As some of the folks from the chat room and at Daytona already know, I stumbled upon a cheap and effective brake upgrade. There is also a writup of this in the current Fiero Pride newsletter. Although I've only done this on a 88 I see no reason why it wouldn't work for any year Fiero. While I had the hood open on my Chevy S10 pickup (dead battery) I noticed that the power brake booster had a bit larger diameter than that of the Fiero. After taking a few rough measurements I determined that the S10 booster would fit in the Fiero. The installation turned out to be rather easy. # 1 - Unbolt the master cyl from the Fiero booster and just move it out of the way( no need to disconnect any brake lines) and disconnect the pushrod from the pedal # 2 -Remove the Fiero booster and then file/cut/ grind the 4 rivets that attach the bracket to the Fiero booster and bolt the bracket to the S10 booster
# 3- You now have to extend the pushrod from the booster to the pedal. I made a threaded coupling but it's really not needed. Cut the end off othe S10 booster ( it's the wrong size hole) you can get a piece of steel rod and drill a hole in one end to fit over the rod and then cut the Fiero rod insert the proper length onto another drilled hole in your coupling. Seeing that this extended rod will only be in compression you could get away with JB welding the ends into the coupling but electric welding may be better.
# 4- A slight bit of BFH work is needed to give the needed clearence for the new setup
# 5- Reinstall the new setup and you're finished
I used a booster from a 96 S10 I will be doing this conversion at a NEFA Tech Session at my house o n Apr. 23 . Let me know if you want to attend Pedal modulation is excellant and I can lock up all 4 at any speed ( if I realy really wanted too)
[This message has been edited by Phil (edited 04-04-2006).]
Just as a side note , I did have the 12" Vette rotor setup on my car before but I didn't like having to carry a 16" spare in the front ( sunroof glass wouldn't fit in the front anymore) and I think that I now have better braking with the stock rotors and the bigger booster than with the Vette setup. I don't know if I would do both conversions at the same time - brakes might get a little too touchy.
But I'd really like to hear from some people who know how a brake booster works - with the math. I think we all know that sometimes bigger doesn't mean better - as in the case of big-bore master brake cylinders. Does a bigger brake booster automatically mean more brake assist? Can the stock engine supply the vacuum necessary?
As the area increases the amount of force created will be bigger, even if the pressure stays the same, or in this case vacuum. So going to a physically bigger booster should increase the braking force. The big bore master cylinders work the opposite of this because of the way the force is applied. You are applying the same force over a large area and generating less pressure, so it would take more force to generate the same pressure of the normal sized master cylinder.
So going to a physically bigger booster should increase the braking force.
But only if the vacuum stays the same. And I know from personal experience with one of my secret projects, that increasing volume of a vacuum canister has a tendency to reduce vacuum given the same source of the vacuum. In other words, my compressor running a venturi valve to vacuum a tank produces a lesser rate of vacuum with a bigger tank. Imagine trying to suck one breath out of a 20oz pop bottle... enough vacuum to crush the bottle. Now imagine trying to suck one breath out of a tanker truck. Your vacuum won't even register....
[This message has been edited by fierogt88 (edited 04-04-2006).]
Fiero88GT, If your vacuum drops, you have a leak. Regaurdless of the size tank you're using. The only difference that the size of the tank will make is in recovery time. Keep in mind that the S-10 booster is only slightly larger, the recovery time to make up for this size is negligable. Your engine produces a near constant vacuum. (sucking on a water bottle does not). Replace, "you sucking on the bottle", with a vacuum cleaner. Both bottles will colapse. Kevin
------------------ 85 Fiero-based ASPP GT-40 MarkII. 3800 S/C, Auto, Held suspension all around with 2" drop spindles and sport fr. end. RCC bump-steer correction. Mr. Mike's interior.
yes, the vacuum boost is a sealed system, with a continous vacuum source (the engine). the larger surface of the diaphram will make for more brake assist. the older concern with a larger bore master cyl creating more brake effort is now covered.
This could be the answer I'm looking for. You see, I have the Grand Am brakes front and rear. But I'm still using the stock master cylinder, because I'm afraid the Blazer m/c will increase pedal effort too much. The increased power boost might compensate for that.
Phil, can you tell me the total length of your modified brake banjo?
First, I want to reiterate that I find this mod particularly interesting, as yes, it does have potential to be a great upgrade.
But again, we need details. The is your brakes, after all.
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If your vacuum drops, you have a leak. Regaurdless of the size tank you're using.
