quote Originally posted by sspeedstreet: Put some brake fluid in that reservoir!

Did that yesterday.

quote Originally posted by sspeedstreet: Put some brake fluid in that reservoir!

Looks full to me... No?

It looks like this mod would have been quite useful to me when I had my Fiero.

I always had weak launches at the dragstrip because I couldn't hold any boost at the line due to the car overpowering the brakes. The increased clamping force would have probably helped out a fair amount in that regard.

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'04 Mazda RX8 Build Thread
'88 GT- 3800 Turbo 11.367@121.03mph (Sold and gone now)
GM Tuners

I didn't take any good video's (first attempt failed), but I did compare the "slop" in the pedal between two Fieros, one with an S-10 booster, one with the Fiero booster, and both being otherwise stock pre-88 systems. I did not notice any major difference between the two in slop. If anyone wants a more precise comparison in slop I can do so.

[This message has been edited by mattwa (edited 04-01-2012).]

Thanks to Rodney for another Fiero product. And thanks the Guru for the examination of the part.
I have use a set of Rodneys test run ball joint end links, I still have them in my LS4 GT and they have been working great.

I put a S10 booster in my 88 some time back and can say that it is a good upgrade. I can also say that I have done the S10 swap in a stock 88 and my C4 12" rotor 88.
I have never been able to get a "good" feel from my C4 rotors and S10 booster. The travle is long and soft. BUT for some reason the stock 88 with the S10 felt really good, it had a shorter petal and a much harder feel than my 88 with C4 rotors. I am not exactly sure why, but I just cant seem to get the "feel" that I want out of the LS4 88.
The booster let me lock up the wheels at will and with less effort, and that made the car "feel" safer to me. I did not have to stand on the brake to get the wheels to lock up.
But this is just one of those upgrades that I would do to every 88 I will ever own. If I could save the time and just buy a booster set up for the swap, I would do it in a heart beat. I had to buy two new boosters the last time I did this swap because I broke the black plastic just inside the booster. I dont remember how I did it but I screwed it up some how.

quote Originally posted by Rickady88GT: Thanks to Rodney for another Fiero product. And thanks the Guru for the examination of the part. I have use a set of Rodney"s test run ball joint end links, I still have them in my LS4 GT and they have been working great. I put a S10 booster in my 88 some time back and can say that it is a good upgrade. I can also say that I have done the S10 swap in a stock 88 and my C4 12" rotor 88. I have never been able to get a "good" feel from my C4 rotors and S10 booster. The travel is long and soft. BUT for some reason the stock 88 with the S10 felt really good, it had a shorter pedal and a much harder feel than my 88 with C4 rotors. I am not exactly sure why, but I just cant seem to get the "feel" that I want out of the LS4 88. The booster let me lock up the wheels at will and with less effort, and that made the car "feel" safer to me. I did not have to stand on the brake to get the wheels to lock up. But this is just one of those upgrades that I would do to every 88 I will ever own. If I could save the time and just buy a booster set up for the swap, I would do it in a heart beat. I had to buy two new boosters the last time I did this swap because I broke the black plastic just inside the booster. I don't remember how I did it but I screwed it up some how.

You're scaring me, Rick. I'm in the midst of doing my C4 12" rotor 88 install and I'm contemplating the S-10 booster. What possible connection could there be between the booster and the rotors? Maybe if the master cylinder or the calipers were changed, but all rotors are an immovable object as far as the pedal knows.

[This message has been edited by sspeedstreet (edited 04-02-2012).]

quote Originally posted by sspeedstreet: You're scaring me, Rick. I'm in the midst of doing my C4 12" rotor 88 install and I'm contemplating the S-10 booster. What possible connection could there be between the booster and the rotors? Maybe if the master cylinder or the calipers were changed, but all rotors are an immovable object as far as the pedal knows.

I dont blame the rotors, It could be that I am just overlooking some small part that is causing the problem. My opinion is that you should do one upgrade at a time. Do the rotors first and see how you like it. Drive it for a while and make sure it works for you in several different type of braking conditions, and just make sure the system is functional and healthy. IF for some reason you think it needs the booster, then do the booster.

quote Originally posted by Rodney: 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?

I wholeheartedly agree with Rodney. While it may or may not be safe, I do not trust my welding skills with such a safety item. I prefer something that Rodney thought through all the way.

quote Originally posted by Rickady88GT: I don't blame the rotors, It could be that I am just overlooking some small part that is causing the problem. My opinion is that you should do one upgrade at a time. Do the rotors first and see how you like it. Drive it for a while and make sure it works for you in several different type of braking conditions, and just make sure the system is functional and healthy. IF for some reason you think it needs the booster, then do the booster.

