Over cooling a SC or turbo engine

paint colour, wheel size, brake size, speaker output, northern or southern equator, geometric tesselation, young's modulus, fibonacci sequence, boyle's law, simultaneous equations, fuel octane, wave/particle duality, monosodium glutamate, gyroscopic progression, polar maritime flow...


and that's just off the top of my head.

 

Are you taking the piss

 

also the climate and altitude

 

I believe the honourable TT pimps himself at a g a day or some such exorbitant figure to use a vastly expensive piece of massively complex software in order to calculate the size of components such as that.

unfirtunately it aint gonna be as simple as IC core /4 * weight of right foot = BHP...

Matt

 

so,, in laymans terms, you don't know.?

 

look for the closest production car spec to what you are trying to create, hence mitsu EVO front mount should be pretty good for a 300bhp 20vt. Obviously it's way more complex than that but i reckon an evo one is going to be a good compromise for a street driven car

 

thinking about it again, i think the EVO one may just be huge for homologation purposes, sorry i'll get me coat

 

I think it's a good basic rule of thumb, just dont use a vehicle built for rally homologation

 

I'm curious about the 90 degree bend, how come the factory downpipes have 90 degree bends straight from the turbo, and on the intake on the 20vt, how much of difference does this make given space is limited on most transverse engines ??

On the intake side i would have thought the 90 degree bend would cause the air to change direction and swirl better into the turbo ??

 

it's all because of package constraints pure and simple

on the intake side swirl can be beneficial but only at one point in the turbocharger speed range - in other places it will actually reduce inefficiency considerably. additionally any induced swirl will take energy from the air.
compressor efficiency is determined by the angle at which the flow hits the compressor wheel blades and this angle changes with speed, hence why you get a region of optimum efficiency on your map.
if you induce swirl, or put a bend pre-compressor, you change the spatial velocity across the plane of the inducer and change the characteristics and distribution of air hitting the compressor wheel. most of these installations squeeze and shift the compressor map - generally giving slightly better surge margin but reduced efficiency and mass flow capability, meaning that you will be producer hotter compressor outlet temps at increased compressor speeds when you ramp-up the boost - essentially why K03s and K04s go pop when tuned (the KKK turbos tend to have a relatively low max. speed limit of around 205krpm)

tt

 

well i've been saying that for seven pages and no-one listened

 

I wish this were true!!

having just had a custom build fitted to my 1.8t by Forge there is no way they take all that into consideration.
That might be true for a WRC works car, but any retail custom build is much more based on cost per unit production and "how many cars can we get it to work on"
My car had core size limitations due to the bumper bar, all they have really done is whack in the largest (without looking like a chav in dad's Evo!) core size and the straightest pipe work. It is custom only in its fit and construction, not it it's dimensions and air flow, they just don't have the facilities.
They road test/dyno it and if it gives gains then it works, if it doesn't they change it!

Still not convinced it is as straight as possible or as large as it should be for the application I have planned.
I am going to do something different with a deeper core in more airflow.

But saying that it does the trick now and makes a noticeable difference to response, fuel economy and power delivery at the top end and in hotter days.

Its a "suck it and see" development!

 

Right... It might actually be a backtrack, but I think I can add a bit to that conversation, I hope...

First of all, even the most knowledgeable people can make slips by failing to take into consideration a parameter or alternative. ( Even monkeys fall from the trees, sometimes ). And I am referring to a part that everyone refers to all the time as if it is the heart of this conversation, and still it is completely wrong, and that is that big intercoolers have more pressure drop.

NO, BIGGER INTERCOOLER DOES NOT NECESSARILY MEAN MORE PRESSURE DROP

Take an intercooler that has, for example, 10 runners and a length of 50cm.
If you make it larger by making the runners say 75cm, YES you will increase the pressure drop. (I will not post formulas here, but restriction to flow is proportional to length)
If, on the other hand, you add 5 more runners you will DECREASE the pressure drop, because you will decrease the velocity of air through the runners (Restriction is inversely proportional to the square of velocity)

Or, in other, correct -if crude- words...