I wasn't talking about a vacuum drop. I was talking about more volume causes less vacuum given the same source. That is a fact. Deal with it. To get around this, the source of the vacuum (the engine) has got to work harder. And as far as the vacuum cleaner comparison, I'm sorry but there is still a time difference between when the vacuum cleaner registers vacuum in a pop bottle and when a vacuum cleaner registers vacuum in a tanker truck.
We already have the answer to my first question: does a bigger brake booster automatically mean more brake assist? The answer is No, not absolutely. In the case of the s10, it may provide more brake assist - but the bigger size alone does not automatically guarantee it.
So we go back to my second question: can the stock engine supply the vacuum necessary? Well, if this came off a 2.8 s10 I wouldn't have any problems with it, but I'm guessing this came off a 4.3 s10. The 4.3 is significantly larger - 1.5 liters larger. Over 50% bigger. Now, I'm no expert on how engines produce vacuum, but it sure raises a question, in my mind anyway, about a whether a brake booster designed to be supplied by a much larger engine will be satisfied by the much smaller 2.8.
And now I've got a new question: How is the vacuum regulated in the brake booster? Since the engine is almost constantly producing vacuum, there has to be a limiter for how much vacuum is produced. My assumption at this point is that there is some kind of pressure valve in the booster assembly. Is the valve the same size? Does it provide the same air flow? Is it tuned to peak the booster at the same amount of vacuum? Or more vacuum? Or less? Is it even inside the brake booster?
And here is another one: Is the booster appropriately sized for the mechanical leverage of the fiero setup? Right off the bat I know absolutetly that there is a greater distance between the booster and pedal in an s10 than there is in a fiero. This means there is a lot more opportunity for the s10 to get brake assist from mechanical leverage of the pedal linkage. Quite simply, if the s10 uses twice the mechanical leverage, the booster may be tuned for HALF of the total brake assist power. That would not be a good thing....
Again, I'm not bashing the mod. Obviously Phil is reporting good results so I'm sure that the answers to these questions, once answered, will prove mathematically that it's an improvement. But if you think I'm gonna trust my brakes to "seat of the pants" you've got another think coming. I'm just saying that there are a lot of VALID questions that have to be answered before we all run out and slap them on.
And one last point of thought: I've seen several motor swaps in other platforms where a smaller brake booster was chosen so a bigger engine could fit in the bay. (think big block swaps and big v8 swaps into smaller vehicles like monzas, chevettes, s10's, etc.) I've never looked into the math before, but obviously size is not the only determining factor.
yes, the vacuum boost is a sealed system, with a continous vacuum source (the engine). the larger surface of the diaphram will make for more brake assist. the older concern with a larger bore master cyl creating more brake effort is now covered.
And now that I think more about it, this flies in the face of the formula posted above.
Increasing area decreases force, according to the formula. The only way around that is to increase vacuum...
AAMOF, it sounds exactly like the big bore issue, only now we're dealing with a gas vacuum instead of a liquid pressure...
Calm down, people. The S10 booster is only a fraction larger than the Fiero one. It may take a fraction of a second longer for the engine to depressurize it. Big deal.
But sorry, all my points are valid. The brake system in any given vehicle has a lot of components in it that all work together to correctly give the right amount of brake force according to known mathematical principles. The questions are there, and need to be answered before anybody starts proclaiming it as a safe upgrade for the masses. I'm sure that once we know the answers, it will all fall into place, but my questions are unargueably valid. So if anybody needs to calm down, I say it's the "defenders of the holy" that are here trying to use the "well duh bigger is better" method of analysis.
EDIT: Oh, and once we start seeing actual numbers, it's quite possible that this will actually work better with a bigger s10 master cylinder. Again, this has great potential but lets see some real math here...
[This message has been edited by fierogt88 (edited 04-04-2006).]
And now that I think more about it, this flies in the face of the formula posted above.
Increasing area decreases force, according to the formula. The only way around that is to increase vacuum...
Actually, since it is assist, it is not the same at the big bore MC problem...I digress,
If F=P/A that means that if you increase A you need less P to do the same amount of F right? The booster is adding to the P that you apply. So doesn't that mean it takes less pressure (from your foot + booster) to make the same amount of force (on the brakes)? So in theory with more P AND more A you get much more F.
The reason this doesn't work with the MC is the P is working against you....instead of assisting you. I hope this makes some sence.
Best regards,
~Shane
BTW...this could be wholly wrong, I'll have to re-read it a few times before I convince myself...haha
edit: or maybe it is. Regardless, it's a matter of ratio to the pressure and the value of F can vary widely depending on the mechanical leverage available from the pedal design. I'm looking now for verification of the formula either way...
[This message has been edited by fierogt88 (edited 04-04-2006).]
