possible to swap between AFM's on the run?

[RAd28]

hey guys...

been pondering the possibility of twin charging (again) and i've come to a solution i think would be quite simple (though not true twin charging)... only question i really have is this... Would it be possible to have seperate AFM's, and swap between the two at the flick of a switch... assuming the pipe work allowed... i reckon you should, because i don't believe there to be any kind of "start up proceedure" for them since you can just jump in the car and hit the start button, i don't see this to be much different from the first reading an AFM would get if you were to switch between one and another on the run.

and i know it'd be easier to use a stand alone ecu, with map sensors... but it'd be cheaper this way...

any opinions?

[-=DV=-]

mate i dont see why not, but at the cost of another afm, moving whatever u may need to to create the space for it, and the initial cost of all the work involved with twin charging anyway, why cut corners on something as crucial as what decides ur fuel/air ratios and could possibly destroy ur engine in the blink of an eye if every1a assumptions were incorrect?

[EldarO]

car stalls if theres no AFm

it will Idle, but as soon as you rev it will die.

I know this from runnign my supra without the afm plugged in.

Eldar.O.

[ATMO_BT1]

if you keep the rpm under a certain level i believe the car will run without an afm. In my rb30's in the past i have blown 3 or 4 afms and always made it home by keeping the rev's under 1500rpm.

[mrshin]

Uhmm... Why? Why can't you use one AFM that's big enough for the job and pass all the intake air through it? Would seem a lot more logical to me!

[RAd28]

well see, i've thought of all those points, cost of new AFM, making space, more logical to use a single (bigger) afm... my idea is to use a stock SC14 supercharger, over driven so it makes 8-10psi boost at around 3-4000rpm (or once turbos come on boost) and is switched off via a clutch at such time. the reason for 2 seperate AFM's is because the best spot i can see to install the supercharger is where the air con compressor once resided, except i'd need to remotely mount the oil filter (why not fit an oil cooler at the same time?) this way, i could tee in the supercharger flow just before the plenum (valved of course). but once the car hit (turbo) boost, the supercharger switches off, and the turbos take over... biggest problem i see is the supercharger clutch taking a beating although you could make it's life easier with a manual override for traffic etc. doing it this way i BELIVE you could retain the stock ECU too, since boost never really increases over stock, just means you get rid of lag...

and i'll need 2x AFM because it'll make life a shit load easier to use a switch between the two, as oppose to running piping from one side to the other, although there's no reason i couldn't if i absolutly HAD to, just trying to find alternates..

and 2 pod filters under the bonnet would make you wonder whats going on... no?



*edit* oh... and my car wouldn't start with out an AFM... tried to start it before we mounted the blow off valve, and it wouldn't, as soon as we mounted it, it started first go.

[wilbo666]

I'd use a single AFM, and run a pipe over...

Also do SC14's like being pressurised or will you need a one way valve to block turbo flow back through the SC?

Cheers
Wilbo

[Lambolica]

Why not just use 1 Pipe and a bypass setup?

Basically looking at a stock 1G run air from the AFM through the turbos and straight to the plenum as it does from factory. from there locate the S/C in the factory location run a pipe from the outlet of the s/c to the pipe just before the plenum. and a second pipe from the inlet to somwhere near the plenum but in front of the outlet pipe. between the 2 pipes have a buttefly to direct air flow to either the S/C of bypass it.



.................................................. .Butterfly
----> AFM ------> Turbo -----------> ---------/---------> ----------> I/C -----------> Plenum
...............................................\__ __S/C____/

use an old throttle body as the butterfly and set up a BOV style (or wastegate) so that as pressure builds up behind the S/C it triggers a linkage to open the butterfly. If you use a throttle body you could set the TPS so that when the butterfly opens to WOT the S/C clutch shuts down. meaning there is little of no retriction to the turbo flow.

[RAd28]

wilbo - single AFM with a long pipe is a second option... just wanna give the 2 AFM's a shot... for shits and giggles if nothing else...

lambo - i'm not 100% sure what you were saying.. but from your awesome stick diagram, and parts list, i think i can figure it out.. except it looks like your drawing air for the supercharger from the boosted side of the turbos... IMO this would cause problems...

[Lambolica]

Yeah true you could put the first pipe to the S/C before the turbo. I just thourght drawing air through them wouls assist with spooling. Didn't think it right through.

Yeah the text is complete jibberish... I'll fix that later... I was describing an idea then drew somthing else.....

So...

...............................................But terfly
----> AFM ------>------ Turbo ----->------/--------->----------> I/C -----------> Plenum
.......................\____S/C______________/

[wiso]

when twhin charging wouldn't it be possible to have the sc run first, feed into the turbo, then out of the turbo into the intercooler than into the plenum. I am thinking about this twincharging idea on my 4agze, it seems very likely to work, and when up top end if the sc can't flow enough air for the turbo you can have a oneway valve going from before the sc teeing into just beofre the turbo so extra air can flow through the turbo.

does this sound reasonable?

[mic*]

What is the problem you would foresee with the S/C positively displacing pre-boosted air?

I would suggest underspinning the S/C (8-10psi is stock boost for a SC14 with standard pulleys on a 1G - and boost is constant with revs as S/C displacement is set by pulley ratio which does not change with revs) so you get a little less sever boost down low - say 6-7psi. Couple it with a moderately sized turbo remembering that whatever is in the intake right before the S/C (say 8psi boost from the turbo - 22.7 total) will be boosted again by the S/C.

eg: In this case if S/C = 7 psi or 0.5bar for simplicity, 22.7 psi absolute (the 8 psi boost from turbo) will become 34.05psi absolute, or 19.35psi boost.

The only problem i see with the S/C positively displacing pre-boosted air is you get out of your depth VERY QUICK. But thats the beauty of twin-charging....

[mic*]

The hardest part is sizing the turbo for the job.

[RAd28]

hate to break up the party, but the whole reason i plan on using a supercharger, is simply to eliminate lag, run the supercharger, and turbo charger independently, and you'll find the turbos will spool faster anyway since the supercharger is pushing a whole heap more air through the engine, and out the exhaust (where the turbo feeds)... i just wanna know if i could switch between AFM's... OH... and i thought of a glitch with using a single AFM and running both off the same... what happens to the AFM as the turbos start to come on boost, while the S/C is running... you'll get a false reading... 'cause the point really is to make the transition between S/C boost, and turbo boost as smooth as possible... so really, you couldn't have them swap until the turbos were making the same boost as the supercharger... hmmmm....

now i've raised that point... i find myself in a bind... *off to think some more*

[RAd28]

think of the most 'cost effective' (read: CHEAP) way to bolt on a supercharger, to reduce/eleminate lag... and that's what i want (FOR NOW)

running a kick ass single turbo later, with a supercharger assist and standalone ECU is entirely possible...