firm shift hesitation - 2nd to 3rd gears only

concoursd · Post by **concoursd** » Tue Aug 25, 2009 2:36 pm

ExR90, you are probably hitting the overtemp protection after heatsoak. This is normal and really should not be disabled in the tune. It is designed to safeguard your catalytic converters, exhaust valves, and engine internals. It is designed to richen up the fuel mixture if the exhaust temps are estimated to reach above 1650 degrees. It considers intake temp, rpm, timing, fuel mixture to estimate the exhaust temps.

The exhaust valves will tulip in the heads and the catalytic converters will collapse if they are exposed to temps above 1650 degrees for prolonged periods of time. Some tuners disable this feature but I have forum posts where the car's catalytic converter collapsed, created 100% back pressure on one bank of cylinders, and later blew the rods out the side of the block while on the dyno. The tuner was puzzled as to they the car kept going into limp mode on the dyno and soon found out why. The catalytic converter material collapsed, sucked through the exhaust, and got stuck on the rear oxygen sensor.

In case you are wondering why a tuner would want to reduce/remove this feature is because on the 2nd and 3rd dyno pulls, it will show a reduction of power because the richer fuel mixture is not ideal for peak power but is useful in reducing the exhaust temps. Leaner mixture will result in a hotter exhaust temp. So, by disabling this feature, the later dyno pulls will show an improvement and consistent power at the expense of durability even though the fuel mixture is not dangerously lean on the A/F mixture.

mikel_too · Post by **mikel_too** » Sat Aug 29, 2009 2:37 am

Still willing to entertain suggestions and help on this...

mikel_too · Post by **mikel_too** » Wed Sep 16, 2009 6:00 pm

Still willing to entertain suggestions and help on this... (anyone???)

kmac1 · Post by **kmac1** » Thu Sep 24, 2009 3:40 pm

Just saw this post. This is a characteristic that I think everyone will probably have to live with if they want their transmission to last. These cars have what you would call a synchronized transmission. What this means is some of the gear changes will require more than one clutch/band to be applied or released during the shift. The 1-2 is fast and firm like you want it to be because all it is doing is applying another gear(OD band) on top of first gear. However, the 2-3 shift, the transmission must disengage the OD band before it can apply 3rd gear. This takes time and if you apply 3rd gear too fast you can smoke the OD band by overpowering it. Not good! For longevity I would say the Predator tune and likely all other tuners out there have the settings pretty much nailed without doing any damage.

Hope this helps!

Kevin@Diablo

MADSCOTSMAN · Post by **MADSCOTSMAN** » Tue Mar 09, 2010 9:33 am

Oddly enough, I have been experiencing a similar issue but between 4-5. When I travel on the highway (more noticeable when it's cold), in my 2006 mustang GT. I have the canned 93 octane firm shift tune on my car. When I cruise along between 60-70 on the highway it feels as if the car is having difficulty deciding which gear to be in and feels like it is shifting back and fourth between 4 and 5. Speeding up or slowing down seems to resolve the shifting back and fourth. I plan to restore my factory tune and update my predator to the newest crom. I will drive a few days with the factory tune and see if it may be the transmission before reinstalling an updated tune. Only mods on my car are a Granatelli CAI

tuningss · Post by **tuningss** » Tue Mar 09, 2010 9:42 pm

Do you have gear in the car or a converter?