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iBooster Electric Brake Booster

Anybody determine which port is front and which is rear on these dinky MC's? I've been browsing pics and diagrams with no real luck. Might have been posted here and I missed it.

20240915_153535.jpg
 
JNHEscher said:
Anybody determine which port is front and which is rear on these dinky MC's? I've been browsing pics and diagrams with no real luck. Might have been posted here and I missed it.

20240915_153535.jpg
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rockota said:
IIRC, "standard" is that the rear most port on the MC (closest to the booster) is for the front brakes... Likely depends on the master, but it's been fairly consistent in my experience.
Click to expand...
 
If all else fails hook a bench bleeding kit to it and "flow" test it.
If it does have bias built in likely doesn't matter right?
 
Anyone switch to a bigger MC than the Accord MC and get a noticeably better pedal feel? On my 05+ D60 and ‘14 Sterling 10.5 the pedal feel is completely linear once the ignition is turned on. This thing is incredibly powerful. Curious if a bigger bore MC is worth the money and effort. The Accord MC works fine aside from pedal resistance.
 
JNHEscher said:
Anybody determine which port is front and which is rear on these dinky MC's? I've been browsing pics and diagrams with no real luck. Might have been posted here and I missed it.

20240915_153535.jpg
Click to expand...


I asked earlier and no real answers, so I went front to front. Seems ok.
 
Try the back, gives us more data points.

I may flip them this winter just to try. Also may try other calipers to see how they feel.
 
JohnnyJ said:
I asked earlier and no real answers, so I went front to front. Seems ok.
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I went front to front as well to a Wilwood prop valve. I Googled, I asked ChatGPT.. consensus was modern vehicles/MCs had disc F/R and no residual valve so the MCs were equal on both ports, seems to work fine so far.
 
holdmypocket said:
I went front to front as well to a Wilwood prop valve. I Googled, I asked ChatGPT.. consensus was modern vehicles/MCs had disc F/R and no residual valve so the MCs were equal on both ports, seems to work fine so far.
Click to expand...
That's essentially why I asked the other day. My Subaru has discs all around.
 
If you hook up bench bleed lines and then measure flow from each port won't that tell us if the mc bore is stepled, biased etc?
 
Enhon Master Cylinder Bleeder Kit Replacement for 13911, 22 In Clear Hose, Clip, SAE and Metric Fittings Universal Fit, Complete Brake Bleeder Kit with PTFE Tape Amazon.com

Do it on the firewall?
 
Anyone see a problem with the push rod angle? Stock power brakes CJ pedal arm, with the stud removed.
 

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I'm looking for advice based on your collective experience. I have a Honda second gen ibooster with a 25mm master cylinder in my Unimog 404, running standard drum brakes. Based on my research, the fluid movement required to actuate all the wheel cylinders should be a total of 0.37 cu/in. With this master pushing up to 0.98 cu/in, I thought I would be fine. I bench-bled the master and bled the system thoroughly, but the pedal still goes almost to the floor before I get any braking. The odd thing is, when I pump the brakes a little, I get some more brake, but not a lot. I have a residual pressure valve going to the front and the rear, so I was surprised by the pumping thing having any effect. I thought perhaps I was doing the math incorrectly, so I bought the F250 HD master with the hope it would fit, but there is no chance. So now I am back to the idea that perhaps there is still air in the system? Or is the master too small for my system and I just need to find a bigger master that will fit? Any help would be appreciated.

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Bohalrantipol said:
I'm looking for advice based on your collective experience. I have a Honda second gen ibooster with a 25mm master cylinder in my Unimog 404, running standard drum brakes. Based on my research, the fluid movement required to actuate all the wheel cylinders should be a total of 0.37 cu/in. With this master pushing up to 0.98 cu/in, I thought I would be fine. I bench-bled the master and bled the system thoroughly, but the pedal still goes almost to the floor when I try to stop. The odd thing is, when I pump the brakes a little, I get some more brake, but not a lot. I have a residual pressure valve going to the front and the rear, so I was surprised by the pumping thing having any effect. I thought perhaps I was doing the math incorrectly, so I bought the F250 HD master with the hope it would fit, but there is no chance. So now I am back to the idea that perhaps there is still air in the system? Or is the master too small for my system and I just need to find a bigger master that will fit? Any help would be appreciated.
Click to expand...

If you adjust the cams on the backing plates to push the shoes out so that the brakes are bound up does the pedal firm up?
 
