PDA

View Full Version : Brake Boosting



Cr0mster
04-07-2004, 08:53 PM
Being this is my first turbo charged car I am not totally sure how you break boost. Could anyone please give me some pointers please?

leaveit2bevo
04-07-2004, 09:00 PM
I think you only brake boost on automatics, so you can build boost without moving

EvolvedDSM
04-07-2004, 09:02 PM
Drag your brakes (gently) using the left foot (some use the e-brake), right foot on the gas and, as mentioned, you'll need to be moving.

Dr. Evo
04-07-2004, 09:31 PM
Beautiful technique to BURN OUT YOUR CLUTCH! They are weak enough for God's sake :lol: ! Anyway, what is 19 psi by 3500 rpm NOT fast enough spool for you??

Cr0mster
04-07-2004, 10:41 PM
I am not wanting to do this to my car. :) I was just wondering since I keep reading about it in other forums.

leaveit2bevo
04-07-2004, 10:52 PM
why would you want to do it?

EvolvedDSM
04-07-2004, 11:03 PM
"Instant" boost.

leaveit2bevo
04-08-2004, 12:05 PM
if you launch the car and keep the rpm above 3k thats instant boost.

CACalomino
04-08-2004, 12:30 PM
I have watched on BEST OF MOTORING and on the EVO in the togi he would role about 10mph or so then mash the gas at same time pushed in the clutch to the floor wile still holding the gas down and then let it out real fast it hit boost instantly.

Basicly its like shifting gears fast but keeping the gas down to the foor but your not shifting just the foot work.

But it will kill the clutch for sure over time

-Chris

Dr. Evo
04-08-2004, 12:41 PM
These cars have basically no lag anyway. I just don't see the point.

mr. evo
04-08-2004, 12:52 PM
You've got to be joking on the no lag statement... right. Please say you were joking.

EvolvedDSM
04-08-2004, 05:15 PM
I don't see the point either. If you're experiencing lag, you need to downshift--problem solved.

Dr. Evo
04-08-2004, 05:41 PM
19+ psi at 3500 rpm is lag?? Have you ever driven any other turbo cars?? My DSM would boost 15 psi by about 3800. And that was with many mods and alot of horsepower.

Ricardon
04-08-2004, 06:42 PM
Of course the car has lag, and unfortunatley for this car it doesn't really make too much power before boost comes on. The spool is fairly fast for the amount of horsepower the car makes though. The midrange of this car is downright phenomenal, but down low she licks balls. What Chris is talking about is power shifting, which IMO is completely useless not to mention hell on your clutch. If you have enough experience you can shift fast enough without having to power shift. I personally see no reason to "brake boost" with a manual transmission..at all. A clutch kick for a drift is a lot different, people may be confusing those two as well.

CACalomino
04-09-2004, 12:11 AM
I guess I needed to make my statement more clear its not a power shift well kinda its kinda like doing a roling dragg launch in a sence your roling and u smash the gas to surge forward as the car starts to take off u keep the gas down push teh clutch in super fast and let it out just as fast I guess this built boost in the EVO in the vid cause he jumped 3 cars in 1.5 second period on the AMUSE S2000

BUt if your worried about boost lagg get a lighten flywheel it will help the car get to boost alot faster and get u in the sweet spot ASAP

mr. evo
04-09-2004, 07:47 AM
Shop manual driving at its best... on the road is different. You can hardly compare a dsm car to an evo. The fact of the matter is all turbo cars have lag, so even if it does start to spool at 3,500 rpm, whats happening in the begining stages... LAG! Why do you think rally cars have ALS on there cars?

As far as this "brake boost" goes... I don't see the point either. Just learn to drive the car great first. You can be a wicked driver and not have to do anything crazy, just be a smart driver.

Ricardon
04-09-2004, 08:52 PM
Hey Josh, you forget that there are no "smart drivers" here LOL!! We all do stupid shite hehehe. Like driving hard into a corner and clutch kicking in front of a cop with his gun pulled! Not a very good idea BTW, you might miss big NFL playoff games on TV and have to breathe the fumes of mass amounts of pepper spray form the clothes of some rediculously drunk 300lb dude. That and you might have to spend a few hours with a crazy bald British guy and another dude who claims to know a thing or two about mitsubishi cars. What up!! hehehe.

mr. evo
04-10-2004, 08:29 AM
HHHHHHHHAAAAAAAAAAA! I was waiting for that.

trinydex
07-09-2004, 12:23 PM
it's called left foot braking, at least the technique to reduce turbo lag (left foot braking is also used to describe a few other techniques). it's the idea that if you are in a turn, you want higher rpms but a lower speed so when you exit corner you can have max boost with minimum time getting there. i believe the idea was born in rallying and i think in the evo, iv or v.

they also have anti lag systems which make you run rich after shift and push gas out into your manifold where it explodes and spins your turbine really fast.

these of course are all bandaids to a problem that will never go away, if you don't want lag get a supercharger :].

