whats wrong with the renault engines?

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Phil
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Re: whats wrong with the renault engines?

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I hadn't thought about the ICE actually. I was more thinking about the simple fact that with every higher gear, the torque at the wheels is significantly less, which is why even after the drop-off point, the engine might still be producing more power/torque at the wheel in that gear than shifting up. The main question is: how much torque at the wheel is the engine producing past its bhp-peak and how does it compare to the next higher gear at its lower RPM number.

Take this graph for example (posted in the what's wrong with the renault engine thread):

Image

The difference between torque at the wheel between gears is so high that even after the BHP drop-off (which we don't see here since it only shows torque, but we can guess), you still have way more grunt than if you were to shift to the next higher gear. In F1 and thanks to 8 gears (closer gearing) this is of course minimized since all the gears would be closer to each other, but without knowing the exact drop-off, it's hard to say for sure.

If we assume that these engines produce max BHP at 85% of the rev range, we still don't know how much they produce say at the rev-limit. My guess is you would still have a gain to rev until 90-95% before upshifting (assuming engine reliability and strain is not an issue). How much this would yield over an entire lap is anyones guess though... My main point was more that it does make sense to rev higher than the peak BHP rpm point if you take gearing and the drop off into account. It's not as if the engine peak power suddenly drops to zero after it's max point.
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Blackout
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Re: whats wrong with the renault engines?

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We're talking about the power unit myurr, not about RBR or the chassis etc. All what you said is generally true, but we know it and it has been written two thousand time already here.
We are looking for new infos and we try to elminate what is working well in that PU and find out what's working wrong as exactly as possible.

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rscsr
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Re: whats wrong with the renault engines?

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Phil wrote:I hadn't thought about the ICE actually. I was more thinking about the simple fact that with every higher gear, the torque at the wheels is significantly less, which is why even after the drop-off point, the engine might still be producing more power/torque at the wheel in that gear than shifting up. The main question is: how much torque at the wheel is the engine producing past its bhp-peak and how does it compare to the next higher gear at its lower RPM number.

Take this graph for example (posted in the what's wrong with the renault engine thread):

http://i59.photobucket.com/albums/g288/ ... ph_134.png

The difference between torque at the wheel between gears is so high that even after the BHP drop-off (which we don't see here since it only shows torque, but we can guess), you still have way more grunt than if you were to shift to the next higher gear. In F1 and thanks to 8 gears (closer gearing) this is of course minimized since all the gears would be closer to each other, but without knowing the exact drop-off, it's hard to say for sure.

If we assume that these engines produce max BHP at 85% of the rev range, we still don't know how much they produce say at the rev-limit. My guess is you would still have a gain to rev until 90-95% before upshifting (assuming engine reliability and strain is not an issue). How much this would yield over an entire lap is anyones guess though... My main point was more that it does make sense to rev higher than the peak BHP rpm point if you take gearing and the drop off into account. It's not as if the engine peak power suddenly drops to zero after it's max point.
The Cosworth data indicates that they will rev between 11000 and 13000rpm for max acceleration. (At least for the gearing and Drag which I used)
Here are the charts for the V8 and V6 in sustained mode. http://www.f1technical.net/forum/viewto ... 13#p484513

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raymondu999
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Re: whats wrong with the renault engines?

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Just curious - why is everyone so keen on heat being the issue? I'm not saying heat is not the issue - but it could always be the symptom rather than the cause. It would probably be much harder to replicate cornering forces in the dyno - could it not be that some part is failing under constant cornering?
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Lycoming
Lycoming
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Re: whats wrong with the renault engines?

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I guess it's a possibility, but while the cornering loads haven't changed significantly, thermal load has increased significantly. Besides, cornering loads are just inertial loads. Even at 5G, that won't put much stress on most of the components. The big loads are things like dumping the clutch at redline, or apparently, sudden torque application from an electric motor.

Robbobnob
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Re: whats wrong with the renault engines?

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Well in reality the cornering forces will pale in comparison to the dynamic forces internal to the engine.

Comapring a V6 to a V8, there is less rotating mass on the crank shaft, as well as less rotating mass being driven by the crank, therefore any dynamic imbalance of the engine will be less severe, however solving these issues is rather trivial and is a well understood subject. Any such issue would be a vast oversight on Renaults behalf.

One of the obvious differences is the increased intake pressure due to the turbo charging. This will increase the MEP (mean effective pressure) of the engine. Components dealing with the intake fluid, such as the valves, valve seats, piston, piston rings and piston liners; will all have to be re-engineered to take the increase in stress applied to the parts. Again a fairly fundamental concept of ICE design.

Cooling and fluid delivery, again issues which are easily solved and are apparent in early prototyping.
Not to mention all of the above are testable on a dyno.

Any cornering forces wouldn't appreciably stress any of these components beyond their working limit.

That leaves system fluids, such as oil and water flowing inwards and outwards of the system... could they possibly be affected by cornering loads, yes.. But again these are well understood issues of a racing car.

