Got my PCM tuned, still poor low end

[skinrock]

First off, I have a 2005 Impala with the 3400 engine. I have done the NAIOA Fender-well Intake, ZZP 2.5" catted downpipe and GMPP dual exhaust.

I got my PCM tuned by ZZP. They told me it was the same as what you find on their site: http://www.zzperformance.com/grand_p...=182&catid=107

The biggest thing I noticed is when it shifts from 1-2. The line pressure increase makes the shift nearly instant. Before I would notice a lag, and a slow pull at the start of 2nd gear. Now it's a smooth transition, it shifts at about 50-52 when I go WOT, and as soon as it shifts, it kicks and pulls MUCH better from there to 60 and up.

Launching still isn't that good, though. 0-20 feels like it's choking, once it gets to about 25, it starts to pull much better from there to 40. I'm pretty happy with the improvement, and the skip shifts definitely wake you up when you go to pass someone.

My concern is, what can I do for this poor low end? It might even be related to driving skills alone, but I just can't ever seem to get a good take off from stop. I'm assuming it's related to the low idle, 750-1000, and it just feels like it's slow because it takes so long to get it to about 3k where it starts to wake up, so while I'm waiting for that, and slowly moving forward, I feel like I could be going faster.

Is there a particular part that can help with this? I have the 3500 top end parts, but I think it will come down to having ZZP install it for me, so that's outta the picture for right now. The only other thing I know of is the throttle body.

ZZP's site says they change some stuff with the torque abuse settings, which is supposed to help with "bog at launch", but I didn't really notice anything.

[sharkey]

to realy wake it up, get a 3000 stall converter for it. im guessing the impala has a fairly low final drive and a fairly low stall converter. with a 3000 stall conveter you will be into the power band as soon as you put your foot into it. changing your final drive would also get the car moving a bit faster

[skinrock]

Is that something readily available for me? I think I have the 4t60 transmission.

[skinrock]

I found this one: http://shop.rezlo.com/index.php?main...products_id=31

[skinrock]

nvm, it has the 4T65-E, here are the specs:

1 2 3 4 R
2.92 1.56 1.00 0.70 2.38

Final drive on mine is 2.86:1

[sharkey]

gm did have a 2950 stall converter for the th125. luckily all gm 245mm torque converters are interchangable. i however cant remember what motor used that converter though.

[skinrock]

I guess I should get my facts straight first, does a stall converter literally mean it won't go until it reaches that RPM?

[86euro]

I thought the newer ones used a different material for the lockup clutch?

[SappySE107]

You should get a programmer and do it yourself. This will also let you know if you have massive KR or a fueling issue at low RPM. Did ZZP tune the car or sell you a PCM.

[skinrock]

They tuned mine, I went there. I didn't want to get a programmer for a couple reasons...a little too much, and I didn't really want to mess around with some of those settings. I'm not sure what they all do, and I didn't want to mess anything up. I just wanted a tune that has been safely done before.

[SappySE107]

Then it should be setup just fine. Your FDR sucks for acceleration but is great for gas milage. That may be the real issue with it then.

[sil]

I guess I should get my facts straight first, does a stall converter literally mean it won't go until it reaches that RPM?

nope, itll feel just like stock
except when you floor it WOT from a stop itll spin up to the stall speed

ie.. step on brakes real good, press gas pedal, watch tach and see what it says, thats your stall speed

any GM TQ wont have that drag racer feel
the GM higher stall TQ are a cheaper alternative, they do help launch at a higher rpm(in the better power band)

[discostu]

Wasn't it the 4 cylinder stall converters that had 2950 stall point?
If I remember correctly, the 2.0L OHC Pontiac has one, not sure about the OHV 4 cylinders though...
The TH125C has a lockup converter.
A 3000 stall converter means that the converter doesn't fully achieve hydraulic lockup until 3000 rpm. Below that rpm and the engine will be allowed to rev up more freely, thus putting it higher into the powerband before transferring full power to the wheels. Much better for acceleration. And with a lockup converter, you will still get great highway mileage.
And that 2.86 final drive is killing you. Great for highway trips. Crap for acceleration.

[skinrock]

I heard the FDR is something that isn't controlled in the transmission itself, is that right? Is it something I can have increased to help acceleration?

[bszopi]

The FDR (Final Drive Ratio) is the gear set inside the transmission. In order to change it, you need to change out the gearing inside the tranny.