Think for a minute. What units do we use to measure pressure? In the Imperial system it's Pounds per Square Inch, i.e. force/area. So obviously, P=F/A. Multiply both sides by A and you get F=PA.
But back on topic... the big question is the size difference between the S10 booster's bladder and that of the Fiero booster. The force increase will be directly proportional to the bladder area increase.
[This message has been edited by Blacktree (edited 04-04-2006).]
You are correct on the formula. (so you can ignore my previous post where I relied on the false formula)
However, you are still neglecting the importance of the correct level of vacuum. The check valve and the amount of vacuum the engine can pull are the other half of the equation.
the same vacuum in a larger area = more force - its basicly like useing a larger wrench now, on the other side, many aftermarket cams do lower the manifold vacuum, and canisters are used to store vacuum peaks, and even vacuum pumps are used for extreme applications. while I understand this is brakes, and its important to be careful, but its not like this is an overwhelming brake assist that will lock up the brakes with the slightest tap of the pedal, its just a slightly larger assist to help with slightly larger bore MC, which needs slightly more assist.
Yes Blacktree, but that just means that instead os ponds per squar inch in the line I was thinking pounds force at the calipers...either way. Though about the vaccum and volume of the booster...I thought the bosster was sealed, ie, no check valve? I thought once it got to the correct vaccum it would hold there, though saying this now in my head makes no sence as if that happened the vacuum would continue to rise, untille the sys gets air from somewhere (leak) so in that case I can definately see that if the check valves were indeed differant (open sooner for the *bigger* booster) this would be a problem. All in all Phil said the results are great so the detail don't really matter to me, except what year S-10 the booster is out of?
I'm not neglecting anything. As I already stated, the bigger booster will take longer to pressurize.
Do you have an air compressor? If you use it to fill a 10 gallon tank, does the pressure somehow end up being lesser than a 2 gallon tank? If the compressor is capable of 100PSI, it will fill both tanks to 100PSI. The difference is time.
the same vacuum in a larger area = more force - its basicly like useing a larger wrench
And, again, until you can show me that a 2.8 and 4.3 pull the same vacuum and that the check valve from a fiero booster and the check valve from an s10 maintain the same vacuum then no global statement that uses the term "same vacuum" is even remotely valid.
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now, on the other side, many aftermarket cams do lower the manifold vacuum, and canisters are used to store vacuum peaks, and even vacuum pumps are used for extreme applications.
So changing cams can change how much vacuum is pulled but changing engines doesn't?
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while I understand this is brakes, and its important to be careful, but its not like this is an overwhelming brake assist that will lock up the brakes with the slightest tap of the pedal, its just a slightly larger assist to help with slightly larger bore MC, which needs slightly more assist.
Yes, I think once we verify how much vacuum is being pulled inside the booster with a 2.8 engine (and honestly I really really really do think it will come up fine - but nobody has offered to hook up a vacuum guage yet...) and once we have some comparable measurements for the pedal assemblies, this may actually allow the use of the bigger cylinder with more force applied at the calipers and less pedal effort at the foot. But again, if the proper vacuum can't be generated/maintained then it's a little early to be telling everybody it's a safe upgrade.
[This message has been edited by fierogt88 (edited 04-04-2006).]
I'm not neglecting anything. As I already stated, the bigger booster will take longer to pressurize.
Do you have an air compressor? If you use it to fill a 10 gallon tank, does the pressure somehow end up being lesser than a 2 gallon tank? If the compressor is capable of 100PSI, it will fill both tanks to 100PSI. The difference is time.
You are neglecting that there is a limiter of the vacuum somewhere in the system, and it could be drastically different between a 2.8 and a 4.3. When you look at a compressor that is "capable of 100 PSI", you are looking at the rating of the TANK not the compressor. So yes time is the factor, but if the check valve in the s10 booster maintains half the vacuum that the fiero check valve does, then you have half the assist. And this would be perfectly acceptable if, say, the s10 uses twice the mechanical leverage at the pedal...
Edit: I can't believe I wasted my 1000th post on this... lol
[This message has been edited by fierogt88 (edited 04-04-2006).]
And this is why I don't come here much anymore. Anytime you actually try to talk facts, science, and logic with the "dur, uh yeah, well think about it" types, they get all pissy...
Last I checked it was friendly discussion about the real -->TECHNICAL <-- situation in the tech section with tech type people but somebody had to get sand in their vagina...
