Make your NA diesel (non-turbo) a faster car

[malone]

Introduction

Make your NA diesel (non-turbo) a faster car - an oxymoron? the impossible? Not really, NA (naturally aspirated) diesels can be modified to move a bit quicker than stock.

If you have any questions or suggestions regarding this post, feel free to contribute!

If you're confused by some acronyms like EGT, WOT, NA, etc., then open this page to decipher the acronyms.

Basic Performance Concept

By increasing both airflow and fuel flow through your engine you'll gain some power. Increasing airflow in a turbo diesel is most commonly done by increasing turbo boost, which is easy and inexpensive to do. Increasing airflow in a NA diesel is however limited or costly. Don't fret, there's still room for improvement in NA diesels.

It is possible to gain power by just increasing fuel flow (with nothing done to airflow), however that will potentially increase exhaust smoke and also increase EGT (exhaust gas temperature). Higher EGT indicates higher temperature in the engine internals.

Rule of Thumb

The exhaust smoke should not be more than a light grey haze. Too much smoke may indicate high EGT... not a good idea unless you have an EGT gauge to keep an eye on. Note: ULSD is becoming more common and it reduces visible exhaust smoke so it can be deceiving. The maximum safe EGT for an NA diesel might be 1,400 degrees F. The maximum safe EGT for turbo diesels is around 1,600 degrees F (measured inside exhaust manifold) because they have different engine components that tolerate more heat from turbocharging. Piston cooling oil jets is one feature of turbo diesels. An EGT gauge is not required for virtually all airflow enhancements and some fuelling enhancements.

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The following topics are covered: Maintenance • Airflow • Fuel • Chassis/Other • Big Power

Maintenance

1. Do a compression test. It's nice to see how healthy the engine currently is. Higher compression makes a noticable difference in a NA's peppiness.. turbo diesels not so much (while under boost).

2. If the fuel injector nozzles are old and worn, then replace them or pop-test them if you can. New ones will restore power, economy, and reduce smoke (from improved fuel atomization).

3. Use decent oil, ensure that the headgasket or any engine seals are not leaking, etc. Generally, the engine should be in good condition before you begin modifying. Any VW Tech or mechanic familiar with VW diesels can do a check up. I'm going to stop right here because this thread is about power enhancements, not how to maintain a stock diesel.

Airflow

All airflow upgrades mentioned here are safe and will not increase engine temperature (indicated by EGT).

1. The exhaust manifold upgrade that VW 8v counter-flow gassers have will fit any 8v NA diesel as well.

2. Make sure the air intake filter is clean to ensure no restriction in the airway. If you're curious enough (I haven't personally tried this), you can install a sensitive vacuum gauge between the air filter and the air intake runners to see how much vacuum is produced from the engine trying to suck in air. Less vacuum is better.

3. Many intake piping I've seen stop short, so install intake piping like this for a better cold-air / ram-air effect. It may not suddenly increase power, but it can decrease smoke a little on the highway. A recommended mod because it's inexpensive.

Click image to enlarge

Note: Not all setups shown above are optimal, they just show different designs. When building a cold air intake, consider the following: 1. Place the inlet where the coldest and strongest airflow might be found i.e. in front of vehicle and 2. Minimize intake heat soak generated by nearby hot sources, like the radiator. Heat soak can be reduced using heat shields.

4. Camshaft upgrade from Colt Cams. This seems to work well in turbo diesels, but I haven't personally seen results in NA diesels.

5. Port & polish intake and exhaust ports. It's fairly labour intensive or costly, but if the head needs to be removed for a headgasket replacement or a rebuild, then it may be worth getting a port & polish job done.

Fuel

1. See fuel injectors under Maintenance. Safe for EGT with no change in airflow

2. Advance static fuel pump timing. On 1.6L turbo diesels 1.05mm is the ideal advancing spot, but the NA diesel fuel injectors have a lower breaking pressure (NA 130bar vs. TD 155 bar) and I can't recall the optimal timing at this time. A slightly advanced timing can improve cold starts as well (if the cold-start pull cable is unused). Safe for EGT with no change in airflow

Too much timing advance can increase peak cylinder pressure & reduce efficiency. Don't go too wild on timing advance as it could possibly do some damage.

