Surprising mpg on new crossflow!

[petrolhead]

Just came back from a 'running in' drive from chessington to worthing and back again (exactly 84miles according to GPS & RAC) at a average of 60mph.

 

Brief Engine spec: 1700cc, full race head, 244cam, twin 45's and megajolt

 

Result? 29.1mpg!!!

[Mr Sam]

 

fast reliable and economical

 

 

 

why do people bother with modern junk

[bmxdave]

Youll often find that a well set up modified engine, is far more efficient then a standard one because you dont use as much throttle and your engine is far more efficient.

 

Thats my arguement for going mad on tuning an engine anyway.

[petrolhead]

I like your logic

[Mr Sam]

i like it too

[morcheen]

was it all down hill one way ?

[RChambers]

Thats bloody good for a car on twin carbs!! MY 325 Coupe does just over 30mpg although that is at 90 mph rather than 60 My zetec used to be able to push 40mpg on a run (in a mk2 Escort). Watch the fuel economy drop once its run in though

[bortaf]

Megajolt, does that every tme

thats why it's so popular, you just can't beat modern leccy gadgets for fuel economy

[fergus mk2]

yove gave me a bit of releaf mate is that wit a 4sp or 5 and on a motor way i presume none of them over here only big hills

[petrolhead]

4 speed on A roads (A24) and light traffic, could have got more if I was careful I think.

[SLYMAN]

Is that using the 2d map with Megajolt?

 

That seems far to good MPG, fit some bigger jets for christ sake!!

[fergus mk2]

sorry lads wats megajolt?????

[iokarus]

ooooow, big shock to sum1 new to the OSF world to find that 29.1mpg on a 60mph run is condsidered good! Id hate to know what sum of u must be getting to the gallon!

[Tom]

sorry lads wats megajolt?????

 

megajolt is a spark only fully home mappable 3d ignition system bud, will set you back around 100 quid

[texr2000]

I use to get MPG like that when i was running in my x/flow.... dont think i sceen 20MPG sence... saying that i havnt had it on a nice long run on the motorway recently so donno, but my old engine on 40's was better on the motor way than the GT webber with fuel....

[fergus mk2]

so is it better that electronic ignition or is it a fancy version of it????

 

cheeRS

[Tom]

Its a dizzy-less system mate running off a crank trigger. i've got one and once you've got it fitted and figured out its brilliant

[fergus mk2]

is it a better job that the dizzy??? more responsive or wat??

cheeRS

[petrolhead]

That's it, once you've figured it out it is good. You get built in rev limiter, shift light and 4 programmable outputs for your money too.

 

Fuelling is spot on at the moment. I would have thought economy would improve once run in - less friction as the moving parts are bedded in. Unless of course, you mean the change in driving styles!

 

Economy was the last thing I was thinking of when I got the engine built, I was actually expecting 22-25mpg

[petrolhead]

You can basically tailor the advance at differnet loads and revs to absolute perfection. Even a modified dizzy will only ever be a compromise. So to answer your question maybe not more top-end power but more torque overall.

[fergus mk2]

oh rite but they need to b set up rite dont they theres no 1 capable of doin that over here

[Tom]

and plenty more drivability too i can put mine in 5th at 30 and put my foot down and it'll pull cleanly and smoothly rather than struggle

[Toby]

That does sound good.

 

What compression? 1300 pistons? Compression can have quite a bearing on part throttle full economy.

 

Diff ratio? Don't say 5.1!

[petrolhead]

yep, fair points.

 

11.7:1 compression

3.54:1 diff ratio

[SLYMAN]

Thats high comp!!

 

Remember to change da oil soon, shards of metal and ting in der