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Water Injection Pump 1

I read your article on water injection. I have a question, I looked around here locally and most pumps mentioned they are vibratory pumps. Should I try this or keep looking. The price wasn't bad, I enclosed a link of the pump I'm looking at purchasing.

Anthony Limjoco

United States

The pump you have cited looks fine.

Water Injection Pump 2

I'd like to give some background to some question I need to ask.

I've been using a high-pressure water/air water misting system on a Peugeot DW10B engine for research on emission control in diesel engines. Presently I'm using a Kärcher pressure washer pump, with an external variable regulator for the water supply. I'm using a flow meter on the injector inlet (for water) to control the amount of water injected in the intake. Trouble is, I have to keep an eye on the flow meter reading while doing the test, as a change in water injection rate changes the emissions considerably. And I change the flow rate by hand by varying the water injection pressure.

Needing to develop a closed loop system, I'm tempted by the Ulka pump, some reasons being:

1. It's cheaper

2. Less noise

3. Much lower power requirements

4. The Kärcher pumps 300+ kgs/Hr of water, I recirculate it to prevent wastage, this heats up the water over a test period causing further complications in repeatability.

5. Best of all, the Ulka seems much quieter than the Kärcher.

6. I've killed off one Kärcher after a long test period. It'll soon get really expensive as replacements will be needed.

I feel that it's better for the flow quantities I'm looking at (In the region of 3 to 15 kgs/Hr at 6 Bar). I'd like to use the pump in a closed loop setup coupled with the flow meter. To vary the flow rate (piston stroke length and/or frequency?), I would imagine that a variation in duty cycle or drive frequency would work.

Have you had any experience with this? Can I use a type of AC signal conditioning to change the "duty cycle", so to speak? Or is it best to use the piston/cylinder assembly and drive it using a new solenoid winding at a lower voltage? That way I may be able to vary the drive frequency.

Any ideas would be greatly appreciated.

Thank you for a great magazine.

Samiur Rahman Shah


We trialled varying pump power and found that any reduction in pump performance resulted in the nozzle just dribbling (rather than atomising) as the pressure dropped away. We’d suggest the best approach would be a methanol injector pulsed at high frequency and variable duty cycle, used in conjunction with a pressure regulator on the Ulka pump. However, as described in Part 2 of that series, this approach also has problems, especially when flowing very small quantities of water. The simplest approach might be to simply change nozzle size to vary the flow.

Water Injection Pump 3

Came across this:

Price is better than quoted in the article!

Dave Yates


Well found! Footnote has been added to article.

Water Injection Pump 4

I have been reading with interest your stories on the water injection system utilising an inverter and the ulka pump/spraying systems UK nozzle. I have been working on a system almost identical for my vehicle.

I too came to a similar conclusion with cooling the pump, but developed a proportional controller utilising a PIC microprocessor and a high-side driver for the ulka pump - as you are no doubt aware, the ulka pump is a vibratory pump, which has a blocking diode so it is effectivly using pulsed DC for the solenoid.

The flow rate and pressure of the pump may be grossly controlled by reducing the pulse frequency (but not duration - a light dimmer chops off either the leading or trailing edge of the pulse, so the piston does not travel the full distance of the cylinder). This approach is taken in several coffee machines, where the frequency is divided by a pair of 4017 decade counters driving an SCR – this is the slow clunk, clunk when you are using the steam function of most thermoblock coffee machines.

A similar approach may be used to control the flow/pressure of the pump - by rectifying the output of the inverter (bridge rectifier and a smallish cap removed from a computer power supply) and an IGBT switched from the output of a PIC (which monitors the duty cycle of the injectors, and compares this to an internal user programmed map).

The output of the pump may be increased by increasing its frequency as well - these are specced for 60Hz as well, but may be pushed higher if neccesary.

Another (far safer!) approach to this problem is to get the pump in the 12V AC version - the thought of safely routing almost 340V DC (240 X 1.414 assuming a sinewave inverter) is just plain worrying!

Also - feel free to forward my email details to last weeks response correspondent John Drewett ('Electric Bike') as I have a large surplus of used but reasonable 7.2AH SLA batteries + heavy wires and connectors + battery frames from a decomissioned 30KVA UPS that would be of use to him - I can supply these gratis if he would like a few to construct his electric bike - as he is located in Newcastle.

Heath Young


We have passed on your details to the bike constructor. Re altering pump output: you have not mentioned the real problem - what happens to the nozzle spray pattern when you drop pump pressure.

Water Injection 1

Just have a thought for the water injection article. If you want water vapor, why not make a heat exchanger by wrapping metal tubing around the exhaust? It will work like a coffee maker, but you will have to trap and return liquid water. If you install it in the engine bay, you can recover wasted energy and lower the temperature at the same time.


United States

Because the change of state from water droplets to water vapour, and the consequent uptake of heat, needs to occur in the intake and engine.

Water Injection 2

Re your Water Injection experiments. I did some family reearch and found that a distant relative of mine was killed in 1944 when the engine of his Messerchmitt Bf109G6 blew up shortly after take off. I researched this aircraft, and found that they had an underbelly tank of 300 litres of 50% water/50% methanol injected into the engine. The idea was to increase the boost, which took the engine from 1475HP to 1950HP. The cost was enormous engine wear. I suspect a minor amount of water injection might be OK, but a huge amount as the Luftwaffe was doing, was detrimental. Then again, if you expect to get shot down in 20 hours, the engine only has to last 25.

