[Paparoach]

Online article:

Now let us differentiate BOV's, diverter and bypass valves. First, a blow off valve (seen top right) is common to high performance applications in that it provides the least bit of compromise. A BOV essentially releases this pressure straight out into the atmosphere. Quite often you will find that these units take on particular shapes, making them resemble musical instruments. I guess some people out there really like to flaunt their gadgets. Just wait ti'll you see how much they impress the ol' 5-0. Aside from this legal dilemma, the second problem you encounter with BOV's is that the mass air flow sensor will cause the engine management system to "think" that the air will go into the engine and in turn will release an appropriate amount of fuel for it. However, a BOV system will vent this air out before it gets to the injectors causing your mixture to run lean. In turn, this will result in unburned fuel to escape into the exhaust system. This is why you often see flames and hear those "pop's" in rally cars. It is unburned fuel exploding in the exhaust system. Doesn't take a genius to figure out that this is not the smartest application for the day to day car. For this reason, reasonable tuners will usually employ a bypass or a diverter valve (see left). These units essentially redirect this pressure back behind the compressor causing the net flow of air to remain constant. This in turn slows the turbine down gradually and allows the air flow sensor to work appropriately.


Is this wrong?

[Paparoach]

If making a custom turbo why would I go BOV then except for the sound then?

Is it more difficult to install?

[darkpuppet]

Paparoach,Jun 9 2004, 07:06 PM Wrote:Online article:

Now let us differentiate BOV's, diverter and bypass valves. First, a blow off valve (seen top right) is common to high performance applications in that it provides the least bit of compromise. A BOV essentially releases this pressure straight out into the atmosphere. Quite often you will find that these units take on particular shapes, making them resemble musical instruments. I guess some people out there really like to flaunt their gadgets. Just wait ti'll you see how much they impress the ol' 5-0. Aside from this legal dilemma, the second problem you encounter with BOV's is that the mass air flow sensor will cause the engine management system to "think" that the air will go into the engine and in turn will release an appropriate amount of fuel for it. However, a BOV system will vent this air out before it gets to the injectors causing your mixture to run lean. In turn, this will result in unburned fuel to escape into the exhaust system. This is why you often see flames and hear those "pop's" in rally cars. It is unburned fuel exploding in the exhaust system. Doesn't take a genius to figure out that this is not the smartest application for the day to day car. For this reason, reasonable tuners will usually employ a bypass or a diverter valve (see left). These units essentially redirect this pressure back behind the compressor causing the net flow of air to remain constant. This in turn slows the turbine down gradually and allows the air flow sensor to work appropriately.


Is this wrong?

a good portion of that write-up is wrong...

the author needs to be flogged.

if you put more fuel in than air, you run rich.... and a rich running engine is not the cause of the flames in WRC/race cars. That's caused by timing being pulled so that the air/fuel mixture has a chance to go out the exhaust port, into the exhaust, and then is ignited to keep the turbo spooled between shifts.

that, and as the flow of air is concerned, the air is pumped back in-front (to the inlet) of the compressor, and subsequently after the MAF (between MAF and compressor), to let the compressor suck in the extra air, without drawing it through the MAF.

BOVs are suggested because they are slightly quicker, and sound a lot cooler, but if you're running a draw-thru MAF, you can save running rich between shifts, wich can be hard on the engine in the long run.

[darkpuppet]

Paparoach,Jun 9 2004, 07:10 PM Wrote:If making a custom turbo why would I go BOV then except for the sound then?

Is it more difficult to install?

You only really need to go BOV if you plan on running highboost, high horsepower applications, or when you're running a MAP or blow-thru MAF (which you would need to do with high horsepower applications)

in this case, you'll have a lot less grief tuning/running the car if you go bypass... bypass requires plumbing to divert the air to the inlet tract, so BOVs are simpler in that manner a well... but it's not that big a deal..

[Paparoach]

I thought he was screwy...more fuel rich. The next line...lol.

Okay still undecided there.....but learning thanks guys.

