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admc58
admc58 Reader
12/13/20 8:40 a.m.

Note for brake vacuum capacity... 

I had at least 3 cars run out of brake boost this year... Especially on boosted cars. 

When I'm driving I'm not "Off Throttle" for very long and I use the brakes to settle the front end without fully releasing the throttle in fast sections (This keeps Boost up and reduces lag)... What happens is, there is little time to rebuilt the vacuum to assist the brakes and the peddle goes "HARD" at the time when really HEAVY braking is required. 

My workaround (after blowing a good run by overshooting corner entry) was to release the throttle fully about 2 car lengths before the brake point and build vacuum so I could hit my corner entry point. 

So, I humbly suggest that you add additional vacuum capacity. Old VW's used to have egg crate looking plastic vacuum reservoirs that attached to the underside of the hood. I've seen them in other cars wheel wells. Should be really cheep to add.  

Kr, Alan

obsolete
obsolete New Reader
12/13/20 10:35 a.m.

Might be worth looking into adding a vacuum pump? The Chevy Traverse/GMC Acadia has an electric one that looks interesting, plenty of junkyard availability nowadays. Example: https://www.ebay.com/itm/362948507164

Patrick (Forum Supporter)
Patrick (Forum Supporter) MegaDork
12/13/20 12:21 p.m.

A vacuum reserve can with a check valve should be a $10 swap meet item.  I used to run one on my 54 chevy because it would stall sometimes so I could stop safely laugh

Stampie (FS)
Stampie (FS) GRM+ Memberand MegaDork
12/13/20 12:48 p.m.

Things you never thought of for the Challenge.  I think Alan needs a regular column.

gumby (Forum Supporter)
gumby (Forum Supporter) GRM+ Memberand Dork
12/13/20 3:11 p.m.

Manual brakes for everyone!

Brakes just slow you down....

admc58
admc58 Reader
12/15/20 1:46 p.m.
Stampie (FS) said:

Things you never thought of for the Challenge.  I think Alan needs a regular column.

LOL... someone might find my ideas intersting...

Yourself
Yourself New Reader
12/15/20 2:43 p.m.

Or use a hollow frame member as a vacuum reservoir (zero cost!).  As Patrick mentioned, a one way check valve is also useful. Lotus Elans used the front frame crossmember to hold vacuum for the pop-up headlights.  Even with a poor vacuum source from just one intake runner it held up well.

cruisermatt
cruisermatt New Reader
12/15/20 5:28 p.m.

Or just convert to manual brakes, or hydroboost for serious stopping power!

tb (minimally supportive)
tb (minimally supportive) GRM+ Memberand Dork
12/15/20 7:46 p.m.

In reply to admc58 :

I remember talking with you about this and how frustrated you were that you lost some time over it. My goal is to always keep my favorite driver as happy and fast as possible...

 

However, this is something I don't have a ton of firsthand knowledge about. Is it really as idiot proof as it seems? Are there some best practices that I should be aware of? My budget doesn't want the $20 hit but it seems worth it, right? Expert advice is always appreciated!

cruisermatt
cruisermatt New Reader
12/16/20 9:31 p.m.

In reply to tb (minimally supportive) :

 

You need $20 for a vacuum canister? That should easily be able to be made out of garbage and various adhesives 

tb (minimally supportive)
tb (minimally supportive) GRM+ Memberand Dork
12/16/20 9:38 p.m.
cruisermatt said:

In reply to tb (minimally supportive) :

 

You need $20 for a vacuum canister? That should easily be able to be made out of garbage and various adhesives 

Probably could be, but I don't berkeley around with rigged up brake parts and then give the keys to a friend so he can beat on the car mercilessly. I could make a roll cage out of pvc pipes, but not even I am that big of an shiny happy person. 

 

Feel free to modify your own brakes with garbage, just warn everyone to stay well clear of your car. My friends and family are worth $20 of new parts.

cruisermatt
cruisermatt New Reader
12/16/20 10:18 p.m.

In reply to tb (minimally supportive) :

lol. you sound like so much fun. 

And jokes on you, my entire car is made of garbage.

Now I want to build you a high quality vacuum reservoir entirely out of free materials, I used to weld stainless vacuum fixtures for aerospace and university testing rigs that were tested to high vacuum daily. My car has manual brakes though so it's going to have to go on your car. How much volume do you want?

tb (minimally supportive)
tb (minimally supportive) GRM+ Memberand Dork
12/16/20 10:35 p.m.

