MR2 Owners Club Forum banner

1 - 20 of 26 Posts

·
Registered
Joined
·
735 Posts
Discussion Starter #1
If you were to twincharge (turbo into S/C)and leave the ABV enabled, once the turbo starts to go over the 8-10 psi the abv allows, would it flow enough air? (aplogize for the long sentence) Would this work, or is it just a pipe dream?

Sorry to beat the dead horse, but I can now afford to try this. Will take some time but anytihng does.

Also, i know that 3sgte swap would probably be better in the long run, but I have a odd interest in trying to twin-charge
 

·
Moderator
Driving MR2s since '89
Joined
·
4,138 Posts
No, the stock ABV would not allow enough air flow through it (if you're thinking of using it as an SC by-pass for the turbo) to not be a significant restriction. It's total cross sectional flow area is probably less that 1 square inch.
 

·
Registered
Joined
·
735 Posts
Discussion Starter #3
I understand that it wouldn't be enough by itself. But if you had the S/C switch off at around the same time would the combined area from the freespooling s/c and the ABV work?
 

·
Registered
Joined
·
1,612 Posts
What is ABV? Auto Bypass valve?
Im still just getting into the MKI world and this is the only place i can learn it as i have only a MKII :p
 

·
Registered
Joined
·
4,920 Posts
ABV is the air bypass valve. It is smaller than most blow off valves in area.

It functions to limit the boost of the SC to 8 psi, and must be defeated in order to run more, like when you put a bigger pulley on.

There is a guy on the board right now with a twincharge setup who has placed two boost guages in his sytem and he has shown that the SC presents a pretty big restriction.
 

·
Registered
Joined
·
1,612 Posts
I see, so its not the similar to a actuator which releases s/c pressure upon throttle shut?
Thats the only thing on the tacoma s/c....
the pully should be the one determining the amount of boost going into the engine.
I thought the s/c is roots type....damn i need to look at one upclose
 

·
Registered
Joined
·
4,920 Posts
this layout is not for just "adding a kit" to a SC car....

The only potential issue I see ( post what you all see ! ) is what happens when the SC is on and your foot is off the gas.. During shifts the BOV will open and vent the boost from the SC and the turbo. At partial throttle and cruise, the SC wont be on.. just mimic the factory SC supercharger control, turn the SC on at like 8 inches of vacuum so it is up and spinning when there is load but off when there is not load, like highway cruising. You could do this with a hobbs pressure switch or with a programmable output from your engine management. You can turn the SC off once the boost is at a higher psi than the SC provides alone as you will know by that time the turbo is fully spooled up and the SC is just free spinning with no load on it.


This will spool faster than the same motor with just the turbo, but peak power will be the same as the motor with only a turbo. ( at same boost)

the previous picture will spool faster as well, but peak power will be less than a motor with the same turbo alone. ( at same boost)

The benefit in both cases is you can spool a bigger turbo at a usable RPM, so you can benefit from exciting things like big turbine housings and low backpressure, and hopefully boost pressure higher than backpressure ( = magic things happening according to maximum boost)


EDIT:
Forgot to mention another key difference..in the SC after turbo setup, the turbo will be seeing a different load than a 1.6l engine.... it will be seeing the combine system of the SC and engine as its load... That combined system with a stock 8 psi pulley is about equivilant to a 2.5L engine.
( 1 + 8/14.5)*(1.6) = 2.48
this means that the nice huge garret you can stick your head into wont run into surge issues as early as it would on the 1.6l motor...
in theory the maximum sized turbo that could be run is bigger with that first setup because of this.
In actual practice you just need to look harder for the turbo you want to use and find somehting like:
http://www.turboengineering.com/custom_performance_turbochargers/ht-series/ht200.html

which wil let you run 40-50 psi on a 1.6l ( assuming you had the octane and the motor could live)
 

·
Registered
Joined
·
24 Posts
parts question

This will spool faster than the same motor with just the turbo, but peak power will be the same as the motor with only a turbo. ( at same boost)
This is what I'm wanting, I have 4 available outputs from the Haltech, but I'll still have plenty of questions when the time comes. Right now I'm trying to collect all the pieces so I can have everything together when I start working on it. I hate trying to remember what went where a month later( me gettin old makes it worse). Looking at the factory setup, does there need to be a bypass or one-way valve to close off the supercharger when the turbo is boosting?
 

