less boost??

[ACWALSH8]

With an aftermarket exhaust (catback and midpipes) I have read that boost levels can or are often decreased as a result of less back pressure.

With this loss in boost and the engine now flowing better does this mean that one can run a large pulley or a ported blower without causing any more stress to internals than before the aftermarket exhaust was installed.

With my mods I saw 13 maybe 14 #s.....after the exhaust if I dip to 12 or 13 can I up my boost to the previous level without increasing the risk of venting? I understand the more I add the higher the prob of a blown engine but I am wondering about this question specifically.

Any opinions?

Thanks,
Chris W.

[54Triton]

i have wondered the same and i don't see why not. The amount of boost you are running is basically the amount of stress on the motor so just bumping the boost back up to what it was shouldn't hurt anything. I am about to put a set of longtubes and midpipes on mine, which i figure will drop off a # or 2 of boost....afterwards, i plan on either porting my blower, or going for the Kenne Bell....still not sure yet. Either way, my boost will stay the same after doing the exhaust.

[Blu Buy U]

If you reduce back pressure, you are increasing air flow through the MAF,... the more air = More fuel to maintain the programmed A/F ratio. More fuel = bigger bang in the cylinder = more HP & pushes the strength of the stock internals.

[redvert]

Just my $.02...

Boost itself doesn't stress an engine. Power does... If you reduce your boost by increasing airflow through the engine and then add more boost to make up for it (and the fuel to go with it), you will have increased your power and that stresses your engines internals. Of course, NOTHING stresses an engine like detonation and/or preignition. If you lean your engine out and preignite, there's not many built blocks that will hold together.

So as far as brining the boost 'back' to its previous levels, you will need to make sure you are tunning for the increased air flow, and you will need to be sure your engine can live at the new power level..

btw, if you make less boost my increasing the airflow (with no change to the bolwer's output) downstream of the blower, you still have increased the stress to your engine because you have increased its power output...

[MRBLUEOVAL]

You are right but not completely. More efficient flow and HP with less heat build up will reduce some of the stress. I would tune for these changes with someone who knows what they are doing. You will see more power over a wider RPM range with headers and a ported blower but once you get up in the RPM ranges then the stress starts mounting with the HP output increase like redvert is saying. I suggest a phenolic spacer to keep that blower operation temp down. I would think a ported blower, 6lb lower and headers will give you the power you need and keep it within a safe zone. The 8lber and this setup could be pushing the limit. this is where I'm headed and I will have both 6 and 8lb lowers to be sure I am dealing with a setup that will not cause me to blow up. I have all the parts but need to polish the outside of the blower. The plenum and blower are ported and ready for action

[ACWALSH8]

thanks MBO....looks like Im going that direction shortly.