Twin Turbocharged LPG powered 928
02-05-2009, 05:21 AM
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Twin Turbocharged LPG powered 928
As a continuation from "LP Gas powered 928" thread.
So having succesfully converted to LPG, it was time to start in ernest on the Twin Turbo conversion. I had been gathering bits and pieces for some time,I had determined that a couple of Garrett T28 turbos would be suitable for my 4.5 litre. I sourced 2 from Nissan SR 20 engines as found in 200SX /Silvia.
I fabricated a couple of exhaust manifolds from steel "steam" bends and T pieces, having had the exhaust flanges laser cut. I bought in the turbo flanges and gaskets.
It was only at about this stage that I finally settled on the configuration. Having wrestled the LH turbo into position, I was having nightmares about fitting the RH unit, what with the steering shaft coming down on that side and all. Of course the answer was staring me in the face, Having removed the air pump there was now space to run the manifold forward and mount the turbo at the front of the motor. which also meant I didn't need a pump to return the turbo drain oil to the sump, simply run it to the oil fill tube.
Of course there is an almost unbelievable amount of detail work and fabrication involved. From simple little tasks like changing the orientation of the turbos to suit my application: application of WD40, loosen bolts, strike repeatedly with hammer, more WD40, clamp in vice, insert 4 foot length of pipe twist to correct orientation, repeat, on compressor side. Then of course the wastegate doesn't line up any more, modify wastegate actuator bracket, shorten and modify wastegate actuator rod, drill and tap compressor housing to mount wastegate actuator, further modify wastegate actuator bracket to allow wastegate actuator to be fitted after installation of the turbo and manifold because they can not be installed into the car with it attached ! And so it goes on and on ........
I don't have the skill or facilities to weld aluminium, so I made everything in steel ! Many trips to the local truck exhaust workshop for mandrel bends, lots of cutting welding and general fabrication.
Toward the end of the project I was able to track my hours quite simply and in total I reckon I spent about $4500 and around 350 hrs.
The lpg side of the installation was supposed to be easy, 1 small hose from the mixer to the gas convertor so that the convertors see boost pressure.
I set the wastegates at 8 psi on the bench they are opening at 7 on the car, I wanted to start at something safe but worthwhile.
So when the time finally came for start up I was feeling quite pleased, finally a dream realised, it was reluctant to start, but eventually spluttered into life, but once warmed up, started on the button every time. Finally time to drive the beast, in 1st gear feed in some throttle, ok, some more, lets see if there is some boost hidden in there somewhere,OMFG..... in what seemed like a split second from about 3000 rpm it hit 7psi, lit up the rear tyres, gently slewed sideways and the engine seemed to kind of stop at 7000rpm oops must be time to change gear...into 2nd on the throttle again and it was as if the ignition was switched of ....then on .......then off again....repeating oooooh this is not good.
It took a little thinking before I nailed down what was happening. Under boost the gas leaving the convertors was at boost pressure, fine when the mixer is under pressure, not so good after you have changed gear and the mixer is no longer under pressure, open the throttle and all of this pressurised gas floods into the engine, putting the fire out !
The solution was to move the convertors closer to the mixers, no, not closer but actually screwed to the mixer. Now, I would have done that initially if I could! So I've had to reconfigure the LPG induction system and revert to only one mixer, the space where the second mixer was is now home to a convertor. unfortunately I don't have a photo of that here.
Meanwhile there were ominous signs that all was not well with coolant to combustion sealing. Yep a 30 year old head gasket had called it a day, rest assured I was a slightly despondent chap removing everything I had worked so long and hard to build and fit. Still I know it works and it was simply old age that is the issue with the gasket.
Replace the gaskets, reassemble the whole device and there it is, about 350 hp/ 1450 kg, wind up the boost to 10 psi should be good for about 400hp, at that, it has a better power to weight than a new M3 BMW... I figure i should be happy with that for less than $15 000AUD
Pictures are worth a thousand words....
Cheers Roy
So having succesfully converted to LPG, it was time to start in ernest on the Twin Turbo conversion. I had been gathering bits and pieces for some time,I had determined that a couple of Garrett T28 turbos would be suitable for my 4.5 litre. I sourced 2 from Nissan SR 20 engines as found in 200SX /Silvia.
I fabricated a couple of exhaust manifolds from steel "steam" bends and T pieces, having had the exhaust flanges laser cut. I bought in the turbo flanges and gaskets.
It was only at about this stage that I finally settled on the configuration. Having wrestled the LH turbo into position, I was having nightmares about fitting the RH unit, what with the steering shaft coming down on that side and all. Of course the answer was staring me in the face, Having removed the air pump there was now space to run the manifold forward and mount the turbo at the front of the motor. which also meant I didn't need a pump to return the turbo drain oil to the sump, simply run it to the oil fill tube.
