esp-6

what ratio in turbo 250xflow

18 posts in this topic

Hi guys

As the title suggests, got a bw LSD with 2.9 gears at the moment, have a 250xflow turbo c4 gearbox with 2500 stall 
looking to go either 3.23 or 3.45 what would best suit the turbo engine ? 

cheers

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Hi guys

 

As the title suggests, got a bw LSD with 2.9 gears at the moment, have a 250xflow turbo c4 gearbox with 2500 stall 

looking to go either 3.23 or 3.45 what would best suit the turbo engine ? 

cheers

 

I would think 3.45s to be too short for something without an overdrive box. 3.23 would have it singing a bit on the freeway too but depends on your priorities. I'm going back down from 3.27s because manual and cruiser. 4th gear (1:1) in mine has about 2900 up at 110 K's. Yours would be more with converter slippage.

 

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i would say depends on the cam. and rev limit. and when the boost comes on.. 

i'd try 3.23 because they are common and cheap.. get one, bolt it in.. try it. if it's too slow to get the 3.45
 

 

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also don't rule out the 2.92 depending on the combo also.. i've seen some turbo 250s running the 2.92 and they pull like a train with a smaller turbo making boost early

gerg likes this

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also don't rule out the 2.92 depending on the combo also.. i've seen some turbo 250s running the 2.92 and they pull like a train with a smaller turbo making boost early
Yeah I was thinking this too. Turbos make torque so taller gears might work even better than with N/A. That 2500 converter is already fairly high for a street-friendly crossy.

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Its got a fairly lumpy cam un sure on specs. It pulls like crazy on boost but just feels real sluggish untill it gets there. Might try 3.23 to waken it up a tiny bit and hopefully not lose that pull it has up top. Its a crossflow after all only revs to 5ish on a good day haha

deankdx likes this

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can't just say crossflow can't rev.. because there's a few that are pulling big revs with some decent upgrades

CHESTNUTXE likes this

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Mines a 4 speed and I went back down to 2.9s. I had 3.7 and tried 3.23 and there was little difference. First gear was way to short and banging throw the gears way to quick. Revs are the big killer, mine only pulls to alittle over 5k. Starts making boost around 2600rpm and full boost (10psi) at 3k.  2.9s in 3rd at 5k im doing about 155kph. Mines also in a corty so pulls along nicely off boost and cruising around.

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13 hours ago, LJDB said:

Mines a 4 speed and I went back down to 2.9s. I had 3.7 and tried 3.23 and there was little difference. First gear was way to short and banging throw the gears way to quick. Revs are the big killer, mine only pulls to alittle over 5k. Starts making boost around 2600rpm and full boost (10psi) at 3k.  2.9s in 3rd at 5k im doing about 155kph. Mines also in a corty so pulls along nicely off boost and cruising around.

not sure on the gearing in the c4 but id assume the 4 speed would have a shorter 1st compared to what im running, think ill try 3.23 and that will hopefully give it a bit more out of the line and hopefully not lose too much up top. i havent put a boost gauge on it yet (just got one yesterday) so not sure at what rpm it makes full boost, definitely comes on hard early though.

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15 hours ago, CHESTNUTXE said:

the grand prix turbo was changed from 2.77 to 2.92 if that helps .

2.92 is stronger i think(than 2.77). might be one of the reasons

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11 hours ago, CHESTNUTXE said:

yeah the std s pack diff was replaced with a 2.92 v8 xe diff.

might have been 28 spline possibly then, i don't think the 2.77 were ever 28 spline?

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12 hours ago, CHESTNUTXE said:

only in 351 factory fittment auto,xd,fairlane,ltd ect very rare diff and hard to find

learn something new every day, didnt think the 2.77 came in 28 spline at all. 

would the 2.92 in mine be 28 spline ? its a factory 6cyl esp 

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only in 351 factory fittment auto,xd,fairlane,ltd ect very rare diff and hard to find

and some ford Xe Fairmont Ghia 6 cylinder efi turned up with them too particularly 83 year model. But if it has pbr calipers on front and not Girlocks good chance it have that diff. How and why I am not sure but do know that ford were known to flog all gear that normally came from previous model/specs or change in suppliers etc from the parts bin till ran out especially in either in certain models such as ghia or limited edition/one off production run.


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