PDA

View Full Version : Mpg



tommy_gixer
11-05-16, 06:53 PM
Hi everyone, this has no doubt already been discussed but what kind of mpg could I expect to get from a cobra kit , 350 chevy approx, and roughly 350 -400bhp with a 5 speed box ? I know this is hard to answer but just a rough idea will do 😊. Thanks

Roger Shackleton
11-05-16, 07:03 PM
On my 383 with carb I get 16.3 mixed spirited driving on a long run may be 18/19

Rog

tommy_gixer
11-05-16, 07:53 PM
That's not as bad as I thought roger, what size tank does your ak have? what's the range on a run ?

westborne
11-05-16, 08:03 PM
Bog standard 350 with carb. About 18 on a decent run

david hemmings
11-05-16, 08:37 PM
21.8 average on the trip to stonleigh cruising at 70/80 all the way ( last 120 miles was on 7 cylinders though) 3.54 dif chevy 350. I was pleasantly surprised

Happy Jim
11-05-16, 08:52 PM
LS1, 6 Speed box, Best 32Mpg, good run 25Mpg, normal hooning 18Mpg, track 8Mpg.

Jim

nealgs
11-05-16, 08:52 PM
383 on carbs - averaged 22 to Le-Mans, with a best of 24-26MPG on same journey, not bad at all :)

nuf_said
11-05-16, 09:16 PM
383 with carbs. Did surprisingly good 19mpg to Stoneleigh and back at a steady 70mph each way. Had to put my two cans into the tank on the way back, since my gauge seemed to suddenly jump from 1/3 full to E instantly. So range not too good.

Daren't work it out for round town....

I'm jealous of nealgs getting mid 20s (think I'm due a tune up) and the LS ones getting more.

My previous chevrolet 5 litre (305) did about 8 round town and 12 mpg on a run - also had no power at normal revs either. It had to go. Sold it in bits.

Nuf Said

Neil O
11-05-16, 10:08 PM
462ci Fe Sideoiler, never more than 13mpg
351ci Cleveland, 17-19mpg max.

AKBaz
12-05-16, 12:43 AM
390 FE just over 16 mpg, mostly Motorway cruising at 70mph. And I am happy with that.

Barry

kdavies3
12-05-16, 07:26 AM
445 FE with 850 DP Holley about 17mpg on a run.

tommy_gixer
12-05-16, 07:55 AM
Thanks for everyone's replies,

There seems to be quite a variety of readings depending on spec and tune up. What is the capcity of and ak/dax/SRv8 fuel tank then ?

TINKA
12-05-16, 08:13 AM
Not 100% sure but think AK's is about 12/13 gallons and Dax is very similar.

hifihedgehog
12-05-16, 08:40 AM
383 sbc, 19mpg cruising with 650 edelbrock carb. switched to Holley double pumper and out the box or was a miserable 12mpg but with a few easy tweaks I'm now getting 17/18 mpg so they are not as bad as their reputation! The primary side of the carb is no different to a vac sec so if you stay out of the secondaries and avoid activating the secondary pump squirt then there's no reason you can't get good mileage, as I have found. Bloody difficult not to floor it at every opportunity though!

I copied a dax de dion tank but made it slightly wider to squeeze a few more litres, from external measurements IIRC the internal volume is about 77 litres. That gives me a realistic range of about 280 miles as the fuel gauge isnt entirely truthful below 1/4

Dave A

psh
12-05-16, 10:11 AM
6.3 Chevvy V8 with 5 speed Getrag, Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel.

My AK has a 12 gallon fuel tank.

On a run sticking to speed limit , but including a few “mad “ moments, using “A” roads from Rugby to the Peak district with a passenger , I averaged 27 mpg, but blasting up to Peterborough and back ,doing between 70- 90 mph on the motorway . I averaged 19 mpg, and pleased with both figures .

hifihedgehog
12-05-16, 10:30 AM
loads more people than I thought with 383's around here!

