tt soarer over boosting

**sprintah!** · 07-06-2006, 02:47 PM

here's a little experiment for you..
go and grab your vacuum cleaner, turn it on.
sounds good yeh,.. running smoothly.
now restrict its intake with ur hand..
doesn't sound so good now does it.
sure the air coming out the other end is less but its working soo much harder.
this is whats happening to your mates turbos.

**oldcorollas** · 07-06-2006, 03:23 PM

Originally Posted by craigafleming

where's oldcorollas when you need him?

sorry, i was kind of ignoring this thread, hoping the cardboard idea would go away

shall we have a little science lesson?

engine is an air pump. ideally it moves a fixed volume of air each rotation
rotate the engine faster and the air sucked in increases linearly with engine speed.

now. plonk a piece of cardboard

with holes in it on the front. what does it do?
provides a restriction.. good so far

... now, the cardboard has a limit of how much it can flow, due to various reasons, but lets call it mach speed of the air thru the scientific holes.
as airflow (engine speed) goes up, at some point you will reach the maximum flow of the cardboard dooberwhacky. above this, the amount of air going in stays constant, but engine speed increases. this is how turbo restrictors in racing work. except they have a nice shape and for IPRA are? 36mm restrictors?? this limits the engine to a fairly specific power, BUT doesn't restrict boost.

doesn't restrict boost you say?

ok. say that your tricky piece of cardboard limits airflow to only make 15psi at 6000rpm. (ie, 30psi absolute). at 3000rpm, you still have enough airflow to make 60psi absolute, or 45psi boost. an easier way to limit boost would be to not plant the foot

or drive near where the turbos begin to boost.

as for turbo life.
as with IPRA and other forms of racing with restrictors, the limit (i think) is caused due to the pressure differential across the turbo. a turbo is a pump, but it is a dynamic pump. if you spin it fast enough, it will maintain a pressure differential up until the "surge line". (ie, up to a certain pressure differential depending on air flow. less airflow = lower pressure differential at which surge occurs, since you know abotu turbos, check a compressor map and see what you think)
the lower pressure will also pull the turbo rotating asembly forward more = more work on bearings.

so what happens if you whack cardboard on there? you decrease the intake pressure, resulting in a higher differential across the turbo, and potentially leading to surge.

also, with an unrestricted exhaust, the power to drive the turbine is still there, but the compressor spins more freely, so it's easier to overspeed the turbo.

so. higher pressure differential (same as running more boost), higher turbo speed, more axial force on the bearings due to lower intake pressure.

sounds good

as for the 13B turb, 264rwkw on 12psi. it's possible. assuming setup was perfect and revving to about 8-8500rpm... not bad for a 2.3L

you'd get the same out of a 1J at those revs.

as for your hobbs pressure switch solenoid ECU DVD player....

a hobbs pressure switch is a switch.

a solenoid is an electrical device with a plunger that is pulled back when power is applied.

you may only choose one.

as for the power claims. as a basic guide

Nm = (9402 x kw) / rpm
or
kw = (Nm x rpm) / 9402

so then
kw = (engine size x 100 x (1+ boost) x rpm) / 9402
where engine size is in litres, boost is in Bar or atm)

and Nm = engine size x 100 x (1+ boost)
or Nm = engine size x 100 x efficiency (in %)

you can then divide by your expected losses to get expected RWkw
note that this assumes 100% efficiency unless you factor in lower than 100%VE.

a rotor, for this scenario, has a VE of about 90%. ie multiply 1.3L by 1.8 to get expected torque.

as for the overboosting problem.

1) REPLACE the lines from the compressor to the wastegate with NEW UNADULTERATED PIPING, that is the correct size and doesn't leak.

if still overboosting
2) CHECK your wastegates actually operate properly.. by hand..

3) CHECK your cam timing.

4) it may be that the dumps are the problem

have you checked to see if the wastgate, when it opens, hits the inside of the dump pipe?
have you checked the design to see if the flow of exhaust THROUGH the wastegate is actually being reduced by shitty design of the dump pipes?

lastly, hold the gates open with a bit of coathanger, and see what happens

if you hold them fully open, and it still overboosts....

well.... you have a problem there sonny

Cya, Stewart

**oldcorollas** · 07-06-2006, 03:27 PM

oh. and it may just be that your boost gauge is shit.

**Vios-GT_07** · 07-06-2006, 05:05 PM

hm...

i understood that bit about the turbo's surging and stuff... made sense..

to sum it up.. it's pressure v.s. volume.. ?? sounds about right..? that cardboard piece will in effect

1. screw up the turbo really bad (especially the 1jz stock turbo's fragile bits)
2. won't limit boost period
3. reduce air volume which in turn means car runs rich? or just have lower combustion?

sorry i'm a noob.. please correct me if i'm wrong..

