I'll be building an uprated engine for my Coupe race car over the winter, and am wondering is there an advantage in fitting the 2.4 Stilo crank along with the associated uprated rods pistons etc? I'm not after big power, 400bhp is loads, but the extra torque form the 2.4 may be handy.

What are peoples opinions?

I would speak to Nyssa7 on here about making the 2.4 up to race spec, big difference between fast road 2.4 and race spec 2.4. One of the many things would be the conrods, i believe Nyssa has made the big end made wider

plus solid lifters

Easy enough to get 400bhp and big torque from the 2.0, but after running nearly 600bhp I was looking for a bit more than 400 with appropriate torque so went for a 2.4

With no disrespect to anyone on this forum, nor any Fiat Coupe specialists, or anybody indeed - I sent my engine to a RACE engine builder for opinion in the first instance, then solution and build

Fiat have designed their rods with what appears to be massive side to side float on the big end - seems fine on road cars, my kappa 20vt has done enough miles and there's plenty on here who have done a lot more

But so far I have wrecked 5 race engines, 2 of them snapped rods, another had something give so the pistons met the valves with nothing having broken

So my RACE engine builder tells me this is an "iffy" design for a race engine, I listened

And invested a large sum in a custom set of rods designed by him and Arrows, and paid for my engine (which was yet to run) to be stripped down and rebuilt

And as Rich added, also gone down the solid lifter path as 8000 rpm and hydraulic tappets do not go well together

TBH depends on what you are racing with, how long you expect your engine to last and just how hard you're planning to thrash the hell out of it - no matter what anyone thinks, a road engine will never get the grief a RACE one does

Then the really good news is, expectto treat gearboxes as disposable items, because they won't last long either

And finally - good luck, we're both going to need that!

I prefer the approach to a wider big end with less play to the original Fiat design.

What is the difference in torque between a 2.4 and a 2.0?

Dunno yet, engine not back in the car yet, that won't happen for at least a couple of months yet. Have had cam timing set up to aim for good torque curve in preference to outright power though so won't be directly comparable to the previous engine where it was set up for power

Just my 2 cents regarding the achieving best torque... don't let the chip control when your timing variator turns off, instead use an industrial grade pressure switch to turn off the timing variator prematurely once you have reached a particular boost level. IMHO, the sole purpose of the variator (when it kicks in, i.e., early opening and closing) is to ensure a steady idle (wide lobe separation angle) and better lower end (early opening of the intake valve means you will start building compression sooner). Once it reaches a significant level of boost, which depends on how it’s tuned, you can turn off the timing variator to allow more air to flow into the cylinder as the turbo is generating enough flow, so you will need it to be closed so that it opens and closes later. JohnS mentioned something similar sometime ago, and it’ll be best to test various settings to get the best overall setup(look at where the torque chart intersects with different settings). I’m using SMC pressure switch to turn off the variator when boost is above 1 Bar and it made a world of difference.

Most turbocharged engines are “knock limited” and it’s the same for the 20VT, imagine boosting to 1.8 bar with the variator turned on (it cuts off at 4800 rpm on the standard chip and 4000rpm for novitec and G-Tec) vs. 1.8 bar with the variator turned off. For the former setup, if the peak boost level is reached before the variator is turned off, it will probably be knocking like hell, for the latter setup, with the variator turned off, it has retarded the timing by 18 degrees, which means although it will lose a bit on compression pressure, however, the turbo is now generating more air flow into the cylinder to make up for the compression loss. One more big advantage is that the air flow from the turbo is intercooled, while air compressed inside the cylinder is not, and hence more prone to knock. A bit lengthy but I hope someone will find it useful.

The little green genie in the middle of the steering wheel is the SMC


Cheers,

David, that is very interesting, never heard of such a thing in reality, I may look into this further

Does sound very logical.

Hi Taz,

Just realized that our registration date on the forum is only 2 days apart

IMHO, turbocharged engines should be tuned according to boost level in most respects and not according to rpm only (Fiat's idea of controlling the variator cheaply as it does not have a MAP sensor for the boost level). Check out this link for pressure switches: SMC

Because I don't need to worry about knock, so I usually just boot it and use scramble mode for the AVC-R...I've also tested every cylinder for compression and matched it with precise injector dynamic flow range(@ 3.8 bar fuel pressure 80% IDC)

Cheers,

David

Very interesting stuff David. I was very surprised to know that OE chip uses the variator more than GTec and Novitec. Is this because engine with tuning chip hit boost earlier than original engine (with original chip)?

