Speed with Guy Martin - new series
Discussion
anonymous said:
[redacted]
My non-turbo rental Ford SUV was being overtaken by lorries on the Andes main roads and a 'bit' slow at 4200m, similar toPikes Peak.My old Octavia vRS (remapped, of course...). was fine accelerating over Alpine passes.
Edited by MC Bodge on Tuesday 4th November 10:28
Megaflow said:
He also lived with a parents until recently. He claimed there was no point in buying a house, because he wouldn't live long enough...
Does anybody know if he still has the V12 Vantage?
In a recent interview he said that he had sold it as he had been very disappointed with it. Mainly its build quality. He said it had been his dream car to own but it didn't live up to his expectations. He then went on to buy the tricked out Volvo estate.Does anybody know if he still has the V12 Vantage?
chrisga said:
[pedant] Hope he wasn't wearing alpinestars when he was hanging out with Rossi at the Dainese ranch event... [/pedant]
https://www.youtube.com/watch?v=3tjI3v58OR8
I'm sure I read somewhere a couple of years ago that GM was (is?) getting something like £250k per year from Dainese, even before he had done any mainstream media stuff ?https://www.youtube.com/watch?v=3tjI3v58OR8
Guy at pikes peak, explaining whats wrong with the bike. Sounds like they had trouble getting the fuel mapping right because of the air pressure. (but its a bit hard to make out).
https://www.youtube.com/watch?v=6woPgU4vqnU
https://www.youtube.com/watch?v=6woPgU4vqnU
OK, it's a turbo engine, why are they using Baro as a correction?
one would hope he's using MAP (absolute) as the 'load' in which case altitude makes no odds?
As a second thought, this would assume that he has the fuel reg referenced to MAP? if not, then are they trying to use Baro to correct for the dropping fuel pressure? (really bad idea...)
for ref, 700mbar is about 10,000 feet.
one would hope he's using MAP (absolute) as the 'load' in which case altitude makes no odds?
As a second thought, this would assume that he has the fuel reg referenced to MAP? if not, then are they trying to use Baro to correct for the dropping fuel pressure? (really bad idea...)
for ref, 700mbar is about 10,000 feet.
Don't forget he's doing these challenges for the TV series and they'll be largely funded by the production budget and schedule which means he won't have the time and resources he might have wanted and got if he had taken them on himself.
There is also always a desire in TV to create jeopardy. Usually before every ad break there's some sort of cliff-hanger to keep you tuned in. So the more problems he encounters the better it is for the production and the less likely they are to pull out all the stops to get them fixed.
I'm not saying they would set him up to fail, but the result they got from that particular episode was TV gold. A bike which wasn't running well and kept stopping ends up winning by just 1 second!
If this was on Top Gear, everyone would be saying it's a fix but with Guy involved we know there's a fair degree of integrity. At least I'd like to think so.
You still should never believe everything you see on TV though.
There is also always a desire in TV to create jeopardy. Usually before every ad break there's some sort of cliff-hanger to keep you tuned in. So the more problems he encounters the better it is for the production and the less likely they are to pull out all the stops to get them fixed.
I'm not saying they would set him up to fail, but the result they got from that particular episode was TV gold. A bike which wasn't running well and kept stopping ends up winning by just 1 second!
If this was on Top Gear, everyone would be saying it's a fix but with Guy involved we know there's a fair degree of integrity. At least I'd like to think so.
You still should never believe everything you see on TV though.
Max_Torque said:
Scuffers said:
one would hope he's using MAP (absolute) as the 'load' in which case altitude makes no odds?
Oh yes it does!!! It makes plenty of Odds! (have a think about turbo pressure ratios and efficiency.......)yes, lower baro on the turbo will probably lead to lower E-MAP (for a given MAP)
Now, I guess if the change is significant (and let's face it, it could be almost non-existent), then I guess you may have slightly higher air-mass ingested for the same MAP?
this of course depends on a lot of other stuff, the cam profiles/overlap, the exhaust work between the engine/turbo and final exit, the turbo itself along with the wastegate, etc etc etc.
