Twin-Charging and Compound Turbo Charging
06-09-2010, 10:07 AM
#101
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Hi from Scotland...
I found this thread while doing some 'research' on twincharging and compound charging. I've not long completed my own project on a mitsubishi lancer Evo5 that i use for hillclimbs and sprints over here. I have no criticism of anyone's posts so please understand i'm posting from experience to help with this thread!
I thought i'd give you some pointers on the subject as although this is an intersting thread and much thought is being put into this, there's some things that i haven't seen discussed at all. Things that are important at the design stage.
I'm not familiar with the models of cars you're discussing but if like mine the engine bay is already full, it's still possible to fit in an amazing array of pipes and coolers if it's made bespoke. This was a challenge for me but it all seems to fit in quite well and it works in such an amazing way to remove turbo lag and give massive torque and top end power.
First you need to think about what you want to achieve from compound charging. 2nd is cost and 3rd, making it all fit.
One area to think about is exhaust backpressure V's intake pressure. For a turbo to make boost, the pressure needed ahead in the exhaust manifold will be higher than the boost the turbo makes. If you connect the outlet of the turbo to the inlet of a roots or screw type SC, the air will be further multiplied by the SC dependent on the drive ratio and capacity (minus efficiency losses). I used a harrop HTV 1320 SC, fed by a To4z hybrid turbo. The engine size is 2270cc, 4cyl. The turbo would ideally be producing around half of the total boost (but still with the massive top end flow capabilities) and because of this the wastegates on the turbo will be diverting the gasses past the turbine housing and lowering the exhaust manifold pressure. The SC multiplies the inlet charge so at the plenum, there may be as much as double the pressure there is at the exhaust valves. This allows the cylinders to fill up to 40% more inlet charge than with the turbo alone, essentially increasing the volume of the cylinder = more bang for the engine size
I looked into twincharging using 2 turbo's but the fact remains that the exhaust backpressure will always be high and therefore not allowing the cylinders to fill as well, so i opted for a straight compound charge system. The Harrop SC's have a built-in bypass which takes its signal from the plenum. At cruise or idle when there is plenum vacuum, the bypass opens and it takes virtually no power to spin the rotors. Dump the throttle and the valve closes giving instant boost. Economy isn't a concern of mine but for a road car, a bypass is essential
many times i heard that a small SC wouldn't be able to flow enough air at the top end and would restrict the engine if it was after the turbo, which is why so many opt to try to disengage the blower once the turbo has spooled, or even discount this method of forced induction altogether to look at two turbos. This is a very tricky install and difficult to get right without electronics to control valves and clutches. In a compound charge setup, the SC is flowing already compressed air and will continue to multiply up to the SC rev limit. Believe me, i got a few surprises with this project!
If the SC doesn't have a bypass then you can use an external wastegate to do the job very simply. You'd connect the 2 lines at either side of the throttle butterfly and have the valve connected so the pressure would pop the valve off its seat. This gives a purely load sensitive valve that will be very smooth in operation. You can also play with spring rates to adjust the throttle opening that the bypass (wastegate) closes to best suit the use of the car.
The To4z turbo i'm using was producing 635hp at 8000rpm and 2.6bar, but it didn't spool until almost 5000rpm. Using the same turbo and compounding with the SC, this turbo is now at full spool at 2500rpm and the compound effect is available over a massive engine rpm range. At the moment my final boost is down to 2.2bar and the engine is making a massive amount of torque and power than it did at the higher boost with turbo alone! This proves the cylinder filling theory for more power.
To control the combined boost, you would take your boost controller pressure signal from the plenum and set it to the final boost figure you want to achieve. This controls the whole setup nicely in that the boost controller will be adjusting the turbo and with the SC being constant displacement, the final combined boost.
To give you some idea of how this has transformed the engine, we're now seeing full boost at 2500rpm with instant response at any revs. Because of the SC producing boost below 2500rpm as well, the extra airflow through the engine starts spinning the turbo by both exhaust and intake so it's the best of both worlds to make the turbo start spooling early. Also because the turbo only needs to spin to around 2/3 of it's normal speed and the fact it has to produce less boost, this also aids spool to amazing effect!