Roger Shackleton
12-05-16, 11:04 AM
Down hill out of gear with the wind behind you! Either that or you need a new calculator ! LOL

Rog


6.3 Chevvy V8 with 5 speed Getrag, Holley 670cfm 4 barrel street Avenger Carb, 450 BHP at flywheel.

My AK has a 12 gallon fuel tank.

On a run sticking to speed limit , but including a few “mad “ moments, using “A” roads from Rugby to the Peak district with a passenger , I averaged 27 mpg, but blasting up to Peterborough and back ,doing between 70- 90 mph on the motorway . I averaged 19 mpg, and pleased with both figures .

hifihedgehog
12-05-16, 11:24 AM
Paul your "blasting" sounds like my cruising! I'll echo Roger, I'd be deeply, deeply suspicious of 27mpg!

psh
12-05-16, 11:27 AM
Down hill out of gear with the wind behind you! Either that or you need a new calculator ! LOL

Rog

Nothing wrong with my calculations Roger :D . As I said I was sticking to the speed limits on the A and B roads , and as the wife was I in the car , I took it quite steady and only did a bit of over taking . That figure was worked out on the journey up only, and did not include all the running about in the Peak District. On the motor way i wasn't being heavy footed, just cruising .

psh
12-05-16, 11:42 AM
Paul your "blasting" sounds like my cruising! I'll echo Roger, I'd be deeply, deeply suspicious of 27mpg!

I do welly it when i am on my own, but granted i don't hammer it every where, but my figures are not that much different from Jim's or Nealgs figures !

marlin444
12-05-16, 12:49 PM
SVRV8 351w = 386HP When I got it. Lots of work done so not sure of HP now 10gal tank. As much as 15mpg as low as 7mph ouch. Paul

dobbo1969
12-05-16, 03:08 PM
Not sure of MPG as not actually on the road but put 25 litres in for test (told should have filled it completely) but fuel gauge showing 1/4 at start of test and empty when finished. Only running for say an hour not very hopeful for good figures when it comes to fuel consumption

nealgs
12-05-16, 04:09 PM
decent MPG = LS3 or Lexus engine i'd say, but that ain't what a cobra is about ;)

neilcatele
12-05-16, 04:55 PM
With the cruse control set to 80 mph Calais to Reims yesterday we got 23.8 mpg. That's with roof on in the rain and 2 people and 2 weeks of luggage.

hifihedgehog
12-05-16, 05:23 PM
I do welly it when i am on my own, but granted i don't hammer it every where, but my figures are not that much different from Jim's or Nealgs figures !

fair play to you if that figure is genuine, you'll forgive us for being skeptical though I hope! If you did manage 27mpg all I can say is 'kin hell that must have been boring

nuf_said
12-05-16, 07:28 PM
My cousin put a gallon in the tank when he fired up his cobra for the first time. He thought it sounded great and went in the house to fetch his wife, but when he came back it had stopped. After lots of checking - he had run out of petrol.

A chum with a Harley D bike told me he gets better mpg when he tows it on a trailer behind his camper van.

We shouldn't worry too much. Lots of smiles per gallon.

Nuf Said

psh
13-05-16, 09:36 AM
fair play to you if that figure is genuine, you'll forgive us for being skeptical though I hope! If you did manage 27mpg all I can say is 'kin hell that must have been boring

That’s the one and only time I have ever managed that sort of economy in the cobra, not come anywhere near since to be honest , as I tend to drive it like they are supposed to be driven on my own or with mates ,and as previously said, I agree that our cobras are not about economy .

And yes it was a frustrating drive at times keeping to the limit and missing loads of opportunities to blast past people :rolleyes:, and although my wife likes the cobra, she does not like excessive speed or noise and only agreed to do the weekend away to the Peaks, as long as I didn’t give her a heart attack :rolleyes:

One thing I would like to fix on my cobra is the “do what it likes fuel gauge ”, its fine when its full, but once down to under half , one minute its reading empty ,then back up to half :lol: any one got an easy fix for this ?

KevinW
13-05-16, 11:00 AM
One thing I would like to fix on my cobra is the “do what it likes fuel gauge ”, its fine when its full, but once down to under half , one minute its reading empty ,then back up to half :lol: any one got an easy fix for this ?

