4-2-1 exhaust manifold good idea? and question about gearbox oil

[tau9]

hello again!

if I make a custom exhaust manifold (old grey specs) can I have problems if I keep with the stock ECU?

ty

[BrownDog]

nah shouldnt do

[tau9]

Originally Posted by BrownDog

nah shouldnt do

okey then, I was worried cause i've go to a workshop that makes custom exhaust and he told me that there's a chance that the engine can run bad with custom 4-2-1 exhaust because electronics

The custom 4-2-1 manifold costs 500EUR

I have another question about the gearbox. the fifth gear it's too short is there a way to make it longer so I can cruise at 100-110 kmph @ 3000rpm? stock ratio makes the car too much rev happy at 100 kmph and this raises the fuel consumption a lot if i go faster than 90kmph (spanish roads are ok to cruise at 110 kmph)

i hear you can swap the 5th gears of a mazda 626/mx3 that are longer so the car can cruise at higher speeds at lower revs

Is is true?

[Cosmo Dude]

Yes you can use the 5th gear from a GD 626 to make it rev lower on the highway but if your engine does not have the right power at those revs then it will struggle and you may use more petrol not less.

[tau9]

Originally Posted by Cosmo Dude

Yes you can use the 5th gear from a GD 626 to make it rev lower on the highway but if your engine does not have the right power at those revs then it will struggle and you may use more petrol not less.

yeah well the car accelerates well at stock revs/5th gear/90kmph I think it yould be okey if the car goes at 100-110kmph at same 3000 revs. It's for cruising.

In the near future I will add the 4-2-1 manifold and If I do the ignition mod wich make more torque in the mid rpm should me more than enough to keep the engine at good power in mid revs

the car uses a lot of fuel when cruising at 110 kmph because running at more than 4000rpm

[tau9]

mazda manual says G5M-R ratio is 0.795

but in other places (forums) I read ratios of 0.837 :/

Damn! Stupid old mazdas! there's no info about the 626/mx6 gearbox

EDIT: found this



got the info from here: http://www.mazdabg.com/ftp-uploads/6...da%20626%20GD/

need the "RF" gear but RF engine is diesel

F8 5th gear engine ratios are same

also BG mazda 323 BP sohc have better ratios for economy but it's a different gearbox! (F5M-R)

[Rupewrecht]

Search the forums, there's threads listing the correct "626 5th gear" part numbers.

[HMT]

You could also just use 5th gear from a G-series transmission of a 323 BA 1.8.