Fuel consumption on a modified rev3 tubby...

[RyanRs]

I was just wondering how much the MPG would be effected 'in normal sensible driving' when tuning the engine?

I am currently running 376bhp/308lbft fly on my 2.2 stroker build, its still using the 540's and std pump/regulator until it gets upgraded, but being controlled by a Linkplus G3,tuned by Ryan.g. Now i understand that the car will be a lot more juicy under heavy boost than that of a stock tubby, but what about off boost? would the car also be juicier here? or should it be more or less un effected?

The reason i ask this is because i put £15 of v-power in it from empty @ about £1.11 p/ltr, it got me 1/4 of a tank. which under normal driving (50/50 town/motorway) i got about 55~60 miles before the fuel light came back on. the car is tuned for upto 18psi, and i wasnt really going over 6~8psi while on the motorway. obv some boosting is inevitable.

Now, im thinking this fuel usage is quite bad?! considering my escort 1.8 gti will get 95~105miles to £15 of 95ron @ £1.06 p/ltr. (which i still consider bad!)

I do however have the fuel tank vented to atmosphere via a long open pipe that runs to the boot, where vapors are sucked out by the BMIC fans. I know venting to atmosphere does cause poor fuel comsumption, but to what extent?

Can anyone shed some light?

thanx
Ryan

[Turbocarl]

My fuel light comes on when there,s anywhere between 7 and 13 litres still in tank so you can,t really judge your mileage based on those figures - the only true way to find out would be to brim fill her run her say 250 miles then what you can put back into the tank gives you an accurate mpg. I know one fella running pretty similar set up to you and similar mapping greatly improved his mpg over standard if that helps?

[Marf]

50-60 miles to a quarter of a tank is pretty much the same as I get on my Rev3 tubby with exhaust, downpipe and ARC airbox.

I tend to get 230-240 miles to a tank, or if I do a stint on the motorway 260-300, depending on how much squirt I give it.

[cantfindausername]

You want to fill up to the brim, reset the counter, run it till empty, and then fill back up to the brim again. This will tell you exactely how many liters you've used for the miles you've done. Divide liters by 4.54 to get gallons, then you can work out your MPG. I manages 22 cruising at 70 and 17 giving it a bit of stick on the motorway and cruising at 80-90.

[Martin F]

Cruising I'm finding her still heavier on juice then a normal bolt on mods tubby but on acceleration running just 0.8 bar i am literally watching the fuel level go down, 15 mpg, not looking forward to running in excess of 500 bhp

Thats on 800cc injectors Btw.

[RyanRs]

*dont know what happened here :S*

[^Trickster^]

I get 30mpg when driving normally with 470hp tuned on 1000cc injectors etc

Put my foot down and its a different story but still not so bad

Gaeme

[RyanRs]

Well the only problem with the 'fill the tank' method, is i know i would not be able to control my right foot knowing i have 60 odd litres of fuel at my disposal!!

But i suppose if i want to find out if the car is using fuel badly then i guess its the only way.

Marty, how much power are you running at the moment? I know exactly how you feel about when its at 500 or so hp! I went to pirtek the other week to get a quote on some -8AN lines and fittings and I almost had a heart attack when i see the pipe diameter!! jesus its like 4 times the size of the stock fuel line!! :O just hope it doesnt mean it will drink 4 times as much when its all set up!!

[Baker]

If you want a fuel efficient car buy a diesel, not a 500bhp mr2

[RyanRs]

If you want a fuel efficient car buy a diesel, not a 500bhp mr2

lol but your missing the point there bud. incorrect / poor mpg can be a symptom of problems!

[monkeyminger]

i filled the tank at the local shell with v-power light was just coming on when i drove in.went to nothampton and got back to bradford when the light came on again.When i worked it out i got 29.7 mph and that was just under 300 miles with maybe 40 miles been at 50mph (speed cameras)
and the rest at 75+ .. i have a rev2 with exhaust,hks airfilter and 1 or 2 other mods and its quite low.

[sw20GTS]

Well, I am not sure if my odometer reads in miles or kmh. I do hope its miles though since my full tank lasts like 400 (roughly) on the odometer. That's mostly city driving though with occasional legging it on B roads.

However, I did notice an improvement in fuel economy after I put the induction kit in.

[Baker]

If you want a fuel efficient car buy a diesel, not a 500bhp mr2

lol but your missing the point there bud. incorrect / poor mpg can be a symptom of problems!

true that


but


the point in my comment


was


that


his fuel consumption is normal for a powerfull car


hence the comment

[wadeski]

Sorry to thread ressurrect, but i thought i would ask the question - do bigger injectors have a fairly chunky effect on mileage?

I'm running 850cc squirters and a TD06 to get 350bhp at 1.2bar, mapped by Ryan, but it seems to drink a fair bit more than before when cruising at 80mph on light throttle.

I seemed to use up most of a tank (not empty, from brim to just below 1/4 marker) in only 180 miles, and i wasnt really hooning it?

Is that "normal" or is it worth looking at the maps again for cruising?

[Marf]

What duty cycle are the 850s at under full boost max revs? Could you get away with downsizing them?

The problem with larger injectors is that if you have a relatively low resolution ECU(like the PFC), you'll lose fuel economy because the cell interpolation isn't great.

More advanced ECU's allow the addition of extra load cells so you can increase the resolution where needed, such as around cruise.

[Neptune]

50-60 miles to a quarter of a tank is pretty much the same as I get on my Rev3 tubby with exhaust, downpipe and ARC airbox.

I tend to get 230-240 miles to a tank, or if I do a stint on the motorway 260-300, depending on how much squirt I give it.

Thats good to know, i get bang on that mpg for my tubby.