Need Help Bad

[justin99]

I have a stock 4.2 I6 other than a K&N drop in. My problem is that I am getting ready to tow my fathers boat 250 miles one way and it weighs around 3500 to 4000 lbs. I seem to have plenty of power but gas mileage is sucking. I would like for someone to take alook at my tunes and see if they can help me get alittle more power as well as gas mileage or mabye my tune isnt right. Attached is my stock tune and the one i am using. My concern is, I pulled this boat 60 miles today on this tune and after about 50 miles when it would shift from 1-2 2-3 is shifted alittle hard. I have a feeling i have something jacked up.

[justin99]

anyone have any ideas? I am leaving this Friday and need to get my tune worked out.

[justin99]

No one has any ideas?

[Mep_q8]

looking at your high octane tables, they do seem a bit high from what I've normally seen on the I6s...


for some more fule mileage id suggest you set the PE TPS enable to around 80% in all areas just so you don't run into PE unless you need too and also increase the Delay RPM to a higher value....

My blazer is running in PE pretty much all the time and do I spend alot of money on fuel even being in Kuwait!

With regard to it shifting hard, it might be the trans over heating... best bet would be to install a trans cooler specially when towing loads.

With the TM settings, I would increase it a little to help save the trans when towing for 200miles.... other then that, the tune looks good!

Get rid of your speed limiter though :P

[justin99]

It does have a tranny cooler. I thought the tune looked good. I do run 93 octane and do not get knock. I just want to be safe being that i will be towing over 400 miles this weekend.

[Mep_q8]

ill tell u wat though, for the weekend ur travelling, u won't lose THAT much power if u switch to 87-89 octane... lower ur spark and your saving urself some money on the fuel..

[justin99]

Can anyone give me some more help on this please? I just purchased a 18ftx8ft enclosed trailer that I will be pulling and I just want to get the best tune for towing that I can.

[justin99]

anyone!

[LS1408]

Not trying to be smart or anything but it sounds like you need to buy a bigger truck. Your probably not going to get any mileage with the smaller engine pulling 4000lb's. I have a friend that pull's his Camaro with his Trailblazer. On a open road it seems fine, but through in a hill or try to pass and you know it really doesn't have the power it needs to tow a car.

[Baldturbofreak.com]

Get a diesel. It's about the only engine that will get "mileage" towing.
A long tube header might inprove BSFC a tenth of a point or so, resulting in another mpg. No magic bullet.

[justin99]

I am actually not concerned about the mileage really. I would like more power while towing. I tow a 3500lb enclosed trailer with about 1000lbs in it. That is well under the towing capacity but the wind is a huge factor. The tune I have is "ok" but didnt know if anyone could help get alittle more out of it.

[Baldturbofreak.com]

The general doesnt leave much on the table for milage. But you can squeeze some ponies out by working with the timing and AFR in PE mode.
Each vehicle is a little different, so tweaking to the edge is something best done with the truck itself. start with a wideband and take the AFR to around 12.4 ish around torque peak then lean it out to 13.2 up top. Get a nice longtube header with 1.75" minimum primary. Then work with cam overlap in the midrange. reduce it a little at time until you get your best torque.

[b_faster]

Justin, the towing weight isnt going to be the obstacle, it is the aerodynamics of that enclosed trailer that will eat your lunch.

Keep your speeds at 60 and below and you will do the Trailblazer a world of good. Even diesel truck guys have to learn this tip sometimes.