JustCallMeMac

I have a Hawkeye Type UK STI (2.5) which has been sensibly modified and re-mapped, by Bob Rawle, to produce 390 / 410. The car has only covered 8000 miles.

It’s currently at Chevron Motorsport in Stafford having the handling and brakes sorted, (Tein monoflex coilovers, whiteline arbs, alk, full geo set up, AP 6 pots (front)), as I intend to get some tuition and start tracking the car next year, as well as heading over to the NBR. Nothing competitive to start with, just learning about and enjoying the car’s capabilities, which can’t be experienced on the road.

I keep reading about the ‘chocolate pistons’ on the UK spec model but having spoken to Simon at Chevron, he says a lot of this is down to the map and that if carried out properly, as Bob would have done, there shouldn’t be any problems.

I suppose if I’m going to work the car hard, I don’t want to be worrying about breaking the engine so it would be good to know what would need to be invested now in order to avoid a potentially more expensive issue later on. I’m not really interested in increasing the power, as the car has plenty enough for me, although I might like to make the magical 400bhp one day, just for the hell of it. In terms of tracktime, who knows but between 6 and 12 times a year.

Is it simply a case of upgrading the UK spec 2.5 engine to forged pistons and maybe conrods, or is there more to it than that?

Or is it a case of waiting for things to go bang first, (if they do) and then going for a proper rebuild from the likes of API?

Or am I worrying for nothing?

Apologies for my naivety, I’m no mechanic, but opinions, advice and potential ballpark costs, for each scenario, would be welcome.

Funds are limited but this car and having fun on the track to get the most out of it, is going to be my hobby as I just sail north of 40, so I’d rather spend a little more over the coming winter, whilst the car isn’t going to be used, if it’s worthwhile doing so and for my own peace of mind.

Cheers,

Steve

Shaun

You are better off speaking to professionals that build / map these engines and have customers who use them on track. You will get so much conflicting advice on here I suspect.

Driving to the shops is in a totally different part of the world than giving it some serious use on track.

If you are serious about track use, you would be best advised to ensure everything is at an appropriate level before you unleash the car, or you will pay dearly for it.

Terminator X

iTrader: (7)

If you go forged you need to take the engine apart so at least £2-3k before you start ... wait until it goes bang IMHO, which it may never do of course.

TX.

APIDavid

iTrader: (4)

[QUOTE=Terminator X;9592921]If you go forged you need to take the engine apart so at least £2-3k before you start ... wait until it goes bang IMHO, which it may never do of course.

TX.

Aaaah BUT !, if it goes bang, it'll wreck the bores and 2.5 cannot be bored oversize, if you want to keep oil in the sump.

The problem is that the bore walls are very thin on 2.5's and they barely stay together on a standard block at high horsepower, let alone after a rebore.

SO, just now a set of forged pistons new rings head studs and so on will be plenty good enough for 430 - 450 hp. More than that and even a standard bore block will sooner or later split a liner.

Wreck the standard pistons and it'll need a new block and the cost suddenly goes through the roof.

OP call me if you want to talk it through.

David APi

01926 614333

smokingkills

iTrader: (3)

390 / 410 and my 2.5 pistons gave up one of the ringlands, fortuantely this was caught before serious engine failure occured & now full forged engine built. IMO you are close to the inevitable happening with those figures. I wouldn't want to run anything over 350ish with those crappy pistons.

53

iTrader: (41)

...and to get those figures you must be running impressive boost and those VF43's like to crack Personally, I think your power is probably over estimated which is good IMHO, however HG's are more the issue with 2.5's so keep you eye on temperatures and look at maximising your cooling if seriously doing track time.

If it were me I would get it properly track/road dyno'd to find out exactly what is going on boost/power/temps etc...if everything looks good just enjoy it !

There is a lot to be said for pre planning, but also similar can be said for 'if it aint broke'....

trevsjwood

iTrader: (2)

Mac, what are the main upgrades you've done thus far and is your power data from a Rolling Road ?
Trev

Tone Loc

iTrader: (1)

David, what are the very rough costs for fitting new pistons inc studs etc and anything else required (standard rods etc to remain)? In my case i'm thinking of a hatch Sti but presume costs are similar.

Cheers,

Tony.

Midlife......

iTrader: (2)

If you have the money I'd think along David's lines..... Standard STi rods should be good enough and Mahle Powerpack pistons or similar

Shaun

APIDavid

iTrader: (4)

Mahle power pack?, go wash your mouth out ......

We use Supertech from the US. really strong, perfectly round [ you listening Mr Wiseco ? ] and silent when bored and fitted correctly. I'm really sold on them and even the great Oliver Clark was impressed when he heard them...or rather didn't hear them.

We have found in the past that boost of 1.3 bar and upwards kills the standard pistons below that they hang on , but 1.25 bar is for wimps [ or chocolate pistons !! ]

David

JustCallMeMac

Thanks David. Coming from you that's great advice. I will give you a call

I think it is over-estimated too, based on what I've read is realistically possible based on the mods the car has and the VF43 and despite the dyno print-out showing those numbers. Boost, if I recall, is 1.1 bar and the torque curve means she pulls like a train. Whatever she's running, Bob mapped the car brilliantly. For info I'm also having some Defis fitted by Chevron, (boost, oil pressure, oil temp) so that I'm more aware of what's going on.

