Exhaust

[fester]

Couple of little issues in this too. Articsoldier I'm not sure where you cut and pasted that text from but I'd like to know the source and what fuel they were referring to. A turbo diesel IS on boost all the time. It may not be on max boost all the time but tend to be on meaningful boost far more often than a petrol. I don't have a boost gauge on our Challenger but I do on my Patrol and between light throttle around town to light highway cruising I'm making anything from about 5 to 10 psi with a 15psi max.

I've mentioned size before and questioned whether any of these exhaust makers actually have test data to back up the ideal size. The other thing to consider with something like the Tiapan system is the thermal dynamics of airflow. I'm not sure I believe their claims that the air diverted over the baffles in their special muffler increases airflow by heating the air that far down the line and pretty much every turbo muffler is just a perforated baffle and would therefore do the same thing. Their design of starting at 2.5" through to the flex joint then upping to 3" for the remainder is flawed. In theory the system should be the opposite stepping down towards the back. As exhaust flows it cools. When it cools it contracts. When that cooler contracted air hits a larger pipe size (or is contracted within the same larger pipe) it has to slow down and spread out to fill the larger void before it can return to the same flow. At this point the turbo is again pushing against this slower airflow so ideally the pipe diameter should reduce at that point to enable the air to maintain full velocity.

The other thing that is being overlooked here in the Challenger specific application is the ECU's inability to quickly control overboosting when the system is opened up, hence the theory of "as little back pressure as possible is good and less is better" is negated, if the control systems can no longer maintain stable boost within original tolerances.

[Arcticsoldier]

Yup turbo diesel is on boost given that the engine has a short rpm range. Most turbo diesel have variable vein turbo to aid boost at lower rpm. The info I posted above is referring to petrol but the concept of exhaust size for gas flow is same. Yes turbo engine will flow more hotter gas. Like you I also question manufacturers research as you can see online they'll seem to be selling 3" system for different displacement turbo diesel engines. Some will sell smaller diameter system's. I would like to see graphs comparing 2.5 2.75 3" exhaust system but haven't seen any for diesels just yet.

http://www.mrtperformance.com.au/performance/engine/1274-Mitsubishi-Challenger-25-Turbo-Diesel-engine-performance-guide

Just as a guide but useful info.

[littleriver]

Dyno runs are alway's ran at full load meaning full throttle. When I say load I mean 100% throttle. The tuner will the adjust fuel, ignition, timings etc.. at different loads. Dyno graphs show max hp/torque @ 100% load over the rpm range. Let's say for example at Im accelerating at full throttle from 1500rpm, turbo spools up to max and gives me 20 psi and a reading of 150hp at 4500rpm. Now if I did the same at 50% throttle the turbo might only spool up 10psi (again this is example) the dyno graph numbers would look different.

x2 on dyno runs when measuring torque and horsepower 100% fullthrottle ...

there is a lot more to the tuning the vehicle on the dyno... ie. measuring and monitoring many variables (air,fuel,timing,pulses etc.) and a reputable dyno shop will spend many hours on your vehicle measuring at different rpm's (at different throttle percentages) from idle up to redline to get that best possible air/fuel ratio (but you get what you pay for, as may take all day for the perfect tune).

so a tune to the exhaust is essential for best results and agreed it's really what the customer is after (and can afford)

[rotare]

Since you guys seem to be roo system fans, here's what they have to say about exhaust systems:

There are essentially 4 common sizes, 2 1/4, 2 1/2, 2 3/4 and 3″. Most standard exhaust systems in the diesel 4wd are 2 1/4.

2 1/2″ is common with exhaust companies who either specialise in or have a past experience in petrol naturally aspirated motors. The most Common misconceptions from people who recommend 2/12 is the any larger and you will not have enough back pressure in the exhaust.

The fact is forced induction Diesel engine are not as sensitive to back pressure as naturally aspirated engines are, on top of this more than enough back pressure in created by the turbo housing and factory manifold. This negates any concern about a large exhaust in regards to back pressure.

2 3/4″ exhaust systems have been made popular by Beaudesert exhausts. These systems are a compromise between the 2 1/2″ and 3″ systems.

This brings us the to Roo Systems exhaust of choice. 3″ exhaust systems on a turbo Diesel engine give you the best possible performance all round. 3″ enables you the option of getting the most out of the turbo diesel with a chip or simply giving you the benefit of better economy and lower EGT’s if you choose not to chip your 4wd at first.

