Boost on turbo gas engines?

[Gord]

Kind of a stupid question...

How is boost raised on a turbo gas car? I know you can change the chip/ecu to do it, but how does it work? Fueling is then raised after more boost is requested to keep from going lean? Are there chips (and is there a benefit) to just play with fueling?

Thanks,

-Gord

[ADAM]

boost is raised by modifying the signal to the wastegate....

depending on the fuel system...fuel will either be compensated for or not...

[ADAM]

for cars that are using the street ECU programming there are large benifits to changing the fuel maps......OEM fuel maps are designed for fuel economy and emissions....which are not close to what they should be for maximum power....generally turbo engines make the most power at 12:1 to 11:1 air fuel ratios...

to raise boost properly, you eith need to rechip...or get an external boost controller....

in either case..most of the stock turbos cannot be operated too far over stock boost levels without producing alot of heat...

[Logan]

VW boost levels are controlled by the computer, so yes, changing the computer on a 1.8T can increase your boost level.
The wastegate that controls the boost is controlled by the computer.
Other cars (like mine) are controlled by mechanical methods. The computer doesn't control the level of boost, so I can plug by boost controller into the wastegate vacuum line, which allows me to fool the wastegate into thinking more boost is actually stock boost.
My car is really freakin' rich, so a few extra psi of boost doesn't hurt it.
Problem here is that in order for better fueling if I want even more boost means I have to have some method of taking control away from the computer. There is no chip available for a mazda, so I have to buy a standalone or an piggy-back computer.

The simple answer: boost is controlled by the turbo's wastegate, you change the wastegate signals (electronically or by vacuum) to increase the boost.

[Gord]

Good info...

So, just adding more fuel won't in itself raise the boost level, the wastegate has to be held closed for longer to allow more pressure to be developed, right?

[Martini Focus]

Yep that's right.

[JAYh]

You can also raise it manually (i.e. rather than electronically). An old Talon trick is to build a boost controller for about twenty bucks out of hose fittings. (It basically restricts the amount of air that can pass through the wastegate - i.e. making more pass through the turbine and spinning it up further.) Let me see if I can find you the website...

- J

[Greg F]

Just make sure to get a good Compressor Bypass Valve, commonly called a blow-off valve (Taylor will explain further, haha) before you think of doing this, or you could shorten your turbo's life considerably.

The 2G Talon has such a crappy CBV that simply by installing an adjustable one, you can hold slightly more boost, and maintain it, especially during throttle modulation.

Make sure you adjust the new CBV properly or you can really mess up your turbo as well: too light on the spring and the turbo will work too hard; too tight on the spring and the turbo will 'ping.' Either way, there'll be problems with turbo life.

[Gord]

So, I have a 1.8t in my Passat (currently stock motor wise). As Adam and Logan have said, it may be possible to get more power without having to raise the boost (turn up the fuel)?

I'm looking at next years CNAC rules and trying to determine if there is stuff I can do to make the most of the class I run in. Currently, all that is in the car is springs, so it automatically goes to SS, but with a few points to play with.

One of the things I have noticed in the SS allowances is that chips/ECU's are free provided they do not raise the boost directly. So if there was some power to be had by just fueling, no points have to be taken for a power increase. Kind of nice, but might not work for the 1.8t.

Then again, I'm not sure what else I would really want to do to it. Lots of stuff is free in SS as it is, and the power is already good.

-Gord

[Logan]

Gord, you may be able to get power by leaving the boost stock, by doing things like freeing up the air flow, changing cams etc.
But just turning up the fuel will probably reduce your power.

If you want more power, install a chip and take the two points for boost controller. Probably the best way to go.

[finboy]

Originally posted by JAYh
You can also raise it manually (i.e. rather than electronically). An old Talon trick is to build a boost controller for about twenty bucks out of hose fittings. (It basically restricts the amount of air that can pass through the wastegate - i.e. making more pass through the turbine and spinning it up further.) Let me see if I can find you the website...

