MustangGT0405

So I put an O/R H on last week at the same time as the 10psi pulley. I have been running 8psi up to this point.

I noticed that the 10psi pulley is making about 9.5psi on the car. I was thinking this is probably due to the fact there is less back pressure now.

Has any other boosted member seen this?

Texotic

with an s/c, it's belt driven, so i wouldn't think that a lack of back pressure would change anything boost wise. with a turbo, that's exactly what would happen, though.

MustangGT0405

Being belt driven doesnt affect the boost pressure in what I am talking about. With a FI car if you reduce restrictions in the intake side or the exhaust side you will see a reduction in boost presure but not in power production. It has basically become more effiecient.

I know when you change to something like LT's you will see a reduction in boost, I was just curious if most have seen an almost 1 psi reduction just by dumping the cats. The car defineatly still pulls. I should be getting a dyno tune this week.

onederful100

i have LT's, o/r x pipe and muffler deletes. i was still seeing 10-11 psi w/ the 10# pulley. i have since switched to a bigger pulley and am getting 8-9psi. maybe its your environmental conditions.
but i did not test my boost before and after having the exhaust, the exhaust was already in when i got the SC, so i really dont know the before and after effects of having the exhaust, it could possibly be how you say, losing the boost.

Hufenstang

switching to long tubes and an o/r pipe net me a loss of 1.5lbs of boost

onederful100

now i remember a friend w/ a centri lost 1-2#'s w/ LT's and o/r x, but he still had more hp than i did w/ less boost.

MustangGT0405

Yeah that is how I thought it works. You dont loose any power it just gets more efficient so you can make the same power with less boost.

Thanks,

It sounds like if I ever get LT's with the O/R H I might be able to go to a 3.2" pulley and still only see 10-11psi.