A question about your boosters, then. Were they all from the same source?

Your numbers says 88 prop valve is working at full time. EI a "True" prop valve.
(Acts like Figure B on this page.)

I re-edit the columns to show the prop valve to front/rear brakes.

code:

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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"
					
	2.5L	2.5L		3.4TDC	3.4TDC
Input	Front	Rear		Front	Rear
 Air	Stock	Stock		S10   	S10
(psi)	(psi)	(psi) 		(psi)	(psi)
10	400	300		450	300
15	600	400		700	400
20	800	500		950	550
25	925	600		1275	675
30	1200	675		1475	775
35	1225	700		1500	775
40	1250	700		1550	775
45	1300	725		1575	850
50	1325	725		1600	850
55	1375	775		1675	900
60	1400	775		1700	900

---

I think 84-87 uses a prop valve design that works like air/fuel regulators to limit max line pressure. (Figure C on link above)
Older Fiero have some natural bias, 88 doesn't.
Thanks for posting that data.

[This message has been edited by theogre (edited 04-03-2012).]

quote Originally posted by sspeedstreet: A question about your boosters, then. Were they all from the same source?

I think so, but dont recall for sure? They were all new, I did not adapt any used boosters.

quote Originally posted by Rickady88GT: I think so, but don't recall for sure? They were all new, I did not adapt any used boosters.

Thanks, Rick.

Great write-up and testing Guru. Very interesting data.

My question is, on your test drives, did you find the Fiero to be more controllable or less during hard braking using the S10 brake booster versus the stock version? Was modulation of the brake pedal during high speed cornering that great of a difference from the stock version and were you able to flat spot any tires?

In that I'm not a professional driver not an engineer, I'll ask. Does it not make sense that during hard braking that more caliper pressure it transferred to the rear calipers? I'm thinking that makes a lot of sense.

------------------
Ron
The key thing is to wake up breathing! All the rest can be fixed. (Except Stupid - You can't fix that)
Always remember these words of wisdom.

"The Lord must truly love fools, for he made them in abundance."

quote Originally posted by blackrams: Great write-up and testing Guru. Very interesting data. My question is, on your test drives, did you find the Fiero to be more controllable or less during hard braking using the S10 brake booster versus the stock version? Was modulation of the brake pedal during high speed cornering that great of a difference from the stock version and were you able to flat spot any tires? In that I'm not a professional driver not an engineer, I'll ask. Does it not make sense that during hard braking that more caliper pressure it transferred to the rear calipers? I'm thinking that makes a lot of sense.

Actually, that is not a favorable scenario. When braking, weight is transferred to the front of the vehicle. Having more of the braking force applied to the rear brakes does not do much good, since the rear brakes do not work nearly as well to stop the car. You want most of your braking power biased to the front brakes because they are under more pressure when braking. I'm sure guru will be able to explain this much better than I can.

quote Originally posted by ThatFieroKid: Actually, that is not a favorable scenario. When braking, weight is transferred to the front of the vehicle. Having more of the braking force applied to the rear brakes does not do much good, since the rear brakes do not work nearly as well to stop the car. You want most of your braking power biased to the front brakes because they are under more pressure when braking. I'm sure guru will be able to explain this much better than I can.

Yes, generally speaking for a car with a static weight bias on the front wheels, but on a mid engined car the rear wheels have more weight on them during braking, therefore the rear brakes can do more work.

The Fiero, with its 47/53 static balance, keeps a lot more weight on the rear than a FWD car with a 57/43 (or 60/40) static balance during braking.

The concept is simple, braking force should be proportional to the current weight distribution. In a low to no traction situation, best braking is fairly close to matching natural weight distribution with a slight front bias to keep spin outs from occurring. Since the Fiero is slightly rear heavy, 50/50 happens to be just about right. This explains why Fiero's brakes are very close to identical on all fours. (50/50 F/R in 88, 51/49 in 84-87)

However, when you are panic braking in an ideal traction circumstance, the weight transfer would dictate a need more and more front brake bias. This is exactly what the combination valve is supposed to take care of. The combination valve, according to the math should not do any proportioning up to about 300-350 PSI ish, maybe lower? But for each 1 PSI the fronts increase, the rears increase 0.75 above the proportioning start point. I still have yet to butcher a combination valve and instrument it.

