911

So, if we made an AndyF TMIC and cut a hole/made a scoop big enough to expose the whole core to 'scoop pressure' we could be on to a good thing while the car was moving?
I think Andy had fan assist on that monster (and it was) big TMIC?

I still would suffer from heat soak waiting to leave the line in the que.

Paul:

I think I'll rig up another pair of nozzles for the cold end this week; should have added that the sprays at the hot end are aimed at the inlet side of the hot end, ie at the bottom of the core.
Lets hope my clamps hold on!

Graham

Andy.F

Correct Graham. The fans were to eliminate the heat soak issue whilst queueing for 1/4 mile etc, they were off whilst moving. Airflow from the scoop through the enlarged tmic and out to the low pressure area behind the gearbox was not in question. The engine ran a very reliable 556bhp with this.
The problem on some years of car is that there is just not enough room to get a large enough tmic fitted in.
Another important thing to consider when thinking about big bonnet scoops is that the ideal duct inlet cross sectional area is around 40-50% of the CSA of the cooling core. Any larger (such as most FMIC set ups) will just create turbulence and reduce flow through the core.

Andy

silent running

So Andy, in your opinion it's the restriction in I/C size in the top mount location that's more the problem than the air flow through the scoop? Is there any possibility that the good charge temps that you saw with your monster TMIC could have been down to just the passive 'heatsink' effect of a physically larger I/C? What was your scoop like with this monster TMIC (I've not seen it). Good point about there being a limit to how big an inlet duct you want to feed your I/C efficiently.

Paul (or anyone) - the fuel pump issue is interesting. Is it only on cars making MORE power than standard that this becomes a problem? I'm no pslewis but I can't believe that Subaru would make such a glaring oversight as to use a pump that wasn't even adequate at high speed in a European market with the high cruising speeds possible over here?

Graham - it seemed a bit gimmicky when I first noticed it a couple of years ago, but one of the US heat management firms (maybe DEI or Thermo-tec, I can't remember) makes a CO2 system that's quite interesting and would seem well suited to hill-climbing or drag racing. With the full house system, you'd have a liquid CO2 tank in the back, lines running up to the front eventually discharging through a spray bar over your I/C. But on the way, the CO2 runs through an 'aerodynamic' teardrop shaped bulb suspended within one of your boost pipes and also jackets a custom add-on fuel bar intercepting your fuel line. When you purge the system, the liquid CO2 expands through, pulling heat out of the charge air, the fuel and finally venting over the I/C and taking heat out of that too. Seems to be a clever idea for competition use, with the only downsides being the additional weight of the system and the restriction of the bulb inside the charge plumbing.

Andy.F

Yes.... in my opinion ! Whilst every intercooler will have heat sink capacity, in my case it was not considered to be a large factor. This was mainly due to the end tanks being minimum wall thickness sheet as opposed to heavy castings and the core used being of lightweight construction (tube and fin)
I used the std shape Sti5 scoop with 65mm instead of 50mm height.

Andy

silent running

I didn't realise the STi5 scoop was taller...

How do you find your reversed bonnet scoop works out? I always thought that if I was to fit a front mount, I might well go as far as to get a plain bonnet from a normally aspirated version to close off the hole.

ZEN Performance

The pump is fine at standard power levels. My point about sustained load on a pump, is that it may push a standard pump, that initially seems fine, over the edge when making unrealistic demands for fuel flow and pressure.

Paul

JTaylor

Discussed to an extent here SR. There is a smattering of bull**** though

http://bbs.scoobynet.co.uk/showthrea...=reverse+scoop

911

There must be some value in the reversed scoop/vent?
Hot air rises when stationary, so as i wait my turn to race, the turbo heat will rise out of the scoop (anyway) if it faces front or back. but when on the move, will more hot air be drawn using a reverse top scoop as opposed to a normal scoop ramming the heat down past the box etc.?
Graham

tath

It's nigh on impossible to speculate without some modelling and experiments on things like that...

However, it will make wipers unnecessary in light rain lol.

RB5_245

Having measured a bit of this myself I'll add in my results. Ait sensor is installed in the intercooler end tank.

Using APS tmic, with 20G relatively unstressed at 1.3bar circa 340bhp. Standard RB5 scoop. Ambient temp around 15 degrees. I can't remember exact figures this was about 2years ago.

Accelerating through the gears saw charge temperatures stay relatively low and fully acceptable in the 30's until hitting 4th where it would peak at around 45@7000 rpm or 130mph.

The ignition is retarded above 40deg AIT via the ecu so with the road dyno it is easy to see when this point is reached by the logs. It also runs like a dog if 40deg is exeeded at slow speeds so easy to spot.