Of course there is an almost unbelievable amount of detail work and fabrication involved. From simple little tasks like changing the orientation of the turbos to suit my application: application of WD40, loosen bolts, strike repeatedly with hammer, more WD40, clamp in vice, insert 4 foot length of pipe twist to correct orientation, repeat, on compressor side. Then of course the wastegate doesn't line up any more, modify wastegate actuator bracket, shorten and modify wastegate actuator rod, drill and tap compressor housing to mount wastegate actuator, further modify wastegate actuator bracket to allow wastegate actuator to be fitted after installation of the turbo and manifold because they can not be installed into the car with it attached ! And so it goes on and on ........
I don't have the skill or facilities to weld aluminium, so I made everything in steel ! Many trips to the local truck exhaust workshop for mandrel bends, lots of cutting welding and general fabrication.
Toward the end of the project I was able to track my hours quite simply and in total I reckon I spent about $4500 and around 350 hrs.
The lpg side of the installation was supposed to be easy, 1 small hose from the mixer to the gas convertor so that the convertors see boost pressure.
I set the wastegates at 8 psi on the bench they are opening at 7 on the car, I wanted to start at something safe but worthwhile.
So when the time finally came for start up I was feeling quite pleased, finally a dream realised, it was reluctant to start, but eventually spluttered into life, but once warmed up, started on the button every time. Finally time to drive the beast, in 1st gear feed in some throttle, ok, some more, lets see if there is some boost hidden in there somewhere,OMFG..... in what seemed like a split second from about 3000 rpm it hit 7psi, lit up the rear tyres, gently slewed sideways and the engine seemed to kind of stop at 7000rpm oops must be time to change gear...into 2nd on the throttle again and it was as if the ignition was switched of ....then on .......then off again....repeating oooooh this is not good.
It took a little thinking before I nailed down what was happening. Under boost the gas leaving the convertors was at boost pressure, fine when the mixer is under pressure, not so good after you have changed gear and the mixer is no longer under pressure, open the throttle and all of this pressurised gas floods into the engine, putting the fire out !
The solution was to move the convertors closer to the mixers, no, not closer but actually screwed to the mixer. Now, I would have done that initially if I could! So I've had to reconfigure the LPG induction system and revert to only one mixer, the space where the second mixer was is now home to a convertor. unfortunately I don't have a photo of that here.
Meanwhile there were ominous signs that all was not well with coolant to combustion sealing. Yep a 30 year old head gasket had called it a day, rest assured I was a slightly despondent chap removing everything I had worked so long and hard to build and fit. Still I know it works and it was simply old age that is the issue with the gasket.
Replace the gaskets, reassemble the whole device and there it is, about 350 hp/ 1450 kg, wind up the boost to 10 psi should be good for about 400hp, at that, it has a better power to weight than a new M3 BMW... I figure i should be happy with that for less than $15 000AUD
Pictures are worth a thousand words....
Cheers Roy
Last edited by Roy928tt; 04-02-2009 at 02:59 AM.
02-05-2009, 08:31 AM
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Sweet!!!!
Thanks for the pictures, looks like a fun project.
Thanks for the pictures, looks like a fun project.
475hp/460lb.ft
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02-05-2009, 02:00 PM
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this is such a big step for the cis guys hoping to boost safety and held back by cis!!!!!!!!! that statment is only base on the fact of the 100+ octane rating. Now where can you get LPG in the States i think i'm going to pursue this project on MY79 4.5 cis. Roy928tt hats off to you......
02-05-2009, 02:06 PM
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Since LPG is a little less lubricating than gas. I would suggest an Amsoil oil vacuum Drip system very cheap it drips a little oil into the vacuum system to keep everything will oiled. also engine wear is reduces
05-05-2009, 08:20 AM
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Brilliant Roy!
You have managed to do the impossible..!!!!
Combine fun with sensibility!!!
Power with economy!
Thrills with environmental awareness!
Respeck!!!!
You have managed to do the impossible..!!!!
Combine fun with sensibility!!!
Power with economy!
Thrills with environmental awareness!
Respeck!!!!
05-05-2009, 08:30 AM
#15
Instructor
928TT LPG
Hello Roy, thats a great project and I must say probably the most boldest modification I've seen to a 928 engine being turbocharged.
Would you like to place your car on another website.
www.turboclub.com
Have a look around, it's my parents website. I have my 2 cars on there (AMC Javelin and my SuperGas dragster) The Javelin is blown, the dragster Turbocharged.
Only turbo based cars on the site. A 928TT LPG would be and interesting read.
Cheers,
Glenn.
'81 928
Would you like to place your car on another website.
www.turboclub.com
Have a look around, it's my parents website. I have my 2 cars on there (AMC Javelin and my SuperGas dragster) The Javelin is blown, the dragster Turbocharged.
Only turbo based cars on the site. A 928TT LPG would be and interesting read.
Cheers,
Glenn.
'81 928