WREXY

http://www.wrxsa.com/tech/techBra.html

In the above link, there is a good technique for measuring airflow to the bonnet scoop. Although they did it to see if a car bra restricts air to the scoop, I thought it may help someone that's capable of on here, to perform a similar test at high speeds, without a bra offcourse, to see if our cars are in danger of not getting air to the scoop at high speeds. This test would be for the classic shaped scoobs.

A test was also done in that article without a car bra, but unfortunately it was only conducted to speeds of 110kph (67mph)and there was no restriction.

Has anyone on here done a similar test to speeds over say 100mph, (without a car bra), to see if high speed has an affect on airflow into the scoop and intercooler? Or does anyone that can copy the technique from the article want to try it?

I remember reading about airflow restriction to the scoop at high speeds, but I can't recall whether we had definate answers.

Cheers,

Wrexy.

Beastie

iTrader: (2)

WREXY
how you doing. Funny enough I have been thinking about this recently and wondering why no-one has brought out a scoop spacer that could be fitted under the scoop of classic shape cars to raise the scoop up to STi 8 levels. It could also be formed as a scoop splitter so that air flow is improved.

Following these posts previously, i seem to remember that the flow over the intercooler was affected at high speeds because of a low pressure area formed on the bonnet.

However, it strikes me that with the vent covers removed on the bonnet that in these circumstances the flow through the intercooler may reverse and cooling may still be maintained. This was never seen to be commented on.

A water spray system on the intercooler a la STi is meant to make a big impact and I will be trying this myself shortly. I already have a set of STi nozzles and looking at a control system.

I am also looking at the APS topmount intercooler, (I know that front mount is supposedly better) and trying to persuade myself to part with the cash.

Beastie

WREXY

Hi Beastie,

I'm fine thanks m8.

I think you will be OK getting the water spray system with the cold climate Scotland has.

From what I've read, if you go for the APS TMIC, it will be better than the stock item when cruising, but if you're stuck in traffic, there will be more heat soak retained by the intercooler being larger and you'll have to be carefull when you find an empty stretch of road in front of you at a set of traffic lights when taking off. You'll have to go slow for the first 200 metres or so to get the air in, to cool down the intercooler before planting the foot down.

This is not to say that you don't need to take the same precautions with the stock item offcourse.

I think where you are, you mainly cruise, rather than being stuck in traffic anyway, so go for it.

If I go for anything it will be a FMIC cos with our extremely hot ambient temps here in Greece I feel that a FMIC is the best option to battle the heat and it gets rid of the fear that the intercooler won't get sufficient airflow at high speeds.

Cheers,

Wrexy.

Forester_GP

Wrexy, greek mode on < gia sou > off

Beastie, i've ordered the latest APS+duct splitter for my Forester '00 and hope to get it within the next couple of weeks. Once i get, i'll be able to post some findings as i've already fitted two K-type sensors (pre & post cooler)measuring temps.
Also the 1.5 PSI less pressure drop compaired to stock should make a noticeable difference, ie turbo has easier work to do lowering intake temps even further.

Heat soak can be diminished with the use of high CFM (3x200 cfm) Delta fans that could be mounted underneath the IC sucking air through it. I'm currently using the above config (with smaller fans) and in city traffic, intake temps stay quite stable once the fans are operating. I'm afraid, though, that the new IC being quite taller would make near impossible the fitment of the fans.

Best WS, i think is the Autospeed's which costs around $125 and is quite intelligent (saves a lot of water).

George

Beastie

iTrader: (2)

Forester
that sounds interesting, i await your results with interest to see what difference in temps can be acheived.
Incidentally water injection (not water spray) can have a huge effect on the temperature of the air charge, lowering it quite considerably.
The fan idea is really quite good.

What horse power is your car putting out now WREXY? and are you happy with it or wanting more?

Unfortunately, I have now got used to my current level of horsepower and some further gains are now necessary irrespective of warranty!Its a slippery slope!
Beastie

john banks

21st Century Performance by Julian Edgar (T-uk has my copy so can't look) has a chapter on this, and IIRC, some wool strand testing on an Impreza body generally.

