Lean during first cruise.... A little help appriciated.

[Bville99gt]

drove the car around the block and experience a very lean situation during cruise from 1500rpms to 3700rpms, didn't go any higher since I was driven around the neighborhood... I am not very popular with the neighbors (open exhaust). Set up consist of stock 93 SBF 302 roller shortblock, TFS 170 heads, somewhat big cam for turbo (can't find the specs), TFS intake manifold, On3 Turbo kit with 70mm turbo (7psi for now), and 80lbs injectors with 340plh fuel pump. Can you please critic and give any pointers on my tune. Thank you for your time.

test drive.msq

2016-02-03_17.55.14.msl

[turbo conversion]

Are you going to be putting an exhaust system on the car?

If so I would get the exhaust on before spending a lot of time tuning an open exhaust, open exhaust will tune different than an exhaust system.

David

[Bville99gt]

It will have exhaust, right now the downpipe ends right under the passengers seats the wideband is way upstream (more than 2 foot of distance) of the exit. I do not see getting those type of lean readings from having an open exhaust.

[slow_hemi6]

What size is the down pipe 3.5 or 4"? with that type of diameter 2' of pipe is not enough. Clamp a baffle on it that reduces the outlet down to about 2 inches and see if that improves it.

[turbo conversion]

It will have exhaust, right now the downpipe ends right under the passengers seats the wideband is way upstream (more than 2 foot of distance) of the exit. I do not see getting those type of lean readings from having an open exhaust.

With open exhaust there is almost no back pressure so more fuel will be required than with an exhaust system in place.

All I am saying is you need to finish your exhaust before you spend a lot of time tuning or you will be retuning.

David

[slow_hemi6]

You also have to keep in mind that with such a large diameter and no back pressure, the exhaust which pulses, tumbles and is generally turbulent will suck in gulps of external air as well. I have built a tailpipe sniffer for my wideband and it is really complex to get one working decently. On a 2.5" tailpipe I had to pick up the sample at least 1' down the pipe, the sniffer had to have an expansion chamber and an adjustable baffle at the end of a 6" long outlet. Still reads a little bit leaner than the permanently mounted sensor.

[Bville99gt]

Ok thanks will keep this in mind... won't mess with it until it has an full exhaust.