Over cooling a SC or turbo engine

is it possible and would be a problem to the performance of a car?

is there a perfect size for a intercooler or is bigger better?

 

dont know how you work it out, but a bigger intercooler means more pipework and therefore more pressure drop = less bosst getting into your engine.

 

Erm nope. does'nt neccessarily work like that.

 

oh ok my mistake. But you can have one thats too big cant you?

 

Overcooling.


A few of my mates run turbo/super charged cars and they got gauges to keep an eye on the intake temps. The G60 runs well Siht untill the intake temps go over 35deg and the turbo'd car is the same untill the temps go above 10deg. Both cars running over 250 bhp.


Ive heard that the best intake temp is around the 44 deg mark.

 

There is an increasing number of cars with turbocharged or supercharged engines on the road today, including turbocharged Japanese cars and the widely used VW Group 1.8 20v Turbo. The intercoolers used on these cars tend to be quite small and located in the front bumper, just in front on the front wheel arches. This position does not allow a good air flow and the small size of these intercoolers also restricts the cooling required for the inlet air.
One of the best solutions is to fit a Front Mounted Inter Cooler (FMIC). These are usually located in the centre of the car just behind the front bumper (around the same area as you would normally find the radiator). This usually allows a larger intercooler to be installed and also gains a much higher airflow which results in a greatly improved cooling effect - typically 20 - 30C lower inlet temps.
The main benefits are the cooler air improves engine performance and also prolongs the life of the turbocharger and engine as they do not reach as high running temperatures. As with all our performance enhancing modifications.

 

big is good

 

id have thought cold air being denser is good in general!

my g60 always used to feel more lively on cold days.

I'm intrigued by Bills post, I really thought that a big intercooler causes problems by increasing the length of the inlet tract. Perhaps its not boost pressure but I'm pretty sure it has some bad effect. of course the extra cooling may offset that.

 

Yea but too cold aint good. They see temps of about 35deg driving around and about 40 to 50 deg when giving it death

 

Ideal tempeture for fuel to be entering the engine at is around 40-45 degrees.

 

If you want more info try the forum the owners club for pulsar gtirs i think its gtiroc.com those guys know about turbo power and how to get the best out of a car. Many of the members a running 300bhp just using the normal mods we all do plus a skyline frontmount intercooler, thats about 70bhp over standard .

 

big is goodand cooler is better



Edited by: danmoody

 

Big is not good, the correct size is good. And the correct size IC with a well-designed turbo system is best. If [Dan] you're having to use an IC the size of yours then you have a problem with the rest of your system (or you're running a GT30 size unit) - either incorrect turbo choice (requesting too much from the turbo), poor downpipe design, poor compressor inlet conditions, poor mapping etc. All of this makes the turbo work outside of its optimum efficiency range, losing adiabatic efficiency and therefore heating the inlet charge further in the first place.
an IC twice as big may reduce manifold temps by a couple of degrees but if you're losing a few kPa before the wastegate take-off your turbo will work harder to reach the wastegate preset, heating the inlet charge further whioh is self-defeating.
It's a balancing act i.e. bigger is not necessarily better

cheers,
tt

 

so how do you work out a good size intercooler for an application?

 

from compressor out boost pressure targets and estimated mass flow estimate roughly where you are operating on the compressor map at say peak torque and peak power. using the adiabatic efficiency from the map (or just assume a figure if you can't be bothered) you can calculate the temperature of the air at compressor out.
if you know the temperature and rough mass flow of air you roughly know your IC intake conditions. Estimate what your ideal outlet conditions would be in terms of temperature and you then have a delta T and a mass flow so you can calculate the energy that needs to be dissipated. Assume an IC efficiency - e.g. a good figure say 75%. Use this information with the core efficiency tables/plots that should be available from the core supplier.
You could also look at idle conditions where heat soak is an issue and IC effy is very low to see if the core still performs OK (should be fine if peak torque/power is OK).

that's off the top of my head, but a reasonable guess i think.

cheers,
tt

 

TT even if it turned out to be BS it sounds good......

Jon there are plenty of books on the subject if you look around, (although some I've seen simplify it to "X BHP= Y IC core size"!)

I have "FI performance Tuning" by A Graham Bell (no, really!) and that seems to have a few calculations in it.......I think my Dad's got an Allard book which has more details in it.....

 

Rumbled !!

tt

 

HAHA I know that you know your stuff dude, no offence intended....but working where you do, you're guaranteed to have heard the old adage "Bullsh1t Baffles Brains"

 

works?? TT doesn't work, i wouldn't call begging working

looks like it time to get reading then.

or just go off the shelf and see what happens.

I'm just trying to decipher what the tramp man said into english, i'm getting close...

 

Not in my experience of trying a few IC's and CC, no noticable difference in lag at all.
I had this one made for my Mk4>
and this one on my ibiza







From the above different FMIC's, no difference in lag or power delivery at all.