WRX with STI TMIC - need the scoop too?
10 July 2013, 06:02 PM
#1
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WRX with STI TMIC - need the scoop too?
Hi Guys,
I have a 2003 WRX and I'm thinking about upgrading the TMIC to an STI version.
I know I have to change the undertray, but would it all be pointless if I didn't change the scoop to an STI scoop too? Or would I still see good benefits with an STI TMIC, undertray and WRX scoop?
Would love to hear what you think or experience has been!
Cheers
I have a 2003 WRX and I'm thinking about upgrading the TMIC to an STI version.
I know I have to change the undertray, but would it all be pointless if I didn't change the scoop to an STI scoop too? Or would I still see good benefits with an STI TMIC, undertray and WRX scoop?
Would love to hear what you think or experience has been!
Cheers
10 July 2013, 07:35 PM
#2
usually the scoop and undertray are sold together, so best case to fit both, the benifit is the sti scoop is higher and for that I would expect it to be more effective at high speed.
To fit the undertray only would still have good benifit. To do nothing and just fit the intercooler would still be effective. The intercooler as well as having a larger surface area is much deeper and is known to be effective up to 400hp, so running up to as much as 340/350hp it's still going to be effective even with a slightly reduced airflow.
I ran a similar size aftermarket intercooler with my wrx scoop and undertray and there were never any issues, I just fitted the STI scoop and undertray later on.
Trev
To fit the undertray only would still have good benifit. To do nothing and just fit the intercooler would still be effective. The intercooler as well as having a larger surface area is much deeper and is known to be effective up to 400hp, so running up to as much as 340/350hp it's still going to be effective even with a slightly reduced airflow.
I ran a similar size aftermarket intercooler with my wrx scoop and undertray and there were never any issues, I just fitted the STI scoop and undertray later on.
Trev
10 July 2013, 07:48 PM
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Hi Trev, exactly what I thought, but just wanted to have it backed up from a member in the know.
Out of curiosity, what aftermarket top mount did you have? How much power was you running through it?
Out of curiosity, what aftermarket top mount did you have? How much power was you running through it?
10 July 2013, 07:52 PM
#4
The sti undertray can be modded to fit the wrx scoop, that's what I did as I wasn't keen on the big scoop.
Or the other option would be to mod/extend the rubber on the wrx undertray.
Either way it's your choice in what you prefer.
Or the other option would be to mod/extend the rubber on the wrx undertray.
Either way it's your choice in what you prefer.
Last edited by bustaMOVEs; 10 July 2013 at 07:54 PM.
10 July 2013, 08:10 PM
#5
The STI top mount is a proven bit of kit and is first choice for upgrading the wrx.
Trev
10 July 2013, 08:55 PM
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The problem with the sti top mount, is finding a good one at a good price. The avo and hyperflow ones seem to have good reputations but are expenzive! I was trying to figure out if some if the aftermarket top mounts that are selling for roughtly the same price as used sti versions aee any good. They dont seem to be, so I'll have to keep looki g until I find a good one, one shiukd come up sooner or later :-)
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11 July 2013, 02:37 PM
#11
The problem with the sti top mount, is finding a good one at a good price. The avo and hyperflow ones seem to have good reputations but are expenzive! I was trying to figure out if some if the aftermarket top mounts that are selling for roughtly the same price as used sti versions aee any good. They dont seem to be, so I'll have to keep looki g until I find a good one, one shiukd come up sooner or later :-)
Trev
12 July 2013, 03:56 PM
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You definately need to do both otherwise you'll not get full benefit. LArger scoop standard tray means more air flow but just to certain areas of the IC, not great. LArger scoop and aftermarket tray to match means more air to all the IC, perfect. Watch out for heat soak as you'll still get it when standing in traffic no matter what size IC you have, only FMICs sort that.
01 November 2020, 12:42 PM
#15
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It was my understanding that Sti needed the bigger scoop especially at lower speeds on the higher powered production road car ( Post Japanese Producers 280bhp agreement )
to prevent charge temperature increase causing knock. The introduction of the IHI 34 Turbo >2001 having exasperated the situation together with US Emission Laws.
So why do we not use the Large scoop on Rally Cars? . The WRC cars had to produce still greater power, and especially in higher temperature regions you needed a bigger / better cooled IC . This could only be solved with FMIC and additional bonnet vents to remove the IC/ Radiator hot air before it flowed over the engine. Engine and Turbo cooling was actually assisted by the Bug / Newage Scoop. The larger the scoop however the worse the drag is and is detrimental for smooth airflow over the car. For this reason the Sti large scoop was not ( as far as my research goes ) used in the WRC. Rally avg speeds are typical 110 kmph . some are even higher. Unless the drivers were roasting in the cockpit while the drag was worth a Tenth of a second / km even the small roof vents had to be dropped down.
On track cars the drag is even higher still and due to the higher average and higher maximum speeds the larger the scoop the higher the positive lift pressure becomes due to turbulence generated over the screen / roof. But a FMIC may not be needed for sub 400 bhp as sufficient Airflow is available from a WRX / Newage scoop,
For example when driving on the Ring , in light traffic a good Road Subaru / Pilot will average 130kmph , (about 8 1/5 mins bridge to gantry ) with many tuned Subarus exceeding straight line 225 kmh so on the Track large scoop size becomes a Drag liabilty. Take a look at www.wrcwings.tech , this link helped me against my fading memory.
However if you want to drive around Town at legal max and protect your circa 400 , 400 + bhp build then a FMIC is the only way. Just hook up a temperature sensor on your TMIC and you soon see that charge temp increases quickly <30 mph , if you want some help use the IC water cooling.
to prevent charge temperature increase causing knock. The introduction of the IHI 34 Turbo >2001 having exasperated the situation together with US Emission Laws.
