The mk3 1.9L TD power-quest

[gldgti]

i already have the T3 - its the same as was delivered from factory on 1.6diesels from the mid-late 80's.

the total hp ability of the t3 is far above my needs (i doubt i'm going to risk 200+hp in my daily econodriver ) but the turbo should be just perfect - boost topping out at about 20psi (same as now) but with lots less backpressure and it wont work nearly as hard as the k1`4 does.

if i were to go any smaller, it would be to a frankenturbo k04-003 - inbetween the k14 and t3 really.

but im confident the t3 will suit my purposes just nicely.

[gldgti]

Well, theres been a few little things going on...

I've lately been fiddling more and more with the fuel settings on the pump, trying to minimise soot and keep some power - and i've basically cracked it with a midrange setting on the "boost pin" (adds fuel on boost) and carefully adjusted "smoke screw" (entire fuel curve adjustment).

Boost now peaks at 21psi at around 2700rpm, dropping off to about 15 psi at 3500rpm and 10psi at 4200. This is due to the governor (still stock) cutting in and spoiling all the fun - basically theres not enough fuel to make any more boost. this does however make for a clean and cool running condition - no smoke anywhere!
the only time it smokes now is off boost with a heavy tromp of the foot - quickly dissappears as the turbo spools up above 5-6psi... so she's really quote socially amicable now.

governor mod is something i really want to look at soon, as its basically the last thing on the list for this car.... apart from the T3 which is in the works


now, onto prettier things:

I aquired a triplet of nice new guages ex-ebay, from a supplier in SA. they are Racetech brand, made in taiwan. the guages came with everything needed for installation and are of very high quality, and work very very nicely indeed. stepper motor type - fully electronic with senders kept in the engine bay, so i only had to run wires into the cabin.

I got a boost pressure, oil pressure and EGT guage all for about $260. very impressed!

obviously, the EGT is the one i want to talk about....

EGT kit came complete with sender probe and all wiring, and i might add that its a very nice egt probe to install - just a good size (about 2" long with a suaged fitting so that you can adjust how far into your port it pokes.

i've mounted the probe into the EGR blanking plate that i made up for the exhaust manifold when i de-EGR'd the engine. it fits in nicely and basically sits right behind the exhaust port of no.4 cylinder.

I have found that the response of the EGT guage is pretty much instantaneous, and i have seen rises of 100degC/second, which i would think wouldnt lag much behind the actual temperature.

guage travel goes from 200C-1300C, with my own danger limit at about 750C. as yet i've not clocked anything over 520C, so i'm happy my "tuning" isnt having any negative effects on the engine.

hyway cruise at 110 keeps the guage on 200 (lower limit) which is great, and around town goes between 200 and 400.

i've also noted a direct and obvious difference with EGT and boost. more boost makes for lower EGT's in all scenario's, confirming the fact that diesels run cool and lean, rich and hot (opposite of a petrol engine). driving with a moderate boost leak (early this week i had a hose failure) i noted an increase in EGT's of about 50C across the board of driving conditions.

these observations are interesting in that it seems to make more difference to turbine temps that the mixture in nice and lean (more boost) than having a cool inlet temp (efficient intercooler). however ofcourse you'll get better efficiency andpower if the inlet air is cooler....

i'll also note that there is an obvious point where you have too much boost for the amount of fuel - as the power output suffers from larger compression losses. i see this when cuising at 0psi, and speeding up slightly so that the rev's go over 3200 and the automatic wastegating is disabled. if this happens, i get 5-7psi of boost but no extra fuel, and feel a small deceleration as the engine "loads up" with extra compression but no oomph. so, the ewasy way to tune for power is to go for a "light haze" of smoke - however this might be socially unacceptable, depending on how the people around you think. perhaps this is where the DPF came into being - allowing vw to run a tune that creates a small amount of soot (max power) and still have a slean exhaust.

anyway, pics of all the above things to come shortly.