- J

dawes device??

http://www.j-w-racing.co.uk/acatalog/Dawesdevices.html

[NOSfly]

Sometimes the boost will increase because you have increased the airflow through the motor,by altering intake,exhaust,etc.I picked up 3psi after installing a free flowing exhaust in place of the very restrictive stock one.I would bet that the computer controlled wastegates would probably prevent that from happening,though.I'm currently running 25psi on pump gas.

[Logan]

Originally posted by NOSfly
Sometimes the boost will increase because you have increased the airflow through the motor,by altering intake,exhaust,etc.I picked up 3psi after installing a free flowing exhaust in place of the very restrictive stock one.I would bet that the computer controlled wastegates would probably prevent that from happening,though.I'm currently running 25psi on pump gas.
When I opened up my exhaust, I didn't gain any extra boost pressure, but I gained a WHOLE LOT of decreased spool time/increased throttle response.

[ice/solo racer]

Did you say 25 PSI? Are you sure?

I've never known a of a factory turbo car to pump out more than around 10 with fuel cuts happening around 14.5 psi(new evo's are more than that if I remember right)
You have this on a 3 cyl sprint right?

[Logan]

Originally posted by Greg F
Compressor Bypass Valve, commonly called a blow-off valve
Actually, these are different.

A blow-off valve will vent the extra pressure directly to the atmosphere.
A by-pass valve vents the extra pressure back into the intake system (after the filter, but before the compressor).
Blow-off valves are commonly used in vehicles that have Manifold Absolute Pressure (MAP) sensors, while by-pass valves are used in vehicles with Mass Airflow Sensors (MAS).

MAS measures the air once, and if you blow it out to the atmosphere, the computer doesn't know what happened to it, causing the engine to run rough just after the blow-off (assumes air is still in system, and injects appropriate amount of fuel anyway).
MAP measures the pressure, the computer uses that to know how much fuel to deliver.

[Greg F]

Originally posted by Logan
Actually, these are different.

A blow-off valve will vent the extra pressure directly to the atmosphere.
A by-pass valve vents the extra pressure back into the intake system (after the filter, but before the compressor)..

Yup, like I said, "commonly referred to" not, "correctly referred to..." ;)

It'll be much less painful to ask the yahoo behind the counter for a blow-off valve instead of a compressor bypass valve. :o

Hmm, now do I let everyone know I'm thinking of running an 'exhaust bypass' next year? :rolleyes:

[glh]

Opening the exhaust is the safest method inlarging the turbo outlet and front pipe and removing the cat can gain as much as 50-75 lbs of touque alone and it helps every thing run cooler .

[njansenv]

Turbo Dodge guys prefer a 'grainger' valve. It's an industrial pressure release valve available at McMaster-Carr for $7.33USD. I just installed one on a Daytona TI. It worked VERY well. We're now boosting 14.5psi or so, and boost response is MUCH better.

Refering to the post about 25psi etc. The Dodge guys commonly run over the fuel cut (14.7psi) by installing a zener diode. Extra fuel can be added with coldstart injectors. It's not unheard of to run 25+psi with the stock turbo. Usually running 11's-12's at that point;).

Nate

[glh]

i run a turbo smart boost controler much better that a grainger i had a grainger fail and it cost me a motor also tricking the map is dangerous as well my set runs a 3 bar mar computer set up with timing and fuel curvs to 25 psi and +40 injectors and i can still only run 15psi on the track but it could easlly run 24psi for drag racing you get alot more heat build up road racing . just my 2 cents
steve

[tim@canspeed]

tricking the map is dangerous

Not if you are using the right equipment!

http://canspeed.com/images/SMT6small.gif

I'm just sayin:)

[max attack]

I'll add a shameless plug for Tim,great guys and great product!.

My crx is receiving perfect power as we speak,the corolla gets one as soon as the supercharger install is completed.