Vacuum Brake Boost vs. Electronic Brake Boost?

[HoosierDaddy]

What exactly is the "electric assist" though?

I am familiar with hydro-boost and vacuum boost.

Vacuum being engine vacuum or electric vacuum pump assisted.

Hydro-boost being powersteering pump pressure.

School me!

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[jjack50]

The 2.0L and 2.3L EBs are still Mazda based, unrelated to prior 2.0Ls like the Zetec and 2.3Ls like the Lima.

The block of the 2.0 was based on the Mazda block design but everything else is different so I wouldn’t call the 2.3 Mazda based. In any case, there are no 2.3 NA engines with the same design. This is a rabbit-hole discussion anyway because it is completely unrelated to the brake boost design choices.

 

[rtsherry73]

I read the above. It made my head hurt.

 

[Tricky Dick]

The block of the 2.0 was based on the Mazda block design but everything else is different so I wouldn’t call the 2.3 Mazda based. In any case, there are no 2.3 NA engines with the same design. This is a rabbit-hole discussion anyway because it is completely unrelated to the brake boost design choices.

I agree, it's off topic. But the 2.0 and 2.3 are very similar. There's even guys swapping heads around between the two.

 

[colintrax]

The 2.0L and 2.3L EBs are still Mazda based, unrelated to prior 2.0Ls like the Zetec and 2.3Ls like the Lima.

So originally I was talking about the 2.3 duratech not the lima. However I found a source saying the 2015 ecoboost is a brand new engine. But now this link says the 2.3 ecoboost is in fact based on the old Mazda engine like I had thought. So maybe my assumption was correct but I removed that comment...
https://fordauthority.com/fmc/ford-...ec-engine-family/ford-2-3l-duratec-23-engine/

 

[colintrax]

The block of the 2.0 was based on the Mazda block design but everything else is different so I wouldn’t call the 2.3 Mazda based. In any case, there are no 2.3 NA engines with the same design. This is a rabbit-hole discussion anyway because it is completely unrelated to the brake boost design choices.

Disagree, NA engines do not need a vacuum pump. Keeping that in mind might explain why the 2.3 has a pump and the 2.7 uses electric.
Of course the 2.7 is used in the F150 which has naturally aspirated options still.
Wouldn't be shocked if electric assist becomes the go to standard.
Maybe this is just a weird leftover due to the 2.3 being a crate engine option (being shoehorned in place of NA engines) and the 2.7 not being a crate engine. More carry over parts saves money.

 

[HoosierDaddy]

The boosted portion comes from an electric actuator pushing the cylinder forward.

OUTSTANDING!!!
THANKS a bunch!

 

[Tricky Dick]

So originally I was talking about the 2.3 duratech not the lima. However I found a source saying the 2015 ecoboost is a brand new engine. But now this link says the 2.3 ecoboost is in fact based on the old Mazda engine like I had thought. So maybe my assumption was correct but I removed that comment...
https://fordauthority.com/fmc/ford-...ec-engine-family/ford-2-3l-duratec-23-engine/

It certainly is based on the Duratec, which is based on the Mazda L. Even the ecoboost wiki page falsely states the 2015+ 2.0 and 2.3 are clean sheet designs, with a "citation" behind a pay wall. However, when a Duratec and EB are side by side you can clearly see they are related. Here's a 09 2.5 Duratec vs a 15 2.3EB vs a 12 2.0 Duratec. A big difference is the open deck on the EB, which was not a change for the better.

 

[Mr. Nice]

On the 2021 Bronco tech specs sheet, I noticed the following:

The 2.3L gets vacuum brake boost, while the 2.7L gets electronic brake boost. What is the difference between the two systems? I haven’t been able to find much information online.

I’ve also noticed a few other differences between the two engines (besides the actual engine assembly).

For example, according to the 2021 Bronco Owners Manual, only the 2.3L gets a Turbo Boost Guage:

And while both engines get Trail Control and Trail Turn Assist, only the 2.7L gets Trail One Pedal Drive:

I wonder if that has anything to do with the different brake systems between the two engines?

Thanks ahead of time for the help!


Folks that have the 2.3 have vacuum assisted brakes vs the electronic found in the 2.7. Documented better stop distances for the 2.7. Just another advantage that many never consider.

 

[Norm A.]

As long as it doesn't come with vacuum windshield wipers like my 55 Chevy had I'm good

 

[KPLOBX]

I’ve test driven both manual and auto 2.3l bronco. Brakes felt mushy. Has anybody driven the both 2.3 and 2.7l? Any comments on brake feel on the 2.7l?

 

[Thrash Metash]

I have driven both and the 2.3L brakes were mushy compared to the brakes in the 2.7L. I don't know if that is true with all 2.3s and 2.7s but many have said the same.

That said, I did a bunch of trails in Moab and felt like the brakes worked just fine even when coming down a steep steep hill. There's just more travel in the pedal than I'm used to. Usually I would say the brakes need to be bled if they feel like that but maybe that's just the way it is on 2.3L.

 

[Rusty_McTetanus]

Normally aspirated engines create vacuum when not at full open throttle, maximum vacuum with it closed, like under a braking situation. Aside from some tuned intakes, the minimum vacuum is normal air pressure is zero gage (14.7lb per square inch or whatever local air pressure might be as that is the normal force pushing in at all times). It is used to increase the brake line pressure, enhancing the pressure applied to the calipers. Turbo cars push air into the engine and reduce vacuum at the same throttle positions. They can go negative vacuum because they are artificially cramming air into the intake using energy from the exhaust. Negative vacuum is called boost. The pressure above ambient outside air pressure. The key is that even at low load and RPM the intake vacuum can be low (getting closer to zero gage) as the turbos are always pushing some air in (a throttle is never 100% closed, needs some air to not stall when at idle). Can create situations where there is varying or not enough vacuum to help power the braking system. The electronic kind uses a pump to create vacuum to drive the brakes no matter what the engine intake vacuum. My supposition in this case is that the turbos on the 2.7 are negating enough vacuum for the brakes to be mushy in some instances, while the 2.3 is less affected because the turbo is not moving enough air to interfere with the braking system. Essentially, it 'spools up' well above idle speed and doesn't see up the vacuum when the throttle is closed.

Most turbo engines still generate enough vacuum to use vacuum assisted brakes. I suspect it's more of a packaging issue. The vacuum brake booster is pretty big and a twin turbo V6 takes up a lot more space than a single turbo I4.

 

[bbowisbald]

It's been used since at least the 80's on Fords. The Lincoln MK VII's had it with integral ABS. All it does is typically use an electric motor to create pressure for hydro-boost brakes. Instead of vac doing the "boosting", it uses hydraulic pressure.

They do it mostly as it is a much smaller package that can put out as much (or more) "assist" as a 12" dia dual diaphram vac brake booster (that came on say a 90's, F350). Very popular swap on classic bronco's as there is little space between even a 302 V-8 valve cover and where the MC is mounted on firewall. I put it on my 70 bronco.............

I have a simpler, single point version, on one of my trailers that I converted to 78/79 Bronco disk brakes. Works awesome, much better than even my brand new 14K, 26' alum car trailer drums. It uses the brake controller to progressively actuate hydraulics (brakes), just like the new bronco will.

I did the hydro boost mod on my 76' Bronco years ago. Booster from a Chevy Astro van and saginaw dual return pump from a Lincoln Mark 5 I believe. It would stop like a Corvette.

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