So, it is a blatant mistake to say that bigger will have more pressure drop

So, does bigger equal better?
Answer is sometimes yes, sometimes no, and it DOES NOT only relate to flow et.c. et.c.
My answer is, IF you can get a bigger intercooler with the same or less pressure drop than the one you are using, YES bigger is will be better.
IF by increasing size you also increase pressure drop, THEN AND ONLY THEN do we enter the realm of complex calculations, estimations et.c.

No, he is not talking about choking velocity... He is (or should be) talking about the actual restriction the intercooler presents to the air -- a bigger intercooler, if, instead of getting longer, gets taller or wider, it will have LESS pressure drop than the smaller, and IT WILL BE BETTER IN ANY WAY REGARDLESS OF SETUP!
Because it will reduce more the temperature (even if only a little), and will have less of a pressure drop making the turbo's job easier.
OOTTOMH the only conceivable way that I can think of in which it could be worse would be a small increase in turbo lag if it is very, very much bigger.

It is not like that in all cases. Sometimes it is not a matter of "weakest link", sometimes it is a matter of cumulative gains or losses.
Let me explain: Each and every restriction, from the filter to the valves themselves, will detract from the actual quantity of air that gets processed in the engine by reducing its pressure.
In other words, each and every restriction in the engine causes a pressure drop, and if you can remove-decrease ANY restriction in the path of air, you will have gains. Small or big gains, it depends, but there will be gains.

Please excuse my english if I made any language-related mistakes!

P.S.: By the way, i do not mean that if you removed ALL restrictions (for example by eliminating intake runners or making the ports huge et.c. in a hypothetical scenario) you would have gains: Of course, as you approach the actual combustion chamber, other thing should get considered (air velocity and inertia, kind of flow et.c.), but, before you reach the inlet manifold runners, that is not an issue. less restriction=better.

 

Good well-informed post Quasar

The point made was that, for the SAME fundamental core design, a bigger core would give a greater pressure drop, although this does depend upon end-tank design and inlet/outlet entry conditions. In this case you'd balance pressure drop due to friction within the IC matrix Vs pressure lost due to expansion/contraction of the air in the end tanks (the latter is an area many overlook).

I have spent a large amount of time specifiying ICs in turbocharged systems and it all boils down to balancing the gains from increased efficiency Vs pressure drop and the general rule of thumb is that when one goes up..... you know the story.

It's quite amazing though how much a simple change of IC or charge air ducting can upset the balance of the entire system, so I still stick by my words that it's important to get the 'correct' size for your application.

The only point I would pick you up on is your comment regarding higher pressure drops leading to minimal transient differences; from doing a lot of transient accel. work I've found that it is very sensitive to compressor efficiency, which as you know during a transient is all over the map. It only takes a small change in this efficency to make a big difference to accel., particularly so to engines with lower levels of zero-boost torque. Again it's application specific, depending upon where you're operating on the compressor map, but a couple of kPa additional pressure drop can make a big difference to tip-in situations.

Cheers,
tt

 

So I can just use an old 8v Gti radiator as an intercooler then, with no ill effects? Nice one.
My spatial plane velocity compressor thing should be perfect, I worked it all out.

 

Well just got to say i have the neuspeeds front mounted intercool fitted to mine and it's alot better especiall on very cooled and damp days.But i also have the Forge Motorsport 1.8T+2.7T Eliminator DV Which can be ajusted for more boost and it all works well together.
And seening that clubgtinottingham have a rolling road day at jabba it will be nice to see what its kicking out how

 

hi guys, im no expert by all means but im doing a dissertation on turbo's at the moment for uni....

thourght this might solve a few agreuments...there IS an ideal i/c out there, if you can be bothered to do the maths you'll find it!

enjoy....

sorry i didnt put a link up but thats just a small part of the page....

cheers, james

 

bit more.....

hope this helps!

cheers!

 

last bit lol....

Pressure Drop

thats it.