I've found that from a standing start I get full power in 2nd and 3rd dropping off almost as soon as changing into (90mph ish) 4th, this could be explaned as heatsoak yet harsh driving on tight roads it's never been possible to get over 40deg in 2nd of 3rd, after around a min, even not on WOT in 5th the charge temp will exceed 40deg at 110mph +

From the amount I've driven the car I feel the scoop becomes ineffective over this speed it starts too loose it's effectiveness at around 100 where if sitting for any lenght of time the ignition will retard very soon after wot.

I am an avocate of fitting a larger scoop to try and cure this, which i've not done purely due to asthetics.

There is a very large lifting force on the bonnet at high speed, I had a release catch fail at an indicated 160mph and the bonnet came up with one hell of a bang!

I have looked under the bonnet before in an attempt to smoothen flow out after the radiator (imo would help intercooler flow more than undercooler ducting) aka old mini style splash guard but I don't see that it will make a significant effect for effort to make it due to the such tight space under there.

Dave

RB5_245

Oh and to add to that 5mins idling, or even parked will take the temps above 40deg, 30secs to 1 min above 30mph will drop them below again.

silent running

JTaylor - Nice one LOL I didn't think that it was possible to make a Sunny GTI-R's bonnet look worse but someone's gone and done it. Some interesting stuff on that thread though.

Graham -yes I'd agree there is SOME value in keeping the opening there - after all it does actually vent the turbo heat at standstill by convection and presumably forces a small amount of cooling air over the turbo whilst on the move. In this respect it acts almost identically to a Clio 16v/Williams bonnet vent which sits right over the exhaust manifold and is in the rear half of the bonnet just the same. I wonder what the effect of the rear facing scoop is though, over say a meshed or louvred panel? Not sure whether it would actually extract any air from the engine bay at all, being so close to the scuttle panel. Cool location for a remote fuel pressure gauge though LOL. Even if it doesn't actively extract air from the engine bay I'd expect it to cut the amount of air flow into the bonnet by a fair bit, compared to having it forward facing.

Dave - that's some good stuff there. Are you serious, the bonnet actually came up at 160? I bet you **** yourself!

RB5_245

I can tell you the car got quite unsettled under braking... not quite as unsettled as me though!

I think the best thing to do with regard to scoop reversing would be to monitor underbonnet temps with regard to charge temp. Is that added air movement, and hence turbulance advantagous for example having the scoop there may allow heat dissipation at the expense of the added turbulance reducing flow across the front mount.

I would suggest measuring at about 4 different points in the engine bay along with ait, I would surmise that the vented arrangement would only effect cooling at low speed. I would be interested to read results on this though.

I'll stop there though before speculating too much

Andy.F

There are a number of areas where you/we need to resist jumping to conclusions.

1- Bonnet lift
If there is a great lifting force then that means high air speed causing lower pressure. Lower lifting force could indicate turbulent flow. My point being that you can't read anything into the fact the bonnet wants to lift at speed.

2- High speed ignition retard.
After a period of high speed cruise, the exhaust manifold, turbo, pistons and combustion chambers are fully up to temperature and the engine dynamics are changed from the conditions during a 2nd/3rd gear acceleration run. It is normal even on the std car (new age Impreza) for the ECU to retard ignition at higher speeds due to the prolonged load applied. This can happen whether tmic or fmic is fitted.

Regards the reverse scoop, I fitted it as much to look the part as for function. I have not done any back to back testing and accept it could even have a negative effect on flow.

There are many factors that will influence the flow through the engine bay, rake of the car, splitters, ride height, bumper style etc.
On my own car I fitted a custom undertray and noticed a reduction in oil temperature ! The majority of others have reported a rise in temp.

Andy

StickyMicky

my mate claims his windscreen stays dry at the bottom, when on the move due to the reversed scoop

ZEN Performance

Does he drive in the rain though?

STI Craig

I like this thread


But I have a STI 2 with a front mount

And I think, that it isn’t to do with the intercooler as much as people on ere think
(go easy on me as i am a armature)

on my 3rd or 4th blip to 140mph I noticed the oil temp was the highest I have ever seen it at over 125 degrees C

now I have also noticed that, when I cruise at about say 100MPH + the oil temp goes high very fast.

Now when my car dropped its bottom ends in to the sump number 2 and 3 had both gone, these are the bearing which both have one oil supply where as bearing 1 and 4 have there own and they where fine so I think the very thin and hot oil went straight out the bearings and took out 2 and 3 first because they have the weakest oil supply out of all of them.