- you could try this:

https://www.spiyda.com/magento/index.php/vehicle-electronics/fuel-gauge-electronics.html

TINKA
13-05-16, 12:41 PM
- you could try this:

https://www.spiyda.com/magento/index.php/vehicle-electronics/fuel-gauge-electronics.html

Just fitted one of these and think they are great.

GUMBALL
13-05-16, 01:52 PM
Me too, (after reading your thread) along with a VDO tube sender.

leochas232
13-05-16, 07:50 PM
I have an LS3 in mine and although I've not measured it exactly, I'm getting about 18MPG.
decent MPG = LS3 or Lexus engine i'd say, but that ain't what a cobra is about ;)

nealgs
13-05-16, 09:05 PM
ok, maybe just the Lexus engine then for decent MPG :) - lol

TFatC
15-05-16, 12:08 AM
Chevrolet 427 with 4 barrel Holly carb. Best ever a steady run to Le Mans - 17mpg. Out for a spirited drive over the mountain roads, 6mpg. 10 gallon fuel tank.

Filling up for the third time in a morning at the same garage is embarrassing! :-)

Commando
15-05-16, 10:52 PM
7/8 MPG with a ford 5.7 Cleveland 351 .................15 MPG , When Boys in Blue about!

psh
16-05-16, 10:11 AM
- you could try this:

https://www.spiyda.com/magento/index.php/vehicle-electronics/fuel-gauge-electronics.html

Hi Kevin, just tried sending you a PM,but your inbox is full.

Paul.

Delfim
16-05-16, 02:02 PM
I have a chevy 350, 4 speed box and electric overdrive on a 3:31 diff.
With a full tank, +- 45 litres, gives me 2 hours drive on a highway (sea level) at max 140 kms/h.
I have no idea if that is good or not for a cobra. I know that is no good on any of my other cars.
But I never built the cobra with fuel economy in mind.
Did anybody?
Cobras are very thirsty and I never drive "normaly" with the cobra.
Mine is not used on a daily basis, unlike a lot of cobra owners, so now and then I can afford to splash a bit.

Highlander
16-05-16, 03:31 PM
I have a chevy 350, 4 speed box and electric overdrive on a 3:31 diff.
With a full tank, +- 45 litres, gives me 2 hours drive on a highway (sea level) at max 140 kms/h.
I have no idea if that is good or not for a cobra. I know that is no good on any of my other cars.
But I never built the cobra with fuel economy in mind.
Did anybody?
Cobras are very thirsty and I never drive "normaly" with the cobra.

Mine is not used on a daily basis, unlike a lot of cobra owners, so now and then I can afford to splash a bit.


That's about 17 miles to the gallon, so no different to most apart from the speed you suggest is approx 84mph and not the 60 ish mph that most of us have to stick to in the UK.
No idea what mine will do with the Lexus engine.......time will tell!!

Delfim
16-05-16, 07:01 PM
That's about 17 miles to the gallon, so no different to most apart from the speed you suggest is approx 84mph and not the 60 ish mph that most of us have to stick to in the UK.
No idea what mine will do with the Lexus engine.......time will tell!!

Fortunatly, here in Portugal, although the speed limit on a higway is 120 km/h, the police here do not use the excess of 20km/h as an excuse to fine motorists.
Legaly this practice is not acceptable here (overspeeding) but unlike the UK, the Police in this country is not a business. Here they have better and more important things to do.

I remember when I lived in South Africa, way back in the 90´s it was the same situation: It was nothing but a business.
Maybe your opinion is not the same as ours here, but then you don´t live here.
When I go to the UK, I´ll remember this post and will comply.

KevinW
16-05-16, 07:26 PM
Hi Kevin, just tried sending you a PM,but your inbox is full.

Paul.

Inbox now cleared - sorry!

Dave S
23-05-16, 04:53 PM
Being in the US leads me to ask; when reporting MPG, you're basing it on Imperial Gallons, right? Our US Gallon is about 0.8 Imperial Gallons.

