JAR1Y back on the road after a few years

[tuscanturner]

Not what I was expecting but it certainly runs sweeter

[ukkid35]

The incredible thing for me is that when I overlay my chart on yours it follows virtually every little bump on both torque and power. Same engine/induction/dyno probably contributes significantly to that.

[tuscanturner]

Although it drives a lot better than before I was still expecting over 420hp with the amount of work andthat has been done to her not to mention the money.
Now just need a bit of dry weather to get out and do some miles. she has some catching up to do with only 16,000 miles on her from new.

[ukkid35]

Your engine is better than mine all the way to 6000, and then mine keeps going, which suggests to me that you may have a breathing restriction somewhere. Do you have cats, if so are they new? Fresh air filter? I had Cats and Sports Tails at the time, which I hate. Fortunately Joolz reckons the SP Backbox that I now have (coupled with Linked Decats) won't cost me anything. I thinking of going back to Joolz for another session since the heads have been off and skimmed again since then.

[Jhonno]

ukkid35 said:

Your engine is better than mine all the way to 6000, and then mine keeps going, which suggests to me that you may have a breathing restriction somewhere. Do you have cats, if so are they new? Fresh air filter? I had Cats and Sports Tails at the time, which I hate. Fortunately Joolz reckons the SP Backbox that I now have (coupled with Linked Decats) won't cost me anything. I thinking of going back to Joolz for another session since the heads have been off and skimmed again since then.

Iirc it is a 4.5 with a 4.2 top end? So that will be the restriction?

[tuscanturner]

I have the ACT 4.5 big bore system on with no cats. Plus the fancy manifolds and a huge list of other stuff

[tuscanturner]

[gacksen]

dont overjudge the dyno charts. different dyno different number ....

[Jhonno]

tuscanturner said:

That manifold!

[ukkid35]

gacksen said:

dont overjudge the dyno charts. different dyno different number ....

Same Dyno, Same Operator, no doubt different atmospheric conditions... and very different exhaust systems.

[tuscanturner]

Some info from the original owners work. Although a number of items have been changed but it makes interesting reading and shows what was happening many years ago in the Cerbera world. Now you may understand why I was expecting a few more horses 😁

Full refurb, new everything
Enlarged, hand-radiused intake seats and enlarged throats
3-angle cut exhaust seats and enlarged throats - stds were seriously restricted!
New valve spring with preloads set to 2x std accuracy
Skimmed head decks and timing chest
Chambers reshaped for maximum valve deshrouding, and finely balanced, unlike what was found on the factory-reworked heads - different CR ratios in each cyl, 10.5 to 11.0!
1.2mm solid copper gasket with wired liners (see below)
11.2 CR precisely for each cylinder - not toooo challenging for a road mobile

Bottom-end fully rebuilt and blueprinted by TVR Power
New liners, wired for guaranteed gasket seal - with the solid copper gaskets
New lightened and matched weight rods (originals had suspect little end thicknesses - thanks TVR!)
Finely dynamically balanced
New clutch and hydraulic seals
New studs, bolts, nuts, seals and bearings throughout - all stainless steel outer casing bolts
Engine timing markers and pointer permanently added to timing chest
Engine negative pressure breather catch tank

Intake
Std intake redesigned for maximum power - same side breathing, no cross-over
Inlet tract reduced in length from ~600mm to 450mm tuned to upper rpm range
Intake now taken through bonnet NASCA submerged ducts directly into new airboxes with an intake per bank via large KHN flat filters a - plenums removed to increase top range power
Horrible and mis-shapen purple silicon hoses replaced by beautiful curved aluminum intake pipes - all EXACTLY the same cross-section and length now!
Intake ports enlarged to 42mm at manifold face to compensate for less than ideal 'sharp angle'
Extensive rework and enlargemenmt of downstream throttle body shape to reduce impact of standard mis-aligned casting/line borings and remove the big flow restricting 'elbow' caused by tb being off the port centre line
Intake manifold dowelled to head for exact alignment
Throttle spindle reduced from 10mm to 7mm diam to increase mass airflow capacity
Throtlle plate bolts trimmed to exact length and bolt heads flow-shaped to minimise airflow restrictions
Throttle linkages changed so throttle plates now open in the same direction in each bank with respect to the injector position (removes airflow and fuelling variance between banks)
Std Red Rose injectors retained, now running @ 55 psi fuel pressure

