Project STi ... the next steps

[dynamix]

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

[Houdini]

Good read, Duncan. I'd be particularly interested to see how you get on with the fuel surge issue

470 lb/ft also sounds about right too. I'm aware of the bottom end on the 2.5 engine starting to move around once you reach 500 lb/ft. Beyond that comes scary territory with a fully forged engine being the next stop

[danr55]

I'd also be interested to how you get on with the fuel surge issue

[dynamix]

Solution has been chosen:



[quote]HyperFlow Technologies has completed development of a fuel surge tank to suit the MY01-05 WRX and WRX STi fuel pump assembly.

It is recognised that fuel surge does occur with light fuel loads in the Subaru WRX, leading to starvation. This shortens range on the track and adds mass to the vehicle, with unnecessarily high fuel loads for Super Sprints and track racing.

The Fuel surge tank has been developed over many months to ensure the materials and configuration are durable and perform.

A custom thermoplastic base has been created from fuel resistant materials. The base interfaces with a CNC machined billet alloy top plate that is fixed to the fuel pump frame

As shown in the images above, the base of the surge tank fits precisely to maximise use of fuel in the tank. The baffle system has been successfully tested on an STi at Wakefield Park clocking consistent 1.09 sec lap times with light fuel loads

[SPIKE LIKE MIKE]

Did you know you can now also get a twin walbro pump - fuels uptp 700bhp on original fuel lines - they are basically 2 fitted side by side. I assume this will also help with fuel surge? approx

[Chris B]

That Hyperflow pump looks very interesting,it is very very similar to the STI pump fitted to the Spec Cs like Kevs,what is the cost?

[Robocop]

Spike

You'll still suffer from fuel surge even with two pump. Unless of course the fuel pipes themselves are attached to opposite sides of the fuel tank.

[Micktype WR1]

You may have heard of Nathan Freake (friend of mine) He's a member of WJPC and has built a very fast MR2 for his "Ten Of the Best" entry. He won his catagory. He's Form Ford Champ from 06 too.
The point is that he had the same concerns about fuel and solved it with a swirl pot...
http://www.wjpc.nemesisuk.com/forums/in ... =575&st=60

Scroll down past the enormous turbo pics and you'll see the pic of the swirl pot. Hopefully you'll get the manufacturers name from the pic !

Hope it might be of some interest to you.

[dynamix]

A swirl pot is 'a, and probably THE, solution' but this will mean having this 'pot' mounted in your boot. The std pump then feeds this with any excess being returned to the tank and generally another pump is needed to bring the fuel to the engine.

The other issue with this is that the swirl pot is then encroaching on boot area and becomes quite vulnerable to objects flying around in there and may (i havent totally checked) would also require fitment of a fireproof bulkhead between the boot and the passenger compartment for the likes of Time Attack.

The swirl pot is more expensive set up.

The Hyperflow kit is about

[Houdini]

I'm liking the hyperflow kit solution a lot

Where exactly is this mounted, Duncan? The car needs to remain a family drive so extraneous fuel bits are probably not ideal for little fingers to play with if they're foreward of the rear seat bulkhead

[dynamix]

Indeed - it is mounted within the fuel tank and acts like a baffled mini-reservoir within the main tank. It seems to solve the problem well enough from what I have heard.

[dynamix]

I think I have had a result on this Anit - Surge tank ... I will keep stum until it actually arrives but suffice to say I think I got a good deal

[marky mark]

Great thread Duncan.

Have you spoke to RCM about the in tank STI surge pot that STI make for aftermarket fittment. Nice bit of kit but a bit expensive.

[dynamix]

Nope - hadnt spoken to RCM. I have ordered the Hyperflow kit and will atempt to fit it myself

[dynamix]

Hyperflow kit has arrived, or should I say MRT Rally kit has arrived. Looks pretty straightforward to fit (famous last words I know) so will get it fitted this weekend if time allows.

Dimensions are 120mm x 65 mm x 95mm

Therefore volume is 741 cc. (approximately )

This should hold enough fuel to solve the issue.

It is essentially a rubber surround for the fuel pickup with the hole for the fuel to enter towards the front of the car so hard acceleration or cornering will not drain it.

btw RRP cost of this is

[WR1 Bro]

Make sure you take pictures of your progress Duncan.

[dynamix]

I will have my camera and phone at the ready to call an expert 'when' I get stuck in the boot upside-down covered in petrol and nearly passing out from the fumes

[WR1 Bro]

Maybe a camera/phone and fumes aren't the best combination?

[dynamix]

Good point....

I will have a collection of yoghurt Pots and very long pieces of string at the ready to call an expert 'when' I get stuck in the boot upside-down covered in petrol and nearly passing out from the fumes :pmsl:

[Houdini]

Good point....

I will have a collection of yoghurt Pots and very long pieces of string at the ready to call an expert 'when' I get stuck in the boot upside-down covered in petrol and nearly passing out from the fumes :pmsl:

FPMSL, Duncan I have an endearing image of you struggling to choose Yoplait or Activia in your moment of need, only to find the other end of the string reaches another yoghurt pot already in the boot alongside you.

Get some piccies up as soon as you get a chance

[dynamix]

I will hopefully get this fitted today as I am off down to North Weald tomorrow to watch my friend drifting in EDC at the DonnySouth show.

