Let the tinkering continue.....

[Greg Roles]

i love all these little ingenious manifestations on your tdi!

i'm guessing the milltek/custom code DPF delete is going to end up somewhere in this car down the track?

good to see this updated

Only if it's bigger than stock. I want at least a 3" full system, given what I hope to stuff in the other end, 3.5" looked the berries at the exhaust shop.

I've only slowed down due to a lack of funds the last few months, I'm only working part time, but real job prospects are starting to look up, and GOD I've missed my tinkering!!!

I'll be back!

[Greg Roles]

Here's what drilling a hole in the top of your $5k DPF looks like. It's OK to drill, but tapping it....well that was a mission. My tap is cactus, but I managed a thread to hold my EGT probe, so we'll see if it stay's put under heat. Into the Intercooler spray now, just need to set up the controller box, which only turns it on at certain temps, and you can adjust the time it's on. With the heat finally coming back, this will be a great little mod for summer. Hope to get into the CAI to turbo plumbing this arvo, need to visit my Dad and get a bush lathed up. See how we go...





The passenger side headlight washer cover would be an unreal CAI inlet....hmmmmmmmmm

[Greg Roles]

Gonna have to use the stock MAF housing for now, so it doesn't underfuel, but then again, I wonder what "underfueling" is in a diesel??

Hmmm.

[Greg Roles]

Well my inlet is 100% dry and oil free, and ain't that a treat.

Downside is on the elbow just before the turbo I noticed some fine dust buildup, so I have to wonder if the Apexi dry is filtering OK, or if the fact I've washed it out twice in metho and used the compressor to blow it dry has damaged it. Either way, might be time for a new element.

Logzy and anyone else running a dry fliter, might be time to check the inlet, as with the stock oil digestion problem it's probably not something you notice, so please check between the filter and the MAF / oil slick for fine dust guys.

I'd put money on me damaging mine by washing it out. It looks fine....but yeah, time to go shopping.

The major upside is the stock MAF pipe inner diameter is 72mm, and the 3" pipe I'm planning on putting in is also 72mm inner diameter. Means I can just bolt the MAF sensor at the same depth, and I should have a stock MAF reading given the same surface area. Time will tell.

[Transporter]

Here's what drilling a hole in the top of your $5k DPF looks like. It's OK to drill, but tapping it....well that was a mission. My tap is cactus, but I managed a thread to hold my EGT probe, so we'll see if it stay's put under heat.

If it doesn't stay in. You could use the rivet nut; any good exhaust repair shop should have it. What size is the thread that you cut in?

[gldgti]

If it doesn't stay in. You could use the rivet nut; any good exhaust repair shop should have it. What size is the thread that you cut in?

thats waht i thought of too - they're really handy for that sort of caper!

Cog, will you be trying to rout your intake all the way over to the RHS?

[Greg Roles]

Nah man, the passenger side, and I'm dreaming of a nice fibreglass scoop from the headlight washer cover at the moment. The pic above is my intercooler spray side!

The EGT probe is from the USA, 1/8" I think... I'm at the exhaust shop this arvo, so I'll be sure to ask. I'd like it to be more secure than it currently is.

[Transporter]

Greg, if they don't have the rivet nut of your size, it can be easily made in lathe and riveted in.

[Greg Roles]

Well they had no rivet nuts, but I'll at least get a NPT weld on fitting if I can't track down a riv nut place. The probe seems to be fixed pretty well, so for the meantime it looks like it'll hold up to the heating cycles. I have my eye on it.

Interesting that in start stop traffic I don't even get a reading till I boost it, where it's showing between 200 and 300 degrees for normal driving. The only time I saw some decent numbers was a constant 90kph in 4th for a few minutes where it crept up to about 400. Little wonder my oil vapour isn't really getting burnt, but I can't smell it at all in traffic, and I've had the windows down and get a little diesel exhaust back in, so it's way better than total loss!

I can confirm that deleting the rear pancake muffler makes absolutely no difference to the noise, just returned from a mufflerectomy, and whilst I kept telling myself it was a little louder, well...it's not. On idle you'd never know, and obviously the DPF is muffling everything. Still it's nice to have ditched that massive muffler, and I'm sure Polar would be proud at the weight loss. I'd recommend the delete to anyone considering it, can't hurt, and once the DPF goes, should help no end. For you non DPF types, probably get a bit louder, but I'd still be doing it, as there's a resonator in there as well to stop any drone.

Man the 3 and 3.5" systems look the berries, and I'll be doing one of those at some stage!

[gldgti]

Well they had no rivet nuts, but I'll at least get a NPT weld on fitting if I can't track down a riv nut place. The probe seems to be fixed pretty well, so for the meantime it looks like it'll hold up to the heating cycles. I have my eye on it.

Interesting that in start stop traffic I don't even get a reading till I boost it, where it's showing between 200 and 300 degrees for normal driving. The only time I saw some decent numbers was a constant 90kph in 4th for a few minutes where it crept up to about 400. Little wonder my oil vapour isn't really getting burnt, but I can't smell it at all in traffic, and I've had the windows down and get a little diesel exhaust back in, so it's way better than total loss!