It's all very magical really. The benefits of both, with the disadvantages of neither!
Other things to know about, a chargecooler is likely to be needed to cool the turbo air before it goes into the SC to avoid overheating the rotors. This will also mean the air is denser at the next compression stage. The whole lot then needs to be cooled via a front mounted intercooler before it enters the engine.
There's also cam duration and ingintion timing changes that can be made to reallty get the best out of the setup but i don't have time to go into that just now
Hope the above helps. From a fellow petrolhead...
I found this thread while doing some 'research' on twincharging and compound charging. I've not long completed my own project on a mitsubishi lancer Evo5 that i use for hillclimbs and sprints over here. I have no criticism of anyone's posts so please understand i'm posting from experience to help with this thread!
I thought i'd give you some pointers on the subject as although this is an intersting thread and much thought is being put into this, there's some things that i haven't seen discussed at all. Things that are important at the design stage.
I'm not familiar with the models of cars you're discussing but if like mine the engine bay is already full, it's still possible to fit in an amazing array of pipes and coolers if it's made bespoke. This was a challenge for me but it all seems to fit in quite well and it works in such an amazing way to remove turbo lag and give massive torque and top end power.
First you need to think about what you want to achieve from compound charging. 2nd is cost and 3rd, making it all fit.
One area to think about is exhaust backpressure V's intake pressure. For a turbo to make boost, the pressure needed ahead in the exhaust manifold will be higher than the boost the turbo makes. If you connect the outlet of the turbo to the inlet of a roots or screw type SC, the air will be further multiplied by the SC dependent on the drive ratio and capacity (minus efficiency losses). I used a harrop HTV 1320 SC, fed by a To4z hybrid turbo. The engine size is 2270cc, 4cyl. The turbo would ideally be producing around half of the total boost (but still with the massive top end flow capabilities) and because of this the wastegates on the turbo will be diverting the gasses past the turbine housing and lowering the exhaust manifold pressure. The SC multiplies the inlet charge so at the plenum, there may be as much as double the pressure there is at the exhaust valves. This allows the cylinders to fill up to 40% more inlet charge than with the turbo alone, essentially increasing the volume of the cylinder = more bang for the engine size
I looked into twincharging using 2 turbo's but the fact remains that the exhaust backpressure will always be high and therefore not allowing the cylinders to fill as well, so i opted for a straight compound charge system. The Harrop SC's have a built-in bypass which takes its signal from the plenum. At cruise or idle when there is plenum vacuum, the bypass opens and it takes virtually no power to spin the rotors. Dump the throttle and the valve closes giving instant boost. Economy isn't a concern of mine but for a road car, a bypass is essential
many times i heard that a small SC wouldn't be able to flow enough air at the top end and would restrict the engine if it was after the turbo, which is why so many opt to try to disengage the blower once the turbo has spooled, or even discount this method of forced induction altogether to look at two turbos. This is a very tricky install and difficult to get right without electronics to control valves and clutches. In a compound charge setup, the SC is flowing already compressed air and will continue to multiply up to the SC rev limit. Believe me, i got a few surprises with this project!
If the SC doesn't have a bypass then you can use an external wastegate to do the job very simply. You'd connect the 2 lines at either side of the throttle butterfly and have the valve connected so the pressure would pop the valve off its seat. This gives a purely load sensitive valve that will be very smooth in operation. You can also play with spring rates to adjust the throttle opening that the bypass (wastegate) closes to best suit the use of the car.
The To4z turbo i'm using was producing 635hp at 8000rpm and 2.6bar, but it didn't spool until almost 5000rpm. Using the same turbo and compounding with the SC, this turbo is now at full spool at 2500rpm and the compound effect is available over a massive engine rpm range. At the moment my final boost is down to 2.2bar and the engine is making a massive amount of torque and power than it did at the higher boost with turbo alone! This proves the cylinder filling theory for more power.
To control the combined boost, you would take your boost controller pressure signal from the plenum and set it to the final boost figure you want to achieve. This controls the whole setup nicely in that the boost controller will be adjusting the turbo and with the SC being constant displacement, the final combined boost.
