How short can a downpipe be?

[gustavm]

Im getting a 3 inch dp done tommorow and Im wondering what the minimum length can be and still be effective . I was thinking only to the junction just behind the of the engine then back to standard exhaust which in my case is a resinator and 2 1/4 inch pipe through to a glasspack standard rear muffler with twin megaphone type tail pipes. Obviously later with funds availiable more 3 inch pipe could be added .BTW Battery is under the air intake pipe so a nice initial curve is not a problem

[dmgb5]

Umm...? Whats your objective here...i.e. what do you hope to gain from a 3" downpipe? What are your plans for the rest of the exhaust?

[gustavm]

To safely support about 12-14 lbs boost and increase spool up time . No big turbo or high horse power stuff . Id like to leave the rest fairly standard to keep that old fishing boat sound ! The guys are working on it at the moment and have decided to only go to the end of the engine block just after the hanger in 3 inch .Will give you all a report once Ive driven it.

[dmgb5]

Even just getting rid of the cast iron elbow would help with spool. So building it to the CAT/heat shield is plenty for what your after. Is the battery staying put or are you moving it for your downpipe?

[gustavm]

Battery is on the air intake side so no problem there.

[gustavm]

New DP . Seems to have done the trick . Pulls well from 1500 revs in 5th now.

[dmgb5]

Thats shorter than I imagined but it should certainly do the trick. Is it stainless? Why is it painted black?

[gustavm]

Maybe to prevent corrosion ? Paul did the same thing on my 9000 3 inch DP I must check if its still black after a couple of years .Im sure its just ordinary steel . The engine revs more freely and the car seems lighter ! that has to be a good sign. I may continue the 3 inch pipe one day . Bilstein rear shocks next.

[Squaab99t]

Originally Posted by gustavm

Maybe to prevent corrosion ? Paul did the same thing on my 9000 3 inch DP I must check if its still black after a couple of years .Im sure its just ordinary steel . The engine revs more freely and the car seems lighter ! that has to be a good sign. I may continue the 3 inch pipe one day . Bilstein rear shocks next.

Looks good. Much improved over the stock, but Saab had other requirements and constraints. If you have not done already, put the turbine heat shield back in place. I ran with mine off, but with a turbine fiberglass cozy and would have hot soak start issues. Seems like the hall sensor failed to give signal when it got too hot.

When you say pulls at 1500 in fifth, what boost are you getting if any or is it boosting quicker?

[gustavm]

I will get one before summer . So are you saying get a heat sheild or a turbo cozy?. Mine never had the heat sheild . Dont think Im getting any boost at 1500 revs but there is a definate off boost torque improvement . Im predicting better mpgs.

[Squaab99t]

Originally Posted by gustavm

I will get one before summer . So are you saying get a heat sheild or a turbo cozy?. Mine never had the heat sheild . Dont think Im getting any boost at 1500 revs but there is a definate off boost torque improvement . Im predicting better mpgs.

I'd say both, in my mind they do separate functions. The heat shield protects the dist and ignition wires. The cozy keeps more of the energy (heat) in housing for better spool.

[gustavm]

Interesting, Im wondering though with the early oil cooled t3 that I have would that increase the chance of baking the oil at shut down ?