I think you've hit the nail on the head re. the pre-planning. After reading David's recommendation I think it would be wise to consider it strongly. I've saved long and hard to buy the Hawkeye as a second car to enjoy on the track and also to modify it, primarily for handling, so to spend a little more, in order to avoid a potentially very expensive bang, would make sense. I'd rather do it right and put off my 'track debut' than rush ahead and regret not doing it!

I bought the car with the upgrades and map already done and I also spoke to Bob Rawle before I bought it to confirm his own work. It is fully de-catted, has Cosworth induction, walboro 255 fuel pump, NGK7 plugs and upgraded wastegate actuator, to handle the higher boost. As 53WRX said, the 390 / 410 is probably over-estimated and whilst I have a rolling-road dyno readout with the figures in question, it's unusual for the VF43 turbo to really get above 360bhp / 370bhp although I have heard rumours of some 2.5s getting to the 390 level. However, for me, it's the torque that's really impressive and that's way above standard, whatever it is.

dunx

iTrader: (3)

Forged bottom end and fit a thermostatically controlled oil cooler.

dunx

trevsjwood

iTrader: (2)

I would be guided by Bob on wether or not to open up the engine, but from what you have said Chevron seem to be on the money. I would add a water temp gauge, before the others to be honest and deffo FMIC for track. Too hot an engine wont take a blind bit of notice of forged pistons.
good luck
Trev

JustCallMeMac

Sorry but what does HG stand for? Something obvious I expect so I shall await the ridicule!!

Cheers,

Steve

APIDavid

iTrader: (4)

Head gaskets

Head studs fix the stretchy-bolt-blown-head-gasket syndrome, which whilst rare, can happen.

David

Ask away, no matter what, we all knew nothing when we started, some out there in the world still know nothing.........

alcazar

iTrader: (2)

LOL at that..........but I'm not disputing it

dunx

iTrader: (3)

I know nothing, but I'm entitled to my opinion even if it's wrong !

LOL

dunx

alcazar

iTrader: (2)

And being a Yorkshireman..............

dunx

iTrader: (3)

Yellerbelly...

See you on the 5th ?

dunx

Terminator X

iTrader: (7)

At what level does boost become "impressive"

TX.

APIDavid

iTrader: (4)

I work on the following;

If you know nothing, don't speak and people will never know.

As soon as you speak you remove all doubt.

JustCallMeMac

Good to speak to you earlier David and thanks for taking the time to go through things!

You have certainly removed my willpower to keep my wallet shut!!

Have just dropped you a quick email.

Cheers again,

Steve

alcazar

iTrader: (2)

By all means.

trevsjwood

iTrader: (2)

I see Supertech make a 100mm piston for the EJ257, obviously they don't see overboring as the same problem you do.
Trev

53

iTrader: (41)

Enough to crack your VF43 1.1 need not apply

APIDavid

iTrader: (4)

Trev, they are for use with Darton sleeves which are about the only known [ to me anyway ] way to overbore a 2.5 safely

The 2.5 total liner thickness, steel and alloy is about 3.5 or 4 mm max at the critical point.

At higher boost the standard liners 'pant ' and act like a small pump allowing oil up past the rings.

Overbore a standard 2.5 block at your peril and risk.

David

trevsjwood

iTrader: (2)

well for my sins, my bores are at 100mm,recently a piston failure resulted in scoring of No 4 cylinder. The cylinder was honed out by 1.5 thou" which cleaned the bore up. A set of Mahle 100mm forged compact pistons which come out of the box 1thou" bigger than any other 100mm item were sourced and honed matched to run at 3thou" clearance. Whilst the fix isn't ideal it is still a good build.
Once the car is run in it will be mapped to run approx 1.6 bar.
The car has oil catch cans and the only time they have caught any oil is when the piston let go, so 'cylinder panting' doesn't appear to be a problem and neither also the boost, which as with most 2.5 drops off quickly above 5500rpm, so you don't have high boost at high rpm as in the 2ltr builds.
Trev

APIDavid

iTrader: (4)

Ah!, Ok; you clearly know better than we do Trevor.

stevie1982

iTrader: (16)

The words bum fight spring to mind, to the op there a plenty of well respected engine builders on here and then there are some well respected members who have built thier own engine, to find one common ground of what can be done is a needle in a hay stack.

IMO you will not go wrong with David @ API and his team, which ever route you go down or advice you take I wish you all the best and hope you enjoy the end result.

JustCallMeMac

So far I have to agree 100% with you mate and thanks for your good wishes. I'm looking to get some driver tuition and then start tracking the car from next Spring and so I'm having what I think are sensible mods and improvements done now and over the next few months to get the car sorted. It's going to be a long Autumn and Winter but I can't wait.

Have spoken to David at length about my requirements and being a bit of a mechanical ********, (me not David ), he's explained and summarised everything in detail and in plain English, without ever trying to blind me with science. He broke everything down sensibly and gave me a few other options to consider, without ever being insistant and taking advantage of my lack of knowledge. Top bloke and he will be getting my business when I'm ready to drop the car to him!

To be honest I have only ever gone on the personal recommendation of the majority of guys on here so I'm sure my car will be in safe hands and even if there is an issue afterwards.

For example the car is currently with Chevron Motorsport in Stafford having handling, chasis and front-brake upgrades, after Simon was recommended to me, in glowing terms, by quite a few members on here. I live in Southampton so it's a fair old trek but after speaking to Simon, on quite a few occasion, I had no problem asking him to do the work. His approach was very similar to Davids.

Can't wait to get the car back but have this feeling that I'll now be stopping off at API on my way back down South and subsequently getting a train home!!

Cheers,

Steve