Sudden loss & Gain of power

[buickman]

I notice if I change the gears on the AU VCT auto manullay at full revs the changes from 1st to 2nd into 3rd comes a shake & drop of power before the car starts powering up again. Cannot work out why only happens betwen I manully change the gears. I noticed at a dyno day the power drop of at those revs & gear change, the car seems Ok if left to change by itself. Is this a factory ECU cutoff.
buickman

[JC]

Sounds and looks odd to me. I've attached my dyno graph for the I6 Forte - and the power drop is nowhere near yours during gear changes - it flattens, but certainly doesn't dip. But then I'm also 20rwkw down on yours, so perhaps yours is normal and mine is sick!

[jonbays]

No I don't believe it changing gears on the dyno in the middle of a power run!!

Surely this is just the BBM changeover point your looking at not a gear change.

[JC]

In an auto, you don't have much choice in changing gears or not.

[buickman]

In the Buick, the 360cu charger & my old XB GT with pre computers it was straight power all the time. Even the 82 Corvette I owned with the computer. Manual gear changing the auto's never lost any power.

By the sound of it the AU auto's are better left to themselves to change for better performance.

buickman

[EFFalcon]

it doesn't look like gear chagnes to me.
if it was changing gear, it would drop right down again, then goto peak power again.
it also won't be able to pull different gears between 90 and 170km/h.

looks like somethings a miss there.

[Casper]

Thats not a gear change happening on the dyno, not a chance. If it changes gears it will "spike" the dyno. Mine did it when and spiked it to about 160+rwkw then tropped again.

I'm not sure what the first bobble is on your chart, its an odd one. The second one is a classic BBM switch along with the VCT cam change (happens about the same time) and is very normal (can be smoothed a fair bit with a chip tune). After that it looks like your line gets fairly rough. I'd say spark issues of some kind. I know I've seen a similar rough line on some e series dyno sheets that were fixed with new plugs/leads etc.

i have a au3 fairmont and it says that it has 157KW. But does it actually have that much power?

[Casper]

Originally Posted by AU3FAIRMONT

i have a au3 fairmont and it says that it has 157KW. But does it actually have that much power?

Unless it has some major head and cam work or is a V8 with exhaust and intake... then no.

damm. thats kinda stupid. so why does ford say it has 157KW? So the new BF they say has 190 KWs. So that wouldn't have it either !!

[Casper]

Originally Posted by AU3FAIRMONT

damm. thats kinda stupid. so why does ford say it has 157KW? So the new BF they say has 190 KWs. So that wouldn't have it either !!

157kw at the flywheel. Thats a factory spec and is generally correct.
What you are looking at here is rear wheel kilowats, measured at the rear wheels on a chassis dyno. Easy enough to confuse them if you have never dealt with it.

For the record, your 157kw engine would be between 100-105rwkw for comparison.

so what about a 5.7 litre 351 cleveland. Roller Rockers, 700 Double Pumper Holley. 31 Spline.How many KWs at the real wheel?

I know this is AU Forums and I have AU Fairmont. Im just fasincated!

[Casper]

Originally Posted by AU3FAIRMONT

so what about a 5.7 litre 351 cleveland. Roller Rockers, 700 Double Pumper Holley. 31 Spline.How many KWs at the real wheel?

I know this is AU Forums and I have AU Fairmont. Im just fasincated!

Its not an exact science, there are so many variables its almost impossible to say. I know a fair few of the modified Clevo guys are getting anywhere upwards of 250rwkw with some well past 300rwkw and beyond.

[Casper]

As for AU's, this is a good representation of the ones on this site:

http://www.fordforums.com.au/showpos...&postcount=176

[buickman]

Running the AU autos down the 1/4 do you guys change gears or leave it in 3rd gear with the power button on.
Because I reckon if I were changing the auto manually the sudden drop of power would have a Suzuki Jimmy sailing past me.

buickman

[Casper]

I change manually, so do most of the other AU auto driver that I know of. Im my case it makes for a quicker pass by anywhere up to .5 seconds.

[jonbays]

I let the auto do it for me but its tricked into changing at 5300 in first and 5600 in second by fooling the ecu that its going 13% slower than it is.

[Stav]

Buickman...the curves on your dyno sheet appear odd.The dip in power occurs in all bbm equipped fords ,normally at 130-145 kmph.Yours seems to cut in too early and then seems to flop back in at a higher speed. This may account for your air fuel mixtures dying at top end speed which would suggest that the bbm is holding the long runners.

[xr8ute]

Guys, don't forget that with an auto, the dyno operator can't use full throttle at low RPM because the gearbox would kick-down and ruin the dyno run.

Would be interesting to see a datalog of TPS voltage laid over the top of that dyno run.

[jonbays]

Originally Posted by xr8ute

Guys, don't forget that with an auto, the dyno operator can't use full throttle at low RPM because the gearbox would kick-down and ruin the dyno run.

Would be interesting to see a datalog of TPS voltage laid over the top of that dyno run.

correct and very important. i have had a few peple compare the big torque and low down power they get from their cam compared to mine but when you dig for details its like you only had 80rwkw at100k and i had 100 but it was a manual! If the dyno operator was silly enough to floor mine at 100 it would change down so its not full throttle.

in the old days and on older cars you used to disconnect the kickdown cable.

can't do that with the ecu. well I can sort of i i disconnect half of my shift kit wiring i get limp home mode third gear and reverse only. maybe i should try that at the next dyno run. problem is i think it retards the ign and all sorts of things to save the transmission too.