Project STi ... the next steps
Posted: Mon Aug 13, 2007 8:48 am
I thought I would start a new project thread for the next phase of developments on the car.
Currently the car is pretty much sorted apart from a few issues that have reared their head now that it is slightly quicker (or I am) on track and in the light of a sit down and review of the current performance against others in Time Attack.
Current Issues that I am aware of:
1) Fuel Surge .... about time really, I was feeling left out from the Subaru community by not having had this to any extent - now I get it on high G right handers and is a cause for concern that needs solving. I think my smooth driving style has mitigated this for a while.
2) Body Roll .... having looked at pictures of me, I feel that a little less body roll will help the handling on the limit on track
3) Power .... more is almost always good
Solutions:
1. Fuel Surge
There are a number of solutions to this issue that plagues all Imprezas (it is in the mfr's handbook of excuses) and is down to the design of the fuel tank. The option is not there to change the tank so I am looking at ways to improve fuel pickup from within the tank by using an anti-surge tank or swirl pot. Hyperflow do a good kit for this that retails at £200 ish
2. Body Roll
Whiteline have suggested the use of 24mm adjustable ARB's to give more control and tunability of roll characteristics. These are up from the std 21 mm (i think) and will offer much greater roll resistance for track use and should compliment the Exe-TC suspension pretty well.
These will also enable me to tune the handling to each circuit / weather conditions more.
3. Power
The existing OE turbo is maxxed out now at the top end acheiving only 1.1 bar of boost at the top of the rev range because of air flow restrictions feeding enough air to the 2.5 despite now having injectors capable of more. The only option for more power now is to change the turbo.
Current thoughts are either the MD321T or FP Green turbos, which are both capable of achieving 450+ bhp and around 500 lb/ft torque on a 2.5 engine.
However, and it is a big however, I doubt whether the rest of my engine will stand this level for long with particular problem being the pistons. I have decided that it is not worth ricking a catastrophic failure of the pistons so will be looking to replace the existing cast pistons with forged 'drop-in' items when a new turbo is fitted. Prices are being obtained for this as a package now versus being a spare engine to build up to my spec.
If fitting pistons only I will be limited by the strength of other items too such as liners and rods if I really decide to stretch the power envelope to its max so torque of around 470 lb/ft would be the likely limit.
This will also highlight the limits in the clutch assembly so an Exedy Organic or equivalent will need to be done at the same time.
... this aint going to be cheap but will 'need' to be done to raise the performance bar
Currently the car is pretty much sorted apart from a few issues that have reared their head now that it is slightly quicker (or I am) on track and in the light of a sit down and review of the current performance against others in Time Attack.
Current Issues that I am aware of:
1) Fuel Surge .... about time really, I was feeling left out from the Subaru community by not having had this to any extent - now I get it on high G right handers and is a cause for concern that needs solving. I think my smooth driving style has mitigated this for a while.
2) Body Roll .... having looked at pictures of me, I feel that a little less body roll will help the handling on the limit on track
3) Power .... more is almost always good
Solutions:
1. Fuel Surge
There are a number of solutions to this issue that plagues all Imprezas (it is in the mfr's handbook of excuses) and is down to the design of the fuel tank. The option is not there to change the tank so I am looking at ways to improve fuel pickup from within the tank by using an anti-surge tank or swirl pot. Hyperflow do a good kit for this that retails at £200 ish
2. Body Roll
Whiteline have suggested the use of 24mm adjustable ARB's to give more control and tunability of roll characteristics. These are up from the std 21 mm (i think) and will offer much greater roll resistance for track use and should compliment the Exe-TC suspension pretty well.
These will also enable me to tune the handling to each circuit / weather conditions more.
3. Power
The existing OE turbo is maxxed out now at the top end acheiving only 1.1 bar of boost at the top of the rev range because of air flow restrictions feeding enough air to the 2.5 despite now having injectors capable of more. The only option for more power now is to change the turbo.
Current thoughts are either the MD321T or FP Green turbos, which are both capable of achieving 450+ bhp and around 500 lb/ft torque on a 2.5 engine.
However, and it is a big however, I doubt whether the rest of my engine will stand this level for long with particular problem being the pistons. I have decided that it is not worth ricking a catastrophic failure of the pistons so will be looking to replace the existing cast pistons with forged 'drop-in' items when a new turbo is fitted. Prices are being obtained for this as a package now versus being a spare engine to build up to my spec.
If fitting pistons only I will be limited by the strength of other items too such as liners and rods if I really decide to stretch the power envelope to its max so torque of around 470 lb/ft would be the likely limit.
This will also highlight the limits in the clutch assembly so an Exedy Organic or equivalent will need to be done at the same time.
... this aint going to be cheap but will 'need' to be done to raise the performance bar