So why do we not use the Large scoop on Rally Cars? . The WRC cars had to produce still greater power, and especially in higher temperature regions you needed a bigger / better cooled IC . This could only be solved with FMIC and additional bonnet vents to remove the IC/ Radiator hot air before it flowed over the engine. Engine and Turbo cooling was actually assisted by the Bug / Newage Scoop. The larger the scoop however the worse the drag is and is detrimental for smooth airflow over the car. For this reason the Sti large scoop was not ( as far as my research goes ) used in the WRC. Rally avg speeds are typical 110 kmph . some are even higher. Unless the drivers were roasting in the cockpit while the drag was worth a Tenth of a second / km even the small roof vents had to be dropped down.
On track cars the drag is even higher still and due to the higher average and higher maximum speeds the larger the scoop the higher the positive lift pressure becomes due to turbulence generated over the screen / roof. But a FMIC may not be needed for sub 400 bhp as sufficient Airflow is available from a WRX / Newage scoop,
For example when driving on the Ring , in light traffic a good Road Subaru / Pilot will average 130kmph , (about 8 1/5 mins bridge to gantry ) with many tuned Subarus exceeding straight line 225 kmh so on the Track large scoop size becomes a Drag liabilty. Take a look at www.wrcwings.tech , this link helped me against my fading memory.
However if you want to drive around Town at legal max and protect your circa 400 , 400 + bhp build then a FMIC is the only way. Just hook up a temperature sensor on your TMIC and you soon see that charge temp increases quickly <30 mph , if you want some help use the IC water cooling.
Last edited by Linksfahrer; 01 November 2020 at 01:14 PM. Reason: Had to laugh as I had overlooked the age of the ORG thread :-)
01 November 2020, 02:01 PM
#16
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Is there much of a marginal benefit to swapping the TMIC on a newage WRX? Andy Forrest told me that a newage WRX TMIC is similarly sized to that of a late classic STi (which are capable of 320-330bhp) and thus he did not see it as a worthwhile modification for the effort involved. Has anyone found the newage WRX TMIC to be a limiting factor when running say a VF35-sized turbo and STi injectors? Would be interested to hear.
01 November 2020, 11:27 PM
#17
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Is there much of a marginal benefit to swapping the TMIC on a newage WRX? Andy Forrest told me that a newage WRX TMIC is similarly sized to that of a late classic STi (which are capable of 320-330bhp) and thus he did not see it as a worthwhile modification for the effort involved. Has anyone found the newage WRX TMIC to be a limiting factor when running say a VF35-sized turbo and STi injectors? Would be interested to hear.
Im not quiet finished , the last item I wish to change is the header which are still standard , I would look to find another 10-15 Bhp , the extra flow would require a remap and will bring the 565cc injectors closer to 90 % duty cycle ( currently 82%) If you ask Andy Forest he is bound to say this level requires the switch to a Sti IC , you might still "manage" road tuning on the WRX IC but getting enough power runs done on the RR before the IC temp rise, start to hold your timing back success will depend on the blowers flow in the box and the ambient and mappers temperature , The point about using the larger Sti IC is that you dont want the IC to become the limiting factor , if you have already spent 4-5 thou on the previous mods / engine.
02 November 2020, 07:28 AM
#18
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Its fair comment from Andy at 320 bhp but I have heard from Duncan while on Surrey RR that he thought my WRX cooler was starting to suffer heat soak , we had already done 5 power runs , but at that time I was running a TD05 16G 565cc injectors but just the PPP downpipe / exhaust, As he pushed it again it started to make less power. At 314bhp on 102 Octane I was not particularly happy. When that engine let go six months later I decided to go to a forged 2.0 with a SC36 Turbo and a 3 inch Sports Cat , the tune was later done at Plymouth Engine tune , here we hit a problem with the Tumbler motor which was partial closing , so I had them taken out , and while talking with Martyn he thought that with a SC36 it would be the right time to add the Sti IC , the result on 95Oct ( 102 Octane is not available in UK) was a conservative 329 bhp and a much more solid broader torque delivery.
Im not quiet finished , the last item I wish to change is the header which are still standard , I would look to find another 10-15 Bhp , the extra flow would require a remap and will bring the 565cc injectors closer to 90 % duty cycle ( currently 82%) If you ask Andy Forest he is bound to say this level requires the switch to a Sti IC , you might still "manage" road tuning on the WRX IC but getting enough power runs done on the RR before the IC temp rise, start to hold your timing back success will depend on the blowers flow in the box and the ambient and mappers temperature , The point about using the larger Sti IC is that you dont want the IC to become the limiting factor , if you have already spent 4-5 thou on the previous mods / engine.
Im not quiet finished , the last item I wish to change is the header which are still standard , I would look to find another 10-15 Bhp , the extra flow would require a remap and will bring the 565cc injectors closer to 90 % duty cycle ( currently 82%) If you ask Andy Forest he is bound to say this level requires the switch to a Sti IC , you might still "manage" road tuning on the WRX IC but getting enough power runs done on the RR before the IC temp rise, start to hold your timing back success will depend on the blowers flow in the box and the ambient and mappers temperature , The point about using the larger Sti IC is that you dont want the IC to become the limiting factor , if you have already spent 4-5 thou on the previous mods / engine.
02 November 2020, 10:15 AM
#19
Also given the cost I would also always opt to upgrade the IC too (definitely once past standard td04 territory). You could probably do this for about 200-250 all in, and the STI TMIC is a really good piece of kit with the right undertray (IMO), at least for reasonable power levels
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