QuickShifter
07-09-2004, 03:57 PM
I guess I needed to make my statement more clear its not a power shift well kinda its kinda like doing a roling dragg launch in a sence your roling and u smash the gas to surge forward as the car starts to take off u keep the gas down push teh clutch in super fast and let it out just as fast I guess this built boost in the EVO in the vid cause he jumped 3 cars in 1.5 second period on the AMUSE S2000

BUt if your worried about boost lagg get a lighten flywheel it will help the car get to boost alot faster and get u in the sweet spot ASAP

Evo's arent drag cars...PERIOD

gt40
07-09-2004, 04:40 PM
The fact of the matter is all turbo cars have lag, so even if it does start to spool at 3,500 rpm, whats happening in the begining stages... LAG! Why do you think rally cars have ALS on there cars?

I can show you the aem ems log I did on the way home today- 25 psi at 3756 rpm and making 10 psi at 3400... You are right though about lag if you don't match the turbo to the motor properly. It amazes me folks putting gt35s and other missmatched turbos for driving on the street and the track. I had to learn this the hard way with my old gt40 setup :(

Now, thanks to blax94gsx, I am getting full spool by 3700, not just start to spool :twisted:

leaveit2bevo
07-09-2004, 04:45 PM
Not all turbo cars lag what about the twin turbo in the supra? it had a small turbo for no lag and a big turbo to take over when the small one ran out of air.

Ricardon
07-09-2004, 06:14 PM
Not all turbo cars lag what about the twin turbo in the supra? it had a small turbo for no lag and a big turbo to take over when the small one ran out of air.

Something has to spin that small turbo to Bevo. While the lag in a TT car, that has 1 big 1small for just that purpose, may be reduced...it's still gonna be there.

Left foot braking in certain corners helps to stabilize the car...rather slow you down a little bit so that you don't have to lift to slow down until your wheels are pointed straight and you can go all brake. Bad bad bad to lift in corners!!

trinydex
07-09-2004, 08:32 PM
the two turbos on the supra and any other twin turbo car are the same size... hence the term twin. they are twin sequential, which means the other turbo comes in at another time. if you have a staggered turbo set up you have different back pressures over the motor which is bad.

it is virtually impossible to setup a non twin, staggered turbo setup unless you put them inline or something. and if you put them inline you will get lag when the big boy spools up anyway.

twin turbos are beneficial because it splits the engine in half which means the exhaust from half the engine goes to one turbo. this means you can put a smaller (read faster spooling) turbo but get the same or more power output because you have two.

big engines move lots of air, smalls turbos are caps to that, there are many examples of stock cars that have tiny turbos that are the limiting factor. there are also examples of cars that are not well mated with their turbo, too large and you get lots of lag. twin lets you get the small turbo size without comprimising the flow capabilities of the engine.

if you want to think of it visually, one large turbo is a big O but two twins are two small os... o o the two small os have more area than the one big O but still spool like small os which means they move more air, where the O only flows as much as a O and spools like an O too.

leaveit2bevo
07-10-2004, 12:49 AM
are you positive of that? I know the 300zx works like that 2 turbos the same size but I thought the supra had to different size turbos.

trinydex
07-10-2004, 11:45 AM
positive

leaveit2bevo
07-10-2004, 12:26 PM
well guess what I did some research on the supras twin turbo set up and every single site said that it had a small turbo for quick response and a large turbo for full trottle.

Ralliartpnoi
07-16-2004, 08:16 AM
well guess what I did some research on the supras twin turbo set up and every single site said that it had a small turbo for quick response and a large turbo for full trottle.

hahaha my friend said to me at work one day. "dude i have the best idea in the world. for a twin turbo set up, why dont you put a small turbo to spool up fast and a big turbo to give you nice amounts of power. no one has ever done that yet and ill be the first to show everyone." HAHA imma have to give him bad news about his "great idea that noone has ever done".

reminds me of the time my other friend thought a great idea of making a electrical powered turbo that will spool you straight from the beginning and then switch over to regular traditional exhaust method after a certain rpm. about a year later i read in super street (i think it was SS) that mazda made a prototype renesis motor in the same setup. my friend got pissed. he could have sold a new design off to some company for millions. LOL

IMO imagine if you get a idea no one ever made, you could sell that for so much to a company if it works.

Boosted
08-08-2004, 02:23 PM
I have watched on BEST OF MOTORING and on the EVO in the togi -Chris

are you refering to "touge" ? not togi?

sidoze
08-08-2004, 03:31 PM
I assure you that both of them are the same size, I'm at the tustin meet every thursday so your welcome to look if your bored. 8)

Also I run the car in TTC, which is both running at the same time. I get 14 psi at about 4,200 rpms and its absolutely the coolest thing ever.

Normally though the first turbo is running, and then a butterfly opens mid 2000s to allow the 2nd one to start spooling and at 4,000 it transitions to both. Theres a dip in timing and boost when this happens though and its quite annoying. Problem is though if you turn up the boost the 2nd turbo gets hit hard when it transitions and the first turbo gets over spun before that, makes for a short life for the twins, hence lag monster mode that I run around in.