ALL engines run at approx the same vacuum. vacuum is determined by cam profile, not engine displacement. a 1.6L has basicly the same vacuum as a 6.9L now, the 1.6 wont have as much volume as the 6.9, but the vacuum will be the same. and both will give brake boost almost instantly so a 1.6L chevette can use a 6.9L suburban booster is they wanted effortless brakes
just an observation. Phil tried this and it worked. if another tries it and it works, it would be confrimation.
speculating on theory without all the proper data is usless. The 2 issues i see are: recovery time for the vacuum when the volume is increased, and is the vacuum supplied sufficient. if it works the answer is a qualified yes. would need actual before and after data to evaluate this properly, then we would need a qualified engineer in gas systems to review it.
I don;t do gas systems. I do EE stuff. so let's see where our engineers in gas syetems would say.
ALL engines run at approx the same vacuum. vacuum is determined by cam profile, not engine displacement. a 1.6L has basicly the same vacuum as a 6.9L now, the 1.6 wont have as much volume as the 6.9, but the vacuum will be the same. and both will give brake boost almost instantly so a 1.6L chevette can use a 6.9L suburban booster is they wanted effortless brakes
Well that's a pretty big statement, that ALL engines run at the same vacuum... I know my 3800 supercharged does not... And I know lloyde commonly sets up his swaps for full time boost... I don't know how he pulls that off...
But maybe all normally aspirated do? That's a possibility... Do you have any links or sources for that claim?
And if a chevette could use a suburbans booster... why wouldn't it? Heck, why should we stop at an s10 booster? Lets just run out and get one off of a Ford Excursion! Oh yeah, that little thing that I brought up about tuning it (the diaphram size, the check valve, and maintained vacuum) to the mechanical leverage in the original vehicle...
And on the volume of the booster... So we're going to a XX% larger booster... With a 50% smaller engine to fill it with... Well, that's gonna be significantly over a 50% increase in vacuum charging rate... Does that matter? it might. We'd have to know exactly how much bigger the diaphragm is, how much more volume, the rate of vacuum for both engines...
Seriously though, to satisfy me all I'd need was a vacuum gauage hooked up to the constant vacuum side of the booster (after the check valve) and make sure that at least as much vacuum was maintained during driving conditions. That's not so hard...
So, when Phil comes in, 2 questions... 1. What is the exact diameters of the 2 booster pumps? 2. Any chance you could hook up a vacuum guage to the constant vacuum side of the booster? I'd be willing to do it for the stock one for comparison purposes...
Well that's a pretty big statement, that ALL engines run at the same vacuum... I know my 3800 supercharged does not... And I know lloyde commonly sets up his swaps for full time boost... I don't know how he pulls that off...
But maybe all normally aspirated do? That's a possibility... Do you have any links or sources for that claim?
And if a chevette could use a suburbans booster... why wouldn't it?
yes, boost does change things no, no links for that claim. but, I think 12-14 PSI is standard vacuum for average street cars and, some brake effort is a good thing, to prevent overbraking. gotta give the person behind the wheel some pedal pressure, to have a "feel" for the brakes
With the throttle plate closed my engine pulls about 18"Hg- Now think about this- Once the vac side of the booster is evacuated the black check valve keeps it evacuated in fact you could even pull off the hose and you will still have power assist for about 2 or 3 pedal applications. Usually when you step on the brakes you take your foot off the gas and then you get max vac. I have put about 4000 miles on this setup without any noticable difference except that my brakes work much much better. The first booster I had did have a vac leak in it and whenever I stepped on the brakes I did get a slight RPM increase but a reman booster fixed that right up. As for the length of the push rod just measure the distance of the stock Fiero from the back of the bracket to the center of the attachment hole. I think you have to add about 2 1/8 " but meqasure to be sure. If I step on my brakes 3-5 times with the engine off (gets rid of any vac reserve in the booster) and then start the car I have full power assist again in under 2 sec. Ther is someone on the forum ( I forget who) who works in brake booster design and he had no objections to this mod . I used to be an engineer and I'll say that actual data is light years ahead of imperical data. According to the "experts" a bumblebee shouldn't be able to fly either.
Well that's a pretty big statement, that ALL engines run at the same vacuum... I know my 3800 supercharged does not... And I know lloyde commonly sets up his swaps for full time boost... I don't know how he pulls that off...
But maybe all normally aspirated do? That's a possibility... Do you have any links or sources for that claim?
On a S/C 3800 ( that's what I have) the vac for your brakes is taken from infront on the S/C so boost pressure has no effect BTW to set for boost all the time just disable the boost bypass valve.
But I have a revelant question.........Does replacing the Master Cylinder with a Bigger one have an affect on the pedal? I replaced my M/C with a Bigbore and the brakes haven't been the same since! Now,...if I replaced the Booster with the aforementioned S-10 option,...would that help my "soft Pedal" problem?