A 3″ system gives you the best possible environment for the turbo to spool freely allowing the engine to draw in more air and allowing for the boost to come on sooner. The combination of this makes for a noticeable drop in turbo lag.

http://getgoodgear.com.au/roosystems_exhaust/

Perhaps someone should let roo systems know their logic is all wrong, and a 2inch or 2.25inch exhaust is better for low down torque on a turbo diesel

[Arcticsoldier]

Not a fan of roo systems, just pointing out they did a back to back dyno run in the video they posted. Again you seem to have missed the problem here. The challenger is 2.5 so if people says 3" is best all round for it, great. They done r&d. So for my pajero 3.2 would I need a 3.25" or 3.5" because I have a .7ltr of more displacement?

Op wants a bigger exhaust. Roos recommend 2.5 instead of 3 due to droning noise which can be sorted with extra hotdogs but that would mean a custom exhaust if they have to modify their existing product.
Stock exhaust for challenger is 2.25. Replacing the stock exhaust with 2.5 may not sound like much but having a exhaust with less bends and kinks, better flow muffler and catalytic converter is pretty much it. Going larger to 2.75 or 3 still yield gains but how much more benefit will it have for OP driving needs?

[littleriver]

Not a fan of roo systems, just pointing out they did a back to back dyno run in the video they posted. Again you seem to have missed the problem here. The challenger is 2.5 so if people says 3" is best all round for it, great. They done r&d. So for my pajero 3.2 would I need a 3.25" or 3.5" because I have a .7ltr of more displacement?

Op wants a bigger exhaust. Roos recommend 2.5 instead of 3 due to droning noise which can be sorted with extra hotdogs but that would mean a custom exhaust if they have to modify their existing product.
Stock exhaust for challenger is 2.25. Replacing the stock exhaust with 2.5 may not sound like much but having a exhaust with less bends and kinks, better flow muffler and catalytic converter is pretty much it. Going larger to 2.75 or 3 still yield gains but how much more benefit will it have for OP driving needs?

As above - Roosystems seem to put a lot of time/money/effort into there Research and Development (as possibly other reputable companies do) - they need your vehicle for the day to tune ... where the others may need for couple of hrs ... tuning is best done on dyno.

some other products/franchises just install a chip with a preloaded map which may not suit your vehicles/customer needs"as mentioned above" (some of these maps may be from different contents of the world - different altitudes, climates etc.) even from say state to state the air may become more denser resulting in a different tune (but there is a happy medium that the big boyz can set the vehicle to suit each country/state).

When we first purchased our Challenger back in 2012, we went into local exhaust shop (owner in the business the last 25+ yrs), He also quoted he wouldn't go bigger then 2 1/2inch ... maybe on a 3L or bigger he would go up to 3 inch.

As at this present time there is not a huge market for our challengers for after market exhausts - it's better to possibly look at a triton 2.5L exhaust to match with a few mods. (yes with the autos you need that extra hotdog) ... Very similar motors but the ECU parameters can be altered substantially more on the challengers then the tritons (I have seen Tritons with more torque but less horsepower) as the triton is more of a work horse.

NB sorry if we seem to be repeating ourselves bit like a scratched record

[littleriver]

Here's a clip from TaipanXP with 3 inch system fitted ...

https://www.youtube.com/watch?v=x7G7LWRvRPE

also their website

http://taipanxp.com.au/mitsubishi-pb-2-5l-challenger-rd-vehicle-needed/

...

[littleriver]

Beaudesert exhaust 2 3/4 inch exhaust on Triton MN

https://www.youtube.com/watch?v=i9j76adYQ2M

[fester]

So lets get back to the real world. I nearly hit the buy button on a cheap 3" Triton system for $520 delivered with 200 cpi cat and proper muffler. However my concern is who has a 3" and properly tested it out to make sure the turbo doesn't overboost and trigger a limp condition. For towing or heavy beach work this is a real concern. There is no point even discussing 3" if this is the case regardless of what is generally accepted.

[littleriver]

unknown manufacturer
2.5inch exhaust from cat back MN Triton

https://www.youtube.com/watch?v=hS57aA1Va-o

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[littleriver]

So lets get back to the real world. I nearly hit the buy button on a cheap 3" Triton system for $520 delivered with 200 cpi cat and proper muffler. However my concern is who has a 3" and properly tested it out to make sure the turbo doesn't overboost and trigger a limp condition. For towing or heavy beach work this is a real concern. There is no point even discussing 3" if this is the case regardless of what is generally accepted.

