Diesel Performance Tuning 1
Great to see you getting into the turbo
diesels. I've got an aftermarket turbocharged Maverick that has copped the Audi
DiY boost control (10psi at 1500rpm, courtesy of the pressure relief
A quick one on adjusting the fuelling level on diesel powered
cars. Richening the mixture on a turbo diesel has a significant impact on
exhaust gas temperatures. I've got another autospeed project (or rather,
Performance Electronics for Cars) monitoring exhaust temp, and used this to tune
the car post boost control.
I'd recommend anyone that is considering doing the
same thing gets an exhaust gas temperature gauge installed (or a thermocouple
and do your tuning with a hand held multimeter). Even a small adjustment on the
fuel enrichment screw is enough to send the temps skyrocketing, and if you're
not careful you can end up doing serious damage.
The procedure then
1. Measure exhaust gas temp under significant load in standard
2. Increase Boost (which will lower temps on a turbo diesel, unlike a
3. Increase fuelling, again measuring temp under significant
4. keep adjusting fuelling until exhaust gas temps are back to
Yep, less power than your method, but probably a safer
alternative. Note that my fuel pump doesn't have a boost compensator, which
makes my exhaust gas temps a lot more sensitive than yours would be. Mind you,
with significant black smoke, I'm willing to bet that yours would have been
getting up there too!
Diesel Performance Tuning 2
Excellent articles on the Peugeot Diesel
stuff, best explanation of pump adjustment that I've seen. I've got a '92
Jackaroo with a 3.1 diesel and I've had a Dieselgasaustralia LPG system put on
it which makes a world of difference. 20% more power and 30% less diesel used,
comes onto boost earlier and is smoother. But now I may start tinkering with the
pump as well.
Diesel Performance Tuning 3
I have been following your Pug Diesel tuning
In your latest article: Issue 460: "Our Peugeot
Diesel - Part 5 - Final Tuning of the Injection System", I have some points of
interest that you have not covered or explained in this and previous
You have not covered how or if the Car's ECU is working with the
Engine, monitoring levels and temps and controlling fueling and wastegate etc.
If so then can your ECU be scanned for codes? Have you checked if there are any
ECU logs that report faults or out of range values and puts the Programming Maps
into a fixed Limp mode value?
Example 1: I had a Fuel Temp sensor die
inside my TDI fuel pump. . It did not click what was going on till I bought a
scanning tool andfound the Fault Codes and l did some logging. The ECU reverted
afixed Fuel Temp Limp mode value of +23degC, which is within anormal realistic
operating range... but as a fixed value the ECU could not calculate the correct
fueling, as temperature of fuel changes the fuel density and this affects amount
of fuel injected for optimal combustion, so depending on a cold quick runs or
long journeys, my car ran well or a bit off. Now It was only slightly and not
really noticeable until I drove on a really hot day and thecar was a lot
sluggish than normal.
Now I was lucky... I have read in forums of some
users who have crappympg and degraded performance and found that the Fuel temp
sensor died and the ECU using a Fixed Fuel Temp Limp mode value out of a normal
range. Some have seen limp mode values like -20 degC in the US on a hot summers
day and this makes the car run really lean and diesels don't run well when lean
(as the ECU thinks the fuel is denser than it really is so it injects less that
it really needs resulting in less power). Others had high values like +50deg C
and just smoked really bad.
Example 2: I have disconnected the boost hoses
from the ECU controlled wastegate valve and installed a manual fixed pressure
valve set to ~18psi. Now my ECU throws codes as it is out of expected range and
I do not know how the ECU is affecting my Fueling, mpg etc but she still
In Some newer cars the ECU can treat this out of range
measurement as a major engine fault and to save the engine from breakdown, the
car goes into total limp mode. Resetting your modification will not reset the
limp mode and the Codes have to be cleared before trying any modification
What I'm really getting at is that the ECU program for your car is
fixed but the mechanical tuning of Fuel Pump and Boost is set at the factory to
comply with final engine emissions. If you play with the Mechanical tuning like
you have, and the ECU "throws a code" as you are out of range for some component
value, then the ECU can revert to a Limp Mode value and all you are doing is
tuning a flat ECU tune that does not take any variable values.
I could be
wrong as the Pug's engine might be set up completely different to mine and only
relies on mechanical close loop monitoring of operations. My car has a timing
belt driven Bosch Electronic VE Fuel Pump and is Drive By Wire through the
I suggest you take a look at if you car can be scanned for codes.
This way you are not tuning an out of tune car once you reach an out of range
Also if you are going to play with diesel fueling you should make
a warning to readers about diesel over fueling and rising EGT's (Exhaust Gas
Temps). Some people might prefer the new found power over a bit of extra soot.
Overfuelling has the potential of quicky burning up turbos - especially when
climbing hills or carrying weight in the car.
The Peugeot 405 SRDT does not have an
Diesel Performance Tuning 4
I notice your 405 Td tuning exercise has gone
quite well. Onto the 5th article already, I can't remember seeing the others so
having a read up now. Your latest article (5th) appears to end up where we did
Fuelling alone can see 0.9bar > 1.2bar turbo boost
changes, before you touch the wastegate. I remember when we tuned ours we could
often get strong top-end power with little smoke, but left with not much boost
around 2000rpm and that made it smokey.
Sometimes the car felt really torquey and
boosted nicely, but felt really poor at the top end of the revs, finding the
sweet spot of balance really was a tough process. I ended up driving around with
a screwdriver and spanner to make the boost compensator and overall fuelling
screw adjustments out on the road, and just stopping every now and again in my
daily driving to tweak it.
