Guess the power!!

Following a fully forged rebuild, my Coupé will be off to see Leighton next week for a remap. After 6 years with forged pistons but standard rods, it's time to finally see what this turbo can do!

Previous spec
Hybrid GT28 (0.64 housing and custom compressor wheel)
82mm Wossner forged pistons
Balanced and shot-peened standard rods
Synapse Synchronic diverter valve
12v Fuel Pump Supply 'Wiring Mod'
FC Performance 3” 5 stud turbo-back, twin silencer exhaust system
A'PEXi Power intake
Pro Alloy 3” Straight Induction
Pro Alloy FMIC with FCP custom shortened pipe route
FC Performance 3D boost control system
Walbro GSS340 255l fuel pump
440cc fuel injectors
Big MAF

Mapped for mechanical sympathy (1.5bar, trailing off to 1.3bar at the redline) it made:
416bhp
328lbs/ft
Dyno charts attached for reference.

Changes - Now fully forged
82.5mm Wossner forged pistons (now 2022cc :D)
Maxspeeding rods
ARP 200 rod bolts
Seimens Deka 630cc injectors
Balance shaft removed

Nice! I'll take a guess at 480bhp

450

465

430bhp but 350-360lbs/ft on the torque. Assuming you are staying with the same turbo

440bhp

435

6bhp for the extra cc plus 50% on top for turbo... Plus a wadge more for the big injectors.

I'd estimate 475.

Glad to see you still have the Coupe Ryan. I am toying with the idea of a return one day; not sure if I'd buy standard or go down the modified road again. You must be the only other person I know who had a Synpase valve; had one on mine fitted by Rog of course.

south of 450bhp due to your injectors running out. unless pushing past 90% duty cycle

I forgot to add, it has a 3.8bar FPR.

630cc injectors must surely be good for more than 450bhp, even on the standard 3-bar FPR

I'm going for 487bhp - this is based on two factors:-

1) Your spec is now very close to mine
2) I'd be miffed if you got 489bhp.... ;-)

It will be interesting to hear your thoughts on the driveability with the big injectors - has Leighton worked out a way round the low load hunting that these give? (injectors are abruptly off or on at certain loads - they can't hold a steady light throttle).

I'd also be interested to hear how you get on with the cold start - my car doesn't like any load for the first couple of minutes after starting in cold weather (eg below say 5 degrees)

Don't tell me that now Nigel! I spent ages trying to convince Leighton it was worth going for Injector Dynamics' ID1050Xs but he insisted they were overkill!

Is it like this on all 20vTs running the 630s?

P.s Mine's going to be a fair bit lighter than yours :-)

446bhp 380ftlb

I agree that the ID1050Xs are overkill for the power you're after, but it would be interesting to know more about the spray pattern.

I have a theory (nothing more than that) that a too-wide spray pattern will cause less than perfect running at low revs / load, on the basis that some of the fuel is hitting the port walls. IIRC, the standard Coupe injector has a twin-cone spray of 10 degrees each, separated by two degrees. This pattern sprays straight down the throat of the ports, pretty much to the back of the valves.

To be fair to Leighton, getting a Coupe ECU to run at all on 630cc injectors is a triumph - back in "the early days" of Coupe modding, it was thought that 440cc was tha absolute limit. JohnS eventually baled out to a Motec ECU to get his 2.4 to run properly.

I'd really like to know what ECU options are available now

We need to know....

It didn't go so well on the day...

Leighton said he had to back off the map it had previously because the car was not responding well at all. As soon as it hit 6,000rpm, it was detecting knock and started dumping fuel.

It spooled up really well and made 360lbs/ft at only 1.5bar (previously, it made 328lb/ft at the same pressure) but promptly died off at the top end. He said he had to dial out 4 degrees of timing to remedy it and by then it was making no power. Peak power was only 384bhp. He was going to go for 1.8bar so there was scope for plenty more torque if the top end was playing ball.

Suspecting the head may have been skimmed one time too many over the years, Leighton checked the compression and found 3 cyclinders to be 162 psi (they should be 140-150 on Wossner pistons). By the time he went to check the fourth, the battery (and two power packs) were dead and we had to push start it outside his shop. The battery died on the way home while I refueled and I had to get a push start from two gents (who were washing a Calibra) in a Shell garage forecourt…

So it needs new head before it will start flowing at the top end and make proper power. I think the head I have now has been skimmed three times so it ws inevitable really...

Onwards then, it's having a 2.4 head and, hopefully, pretty soon!

Sorry to read about the head problems mate.
It will be a beast when on song.

As Joe says, sorry to read about that Ryan, especially after all the work you have put into her recently. Had a head skim been done since when it was mapped to now? Just curious as to why the problem showed up whilst being mapped?


At least I guessed right on the torque for the time being

It had the current head fitted at some point prior to 2008 when the cambelt snapped and it bent all the valves. My records are patchy from back then but presumably it was skimmed.

It melted a piston in 2009 so the head may have been skimmed again then.

It was definitely skimmed this time around.

I can only assume this was one skim too many?



It made that torque at 1.5bar though, if it'd been mapped at 1.8bar, you'd have been wrong

Can you not fit a thicker head gasket? https://www.protoxide.eu/en/head-ga...arate-rings-fiat-coupe-20-20v-turbo.html

It used to be the solution years ago, I don't know if it is now frowned upon...

instead of thicker gasket, machine slightly deeper bowl in pistons... who build that engibe could check the CR and squish band and could prevent this situation🤔

Well over a year on and the Coupé finally went back in for mapping last week.

The following modifications were made since the previous mapping session, where it experienced serious detonation
NGK 8 spark plugs
Ported and polished 2.4 Stilo head (with Nimonic exhaust valves)
Ported and matched exhaust manifold
Aquamist HFS3, dual port water/meth system

Headline figures:
448 bhp @ 7,274rpm
370 lbs/ft @ 5,543rpm

Leighton said it was far happier than it was previously, and that he was able to push the turbo until it was maxed out - where it will stay!!

Interestingly, the power loss to the wheels seems to have decreased from around 50 to 40 since the last time it was mapped. I have to wonder if this could be attributed to the Quaife?

Good result Ryan - I bet it feels epic on the road. Drivetrain losses could be down to may things - tyres, temperatures, the Quaife or simply just a different assumed value entered by the dyno operator.

What do I win?

I think I was equally close

7bhp out

Glad it’s all sorted now, that was quite an ordeal!

Enjoy

The re-build opportunity in a few years time :-)

Let's hope not