interesting thread on 3si

I was just skimming 3si and thought this was an interesting thread to read:

http://www.3si.org/forum/showthread.php?t=242207&page=1&pp=10

It starts discussing 4" exhausts, then other restrictions holding the 3/S platform back, compares ideas that have been used on Supras, single turbo setups, etc. It has some interesting theoretical ideas. It's 7 pages, so it takes some time, but I found had some intersting points to consider.

how fast can we rev befor something gos wrong?

i work right next a guy who owns an exhaust shop and i was asking him bout 4" exhaust because the biggest he puts on is 3" because he says when you go to big it robs hp is this right or what? :smokin:

i work right next a guy who owns an exhaust shop and i was asking him bout 4" exhaust because the biggest he puts on is 3" because he says when you go to big it robs hp is this right or what? :smokin:


It has a negative effect on NA cars, it is BS in regards to turbo cars. This has been addressed in plenty of threads...if you want more info, do a search for "loss of backpressure" I'm sure you'll find plenty of info regarding the subject.


as far as mike's ?, I'm not sure exactly what you are asking.

With 4" piping the exhuats gas would lose velocity thus creating more difficulty for the engine to expell exhuast gasses. Also, with such large piping the exhuaust would cool off much more than would occur in smaller diameter tubing. The hotter the exhuast gas, the less dense it is which means that the engine will have less trouble "pushing" it out.

how fast can we rev befor something gos wrong?

Mike, i think what you are talking about is what damage can occur when you rev the engine up really high. There is something called "floating the valves" tha can occur b/c the lifters or springs are not designed to handle extremely high revs. however, i'm not sure what the limit is on our cars. search the 3Si forums for more info.

however, i'm not sure what the limit is on our cars. search the 3Si forums for more info.

i have heard that it is about 8000 rpm when the stock stuff begins to be a problem and valve float occurs.

Another sweet thread...john monnin's write up on swapping in a 3.5L 6g74...and even talking about boring it out to 4.1 He actually has a detailed write-up...granted it isn't anything that'll be happening in my near future...but it's great to dream!

http://www.3si.org/forum/showthread.php?t=240131&page=1&pp=10