What is the fuel capacity on GTR?

[chiz]

Hello,

I understand the GTR and Can-Am has 2 fuel tanks. What is the total fuel capacity in litres?

Thanks

[Stig]

80 litres.

[chiz]

Hello Stig,

I take it it is 40 litres per tank?

I work this out at 17.6 gallons, and with reports of 10 miles per gallon, a range of 176 miles. Does that sound right?

Not bothered about fuel cost, just driving around north Wales and running out of fuel

There is a Shell station just as you come into Denbigh.

Do you use Optimax in your GTR stig?

Thanks

[Stig]

Yup, 180 miles ish is the range in mine, but others may give better economy.

And yes, I always run Optimax.

[BobM]

Hi Chiz,

I've got a 450bhp AS engine in my GTR and get between 110 and 140 miles per tank, i.e. total range between 220 and 280 miles between fillups, depending on driving.

[davefiddes]

EFI boosts the fuel consumption into the low 20s which pushes out the range somewhat.

At least you don't have to waste your money on high octane fuel like Optimax even for a blown engine. American Speed engines (and most US sourced Chevys) are setup to run on 92 octane gas and don't have variable ignition timing with knock sensors (heck mine doesn't even have vacuum advance!) that could make use of the increased octane rating.

[chiz]

So there is no point in using Optimax (98RON) with a 6.3 534BHP AS engine, will 95RON give exactly the same power/noise?

[Stig]

I use Optimax as my high engine bay temps make pinking more likely.

[davefiddes]

AFAIK, yes it wont make much difference out of the box. If you get the ignition tuned for higher octane jungle juice I'm sure you'll get some more power. The only way to get the full benefit though is to have the engine build with the appropriate cam, compression ratio, etc. This is a bit harder to achieve I suspect as much of the advice on part selection is US biased so will err towards 89-92 octane US street gas or full out 100 octane race gas. American Speed or other US based builders will find it hard to build engines like this...unless we send them regular tankers of Optimax

Your point about higher engine bay temps is a good one Stig.

I've pretty much got or will shortly have the bits I need to build a programmable ignition system as the first step on the way to a fuel injected engine. I'm thinking about getting my beast on a rolling road after it's registered to get a baseline with numbers from AS engine as shipped, tuned stock dizzy setup and programmable ignition. Will report back if I get any interesting results...

[454]

I read somewhere that the Americans use a different Octane rating to us and that their 91 RON was the equivalent of our 95 normal unleaded.
Their 92/93 RON Premium is the equivalent of our 97/98 Super/Optimax type stuff.

Can anyone confirm this ?

I would say that whatever engine you buy it's well worth a few hundred quid to take it to an expert and get it properly set up for our fuel etc. It could save a lot of money in the long run and you might even gain a few ponies

[davefiddes]

You're spot on 454. I'm a dolt and have spouted a lot of nonsense! (not the first time and probably not the last)

The US uses the Anti Knock Index (which is (RON + MON)/2 ) whereas in Europe we tend to see just the RON value quoted. The full details can be found here www.faqs.org/faqs/autos/gasoline-faq/part3/

Rule of thumb seems to be that you add 4-5 to the AKI rating to get the RON rating for modern fuels. So 92 octane would be 96-97 RON (super unleaded) whereas 89 AKI octane would be 93-94 RON (lower than our stock 95 RON unleaded).

Programmable ignition and a session on a dyno to set it up right sounds like a very good idea now...

[james]

I believe that's true. When I was talking about the fuel that I run the Ultima on to Fluxen, it appeared that the RON ratings are different in the UK and US.

Not sure why though.

[davefiddes]

The RON ratings are the same everywhere. It's just that in the US the quoted ratings are an average of two different measures(RON and MON) of fuel quality whereas European petrol stations just quote one measure(RON). Not sure why we do it differently... It may have something to do with European engines being high revving lighter loaded in general compared with low revving highly loaded US engines (RON is an indication of knock under low load whereas MON is an indication of knock under high load).

Just read the rest of FAQ. Seems that too low an octane fuel can also cause runon in carb'd cars. My engine running on std unleaded has run on for a few seconds when hot once or twice.

[Ultimapaul]

A small point on tank capacity. Although 40l per side, it is not possilble to get every last drop out. So, when working out your MPG you'd need to note what amount you put in when filling up. I've never got close to 80l. 70 at best (worst)

Paul

[andycanam]

I filled my tanks, then pumped them dry and re-filled (to calibrate the STACK dash).... and I got in precisely 73 litres of fuel.

I also run my car only on Optimax as I think she's worth it....... after all do you buy your missus cheap plonk for that special night or expensive chardonney?

Clive don't answer that!

[jschwartz]

If you guys ever set your carbs up right you'll get low 20's mpg on the highway as well.
jeff

[BobM]

jschwartz said:

If you guys ever set your carbs up right you'll get low 20's mpg on the highway as well.

Don't forget Jeff that 20 mpg for you is 16.6 mpg for us (US Gallon = 0.83 UK Gallons).

[Alan 2]

I think you've got it the wrong way round. 20mpg US is 24mpg UK.

[BobM]

Alan 2 said:

I think you've got it the wrong way round. 20mpg US is 24mpg UK.

You're right ... must've left quite a few brain cells behind on my weekend away

[Ultimapaul]

jschwartz said:

If you guys ever set your carbs up right you'll get low 20's mpg on the highway as well. jeff

Ah dear, sorry mate, best post I've seen in ages!

Paul 20 odd to a gallon