[GoLfMan]

awesome mate

im a soot man, the more soot the better, especially infront of open topped convertables

[Preen59]

i've also noted a direct and obvious difference with EGT and boost. more boost makes for lower EGT's in all scenario's, confirming the fact that diesels run cool and lean, rich and hot (opposite of a petrol engine). driving with a moderate boost leak (early this week i had a hose failure) i noted an increase in EGT's of about 50C across the board of driving conditions.

Is that necessarily a hotter combustion temperature... OR...

Is it because when your engine runs rich, the charge is still burning as it passes across the exhaust gas temp probe?

It seems strange that with effectively less cylinder pressure you get a hotter charge burn.. And less pressure would equal a slower burn yes? Which would mean that what i have mentioned above could be correct?

All questions, not statements. Love to hear your thoughts..

[gldgti]

your right on track there preeny - indeed the charge burning through longer (continuing as it exits the cylinder) would logically be the reason i'm seeing higher egt's - but when i think about it in terms of the basic thermodynamics - if there's enough oxygen in the air charge to burn all of the fuel well before BDC, say, then more of that combustion heat works to expand the gas charge making torque.... as the gas expands, it cools down - so if everything's over early, i see a lower EGT.

i think the big problem (danger) with diesel tuning is running too "rich" for too long during the cycle, and not being able to convert that heat energy into expansion at the right time.

interesting anyway...

[smithy010]

im a soot man, the more soot the better, especially infront of open topped convertables

Hear Hear!

Doing Well Aydan. That's better than i can say for myself. Someone listened in thermodynamics class more than i did.

I like your theory, but i still see where Mr Preen is coming from. In more practical (but very picky) terms, if you have post-cylinder combustion, then you are more likely to get a bad reading on your EGT.

[Greg Roles]

Wow, interesting stuff guys. Have motivated me to get my own EGT finally hooked up and see what a computer does to the situation.

Awesome observations!

[Preen59]

your right on track there preeny - indeed the charge burning through longer (continuing as it exits the cylinder) would logically be the reason i'm seeing higher egt's - but when i think about it in terms of the basic thermodynamics - if there's enough oxygen in the air charge to burn all of the fuel well before BDC, say, then more of that combustion heat works to expand the gas charge making torque.... as the gas expands, it cools down - so if everything's over early, i see a lower EGT.

i think the big problem (danger) with diesel tuning is running too "rich" for too long during the cycle, and not being able to convert that heat energy into expansion at the right time.

interesting anyway...

Very interesting. We have found that to an extent with the kart engines. If you run them slightly on the rich side, in some cases they actually run hotter and you lose bottom end. (You have to remember that with kart engines, being direct drive, we are using an extremely broad RPM range, like say from 6500 to 15500.. So bottom end is VERY important.)

We found that is some cases (had to be a hot day), if we run a slightly rich mixture, the engine would get hot, lose bottom end and still not perform through the mid range or top end, and be very lethargic. You lean it off, the head temp and egt drops, the engine picks up bottom end, mid range and starts screaming again up high.

There's much, much more to them than that, but that was a case that we have encountered in the past with fuel mixture.

[gldgti]

I like your theory, but i still see where Mr Preen is coming from. In more practical (but very picky) terms, if you have post-cylinder combustion, then you are more likely to get a bad reading on your EGT.

sorry i think my post was a little unclear - i do agree completely that the rich scenario is making me see a high EGT, not necessarily a high combustion temp.

however if the piston is still being heated by the charge continuing to burn through the exhaust stroke, then over the whole cycle the amount of heat saturation would be larger - and hence piston temps would be greater. similar logic applies to the exhaust valves i think.

[gregozedobe]

We have found that to an extent with the kart engines. If you run them slightly on the rich side, in some cases they actually run hotter and you lose bottom end.

Aren't Kart engines 2 stroke engines ? (ie very, very different to 4 cycle diesels with compression ignition, valves and turbochargers)

I seem to remember burning holes in a piston or two from running 2 stroke motorcycle engines too lean for too long at sustained high revs (but I agree, more torque and power on the lean side rather than rich).