You may also want to stick an inexpensive thermocouple just after the intercooler.

I tested my uprated TMIC with MD304 running 1.4 bar and at very high speeds and the charge temperatures were not silly. I believe a few others did the same.

What you may wish to consider is that at sustained high speed you are often holding the vehicle at peak power for a prolonged period. As a result the turbo is working at high pressure continuously. Most road cars have intercoolers that are heatsink/heatsoak devices with a rather slower mechanism of heat exchange with ambient air, so they rely on off boost periods.

We did some testing at Knockhill on a decatted UK car at various levels of boost and found that on a typical Scottish spring day the intercooler temperatures reached 52 degrees after 5 laps driven by a complete lunatic running 17 PSI midrange boost.

A VF23 car on the same day running 19 PSI midrange driven by someone only slightly less lunatic only reached 45 degrees.

Interestingly on the track the highest point for charge temperatures is in the slower bits, and it is still quite high at the hairpin before the main straight, it then drops as you get 100-115 on the straight before breaking for Duffus dip. It then climbs again through the slow bits. Each lap it doesn't quite recover to where it did the lap before, unless you run granny levels of boost. I take the charge temperature to be in short an equilibrium between heatsoak and heatsink which is affected by turbo discharge temperature vs vehicle speed or flow through the scoop.

Intercooler spray makes a few degrees difference at Knockhill, an on edge ignition map still detted after a few laps on a warm day unless you ran lower boost on track than on the road.

A vague rule of thumb is to retard timing by 1 degree per 5 degrees C increase in charge temperature over 40 degrees. Some ECUs have maps for this.

Most have compensations for coolant temperature, but that is not enough. At high RPM the ignition map is not running active on the knock sensor so you have to be careful with top end timing.

I've not extensively thermocoupled my APS FMIC as there is no issue with charge temperatures, you can get much better ignition timing and use more consistent timing.

The benefits of water injection are best combined with a FMIC, the effect on charge cooling from evaporation is beneficial, although the main effects are considered to be in the cylinder with suppression of detonation.

I consider that I "messed about" for too long and put off getting a FMIC. It makes a world of difference, but can feel odd on tiny turbos like the TD04.

[Edited by john banks - 2/22/2003 5:20:31 PM]

WREXY

George,

Geia sou my friend.


Beastie,

My car with an APS induction kit, 5 Zigen exhaust, VF23 turbo, uprated Walbro fuel pump from Mark, (Lateral performance), and an EcuTek Tek 3 map by John Banks, gave me 247.8 bhp ATW on the Delta Dash road dyno. This was with a car weight of 1350kg and with the heavy smoothing setting on the dyno. If I multiply by 1.3 which is Pat's formula it will give me 323hp at the flywheel, if I multiply by 1.22 which is John Banks's formula it gives me 302 hp at the flywheel, so probably somewhere in between would be my actual power. I'm very happy with this, but as you say once you get used to a level of power, you want more.

I would love to have more power, especially after having a 560hp V8 Ford in OZ, however I spent alot of money back then, in maintenance, including 2 engine rebuilds. With big power, it always catches up with you and you need a big healthy bank account.

In my case, I would probably go for a FMIC and if needed, another remap to accomodate the FMIC and that's it. I wouldn't want to go through rebuilds and gearboxes. The above extra mods should make my car safer in that it would take away the fear of high intake temps and would give me a few more complimentary horses.

Looking forward to meeting up again later in the year.


John,

You coming to Greece again this year?

Cheers,

Wrexy.





[Edited by WREXY - 2/23/2003 12:47:08 AM]

JIM THEO

This time you have to visit Thessaloniki George...
By the way just sold my MY00 and I am waiting for a "03 WRX, this time I'll replace only exhausts, as you said once you get used of the power you want more..and much more money.
Cheers
JIM

john banks

Hope you find it quick enough Jim! Without the turbo upgrade and remap, and with all that extra weight I suspect you will be modding it soon.

WREXY

Good one Jim.

However, I'm sure you won't be stopping at just the exhausts! As John says, the new model is heavy.

Cheers,

Wrexy.