power loss

[wpdozer]

Hea guys, This is my first post so bear with me. I have a 1986 Chevy M1031 CUCV with a Banks turbo and 700R4 conversion. It's the one in my avitar. Since the trend for putting stacks on pickups is back, I decided to stack mine. A friend of mine sugested just running a straight pipe. I did that and now i've lost some power going up hills. I do not know if the IP was turned up when the turbo was installed. If so, would I have to make annother fuel adj as there is no back pressure now? The turbo spins a lot faster though, and it seems to have lowered the RPMs on level road wich is a plus. Thanks, Wayne.

[john8662]

Got Gauges?

You need a boost and EGT gauge to tell you what's going on here.

Straight pipe exhaust should have increased performance, and noise.

[wpdozer]

I have the guages, Boost remains the same, EGT dropped approx 100 deg when going up the hill I had mentioned, and have to floor the throttle going up that hill. It stays in OD all the way up, should i adj the tv cable? The engine does not lug, just seems to be starving for fuel with little or no black smoke when it's under load or when I boot the throttle on level road.

[john8662]

As with any possible fuel starvation type issues, replace the fuel filter, as a first.

The no smoke and 100 degree lower EGT sound like better flowing exhaust to me. Not smoking is a very good thing normally, means you're burning all the fuel in the chamber, running efficiently.

How fast are you going up the hill when the trans stays in OD? They usually can shift down at WOT. I know you probably have 4.56 gears, but TH700's still aways shift down, maybe too fast to downshift.

[wpdozer]

Hea John, Yea, This truck runs suprisingly clean, Probably due to the turbo. The previous owner did a spin on fuel filter/water separator upgrade. Guess i'll keep it simple and just change the filter.:o Seems odd that the loss in power happend after I put the straight pipe on it. Question, Are there any other IUOEs here at DP? Thanks for the advice, I'll keep you posted. Wayne.

[Robyn]

I agree with John.

Get a fresh filter on the beast and see what happenes.

Changing the air flow though the system can have unpredictable effects.

Some times things are right in a sweet spot so to speak and changing things can make a difference.

If you are running totally clean stacks, you can certainly "bump" the fuel screw up a tad.

Maybe 1/8th turn and then see what it does.

You don't want Black rolling out, but a tad bit of haze is OK

Keep your WOT EGT under a hard load to no more than 1000F

A Banks system will normally peak at 10 PSI which is fine for these engines.

Missy

[wpdozer]

Hea missy, The air filter is a Banks washable that came with the system, It's clean. It's a total Banks setup from air filter to tailpipe. I removed the muffler, installed a 90deg bend and ran it up through the flatbed. I know of that sweet spot you refer to. I do not have a tach, but it seems to be at about 55-62mph-700R4-4.56 gears. The engine is real happy there. I did make an adj to my B&M lockup controller this morning and to my surprise the shiftpoints changed! It now downshifts going up that hill I refered to, 1 mile @ 25% grade, without having to floor the throttle even though it's in lockup as it was before I made the adj. I don't get it, I thought the TV cable controlled shiftpoints. The trans used to slide into drive before I made the adj under heavy throttle, now the shift is crisp. I guess we can surmise that the power loss was more of a trans issue than a fuel issue. I never would have thought of it untill I started fooling with the lockup controller. I really don't like this trans, It's all over the place all the time, Rather have a TH400, but I need to run the highway. Can't do that with a 400 and 4.56 gears. This lockup controller affecting shiftpoints has me baffled, any feedback will be appreciated. Thanks, Wayne.