Tuning a Biturbo

Water Injecting my Biturbo 425!

A contribution from Richard J Bridge

IMPORTANT NOTICE!

RICHARD IS AN EXPERT IN THESE MATTERS AND KNOWS EXACTLY WHAT HE IS DOING!

AN UNQUALIFIED PERSON UNDERTAKING SUCH A CONVERSION CAN END UP CAUSING SEVERE DAMAGE TO AN ENGINE AND INCUR THE HIGH COST THAT THIS WILL INVOLVE. THIS PAGE IS SIMPLY AN ACCOUNT OF CONVERSION WORK THAT RICHARD HAS CARRIED OUT ON HIS BITURBO 425!!!


"Hello Henry, It was nice to meet you at Castle Combe on Saturday having seen your website before. I am attaching some photos of my car for you...



You can see that the car has 16" wheels, Zender side skirts and the MIE front and rear bumpers with 430 chrome cappings on top. It is a 425 but the front wings, front panel and headlights are from a 430. The bonnet is Karif. Also the 430SE(?) rear spoiler and number plate surround are on the back. I bought the car as a restoration project in 1992 and took the choice to update the appearance, as it needed new panels anyway! The engine bay is stuffed full of modifications. The intercoolers are from an early Biturbo and have been modified by having a flange/box tig welded on the front. Ducting then goes down to the radiator grille to a pair of flanged plates so that a good through-flow of air can be obtained. They are very efficient. I have placed thermocouples (that's why there is that ugly extra dashboard in the car) at three points around the engine to monitor temperatures and the intercoolers get 100°C compressed air down to a few degrees above ambient on a summer's day! I remember one day the outside temp was 25°C, compressed air in was 100°C and intake manifold temp was 28°C - that's efficient I think you will agree.



The wiggly round thing infront of the plenum chamber is an ERL 8BAR race water pump (www.aquamist.co.uk and see system 1S). This pumps water through a solenoid valve and a small manifold block to a pair of 0.4mm orifaces mounted on the front face of the plenum. It is set so that when the boost exceeds 10psi a water mist is injected at about 300ml/min flow. This STOPS pinking!! My MABC pressure transducer is shorted so that the computer doesn't know what's going on - this gives 15PSI boost - a 50% increase over standard. This combined with the huge temperature drop on the intercoolers makes for a really cold, dense charge and the car goes very well.



What do you think? I have the MABC on my desk at the moment in pieces. I have read an interesting article on modifying the SAAB APC and am just comparing the MABC to the information I have... it's possible to get 1.6 BAR boost on a SAAB 900 Turbo - Hhmmm! I might get around to writing something on the water injection and boost mods within the next few months so will let you know what I come up with. Whats the boost pressure of your Ghibli? All the best. Regards, Richard."

"Dear Richard, Fellow enthusiast Nick, who drives a Ghibli Cup, has just sent me details of an intercooler water spray cooling system as a simple and cheap way of boosting performance. Do you have any understanding of this system?" Regards, Enrico." "Hi Enrico, Yes, I have seen this sort of thing. What it does is squirt a mist of water onto the surface of the intercooler. It works on the evaporative principle used in some air conditioner units... The idea is simply summed up by this experiment: 1. Drive along a road at any given speed and put your hand out of the window. 2. Wet your hand and repeat the above experiment. Which feels cooler? Also the mist of water takes heat away from the intercooler. As the moisture contacts the surface, the 'radiator' gives up some heat to the water droplets and they carry it away - This increases cooling efficiency too. As for my car. It does not run at present as I've got pipes off it and the distributor is due to come off any lunchtime now. If you are happy to just take photos and talk about it then you are welcome to come down pretty much anytime. Let me know which you'd prefer and then we can arrange a date / time. Regards, Richard." "Hi again Enrico, Here is some more info on my water injection, I've just emailed it to an interested man from the Forum so thought I should copy it to you as I have already written it: The water injection is the ERL Aquamist system 1S. I might write an article on this with some photos in the next few weeks as I have had quite a few questions about it. If you go to www.aquamist.co.uk and look at the system 1S you can find out about it. The way I fitted it to my car was to make a chassis which bolts to where the throttle cable bracket 'was' mounted. All the gubbins is then mounted onto the chassis. Simple schematic drawing of the water injection system

1 - High pressure race version of the pump		2 - Close-up of the manifold

3 - Boost and temperature gauges		4 - Close-up of the pressure switch

GAUGES - The analogue gauge on the left gives turbo boost pressure and the one on the right the water pressure. The LCD display in the centre shows the exhaust gas temperature, the intake manifold temperature and the air temperature between the turbochargers and the intercoolers

5 - Close-up of the solenoid operated valve		6 - Close-up of one of the water injectors

WI INJECTORS - are fitted via threaded holes mounted on the front face of the plenum chamber.

