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peterd

Fuel Economy

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I've got a 4k block/5k head motor in my ke35 attached to a trimatic. I had the carby rejetted a while back. I can't remember but I think the jets are one size larger than standard. As a city car, it goes great but it's a bit thirsty. I get about 12L per 100k. Obviously the larger jets use more fuel but I wondered if there's a fuel leak too. The carby seems OK, I've just had the fuel pump apart and that seems OK. Where else should I be looking? There's nothing obvious. Thank heaps.

Edited by peterd
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I remember altezza saying that the autos are about 8l per 100. It's quite likely just what happens when you rejet the Aisan carby.

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...and city driving is always worse, whereas I do most of my driving on trips. That 8L/100 would be at 100kph out in the country, down to 7.3 or so with a manual box.

 

12 is pretty thirsty. If you can find stock jets just replace the first throat and see how it goes, that's the one you drive on most of the time I reckon. If you get stuck, PM me as I'm sure there are carbs lying around the Woolshed with jets in, but I'm sure there's some in Perth.

 

You'd see any leaks except the pump leaking into the sump, so I doubt its a leak now. What's the chance of getting a mixture meter up the exhaust and just checking how rich it is?? Some friendly local mech with one that you can take a zip around the block with..

 

The other question would be compression.. Can you run a compression meter over all 4 cyls and see what they are. I'm just wondering which 5K head it is and if the compression is up at 9.5 to one, which should give 150psi. If you have low compression that would make it inefficient.

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I've got a couple of old carbies so I might try swapping just one jet. I tried swapping the whole carby but it went like a dog with my foot flat to the floor. From memory, the 5k head makes about 13;1 and last time I checked the compression, the cylinders were about 155.

The carbies ive got are all slightly different. Is there a difference with 3k/4k/5k carbies or are they the same?

I had the fuel pump apart and the diaphragm looked fine.

Edited by peterd
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OK, so compression is good, it should go like a rocket. I don't know what differences there are in the carbs, but I'm sure they didn't stay exactly the same for 15years.

 

You might find the jets have numbers stamped on them, but as they were never designed to be changed Aisin might not have bothered. In that case it would be good to find different small wires from electrical cables and a pair of verniers to measure the diameters of the jet holes.

 

In the end the numbers don't really matter, you just need to get it performing at its best.

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I found I had an exhaust manifold leak from around a bolt holding the extractors on. I think I'm meant to cut the washer in half to make it fit. For now, I've plugged the hole with gasket cement. Apart from running better when it's cold, the fuel consumption dropped from 12L/100km to 9.5L/100. I thought that was quite significant for such a minor leak.

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That is a big improvement!

 

Sounds like its worth pulling the manifolds off and fitting a one-piece gasket instead of the factory-style two piece. Take the opportunity to check all the holes for dirt and bad threads, clean up the bolts, measure the manifold thicknesses and sort out the half washers.

 

Watch for where nuts do up on the sholder of the welds of the extractors too, they're not that good a quality in manufacture.

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I having the same problems with my 2007 Toyota Corolla LE. Lately, i have been seriously thinking of ordering the cold air intake I saw in 4 Wheel Online. The brand is K&N.

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I run one to get fresh ambient air into the carbs rather than warm air that has been through the radiaitor and heated up. That's only because I can't run the stock cold air inlet on the KE70, but you should be able to if it is all factory still..

 

Mine pressurised the airbox and leaned out the rear cylinders until I put a vent valve on it that opens under 100kph pressure and closes when going slow. Its in "The Girls KE70"

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I having the same problems with my 2007 Toyota Corolla LE. Lately, i have been seriously thinking of ordering the cold air intake I saw in 4 Wheel Online. The brand is K&N.

 

Something wrong with your car if you are getting bad fuel economy in a 2007. A cold air intake wont help.

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How bad is the fuel usage??

 

The Girls KE70 with its 4AGE just did 6.7L/100km Walcha to Orange, while the Hoonicorn with its 4K did 7.3 last month on the same trip. Its about 600km fill to fill. That's pleasant 100kph driving through mountains for most the distance, then a boring run up the New England Highway for about 1/3 of it.

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Something wrong with your car if you are getting bad fuel economy in a 2007. A cold air intake wont help.

 

I've always thought that a cold air intake can improve a vehicle's fuel economy. Thanks for the input.

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The fuel economy in my kluger went bad. A new air filter and a good clean of the mass air flow sensor fixed it.

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I've always thought that a cold air intake can improve a vehicle's fuel economy.

 

It might.. The manufacturers usually have cold air intakes fitted, like the KE70, but these are not performance orientated. So an aftermarket one might have less drag in the filter setup and allow more air through, or not have the bends that allow designers to fit it in an odd place, or not have the quietening design to keep noise down.. Certainly the colder the air the denser, so the more that can be crammed into the cylinders.

 

The cold air part is mostly in slow/stationary traffic as a 100kph wind going in under the bonnet evens the temperature out quite quickly.

 

Its over 30deg outside today, and there's nothing a cold air intake can do about that!

 

Vaguely on this topic, does anyone have an idea of electric fan wind speeds?? At what speed does the car overtake the fan air?? I figure the electric fan only does something useful when stopped or crawling along slowly, and once you're doing 50kph the car's motion cools the rad. From some speed upwards the fan is just adding drag to the air going through the radiator, and the shroud just gets in the way & makes the rad less efficient.

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