So, yes, I can see it having a very small effect (on fuelling), however, I very much doubt anything like the issues he appeared to be having (and they talking about the fuel valve - so I assume fuel reg?).
I would also assume that one would be running a wideband to be able to track/correct any effects like this.
is that what you are getting at?
Say you want to make 1.5bar(gauge) boost in the plenum:
At sea level, where Baro is 1bar(abs), that's a compressor pressure ratio of 2.5
At the top of Pikes Peak (4300m / ~59kPa(abs) that's a compressor pressure ratio of 4.24
Take a look at a typical compressor map. See what happens to the efficiency between those two pressure ratios. Now work out the power consumption for each point. Now use the Turbine map to estimate the Turbine pressure ratio required to provide that power. Now recalculate the engine pressure ratio. If you want to maintain the same performance, you actually need a higher engine pressure ratio at altitude because your spark efficiency will also be affected by the increased exhaust gas residual fraction at EVC!
Minor effect it is not!
At sea level, where Baro is 1bar(abs), that's a compressor pressure ratio of 2.5
At the top of Pikes Peak (4300m / ~59kPa(abs) that's a compressor pressure ratio of 4.24
Take a look at a typical compressor map. See what happens to the efficiency between those two pressure ratios. Now work out the power consumption for each point. Now use the Turbine map to estimate the Turbine pressure ratio required to provide that power. Now recalculate the engine pressure ratio. If you want to maintain the same performance, you actually need a higher engine pressure ratio at altitude because your spark efficiency will also be affected by the increased exhaust gas residual fraction at EVC!
Minor effect it is not!
Max_Torque said:
Say you want to make 1.5bar(gauge) boost in the plenum:
At sea level, where Baro is 1bar(abs), that's a compressor pressure ratio of 2.5
At the top of Pikes Peak (4300m / ~59kPa(abs) that's a compressor pressure ratio of 4.24
Take a look at a typical compressor map. See what happens to the efficiency between those two pressure ratios. Now work out the power consumption for each point. Now use the Turbine map to estimate the Turbine pressure ratio required to provide that power. Now recalculate the engine pressure ratio. If you want to maintain the same performance, you actually need a higher engine pressure ratio at altitude because your spark efficiency will also be affected by the increased exhaust gas residual fraction at EVC!
Minor effect it is not!
err.. come again?At sea level, where Baro is 1bar(abs), that's a compressor pressure ratio of 2.5
At the top of Pikes Peak (4300m / ~59kPa(abs) that's a compressor pressure ratio of 4.24
Take a look at a typical compressor map. See what happens to the efficiency between those two pressure ratios. Now work out the power consumption for each point. Now use the Turbine map to estimate the Turbine pressure ratio required to provide that power. Now recalculate the engine pressure ratio. If you want to maintain the same performance, you actually need a higher engine pressure ratio at altitude because your spark efficiency will also be affected by the increased exhaust gas residual fraction at EVC!
Minor effect it is not!
Assuming you have selected an appropriate turbo, etc etc, (and yes, in this case, that's probably a big if!) you have yet to actually point at anything that will require major corrections to the fuel table.
yes, it will make some difference, but I would not expect to see vast changes in fueling requirement.. (for a given MAP value).
(now, I do accept that the boost control loop will have to have baro correction, else boost will follow altitude and fall in absolute terms, but that's not what we are talking about.)
me thinks your just trying to show off now.
(and yes, before you go on, I have spec'ed, setup and mapped one or two turbo engines before)
Edited by Scuffers on Tuesday 4th November 20:08
This is the fuelling correction table for variations in Barometric Pressure on my 500BHP Turbocharged engine.
That gives me a correction that will work up to 3000 Metres, where at that altitude the injector duty would be 79% of the duty applied at sea level. If I were doing Pikes Peak you would be looking at needing a BAP Correction that would use probably 65% fuel duty at the summit.
So yeh, you certainly need to correct for BAP changes, its just an additional correction on top of all the others.
