rapidcossie

After seeing my car on the rollers recently I was amazed at the differences these can make.

What are peoples experiences?

Stavros

differences in what way?

rapidcossie

I know what I say and have expericed but am interested to see what others thoughts are?

Could be a good thread if it gets technical

Andy_R

iTrader: (3)

re-word what your trying to say mate, either that or explain to me what I should be reading - i dont understand.

rapidcossie

I was suprised the difference the temp of the exhaust etc made on boost etc.

Stavros

As in when it spooled up? As it should spool way faster when loads hotter, its heat that mostly spools turbos...

rapidcossie

yeah I knew it made a difference but it was massive!

Stavros

from wat ive read, its something like 80% heat energy that does it versus 20% flow/pressure, or something ridiculous.

rapidcossie

Judging by the differences I have seen it wontbe far off that.

I was seeing over a bar of a difference at some rev points

Andy_R

iTrader: (3)

cheers Euan, I get you now

I guess the only experience I have would be relating to the increaase in temp caused by the fitment of an different exhauts manifold and its possitive effects on lowering boost threshold.

rapidcossie

Would Imagine the long manifold like on your will see a massive difference when hot and cold

NEIL A

iTrader: (6)

So by wrapping the manifold to keep the heat in you should see gains in boost threshold.

SteveH

Bit of a beginner question here: what is boost threshold? And what would be considered a gain or a loss? Thanks. Good thread Euan

rapidcossie

theoretically but I dont really think normal wrap is actually that good Neil.

NEIL A

iTrader: (6)

Dont Know Euan the stuff i had on my old down pipe before it got trashed seemed to work, when it was on the rollers it did glow still but as soon as Alan let off you could feel the difference around it and the uncovered sections in the bay.

rapidcossie

Maybe you get different quality of wrap?

The stuff I bought went brittle and fell off/did fuck all for the heat

Andy_R

iTrader: (3)

just the starting point the dictionary says:-

The place or point of beginning; the outset.

So the point at which your car makes positive boost, usualy measured against RPM

SteveH

Cheers andy
Im really interested in stuff like this, normally have my head buried in the technical essay section, all info helps

Steve

cossiemanden

When u put wrap on an exhaust, u have to make it wet first, otherwise it will fall off pretty quickly

HAve tryed many times, that the first time u step on the throttle, it´s not as fast as if you do it shortly after again, thats because of the turbo and manifold is heated up, so the speed and temperature is raised.
Same effect wrapping has btw.
When we were mapping mine, we were playing with the exh temp to se how it effected, the boost threshold, pretty interesting

Andy_R

iTrader: (3)

Say that is right Stav, then why dont we hear more about the 80% heat energy? by this I mean most technical post focus on flow(20%).
Is there really so little info about the heat part in the public domain?
I want to learn more, please! Thanks!

Stavros

Because most stuff talked about on internet forums and even by "tuners" is said by clueless morons who just think they know what they on about when they dont.
And one person says some bollocks, 10 more people read it, each tell 10 more, and so on and so forth.

Hence why myths about wastegate chatter and thousands of other things are common and are far more believed than the actual truth.

Ive had people, tuners even, argue till they are blue in the face that heat makes almost no difference to spoolup.

BTW, i dont know if its 80%, but what i can remember of tests etc they was saying it was something along those lines.

pee vee

So a turbo could give (in rapidcossies experience here) 1 bar of boost MORE at a X revs,. than when the manifold is cooler??

or am i getting this totally wrong?

But if so

surely that makes mapping a little more difficult dont it?? as it could only be mapped for whatever temps were being experienced at the time.
and how come we dont hear more about closed loop EGT systems

Andy_R

iTrader: (3)

yeah yeah cool, I appreciate the 80/20 maybe isnt an exact science but its certainly a big enough effect in favour of heat to matter and if it matters then it would be nice to know more about.

rapidcossie

you are 100% right pee vee.