New 3. If applicable, advance dynamic pump timing - described here. Safe for EGT with no change in airflow

4. Look at the throttle lever on the top of the fuel injection pump, swing it all the way to WOT with your hand, notice that it may be stopped by a screw. This is called the "max throttle screw." Back out the screw a bit to let the throttle swing further at WOT. This will result in more fuel & power on demand. More fuel will increase exhaust smoke, but improving the engine airflow will reduce smoke. Will increase EGT

5. For experienced users only: Do the governor mod in the fuel injection pump. Click here for more details. It increases fuel delivery as RPM increases. Decent power improvement. Will increase EGT

6. Send your fuel injection pump (or a spare pump) to Giles. His pump really enhances performance; this may be the most significant power mod you'll see in a NA diesel. Here's a testimonial. If your pump needs a rebuild, then his service is often recommended. With this pump you can disregard modifications #2-5 above.
Bonus: The pump can be modified to tolerate BioDiesel and today's ULSD (Ultra Low Sulphur Diesel). Safe for EGT regardless of airflow, as the pump is professionally configured and tested in many standard NA diesels

7. If the vehicle still isn't smoking much, then turn in the fuel quantity screw on the side of the injection pump to increase fuel delivery. Use the Bentley manual to find this screw. Will increase EGT

8. Forget about propane unless you can set it up inexpensively, it is not effective on IDIs according to Mr. Sharkey. Maybe a 5-8% increase in power at best.

Chassis/Other

1. Get the flywheel lightened. It will improve response during low RPM, especially when accelerating from a stop.

Dave, from Passenger Performance, his personal preference is a flywheel weight of 6 pounds. But anything between 6, 7 and 8 pounds will work. He advised removing the 1" thick ring on the pressure plate side to 0.050" of the flywheel gear teeth, I think, yields 8 pounds. He then removes material on the other side down to the level of the bolt holes to get down to 6 pounds.

2. Suspension and brakes. If the brakes already stop fairly strong and without heat fade (concerning performance), then it may be good enough for spirited driving. A good sport suspension upgrade can make driving the vehicle a pleasure.

3. Ceramic coating. This could be inexpensive if your NA engine is being rebuilt. Do a search in the IDI forum to find threads discussing this topic. Here's one where 935racer outlines what internal parts might be useful to coat and what parts might not.

Big Power

Now.. onto 'big power' enhancements. Strongly recommended is an EGT (Exhaust Gas Temperature) kit (Autometer Pyrometer, for example, which is available at almost any car parts store) tapped into the exhaust manifold:

Nitrous Oxide

Nitrous oxide and turbo-diesel fuel injection pump. Install the two, pipe the nitrous oxide gas into the intake and pipe another one to the LDA device on top of the turbo-diesel fuel injection pump. The LDA senses boost pressure and responds by increasing fuel delivery in the fuel pump. Instead of receiving boost pressure from a turbocharger, it will receive pressure from nitrous oxide gas for the same result.

For best fuel results between NA and nitrous, send your injection pump (even a NA one) to Giles. He will install a LDA on the pump and set the LDA to increase fuel by 100%, while fueling without LDA action will remain stock. In other words, he will turn your regular NA pump into a TD (turbo diesel) pump that responds to changes in forced air pressure.

You may easily see at least double the stock power output on demand. Nitrous Oxide is also cool (as in cold) unlike the compressed air from turbo, so this may be safe for EGT.

Propane

See Propane under the Fuel section in this post.

*** The following modification is still controversial - some feel that NA diesels (except for the 1.9L D, which is already turbo-ready) should not be turbocharged. You make your own decision. ***

Turbocharging

It will be easiest to adapt turbo parts from a 1.6 turbo diesel. Even the turbo + exhaust manifold from a 1.9 turbo diesel will fit. 1.6 turbos are generally bigger (MUCH bigger than any TDI turbo), with no maximum boost until around 3,000 RPM. The 1.9 TD turbos are smaller and although it may be a better choice for daily driving, it will cause higher EGT due to extra backpressure from the smaller turbine. We want to *minimize* EGT for NA engines.

Most importantly, add GOOD intercooling! And avoid smoking much, if at all (or go by your EGT gauge - it's so much easier to install the EGT sensor while you have your turbo exhaust manifold sitting on a bench!). NA diesel longblocks lack piston cooling oil jets and have weaker metal alloys that are less tolerable to heat from turbocharging. So, make sure you have intercooling. If you leave it at stock turbo-diesel power (68hp), it should be good enough for longevity.

A boost gauge is not required unless you're going to change the boost level by bypassing or messing with the turbo's wastegate, or if you just want to see if the turbo's working normally.

eldorado posted a good guideline in maintaining a NA diesel's longevity with turbocharging:

If you've increased the fueling then running more boost will actually help your engine...diesel's run the exact opposite of gassers...the leaner you run a gas engine the higher the egt's. The leaner you run a diesel..ie no smoke the LESS your egt temps will be. when you see smoke..you'll also notice your EGT temps going up.

You will not have any HG issues that is different than a td....they use the same HG, bolts, torques etc..The only issue you'll have is with the pistons...since they're not being cooled by oil. Youy can really help the problem by adding a big oil cooler like the volvo unit. Your oil temps should never be over 210F ever with the volvo oil cooler setup..it's that good, it was made for a 2.4/2.5 gasser that runs hotter turbo temps.

Once you get past running 10-12psi of boost, you definitely need to add an intercooler..this will help your egt temps and give more power to boot.

The most critical part of a turboed N/A diesel is the EGT's...never go past 1400F pre-turbo. I had an original Callaway turbo diesel n/a engine, I put over 120K miles on it (rebuilt engine) and when I gave it away it was still running strong.

You should be able to run 15psi of intercooled boost with no trouble, add fuel until you see a max temp of 1400F and then back it off a hair and you should be good to go. The only thing that will kill the engine is EGT' temps over 1400F and super oil temps. When you're flogging the engine..I would only watch the EGT gauge.

[ezekiel]

pure awesomeness, thanks.

[trigun7469]

does this effect the MPG? what would you expect to get with those mods?

[malone]

does this effect the MPG?

With most modifications the difference in MPG may be neglible when driving normally. If your parts are worn, e.g. injectors, fuel pump, low compression, then restoring them will improve both MPG + power. So keeping the engine healthy w/ maintenance is an important first step.

If you have increased fueling and if you use it often (driving with the pedal to the metal) then you may see lower MPG, but the extra power is nice whenever you need it, i.e. for passing on the highway, going up hills with extra weight.

what would you expect to get with those mods?

More fun!, better passing, less downshifts when going up hills.

[trigun7469]

does this effect the MPG?

With most modifications the difference in MPG may be neglible when driving normally. If your parts are worn, e.g. injectors, fuel pump, low compression, then restoring them will improve both MPG + power. So keeping the engine healthy w/ maintenance is an important first step.

If you have increased fueling and if you use it often (driving with the pedal to the metal) then you may see lower MPG, but the extra power is nice whenever you need it, i.e. for passing on the highway, going up hills with extra weight.

what would you expect to get with those mods?

More fun!, better passing, less downshifts when going up hills.

what will the HP and MPG be rated you think?

[malone]

I can't answer on HP as I don't recall seeing anyone do a before/after dyno with some modifications.

edit: A 52HP to 77HP gain was claimed with just a fuel pump upgrade, more details here. I can't personally verify that number but based on experience his pump does work very well in a NA diesel. Here's another testimonial.

With an unmodified 1.6 NA engine, you can get either 35 US MPG or 55 US MPG - it all depends on your maintenance, vehicle setup (weight, tires, etc.), and your driving style.

Driving 55 MPH vs. 80 MPH on the highway makes a huge difference in fuel economy. The stock 1.5L to 1.9L NA diesel engine is capable of both speeds. The fuel economy depends on your foot.

