: Crossover pipe & Exhaust discussion



fubar569
03-27-07, 08:58 PM
ok, i'd like to start a somewhat technical discussion on exhaust and how to best eliminate the crossover pipe.

i know due to clearance issues running a 2.25 or 2.5" pipe right underneath the pan is out of the question...

the area of a 2.25" single pipe is 3.976"
a 2.5" pipe - about 4.90"

however running that right under the pan would be ludacris and you would have next to no ground clearance.

how is the flow of a rectangular section of pipe compared to a circular section? assuming the transitions were all smooth, would there be any penalty?

lets assume instead the pipe was rectangular in shape...about 4" wide and 1" tall...the area is 4" obviously or equivalent to a 2.25" pipe...would these flow the same amount of gas? or am i missing out on something here?

or would it be even worse of a restriction than the crossover pipe itself?

darien99
03-27-07, 10:09 PM
ok, i'd like to start a somewhat technical discussion on exhaust and how to best eliminate the crossover pipe.

i know due to clearance issues running a 2.25 or 2.5" pipe right underneath the pan is out of the question...

the area of a 2.25" single pipe is 3.976"
a 2.5" pipe - about 4.90"

however running that right under the pan would be ludacris and you would have next to no ground clearance.

how is the flow of a rectangular section of pipe compared to a circular section? assuming the transitions were all smooth, would there be any penalty?

lets assume instead the pipe was rectangular in shape...about 4" wide and 1" tall...the area is 4" obviously or equivalent to a 2.25" pipe...would these flow the same amount of gas? or am i missing out on something here?

or would it be even worse of a restriction than the crossover pipe itself?
You can get oval pipe that flows about just as well as circular. I plan on doing this IF I get this deep into my Cadillac.

codewize
03-27-07, 11:19 PM
We're still trying to obtain this information from Tim Allen. The DTSi has custom crossover and headers. I'm trying to get the specs on that.

fubar569
03-28-07, 12:32 AM
We're still trying to obtain this information from Tim Allen. The DTSi has custom crossover and headers. I'm trying to get the specs on that.



i wouldnt mind knowing, but odds are he wont be talking about it. headers look to be a TIGHT fit in my 97...really tight!

my dad`also needs to fix my MIG so i can start piecing some ideas together. i'm willing to bet the oval/rectangular section is going to be the best bet...

Edahall
03-28-07, 07:34 PM
Could you run 2 round crossover pipes side-by-side?

eldorado1
03-28-07, 07:45 PM
I think you can place a crossover where the water log is, if you use some flanges and stainless pipe available from CHRF.

Something to look into. You won't fit a larger pipe in the space available without getting rid of the heat insulation. Which is a bad idea, because you'd bake your oil.

danbuc
03-28-07, 08:11 PM
I just remembered the crossover pipe has a metal heat shield around it where it runs between the engine and trans. Supposed you were to replace that metal shield with exhaust heat wrap instead. I wonder how much space you could gain. It's
probably a small amount but every bit helps. Just something to think about.

darien99
03-28-07, 08:26 PM
I just remembered the crossover pipe has a metal heat shield around it where it runs between the engine and trans. Supposed you were to replace that metal shield with exhaust heat wrap instead. I wonder how much space you could gain. It's
probably a small amount but every bit helps. Just something to think about.

You could ceramic powder coat it also. It will rust A LOT less this way. :)

fubar569
03-28-07, 11:48 PM
You could ceramic powder coat it also. It will rust A LOT less this way. :)


a ceramic coat would be the way to go for heat reduction...and you could probably fit a bigger pipe through the existing location or where eldorado1 suggested...

would there be a downside to going underneath the car besides ground clearance? it wouls also be a somewhat smoother path i assume?

i suppose finding the diameter of the crossover pipe would be a good start...
what is the stock crossover? and i assume its pressbent too? not a good combo...

as stated ceramic coated would be the way to go there to gain some area...but youd have to have it precision/custom bent...

how hard is it to remove the stock crossover as/is? is anyone else's front manifold-to-crossover pipe bolts threaded in from the top?

eldorado1
03-29-07, 10:23 PM
Ceramic coating won't cut it. You need insulation.

