possible to swap between AFM's on the run?

[EldarO]

If this was an easy, simple, and cost effective thing to do, you would be seeing it alot more often in demo cars, and cars built for racing.

the end result being, that manufacturers have found that the most cost effective way of reducing lag, is to simply use a sequential twin turbo setup.

i reiterate, if this was easy, it would be done alot more often.

not saying i wouldnt LOVE to see it, i love projects, and i love seeing the outcome, if you can see a worth while way of doing it, go for it champ

Eldar.O.

[oldcorollas]

Lambolicas first pic seems to be the simplest, easiest method for hooking up twincharging. simple, effective, smooth transition when the SC turns off (and when SC turns off, remember that it stops pumpign air instantly!)

if you have two AFM's, and both are giving readings.. how do you add them together for the ECU to know what air flow is?

for cheapest and easiest... hook it up with turbo blowing into SC... heck, you don't even need to turn SC off once the bypass is fully open, as it will just be freewheeling in there (so you may as well.. but it'S easier not to have to re-engage it later)


OR, you could just run the perfect size turbo and minimise lag..

OR you could run a twinscrew SC and eliminate RPM and boost limits of the toyota SC, and have no lag like turbo...

all depend how much boost you want to run.... if you are after 30-40psi and still want something driveable, then twincharging is for you
do it.. you know you want to

[myne]

The easiest way would be to use a map sensed ecu.
It shouldnt be *too* hard to swap an AFM ecu to a Map sensed one

[Lambolica]

Like Oldcorollas said if there is 2 AFM's how do you get them both to read to the ecu and going back to your origonal question if you were to shut on off when the S/C disengauged and the turbo on turn on you may well get a kick in the engine curve unless the 2 AFM were reading the same.

if there is 1 AFM it will not really give a false reading as it is measuring air flow. weather N/A, supercharged, turbo or twin screw the engine will draw whatever air it requires and will be read by the AFM. It's not going to read twice as much air because there are 2 items drawing it through and besides if there is that much air you will want that much fuel.

[crowncustom]

If I could remember the link to this certain guys web site in America this would be spot on for u as he has already done this with a 4A-GE in a AE-85 or 86 GT-S RWD.He had the full ins and outs on how he twin charged his Corolla but sorry I cant remember the site,maybe there is someone out there that has come across it while surfin' the net.It was a white and black Corolla.
Cheers Brett.

[RAd28]

Like Oldcorollas said if there is 2 AFM's how do you get them both to read to the ecu and going back to your origonal question if you were to shut on off when the S/C disengauged and the turbo on turn on you may well get a kick in the engine curve unless the 2 AFM were reading the same.

exactly the question i'm asking... well kinda, obviously the ECU could only read 1 AFM at at time, so it would be a matter of switching between the two at such time as they both read the same...

if there is 1 AFM it will not really give a false reading as it is measuring air flow. weather N/A, supercharged, turbo or twin screw the engine will draw whatever air it requires and will be read by the AFM. It's not going to read twice as much air because there are 2 items drawing it through and besides if there is that much air you will want that much fuel.

the problem i see with 1 AFM, is that as the turbos come onto boost, they're gonna be drawing in air, but the charge wouldn't be able to go into the engine because then you'd have the air flow compound ontop of the s/c boost... and once you disengaged the s/c there'd be a massive step... (if you get what i mean) so you'd need to run them independently, allow the turbo charge to vent to atmosphere until it reaches s/c boost (to allow a smooth transition), and so if you were drawing this air in through the AFM it would give a false reading... 'cause the air coming through it, isn't going into the engine... (follow?)


the only way i could see this working at all.. would be to use strictly s/c or turbo... and not phase between the two at all... but it would require the transition to take place at the exact moment (if not a moment before) the turbos hit boost equivalent to what the s/c was producing (would we need to account for volume of air flow? i would think so).

*light bulb* could you blow through the AFM, rather then draw through????????

crowncustom - THIS the link you meant???

[crowncustom]

No not it,but very interesting site.The Corolla concerned was actually a 70 series the same as Nevs in Africa on this site.
Cheers Brett.

[mic*]

I want to know why the hell you would want to bypass the S/C after turbo starts boosting...

Sounds friggin stupid to me. What a waste of potential efficiency.

Stu maybe twin screw (lysholm?) style S/C's have made some advancments lately but the achillies heel of them has always been street practicality. Massive parasitic drag on idle or cruising unless its clutched and no distinct advantage over a typical Eaton (make that a helical Eaton) until 10+ psi... Im sure im not telling you anything new, but thats why i reckon not many, if any, i dont know anybody - who uses em on a street car.

[oldcorollas]

lysholm does generate a bit of heat on cruise... but you aren't boosting at cruise.... manifold has vacuum.. so you turn it off you definitely DON'T need the SC on at idle either...

lysholm has much less parasitic drag than roots.

the reason people don't use them is because they are expensive, esp compared to a second hand SC12/14 or eaton M45/M90... ppl see them, don't understand the benefits (for high boost apps) and don't understand why paying 2K+ for an SC is any better.

sure for 10psi there is not much advantage.. but if you bought a twin screw, it's because you want to run more than that...
seen anyone running 20+psi successfully with an SC14?

even if i had a V8, i would much rather a Ken Belle or a PSI screwcharger than a bodgy eaton

[mic*]

I totally agree stu. You dont buy one if you are looking at 10psi. But thats kinda the rough mark where a lot of people are shopping give or take - for street use - hence the education hole.

