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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 valve!).

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 becomes:-

1. Measure exhaust gas temp under significant load in standard tune,
2. Increase Boost (which will lower temps on a turbo diesel, unlike a petrol),
3. Increase fuelling, again measuring temp under significant load,
4. keep adjusting fuelling until exhaust gas temps are back to normal.

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!

Grant McAuliffe

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.

Ron Engelhardt

Diesel Performance Tuning 3

I have been following your Pug Diesel tuning journey.

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 Parts.

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 screams!

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 again.

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 ECU.

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 value.

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 ECU.

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 tuning ours.
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 boost.
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.
He also 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 405's)
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 turbo.
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 help.
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.
Dave Crabtree
United Kingdom

Human Powered Trike

Trike Project was great. Keep up the good work.

John Fritsche
United States

Praise 1

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.

Wayne Kever
United States

Praise 2

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!

Russell Elliott
New Zealand

Skyline Intercoolers

Re: Julian Edgar's article "DIY Budget 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.

Click for larger image

Some 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.

Click for larger image
Still 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 article.

Thanks for this great website!

Patrick Antoskiewicz

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