To give you some idea of how this has transformed the engine, we're now seeing full boost at 2500rpm with instant response at any revs. Because of the SC producing boost below 2500rpm as well, the extra airflow through the engine starts spinning the turbo by both exhaust and intake so it's the best of both worlds to make the turbo start spooling early. Also because the turbo only needs to spin to around 2/3 of it's normal speed and the fact it has to produce less boost, this also aids spool to amazing effect!
It's all very magical really. The benefits of both, with the disadvantages of neither!
Other things to know about, a chargecooler is likely to be needed to cool the turbo air before it goes into the SC to avoid overheating the rotors. This will also mean the air is denser at the next compression stage. The whole lot then needs to be cooled via a front mounted intercooler before it enters the engine.
There's also cam duration and ingintion timing changes that can be made to reallty get the best out of the setup but i don't have time to go into that just now
Hope the above helps. From a fellow petrolhead...
06-09-2010, 11:54 AM
#104
I really wish there was a GOOD positive displacemnent SC available that would fit completely under the hood (without getting in the way of the turbo system)... Full boost from 2500 rpm to redline... Wow.
Madmac, thank you for the information!!!
Madmac, thank you for the information!!!
Last edited by ttg35fort; 06-09-2010 at 11:59 AM.
06-09-2010, 03:10 PM
#105
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I don't have a diagram as such but here's some photos of the engine bay. It's tight and a real pig to work on now but definately worth it. I spent a lot of time on reliability so i didn't have to take it apart every week!
The blower is mounted under the inlet manifold and driven by a toothed belt system. I had to split the drive into 3 belts to get round a belt stretch issue in the early days. Even fitting another wastegate was awkward because the turbo outlet is in the way too.
In my mind this is defiantely the way to compound charge. We couldn't hold it back on the dyno above 5000rpm so the only real figures we have are 386hp & 405ft/lbs at 3000rpm, 591hp & 540ft/lbs at 5000rpm, then all hell breaks out and we can't hold it back as the cams start working..... This is wheel horsepower as the dyno couldn't calculate flywheel horsepower due to the wheelspin. We reckon she's around 700hp at 5000rpm and around 800 -850 at 7500rpm. It accellerates from 0 to 100mph in 4.6 seconds!
If anyone is seriously looking at compound charging for torque and power then this is the way forward.
Dyno run here:http://www.youtube.com/watch?v=re0POTtQafA
Doune hillclimb on low boost as it was the first outing of the setup so i was playing with the torque:http://www.youtube.com/watch?v=aevTJetugMQ
First hillclimb on high boost. Excuse the dodgy gearshifts at the start. I keep touching the gearlever early and operating the flatshift ecu...:http://www.youtube.com/watch?v=hrLsnR8gNiA http://www.youtube.com/watch?v=FkXLKZLPNmw. The engine is now 4 seasons old so is burning oil. Once we perfect the setup a cusome long rod engine will be built to release more torque, we hope!
It's nice to see others experimenting with different forced induction setups though. There's some 'secrets' i need to keep for the moment as this is considered in Evo circles as hot development but i'm happy to help with any technical questions if i can. I've learned a lot from this!
The blower is mounted under the inlet manifold and driven by a toothed belt system. I had to split the drive into 3 belts to get round a belt stretch issue in the early days. Even fitting another wastegate was awkward because the turbo outlet is in the way too.
In my mind this is defiantely the way to compound charge. We couldn't hold it back on the dyno above 5000rpm so the only real figures we have are 386hp & 405ft/lbs at 3000rpm, 591hp & 540ft/lbs at 5000rpm, then all hell breaks out and we can't hold it back as the cams start working..... This is wheel horsepower as the dyno couldn't calculate flywheel horsepower due to the wheelspin. We reckon she's around 700hp at 5000rpm and around 800 -850 at 7500rpm. It accellerates from 0 to 100mph in 4.6 seconds!
If anyone is seriously looking at compound charging for torque and power then this is the way forward.
