well happy September all!! THIS is going to be a big first post sorry in advance lol.
I was going to keep this next evolution of my imp under cover but the more I think about it the more I feel I would benefit from letting you guys in on the project as there's some crazy clever people on here!
I have spent the last two weeks working out how to go about "version one" of the build which is going to be a simple one without the use of a electromagnetic clutch and using a bypass valve in one pathway.
There’s three main ways to do a twincharged set up
the 3 systems are...
#1 turbo into S/C continuously.
This is by far the simplest way as it does not require bypassing the SC or turning off s/c at higher rpm. the turbo blows thru the sc which gives bottom and midrange torque.. then turbo comes on boost for top end power. the pressurised air feeding into the sc could even help reduce belt drag? the turbo's wastegate controls total boost pressure.
It needs to be mentioned that feeding an S/C hot (non intercooled) air straight from a turbo could cause damage to some sc so intercooling the air from the turbo before the sc is a good idea.
#2 turbo into S/C with bypass.
seems to be the favoured choice for those aiming for peak power. (Lancia Delta S4, HKS aw11 4agzte kit).
Ideally running two intercoolers, one after the sc and one after the turbo. The sc provides low rpm boost until turbo matches it for flow. a bypass valve around the sc is gradually opened in a controlled manor until the turbo provides all the air. once the turbo out flows the supercharger then the charger can either be left in a recyling state or disengaged via electromagnetic clutch for peak power.
The bypass valve operation is the tricky bit... and as far as i've seen its the GRADUAL opening of the bypass that is essential to a smooth transition from sc to turbo. ie say the SC is geared to produce 10psi to the engine.. the bypass valve will be set to start opening at anything above atmospheric pressure before the SC. to try calculate these events would require knowledge in flow rates of each component. The idea here is that the turbo will be matching the flow of the supercharger at the point when pressure is seen anything above atmospheric (14.7psi absolute) before the sc. You will then need to be able to control how much air is bypassed thru the bypass valve at certain boost pressure before the supercharger. If the bypass too slow to open it will act like a continuous system where the sc compounds the pressures.. you will want a measured amount of this but if the compounding pressure exceeds the maximum set boost pressure of the turbo alone then a spike in pressure will be seen. if the bypass acts too fast there will be a pause or dip in boost pressure. the perfect boost curve is one that raises gradually without dips or spikes.. hence the beauty of the twincharger!
The downside of this system is the amount of components and expense + complexity which requires more engine bay space, more money and time to setup and tune.
A single intercooler system can be used...
by running a cooler after both chargers.. probably the preferred option.
intercooler after the turbo but before the sc.. care must be taken to check sc air temps do not get into detonation teritory. lower compression ratio or water injection amongst other techniques could be used to offset this. 10psi out of a roots charger can get surprisingly hot!
#3 SC into turbo with bypass
SC blows thru turbo until turbo matches it for flow then a bypass around the sc opens to free up intake air before the turbo. again a twin intercooled system would be preferred to rid all heat from the compressed air. In a single intercooler setup, both chargers are before the cooler. (your turbo is providing top end boost and since this is a twincharger system aimed at big turbos for top end.. you'd be an idiot not having intercooler after turbo!). The bypass valve also needs careful tuning on opening rate to prevent any dips in the boost curve.. if bypass opens too slowly.. as the turbo outflows the sc, it will suck a vacuum into the piping after the sc, thus restricting how much air the turbo can flow (reducing top end power). if bypass opens too early.. ie before the turbo matches flow rates you'll get a dip in boost. once turbo has matched flow of sc.. I can't see any disadvantage of snapping bypass full open.. tho I see prolems occuring when actually running at that exact switchover point.. say driving up his on 3/4 throttle (whereever that point is). I could see the bypass having indecision issues heehee (open, close, open, close).. therefore a gradual open system is preferred.. ah but how do we control this?
So basically I'm going to attempt No/3 on my wee imp engine ;D
Did a quick cad drawing too (and I mean quick!!) so I could understand what I'm aiming for!
So with the ideas set in my mind of the parts and components needed to make this work, Ive come up with a brilliant idea for a valve
its so simples its clever lol.
Found the main part, the supercharger now most would go a grab a used mini supercharger as thats the norm, easy to find, cheap, and basically new still.
But I knew from a previous attempt at this that the mini supercharger is far from mini! so I went hunting and managed with a stroke of luck to come across a super neat half sized eaton charger that is used on the new TSI golf (Twincharged from factory).
Here it is, problem is finding out information about it, no data sheets are online and eaton have been useless so far but will keep trying! I really need to know its max rpm range and psi ect and the pulley size needed on the crank (think I might just go stick my head under a golf at the dealers ;D
Now that I have it in front of me I'm a little confused as to which is the air in and which is the air to carb? (turbo in my case) can someone confirm for me please?