Not at all. I went so far as to adjust them to the point right AFTER they were dragging and still nothing. Really seems like Air in the system, but I would expect it to just be a mushy pedal, not an all the way to floor, then suddenly a little braking. I do have a wilwood adjustable proportioning valve, which I have zero experience with. I have tried almost all the way out, almost all the way in, and in the middle with similar results each time with that adjustment.
 
What master size is the factory Master?
 
Its a dual stage fill and pressure master (obviously manual) single circuit system. It has a 1.5" fill and a 1.125 pressure, so it isn't an apples to apple comparison, but overall I think I should have been in the ballpark.
 
JohnnyJ said:
Amazon sellls 0-2000psi pressure gauges for $10. It truly makes troubleshooting much easier. I highly recommend buying one or two and the related bits to tap it into your system while troubleshooting.

Click to expand...
I appreciate that. I was debating about going that route.

I had a hard time finding which masters alternatively would fit. Any insight there? There is the list circulating about which cars came with the iBooster set up, but nothing about the master cylinder sizes. The R1T is bigger, but there is no way I am paying the money these people want for an extra 2mm of piston area.

What I have found out is the following:
R1T = 27mm
Bolt = 23mm
Model X = ?
Model 3 = 25mm
Model Y = 25mm?
Model S = 26mm?
Lucid Air = 25mm
Odyssey = ?
Accord = 25mm
2017-2020 SD = 31.75mm


I didn't intend for this to be a basic troubleshooting of a brake system, lol. I have bled a few systems in my life. Early in the thread, it was mentioned that there was an experience similar to mine, but I wasn't sure if the fix was changing to a bigger master. That would obviously solve my problem IF my problem is that the master is just not moving enough fluid; I just can't believe that based on the numbers. If I am effectively pushing 0.37 cu/in within the first 1/3 of the pedal travel, then having to go all the way to the floor before anything happens seems to not make a lot of sense. I guess the master could be bad. I just dont want to throw a lot of money needlessly about this.
 
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Bohalrantipol said:
I appreciate that. I was debating about going that route.

I had a hard time finding which masters alternatively would fit. Any insight there? There is the list circulating about which cars came with the iBooster set up, but nothing about the master cylinder sizes. The R1T is bigger, but there is no way I am paying the money these people want for an extra 2mm of piston area.

What I have found out is the following:
R1T = 27mm
Bolt = 23mm
Model X = ?
Model 3 = 25mm
Model Y = 25mm?
Model S = 26mm?
Lucid Air = 25mm
Odyssey = ?
Accord = 25mm
2017-2020 SD = 31.75mm


I didn't intend for this to be a basic troubleshooting of a brake system, lol. I have bled a few systems in my life. Early in the thread, it was mentioned that there was an experience similar to mine, but I wasn't sure if the fix was changing to a bigger master. That would obviously solve my problem IF my problem is that the master is just not moving enough fluid; I just can't believe that based on the numbers. If I am effectively pushing 0.37 cu/in within the first 1/3 of the pedal travel, then having to go all the way to the floor before anything happens seems to not make a lot of sense. I guess the master could be bad. I just dont want to throw a lot of money needlessly about this.
Click to expand...
Is there a difference with the booster powered vs not? Even with the soft pedal, is it braking?
 
Outahand said:
Thanks for this thread.

Picked one up to try on my Bronco. 18 Honda CRV, $220 off ebay with both plugs and master. Master should be 15/16" according to my research. I hope it is not too small a bore but I will install and see. My Bronco has 89 Dana 60 fronts in front and rear so the big 2 piston calipers all the way around.

It won't go on until after a Rubicon trip in July.

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good am, did you get this installed. is so i missed it. thanks
 
chaplinfj60 said:
good am, did you get this installed. is so i missed it. thanks
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Life has been getting in the way....

It looks to be an easy install. Right before my Rubicon trip my booster took a dive and I ended up buying a new one so I knew I was good.

Mocking it up during my booster install looked very promising using the booster adapter.
 
ParadisePWoffrd said:
Is there a difference with the booster powered vs not? Even with the soft pedal, is it braking?
Click to expand...
Its firm when its off, and there is about half the travel. I am starting to think, that the fill section of the original master is having a much larger impact then I originally hoped it would. My plan at this point is to map out how far the wheel cylinders have to travel in real time before they apply force. at this point my ideas are limited to putting a larger master on, or perhaps manipulating the travel on the wheel cylinders. Any suggestions are welcome.
 
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