I also noticed even on a dyno dynamics
roller the ramping was too fast to allow full boost. My brothers TD 306 seemed
to do the same when we went to a local Dyno Dynamics road almost two years ago.
The G-tech Pro RR showed a decent push at around 2500rpm (g readout) but on the
dyno the torque was peaking at 3000rpm, way later than it felt. The curve
represented what you might feel driving hard from a standstill in 2nd gear and
accelerating beyond the turbo's ability to speed up and deliver
Even my Hdi 306 suffered here at the more recent dyno (Dyno
Dynamics but a different new location closer to home). I asked to start the run
at 1200rpm to get a clear picture, but it seemed to lag badly and had a poor
torque peak value. He ran the car starting at 1500rpm the second time and it
gained over 15lbft and peaked a few hundred rpm sooner.
Interestingly, a Hdi that had been tuned with
a big intercooler and using the same ECU map as me, but with more higher rpm
fuelling, made about 150lbft of torque at 2000rpm where mine was making around
190lbft, and it made it's peak up near 3000rpm, 500rpm later than mine. On the
road however, in 4th from 40mph, he pushed me along right upto 80mph with a
passenger in his car.
I feel that the dyno ramping is still an
issue. I now prefer to just do before/after curves through 4th gear with my
G-tech. I can really see where the changes are.
Going back to Td
tuning, if you still are interested, my brother knows a fair bit about these
engines (he tunes 306 Td's now as a hobby/part time living, not so many nice
405's around in the UK now)
He has just fitted a custom downpipe with
decat with a large stainless steel exhaust. It sounds pretty impressive for a
diesel, standard sounding until the boost rises and then it makes a lovely deep
insistent growl, but best of all the time from applying wide open throttle to
what feels like full boost has been greatly improved.
fitted the Bosch pump that you use. All 405's in the UK used this pump, and the
early 306's, but by 97/98 or so the 306 went to a Lucas pump. Likely cheaper,
inferior injection pressure, and much harder to tune with less control over all
aspects of fuelling.
His car is a 98 model, so he used a 405 pump and the
late 306 small turbo, decatted, with a stock intake system (the 306 system looks
a little more improved vs the one on your 405, which looks different to our UK
I think I mentioned before, but the late turbo's are a good
improvement. The GT15 or K03, as found on the Hdi90 model 406's and 306's, also
came on very late Td 306's in the UK. They boost up a good 500rpm earlier, and
although their peak flow is limited vs the bigger earlier turbo's, the balance
seems better fitted to the engines.
We are hoping to go do some G-tech runs
in the near future, so I will try remember to post our results up and I'll send
a link over.
I've weighed my 306 and it came in at 1131kg, and I
know that the 405's were around the same weight, and just as a rough guide, my
brothers car will stay ahead accelerating hard through 4th up long hills to the
end of the gear, and my car ran a 9.3s to 60mph on my G-tech, and is around
115bhp. I'm sure there is more to come from your 405 Td with the earlier
Also worth noting is that the 405 and 306 intercoolers are subtly
different. One is shorter (side to side) and deeper, so experimentation here may
Also, the intercoolers get rather full of gunk. I cleaned one out
recently after removing the plastic tanks, and the internal cross-section must
have been 50% oily gunk.
Good luck with the project, and great
write up :)
I will show my brother at the weekend, he will be very
interested too... almost makes me want to buy an older Tdi to tune up now (my
brothers Td makes me wish I'd bought one instead of my Hdi, learning the mapping
systems is a real pain, thought ultimately it is better), for me the Td engine
is a peach compared to the Hdi, which although technically better in many ways,
just never feels as alive or as eager as the Td.
Human Powered Trike
Trike Project was great. Keep up the good
You guys are terrific! I love the
budget-oriented features, and the way you show real people in home shops
building projects. All the US magazines do everything in sterile
million-dollar facilities using expensive stuff from their advertisers.
Thank you for showing the rest of us what we can do.
hey this site and the information is great.
have been worried about the electrical side of motors for a while and stumbled
onto this site in a search session. awesomely informative with good examples of
application. Thanks again-Brilliant!
Re: Julian Edgar's article
Intercooler Fitment" Great
article was very interesting to read!
In regards to the rb25 smic costing $200+ The R34
GTT rb25 SMIC is a hard to find, sought after intercooler upgrade. As they can
handle up to 230kw atw, they are a great cheap upgrade. Private sellers usually
sell for $100-$150 mark They bolt on directly to R33 gtst's and with a simple
modification can be made to fit r32 gtst.
specs of the side mount intercoolers;
Length: 205mm Height: 190mm
Width: 60mm Volume: 2337cm^3
Length: 205mm Height: 220mm Width:
80mm Volume: 3608cm^3
Volume difference of 1271cm^3
Therefore; R34 smic is 54% larger than the R32
smic (relative to the r32 cooler)
Installation on my r32 only took a
couple of hours and the results were worth it! Dyno run was done BEFORE the
installation and straight AFTER in the same day to remove any factors which
would alter the results.
have stock ECU running on standard boost (10psi) mods to car; catback exhaust
and airpod. My friend who also got the smic put on his stock r32 also gained
extra 10+kw atw. As you mention at end of your article, a lot of people are
saying FMIC is the best choice, but that requires cutting holes, trimming
reobars etc which make it a hassle.
In the new year, will be looking into
the water spray kit for the SMIC along with the FAN idea you mentioned in the
Thanks for this great website!
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