I am sure the tuning shop will match your exhaust what ever size you choose to it's programming so as not to throw fault codes ...
as the boost control is regulated electronically by ECU


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[shortSteve]

I am sure the tuning shop will match your exhaust what ever size you choose to it's programming so as not to throw fault codes ...
as the boost control is regulated electronically by ECU


...

The problem with the overboost is with a large dia exhaust the ecu can't stop the turbo from spinning too fast quick enough, causing it to overspeed and possible damage/destruction.
This is fairly isolated, but something to be wary of if going for a bigger straight through system.

[littleriver]

The problem with the overboost is with a large dia exhaust the ecu can't stop the turbo from spinning too fast quick enough, causing it to overspeed and possible damage/destruction.
This is fairly isolated, but something to be wary of if going for a bigger straight through system.

does the waste gate also open to prevent this ?

[fester]

There is no waste gate on a VGT turbo. The boost curve is controlled by adjusting the profile of the vanes in the turbo housing. Yes it is controlled by the ECU but as shortsteve just said and i posted several posts ago, the MM ECU cant act fast enough and people have been seeing the boost spike to 30 + psi.

Even with moderate boost spikes the ECU is seeing figures over whatever max boost is and if that is held for more than 8 secs it triggers a limp mode and CEL with codes. Apparently cides that can't be cleared without MUT. Guys are driving around it by feathering the throttle every few seconds. Seems to present itself when guys start towing as that is the most likely situation with sustained high load, high boost. I'm guessing sand could be the same.

What i don't know is how prolific this situation is. Will it effect all 2.5's but be lying stagnant till they hit that load situation or is it adhoc like the EGR blanking plate.

I was all set to put a cheap 3" on before we tow at Chrissy as i don't have time to make one but it could potentially make our towing issues even worse.

Not sure i want the hassle and cost of a Dawes valve set up just to redress an issue created by the exhaust.

Id like to try modifying the standard cat to 3" in and 2.5"out to see how this goes but a $500 3" exhaust is appealing.

Would loveto know if people have been in those load situations without issue with 3".

[shortSteve]

There is no waste gate on a VGT turbo. The boost curve is controlled by adjusting the profile of the vanes in the turbo housing. Yes it is controlled by the ECU but as shortsteve just said and i posted several posts ago, the MM ECU cant act fast enough and people have been seeing the boost spike to 30 + psi.

Even with moderate boost spikes the ECU is seeing figures over whatever max boost is and if that is held for more than 8 secs it triggers a limp mode and CEL with codes. Apparently cides that can't be cleared without MUT. Guys are driving around it by feathering the throttle every few seconds. Seems to present itself when guys start towing as that is the most likely situation with sustained high load, high boost. I'm guessing sand could be the same.

What i don't know is how prolific this situation is. Will it effect all 2.5's but be lying stagnant till they hit that load situation or is it adhoc like the EGR blanking plate.

I was all set to put a cheap 3" on before we tow at Chrissy as i don't have time to make one but it could potentially make our towing issues even worse.

Not sure i want the hassle and cost of a Dawes valve set up just to redress an issue created by the exhaust.

Id like to try modifying the standard cat to 3" in and 2.5"out to see how this goes but a $500 3" exhaust is appealing.

Would loveto know if people have been in those load situations without issue with 3".

Yeah, I got same info as you. After reading a bit more, seems "less" likely if you still run a cat and mufflers (even in 3 inch), but those with straight through systems MAY have more issues. In saying this, there was a guy on newtriton.net that had issues with his as standard. Again, seems more autos than manuals (due to lifting to change in a manual), and at higher road speeds and when towing, eg: overtaking at country speeds with full throttle. Definitely a light feather of the throttle will help prevent. I run an auto pc challenger, and have seen just over 22psi (22.1iirc), would got straight to high teens, then climb to 21, and that was usually it, but have tripped my guage max (set at 22psi) only once. On my tuned Triton, would regularly get high 22's and up to 23, with usual max around 22.5psi. Nothing ever higher though. Both cars have run Beaudesert 2.75" systems with cat and sports mufflers.

sS