[Gee Wr1]

Did the fuel surge bother you on Knockhill? Think we've all had it there especially coming out of the hairpin where the car really gets loaded up on the nearside with the camber & rise in the track exiting the corner, also sometimes happens at Carlube before the back straight.

I was watching you at the TA at Knockhill you looked good on track
Did take some video footage but not had a chance to view it yet but i'm sure i got you sliding the back end out of the hairpin a few times

[dynamix]

In an effort to solve fuel surge issues to remove one of the standard Subaru excuses, I set about to solve this issue with the help of the Fuel Surge Kit from Hyperflow / MRT Rally.



Despite doubts by others as to whether I could actually install this myself (having seen my oil changing prowess first hand ) I thought I would give it a go ... after all, how hard could it be

First job was to remove the rears seats - this makes access to the pump alot easier than hanging upside down in the boot.





Next was to remove the access cover and expose the pump top and connections.



This was all too easy apart from the main fuel pipe that had decided that it didnt want to move Anyway, a bit of wiggling, jiggling and general fiddling later it was off and time to get the pump assembly out - this was tricky as you have to twist it gently and take care with the float assembly.





Once out it was time to fit the new box around the pick up and drill two holes for the bracket to hold it. Once I had found an appropriately sharp drill bit this was re-assembled and time to install back in the car.





This was harder than the extraction as there was a box on the end but eventually in it went and time to connect all the hoses and put the back seats in.

Question is ... had I broken anything?



nope - fired up first time and kept on running

I might make a mechanic yet

[dynamix]

Did the fuel surge bother you on Knockhill? Think we've all had it there especially coming out of the hairpin where the car really gets loaded up on the nearside with the camber & rise in the track exiting the corner, also sometimes happens at Carlube before the back straight.

I was watching you at the TA at Knockhill you looked good on track
Did take some video footage but not had a chance to view it yet but i'm sure i got you sliding the back end out of the hairpin a few times

Yep - got fuel surge most of the time at the hairpin when I let it run under half a tank. In the end I had to fill it over half way to get rid of it. Didnt happen at Carlube though as the car seemed as if it was flying there

Video would be awesome if you have it

[danr55]

really keen to hear if this sorts out your issue. I'm getting a bit fed up of fuel surge now

will the knockill be televised at some point soon, didnt someone say 3 weeks after the event broadcast on a friday on motors tv?

[dynamix]

The EDC drifting from Knockhill was on Motors TV last night (and again over the weekend) - so it should be TA next friday night on Motors TV (413).

I hope it solves the issue too

[dynamix]

Water Temp ==================

Following on from the thermostat issues at the nurburgring and the make shift repair of the jammed thermostat over there, a decision had to be made to replace it. Normal running on the road barely got the water temp up to 70C let alone 80+.

So... a zerosports cool therm was order from Lateral Performance and fitted by me, taking the opportunity to put some anti freeze in a system running pure water since the drain at the ring.

The zero sports stat opens at about 77C as opposed to 85 for the std stat so will run cooler and didnt cost much more than the standard part.

Fitting was straightforward and I gave it a good run afterwards to spot for leaks - there was none I must be getting better at this mechanic stuff.

Water temps on the road now are over 80C but about 7C less than before.

Oil Temps have also dropped from around 90C in normal running to around 84 due to the cooling effect of the water.... so an added benefit.

Suspension ====================

I also took the opportunity to adjust the rear whiteline anti-roll bar from the current soft setting, which was a little stiffer than std but not much. This, i felt, was causing the car to understeer more than it used to so I needed to address the balance. Popping it into the middle possition was not a hard job but was definitely fiddy as it had to be done with the wheels on the ground and not being in possession of a ramp it meant an uncomfortable time under the car undoing the bolts.

End result is good though with the steering now much more immediate even with the coilovers on softest settings all round and a definite improvement on slow speed corners as well as quicker ones. Having thought for some time that less roll at the rear would help, this was quite pleasing to say the least.

Next Steps =====================

Rear camber needs sorting out to add more than the 1 degree that I have at present. I am aiming to 2 degrees of negative camber at the rear and will try the camber bolt route first in an effort to get this. If this does not do the job then some adjustable lower control arms may be called for

[dynamix]

New wheels fitted along with winter track tyres (ie RE070 but date stamped 09/07 so pretty sticky) - these should cope with wet track days and the inevitable mix of conditions on an autumn ring trip.

Photos of the wheels will be taken tomorrow after I clean it ... you may recognise them

i thought it was about time to put in replacement front brake pads too.

The old Performance friction .11 pads (aka z rated) have finally managed 22,000 miles including countless track days, ring trips and a few other bits. They still had 3mm of pad left and will do nicely as a spare set in case of emergency.

[danr55]

New wheels fitted along with winter track tyres (ie RE070 but date stamped 09/07 so pretty sticky) - these should cope with wet track days and the inevitable mix of conditions on an autumn ring trip.

Photos of the wheels will be taken tomorrow after I clean it ... you may recognise them

i thought it was about time to put in replacement front brake pads too.

The old Performance friction .11 pads (aka z rated) have finally managed 22,000 miles including countless track days, ring trips and a few other bits. They still had 3mm of pad left and will do nicely as a spare set in case of emergency.

look forward to the pics

[dynamix]

Cleaned and ready to go: