|
|||||||||||
|
|||||||||||
27 Sep 2010, 08:23 (Ref:2765300) | #1 | |
Rookie
Join Date: Jan 2010
Posts: 81
|
Complete novice question - sorry!
Hi,
I have raced my Lenham for the last few months without knowing how much fuel to fill it with. I have been running on 3/4's full at all circuits, knowing full well that I am probably carrying too much. I measured my tank over the weekend and found that is is 20 litres when full. My question is, what average MPG (a range would be better than nothing!) do you think I am getting so that I can adjust the fuel load? I have a Peter May 1298 A series with twin 1 1/2 inch SU's. The car weighs about 780kg. As I said, any idea is better than me guessing at the moment...! Thanks in advance for any help, Ian. |
|
|
27 Sep 2010, 09:14 (Ref:2765326) | #2 | ||
Race Official
Veteran
Join Date: Mar 2003
Posts: 13,203
|
Ian, no need to apologise; seems a perfectly reasonable question. Hope you get some equally reasonable replies. With hindsight, I guess that if you had recorded roughly how much fuel you had been carrying at each event, how long the race was and how much you had left at the end you would have come up with a rough estimate, although it would probably vary a bit at each circuit depending on the circuit's characteristics. It may be the way to go for next season if your racing season has already ended, if nothing better appears here!
|
||
|
27 Sep 2010, 09:26 (Ref:2765339) | #3 | ||
The Honourable Mallett
20KPINAL
Join Date: Feb 1999
Posts: 37,282
|
I find that it can vary, however if you know the vloume of fuel at the start of practice, count the number of laps you do then measure it afterwards, you can determine the consumption. Its what I do and I know many others do so too.
Bare in mind you aren't going to lose three tenths to the next bloke due to fuel weight. |
||
__________________
I've decided to stop reaching out to people. I'm just going to contact them instead. |
27 Sep 2010, 11:04 (Ref:2765385) | #4 | ||
Veteran
Join Date: Jun 2009
Posts: 4,025
|
Fairly difficult to hazard a guess - it can vary dramatically - our Porsche probably does 8 - 10 mpg at racing speeds, tho we usually aim to have up to 1/4 of a tank left at the end of the race - as this can show as empty at various parts of a circuit and I prefer to have one less thing to worry about...
I'd surmise that you'd probably be getting around 15 mpg at a worst case...but as said its really just down to doing an accurate assessment by for one race putting in a known amount (on the generous side) then pumping out what remains at the end of the race and measuring it.....and of course not worrying too much about it as an extra gallon or so isn't going to kill your lap times |
||
__________________
Richard Murtha: You don't stop racing because you are too old, you get old when you stop racing! But its looking increasingly likely that I've stopped.....have to go back to rallying ;) |
27 Sep 2010, 11:34 (Ref:2765406) | #5 | |
Veteran
Join Date: Jul 2005
Posts: 1,981
|
Another way is to estimate using your known engine BHP and running time.
For 100 BHP you will use about 31 litres of fuel per hour, running at peak revs with a wide open throttle - you won't use any more than that unless the air/fuel ratio is very wrong. So you should be able to work out the maximum you would need if you are going to a new circuit - a 15 minute race with a 100 BHP engine would need 7.75 litres maximum for the race, plus a bit more for getting from the paddock onto the grid, the slowing down lap and for getting back to the paddock. Once in the ballpark you can measure how much you have left in the tank after you are back in the paddock to find out the true consumption. Then make a note for the next time you are at the same circuit. |
|
|
27 Sep 2010, 11:45 (Ref:2765421) | #6 | |
Rookie
Join Date: Jan 2010
Posts: 81
|
Thanks all. I have plenty of ideas now, and I should have really made better notes at the circuits I visited this year! There was so much to learn and take in during the first year that something like fuel usage took a back seat..
|
|
|
27 Sep 2010, 11:55 (Ref:2765428) | #7 | |
Veteran
Join Date: Jun 2007
Posts: 1,685
|
Some guys are quite obsessive about weight and I know one chap who drains the fuel after every qual/race and then puts a known measure back in, all to save the risk of carrying an extra kilo or two which in a touring car seems a bit of overkill. My own car varies a fair bit from race to race, eg at Spa it uses less per mile than at Cadwell where you're doing a lot more braking and accelerating.Not that I've ever measured it, all done by intuition and never been caught out except for the time the car wouldn't start when I went to unload it after a meeting, perfectly judged
|
|
__________________
Semper ubi sub ubi |
27 Sep 2010, 17:45 (Ref:2765625) | #8 | ||
Subscriber
Veteran
Join Date: Oct 2007
Posts: 8,710
|
Should be no need to guess Ian. These days when you can look at all your lap times and how long you raced when you get home.Fill the tank before the race or qualafing then refill afterwards that will tell you how much you have used then look at your distance covered in race plus a bit for warm up lap and then its job done.
I will say this when i took my racing a bit more serios than i do now in the early 80,s i had an engine builder build my engines and we would split the prize money. He was obsessed with working out the fuel we would need.needless to say the first race i was stolling away in the lead untill last lap and we ran out. |
||
|
27 Sep 2010, 20:08 (Ref:2765708) | #9 | ||
Racer
Join Date: Aug 2003
Posts: 386
|
Ian's suggestion is what I do...now..
You can be too obsessive about it. As its my first season I thought there was a really scientific way of doing it and thought 'I'll be reeeally clever and professional, like!" My car is a bit overweight like for like so I have looked for an edge, rather than listening to advice given to me (that being what Ian has suggested above!). Consequently I have 'calculated' my fuel load based on 'known' fuel consumption and had to be towed in twice (on my in laps luckily, once at the end of a race and once at the end of qually)....this season alone!?!! Given up on being too clever. We are talking old cars. No common rails in sight! The variability is huge track to track so base it on what you've actually used (handy if you've had a test day before, otherwise you just have to make sure you've got enough for qually and use that as the measurement for the race) Race notes as soon as you get home are very important for fuel usage (as long as you don't soup your engine up in the close season, then its start again time!) and Mike (my co-driver and esteemed MG man) has drummed this into me. Anyway, from now on I'll avoid pies, forget the weight of the extra fuel and make sure I've got "one or two extra litres"! Last edited by skentellytubby; 27 Sep 2010 at 20:15. |
||
|
27 Sep 2010, 20:16 (Ref:2765712) | #10 | ||
Veteran
Join Date: Jul 2003
Posts: 6,786
|
With our 1380 FISC cars we used to run about 3/4 full for a 30 minute race and never suffered surge. That was using the larger "1500" Midget tank mind you, which measures over 6 gallons so we were putting in 4 gallons-ish. Which tank are you running?
Of course, we never had the grip to suffer from surge too badly. 100 km at Nordchleife was touch and go, we brimmed to the top of the filler neck ;-) I reckon you're OK at 3/4 full, especially if you're only running the small tank. |
||
__________________
Midgetman - known as Max Tyler to the world. MaxAttaq! |
28 Sep 2010, 11:57 (Ref:2766009) | #11 | ||
Veteran
Join Date: Nov 2006
Posts: 9,410
|
We had this not long ago http://tentenths.com/forum/showthread.php?t=123850
|
||
__________________
Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
29 Sep 2010, 22:23 (Ref:2766900) | #12 | ||
Veteran
Join Date: Aug 2008
Posts: 606
|
Agree with Delta... in my wealth of 5 race experience. Just don't runout on the warm down as it could be embarrassing, eh Skells?
|
||
__________________
I am surpised anything this much fun is firstly still legal and secondly is not taxable |
30 Sep 2010, 16:09 (Ref:2767256) | #13 | |
Rookie
Join Date: Oct 2009
Posts: 13
|
Fuel Consumption
We work on 35 litres per hour on a 1460 modsport Midget with around 130 / 140 BHP 540 kilo and big slicks. Lots left if it's wet!
|
|
|
30 Sep 2010, 18:41 (Ref:2767355) | #14 | ||
Racer
Join Date: Aug 2003
Posts: 386
|
|||
|
30 Sep 2010, 18:45 (Ref:2767357) | #15 | ||
Race Official
Veteran
Join Date: May 2003
Posts: 11,141
|
|||
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
several question from novice | rickybobby | Racers Forum | 1 | 12 Mar 2007 22:17 |
question from novice | rickybobby | NASCAR & Stock Car Racing | 5 | 9 Jan 2007 19:29 |
Rule books at the ready: Question regarding novice black and yellow square | Draven | Racers Forum | 3 | 22 Mar 2006 09:03 |
Complete novice | Mickje | Track Day Forum | 11 | 13 Nov 2002 23:56 |
Novice Cross question | Dom | Racers Forum | 12 | 18 Aug 2001 09:55 |