The one thing that is hard to simulate on a dyno is heat rejection. Particularly as they might not simulate the engine as a complete unit, in the same proximities to the ancillary components.
Producing baselines for the heat rejection for the individual parts might prove to be trivial on their own, but couple them in a tightly packaged system, surrounded by the radiators, you suddenly have heat soak becoming an issue. The heat being put off by the oil radiator might raise the mean temperature experienced by the turbo control module by 5 degs, enough for the semi state transistors/ control circuitry to change its resistance behaviour significantly enough to alter the critically damped response for turbo spool.. over shooting, under shooting etc.

There are many complications that can be caused by an increase in operating heat. Mechanical parts particularly suffer from interference issues, electrical components can suffer from magnetic feedback, fluid components are effected by a change in viscosity and the drag effects.

That being said, I am not discounting the possibility of a mechanical system failure. Again the timeframe in which they had to test these engines was really tight and sometimes even the best get it wrong.
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kptaylor
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Re: whats wrong with the renault engines?

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Sorry, dumb question... Does the 28 Feb date for homologation refer to just the ICE, or does it include the ER systems (the entire power unit), too?

langwadt
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Re: whats wrong with the renault engines?

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Lycoming wrote:I guess it's a possibility, but while the cornering loads haven't changed significantly, thermal load has increased significantly. Besides, cornering loads are just inertial loads. Even at 5G, that won't put much stress on most of the components. The big loads are things like dumping the clutch at redline, or apparently, sudden torque application from an electric motor.
unless there is something seriously wrong with the software the electric motor should/could be silky smooth

langwadt
langwadt
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Re: whats wrong with the renault engines?

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kptaylor wrote:Sorry, dumb question... Does the 28 Feb date for homologation refer to just the ICE, or does it include the ER systems (the entire power unit), too?
it is the whole power unit

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Abarth
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Re: whats wrong with the renault engines?

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In another Forum, an insider (thats for sure) gave a fantastic information about the Renault issues and how they will solve them:
For those interested. Here are some of the changes Renault have made since Jerez.

Change of battery cell provider. The individual cells that make up the Energy Store have individual over-charge and over-discharge protection. These were proving unreliable due to thermal/vibration issues. Whilst the energy store is sealed in our fitment, I am informed the cells are now supplied by Panasonic.

Change to MGU-K to Crank drive gearing. The original torque multiplication factor was calculated to give a wider spread of torque on acceleration. Track testing found that this was causing traction dificulties and overloading the gearset and causing failure of the crank casing.

Change to turbocharger wastegate function. Renault had originally intended for the H to regulate Turbine speed in 95%+ of normal running. They facilitated this by allowing the H to pull charge (when the energy store was at capacity) to an air cooled heat sink. This strategy proved ineffective in certain environments and a more coventional wastegate is now being used to supplement the H.

Due to both the change in K gear ratio, boost control strategy and the energy store, most of the software relating to the charge and discharge cycling has been modified daily and continues to be refined. There are still issues relating to turbine speed control via H but these are mostly to do with fine tuning of the control software and the syncronisation between H control and wastegate control.

There has been swift progress and software related driveability now appears to be the main issue.

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Blackout
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Re: whats wrong with the renault engines?

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Great.
And:
Re the H to K transfer.
There are times when you can't (or wouldn't want to) transfer power from the H to the K but still need to limit turbo speed.

Think along the lines of a short burst of accel then slight decel then accel (such as feathering throttle for traction or in a switch back). The last thing the driver would want is for the K to feed power into driveline.

During those transitional situations Renault wanted to control the speed of the turbo by using the H to maintain shaft speed at or close to max rpm. It turned out (partly because of the driveability issues) that H was dumping to the heatsink far more than had been predicted or modeled. This was causing severe heat related issues in some cars at Jerez and the Renault 'patch' was to disable the H entirely and rely on the mechanical wastegate for the remainder of the test.

Obviously this resulted in dramatically increased lag and reduced performance but allowed some mileage to be put on the ICE.

In the interests of transparency it should be disclsclosed that we have had no first hand experience with the original spec PU used in Jerez.

Our running experience started with a version that had basic H functioning and limited K output.

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iotar__
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Re: whats wrong with the renault engines?

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Actual information? Get out of here.

[About earlier theory I'd say they weren't driving fast enough for cornering forces to be an issue. ;-)]

beelsebob
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Re: whats wrong with the renault engines?

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I'm puzzled by the "waste gate gets used some of the time" assertion. I was under the impression that that was banned in the regs.

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Juzh
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Re: whats wrong with the renault engines?

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beelsebob wrote:I'm puzzled by the "waste gate gets used some of the time" assertion. I was under the impression that that was banned in the regs.
They're used as a fail-safe device in case of mgu-h malfunction which could cause catastrophic ICE failure.

beelsebob
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Re: whats wrong with the renault engines?

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Juzh wrote:
beelsebob wrote:I'm puzzled by the "waste gate gets used some of the time" assertion. I was under the impression that that was banned in the regs.
They're used as a fail-safe device in case of mgu-h malfunction which could cause catastrophic ICE failure.
Sure – I know they exist, and they're used as a fail safe, but the assertion above is that they use it in normal running.

Aside – this may go some way to explaining why RedBull have heat issues – using the waste gate would imply dumping extremely hot air into the body of the car, which would naturally cause them to get a surprise on the amount of cooling needed.