New 4 in. exhaust! (custom)
12-08-06, 08:26 PM
#29
That is not true. All that matters is the exhaust has the highest amount of positive velocity without back pressure. To big will slow velocity to small will cause back pressure.
Highest amount of velocity w/ out undue backpressure BEFORE the turbo will help the spool, but velocity after the turbo has proven not to be as important for spool rate as increasing the pressure differential between inlet and outlet of the turbine (the other affect of the large pipe).
You want to keep the low pressure zone pulling the next pulses high pressure zone
You are correct that the gas slows fast as it expands into the large pipe so it has to pushed through the pipe by the higher velocity gas behind it, but during spool the volume of exhaust gas is increasing at such a high rate this phenomenon is already present- smaller pipe to *maintain* gas velocity is moot when velocity MUST increase to serve the exponentially increasing volume of gas.
As the gas cools and loses volume localized pressure will drop. You can actually begin to decrease exhaust size as the gas cools with no or little affect on top end power or rate of spool as the total backpressure changes little. You see an increasing number of downpipes designed this way now; large pipes reduced at the DP outlet or dual pipes back to single for the DP outlet.
[QUOTE]This also means a setup tuned for low rpms high velocity will be bad up top as to much back pressure is seen and one tuned up top will have low velocity down low as not enough exhaust is flowing and gives the gases time to collide and swirl. You want to keep the low pressure zone pulling the next pulses high pressure zone.[QUOTE]
Actually, the smaller exhausts affect the peak power surprisingly little as you must simply match the pipe diameter to the peak engine gas output- you can use the old hotrodders rule of thumb for peak #s.
Below 500 hp moving from 3" to 4" will net very little PEAK power (maybe 5-15 hp); it will gain you much more low end power as full boost will come on earlier as well as more boost at lower rpms.
As I said, I am not just spouting off turbo exhaust theory, but my actual experience using 2.5", 3" and 3.5" exhausts on the exact same car and turbo.
2.5" downpipe to 2.5" presilencer to 3.5" catback felt to have very nearly as much top end power as 3.5" turbo back. It was just the low end was horrible w/ the 2.5" DP/presilencer. It couldn't even hit full boost. Still at 15 psi boost on 2.5" exhaust it felt very nearly as fast as 3.5" turbo back at 17psi boost.
3" turbo back felt like exactly the same top end power as 3.5" turbo back, but the low end suffered a bit. Most noticeable was the power loss from idle to 1,500 rpm w/ 3". Data logs showed full boost hit ~500 rpm later w/ 3" system and several psi less per rpm before full boost.
Now to keep it quieter I run 3.5" downpipe (actually 1st 57" of exhaust) to 3" exhaust. Top end feels as good as 3.5" turbo back and full boost is 200 rpm better than 3" turbo back. A good compromise for me.
12-08-06, 09:26 PM
#31
Very easy to check for a coolant leak. Do a system pressure test and check for visable leaks like BAstard said. If you can't see any visable leaks do the same pressure test overnight, preferably on a level clean surface, and check for leaks in the morning on your floor. If you don't have a pressure tester and you have a coolant leak then your coolant level will obviously be dropping- check your resevoir level.
12-09-06, 08:21 AM
#34
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Originally Posted by ultimatejay
Very easy to check for a coolant leak. Do a system pressure test and check for visable leaks like BAstard said. If you can't see any visable leaks do the same pressure test overnight, preferably on a level clean surface, and check for leaks in the morning on your floor. If you don't have a pressure tester and you have a coolant leak then your coolant level will obviously be dropping- check your resevoir level.
In addition, if you do experience a pressure drop from the coolant pressure test AND there are no visible leaks, you can do the following to verify the diagnosis:
Disable the ignition and fuel systems and pull the leading plugs.
Take a couple a paper towels to cover the plug holes and have a buddy crank the motor. You should be able to detect any coolant leakage into the combustion chamber from the residue sprayed from the plug holes. As long as you are not running straight water in your cooling system, you should be able to denote a 'sweet' coolant smell on the towels.
12-09-06, 01:34 PM
#35
Did you have majestic in waco rebuild your turbo? If so that might be your problem i will no longer do business with them again after i had to return my turbos theve done for me several times before they got them right, first time they put the cold side halfway on, and i had to take it back a second time because the reason i brought it to them was one of the oil seals was out and it smoked, well i put it back on the car and the same thing happened, called them and they said they reused the old ones, so i brought it back they put new ones in and problem solved.... so therefor they sucked for me...just my experience with them tho...
12-09-06, 04:29 PM
#36
big port + big turbo=
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yes it was majestic Turbo in Waco. I thought about that, but i drove the car prior to having the exhaust made and it never smoked like this...
12-09-06, 05:28 PM
#37
big port + big turbo=
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the dump pipe he fabd up (coolant is from messing with the coolant in on the turbo ( was an idiot and turned the wrong way when trying to tighten)
4 to 5in. magnaflow tip, 4in. Borla XR-1 muffler
mandrel bent stainless (t304 i believe)
original resonator attached to the 4in. down pipe (unknown manufac.) 4in. all the way through
the T-70 and down pipe
in car video revs... its not really cold.... (temp gauge)
I made an out of car video but it was to loud and was nothing but static...
shows the tip
12-11-06, 03:26 AM
#40
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very very nice, i like it a lot. one question, when you said original resonator, did you mean the original main cat? sorry for stupid question, but im looking to do something similar and wanted to clarify. thanks
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