I am throwing in the towel on the crappy tranny shifting on my 2010 FX4 and I have ordered an SCT XCal3 with custom tunes from VMP. I was thinking about doing a before and after dyno run at a local shop, just out of curiosity.

I have done some dyno tuning on my Triumph Rocket III motorcycle, and always do the runs in 4th gear because is it closest to a 1:1 final drive ratio. It looks like that 4th may be the closest on the F150, but with the 09/10's, the automatic trans you can select 1, 2, and 3 and D. Any suggestions? Anyone know what PHP did when they did their runs with a 2009? Can the SCT allow the user to hold a gear?

 

your dyno shop will know what to do if they don't then go some place else.

 

Not easy info to find, but I did find this:



Note they used 3rd gear - I'm thinking that's right as it's the highest gear that can be held by the gear selector.

No - the tuner isn't the way to do this (hold a gear).

MGD

 

1:1 ratio is the ticket, so 3rd with the OD off.

 

No 1:1 in that 6-speed .... nor OD 'off' functionality ....
4th and 5th bracket 1:1, but 3rd is the highest ratio that can be held.

MGD

 

I'm interested in hearing why "a tuner isn't the right way to hold a gear".. Maybe it's just me, but in my Lightning I had a dyno program that had all the same engine parameters but had different trans parameters so that I could dyno as low as 2500 without it jumping to 2nd, this was all through an EEC-Tuner.

 

i was told by a guy who owned a performance shop in florida that you dont need the 1:1 ratio to figure out the HP. and anyone wondering, because i was, a 95-97 trans am LT1 he said averaged 312hp at the crank without the ram air. just a stock LT1 trans am which was rated at 285hp. it was well known that the LT1 and LS1 in the f-bodies were under-rated so it looks like the number is 312 and i dont know about the 93 and 94 which were rated 275, but i would guess 302-312

 

This is a separate TCM - this level of complexity is going to require a bit more work on the part of the tuner to accomplish - for little reason, since 3rd appears to cover a wide rpm range.

See the plot above - it's got a spread from below 2500 rpm already.

Never said it was not possible - just that it isn't done, or required, normally - even on a 4-speed - most just use 3rd, OD off. Or held in second, if required. Seems to be the preferred method, for a reason. No apparent issues with it inadvertantly dropping down a gear.

Lots of plots here show this: http://www.vmptuning.com/forum/forumdisplay.php?f=34

But yer right - I should have said 'not the preferred' way instead of 'not the right way' - thanks.

MGD

 

2nd is often used on trucks because the tuner doesn't want high rotational speeds at the tires and drive shafts. Not sure what the 3rd ratio is on the 6 speed, but I couldn't see them going above 3rd for the same reason. Of course, if its something built for those sorts of speeds they may very well choose a higher gear (helps with dyno "shock" so they can often get a power reading at a lower RPM). The tuner is usually going to factor in several things, like the vehicle, tire size, final gear ratio, etc.

 

Thanks for the responses and good find MGDFan.

3rd gear is 1.52 to 1, 4th is 1.14 to 1 and 5th is an overdrive at .86 to 1 (6th is .69 to 1 in case you were wondering). These specs are directly from Ford and I believe don't figure axle ratios and wheel/tire size.

I'll have to ask the dyno operator if there is a correction factor for gearing, but really I guess it doesn't matter too much, I am not really concerned about the final numbers, just more curious about how much of a gain there will be.

 

3rd gear, a good dyno operator can adjust the setting so it's close to a 4th-5th gear ratio's

 

yeah i was talking to that guy who said he owned the place in florida. i was telling him about my truck being 1:1 at 4th gear but that i cant do that stock because my truck is speed limited at 100mph which is 4k in 4th. thats when he said you dont need 1:1 which i understand its easier to figure out but there has to be a way to figure it out if you know what the gear ratio is for the gear you use. plus wouldnt a 3.55 rear end show different than a 3.08? the transmission gear is 1:1 but the wheels are not 1:1. or does what im thinking of only effect the torque reading?

 

Dynos don't actually measure hp.

They measure torque. HP is calculated from torque.

hp = T*RPM/5252