7 - Close-up of the plenum switch		The engine bay of Richard's Biturbo 425

WI PLENUM SWITCH - the pressure switch that activates the solenoid valve to start the water flowing. ENGINE BAY - Speaks for itself. Notice the intercoolers with their ducts, the water injection chassis and the pop-off valve mounted on the front of the plenum chamber - one gets used to it hissing on every gear change.

Two of the four air intakes for the intercoolers.		Close-up of one of the three thermocouples

THERMOCOUPLES - Richard has added three thermocouples to the system (see GAUGES): 1. In the pipe between the turbo and the intercooler. 2. In the No.6 cylinder exhaust manifold, 1" from the head. 3. In the No.6 cylinder intake manifold.

Purpose-built chassis for major components.		WI installation showing the pop-off valve

The high pressure race version of the pump (1) pumps water into a small manifold (2) with a pressure switch (4) on it. This is set so that the manifold always has about 6 BAR of water pressure in it as read by a gauge on the dashboard (3). When the pressure is reached the pump is switched off and the pressurized water remains in the manifold waiting to be released.

A short length of tubing then leads to a solenoid operated valve (5). This valve is opened when the pressure in the plenum chamber exceeds 10 psi. 10 psi being the standard boost pressure on a biturbo. The pressure switch (7) opens the solenoid valve at more than 10 psi and the water flows to the two injectors (6). These jets are 0.3mm in size and allow a flow of about 300 ml/minute between them. As the 6 BAR water is pushed through the tiny holes it atomises and forms a very fine mist.

As the water flows through the injectors the pressure in the manifold drops and the pressure switch (4) turns the pump back on to maintain the water pressure.

Water injection is fantastic and, although it takes a while to fit, is well worth it. I got an engineering shop to modify my plenum chamber to accept the pressure switch and the two injectors.

Regards,

Richard."

"Hello Enrico,

I have taken some more photos for you. This time I just turned the resolution of the camera down rather than re-saving them as lower quality JPG images to get the file size down. I think you will still need to compress them further for your website though.

The shot of the air intake is not so good. Perhaps you'd be better using the one I sent yesterday.

A thermocouple is inserted in the pipe from the turbocharger to the intercooler and monitors the temperature of the compressed air before it is intercooled. I have three thermocouples; one as described, one in the inlet manifold on the No.6 cylinder and one in the exhaust manifold of the No.6 cylinder. The information from these is displayed on my auxilliary dashboard (which again is a prototype and never did get finished properly). From here I can select which temperature to display and monitor what is going on. Exhaust gas temp, Inlet temp and temp of compressed air before intercooling. It can be seen how good the intercoolers are working by seeing the temperature before and after.

The injectors were fitted to the plenum chamber in the same way the pressure switch was. A hole was first drilled in the plenum that was just big enough for the injector to snuggly poke through. Then an aluminium plate was drilled and tapped to accept the injector. The plate thickness was such that the tip of the injector didn't protrude much into the airflow. Next the plate was welded to the plenum. All the work on the plenum was carried out by a specialist engineering workshop that welded aluminium all day long... so as not to destroy the plenum by getting it wrong!

I also have a pop-off valve mounted on the front of the plenum chamber. This opens and exhausts the pressurized contents of the plenum chamber when one comes off the throttle. It prevents the compressed air (and water) heading back towards the turbochargers during gear changes. It has been known for turbochargers to stall when high pressures of compressed air come back at them, when they stop blowing during gear changes. So I thought I'd fit one just in case.

Any questions, please ask.

Regards,

Richard."

If anyone would like more details and information about the water injection system, you can email Richard at richard(at)general-aviation(dot)net and I'll email it to you.

Regards

Richard J Bridge