That gives me a correction that will work up to 3000 Metres, where at that altitude the injector duty would be 79% of the duty applied at sea level. If I were doing Pikes Peak you would be looking at needing a BAP Correction that would use probably 65% fuel duty at the summit.
So yeh, you certainly need to correct for BAP changes, its just an additional correction on top of all the others.
Scuffers said:
ok you need to explain that, unless absolute map is falling, or the proportion of oxygen in the air is changing, why are you reducing fuel to that extent?
Because the absolute pressure ratio across the engine is falling dramatically as turbocharger work increases and compressor efficiency falls!Casting my mind back to thermodynamics...
If the turbo can't work efficiently then there is a large amount of heat generated and it can't be effective at pressure ratios outside of a certain range.
Basically, you can't just maintain inlet pressure in ever decreasing ambient air pressure (or increasing temperature). Less air requires less fuel.
It's not desirable to fit an enormous turbo that would suit only flat-out at 4000m.
Selecting a turbo would require a choice of whereabouts on the course you required greatest efficiency and would be different to sea level.
....Other words such as Adiabatic and entropy are involved....
If the turbo can't work efficiently then there is a large amount of heat generated and it can't be effective at pressure ratios outside of a certain range.
Basically, you can't just maintain inlet pressure in ever decreasing ambient air pressure (or increasing temperature). Less air requires less fuel.
It's not desirable to fit an enormous turbo that would suit only flat-out at 4000m.
Selecting a turbo would require a choice of whereabouts on the course you required greatest efficiency and would be different to sea level.
....Other words such as Adiabatic and entropy are involved....
Edited by MC Bodge on Tuesday 4th November 22:58
Edited by MC Bodge on Tuesday 4th November 23:09
MC Bodge said:
Casting my mind back to thermodynamics...
If the turbo can't work efficiently then there is a large amount of heat generated and it can't be effective at pressure ratios outside of a certain range.
Basically, you can't just maintain inlet pressure in ever decreasing ambient air pressure (or increasing temperature). Less air requires less fuel.
It's not desirable to fit an enormous turbo that would suit only flat-out at 4000m.
Selecting a turbo would require a choice of whereabouts on the course you required greatest efficiency and would be different to sea level.
....Other words such as Adiabatic and entropy are involved....
yes, if the turbo has to work harder and heats up the intake air more, then for a given MAP, the air mass will be less, however, that's what the intake air temp correction is for (and also that would mean less fuel not more).If the turbo can't work efficiently then there is a large amount of heat generated and it can't be effective at pressure ratios outside of a certain range.
Basically, you can't just maintain inlet pressure in ever decreasing ambient air pressure (or increasing temperature). Less air requires less fuel.
It's not desirable to fit an enormous turbo that would suit only flat-out at 4000m.
Selecting a turbo would require a choice of whereabouts on the course you required greatest efficiency and would be different to sea level.
....Other words such as Adiabatic and entropy are involved....
the question still stands, given the same absolute MAP pressure and intake temp, why would you need significant correction to increase fuelling with a lowering of Baro?
If E-Map falls, then I can see you may have to increase it, but with the turbo having to work harder, E-map is likely to rise if anything?
motorizer said:
Yep, they should have tested the bike in low oxygen. It was probably fine here in the UK.
I did a road trip in the rockies once, goddamn the car got slow when you got up in them mountains....
I did a rally this year over the Alps in an Alfa, once we were getting some altitude up I was having to really rev it to make any progress. I did a road trip in the rockies once, goddamn the car got slow when you got up in them mountains....
longshot said:
For someone with his image, I imagine pulling birds in the US is like shooting fish in a barrel.
Why would anyone in the US have the first clue who he is, or even where the IoM is?(I was really surprised to see an american-looking chap with a Guy Martin quote t-shirt on in the programme)
Aaaanyway, excellent programme, excellent effort on all parts, think they'll really struggle to top that episode.
Edited by monthefish on Wednesday 5th November 11:32
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