Dyno run here:http://www.youtube.com/watch?v=re0POTtQafA
Doune hillclimb on low boost as it was the first outing of the setup so i was playing with the torque:http://www.youtube.com/watch?v=aevTJetugMQ
First hillclimb on high boost. Excuse the dodgy gearshifts at the start. I keep touching the gearlever early and operating the flatshift ecu...:http://www.youtube.com/watch?v=hrLsnR8gNiA http://www.youtube.com/watch?v=FkXLKZLPNmw. The engine is now 4 seasons old so is burning oil. Once we perfect the setup a cusome long rod engine will be built to release more torque, we hope!
It's nice to see others experimenting with different forced induction setups though. There's some 'secrets' i need to keep for the moment as this is considered in Evo circles as hot development but i'm happy to help with any technical questions if i can. I've learned a lot from this!
Last edited by madmac; 06-09-2010 at 03:20 PM.
06-09-2010, 05:55 PM
#111
Great stuff madmac!
If there was only more room in the engine bay. I already helped a friend twin charge a car, so I know how it all goes together, and what the "secrets" are.
The ideal blower for us would be an Eaton M90. There may be room if the A/C compressor was removed. A custom pulley would have to be made thogh, but that would not be too hard.
I already looked in to this, just don't have the time to expereiment right now. Most of the people want a big turbo.
If there was only more room in the engine bay. I already helped a friend twin charge a car, so I know how it all goes together, and what the "secrets" are.
The ideal blower for us would be an Eaton M90. There may be room if the A/C compressor was removed. A custom pulley would have to be made thogh, but that would not be too hard.
I already looked in to this, just don't have the time to expereiment right now. Most of the people want a big turbo.
Last edited by Boosted Performance; 06-09-2010 at 05:58 PM.
06-09-2010, 06:00 PM
#112
I would like to pick your brain on this down the road. Right now I just want to get my car back together and running. Nonetheless, If I can get the Eaton M90 to fit under the hood along with the TT system, it is something I would like to seriously investigate.
06-09-2010, 06:14 PM
#114
why would you have to remove the ac compressor. just mount it right on the heads like the stillen. just need a cowl type hood.
It would be very simple to add on as nothing is in the way of the pulleys with a TT kit. You had to make a custom heat exhanger and mount that behind the drivers headlight, but still not very difficult.
It would be very simple to add on as nothing is in the way of the pulleys with a TT kit. You had to make a custom heat exhanger and mount that behind the drivers headlight, but still not very difficult.
Great stuff madmac!
If there was only more room in the engine bay. I already helped a friend twin charge a car, so I know how it all goes together, and what the "secrets" are.
The ideal blower for us would be an Eaton M90. There may be room if the A/C compressor was removed. A custom pulley would have to be made thogh, but that would not be too hard.
I already looked in to this, just don't have the time to expereiment right now. Most of the people want a big turbo.
If there was only more room in the engine bay. I already helped a friend twin charge a car, so I know how it all goes together, and what the "secrets" are.
The ideal blower for us would be an Eaton M90. There may be room if the A/C compressor was removed. A custom pulley would have to be made thogh, but that would not be too hard.
I already looked in to this, just don't have the time to expereiment right now. Most of the people want a big turbo.
06-09-2010, 06:20 PM
#115
why would you have to remove the ac compressor. just mount it right on the heads like the stillen. just need a cowl type hood.
It would be very simple to add on as nothing is in the way of the pulleys with a TT kit. You had to make a custom heat exhanger and mount that behind the drivers headlight, but still not very difficult.
It would be very simple to add on as nothing is in the way of the pulleys with a TT kit. You had to make a custom heat exhanger and mount that behind the drivers headlight, but still not very difficult.
). OK, I'm an old fart. So be it.
06-09-2010, 06:29 PM
#116
Or just try the Stillen - don't think anyone has on a turbo'd engine. This would be a great experiment for your laggy turbos str8dum1. I'm not sure why a roots would be better than a twin screw (Eaton vs Stillen?) but interested in hearing what Sasha has to say...
I'm not sure why a roots would be better than a twin screw (Eaton vs Stillen?) but interested in hearing what Sasha has to say...