I can confirm that deleting the rear pancake muffler makes absolutely no difference to the noise, just returned from a mufflerectomy, and whilst I kept telling myself it was a little louder, well...it's not. On idle you'd never know, and obviously the DPF is muffling everything. Still it's nice to have ditched that massive muffler, and I'm sure Polar would be proud at the weight loss. I'd recommend the delete to anyone considering it, can't hurt, and once the DPF goes, should help no end. For you non DPF types, probably get a bit louder, but I'd still be doing it, as there's a resonator in there as well to stop any drone.

Man the 3 and 3.5" systems look the berries, and I'll be doing one of those at some stage!

on the EGT's:

i too see similar temps. i've tuned mine to enough boost such that it never sees more than about 550C on the EGT's (like as hard as it can go up a good hill accelerating to 110km/h). however, lately i've been having problems with my electronic wastegating crap, so often i have my wastegate fully open until 3200rpm when somewhere else in my engine mangagement tells it to open. with this case, i've been able to look at my egt's with now no boost doing the same kind of loads as with boost, and gee is amazing how much HOTTER the exhaust is with no boost. cruising up a big incline, if i hold it at 3100rpm (no boost) it'll creep up as high as 450C, and if i force it over 3200 and so get an instant 20psi, the EGT just falls away to about 380C!

on the exhaust size - what rout does the exhaust take with respect to the rear suspension on the mk5? on mk1-4, the rear axel beam kinda restricts the largest you can go to 3" (if your VERY GOOD at making exhausts) and 2.5" for normal people. just wondering if you'll be able to fit 3.5" in there?

on a sidenote, i reckon 3.5" will be sooooo big. cool, but big. hotted up cummins 6.3l and ford powerstrokes hardly ever go more than 4"

[Greg Roles]

Good point, but you can always do a twin section over the axle. The difference for a full system in 3 then 3.5 is stuff all, so why not go nuts? You want as little restriction after a turbo as possible afterall, and there's plenty of room in the MKV, but I'll check the rear part tomorrow when I have a closer look at today's surgery.

I could always put another 2.5 in, and make the twin tips real..hmmm. Would weigh a lot I guess.

[gldgti]

yeah, i understand - you figure 3-3.5" price difference is negligible (materials wise) but it seems to end with whats practical with our small cars - unlike a commodore where you can fit whatever you like under it :-P

anyway, just my 2c. if i were you, and could easily do a 3" or 3.5", i reckon i would

[oracle1]

dont go too hard

I read an interesting post in a forum about a guy who changed his exhaust from 2.5 to 3 on a six cylinder turbo diesel cruiser who dynoed before and after, the difference was negligible some 2-3 horsepower with a large increase in the drone in the cabin. The 4.2 compared to 1.9 is more than double in capacity, and most 4x4 are running 2.5 to 3 inch systems, I wonder if any more than 3 is really going to give much gain in horsepower, I surmise it might help with the temps in the exhaust.

[gldgti]

I surmise it might help with the temps in the exhaust.

possible i suppose - in order to do so, it would have to realise a greater pressure drop on exiting the turbine.... but theres a trade off with velocity there. if it slows down too much, the static pressure increases... might even be harder to move the exhaust out... i dunno. i think a CFD model would sort it out... why didnt i do that for a final year project ???

there ya go - anyone reading this doing 2nd or 3rd year mech eng degree - for your FYP in 4th year, how about doing a "computational fluid dynamics analysis of a the flow efficiencies of a constant mass flow of exhaust gasses through variable cross sectional area pipelines?"

[Greg Roles]

Lots of variables there.

Firstly, all but the most modern 4x4's put out really pathetic HP. 3L and 4L TD's 4x4's from the 90's pump out figures around 90-120hp at the wheels, from what I've seen on several dyno printouts. You need to remember that until very recently diesel engines were indeed the weezy items everyone considers them to be. With a lot of tweaking you can get them motivated, but the current modern hi-po oilers are a very different beast. Far better flows, design, and big turbo pressure stock, makes for a lot more exhaust flowing out the other side. 3" may indeed be enough, but if VW saw fit to use a 2.5" mandrel system stock, upping the boost, adding other powerups etc is going to require more than the stock exhaust. Even just ditching the DPF may increase the flows enough, time will tell.

Add to that I aim to be putting a lot more into it as well, so it's all part of a cunning plan. More in, more out, the same old formula.

An increase in cross sectional diameter will obviously lower the resonant frequency, and that's where the correct choice of resonator comes in. Most drone occurs in the 50-500Hz range, and given the specifics of the diesel engine, you can't just wack on a big jap or petrol resonator and expect to get it right. Add to that that a lot of resonators are pretty much just mufflers and you see how easy it would be to get wrong.

If and when I go silly, it'll be with a specifically chosen diesel resonator, and even then it'll probably take some experimentation to get it right. Which for me is the fun bit!

I'm still sticking to the basic truth that you can't have a low enough restriction after a turbo, and back pressure doesn't help in any way whatsoever apart from lowering noise.