Ceramic is good for a 200 degree reduction in pipe temps, which means you're still 500-700 degrees and boiling your oil.

You have to remove and separate the engine and transmission to remove the crossover.

fubar569
03-29-07, 11:16 PM
Ceramic coating won't cut it. You need insulation.

Ceramic is good for a 200 degree reduction in pipe temps, which means you're still 500-700 degrees and boiling your oil.

You have to remove and separate the engine and transmission to remove the crossover.

very good point...what if you coat it and wrap it? think it would have a fair shot then?

you have to seperate motor and trans to remove the crossover pipe? just...wow...go GM on that one...

so the best one could do would be to bypass the crossover with everything in the car...and still have it hanging in there bouncing off of everything...fun times...

Raze
03-30-07, 08:55 AM
naa you could cut it off but if you do that, welding a new pipe for the front bank will require u to take the header off anyway and once you do that you may as well just drop the cradle and pull the engine/tranny off especially to help w/mocking it up...

This is going to be an interesting modification and I plan on doing it on my Eldo later this year when $ permits and I get my old Eldo back on the road, just don't plan on me selling headers cause unless you can pull your engine/trans yourself it just won't be worth it for everyone who 'wants' performance...

darien99
03-30-07, 09:13 AM
Ceramic coating won't cut it. You need insulation.

Ceramic is good for a 200 degree reduction in pipe temps, which means you're still 500-700 degrees and boiling your oil.

You have to remove and separate the engine and transmission to remove the crossover.
If your car is seriously hitting 900* on the crossover you have bigger problems to deal with. :alchi:

I'll stick our thermo gun on my Cadillac today at work, but I bet you the crossover won't hit over 550* beating the hell out of the car. 200* or so off of that would be fine. What kind of temps do you think our oils see anyway? Warmer than you'd think...

darien99
03-30-07, 09:15 AM
just...wow...go GM on that one...


LOL If I had a quarter for every time I said that....

fubar569
03-30-07, 12:13 PM
naa you could cut it off but if you do that, welding a new pipe for the front bank will require u to take the header off anyway and once you do that you may as well just drop the cradle and pull the engine/tranny off especially to help w/mocking it up...

This is going to be an interesting modification and I plan on doing it on my Eldo later this year when $ permits and I get my old Eldo back on the road, just don't plan on me selling headers cause unless you can pull your engine/trans yourself it just won't be worth it for everyone who 'wants' performance...


how would running a pipe under the car require you to take the front manifold off? the crossover unbolt right at the bottom of the motor and i'd just borrow the flange and bolt the new one back up?

i have no plans to drop the cradle to do this...cause like you said if i do it'll be all tubular or bustat that point...

fubar569
03-30-07, 02:20 PM
i just got done examining the exhaust a bit, and the EGR feeds from the stock crossover pipe. this would mean:

1. modify EGR tube to connect to one of your new pipes.
2. Eliminate EGR

i'm gonna shoot for number 1 as i think it could be done with minimal effort.

the stock crossover could be unbolted then cut and removed if desired, retaining the EGR pipe "bung" for use in your new system.

i think i'm gonna try to play with the airbox next for a bit...

jadcock
03-30-07, 02:43 PM
If your car is seriously hitting 900* on the crossover you have bigger problems to deal with. :alchi:

I'll stick our thermo gun on my Cadillac today at work, but I bet you the crossover won't hit over 550* beating the hell out of the car. 200* or so off of that would be fine. What kind of temps do you think our oils see anyway? Warmer than you'd think...

EGTs get higher than you think. During WOT, I wouldn't be surprised to see at least 1000*F INSIDE the exhaust manifold. That's a blast furnace in there. It will cool some as the gas expands, but that crossover will run plenty warm, under some situations. Under normal circumstances, you're right, it's probably lower than 500*F.