In reply to cruisermatt :

I am, actually, lots of fun. My sense of humor just doesn't translate well to the internet and you would need some missing context to fully understand it anyway...

 

To answer, though, I have no idea. That is why I was asking for advice. My car is small and the brakes are tiny but for volume I have no idea what would work.

 

Thanks for volunteering your amazing fab skills, but I might have to pass. It is a challenge build and anything you would create would have a market value exceeding the dollar cap.

Stampie (FS)
Stampie (FS) GRM+ Memberand MegaDork
12/17/20 5:53 a.m.

In reply to cruisermatt :

If this vacuum reservoir (even a limited edition of 1) is freely available to anyone then I'll take it if tb passes.

cruisermatt
cruisermatt New Reader
12/17/20 8:14 a.m.

In reply to Stampie (FS) :

How much volume do you want. 

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
12/17/20 8:24 a.m.
tb (minimally supportive) said:

In reply to cruisermatt :

I am, actually, lots of fun.

Debatable!

cheeky

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
12/17/20 8:32 a.m.

the volume question is such a simple one yet such a good one! 

Anyone know what rate of air/vacuum is consumed by the brakes? Does that change when the engine is 'in boost'? I'm sure we can engineer the bananas out of this. 

Maybe a better question is for Alan - about how long should we plan for vacuum to last? ie, if you do a full throttle blast up to 60mph, and then quickly shift to neutral and kill the engine, how long in seconds should you be able to stay in brake boost? Maybe until the car comes to a stop? But if you immediately repeat, can the car do it again?

My 2 cents on this is:

$0.01 - first make sure that on any boosted cars that the one way valves are actually not leaking. The stock systems should give you brake boost for quite a while after loosing the vacuum source, but if you are boosting into the vacuum canister then that's certainly not helping... If you've added boost to a stock NA car, then take a long hard look at how boosted factory cars run their brake boost vaccum systems.

$0.01 - next maybe look to double volume, or just get a second stock canister for your car make and model. I'd think if you plumb it in in parallel behind any one way valves, it should last 2x as long, which is probably good 'nuff. (as long as the above point about a correctly functioning system is remedied first). 

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
12/17/20 8:37 a.m.

BTW - this whole thread is something that SVreX has been championing for years. and I paraphrase:

The 'free factory replacement brake parts rule' is the most under used performance rule (and budget loophole) in the whole challenge. There is absolutely zero reason not to have great brakes.

Professor_Brap (Forum Supporter)
Professor_Brap (Forum Supporter) GRM+ Memberand UltraDork
12/17/20 9:06 a.m.

Ford diesels also have a fender mounted vaccum pump that are nearly free. 

Stampie (FS)
Stampie (FS) GRM+ Memberand MegaDork
12/17/20 9:36 a.m.
cruisermatt said:

In reply to Stampie (FS) :

How much volume do you want. 

Would ~125 ci work for you?

cruisermatt
cruisermatt New Reader
12/17/20 12:16 p.m.

In reply to Stampie (FS) :

Easy

tb (minimally supportive)
tb (minimally supportive) GRM+ Memberand Dork
12/17/20 12:21 p.m.
Robbie (Forum Supporter) said:
tb (minimally supportive) said:

In reply to cruisermatt :

I am, actually, lots of fun.

Debatable!

cheeky

 

What would you know about fun, NERD!

cheeky

No Time
No Time SuperDork
12/17/20 12:37 p.m.

Any GM from the 70s through 90s in the pick-n-pull should have at least a couple of these under the hood.  Probably most Mopar and Ford products will have their variation. 

Stampie (FS)
Stampie (FS) GRM+ Memberand MegaDork
12/17/20 1:22 p.m.
cruisermatt said:

In reply to Stampie (FS) :

Easy

Thanks.  After I beat tb I'll point out that my piece of garbage hand made vacuum canister displaces more than his entire engine.

Tom Suddard
Tom Suddard GRM+ Memberand Director of Marketing & Digital Assets
12/17/20 2:28 p.m.
Robbie (Forum Supporter) said:

BTW - this whole thread is something that SVreX has been championing for years. and I paraphrase:

The 'free factory replacement brake parts rule' is the most under used performance rule (and budget loophole) in the whole challenge. There is absolutely zero reason not to have great brakes.

Yeah, we realllllllllly reallllllllly want you to have great brakes. Please take advantage of this rule.

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