I would not worry about MPG difference with most modifications mentioned here. When driving normally the MPG difference should be negligible. However if you're always hammering it with the stock engine and if you'll do the same with a modified engine, then yes you may see a permanent reduction in MPG. The loss in MPG also depends on the extent of your modifications.. there too many variables for me to post an accurate MPG estimate.

If you are anal about MPG, then I bet you won't be pushing the engine hard or speeding all the time (won't be making constant use of the mods).

*edit: Fixed old links.

[Baxter]

I just went through my 1.6d and gave it a bit of a fettle.
I cut some more slots in the MKI grille and attached a air scoop to the rear, then cut the beak off the air box and connected with some decent size tubing - amazing difference!

Good service - much smoohter.

Free-er flowin air filter, bit noisey but worth it!

Did intermediate spring mod, well, I measured the gap between the stops and removed the spring and fitted a pair of copper washers in place of the spring, about 1.8mm it was.
Trouble is I had a real hard time getting the throttle lever back onto the splines, and I marked it up but could I get it back in the right place... er no..  :lol:  So the engine was revving away quite fast, so I backed the throttle stop off to compensate, which now leaves me with more throttle travel, surely this is a good thing!? Gave it a bit more fuel and although I thought it felt slower at first, it's just different, I have to now drive in a different style than I was used to but it does seem a fair bit quicker.

I presume that if I strip the capsule down again and add a washer or 2 more and add to the pre tension on the main spring then I will exagerate the effect? as at the minute all I have done is disable the intermediate spring rather than disable it and add extra tension on the main spring.

When tootling along say, light throttle in second, and you accelerate then it goes straight away, as before it would take longer to get going, I presume before when I went to accelerate then all I was doing was adding tension to the intermediate spring.

TBH, reading all the thread on this site about doing this mod are really confusing, and Im a mechainc, it's only now once I have done it and understand it a little more that it makes sense, hats off to you guys that are spanner virgins when you do this mod, I am surprised more don't go wrong!  :shock:

[foxracer1]

I felt rather "scared to tear in to my pump but i took a spare and tore it down to see what it would be like. The spare was acctually a little different but i got the idea. It helps to just try it but on something your not driving daily.

[Hillshy]

Hi Mr brick,

i'm gunna be attempting this mod in the next few weeks, i to have read all the posts and over and then some more just to make sure, i'm sure it will make more sense once i actually crack the lid of the pump. so youre not the only one! :lol:

how do you find about the upper rev range, longer, any more useful power up there, as there should be more fuel now.

hillshy

[jeremp]

Please repost pics.

[jeremp]

I cant seem to find this "governor mod" any where. I am desperatly looking for more power in my 1.6 na

[malone]

Please repost pics.

The pictures are now fixed.

The first post has been updated as well, mainly formatting changes for readability.

As for the governor mod, there's a thread in this very forum - here's the link:
http://vwdiesel.net/phpBB/viewtopic.php?t=2300

[8v-of-fury]

I would like to add another easy to perform exhaust upgrade, if you don't mind.

The stock manifold (toilet-bowl) is actually a very good design, as far as factory manifolds go. The reason they get so much rap as a restrictive exhaust is because the exhaust system past the manifold IS restrictive. Take of the down pipe and measure the opening of the stock manifold, it is 2.5" in diameter. The restrictive part of this exhaust system is that it usually is feeding a 1.5" pipe for the exhaust (why did VW make it so small? jeez).

Taking the toilet bowl mating surface and cutting out a 2.5" hole and then using 2.5" all the way back will be just like using one of those dual manifolds, probably better as there is no material in the middle to provide yet another blockage.

Doing this will be the best bang for your buck on exhaust for an N/a for sure. It will be 2.5" pretty much engine back. Run this without resonator and a free flowing muffler, you'll have MAJOR FLOW

[malone]

Good suggestion, thanks!

[rabbitman]

I must add that 2.5" is PLENTY big, actually too big. And a muffler is a must, my setup (in my sig) is waaay too loud and hits the frequencies of a ricer.