The actual motor oil temperature won't get very warm, especially during normal driving. Maybe 200*F. It takes a lot of sustained high RPM to drive up oil temperatures. Sitting in traffic during the daily slog, that oil will actually stay pretty cool.

fubar569
03-30-07, 06:20 PM
i just got back inside from round 1 of airbox mods.

i smoothed everything out, lopped off the silencer, removed the snorkle, removed the ribs on the lid and smoothed it out, etc...i only have a paper filter now but it seems to have made a small improvement...i'm sure it will mean more when the exhaust is finished.

the real purpose of tinkering was to examine to see if i could easily relocate the washer fluid tank for other intake ideas. it seems doable. this would also mean relocation of the PCM which im not too crazy about but i think its doable as well...probably not worth the effort though...

i'm also still trying to envision the new crossover pipe setup...and the hard part is gonna be to keep the EGR....

danbuc
03-31-07, 03:12 PM
EGTs get higher than you think. During WOT, I wouldn't be surprised to see at least 1000*F INSIDE the exhaust manifold. That's a blast furnace in there. It will cool some as the gas expands, but that crossover will run plenty warm, under some situations. Under normal circumstances, you're right, it's probably lower than 500*F.

The actual motor oil temperature won't get very warm, especially during normal driving. Maybe 200*F. It takes a lot of sustained high RPM to drive up oil temperatures. Sitting in traffic during the daily slog, that oil will actually stay pretty cool.


Your correct regarding EGT's between the manifold and cats. They can get extremely hot. As an example, when monitoring closed loop operation in most new Mercedes through the SDS (scan tool) the vehicle doesn't go into fuel closed loop until the exhaust gas temps are around 700+ degrees. They get that hot just idling in the bay. Exhaust heat wrap is your best bet at significantly reducing the radiant heat put out by the crossover, especially under high load. As an example, when I installed a set of Headman equal length long tube headers in my '66 (back when I had it) I had to wrap the collectors with heat wrap to prevent my trans fluid form overheating. It worked just fine. Granted, I never really ran the car hard that much except for on rare occasions, but I never had a problem with burning the trans fluid. I bet exhaust heat wrap could work, but you'd probably have to use a significant amount. The temperatures in the crossover under high load, are definitely a butt load higher than the temperature of the gas exiting the collectors on the Stang's headers. I'm sure if you ceramic coated it, and wrap it as well, you could probably get it down to around 450-500 degrees or so. Keeping the heat in will help increase exhaust flow as well...which isn't a bad thing either.

fubar569
03-31-07, 08:07 PM
as soon as my dad fixes our MIG i am gonna try pondering a new crossover idea...

today though i did round 2 of airbox mods...which involved temporarily removing the PCM from its safehouse in the lower intake and opening that up, along with the filter tray, and i expanded the new opening created by removing the silencer...she is definitely responding well and is drawing in more air...the sound alone was worth it, but i did feel a slight SOTP improvement...

i should have some money flowing soon...so i can do the exhaust...w00t!

any ideas for keeping the EGR? it feeds from the stock crossover...i would have to somehow extend it...the EGR pipe that is

darien99
04-01-07, 10:40 AM
Well you can feed the egr from any exhaust point if that helps...I wonder if '95/OBD1 would ignore the EGR being gone. It doesn't monitor the cat I know...

fubar569
04-01-07, 01:13 PM
Well you can feed the egr from any exhaust point if that helps...I wonder if '95/OBD1 would ignore the EGR being gone. It doesn't monitor the cat I know...

i bet it would still throw a code but since OBD1 can be edited you could just delete it in the tune...

fubar569
04-02-07, 10:34 PM
well...i decided to experiment with a small section of 3" pipe tonight...it looks like 3" will do the job...this is the preliminary shape for the new crossover pipe:

edit: pic coming...but the shape is a 3" pipe squished to a rectangle measuring roughly 1.275" tall ID x 3.775" wide ID providing the rough area of a 2.475" pipe...not quite 2.5"...but close...i think that should be enough flow for the new crossover especially if the rest of the system is 2.5" duals out the back...

