So a question and I HAVE searched for this. I understand everyone needs research before going turbo and that's what I'm still doing. Oh, and I was about to get a tc, but didn't think it was worth pure price. But i saw the xb, drove a blackberry crush auto and fell in love with it. I still haven;t gotten it but planning on sometime in August before school starts.

For my noob question.

So as I understand, you press the acc. pedal, ur engine revs higher, u release more exhaust gases, ur turbo spools faster the more exhaust u release, and u get boost.

I understand you lose boost in a manual since you have to let go of the acc. pedal when u shift. What I don't understand is, why don't you lose boost in an automatic. My logic is this, if you still keep the pedal pressed, the rpm's are still gonna go down when the auto shifts. so aren't you supposed to lose boost then, since u have less exhaust gases? When I researched I hear ppl saying you don't lose boost in an auto, but I am asking WHY?

This has always been at the back of my mind, since I understand the average turboed xb hits boost after 2750ish rpms, so I need to know how/why I would maintain boost if I got an auto xb2 and turboed it.

 

I'm no expert but IMO the reason why a AT doesn't lose much boost when changing gears is because the throttle remains wide open, allowing enough air flow through the engine to keep the turbo spooling. With a MT, when you let off the throttle to shift, the throttle plate closes, airflow is reduced, the BOV opens to vent excess intake pressure, you lose boost and there is some lag time while the turbo spools up again.

The downsides to a turbo AT setup are that it's slower to build boost off the line and has more parasitic loss. However, the lower boost at launch may actually be a benefit due to reduced wheel spin vs a MT launching at higher rpm/boost.

 

pretty much exactly what he said right there.

keep in mind automatic and manual transmissions both lower rpms when they upshift, but since the automatic never closes throttle unless you lift your foot, you never fall out of boost.

but the other thing is that the automatic transmissions don't like too much power like the manual transmissions do. the manual transmission can take much more power, just gotta swap in a stronger clutch, but the automatic can only take about 250 whp before it needs some expensive upgrades to make it withstand any more.

 

pretty much keep your foot on the throttle like they said

 

Good info there. I plan to eventually boost my AT XB but didn't know how much whp this tranny could take. I was planning to run about 5-7psi and hoping for 200-225whp. IYO, can the AT handle that?

 

thanx a lot scionfred and draxcaliber....i always wondered that...

so some more questions if u will please

so i had always thought the amount of boost was related to the rpms u were running....but apparently....i guess....the engine creates a lot more exhaust gas than it needs to at like around 3000rpm

so, with that, since it's an auto, and i need it as a dd...i plan to keep it at a low 7psi...if kept at this psi....i understand dezod and turbotoyotas have turbos out already....would i be able to hit boost in 1st gear or more around second or third....just an estimate of around when i can expect to hit complete boost....no means expecting u guys to be dead on...

and another question...if running same everything....i understand gearing is diff between the 5spd and auto...but in a straight up drag race...wouldn't the auto win due to no lag except for the start up whereas the 5spd would lose boost every time it shifted??

thank u guys a lot. i hear scionlife really hates noobs...but apparently just ones that don't use the search button

 

i have a manual and i dont loose boost between shifts what you got on that lol

oh and dont buy the auto if your going to turbo it it wont take the abuse like a manual will

and no a auto one wont be as fast due to the slushbox taking power to lock up the converter kinda sucks you know just buy the manual its cheaper sportier and alot more fun to drive

i know im boosted any questions on boost can be answered by me lol im kinda the only one going wild with the xb2 thats not a shop

 

ha i no...i've been "scionlife stalking" ur turbo thread since u seem to be the craziest on here....

plus i have to say i love the black wheels on a blackberry crush...not so much a fan of the crimson mica...looks more maroonish imo but thats all ill get if i get an 2010...

but ya..i would get a stick
but
1. i don't no how to drive a stick
2. the college i go to it takes me around 1.5 hrs to travel the 14 miles there one way...worst case...usually around 55 min but thats still pretty bad
and as i understand even the most experienced driver will kill a clutch pretty quickly in 25ish mph stop and go traffic
3. can't i use the "tiptronic" and use that when i race? (not sure what toyota calls their semiauto)

but kittenjames....damn good job on ur ride and for being the guinea pig..im too scared to test stuff on my own ride seeing as i am just learning turbos and all

 

the stock auto dosent like the power you will have to lift off to shift and its not hard to learn how to drive a stick find a friend should take him about half a hour to teach you and you will never go back i drive my car in stop and go traffic all the time drives like a normal car minus how low it is but you will toast the auto trannie you have to lift off the gas to get it to shift so who knows just get the stick

 

Yeah, only a MT can handle boost. Maybe you should consider lifting when you shift?

 

no lift shift kills mu ignition till the clutch is released and if was at 250 hp it would have been fne but im well over that

 

wait...so i understand it won't want to shift w/more than 250 whp...but see i really don't want more than that...lol...everyone says that until they get a turbo and then they just go crazy...

but me...i really do plan of not going over 250whp...id be plenty happy w/that...just want some oomph and i hate the bolt-on way...

so anyway...so if i am getting 250 to the wheels but drive it gentlly wont the auto shift np....

in my mind...auto=best for my case since i am either going really fast or really easy....never inbetween...so i figure most of the time i can just put in auto, and then put in semi when i wanna race or just merge onto the interstates...

so i really don't mind having to lift everytime i need to shift...lol...this is cause the civic owner before me decided to not change the tranny fluid until 90k miles...now it hesitates so i typically wait a sec or 2 for it to shift and lift my foot off....so im actually really really reallly slow

so ya..

 

Personally, I've never heard of a electronically controlled AT needing a throttle-lift to shift. I remember having that problem with an old TH400 when the vacuum modulator was out of adjustment but that was a long time ago.

IMO, if you want a AT that's what you should get. I've heard that they are okay up to 250whp but to be safe, I'm planning on staying at or below 200whp with mine.

BTW, there is a vast difference between a semi-auto tranny like the Tiptronic and our slush-box with "Sport mode" shifting.

 

there is a boosted auto in miami he made 210 whp andd has to lift to shift

 

Seems odd to me. Maybe his tranny is buggered?

 

he was using the cxr kit he was the first one he had to liift to shift

 

Not that it has anything to do with this topic, but how's he doing with that CXR kit anyway?

 

Uh huh...

 

he was i forget his name he is the one that was working in conjunction to get the kit going he is the one that has the vids on youtube thats the guy i wish i knew his name

 

Kevin? It must be tough for them to collaborate between CA and FL.