Marshall Peters


Throttle Heating

Just like to pass on my compliments to your site, I'm a bit of a newbie to it but I'm finding all your recent articles a pleasant and insightful read. It's fast becoming one of my regularly checked sites!

I would like to put forward a suggestion about a possible article and that is (a bit in the style of the recent 5 cent resistor 'mod') the throttle body coolant bypass modification. I have recently done it to my car and I have noticed a change in how it drives, but what I would really like to know is the technical side of what's going on!

Andrew Mountford

United Kingdom

We haven’t ever tried bypassing the throttle body coolant supply but we assume it results in slightly cooler intake air temperatures.

Salvaged Drills

Sometimes you can say something and it causes a trigger elsewhere. So thanks to the writer for "The electronic variable speed controller ,,,,,,,, A better approach is to build a mechanical system that gives the progression of trigger movement needed in the application."

Twenty minutes later I have a used a drill controller (to drive transistors) as a core of a speed controller on my Dad's, um, well, mobility scooter. The one he built himself. The one that uses two starter motors and direct on/off drive. The one that goes about 40 miles an hour,,,,

Now thinking about using old drills as drive for automatic door openers on my car,,,, Arrgggghhhh better still; drill motor and perhaps two sets of reduction gears. A chuck. A length of threaded rod and a bolt welded in the chassis, hey Presto! Built in electric jacks. Now how is that for a theft deterrent??? (Or a simpler project is to electrify one of those bloody awful scissor jacks,,)



Forgot Diesels

In your recent article "crash boom bang" the first line "every engine has them" made me want to cry. come on guys don't forget the humble diesel.

Travis Brookshire

United States

Measuring Performance and Fuel Economy

Some praise, a suggestion and a question. I can't praise you enough for not only publishing relatively cheap methods for finding more performance but also quantifying the gains - how often I've read in magazines of "noticeably more grunt in lower revs" and longed for some figures to verify such a judgement, I don't need to tell you.

What I'd like to read is a feature from you about on-road-dynoing with a product like this:

I've also read of a software that analyzes the sound of a car and produces a dynosheet from this audio-data. Such a topic would perfectly blend in with your other tech features, imho.

In the feature about modifying under-car airflow you said that quantifying the improvement "... is only applicable to cars with an averaging fuel consumption readout" - I was wondering wether a precise speedo and tacho won't allow similar conclusions? I guess fuel consumption algorithms use the same data plus some constants. Less rpm for the same km/h = better airflow? No need to answer directly, perhaps you can relate to that if you revisit the article in the future or do a similar feature.

Frank Dellen


With regards to on-road dynos and the like, for quantification of performance gains or losses, we don’t think a simple stopwatch and the car’s speedo can be beaten for low cost and absolute on-road validity. Fuel economy needs be measured by dividing distance travelled by fuel consumed; it cannot be worked out by engine speed versus road speed (a relationship that in the one gear, is constant in manual transmission cars and near-constant in those with automatic transmissions).

Modification Direction 1

Re: Where to from here. I have a couple of points to make about this overall well argued piece.

1. I wish a trailer could substitute for a ute. It can if you are going from one spot in the suburbs or exurbs to another, but if you are going to be dealing with angle parking, multi-level car parks or just about any shopping centre that I have dealt with, then a trailer is just not going to work. The result is that I rent a ute about once a month. Which ALMOST works out money wise.

2. Current police attitude to wheel spin makes traction control and/or 4wd even more of a performance advantage than the practical results would suggest. Driving a RWD or (worse) FWD requires such a significant margin of safety when it comes to the right foot that even a "slower" 4wd is a much faster car if you are in a strictly policed area.

3. Modifying a hybrid may be fairly daunting for a Prius, but surely the Insight is much more straightforward? Autospeed's own articles on modification of the lean burn system suggest this.

4. Tangentially, could an aftermarket lean burn system be possible? The aftermarket now has far more computing power than manufacturers had in the mid 1980s.

5. I've seen the advantages of smaller (but higher boost) turbos and higher profile tyres touched upon at some of the more technical webforums, but Autospeed has yet to look at any of this.

As you can tell, this is the sort of article that gets me thinking.

Patrick McAuliffe


Modification Direction 2

Regarding your article 'Where to from here?' you stated that you would be happy to see fuel prices around $3 to $4 per litre.

I think the federal and state governments would dearly love this too!

correct me if i am wrong (i am bad at maths) but at these fuel prices, wouldn't the taxes be in the order of $1.20 per litre?

Last year my wife and i visited her family in Austria and Switzerland and i took notice how much it costs to get around. in AUD terms it was freakishly expensive but was only marginally more in referance to their cost of living. it must be a cultural thing but even when people have nice cars, they still walked or trained to where they wanted to go.

i agree that personal use must be curbed, but raising fuel prices will raise the cost of EVERYTHING that needs to be transported. And Australia is more succeptable to this as your nearest foreign country (aand trading partner) isn't just a 20 minute drive away.



Conductive Glass in Spark Plugs?

"The centre piece of conductive metal stops short before it gets to the electrode, with the gap between it and the electrode filled with conductive glass material."

This is the first time I've heard of "conductive glass material." ...I use glass for an insulator in my Lyden jars. I'll be more careful in the future. <grins>

Bob Wilson

United States

The most recent edition of the Bosch Automotive Handbook (6th edition – page 628) says the same thing: “... an electrically conductive glass seal forms the connection between the centre electrode and terminal stud”.

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