Board logo

HELP!!! Using too much fuel
spoonana - 26/12/14 at 11:36 AM

Hi all,

Hope you all had a good xmas.

I've been having some problems with the engine in my Tiger CAT E1. It has a 2.0 pinto 205 block with injection head mounted to twin 40 Dellorto carbs.
The problem we have discovered is that we seem to be burning fuel at a mile a litre. This seems rather unusual. Is our engine doing something wrong?

Many thanks

Max

Sam_68 - 26/12/14 at 12:09 PM

Really a mile per litre (ie. 4.5 miles per gallon)? On the road?

If so, then yes, your engine is doing something wrong. I'm surprised its even running if its it's overfuelling by that much.

Carburettors are ludicrously inefficient compared to modern fuel injection, but in brisk road use you should be getting upper teens mpg from a Pinto, even if it's in quite a high state of tune (though you probably won't see much better than high 20's mpg from twin carbs., no matter what you do or how you drive).

If it's as bad as you suggest, the carbs need setting up by someone who knows what they're doing.

Paul Turner - 26/12/14 at 12:10 PM

4 1/2 mpg, there is something seriously wrong.

If it is using that much fuel the probability is the engine is not burning it. Probably just washing down to bores and into the sump which will wear the bores fast and dilute the oil to the point of having no lubricating properties.

You really need to get the carbs set up and timing checked. If you give us a clue where you live someone will know qa good local specialist.

spoonana - 26/12/14 at 12:21 PM

I live in Chertsey in Surrey. What would be the cost/complexity of converting over to fuel injection and what sort of mpg could I expect as a result?

[Edited on 26/12/14 by spoonana]

Macbeast - 26/12/14 at 12:27 PM

An injection head mated to carbs ? Sounds odd.

ragindave - 26/12/14 at 12:33 PM

Fit bike carbs should return 25 mpg plus

Paul Turner - 26/12/14 at 01:18 PM

quote:
Originally posted by ragindave
Fit bike carbs should return 25 mpg plus


The OP already had Dellortos, the problem is are they any good or are they simply not set up. Putting bike carbs on the engine that are not set up would be simply throwing money away.

Many years ago I had a 1700 X-Flow with twin 40's, about 130 bhp. On average it did about 25 mpg but on a run it would manage nearer 30 mpg. If the OP's Pinto is in a sensible state of tune and in good health I would be expecting similar economy.

Better to spend money on sorting what he has (presuming they are not knackered). Nothing whatsoever wrong with properly set up Dellortos and Webers.

gremlin1234 - 26/12/14 at 01:34 PM

what fuel pump / pressure are you using, - carbs need very little fuel pressure,

ianm67 - 26/12/14 at 01:48 PM

If it's running that rich you'd have significant clouds of unburnt fuel from the exhaust, it would run like a pig, have poor throttle response and you'd smell that it was overfuelled. Are you sure that you haven't got a fuel leak? If it's at the rear of the car it would be easy to miss it when on the move......

ianm67 - 26/12/14 at 01:52 PM

quote:
Originally posted by Macbeast
An injection head mated to carbs ? Sounds odd.


Why....? The Pinto injection head has bigger valves and better porting so they flow than the carb'd head. Other than that they are pretty much identical. If I remember correctly the injection cam also has slightly more overlap than the carb version. A nice, 'plug and play' upgrade for a Pinto.......

rusty nuts - 26/12/14 at 02:43 PM

Has it ever returned decent fuel consumption ? Have you checked the spark plugs for rich running? If so are all the plugs showing a rich mixture? Have you checked the basics like valve clearances (tight clearances will cause high consumption) , ignition advance , air filter , engine running temperature etc ? Carbs should be the last thing to check/adjust when trying to sort out engine running problems. Have you got the cold start(choke) cable connected and adjusted correctly? Have the carbs ever been set up to suit your engine? Have you checked the fuel pressure, high pressure will cause flooding. Have the carbs been tightened onto the manifold correctly, over tightening will cause problems . If all of these are ok then it might be worth stripping and cleaning the carbs, fitting new needle valves , setting float height , balancing etc

mcerd1 - 27/12/14 at 01:31 PM

quote:
Originally posted by ianm67
quote:
Originally posted by Macbeast
An injection head mated to carbs ? Sounds odd.


Why....? The Pinto injection head has bigger valves and better porting so they flow than the carb'd head. Other than that they are pretty much identical. If I remember correctly the injection cam also has slightly more overlap than the carb version. A nice, 'plug and play' upgrade for a Pinto.......

the valves are the same as the carb'd heads, but the port shapes are significantly better as standard (pinto's have bad port shapes that are actually too big!) and some injection ones have hardened valve seats from new...
if your getting the head ported its of no advantage over the carb'd head, but its worth around 10bhp if your comparing stock heads


as for the fuel economy problem - you'll need to check all the basics as above, its often something really simple and easy to sort.

I'd start with air and fuel leaks - sounds stupid but the last time I had an issue like this it was actually a split fuel line...

whitestu - 27/12/14 at 06:19 PM

Properly set up carbs are very nearly as good as injection. Well set up carbs are better than badly set up injection. You'll never get much out of a Pinto but 20-25mpg should be achievable on a good condition, well set-up engine.