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[What's Burning?]

I had a Metro that had a blown exhaust, it failed its MOT.

Yeah but you picked up 2 or 3 tenths a lap right?

[Jabberwocky]

yes I set the lap record around Tescos car park.

it was loud I remember that much. lost a lot of torque as well.

[smokin]

smokin wrote
Retarding makes the mixture too rich (I think I've got that right) which would cause fuel burning in the exhaust. Dangerous with a blown exhaust directed onto bodywork without the engine damage. Might work for short sprints, though.

Retarding the timing doesnt change the air/fuel mixture,it simply changes the moment when the spark plug ignites. Retarding is delaying spark, advancing the timing ignites earlier in relation to the postition of the piston to TDC(top dead center).

What this means is that some small amount of the air/fuel mixture has already left the cylinder & started to travel down the exhaust manifold........ but this idea is very unlikley to work.

If your engine can rev to 17000-18000rpm the piston will be traveling so fast the engine needs a huge amount of ignition timing advance just to give the fuel enough time to actually burn compleatly before exiting the cylinder.... any over run is a waste of fuel & will cost you power.

But if only used for qualifying i guess it could work............. but hey i dont design F1 cars for a living,so who knows how it really works? It would explain their constant quali advantage!

Thanks, Capt. I didn't think I was quite right but it still sounds a bit iffy to send a flammable mixture through a red hot exhaust. I'll watch carefully for signs of a backfire as the Bulls enter a corner.

[SaintDean]

My fiesta suffered a blown exhaust, it couldnt get up a small hill

[Jamie]

I think it has made a slight difference to Ferrari's performance in a way. I think it could show a good upgrade this weekend, & prove that he has made the right decision in the upgrade. Com'On Ferrari

[zweiblumen]

Seems McLaren have abandoned the upgrades for this weekend - http://www.autosport.com/news/report.php/id/85141

[SaintDean]

Seems McLaren have abandoned the upgrades for this weekend - http://www.autosport.com/news/report.php/id/85141

they have the new front wing in FP3 but to be honest it wont work because it was built with the blown diffuser in mind so the balance wont be right.

Tough times for mclaren.

[Frosty]

So the upgrades were giving the expected down force levels so the lap time is there but there were some pretty major balance issues which stopped the drivers extracting the lap time.

[SaintDean]

Just got to wait and see, in Valencia in practice they seemed well off the pace didnt they. But then thought back in Qualifying and Race.

[Denthúl]

Something interesting i read on jamesallenonf1.co.uk a few days ago might be related to this:

One interesting observation is that Red Bull has a setting on the engine, whereby the ignition is retarded on the over run, which maintains exhaust gas pressure even when the driver lifts off the throttle. This maintains the performance of the blown diffuser and keeps the downforce up when it’s most needed. It’s not something you can do for more than a lap or two as it damages the engine, but it gives that vital fraction of a second which keeps Red Bull ahead of the rest in qualifying.

Now that really is interesting!

[Frosty]

Something interesting i read on jamesallenonf1.co.uk a few days ago might be related to this:

One interesting observation is that Red Bull has a setting on the engine, whereby the ignition is retarded on the over run, which maintains exhaust gas pressure even when the driver lifts off the throttle. This maintains the performance of the blown diffuser and keeps the downforce up when it’s most needed. It’s not something you can do for more than a lap or two as it damages the engine, but it gives that vital fraction of a second which keeps Red Bull ahead of the rest in qualifying.

Now that really is interesting!

What I think has been made clear is that Red Bull optimised their car for Red Bull.

[Fred_C_Dobbs]

smokin wrote
Retarding makes the mixture too rich (I think I've got that right) which would cause fuel burning in the exhaust. Dangerous with a blown exhaust directed onto bodywork without the engine damage. Might work for short sprints, though.

Retarding the timing doesnt change the air/fuel mixture,it simply changes the moment when the spark plug ignites. Retarding is delaying spark, advancing the timing ignites earlier in relation to the postition of the piston to TDC(top dead center).

What this means is that some small amount of the air/fuel mixture has already left the cylinder & started to travel down the exhaust manifold........ but this idea is very unlikley to work.

If your engine can rev to 17000-18000rpm the piston will be traveling so fast the engine needs a huge amount of ignition timing advance just to give the fuel enough time to actually burn compleatly before exiting the cylinder.... any over run is a waste of fuel & will cost you power.

But if only used for qualifying i guess it could work............. but hey i dont design F1 cars for a living,so who knows how it really works? It would explain their constant quali advantage!

A richer mixture burns cooler than a leaner mixture because it produces more CO vs CO2, and less heat is released from the production of CO than from CO2. Plus there's a slight increase in mechanical cooling from the richer mixture's additional fluid. Most piston-engined aeroplanes have a manual mixture control. To conserve petrol in cruise flight, pilots are trained to lean the mixture to the point of highest exhaust gas temperature, then enrich it by a certain number of degrees to preserve the engine.

IIRC, the 3.4 litre V-10s were running ~60° advance, and they revved to ~18K rpms (+/- 1.2K), so the current lot of V-8s probably are near that same advance.

Might RBR be running an accelerator pedal position-sensitive ignition timing? Something that would drastically retard the timing unless the accelerator pedal were mashed to the floorboard? There would be no real loss in power because full power always is available, but every time the driver lifts (or is at part throttle), there's a higher exhaust gas pressure than there otherwise would be because the fuel mixture is still burning (and hence, hotter) when it rushes out the exhaust port.

[bud]

Could it be as simple as a setting for nuetral, or when they lift for a corner the drivers engage the clutch keeping the revs high and keeping the blown exhaust air coming when they need it the most

[MAD MAX]

I had a Metro that had a blown exhaust, it failed its MOT.

pmsl

[Fred_C_Dobbs]

Could it be as simple as a setting for nuetral, or when they lift for a corner the drivers engage the clutch keeping the revs high and keeping the blown exhaust air coming when they need it the most

There is no coasting in F1. Even in the slowest corners, they run twice the sideloading of the upper limit of the best handling street autos. Under those conditions, the car will slow dramatically any time the driver isn't applying serious horsepower.

Also, whether accelerating or de-accelerating (which, in the case of an F1 car, is virtually all the time), so long as the clutch remains engaged, the engine contributes to the grip available to the front tyres. I would think removing the effect of the engine from that equation would work at crossed purposes to the blown diffuser.

Not to mention the dynamics of mid- and rear-engined cars get wonky if you clutch or brake while in mid-corner.*

*The book of Porsche, Chapter 1, Verses 4-7