At least that's how its supposed to work in theory Guru's numbers say otherwise

[This message has been edited by Fierobsessed (edited 04-03-2012).]

quote Originally posted by Fierobsessed: Since the Fiero is slightly rear heavy, 50/50 happens to be just about right. This explains why Fiero's brakes are very close to identical on all fours. (50/50 F/R in 88, 51/49 in 84-87) At least that's how its supposed to work in theory Guru's numbers say otherwise

50/50 never happen in an 88. 88 uses a "true" prop valve and run at all line pressures. 88 prop has small but major design changes.
I still think 84-87 uses the kind of valve you are thinking. IE F/R same pressure until rears hits pressure limit.

You need different math to see 88 brake bias. (no, i don't have it.)

quote Originally posted by ThatFieroKid: Actually, that is not a favorable scenario. When braking, weight is transferred to the front of the vehicle. Having more of the braking force applied to the rear brakes does not do much good, since the rear brakes do not work nearly as well to stop the car. You want most of your braking power biased to the front brakes because they are under more pressure when braking. I'm sure guru will be able to explain this much better than I can.

I'd agree in straight line braking but, not necessarily true while cornering and braking. But, I'm not looking to debate that here.

------------------
Ron
The key thing is to wake up breathing! All the rest can be fixed. (Except Stupid - You can't fix that)
Always remember these words of wisdom.

"The Lord must truly love fools, for he made them in abundance."

So what's the latest on these? Are they available yet? I searched but didn't see a more recent thread on this.

quote Originally posted by Rodney: Yes. I went thru a lot to get these made. Time, money and effort. This was no small project to get a brake booster custom made to my specs.

so whas different in this booster than the s-10 one..

quote Originally posted by E.Furgal: so whas different in this booster than the s-10 one..

The banjo was lengthened to correctly fit the Fiero. The S10 booster banjo is shorter.

quote Originally posted by Silicoan86: So what's the latest on these? Are they available yet? I searched but didn't see a more recent thread on this.

Anybody know?

Now I think I understand why the car I bought that has the S-10 booster, has what I call a soft pedal. It travels farther than what I was accustom to in my old 88.

And I need to bleed the system.

[This message has been edited by solotwo (edited 02-28-2013).]

Sometimes it's easier to visualize

Just curious to know if the S10 booster can be pre-loaded by using an even longer shaft to take up the extra slack...

Bob

quote Originally posted by RCR: Just curious to know if the S10 booster can be pre-loaded by using an even longer shaft to take up the extra slack... Bob

Possibly, but you have to be careful not to make it too long:
https://www.fiero.nl/forum/Forum2/HTML/126926.html

I'll be watching this one.

quote Originally posted by fieroguru: Possibly, but you have to be careful not to make it too long: https://www.fiero.nl/forum/Forum2/HTML/126926.html

Would there be an issue making it just long enough to touch off on the master cylinder plunger? Or is the slack required?

Bob

quote Originally posted by RCR: Would there be an issue making it just long enough to touch off on the master cylinder plunger? Or is the slack required? Bob

I do not know all the interworkings of the brake booster, but assume the clutch pedal bango pushes on some type of control valve within the booster. Any slack that can be taken up w/o activating the control valve would help reduce pedal slop without having adverse impact. The body of the control valve then pushes on the brake master pushrod - but all this happens internal to the booster and any modifications to reduce and excessive clearance would require full balancer disassembly. Lastly, the pushrod activates the brake master cylinder, so if any slack can be taken out at this point without activating the brake msater, then that could help as well.

The real issue is you are talking about making adjustments for manufacturing tolerances that will vary from booster to booster and suppier to supplier, so there will likely never be a precise solution that could be applied to all S10 boosters (like one that says to make the banjo .065" longer and the pushrod .032" longer). With enough time/effort you could do something to possibly improve your setup, but doing the exact same on another one could cause the brakes to self activate under certain conditions.

Thanx for the explanation. Definitely more involved than I thought.

The other question I have would involve geometry.

How different is the S10 pedal geometry from the Fiero? Does that play into it?

Bob.

quote Originally posted by RCR: Thanx for the explanation. Definitely more involved than I thought. The other question I have would involve geometry. How different is the S10 pedal geometry from the Fiero? Does that play into it? Bob.

