Can anyone tell me the benifits of installing a crossover?
I've installed 3in down pipe with 4in all the way back, and its night and day....best mod I have done so far along with the 3 bar map. Is it going to make a better difference? Or should I leave it alone? Thanks.

I haven't replaced mine, so I can't say first hand if there's a difference. I don't think that the benefits would be worth the work (my speculation). To increase power, you need to increase efficiency. And to increase efficiency, you need to relieve the restrictions on your motor. The factory exhaust is clearly a bottleneck and is well worth replacing. The cross over can only be replaced by a mandrel bent cross over, unless someone's trying to sell you a 3 inch crossover (if so, ask them about their snake oil special). The benefit to changing the crossover would be realized on the quarter mile track, in hundredths of seconds, but I don't believe that you'd feel a difference in day to day driving (anyone, correct me if you've experienced different). If you're looking for big gains in performance, look to replace/upgrade something that is more restrictive than the crossover.

How much would wrapping the stock or aftermarket crossover help performance?

Don't forget that wrapping will rot the hell out of your exhaust much sooner than would normally be the case

there could be an increase in performance. How much? Only a dyno test can say. I wouldn't expect anything over 1 hp, if that, but then again, I'm no dyno. Exhaust wraps promote rot, especially if salt is used on the roads you drive on. If rot weren't a factor, I might wrap mine.

It was suggested to me to NOT wrap the crossover pipe, as it decreases performance slightly, since you're holding the hot air in more effectively and pushing that hot air back in and expecting it to make power from that.

SnowDrift

Wrapping it or better yet having it coated with something like Jet Hot, retains the heat which helps drive the turbo. I doubt you would notice any power out of it but maybe a cooler under hood temp.

What is the 3 bar map sensor you are talking about bornready6.5? Haven't seen that one before.

I think he is talking about one of these:

http://store.summitracing.com/default.asp?Ntt=3+bar+map&Ntk=KeywordSearch&DDS=1&searchinresults=false&N=0&target=egnsearch.asp&x=21&y=9

These will work with our engines and give them more boost?

It allows more boost by lowering (resisting) the MAP signal. ECM is "fooled" into 15 psi+ without further modification, but without guages (boost, pyro) you're in the dark as to what boost you're running and dangerous heat levels.
1250*f =cracked piston crowns due to the thermal instability of aluminum at that tempature. ie it becomes brittle

Hey qm, would this work instead of (or better than) doing the 10k resistor mod.? Have you heard about using the 3 bar map before, for our motors?

The 3bar map would be better than just 10K ohms inline. No splicing, sodering or taping. If you upgrade to an aftermarket prom/reflash you might have to put the stock MAP back in, not sure on that.

When you guys get stuff from summit online, you should post a link back to posts like this and ask Summit to "check it out" and possibly become site sponsers.

The 3 bar map made a huge difference. I was running about 10-12 psi boost, then after installing 3bar, I hit 18psi and drop to a steady 15psi. Awesome. It also seemed to lower my egt's. I went with the 3bar because I drive alot between 2500ft. elevation and 8500ft and the map automatically adjusts whereas the resisters dont. Hey quantum...(or anyone) what is your opinion on the crossover...is it worth the time and money? My truck runs so well I really cant justify it unless it really does some good. I never thought of wrapping...that may be a good idea.

Hey BornReady6.5 What those VP Torsion bar Lift keys all about?

The 3 bar map made a huge difference. I was running about 10-12 psi boost, then after installing 3bar, I hit 18psi and drop to a steady 15psi. Awesome. It also seemed to lower my egt's. I went with the 3bar because I drive alot between 2500ft. elevation and 8500ft and the map automatically adjusts whereas the resisters dont. Hey quantum...(or anyone) what is your opinion on the crossover...is it worth the time and money? My truck runs so well I really cant justify it unless it really does some good. I never thought of wrapping...that may be a good idea.
I noticed the same thing with EGT's. Higher boost lowers them loaded or unloaded.

2.5" crossover ceramic coated inside and out ought to do it.

Cool...maybe one of these days I'll have to invest in one.....I suppose it couldnt hurt. I just wasnt sure if it was a must have or not.

The VP torsion keys replace the factory ones and instead of cranking the crap out them up to fit bigger tires therefore harshening the ride, etc. They reindex the torson bars like 2 inches while maintaining the factory ride and alighnment specs.
Never again will I just "crank" up the factory torsions without these things. Mine arent even cranked up that much and I can fit a 285 no problem.
VP is for Victoria Performance and I bought them off of E-bay for around $100.

You still got that link to them

Have a couple comments, or 2 cents, to throw at you all:

Bowtie and Bornready6.5 - I ran 285 Wrangler MTR's on my truck for about a year with no torsion bar adjustments or lift. Never had a problem with rubbing, even when I was off-road.

QM - I frown and discourage the use of ceramic coating INSIDE the crossover. I have heard a number of times that the ceramic started chipping and ended up in the turbo (take a guess what happened then!!!!). For our type of engines/trucks, I believe we would be at an even greater risk of this happening, due to possible off-road activity and extreme high temps. Ceramic is a very hard and dense material making it very fragile and brittle, especially when it's thin. Any sharp blow to the pipe could possibly cause the ceramic to break away.

I also don't believe it to be cost effective to worry about "treating" the crossover. It's only about 3 ft long and the volume of air flowing thru at such a high velocity, it's not going to cool the air fast enough to make a difference.

Again...just my 2 cents....

Hey bornready6.5, did you get the 3 bar MAP from summit or somewhere else? I am absolutely going to try this cheap and easy mod. I am around soldering all day and don't want to see it once I get home so if I can do the MAP and not solder a resistor I will be psyched. (part #)? Is it the same one that jac6695 pointed us to yesterday?

No matter how you adjust the torsion bars, keys or cranking the bolt, the lower control arm will move as a result giving you a higher ride height causeing the aligment to be off and needing to be set. Most use the keys because the adjustment is minor on the bolt so you can only go so high and the keys allow you to go higher.

No matter how you adjust the torsion bars, keys or cranking the bolt, the lower control arm will move as a result giving you a higher ride height causeing the aligment to be off and needing to be set. Most use the keys because the adjustment is minor on the bolt so you can only go so high and the keys allow you to go higher.So if you use the keys in the front. What do you use in the back? I want it up enough just to get the 285 on. The truck sits pretty level already.

More info. I've got mine jacked up all the way and I'm looking for a decent source for the drop keys.

Have a couple comments, or 2 cents, to throw at you all:

Bowtie and Bornready6.5 - I ran 285 Wrangler MTR's on my truck for about a year with no torsion bar adjustments or lift. Never had a problem with rubbing, even when I was off-road.


Again...just my 2 cents....
how wide was those 285's, 85,75, 60 or something else ?

bowtie,

285mm = 11.22 inches

SnowDrift

They were 285/75's. One of the best and most expensive tires I have ever owned. I was able to mount them right onto the stock rims.

I havent looked for the link to the torsion keys been getting ready to go on family vacation to Rocky point, Mexico. I am really going to test my truck pulling my 29 ft gooseneck travel trailer. This is my first time pulling that much load with all my new mods....cross fingers everyone.

I will work on those links.
And yes...I got the 3 bar map from summit.

Just for info. The torsion keys are available as a GM part. Here's a link that talks about it. http://www.fullsizechevy.com/fscu/fordkeys.shtml



Look for the GM part # below the last picture in that article. The keys on eBay are about $100. You can order them from GMPartsDirect.com for about $16 a piece (for the green keys).

Hopefully, next weekend I will get my keys changed out. Right now, my 245/75/16 Commercial T/A's barely clear the front. Also, search in google for "green torsion keys" and you can find a few more articles.

OK, I have to put them in, now.

bowtie,

285mm = 11.22 inches

SnowDrift
the tires width changes between 75 and 60's so without that 2nd number hard to know what ratio to figure it with.

the tires width changes between 75 and 60's so without that 2nd number hard to know what ratio to figure it with.
No. That first number is the tire width, no matter what the second number is.

The second number is the "aspect ratio". Multiplying the width by the aspect ratio gives the sidewall height.

The tire width shouldn't change between a 60 series and a 75 series. It may look wider due to the "square" look of a low profile tire.

The first number (285mm in this case) is the section width. The second number (75) is the aspect ratio, for example, this tire has a sidewall height that is 75% of 285- approximately 214mm. The next number of course is the rim size. So you can find the approximate height of the tire by add the sidewall height (214mm x 2), convert it to inches (16.83), add it to the rim size and you have a 32.83 inch tall tire.

on a metric tire, such as a 285/75R16 the 285 is the width in millimeters from sidewall to sidewall (approximately). 285mm = 28.5cm = 11.22 in. The tread width will be about 8 3/4" (rubber on the ground, but that doesn't show up, except for on a spec. sheet). The 16 is the rim size. The 75 is the percentage of rubber on the sidewall compared to the whole tire, which is why a "60 series" tire will, proportionally, have a shorter sidewall than a "75 series."

At any rate, the 285 width will remain approximately 285mm, whether it's a 75 or 60 series.

Uuhmm... ...I think we got off the topic - sorry guys

SnowDrift

sorry guys, we must have all posted that about the same time - didn't mean to reiterate what was already reiterated:o:

SnowDrift

:lol:OKOKOKOKOK already I got my numbers backwards. I got it already:lol:

I think we have the tires covered.:lol:


Now, back to crossovers........

I think we have the tires covered.:lol: Now, back to crossovers........
OK. I have one sitting next to me right now, collecting dust in my office. It's a nice mandrel bent one from FlowMaster. Someday I'll get it installed, but for now it's just holding the floor down.

Still :offtopic: ?

:lol:

is there anything else we need to cover on crossovers?

Ya. Is the crossover a good place to put a pyro gauge, since it is reasonably easy to get too?

its where mine is.

Tim

The company I am dealing with now said the crossover pipe is worth around 5 hp, and the prefered mounting place for the egt pyrometer is on the trailing side of the crossover tube kind of paralell to the transmission for protection.

EGT in the crossover I always thought that the downpipe was the perferred location

I was told crossovers do something about equalizing exhaust pressure in dual exhaust pipes..or something like that. Just wondering if this is true?? Dont know much about exhaust, so Im asking. This thread something about cooling exhaust..

If so, why is there times I see more exhaust out of my left pipe then my right?
Where would you put a pyrometer, since no downpipe?
Truck in question is the one in the signature.

1.- that is an equalizer tube, between the dual exhausts - stops the droning.
Crossover pipe in question is between driver-side manifold and passenger-side manifold, with single exhaust, required for turbocharger operation.

2. one dual exhaust has a vacuum\thermal operated heat valve betwen the manifold and the exhaust pipe, blocks the exhaust out of that side, so most exhaust gas from that side goes thru EGR passage in the intake, warming up the intake air for better drive-away, and cold-emissions control

3. install pyrometer in side without the heat valve, close to the exhaust flange.
Better yet, drill and tap that exhaust manifold for 1/4-20npt to install the probe.

4. the crossover pipe is in direct road draft - an EGT probe would not reflect accurate exhaust temps anywhere except directly adjacent the driver-side exhaust manifold flange - requires PRE-turbo EGT gage

5. just below downpipe flange is another good place for the EGT probe - requires POST-turbo egt gage

6. best place, imo, is the downward curve in the driver-side exhaust manifold between cyl#7 and the flange - gives accurate pulse on engine operation without benefit of exhaust crossover pipe cooling.

Thanks gmtc, I understand it a bit better now.
To clairfy I dont have the oem manifolds or the egr intake, i have headers instead. so I believe that heat valve you mentioned isnt there anymore...so thats why Im still stuck why my exhaust comes out of the left more then the right at times??...and where to put a pyro... I was thinking near the flange like you mentioned..but with the difference in exhuast wasnt sure if one was better then the other.

With the crossover you mentioned, for the 6.5 turbos with single exhaust, can you clairify? i thought after the downpipe it would just go exhaust from there on out, no crossover possible. And then for duals I thought it would be like Y pipe splitting it after the downpipe. Sorry, never seen under a 6.5TD truck. Looking to understand though.

left comes to right under the engine through the crossover and into the bottom of turboside exhaust, turbo sits on turboside exhaust, downpipe comes off the rear of it.

HEY GMCTD Explain for me the difference between pre and post EGT gages ?

Mine goes up to 1600 degrees, would the probe care where it was installed?

Good question, often asked.

The thermocouple sensor, usually Type-K, would be the same, pre- or post- turbo location.

It is the gage face that is different, for the Green - safe, Yellow - caution, and Red -too late operating range shadings.

Mostly, the Pre-turbo gage will be marked for greater full-scale temperature indication, but some gages just move the range shadings - those are the cheaper versions, usually with a Type-J thermocouple.

