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Increased cylinder filling..

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Just finished up dyno tuning my track fiesta st180 which has a 1.6 ecoboost ford engine.

Everything went well and we made good power, we are on a standalone ecu. SCS delta GDI6.

The engine is fairly well insturmented and I have some good data.

My question is: Bigger valves and more lift should equal more cylinder fill?

During tuning we obviously started at low boost levels. .8bar on wastgate pressure finally ending up at 1.6 bar for peak power. We mapped to MBT and the engine wasn't making more power with more IGN. Upping the boost was giving lower increments in power gain. So we left as it was at 1.6 bar peak.

For me tuning is balcance of what's achiveable against what's releaible. So I am no fan of smashing boost into the motor to get a number.

I can see from my EMAP numbers the turbine still has more to give. The head has been worked and we are using a STG2 cam. There is no point in adding more CAM duration as we are out of revs at 8k. That's the limit of the DI system.

EMAP attached is 1.4bar map, i will get a 1.6 bar. It's to give a flavour of the turbine sizing we are working with. The turbo is an s290 development unit, larger than the common s280 used in the UK on these cars. No compressor Map is avaiable..

Would appreciate thoughts, happy to supply more data.

Attached Files

'My question is: Bigger valves and more lift should exqual for cylinder fill?'

It's not always the case, you've your car wired up well for development and measuring everything so will be prefect for development, did you try swinging the VVT at all on the dyno?

Hi Chris.

Yes, VVT has been dialed, we picked up like 25hp just on VVT changes.

Hi Richard,

i am not sure if i can help about filling,but what CR are you running? With my experience,a lower CR with more boost end up with more power if you are sure your turbo is capable for more,i was also limited by these factors on my EP6 4cylinder 1,6 engine,and what fuel do you use? Power output?


I love the thought process, trying to predict optimal engine changes based on sensor data with the current setup.

While the turbo is upsized, the turbine housing and wheel are likely far more related to the relatively high EMAP/MAP ratio you have at the current airflow. I'd expect far more of a gain from fitting a larger turbo of similar quality, than additional lift, valve size at this point.

Beyond that, I find stock size valves in modern turbocharged engines generally work really well until the platform has been pushed really far, and big valves often significantly degrade drivability without substantial gain until you've exhausted most other improvement options.

Beyond that, it depend what your goals are, how you want to use the car, if you'll be limited by class rules and cannot fit a larger turbocharger so you're forced to look elsewhere for gains. Please let us know.

Hi Mike,

So the turbine is like a GT28 frame size. it's an internally gated turbo. I didn't want to go to all the hassle of an external gate. The actuator is decently sized, so there is no boost creep.

I do have an option of trying another development unit with slightly larger wheels.

The challange with DI engines is fuelling them, We have had to get more stroke on DI pump so it keeps it up with dropping pressure. Going bigger on the turbo again, means bigger headaches on this side and the low pressure side. However the ecu can run a port setup as well.. but again more complexity.

I've attached the cam spec we are running plus the option I would go for.

Currently: BP285

Would move to: BP320

It will be interesting to see VE changes by adding additional 1.5mm of lift. It should work in theory, but theories need to proven.

Pistons have already been pocketed for clearences.

The EMAP ratio of 1.6:1 is right at the top end so I'm not massively concerned about this as EMAP is very dirty signal anyway. It's closer to 1.35 across the rev range rising from 6k which tells me we are limit of sizing really.

Goals are a reliable 400hp, We are close. It will just be used on track. So a usable 4k rev range is fine. Not constained by regs at all.

Attached Files

Short answer - it depends.

long answer - it depends on many factors.

Some engines may benefit from larger valves and/or more lift, some may not.

When discussing "lift", it's important to consider the actual profile - depending on the valve train this may require longer duration which affects both the opening/closing points, and the overlap. With direct acting - bucket followers - there may be limitations in the follower diameter, which affects the cam profile and accelerations possible. With indirect operation - rocker and finger type followers, it may be possible to alter the pivot points to change the ratio, and so it may be possible to alter lift while keeping the same nominal timings for opening and closing.

As it is, you're in a position where you can experiment with different camshafts and the VVT option means you can more quickly test for the best cam' timings for the best torque curve over the operating range.

Few things:

If you improve engine VE, you're going to need to deliver more fuel to achieve the same lambda result if you want to make use of the improvement to generate more HP than you have now. If your DI system is truly maxed out and you aren't ready to add port injection, I'd leave the engine alone. Your current dyno graph looks like a great drivable curve for a track Fiesta.

As Gord mentioned those cams are rather different, not just in terms of max lift, so there's a lot to consider.

My experience has thus far indicated that MAP, EMAP readings are not sufficient to determine the specific outcome of a cam swap like this because as Gord mentioned there are a lot of variables, and a lot of data you aren't being given, such as the complete profile of each camshaft.

If we put the fuel system concern aside for a moment, given your EMAP/MAP ratio I'll just say if it's a twin scroll turbo setup, then I'd be more inclined to try the longer duration cam you're considering.


100% agree. We are not at 100% duty on the pump for obs reasons; we have a touch of headroom but not much.

Thanks, yes it's a good graph, more importantly it drives nice and we have plenty of power for our wet weight of 1000kg.

I agree, they are very different, but they are in an engine I have comparative data with, it's on a very slightly larger frame turbine with similar response but lower MAP. 200mbar less and makes decent chunk more power, like 30hp at the top end.

It's not twin scroll.

I agree the emap isn't a good view of cam changes, it was more using it to show we are hitting peak emap at peak rpm and are exhaust sizing is in the ball park with a bit left on the table.

So Plan after everyone’s input:

1. Try the very slightly larger turbo. That's easy.

2. Try the different cams see what it does.

Pick the best outcome. Let the experiments commence.

I will report back..

Excellent. We look forward to hearing your results.

Soo, I've been beavering away in the background.

New cams have been cut. Same duration and timing as the origional cam, but an additional 1.25mm of lift.

Will be testing them shortly..

Attached Files

We tried cams with higher lift a few times and every time found more power all else being equal. I've heard it before that turbo setup runs on the "lift" so from my experience i would say you're going to gain a few pony...

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