[Mk2] [Turbo] Fan aluminium cowl issue on uprated IC

[JeffD]

Pic I took of fan sucking tissue against vent when testing I had wired up fan to make sure it was sucking not blowing :-)



What I always wonder is...

1) The switching of the fan only ever comes on when I'm stationary and usually goes off again quite quickly so why have an overide switch? (I actually have one on my car fitted by previous owner but never use it).

2) There must be a speed that the car does that matches the flow speed caused by the fan - if you have the shroud fitted (which I do) will not the fan act as a hinderence when air is trying to flow through cooler faster than the fan wants to pull it? (when you have shroud fitted)

Love to see some scientific results to compare stock fan and no shroud against spal fan and shroud.

[jimGTS]

Pic I took of fan sucking tissue against vent when testing I had wired up fan to make sure it was sucking not blowing

Image Replaced With URL For Quote http://i68.photobucket.com/albums/i2/je ... ler070.jpg

What I always wonder is...

1) The switching of the fan only ever comes on when I'm stationary and usually goes off again quite quickly so why have an overide switch? (I actually have one on my car fitted by previous owner but never use it).

2) There must be a speed that the car does that matches the flow speed caused by the fan - if you have the shroud fitted (which I do) will not the fan act as a hinderence when air is trying to flow through cooler faster than the fan wants to pull it? (when you have shroud fitted)

Love to see some scientific results to compare stock fan and no shroud against spal fan and shroud.

the fan comes on because of the ambiant engine bay temps...dont forget that sensor is near the turbo....the sensor certainly doesnt know anything about ic heatsoak of high intake temps.
not having and not using it alot makes having the kit fairly pointless. as you are waiting for the bay to get so hot that the fan needs to turn on.

when people talk about tests, scientific results. what are we actually talking about here??
cooling ambiant temps?
cooling the ic?
reducing the intake charge temp?
the amount of air it can flow?
at what speed is the fan a hindrance? (but are we talking about flow, or temps or what)...

[JeffD]

I'm mainly interested in a comparison between:

1) how much air is flowed by a stock fan verses a spal fan

2) How much/if any a shroud increases flow across the cooler bearing in mind that theres always gaps between the backing plate/cooler/shroud etc

3) As per (2) but the fan mounting shroud.

Happy with the cooler itself, really just trying to find what the improvement of the airflow is over standard to see whether the upgrade (of the fan/shroud) was worthwhile or not.

[jimGTS]

not scientific, but am sure its pretty obvious that more air will flow through the cooler with a backing plate than without...quite a bit more infact (as air would find the easiest place to go, and with no backing plate to block, it would rather flow around the cooler)...
amount of air being drawn; stock fan, uprated fan...a fair amount of difference am sure.

there shouldnt be any gaps between cooler and backing plate, and cooler and fan shroud...
if there is, just stuff foam down there to block the air escaping.

but in answer to the main reason about this thread, run a fan/shroud against no fan/shroud...noone can really give detailed facts. there are obviously pros and cons.

[JeffD]

dont forget that sensor is near the turbo

Just thinking...would that not be a good thing as if its near the turbo which is hot rather than in some cold dark corner its going to trigger your stock fan to come on earlier?

[jimGTS]

dont forget that sensor is near the turbo

Just thinking...would that not be a good thing as if its near the turbo which is hot rather than in some cold dark corner its going to trigger your stock fan to come on earlier?

i didnt say it was a bad thing.
simply saying your waiting for the bay temps to get so hot that the sensor is telling it to run the fan.
if you run the fan alot more, or like some people including myself, all the time, you are not at a stage where the bay gets so hot it heatsoaks. cause you are cooling or keeping it at a certain temp all the time.

[mattcambs]

Just another thought. The OEM IC shroud was no doubt designed to flow the side vent air effectively through the OEM IC. The Greddy IC is placed much closer to the vent, which may or may not actually improve the air flow. Who knows what sort of unhelpful turbulence is actually hindering air flow?

What we do know, though is that the good upgrade ICs are far less restrictive than the stock one. This alone means the charge is cooler (for a given boost level) because the turbo doesn't need to work as hard to produce the required pressure.

I wonder if the IC fan is really that important if you're using the engine lid fans?

[jimGTS]

Just another thought. The OEM IC shroud was no doubt designed to flow the side vent air effectively through the OEM IC. The Greddy IC is placed much closer to the vent, which may or may not actually improve the air flow. Who knows what sort of unhelpful turbulence is actually hindering air flow?

What we do know, though is that the good upgrade ICs are far less restrictive than the stock one. This alone means the charge is cooler (for a given boost level) because the turbo doesn't need to work as hard to produce the required pressure.