Even the after market supra turbo kits are lag tastic, check out that green supra in the upcoming USCC. It has a PT67GTS, spools in the mid 4000s. And if you want "big yo" powah out of the car your looking at around 5,500rpm spool. Most of these 1000hp guys are making full boost at right before 6k. Check out t04r.com sometime if your bored.

Lag is cool if your getting your neck broken after it spools :P

drmosh
08-08-2004, 04:05 PM
I assure you that both of them are the same size, I'm at the tustin meet every thursday so your welcome to look if your bored. 8)


But Mike, you don't know SH$T... j/k...

That doesn't make sense though, why would sequential turbos be the same size?

Chris in SD
08-08-2004, 04:19 PM
The size thing isn't a big issue - there is a flapper-type valve that opens to the second turbo at higher rpms (also on the '93+ RX-7). One turbo doesn't necessarily "feed" the other turbo, it is just used for lower rpms while the other is for higher rpms. The 911 Turbo uses twin turbos, but not sequentially since the flapper valve can malfunction. Their solution was to put a turbo on each cylinder bank and have them operate simultaneously over the entire power band. If you remember the Skyline at the last meet, it had A'pexi turbos that were the same size. The flapper issue is another reason a lot of guys swap to a larger, single turbo (plus the obvious power gain).

trinydex
11-24-2004, 01:28 AM
i don't know what break boosting is, but what some people are reffering to is left foot breaking. that's the idea that you use your left foot to brake so you don't release throttle and dump spooled pressure and have to repressurize your intake tract. this is a very advanced technique that does not wear out your clutch, but your brakes. you don't wanna do this with the ebrake really... cuz it's not as precise and also you don't wnat any unnecessary rear end loss.

also the thing you see them do in best motoring is just a launch from roll. but another clutch braking technique used is most used when they're drifting, which doesn't give them instant boost, but instead locks up their rear end so they can initiate a drift. you will also notice another technique they use quite a bit, when they come out of a high speed long sweeper they will "tap" the brakes twice or so, this is to counter brake (caliper) knockback. which is the phenomenon of brakes getting pushed back by the rotor after a turn (rotor camber changes and hence pushes against pad and opens caliper). knockback is bad because the next time you brake the fluid needs to push the pad back to "normal" position then push more to apply braking pressure, which translates into your brake pedal dropping to the floor unexpectedly (bad) but this is not quite left foot braking either.

btw... the two turbos are the same size... the butterfly valve only diverts exhaust from one to both, so at low rpms only one turbo is driven by all the exhaust gases, therefore faster spool, at higher rpms the valve opens so both turbos can operate and provide max boost.

trinydex
01-07-2006, 07:02 PM
Beautiful technique to BURN OUT YOUR CLUTCH! They are weak enough for God's sake :lol: ! Anyway, what is 19 psi by 3500 rpm NOT fast enough spool for you??

what? when you brake boost you don't have your clutch in....


I have watched on BEST OF MOTORING and on the EVO in the togi he would role about 10mph or so then mash the gas at same time pushed in the clutch to the floor wile still holding the gas down and then let it out real fast it hit boost instantly.

Basicly its like shifting gears fast but keeping the gas down to the foor but your not shifting just the foot work.



I don't see the point either. If you're experiencing lag, you need to downshift--problem solved.

downshifting is not always an option... particularly if a shorter lower gear does not last the length of the turn. downshifting also does not solve the problem of transient boost response.
But it will kill the clutch for sure over time

-Chris


this is also known as a rolling launch... and that's all it is... you just drop the clutch after you rev it up some from a roll instead of from a stop.

theoverachiever
02-20-2006, 04:09 PM
Beautiful technique to BURN OUT YOUR CLUTCH! They are weak enough for God's sake :lol: ! Anyway, what is 19 psi by 3500 rpm NOT fast enough spool for you??

how is brake boosting going to burn out your clutch? The clutch is fully out, left foot on brake, right foot on gas. I did this in my wrx all the time, you can get a nice jump on people on the highway

Knower
02-22-2006, 03:04 AM
Beautiful technique to BURN OUT YOUR CLUTCH! They are weak enough for God's sake :lol: ! Anyway, what is 19 psi by 3500 rpm NOT fast enough spool for you??

how is brake boosting going to burn out your clutch? The clutch is fully out, left foot on brake, right foot on gas. I did this in my wrx all the time, you can get a nice jump on people on the highway


A healthy enough dose of throttle and brake and the clutch would slip. Burning out the clutch is when the clutch gets worn in a way that it no longer will hold the torque available from the motor. By braking while on the throttle you can definitely induce enough torque to break the stock clutch loose. Just because you did it in your WRX "all the time" doesn't make it impossible for this to cause problems with your clutch. Maybe think about it a little.

trinydex
02-22-2006, 03:12 AM
you're not braking with that much force... and if you are you're doin' somethin' wrong... you're not suppose to induce enough force to break traction on anything, not the tires not the clutch, it's meant as a way to modulate your speed in either direction without changing the balance of the car. modulate being the key word, it's not meant to stop your car and it's not meant to launch it.