My car uses a apexi ecu which has been set to compensate for the lean mix on the cylinder that suffers from that.

Now I am using a, 15/50 oil instead of 10/40, as it is better at higher temps (look on any oil manufactures site and they will tell u that) FACT.

I have installed a lower temp thermostat to help reduce all temps, and I am now currently installing a oil cooler. I hope this will solve the problems and my car will be ok on the track again.

Fingers crossed

STI Craig

basicly what im trying to say is that, a oil cooler is very important too.

well lets face it how else can you cool the centre of your engine, a intercooler will cool the cylinder temps!!!!! but it will have a small efect on the temp of the crank and its bearings wer as a oil coller should have a grater effect,

also if you can keep the oil at its optimum temp, it should help prevent any det from damaging the bearing?

TRUE or no FAULSE u decide ?

vindaloo

I have wondered if it is possible to shield the underside of the TMIC and provide a trousers style extractor for the TMIC exhaust... Thing is I haven't a clue as to how to accomplish it. Exhaust for the air would ideally be any lower pressure area along the side/underside of the car. Side exit TMIC exhaust anyone?

IMO though...

Anything directing the TMIC exhaust is likely to obstruct 'other' underbonnet airflow in its area. It is likely that this would improve pull through the TMIC. (Likely ¬= scientifically proven).

I/C tilt and splitter seem a good starting point.

How small an anemometer can be purchased?

J.

jasonius

iTrader: (1)

Interesting..!

A few weeks ago I fitted a thermocouple into TB and did some monitoring of temps over a week or so of varied driving. Basically I found that the STI8 TMIC and scoop/splitter fitted to my WRX was keeping CT at ambient for steady driving and ~ +10deg.c for heavy turbo use (dropping back to ambient within 20 sec of steady stuff).

Now the thermocouple/gauge were semi-temporary (ie probe stays in situ coiled up in glove-box for periodic checking) so I again checked CT today, as ambient's were quite a bit higher than previous, only to find that CT were staying at ~40-50deg.c at steady driving off boost..!

Sensing something must surely be wrong I removed TMIC to check probe position (which was fine) only to find that my 20mm crank VTA hose had moved from it's original position and was running across bottom of IC. Not sure if this was the problem or not I re-routed and secured hose and refitted IC. Went out for a quick run and immediately CT's were back to there usual ambient etc as originally found..!

What this has show to me is although the STI8 TMIC is very effective for everyday fast road stuff it is very sensitive to flow impedance underneath..!

I'm sure it was flow related as the breather hose doesnt get that hot.

Amazing what you find out with a little investigation..!

silent running

This thread keeps getting better and better. Highlight has to be the 'trousers-style extractor' ROFL but I can picture it perfectly!

Seeing as this is now broadening out into a more general look at heat management, yes an oil cooler must have some kind of beneficial effect. I know my old car used to run 120-130C oil temps on long high speed runs. Fitted a remote oil cooler up front with its own stat and from then on my oil temps were rock solid 90-100C no matter what the provocation. Best £100 I ever spent I reckon. THe only time it ever hit 110 c was after three back-to-back laps of the 'Ring, funnily enough just before I came to a halt with steam pouring out of the turbo. Oops.

That thing about interrupting the flow under the I/C with a pipe in the wrong place is very interesting. I'm gonna monitor my I/C outlet temps next week and see what I can find out. I did do another set of pressure readings last night...solved the problem of going off-scale by putting a restrictor in the pressure gauge's vent pipe. Obviously these are now no longer absolute values but the give a clear progression and a correlation between pressure at the scoop and directly under the TMIC. Speed in MPH, pressure in mm of water.

SPEED / SCOOP PRESSURE / UNDER TMIC PRESSURE / DIFFERENCE

40 *********4 *********** 0.5*************** -3.5

50 **********5 ***********1 *****************-4

60 **********6 ***********3 *****************-3

70 **********9 ***********7***************** -2

80 *********13 **********12 ******************-1

90 *********16 **********18 ******************+2

100 ********xx ***********22 ******************??

