harvey

iTrader: (48)

A TMIC does not "run out of puff" as such just the same as an inner wing filter does not become a constriction at a set bhp figure. This is a big misconception.

At some point the TMIC starts to loose efficiencey. This varies from model year to model year as Subaru recognise the short comings of the TMIC and have improved it model on model since 1993.
Generally the TMIC on 93-96 cars is already inefficient by around 280 bhp and by 300 bhp it is generally worth changing.
To simplify things, generally on STi 3,4,5 and 6, by 300 bhp there is a lack of efficiency and certainly by 320 bhp a change to an efficient FMIC is worthwhile.
On New Age WRX a change becomes worthwhile by 350 bhp and with the STi a bit beyond that and certainly by 380 bhp.
To a certain extent it will depend on how hard the turbo is working. If the turbo is operating within its efficiency envelope it makes a lot less heat than a turbo that is working on the edge.

Here is an actual example. STi3 fitted with STi8 TMIC. It had to have the bonnet scoop and under tray to operate acceptably. The car was put on the rollers at TEG Sport and made 392 bhp after tweaking the map and that was the maximum figure we could get. A Hybrid GT FMIC was fitted and the car returned for mapping. An initial run without any map tweak showed good gains and when it was repeated we had 401 bhp with any other alterations and no action on the map. The car was then mapped and we took it off the rollers having cut it back marginally for safety at 410 bhp.
So, 9 bhp straight out the box and a further 9 bhp with mapping.

The car was running noticably lower ACTs Low 20s as opposed to mid 40s on a day when the ambient was a little higher for the FMIC.

Scoobdogg

iTrader: (2)

I would recommend the HDI I recently had one fitted to my car and Harvey's advice an aftercare service offered was second to none the car is a classic running in the region of 400bhp with no problems, for the money your paying it's a high quality product both the garage an mapper of my car said you wouldn't go wrong with it and for anything else of that standard you'll be paying high dollar for pretty much the same performance.

KrisBuc

iTrader: (2)

its the front mount ill be purchasing some enough !

Shaun

Hi Harvey,
I am always sceptical about increases shown on many rolling roads, with regard to testing FMIC gains over previous TMIC figures. There is only a couple of rolling road facilitiesthat I know of (I am sure there are more), that imo are better set-up to effectively emulate decent airflow to a TMIC. Even these are not as good as the airflow you will ultimately see on the road.

In the example you give above what was the before and after ACT's with similar ambients (assuming that the ACT's for the TMIC were taken during an open run) on the road (apologies as I assume the information above was from the RR runs). Was an induction kit being used or the OE airbox? Was a snorkel attached if running an airbox?

I am not trying to pick any "holes", but just trying to better understand the playing field.

Thanks.

P.S. I did consider in asking this via PM, but I think the "detail" will be beneficial to all.

harvey

iTrader: (48)

Hi Shaun,
If I understand your question properly I have already answered it above.

These are the figures on the rolling road and the ambient temperature when the FMIC was fitted was about 3 degrees higher than when the STi 8 TMIC was tested. On both occasions the car had the same induction kit which it had run from around 340 bhp and was on the car all the time the top mount was on.
On the open road the ACT with the front mount was generally never more than 6 deg.C over ambient, when I gave it the beans it could go to 12 degrees over and on exceptional occasions as much as 15 but I don't think it ever got more than 15 C over ambient. With the STi 8 top mount it was not difficult to get to 30 C. over ambient and occasionally as much as 40 over when driven ten tenths. These figures on the top mount were greatly exceeded before I put on the STi 8 scoop and under tray.
Hope this clarifies but come back if more is required.

Shaun

Hi Harvey,
Thanks for the detail.

I always used to understand that anything under 40degs ACT was OK (ok... I appreciate the cooler the better) and anything over 40degs was going to have a detrimental effect on power. Is this correct?

harvey

iTrader: (48)

Obviously it depends on the ambient but by the time you are in the 40c area with a top mount the gains from a front mount (that is efficient) are such that it is a no brainer.

Maz

iTrader: (34)

Is there any value in FMIC on an otherwise standard car (JDM STI with exhaust and remap). I am not keen on the bonnet scoop as I feel this creates too much drag, hampering performance at the upper end and using extra fuel. Dispensing with this is my main objective. It's just a big air brake!

Midlife......

iTrader: (2)

The bonnet scoop does not add too much to drag in everyday use........in fact the main problem with the bonnet scoop is that the air is deflected over the bonnet and misses the scoop....... so scoop sits in a relatively slow moving stream of air.

Shaun

Maz

iTrader: (34)

At low speeds no. However at 100+ on a windy day the bonnet doesn't half flex! This is on a Newage BTW. I just think the car should be as slippery and aerodynamic as possible. Where's a wind tunnel when you need one?

Anders_WR1

iTrader: (8)

http://www.mira.co.uk/Facilities/Fac...ind_Tunnel.htm

If we all chip in a few quid we can hire for an hour, £500

Maz

iTrader: (34)

Hmmm I wonder if we could lure Adrian Newey away from Red Bull for an hour too and make good use of it

harvey

iTrader: (48)

As Midlife says I doubt the scoop adds greatly to drag. I toyed with removing the scoop on the STi 6 Wagon with the intention of improving terminal figures on top speed runs. I actually removed the scoop and duck taped over the gap but I could make no distinction on the actual speed achieved but under bonnet temperatures were noticably higher. I therefore put the scoop back on.
I think the scoop is designed to encourage air down the transmission tunnel and the whole way Subaru have designed the engine bay is for air to come in through the radiator and the front of the car, over the engine and down the transmission tunnel. I have also noticed that if you fit a six speed box which fills the transmission tunnel that much more you do have slightly higher under bonnet temperatures.
Einstein, as much as I want to sell you a front mount I don't think it is worth fitting one until you have an actual need. The break points as far as I can see:
Ver 1 and 2 cars with slanted intercoolers around 280 bhp.
Ver 3,4,5, and 6 cars by 320 bhp.
WRX New Age around 350 bhp.
STi New Age by 370-380 bhp.
In part it depends what turbo you are using because if you are wringing the neck of the OE turbo or a small turbo you are making more heat than would be the case for a bigger turbo working well within its capability.

Scooby Arthur

iTrader: (2)

I have changed my scoop for a reverse vent, do you think under bonnet temps are still going to be ok?

harvey

iTrader: (48)

I don't know is the straight answer however it is dead easy to find out. Go to a garden centre and look for a maximum and minimum thermometer and carry out your own tests in various locations in the engine bay. Just don't spend a lot of dosh on the thermometer as you can get good ones for around £8. I rigged up an air charge probe with the guage in the cabin when I was doing underbonnet temperature testing. One of the interesting things was that until you got to 50-55mph there was not a lot of freshair coming into the engine bay.

Scooby Arthur

iTrader: (2)

Thanks Harvey, think I will give that a try with the scoop and then reverse vent fitted.

Arch

iTrader: (59)

Would be interestin to see the results of that.