I wonder if the IC fan is really that important if you're using the engine lid fans?

but the stock ic has loads of gaps around it where its placed on the additional shroud. so air can easily past right by it. its also closer to the hot engine bay.
the greddy/xs is closer to the side vent which can only be a good thing,with the backing plate all the air is blocked to so it has to go through the ic. oem one doesnt have or do that.


who knows what was thought of when greddy/pp/ etc etc were designing the kits.

[JeffD]

I can feel an experimet coming on.....LOL :-)

[platmatt8]

TBH i don`t think the stock IC fan is going to be doing much anyway, it`s not central to the core for a kick off, add with it`s tiny.



I really have to agree with jim on placing the spiral fan without a cowel on the ic, as it resembles the stock set up but with greater pulling power and then you don`t have the issue off restrictions at high speeds plus it will be blowing hot air away from the ic given off by the exhaust.






OR thats what i`m going to do anyway.

[Nails]

Also another thing I have thought about the shroud and cowel. Im finding it hard to put into words though.
Like this, you're driving down the motorway with your heaters on full wack and the windows up, ooh nice and warm, pretty powerful, but open the window just a tiny bit and suddenly the heaters are even more powerful, would this same thing happen without the cowel and shroud, if the air can get past the ic would it not help pull the air through easier too?

[mattcambs]

Im finding it hard to put into words though.

Yes

sorry, mate. have no idea what you're on about!


IMO, the crux of this thread is whether having a fan with fan shroud actually blocks air-flow once the car is at speed?

Yes, the above setup will be the best for preventing heatsoak when the car is stationary, but does that really matter? Boost is only made when the car is at speed.

Also the stock IC fan sits to the side because that's where the hot air goes in; where it will blow air across the turbo exhaust housing; and it's the only place where it fits!

[ATSAaron]

Sorry to bring back an old thread, but a guy on the US boards mentioned this topic. 10 years ago ATS_Todd and I did some temperature testing using a thermocouple mounted inside the pipe after the intercooler. Even at 90 mph the fan helped keep intake air temps lower. The stock side vent provides almost no natural flow without a fan.

Just look down the side of your own MR2 and you'll see side side vent has basically no undisturbed frontal air flow. What would make air suddenly make a near 90 degree turn to go through the intercooler at speed? In fact I think the natural flow probably gets worse at higher speeds.

I do recommend you step up from the SPAL to the 9" high flow ATS Racing fan and shroud kit though. It moves almost twice as much air as the SPAL 7.5" fan. http://www.atsracing.net/IntercoolerFanandShroud.htm

Aaron

[LimeyMk1]

Good info Aaron, cheers. Did you do the test on both Mk1s and 2s. I'd guess the same conclusion would be reached for both.

[ATSAaron]

We tested on a MK1 Supercharged. That was a controversy too because there was some disagreement about which way the fan should pull. Our tests showed that the 9" fan worked best when pull air downward. The natural flow is in the opposite direction, but that pushed engine heat through the intercooler. Our coolest temps were found by directing the fan downwards to pull cool air from above the engine lid.

Aaron

[mattcambs]

We tested on a MK1 Supercharged.

What are your thoughts on mk2 Turbos and the fact that Toyota's intention is for the fan to come on when engine bay temps get too high, i.e when the car is stationary?

I've seen comments on here from tuners/mappers who always prefer to map on the road as intake temps are always lower than rolling roads with fans blowing into the side vents.

[ATSAaron]

Toyota also intended for a 11 psi fuel cut and only 200hp, so I would throw any thoughts about the OEM setup being ideal out the window.

Aaron

[mattcambs]

Toyota also intended for a 11 psi fuel cut and only 200hp, so I would throw any thoughts about the OEM setup being ideal out the window.

Aaron

That makes no sense because for the intended market 11psi fuel cut and 200bhp are absolutely ideal for what Toyota wanted to achieve in terms of market position and the long-term reliability of the motor. Anyway, Jap Turbos made 225bhp (rev1-2) and 245bhp (rev3 -> with fuel cut at a useful 18psi) which is a bit more "ideal"

I don't want to turn this into an argument I'm just not sure what your mk1 tests have to do with the airflow into the side vents of a mk2?

Also, never underestimate the engineering expertise and testing that goes into OEM design

[ATSAaron]

I don't want to turn this into an argument I'm just not sure what your mk1 tests have to do with the airflow into the side vents of a mk2?

Nothing at all, someone asked me if I have done any testing on a MKI.

What are your thoughts on mk2 Turbos and the fact that Toyota's intention is for the fan to come on when engine bay temps get too high, i.e when the car is stationary?

My honest opinion is that Toyota f'd up there. One of the reasons they didn't or wire the fan correctly is probably the potential for noise created by a good fan on the side mount intercooler.

Aaron

[mattcambs]

yeah they definitely did a bare minimum job of the intercooler/fan. They also put two huge vents in the engine lid and then blocked 70% of it up with the rain tray!