If the mechanical advantage of the pedal was greater, then you would have more pedal travel for a given movement of the banjo. If you wanted less pedal movement before brake engagement, you would have to raise the pedal pad or lower the banjo attachment. However, this will also lessen the output force from the master for a given pedal force input, which is the exact opposite of what the S10 booster upgrade is trying to accomplish.

I think Rodney is no longer selling these as pointed out by a prior post. But although I have moderate mechanical skills, I found the S-10 booster conversion to be relatively easy.
I used a rebuilt 1997 S-10 booster bought for about $ 100. Also a 4 pound sledge hammer.
Other than beating the crap out of the frame just to the lower right of the booster placement when facing the firewall, extending the input brake shaft was the most challenging.
But for $100 the improvement is significant.
Phil Randolph, a Connecticut Fiero owner was the first to do the conversion about 7-8 years ago and has a detailed post on the forum someplace.

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quote Originally posted by fieroguru: If the mechanical advantage of the pedal was greater, then you would have more pedal travel for a given movement of the banjo. If you wanted less pedal movement before brake engagement, you would have to raise the pedal pad or lower the banjo attachment. However, this will also lessen the output force from the master for a given pedal force input, which is the exact opposite of what the S10 booster upgrade is trying to accomplish.

Thanks again Fieroguru, I do understand that. I guess what I meant to ask is whether anyone understands (knows) the difference in the swing-arm (pivot to banjo) length between the S10 and Fiero.

Bob

quote Originally posted by solotwo: So Rodney are you selling these now?

No. See https://www.fiero.nl/forum/F...L/072173-8.html#p282

quote Originally posted by RCR: Just curious to know if the S10 booster can be pre-loaded by using an even longer shaft to take up the extra slack...

No... when you have "slack" (or Low Pedal cause by booster) then input shaft, output shaft, or both, is set wrong. Small amount of "slack" is build-in to booster control valve and that is needed. Never try to eliminate (preload) control valve slack.

quote Originally posted by aaron88: Sometimes it's easier to visualize

Thanks.

[This message has been edited by theogre (edited 02-28-2013).]

quote Originally posted by theogre: Originally posted by solotwo:So Rodney are you selling these now? No. See https://www.fiero.nl/forum/F...L/072173-8.html#p282

That is an outdated post actually. He restarted the development of these after that post, and sent one to Fieroguru to inspect and review - thus the reason for this thread. (Notice the date this thread started is a month after the date of that post.)

Unfortunately, there doesn't seem to have been any updates on this for some time now though.

[This message has been edited by Silicoan86 (edited 02-28-2013).]

quote Originally posted by Silicoan86: That is an outdated post actually. He restarted the development of these after that post, and sent one to Fieroguru to inspect and review - thus the reason for this thread. (Notice the date this thread started is a month after the date of that post.)

He's post in this thread says "I think about it..."
https://www.fiero.nl/forum/F.../HTML/121747.html#p3

I thought fieroguru got first version to test in $100 __ thread and took some time to install, get tools to test, time to test, time to writeup...
RD had a few test boosters in other posts in this thread but Booster still not on his site.

You can find aftermarket units w/ customizable links if you need it...
www.fiero.nl/forum/Forum2/HTML/072173-8.html#p284

quote Originally posted by theogre: I thought fieroguru got first version to test in $100 __ thread and took some time to install, get tools to test, time to test, time to writeup... RD had a few test boosters in other posts in this thread but Booster still not on his site.

Just to clarify, I was NOT one of the first 3 people identified to install/test the booster who didn't deliver, I was in the second batch and started my evaluation within hours of it arriving. I sent an email to Rodney on 3/21/2012 at 4:41 PM that the booster arrived and started this thread on 3/23/2012 at 9:22 AM with my first round of preliminary measurements...

Some time after my evaluation Rodney sent me an email saying he was not going to be offering a version of the S10 booster, but he might look for a smaller booster that fit better and didn't produce as much of an increase.

quote Originally posted by fieroguru: Just to clarify, I was NOT one of the first 3 people identified to install/test the booster who didn't deliver, I was in the second batch and started my evaluation within hours of it arriving. I sent an email to Rodney on 3/21/2012 at 4:41 PM that the booster arrived and started this thread on 3/23/2012 at 9:22 AM with my first round of preliminary measurements... Some time after my evaluation Rodney sent me an email saying he was not going to be offering a version of the S10 booster, but he might look for a smaller booster that fit better and didn't produce as much of an increase.

Ok, Thanks. Still a good writeup.