BOV, Air Intake and FCD

I am planning on buying a BOV, an air intake and an FCD for my '91 MR2 Turbo... what brands would you really recommend in buying that can improve performance?

Any BOV you buy will rob performance, not give you any.

There is no reason to buy a FCD, unless you want fuel cut protection. Otherwise, you can eliminate FC for free by capping off the vac line to the OEM map sensor.

I recommend the K&N intake.

Any BOV you buy will rob performance, not give you any.

There is no reason to buy a FCD, unless you want fuel cut protection. Otherwise, you can eliminate FC for free by capping off the vac line to the OEM map sensor.

I recommend the K&N intake.



is it still safe to not get a fcd and just cap the vac line off?

Any BOV you buy will rob performance, not give you any.

There is no reason to buy a FCD, unless you want fuel cut protection. Otherwise, you can eliminate FC for free by capping off the vac line to the OEM map sensor.

I recommend the K&N intake.

Wait wait.. whats the difference of buying FCD, and capping off the OEM map sensor vac line?

willowlee, if you cap the vac line off you have negated the reason for owning an FCD. It would be pointless to do both.

Fuel cut is a built in protection device to save your engine from over boost. Fuel cut from the factory is set at 12 psi (91-93 mr2s and 16 psi on later MR2s).

A fuel cut defencer allows you to RAISE the fuel cut point. The maximum you can raise it to is 17.7 psi. If you want to run more than 17.7 psi of boost you HAVE to get rid of fuel cut.

The OEM map sensor only does 2 things:
*controls fuel cut
*operates the OEM boost gauge (which is worthless)

So, if you cork that vac line you will 100% eliminate fuel cut (and the OEM boost gauge will stop registering).

You can by an HKS FCD and raise the fuel cut.

The GReddy boost cut controller eliminates fuel cut ... so it is worhtless to buy it since you can eliminate FC for free.

Hope that helps.

Right now i am running 13psi but i get fuel cut at 14psi.... how much psi can a CT26 withstand if I am running standard engine with no heavy mods?? I want to know this because I am planning on getting rid of the fuel cut and set up my boost up to 15 or 16psi... will I have any problems with this?

Beyond 15 psi you are out of the CT26s efficiency range and you are increasing your chances of detonation without adding a significant amount of power.

General rule of thumb is keep the CT26 to 15 or less psi.

do you know where i can find a guide to cut fuel cut? any instructions in how to?

I'm not sure what you are asking.
Do you want to eliminate FC or raise it?

i want to eliminate it since i don't want to buy an HKS FCD.... that is what i want to do

Just cap off the OEM map sensor vac line

how dangerous can it be to run without a fcd? what can it do to ur car? is it worth it to get a fcd if lets say, i'm boosting around 15 psi or less on a greddy tdo6?

The danger is if you overboost ... FC protects you from this. The most you can hit is 17 psi.
Without FC, you can hit whatever boost ... assuming boost controller failure.

what do you mean by OEM??? Is it the same as the Vacuum Sensor (Manifold Absolute Pressure Sensor)??

OEM = original equipment manufacturer.

It's short hand for "the part that came on the car when it was new."

i only have to disconnect the vac line or the plug from the MAP??

If you want to completely eliminate FC, just cork the vac line. Do NOT unplug the sensor.

The ECU will see an error with no signal.
Corking the vac line just allows the sensor to never "see" boost.

1. BOV are not made to give you horsepower there made to stop air from backing up into your turbo when the throttle body is closed.
2. the OEM BOV from toyota is sufficient enough for a while eventually it will need to be replaced
3. the MR2's come with a deversion line on their BOV to re=route the blown off air back into the air filter side of the turbo allowing the turbo to spool faster once your in the next gear ( make no differnece if you come to a stop or get completly off boost)
4.the reason it robs preformance is because most aftermarket BOV blow the air right out of the intake tract and into the atmosphere, you have to get one specific to the MR2 with the deversion valve line :2cents:

you will never gain hp by getting a BOV, just the fact knowing that your turbo is safe from compressor surge

Just as a note, im running a totally stock Engine (3SGTE) and eliminated the fuel cut by just capping off the Map (little box in middle passenger side firewall Trunk side. and running 15psi approx on a CT26, seem to have no problems at all on stock configurations. But as said above over 15psi is getting pretty iffy on reliability vs power.