Do you have time to show us how you installed it with all wires etc?

Maybe you have a nice wiring scheme next to you.

Hi,

I'll try to draw up a relay to illustrate how it's done later as I'll be traveling next week. The OE and novitec altered the rev in which the variator is shut off...merely to demonstrate that they can...rather than for tuning reasons. A bigger turbo might be laggier, so I would imagine that the vatiator should be shut off at the same rev if not later. But this depends on how the car is tuned in other respects. I'm running a GT2864RS and I start boosting at 1500 rpm and reaches 1 Bar around 3000 rpm, once the variator is shut off, it goes all the way to 1.8(peak) and then maintained at 1.7 or 1.6 depending on which button you press

Cheers,

David

Which gear did you use?

I'm looking forward to see your illustration

I would be interested to see how this works, on a race car I don't care about lumpy idle and stuff, and the mapping can clean it up anyway, but I do need the torque to come in as low as we can manage and with as little lag

Was thinking of just disabling the variator in its high revs position

Surely you use the variator to get torque just like Fiat did? I find it hard to see how you could benefit from taking it off..?

David any news for us?

Sorry, I've been traveling for the past couple of months. The reason the oe chip uses the variator more, is due to the fact that the conservative ignition map allows the engine to be more knock tolerant. With Novitec and G-tec as the ignition map have been more aggressive (more advanced), hence the engine is more prone to develop knock, hence, the timing variator must be shut off earlier to prevent this.

In brief, it's just like the reverse of the fuel pump relay mode. First, we need to locate the relay with the metal casing on the passenger side (left) or the suspension upper mount.



Then we need to know which pin out stands for, by referring to the repair manual. From the ecu pin out, you can see that #52 controls the variator. When you blip the throttle and when the water temp is above 40 degrees, the ecu will send out a signal to the variator relay to turn it on.


Referring to the detailed schematic, we can see that #27 is the solenoid of the variator, #22 being the relay for it.


Referring to the above schematic, we can see the for #22(normally closed relay), there are 4 pins, namely, 30(battery terminal(+)), 86(ground), 87b(signal to the variator solenoid), 85(connects to the signal from the ecu pin#52). Now, we know that once the car is warmed up, the variator comes on whenever the throttle is pressed (below 4800 rpm). And all that we need is to be able to turn it off prematurely, so we don't need to temper with the pin 85 that's connected to the ecu #52pin. We need to modify pin 87b so that it goes through another relay before entering the solenoid. The additional relay used is one that is normally closes(#30 to #87) and when signals are given, it is opened (so that the circuit for the solenoid is broken).By doing so, we can use the SMC or any pressure switch to turn off the variator at any given pressure that we desire.



I hope I've not complicated a simple job
The easier way would be to use a Hobbs switch rather than a pressure switch, but then you will need to know the working pressure range with each turn.

Cheers,

David

Thanks David

Thank you very much David !

Forgive me if this sounds like a stupid question - I did think the variator was opened by oil pressure without really thinking about how

For those of us running non-Fiat ECUs, does this mean the variator doesn't get opened?

Most of us long term forum users will have registration dates close together because the old forum was lost back in 2005 and we all had to re-register

Hi,

yes - you have to use a separate channel of your motec to get it functional.
I used my "boost - output" of my KMS, because you will need a channel which switches on over idle and switches off at higher revs again (means two different switch - points)...
else you will loose cylinder filling / some torque in medium revs...
Juergen

DavidL -your inbox is full..:(
Stichl and DavidL , I need base info about 2.4 conversion. I have to order conrods but i don't know exactly height/all dimensions . I took a stilo 2.4 service/repair manual and is.. beautiful (e-learn) but Absolutely USELESS
Cheers,

Sorry, been traveling again, just to revive the old thread. The variator is opened by solenoid that sits between the #1 and #2 plenum, which in turn lets the oil pressure push the intake camshaft forward (in respect to value timing). So in a sense, you're also right.