Like some others I have had some issues during track days with a lack of solid brake assist at the end of full power straights (most of them).

As such I have been pondering adding a vacuum canister but am unsure if this will help or maybe even hurt the issue. This led me to consider other possible fixes. Has anyone else had serious issues or were you just otherwise so annoyed by this issue that you were forced to act?

So as I see it these are my options.

1) Replace all vacuum lines as there may be a small leak or weak spot which is causing problems.

2) Replace the vacuum assist device.

3) Add a vacuum canister.

4) Strap on one of these and say ouch when you order it. http://www.jegs.com/webapp/wcs/store...10002_85962_-1

5) Do some combo of the above.

6) Just take my foot off the gas for a second prior to hitting the brake...

On second thought... screw #6. I want to stay on the juice to the last second and then have get stoppage like I threw out an anchor!

Thoughts?

 

Hmm, well i've been getting off the gas for a second or two and watching the vacuum build up then getting on her hard. I personally haven't gotten into it after a long straight because of all the horror stories...

What about this little guy?

http://www.jegs.com/webapp/wcs/store...10002_87534_-1

BTW your link above to whatever it is doesn't work, it redirects back to the home page.

 

This is a dumb idea, but I believe you have an '06. Prior to the '06 I believe, the ECU didn't have the "coast" feature where the car doesn't slow immediately after taking your foot off the gas.

I think this was added for increased fuel mileage or something, and I can verify, my '03 VIII would immediately slow down when I took my foot off the gas, my '06 IX barely transfers weight to the front during a throttle lift.

I'm not sure how the "coast" feature was implemented, but it might kill building vacuum when you first lift off the throttle. From what I understand a standalone ECU gets rid of this "feature", and maybe that can also be disabled in a re-flash.

Maybe someone who is a little more ECU savvy can chime in and tell me if I'm full of s**t.

 

There's a lot of discussion of 'throttle hang' in the ECUflash forums. The belief is that Mitsu put it in there to help keep the revs up between shifts. Some people are looking into the IACV table to try to fix it. I may start playing with it once I get the car prepped for autocross to try and tune the throttle lift behavior.

 

"Throttle hang" .. thanks, I couldn't find the right search terms.

 

Fortunately I haven't experienced the issue. I don't left foot brake fwiw. I have an 06 IX.

 

Actually I have an 05 RS and it is a bit of an issue.

The item at Jegs I am pondering is a electric vacuum assist pump. Item # 884-28146

The canister is possible with or without the pump but if I go that way I will most likely try the canister first and then add the pump if needed as it costs quite a bit more.

 

05-06 have throttle hang. Fuel shuts off below 3500 rpm's.

Replace your hoses with good silicone ones, zip tie everything, and get a vacuum canister. Hell I have some here from audi's, they hold more than enough vacuum for you. Easy to hide also.

Older audi's had low vacuum, so they all had good size cans. If needed pm me and I will sell one to you cheap, I will even give you mounting directions.

 

I have been wanting someone to try a vacuum canister and see if it cures the problem. I have the same problem at the end of the straight away at 135mph. Having a stiff pedal and no vacuum is not a confidence builder. Someone please post if this has worked for them.

Thanks!!!!

 

Lets assume that one of us does find a canister, how, where would you hook it up?

 

Another option would be to delete the vacuum assist completely. I tried disconnecting the booster on my Mazda and hated it, but from what my other competitors have told me is that once you get used to it, you have much better feel of brake pedal modulation, and you don't have to worry about a pedal that engages at different points depending on how much you've been on boost. I can tell you that after a 20 seconds hard on boost coming into a hairpin with a 500ft cliff on the far side, that I really really don't appreciate a brake pedal that changes from corner to corner.

Alot of the rally guys pull their boosters due to running anti-lag out on stages, so the car never really gets to charge up the vacuum booster. I've seen some nice booster deletes for subies, but am not aware of any for the Evo. If anyone knows where I can buy one, please let me know...otherwise, I may have my cage installer fab me one. If anyone is interested, I'll try to get price estimates.

Dave

 

I have no problem with doing away with the boost assist but I NEED some more something.

Right now I get to the end of the back straight at Mid Ohio and I have to STAND on the middle pedal. Please note... I am not a shrinking violet and can exert a huge amount of force on a pedal... more when I fear an off downhill at 140+mph and I need more grip than I am getting at this point.

In short, I don't care if I have to change master cylinders, swap for a different assist, add a canister or even a booster... I just have to get it fixed as I am willing to give up hp but won't futz around with the brakes. I like my brakes. I like me. I love me some me and want more friction in a bad way.

This will come to pass.

With that said I think I'm going to try the canister and then work my way up.

 

Ralliart makes a piece that replaces the vacuum booster:

http://www.stationgaragearnside.co.u....php?p=9&pno=0

Look about halfway down the page. I'm sure you can get a state-side rally shop to order one for you.

 

deleting the booster sounds like a great idea. no more worries and better brake pedal feel. I could live with manual brake pedal feel. just have to get used to it. As long as there consistency and no ill effects of doing it. did not see the part on the web page. have to look harder.

 

oops. found the item. 220 pounds. wonder if someone here in the US sell it or makes one. the vacuum canister may sound like a cheaper option and still keep the power assisted brakes. hmmmmm.... which one to do???