Now of course these are just rough results with a pressure gauge, some hose, some masking tape and a notepad and pen. But they show and interesting pattern. As speed increases up to 80mph, the negative pressure differential, and presumably the flow INTO and THROUGH the TMIC is gradually getting less, getting closer to zero. There appears to be a 'turnover' point at between 80 and 90mph where there is no longer lower pressure under the TMIC than at the scoop and it may even be that flow actually reverses with the scoop becoming an engine bay OUTLET rather than an intake. This of course assumes no other aero effects going on around and above the bonnet which is quite an assumption to make. I recorded nothing for scoop pressure at 100, but from memory it was over 20 but by how much I couldn't say.

silent running

Sorry my table didn't work out how I wanted it to!

silent running

And I've just thought of something else. I've not even got started on how bad a design the TMIC fundamentally is, regardless of its location. Assymetrical twin entry, at 90 degrees to even the closest IC tubes. Any that aren't directly adjacent to the entry pipes are even harder for air to flow into, having to make two sharp 90 degree turns to get down the tubes. Then once the airflow by sheer luck and air pressure manages to reach the end of the tubes, apart from two or three in the middle which can blow straight out into the throttle body, they all have to take another two 90 degree turns to get out of the I/C at the exit.

I think it would be difficult to deliberately design a MORE inefficient entry and exit than this. No blended curves or bends, no internal baffling or deflectors to guide airflow correctly, a multitude of tubes leading the charge air straight into a 'brick wall', the majority of the air flow must be having to turn a sharp right angle four times between entering and exiting the I/C. It's incredible that it works at all! Imagine how good it might be if it was laid out properly.

Andy.F

What orientation was the measuring tube end to the airflow ?

ZEN Performance

But it does it's job at the power levels it's designed for, welcome to the price/performance compromise of volume production!

frayz

iTrader: (7)

Finally an informal interesting thread that i actually want to read on SN.

Well done on all this info guys, im having this very same debate with myself at the moment as to wether to put a big TMIC on my sti7 or a FMIC. Ive ordered a digital thermocouple for inside the car to read charge temps exiting the cooler. From this i think it will help make my decision on what cooler to buy.

911

I feel Paul (Zen) makes a valid point:

The Subaru TMIC whatever size, is designed for production, a 300bhp Sti or a 205 bhp UK turbo etc.
I had good results from my Sti v8 running 350/380 something bhp, and for road driving it is a great mod.
Going further and with an eye to the future (2.33/2.5 etc) I think the FMIC becomes a must (IMHO) for the resons I and others have discussed on this thread (which is very good to read comments from the proven experts).

Look at the lateral Perf FMIC and you see what Paul means, but a bit OTT for a 260 bhp tweeked UK turbo?

Got to switch-off now for work, but more comments later..
Graham

RB5_245

As you're having trouble measuring pressures, how about this... You seem to be using a water tube manometer, how about having inlet measuring scoop pressure and outlet measuring under i/c pressure and hence only measure differential pressures without having to use restrictors in the line as they completely mess up measurement unless you can accurately time how long you measure for. ie it turns into a slow reacting pressure gauge rather than and instant one and would give some sort of mean indication over a period of time. It will still reach peak pressure eventually if left for long enough.

Dave

RB5_245

oh and btw, to measure 1bar water gauge is approx 10m head... Which is a little big to use in a car , so the differential measured here is tiny

silent running

Oh yes, don't worry, I perfectly accept that the factory TMIC is a compromise design for a production road car - I'm just lamenting the fact that it is SUCH a bad design when with a bit of thought it could have been so much better. In fact it's not even that. It's more that I wonder why none of the upgraded designs, either later Subaru ones or aftermarket, seem to really depart from the same basic layout. It's all very well changing to say a bar and plate core rather than tube and fin, but when the entry and exit points and end tanks are roughly the same anyway, does it make a whole lot of difference apart from looks? Anyway it's not a big issue, just thought I'd throw it in for a bit of fun.

Dave, good guess with the water tube manometer but not quite right...I have used one in the past but it gets a bit tricky in car. It's actually a Magnehelic pressure gauge, and I thought of exactly what you suggested already - high pressure port above the IC and low pressure port below, then reading off the differential pressure directly. Problem is I can't seem to get it to read properly, and I don't know why. Whichever way round I have the pair of pipes, as soon as I get going the reading hits the zero stop and stays there. I realise the restrictor isn't ideal, I'm just using the equipment I've got, really and my readings are staying steady when I'm taking them, no 'creep' to speak of that I can see after 20 seconds or so at each speed. And yes I agree, obviously to measure a bar of pressure would need a damn great water manometer, but actually the pressures involved are a lot less than you'd expect, small fractions of a bar.

Andy, the measuring tube ends are at slightly more than right angles to the airflow, in other words, I'm trying to measure the actual 'ambient' air pressure, not the turbulent 'ram air' effect that would be seen by pointing the tube directly to face the direction of travel. This had good results on my previous car where I needed to take measurements all over the bonnet and having the open end of the tube facing slightly 'backwards' gave good, consistent, logical and repeatable results. Having it 'scooping' the air stream was impossible to get a proper reading at all.