Exhaust
Bespoke large bore exhaust manifolds by BTB Northamptom, fabricated from high-quality 321 stainless steel
Bore:45mm primary, 50mm secondary
Lengths: Primary 34 inch, Secondary 9 inch, all wrapped
Topography: run forward towards nose-cone, crossover, then follow std route back down side of block
No cats (cat back conversion)
3" tailpipes on std back box

Management
Emerald ECU mapped by Dave Walker of Emerald (the very first Cerbera port)
Dual maps - power and MoT

Cooling System
Fully ECU controlled coolant temperature system
Davies Craig electric water pump
No mechanical pump - TVR Factory modification removed it, before they closed down frown
No thermostat
Bespoke ducting channels hot rad air up and out through bonnet vents
5 core rad with adjustable blind
2 x 1800 cfm PACET fans, ECU controlled
Aircon rad and paraphernalia removed - improved airflow and weight reduction
Nose cone crossbar removed - Picture, just look at the picture!!!

Running Gear
3.72:1 race ratio diff with hydratrak limited slip
AP 330mm vented and grooved discs replace std 322mm front disks
Under-chassis airflow deflectors to direct cooling air to front discs
Steel braided brake hoses all round
Nitron NTX adjustable gas dampers all round
Uprated springs - Front: 400lb Rear: 350lb
Std 'spider' wheels. Tyres: F1 Eagles 225x18F, 255x18R

[ukkid35]

I think there is a lot more to come from that engine, it has obviously been subject to a meticulous and very thorough enhancement project. But the numbers aren't there yet, so it's entirely possible that something very simple has come adrift.

The comparison point is my rescued basket case subjected to some amateur work by myself, and Joolz Whirlwind hoses plus his dynamic remap. And when I say basket case I mean a real mess of an engine that has had a vicious (and head to head unequal) skim, original horribly corroded liners, dreadfully varying compression numbers (just over 15%), and half collapsed airbox ports.

I'm sure you'll see some much improved numbers when the culprit is identified.

[tuscanturner]

I see what you mean regarding the graphs. Still impressive

Any thoughts on what could be the issue on mine?

Some of the mods on the list have been put back to normal , the bonnet and air box are back to normal

[HarryW]

Jhonno said:

tuscanturner said:

That manifold!

Superb looking bit of kit. I love threads like this.

Do you have the rough calcs on the diameter and length selections for primaries and secondaries?

I can't recall when I did mine but from memory; You've gone for long primaries which tends be be for low to mid range torque, but large bore sizes which tends to be for higher up the Rev range. I assume hoping for the best of both worlds. I wonder if they've cancelled each other out. If your up for it try seeing what standard headers gives or loses you. You can't beat empirical data.

[gacksen]

does look like massive spec and some serious cash spent.
maybe there is a problem with interacting parts like e.g.
headers induction or anything else. also what sort of cams
are you running are they dialed in correctly ? i guess the map
is spot on as done on the rollers so that cant be the problem.
for sure you would need to remove modded parts to find an answer for
your question like going back to stock manifolds and stock induction
and put it back on the rollers to see the result with plain
modded engine and stock externals.

[tuscanturner]

My thoughts are that it's either the mods to the heads or the manifold. But Because I have bought the car as its is and I know that there have been some changes back to standard, for example the air box is now a standard one I would like to locate the one Julian made and also the inlet pipes ,so it's a little difficult to say what has impacted on the original setup that Julian built. The car is stunning though and I'm look My forward to using it

[Jhonno]

I'm going to guess the old airboxes were much larger?

[FarmyardPants]

I would have thought even a standard spec 4.5 with a remap for those exhaust headers would see 430+

[Byker28i]

FarmyardPants said:

I would have thought even a standard spec 4.5 with a remap for those exhaust headers would see 430+

Is that degrees C under the bonnet? What's the temp like with that much exhaust piping under the bonnet?

[tuscanturner]

Byker28i said:

Is that degrees C under the bonnet? What's the temp like with that much exhaust piping under the bonnet?

I I don't think they are much different to standard ones. They are ceramic coated now rather than wrapped