Just in case you don’t know the car in question
Thanks
Chris
I was going to keep this next evolution of my imp under cover but the more I think about it the more I feel I would benefit from letting you guys in on the project as there's some crazy clever people on here!
I have spent the last two weeks working out how to go about "version one" of the build which is going to be a simple one without the use of a electromagnetic clutch and using a bypass valve in one pathway.
There’s three main ways to do a twincharged set up
the 3 systems are...
#1 turbo into S/C continuously.
This is by far the simplest way as it does not require bypassing the SC or turning off s/c at higher rpm. the turbo blows thru the sc which gives bottom and midrange torque.. then turbo comes on boost for top end power. the pressurised air feeding into the sc could even help reduce belt drag? the turbo's wastegate controls total boost pressure.
It needs to be mentioned that feeding an S/C hot (non intercooled) air straight from a turbo could cause damage to some sc so intercooling the air from the turbo before the sc is a good idea.
#2 turbo into S/C with bypass.
seems to be the favoured choice for those aiming for peak power. (Lancia Delta S4, HKS aw11 4agzte kit).
Ideally running two intercoolers, one after the sc and one after the turbo. The sc provides low rpm boost until turbo matches it for flow. a bypass valve around the sc is gradually opened in a controlled manor until the turbo provides all the air. once the turbo out flows the supercharger then the charger can either be left in a recyling state or disengaged via electromagnetic clutch for peak power.
The bypass valve operation is the tricky bit... and as far as i've seen its the GRADUAL opening of the bypass that is essential to a smooth transition from sc to turbo. ie say the SC is geared to produce 10psi to the engine.. the bypass valve will be set to start opening at anything above atmospheric pressure before the SC. to try calculate these events would require knowledge in flow rates of each component. The idea here is that the turbo will be matching the flow of the supercharger at the point when pressure is seen anything above atmospheric (14.7psi absolute) before the sc. You will then need to be able to control how much air is bypassed thru the bypass valve at certain boost pressure before the supercharger. If the bypass too slow to open it will act like a continuous system where the sc compounds the pressures.. you will want a measured amount of this but if the compounding pressure exceeds the maximum set boost pressure of the turbo alone then a spike in pressure will be seen. if the bypass acts too fast there will be a pause or dip in boost pressure. the perfect boost curve is one that raises gradually without dips or spikes.. hence the beauty of the twincharger!
The downside of this system is the amount of components and expense + complexity which requires more engine bay space, more money and time to setup and tune.
A single intercooler system can be used...
by running a cooler after both chargers.. probably the preferred option.
intercooler after the turbo but before the sc.. care must be taken to check sc air temps do not get into detonation teritory. lower compression ratio or water injection amongst other techniques could be used to offset this. 10psi out of a roots charger can get surprisingly hot!
#3 SC into turbo with bypass
SC blows thru turbo until turbo matches it for flow then a bypass around the sc opens to free up intake air before the turbo. again a twin intercooled system would be preferred to rid all heat from the compressed air. In a single intercooler setup, both chargers are before the cooler. (your turbo is providing top end boost and since this is a twincharger system aimed at big turbos for top end.. you'd be an idiot not having intercooler after turbo!). The bypass valve also needs careful tuning on opening rate to prevent any dips in the boost curve.. if bypass opens too slowly.. as the turbo outflows the sc, it will suck a vacuum into the piping after the sc, thus restricting how much air the turbo can flow (reducing top end power). if bypass opens too early.. ie before the turbo matches flow rates you'll get a dip in boost. once turbo has matched flow of sc.. I can't see any disadvantage of snapping bypass full open.. tho I see prolems occuring when actually running at that exact switchover point.. say driving up his on 3/4 throttle (whereever that point is). I could see the bypass having indecision issues heehee (open, close, open, close).. therefore a gradual open system is preferred.. ah but how do we control this?
So basically I'm going to attempt No/3 on my wee imp engine ;D
Did a quick cad drawing too (and I mean quick!!) so I could understand what I'm aiming for!
So with the ideas set in my mind of the parts and components needed to make this work, Ive come up with a brilliant idea for a valve
its so simples its clever lol.Found the main part, the supercharger now most would go a grab a used mini supercharger as thats the norm, easy to find, cheap, and basically new still.
But I knew from a previous attempt at this that the mini supercharger is far from mini! so I went hunting and managed with a stroke of luck to come across a super neat half sized eaton charger that is used on the new TSI golf (Twincharged from factory).
Here it is, problem is finding out information about it, no data sheets are online and eaton have been useless so far but will keep trying! I really need to know its max rpm range and psi ect and the pulley size needed on the crank (think I might just go stick my head under a golf at the dealers ;D
Now that I have it in front of me I'm a little confused as to which is the air in and which is the air to carb? (turbo in my case) can someone confirm for me please?
Just in case you don’t know the car in question
Thanks
Chris