Type-J = ~1200deg, can be used to 1400deg max, requires J-type gage
Red and White - Iron and CuNi

Type-K = ~2300deg, can be used to 2500deg max, requires K-type gage
Red and Yellow - Ni Chrome and Ni Alum

ok my gauge has no color markings and the instruction talk about mounting in the down pipe. I have the Auto Meter pyrometer # 2654

Bowtie can you start a separate thread on EGT location good info here going to get lost if hidden in a crossover thread

As qm described, the turbo mounts to a flange on the top of the passenger-side exhaust manifold - the downpipe attaches between the turbine housing outlet and the exhaust pipe to the soot trap, thence to the muffler, and to the rear - single large (hopefully) exhaust pipe.

Driver-side manifold rear-exits to the crossover pipe, to the rear entrance of the passenger-side manifold, where combined left-bank\right-bank exhaust gasses exit thru that top flange thru the turbo to the downpipe and out.

Yep - missed that about your headers - that would tend to eliminate the exhaust heat-riser valve.
What is the indication of more flow thru one side than the other?

Just mount the pyro probe on any convenient exhaust port, inch or so from the flange.
Either of the back ports would offer most protection for the TC wiring, imo.

One easy method for a soft probe is to drill the header pipe so the probe wire just fits, insert it to 1/2 pipe diameter depth, fold the wire over, hose clamp directly over the hole/probe to secure and seal the hole.

You still got that link to them

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33585&item=7963847754&rd=1

sorry it took me so long.

Yep - missed that about your headers - that would tend to eliminate the exhaust heat-riser valve.
What is the indication of more flow thru one side than the other?

Just mount the pyro probe on any convenient exhaust port, inch or so from the flange.
Either of the back ports would offer most protection for the TC wiring, imo.

Thanks for explaining the concept of the turbo exhaust.

gmctd-you said the exhaust hopefully goes to one large pipe, is there a reason dual exhaust is impratical for turbos?

Also...recently the indication of more flow out the left exhaust then the right, is actually standing there watching some exhaust coming out, then walking to the other side and seeing none. Truck is warmed up, at idle.
Other times, and not always, but while driving under hard throttle I can see in the side mirrors more exhaust out the left, then the right again.
It doesnt concern me per say, but would be nice to know. Also, Im pretty sure there are no leaks on either side, and theres defente flow out the right, I can hear and feel it. Any ideas? Thanks

If its white-grey smoke, fuel isn't getting to combustion tempature in at least one cylinder most likely a glowplug/weak injector.

Black smoke might indicate fuel/oil at combustion tempature didn't burn completely.

The turbocnarger consists of an exhaust-driven turbine motor, which drives an air compressor, and makes power to drive the compressor via exhaust gas volume. heat, and velocity.

Generally, the exhaust output from both cylinder banks is required to drive the turbine, particularly at low engine rpm, where exhaust energy is low.

Your exhaust symptoms are of incomplete burn on one side, possibly due to weak injectors, or low cylinder pressure, or possibly a head was replaced, with the wrong pre-cups.

The Stanadyne DB-series Inj Pump-equipped engines became known as "smokeless Diesels" because of the precise fuel-metering at any rpm, along with the matched Bosch injectors.

You should not see any exhaust smoke or haze at idle, after the engine and exhaust system reaches operating temperature.

If the Inj Pump has been 'turned up', maybe yes, but both sides equal, idle or street rpm.

White fuel vapor or water vapor at cold-start, yes, moreso in winter climes, but should clear up when warmed up, and should be same both sides, with functional glow system.

Dirty air filter will also increase haze out exhaust pipes, but will do so equally, both sides.

So - you might have your injectors tested, and get a compression check, see if anything is amiss.

Thanks for the info, I will be looking into it.

i never considered that it could be an injector, since I thought i would be feeling a cylinder(s) missing?

didnt see how it could be a glowplug, since engine was hot and glow plugs are off of course, plus I changed all 8 out 2 months ago.

is there a way to check/ test to see which injector is taking a day off, by myself? I can do a compression test, i mean the injectors themselfs. Light gray smoke, by the way. Wouldnt surprise me to have a damaged injector, if you read the post in the 6.2L forum, this is the one that i got without a secondary filter.
http://dieselplace.com/forum/showthread.php?t=23653

And all this time i thought it could have something to do with the crossover...