**jeffro ra28** · 07-06-2006, 09:22 PM

Originally Posted by Vios-GT_07

hm...

i understood that bit about the turbo's surging and stuff... made sense..

to sum it up.. it's pressure v.s. volume.. ?? sounds about right..? that cardboard piece will in effect

1. screw up the turbo really bad (especially the 1jz stock turbo's fragile bits)
2. won't limit boost period
3. reduce air volume which in turn means car runs rich? or just have lower combustion?

sorry i'm a noob.. please correct me if i'm wrong..

If boost isnt limited air volume will stay the same.

The air travelling threw the restriction will just have higher velocity because its being pulled threw a smaller diameter hence more stress on the hair dryers!

**EldarO** · 07-06-2006, 09:58 PM

Originally Posted by kremsra28

HE DONT WANT TO RUN THE SAME BOOST, !!

restricting the air that goes into the motor WILL lower the boost as the turbos cant draw as much air into the motor, thats why ahen you open up the air intake your motor will run more boost as it has more efficient airflow to the motor, so restricting the amount of air would be like putting it back to stabdard, the only thing is he dont have the factory snorkle to put it back to normal, the cardboard trick seems sensible as it can be varied wit the amount of air it will let thru via the size and amount of holes it has, by ppl saying it wont they are questioning the laws of mechanical engineering, more fuel + more air = more power.
my mate just wants to run less boost and doing it the cheapest way he can, this is a way that wont cost snything, i think that ppl are more into getting as much hp out of their car than reliability, which is wat the prev owner had in mind, sure the cardbord sounds crude and cheap, but so is the way that the air box has been modified to allow it to flow more air, but it does the trick.

there is nothing in line wit the wastegate actuators to bleed any boost out to truck them into running more boost, thats the prob.

as for the "i dont seem very confident" remark, i have as much knowledge or if not more than alot of ppl regarding the turbo motors, having owned quite a fewturbo cars, the last 1 being a 13bt s2 rx7 which had made 195rwkw and 13.1 sec 1/4 on 10psi wit only a few simple home made mods. the car owed me f**k all and the motor is to be fitted into my ra28, where it will have further more substantial mods as my budget is a bit better this time round.

the aim for this post was to ask for advice on HOW TO LOWER BOOST, it seems there are heaps of ppl that know how to raise it, some not knowing how to di it really safely at that, Or if any1 had a full standard air box or the front snorkle, which would RESTRICT the airflow thus allowing less boost to be run, my mate is on a very tight budget (no $ to spare) and i thought there should be some ppl who might be able to help, there have been some posts that are of help to stop the car hitting the boost cut, which is sorta wat i was aking for but removing the solinoid (which is actually called a hobbs pressure switch, for those who think i dont klnow much) will make for more boost,

thanks for the advice guys, but if restricting the airflow to back to how it came out of the factory is bad for the turbos, yet running such high boost is also detrimental the the life of the ceramic turbines causing them to fail, well wat in your eyes is good for them?? its plain and simple, he wants to run around 1bar of boost, the only way to do that is to undo wat is already done, restrict the air going into the motor, or restrict the air going out of the motor, the air going out of the motor will cost money, doing the air going into the motor wont unless he buys another airbox.

dude, the turbos only get "relief" from their work load when they reach the boost that the wastegate is set to actuate at.

reducing flow to the turbos will strain them, you may be lowering boost, and, im doubtful, but it MAY work, but by lowering boost, all your doing is running the turbos at their full, all the time, because, if you stomp on it, the turbo will spool as fast as it can to compress the air, if its not getting that air, it will keep trying, and keep trying, and keep trying, until you fuck the turbos, because they've been working full-time, as opposed to working at full for a short time, before the wastgate opens at the set boost.

By what i read about the car being thrashed, ghetto spec, never being warmed up, your friend made a mistake even buying the thing, tell him to expect a headache, from the moment he bought it.

also, Listen to Russ, he may be a bit curt at times (with me at least

) but its always good reason, hes owned a 1J powered car for quite a while, and he knows his shit, the fact that you dont even know the model code of the motor is reason enough.

Eldar.O.

**slide86** · 07-06-2006, 10:06 PM

dont worry bout it. everyone has had a go and everyone has said the same thing. everyone must be wrong accept "rota master" here.

give it a month or two and you will be back asking how to change the turbos. ill be the first to tell you to check this out.......

http://www.toymods.net/forums/showthread.php?t=7770

OVER IT!