TonyD
23-05-16, 07:15 PM
That's about 17 miles to the gallon, so no different to most apart from the speed you suggest is approx 84mph and not the 60 ish mph that most of us have to stick to in the UK.
No idea what mine will do with the Lexus engine.......time will tell!!

With an auto box and a 3.54 diff in Tims Lexus Cobra cruising at 80mph we wrere getting just a tad over 25mpg which we felt was a tiny bit disappointing. The Beemer engined would have been getting nigh on 30 mpg ( 35mpg at a steady 70mph) as it had a 5 speed box with a 3.31 diff. We swapped the 3.54 out to a 3.08 in the Lexus and the cruising is even more relaxed however have not checked mpg as yet but do expect a significant improvement. With a manual box behind the Lexus you should be getting better mpg than auto anyway so at cruise I would expect you to get the high 20's.

Cheers,

Tony

Highlander
24-05-16, 09:40 AM
With an auto box and a 3.54 diff in Tims Lexus Cobra cruising at 80mph we wrere getting just a tad over 25mpg which we felt was a tiny bit disappointing. The Beemer engined would have been getting nigh on 30 mpg ( 35mpg at a steady 70mph) as it had a 5 speed box with a 3.31 diff. We swapped the 3.54 out to a 3.08 in the Lexus and the cruising is even more relaxed however have not checked mpg as yet but do expect a significant improvement. With a manual box behind the Lexus you should be getting better mpg than auto anyway so at cruise I would expect you to get the high 20's.

Cheers,

Tony

I have a 3:27 ratio diff with the Getrag box. Mine has always been built as a bit of a cruiser for the longer runs that I hope to be doing on the roads up here.

Cheers.

Paul.

TonyD
24-05-16, 10:13 AM
I have a 3:27 ratio diff with the Getrag box. Mine has always been built as a bit of a cruiser for the longer runs that I hope to be doing on the roads up here.

Cheers.

Paul.

I think you'll find that diff ratio damn near perfect.

Cheers,

Tony

Davidg
24-05-16, 04:09 PM
+25 mpg in my Lexus lump with the manual box, that was more of an 'A' road cruise over around 100 miles, so mix of driving through villages and open roads around Arundel. Didn't really manage to get it in 5th Gear very much to be honest so on the motorway high 30's ought to be possible at cruising speeds and 5th gear. Must be related to some degree to weight. How much do other peoples cars weigh out of interest ?

Davidg
24-05-16, 04:28 PM
Sorry high 20's on the motorway that should have read ! Apologies

hifihedgehog
25-05-16, 09:41 AM
+25 mpg in my Lexus lump with the manual box, that was more of an 'A' road cruise over around 100 miles, so mix of driving through villages and open roads around Arundel. Didn't really manage to get it in 5th Gear very much to be honest so on the motorway high 30's ought to be possible at cruising speeds and 5th gear. Must be related to some degree to weight. How much do other peoples cars weigh out of interest ?

Cobra weight as a topic that interests me too. Seems to be fair bit of variation with engine choice etc. My car is completely devoid of all blingy bits. No bumpers, overrider thingies, no roll hoops etc. and at IVA mine weighed in at 1120kg full wet which to be honest is a bit more than I had hoped for but seems fairly average for Dax de dion with SBC. According to the oracle that is Dave Brookes his typical Dax build was about 1130kg. He's made quite a few so probably a good sample size for a reliable average figure.

I weigh 68kg :p so total weight is under 1200. I have thought about trying to get the weight of the car down further, the Dax door hinges are a good start for an easy couple of kg!

Some ali engined GD's and Rams are down at around 1050kg or maybe even lower than that

Seems to be a wide variety of driving style and typical usage by what people have described. Personally, 80% of my cobra driving is blasting around on back roads. I don't often chug along at a constant 60-70mph on a long trip.

Davidg
25-05-16, 10:21 AM
Mine is 1064 kgs with no one in it, with tonneau cover on and hood in boot. I guess it benefits from the alloy engine. Mine has no bling either.