I havent tried but i wouldnt imagine it is physically possible to generate 20psi differential across a roots (helical or straight) S/C. It wouldn be making much more than heat over 15psi.

Im gonna go check that lysholm has less drag than roots. I dont normally disagree with you on anything and there is no room for confusion here it's pretty black and white - they do or they dont.

Male female rotors and internal compression must have a price me thinks...

[myne]

I'm sure you could get 20psi fairly easily.
It'd just become wildly inefficient before the revs got high enough to use.
Think 3:1 pulley with a redline of 3000rpm

[oldcorollas]

eaton M45

eaton M90, 1.5L/rev
http://www.automotive.eaton.com/prod...argers/M90.asp
10psi (1.6 pressure ratio), 12000rpm (520cfm= 14m^3/min)
= 44hp (32.8kw)
outlet temp = 88C

Lysholm
http://www.opconab.com/index.asp?sPa...angID=2&cID=14

lysholm 1600 (1.6L, 1.35 internal compression
10psi (1.6pressure ratio), 14m^3/min
= 17kw = 22.8hp, outlet temp about 85. but this is steady thru whole flow range.
this is for SAME flow, SAME pressure.

lysholm 1600 using 44hp will do same flow but 2.2 pressure ratio instead of 1.6

lysholm 1200, 1.2L/rev, will use 20kw (27hp) to flow 14m^3/min at 1.6 ratio

lysholm 2300 will also use about 17kw (23hp) for 14m^3/min at 1.6 pressure ratio
using 44hp, it will flow (at same pressure) about 22-23m^3/min
ie, 65% more air at SAME pressure and power draw as the eaton M90
BUT, it has flow potential of 28m^3/min at 2.2 pressure ratio., ie twice the flow at twice the pressure (but uses a lot of power to do so 70kw)

this is from data taken from the manufacturers sites.
these flows are roughly what you would require for a 2L motor at around 1.7-1.75 pressure ratio... roughly....
i would much rather use 17kw to provide this pressure than to use 33kw to do the same job. and this is only for 10psi!!!! above this pressure, the roots style gets very inefficient. 33kw on lysholm does 2.2 pressure ratio, not 1.6.

straight lobed SC is even less efficent than the twisted lobe eaton

20psi on a straight or twisted lobe rotor? find me some flow data on them at that pressure
you may be able to get it, but more from temperature increase than extra airflow....

[mic*]

Lysholm superchargers are similar to the modified roots type, but the impellers are dissimilar. One is a male rotor of three or four lobes and the other is a female rotor of five lobes. The Lyshlom superchargers are used more in applications where the boost pressure is over 13 PSI. The reason for this is that the supercharger compresses the air to a high degree inside the supercharger and it decompresses as it enters the plenum. The advantage to this is that the air in the plenum will not back flow into the supercharger as the pressure in the supercharger is always more then in the plenum. The side affect to this is higher heat and more parasitic drag then the modified roots type in non and low boost conditions.

I just picked that up from the first web page i read.

Also Myne, for the same reason but in the opposite context i DO NOT beleive you would get 20psi out of a typical roots design - once you have 15psi give or take in the plenum - the S/C will only be able to "hold it at bay" coz everytime the S/C chamber opens to displace air into the plenum 15psi tries to pop back through it. But this is just an opinion so is open to be proved wrong.

[mic*]

Hang on stu, i know they're more efficient in operation. Its when you dont want boost - which for race purposes is never but is why i beleive the street market basically doesn exsist...

(still taking in all your material before you make a fool of me... )

[oldcorollas]

http://www.gadgetonline.com/super.htm
this page yeah?

The modified roots type is the best type of supercharger to use until the boost pressure exceeds 13 PSI. At that point the pressure in the manifold starts to exceed the pressure in the supercharger housing and it starts to backflow into the supercharger and decreases its output and the heat generated really goes up. Above 13 PSI the better supercharger would be the Lysholm type. It is said that the compression of the air occurs in the plenum after it leaves the supercharger in the modified roots type supercharger unlike the Lysholm where the air is compressed inside the blower and then decompresses as it leaves the blower and enters the plenum. The advantage with the modified roots type is that it has less parasitic drag on the engine when boost is not needed. The Eaton superchargers also use a bypass valve that equalizes the pressure on both sides of the impellers when the engine is operating in vacuum. This takes more load off the engine and reduces the heat generated in non-boost conditions. The Lysholm is still compressing air internally even during non-boost conditions and this generates heat and has more parasitic drag on the engine during non-boost even with a bypass valve. Mercedes Benz does use some Lysholm superchargers on their super cars and they employ a clutch to disengage the supercharger from the crank shaft during non-boost conditions to counter the negatives of the Lysholm superchargers.

for a start, the modified roots always discharges 1atm pressure air.. no boost.. compression occurs in the exit port of the SC.. i am not sure why they say that below 13psi, the air does not backflow into the modified roots SC.. doesn't seem to make sense.

and i have no idea why you would set up an SC to run when boost is not needed!! there is no point, and, as he stated, turning SC off will negate the negative effects of the lysholm SC

turbo is much better for sruise conditions than SC, of this there is no doubt.. but SC would not be used for a car where you did not intend to drive it hard