1. BOV are not made to give you horsepower there made to stop air from backing up into your turbo when the throttle body is closed.
True, but the wrong BOV set up will rob you of power.

2. the OEM BOV from toyota is sufficient enough for a while eventually it will need to be replaced
That is 100% false. As long as your OEM is not broken, you will not ever need to replace it. It is the best valve you can have at any boost/power level.

3. the MR2's come with a deversion line on their BOV to re=route the blown off air back into the air filter side of the turbo allowing the turbo to spool faster once your in the next gear ( make no differnece if you come to a stop or get completly off boost)

It is actually a recirculation pipe, not a "diversion line."
More important than helping boost into the next gear, the recirculation does not allow you to lose metered air which would mess up the A/F ratio.

4.the reason it robs preformance is because most aftermarket BOV blow the air right out of the intake tract and into the atmosphere, you have to get one specific to the MR2 with the deversion valve line
BOVs can also rob performance by how fast they can respond and how sensitive they are too respond. You get a poorly designed spring-based BOV and you are looking at slower response from a less sensitive valve that truly only works within an "ideal" boost range.

The OEM valve works perfectly at any boost level, responds instantly to changes in air pressure and is extremely sensitive.

you will never gain hp by getting a BOV, just the fact knowing that your turbo is safe from compressor surge
... but you can lose HP from a BOV.

Yea but the stock configuration gets old i never stated there was a need to change it, and like i stated earlier if you get the right good quality aftermarket BOV it should come with the right piping. and if thats false your telling me the stock BOV on a Supra can support over a thousand Hp at 40psi? and i see your point with the recirculation pipe generally deversion lines got to the exhaust side of the turbo to help spool up right?

Yea but the stock configuration gets old i never stated there was a need to change it
Why point this out? All parts get old/worn and will need to be replaced.
Why even say "OEM BOV from toyota is sufficient enough for a while eventually it will need to be replace" ?

the right good quality aftermarket BOV it should come with the right piping.
It has nothing to do with "piping," it has to do with valve design.
Most aftermarket valves are based on a spring.
Only one variation of the HKS copies the MR2's OEM BPV design.

and if thats false your telling me the stock BOV on a Supra can support over a thousand Hp at 40psi?
If it has the same design as the MR2s, absolutely.
Max HP has nothing to do with a BOV's ability to do it's job.
As for 40 psi of boost ... the OEM MR2 valves holds tighter the more boost you throw at it.

You really only want two things from your BOV/BPV:
1. Stay closed under boost.
2. Open as qucikly as possible off boost and shut again as fast as possible.

That being said, spring based valves will never hold more boost than the OEM valve and they will never respond as fast. They can't.
The more boost you run with the OEM valve, the harder it stays closed!

and i see your point with the recirculation pipe generally deversion lines got to the exhaust side of the turbo to help spool up right?
Incorrect. The OEM valve routes before the compressor to help spool, not the turbine. There would be no benefit to going before the exhaust side.

"Incorrect. The OEM valve routes before the compressor to help spool, not the turbine. There would be no benefit to going before the exhaust side."

i ment in general not on the MR2 only and the reason i pointed it out was simple would you rather replace your factory unit or realize that the 10+ year old valve isn't functioning at the 4th to 5th gear shift 99% on the throttle , the aftermarket BOV namely HKS is the only real one worth buying for this car because it works and its a little security in knowing it wont fail

Oh and I don't mean to sound rude I just thought I was right, thanks for the info.

i ment in general not on the MR2 only and the reason i pointed it out was simple would you rather replace your factory unit or realize that the 10+ year old valve isn't functioning at the 4th to 5th gear shift 99% on the throttle
I'm not sure you are getting what I am saying.
Unless the OEM valve is broken, it will function perfectly under any boost pressure, rpm, gear or horsepower.

the aftermarket BOV namely HKS is the only real one worth buying for this car because it works and its a little security in knowing it wont fail
The HKS valve is in no way, shape or form better than than the OEM valve, unless you value the BOV noise.

i just ment would you rather find out the factory one is broken because its old and warn when your romping on your car or just go ahead and get a brand new factory one and replace it rather than getting and HKS or Blitz? spend the money and get a replacement from the toyota dealership because what your telling me is that the factory one is best and insted of replacing it with an aftermarket one buy a new stock one that was my point i get what your saying