter period of time with the total heat still being the same. And while you can change the rate of putting heat into the system, you haven't done anything to speed up the rotors ability to transfer the heat away from itself... this is where you can get in trouble with frequent braking at a higher pressure could cause brake fade to occur much sooner.
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01:01 PM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
It was suggested to check the caliper pressure at the rear so I did that on the 3.4TDC fiero that recieved the S10 booster. Then I went a did another round of tests on another stock 88 with 2.5L both front and rear. While there could be engine vacuum differences between the two engines and that could change the values some, both engines are bone stock and should be pretty close.
code:
Caliper Pressure Comparison Stock 88 Booster vs. Rodney S10 Prototype: All Tests with Engine On, but there is data from two 88 Fieros - 3.4TDC and 2.5L
First: Notice is there is some variation in the stock front to stock front between two different fieros. There are a couple of outliers but with +/- 25 psi accuracy per data point there will be some. If you take the average caliper pressure from 10 to 50 psi input pressures, the 2.5L has about 40psi more caliper pressure which isn't a huge difference and could just be an idle vacuum difference.
Second: When looking at 3.4TDC Front/Rear with the S10 booster - the rear only receives a fraction of the caliper pressure (due to the proportioning valve). The rear is about 67% less at 10 psi input pressure and drops to the low 50-53% range at higher input pressures. For comparison the stock front/rear brake bias on the 2.5L fiero starts at 75% @ 10psi and ends at 55 @ 60 psi.
Third: When comparing the stock 2.5L rear caliper pressure to the 3.4TDC with S10 booster, the S10 booster is providing between 0 to 17% gain at the rear (these values might be shifted slightly due the difference engine vacuum), but the directionality is different than the front. The In the front the S10 booster improvement starts at 41% @ 10psi and drops to 15% @ 60psi. The rear improvement starts at 0% @ 10psi and increases to 16% @ 60 psi. It looks like at low pedal inputs the fronts are seeing a much higher % of the overall booster gain, and as input pressure is increased, more of the gain is shared with the rear.
So there you have it.
The S10 booster does increase caliper pressure but the change is not equal or in the same direction front/rear through the normal range of pedal input forces. The S10 booster changes the front/rear brake bias with the front seeing a higher % of the increase at low pedal inputs and at extreme pedal inputs the gain is almost split 50/50 F/R. The S10 booster does not improve fade resistance.
[This message has been edited by fieroguru (edited 03-29-2012).]
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08:57 PM
fieroguru Member
Posts: 12305 From: Champaign, IL Registered: Aug 2003
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