if this turns out to work well, i believe this would relieve a major bottleneck in the system...next chore is to test hang this small section of pipe to measure ground clearance changes...after wrapping and such i'd anticipate about a 1.5" reduction in front ground clearance, however this design should provide for the most flow versus that reduction in clearance.

i will report back tomorrow if the weather is good with further findings...

jadcock
04-03-07, 10:30 AM
2.5" of area for 4 cylinders of exhaust seems excessive.

fubar569
04-03-07, 11:39 AM
2.5" of area for 4 cylinders of exhaust seems excessive.

seems that way, but my mustang was dual 2.5" (~300hp), my talon TSi 2.5 (300+hp turbo), my big block has 3" collectors (600+hp)...2.5 might be a bit excessive, but i wont have to do it again.

even my corvette...which was only 205hp (crossfire) had 2.25" piping from GM (just measured the cut apart section of the front Y in my basement) - with this northstar hopefully making over 300 i think 2.5" would be just fine...

fubar569
04-07-07, 01:48 AM
my dad gets home tomorrow...he is being chained to the mig welder cart till he gets it fixed...

my spare intake and throttle body should be on the way soon (won on ebay for 60 bucks)...

TB and spacer are going out to be bored and intake is getting the dremel tool...

i have the prototype replacement "crossover" about shaped up. uses 3" pipe squished into a rectangle. i need the flange off the stock crossover pipe so i gotta get something in there to cut it off...

i havent got the EGR figured out yet. i just need to extend it to SOME place in the new exhaust and wont know where or how till the car is off the ground and parts start coming off...

i need to order some 2.5" pipe, fab an X section, and get my dynomax bullet mufflers on order...

if im keeping EGR i really oughtta try to at least pretend to install some bullet cats too...eh...maybe...we'll see...

I will probably wind up doing the coils/plugs/wires as well, and possibly wind up with a DIS-4 if i find a good deal on one...

I'd also love to have an XFC piggyback to wire up...if for nothing else than fine tuning and live PC monitoring and datalogging...

injector flow balancing is on the horizon, but not before exhaust and throttlebody...probably will be done once the intake is finished...i am also going to do a custom heat shielded CAI/RAI (cold air/ram air)

ambitious? yes...

help me realize these goals by looking and buying:

http://www.hardforum.com/showthread.php?t=1175309

jadcock
04-07-07, 08:22 AM
Got a pic of the new crossover?

fubar569
04-07-07, 12:28 PM
Got a pic of the new crossover?


i cant really finish it till the weather gets warm and my dad fixes my Mig...so really no pics yet. i promise you will have some of the finished deal though...i have the general idea and a design drawn up...and a proof of concept section (about 3-4" long) completed but im waiting on him at this time so i can get it up in the air and make the final measurements and buy all my exhaust tubing at once. the final dimensions look to be ballpark 1.275 x 3.775 rectangle formed from 3" round pipe. it will bolt to stock manifold using the stock flange and contour as closely to the underside as permissable. i am sending the final piece off to be ceramic coated inside and out and it will be wrapped as well.

another thing i need to do is figure out what to do about including flex sections in the exhaust, or if its even nessesary to do...

also need to get a few smaller pieces of 2.5" so i can tack together an X section...i would like to see how the crossover will be in relation to the rear manifold before doing this though...if the flex sections needed to be added i could prolly do that on the front side of the X-pipe and make it an all-in-one unit...

lisekpl
04-07-07, 12:44 PM
Good luck on your little project there.

fubar569
04-12-07, 02:00 AM
my dad is starting on the mig tomorrow hopefully...

i believe i just sold my SKS rifle and my LCD monitor...so the project has some preliminary fundage

next good day i am gonna measure and order a good amount of pipe and start on the little stuff...

i got my intake and TB in the mail...this dude's intake was DIRTY...perhaps PCV issues? ohwell...bathe it and bring out the dremel...

eldorado1
04-12-07, 09:32 AM
The EGR gets injected into the manifold just after the throttle body. It combines with the PCV oil and turns into a hard brown mud and coats the intake.