·
Registered
Joined
·
4,920 Posts
Weasy2k said:
I see, so its not the similar to a actuator which releases s/c pressure upon throttle shut?
Thats the only thing on the tacoma s/c....
the pully should be the one determining the amount of boost going into the engine.
I thought the s/c is roots type....damn i need to look at one upclose
it is very similar to what I think you are describing. The pulley does determine the boost going into the engine with the mr2 SC ( which is roots, you are correct) but the pulley is not actually 8 psi, it is more like 9.5 or something odd. the ABV bleeds off a bit of the boost to keep it to 8 psi. Some owners of completely stock cars can do the ABV mod and get 9.5" psi at redline in higher gears where the motor has less VE ( adds boost) and the intercooler is more heat soaked ( also adds boost)
note adding boost and adding to the amount of air actually getting into teh motor are 2 different things though.. which is why cams lower boost, but increase power.

Anyways, many owners do not end up getting more boost by doing the ABV mod as the SC's are just old, loose, and inefficient.
 

·
Registered
Joined
·
4,920 Posts
crxdad said:
This is what I'm wanting, I have 4 available outputs from the Haltech, but I'll still have plenty of questions when the time comes. Right now I'm trying to collect all the pieces so I can have everything together when I start working on it. I hate trying to remember what went where a month later( me gettin old makes it worse). Looking at the factory setup, does there need to be a bypass or one-way valve to close off the supercharger when the turbo is boosting?

CRX dad - if you follow the factory setup, which weasy2k
drew here:
http://www.mr2oc.com/showthread.php?t=79853&page=4

Thank weasy2k for this picture

you do not need anything to block off the supercharger. You can definately get away with just slapping a turbo on and calling it a day like 2tone has done, but there is extra power there if you can figure out a way to bypass the SC and turn it off.. then the peak power would be the same as the turbo only setup.

I am sure most twincharge setups will be like this rather than the diagram I drew as the way I drew requires a different intake manifold, and completely new plumbing for the entire inlet tract, so it is probably worth pursuing a more elegant solution to making this work good.
 

·
Registered
Joined
·
1,612 Posts
No problem Jared! You are helping me out alot as well on how this system is run on the MKI's.
The diagram i drew is basicly the easiest and most stock looking way to do things and it is the most commen. When you mentioned the fact that the peak power wont really be there then turbo alone, yea your right...the best thing to do at this point is buy a turbo that will put out alot more air so it kinda compensates for that. (a s/c doesnt make the best intake manifold)
So the best bet would be to remove or do the ABV "mod" so that it doesnt bleed the air.
Keep the indeas coming....twincharging is something that interests me.
 

·
Registered
Joined
·
1,590 Posts
what about running 2 throttle bodies, one at either end of a ge intak emanifold(basically combine a ae86 manifold and mr2 manifold) then run dual intercoolers like in the above picture. you could basically take an s/c car and ass the turbo unit and neither would get in the way of the other. the only problem i can see is the pressure from the either would blow straight through the others throttle body. you would need one way flappers after both throttle bodies or some complex way of it automatically switching from one throttle body to the other.

like this:http://www.we-todd-did-racing.com/wetoddimage.wtdr/wNzg5MDQyNnM0MTNkZmQzMXk1NDE=.jpg
 

·
Registered
Joined
·
1,612 Posts
I just dont see a real point in making sucha complex system :)
Its really simple to make this work and you wont notice the difference the other route would make, besides complications :p
MY 02 :)
 

·
Registered
Joined
·
4,603 Posts
Does anyone know how well 2tone's car runs? Or any other car that has a turbo just blowing through the SC? I am considering trying it, I would be running a HKS pulley and then run a T-25/28 so that I can make something like 13-14psi.
 
1 - 20 of 26 Posts
Top