I am sure I will have another question in about 3-4 minutes.

No one will help me with the compressor maps though ;)

[darkpuppet]

Paparoach,Jun 9 2004, 07:22 PM Wrote:I thought he was screwy...more fuel rich. The next line...lol.

Okay still undecided there.....but learning thanks guys.

I am sure I will have another question in about 3-4 minutes.

No one will help me with the compressor maps though ;)

the point about compressor maps is to make sure that your required airflow and pressure ratios through the RPM range fall into the highest possible compressor efficiencies. The lower the efficiency, the more heat that is generated....

I don't have much time to go into the specific details, but check out this article. It seems to be chock full of info.

But really, you don't need to worry too much about compressor maps since what other people are running provides a good indication of what you should be running. You don't need to pretend you're a pioneer in focus turbos here :P

[darkpuppet]

oh, and if you haven't learned enough from that article..

check this one out..

I'm ready to go tackling the theory of relativity

[Paparoach]

I read the first one that is why I was asking about our engines VE...but it isn't that simple to figure out. And fuk everyone I want to do it myself..okay not myself but I would love to figure it out.

But I haven't read the second one. My brain is like a sponge.

[darkpuppet]

Paparoach,Jun 9 2004, 08:00 PM Wrote:I read the first one that is why I was asking about our engines VE...but it isn't that simple to figure out. And fuk everyone I want to do it myself..okay not myself but I would love to figure it out.

But I haven't read the second one. My brain is like a sponge.

0.00134

that's the measure of air mass at standard air temp and pressure for one cylinder (taken from the scalars table in our ECU)...

that's one number you need for engine VE :P

[Paparoach]

darkpuppet,Jun 9 2004, 04:09 PM Wrote:

Paparoach,Jun 9 2004, 08:00 PM Wrote:I read the first one that is why I was asking about our engines VE...but it isn't that simple to figure out.  And fuk everyone I want to do it myself..okay not myself but I would love to figure it out.

But I haven't read the second one.  My brain is like a sponge.

0.00134

that's the measure of air mass at standard air temp and pressure for one cylinder (taken from the scalars table in our ECU)...

that's one number you need for engine VE :P

Thanks I think...read read and read

[Paparoach]

Okay I am reading the second article....good so far then I get this:

Using the torque curve published by Mistubishi for the stock turbocharged engine, I estimate these volumetric efficiencies for our engine at wide open throttle or full load as 90% at 2000 rpm, 95% at 3000 rpm, 93% at 4000 rpm, 90% at 5000 rpm, 81% at 6000 rpm and 75% at 7000 rpm.

Estimate what the hell, how does he get these numbers any idea guys?

[DD1]

TURBOS rock I know
;)

[arskiker]

..

[Paparoach]

Further in the article he say he says the VE is derived from a torque and horsepower chart published by Mitsu....I wonder.

This is very very interesting. Especially when he explains that the better your engine flows the less boost you get with the same air flow at a given RPM.

Neato

[naz]

i tried to pick up TiG welding a while back.. i found it pretty hard. i'd have needed to have really put in a good effort.. like practicing daily, doing like... shelves and other simple stuff.. and maybe after a few months i could have made something useful.. i think MiG is probably easier to pick up.. maybe i should have done that.. but what i am trying to say is that.. this isn't something you casually decide to do.. its a lot of time and effort... and you will need many many hours on that shop's equipment

another thing to think about.. do you have an unmodified vehicle for your daily driver? i think a lot of people overlook this very important fact.. stuff is going to break, things will go wrong..

do you have good free cash flow? this is related to "stuff is going to break, things will go wrong.. "

EDIT: personally, i think unless you REALLY like fabrication and constantly working on your vehicle, the best way to get turbo is to buy a factory turbo car...

[Paparoach]

Well a couple of good things:

1. Cars I have plenty of them...I work at a dealership
2. As for shops I actually have two where I can practise (one of the mechanics here and the shop next door) also have access to two benders
3. I have a very good in at a machine shop (guy is a car nut too)

Free cash....it is called credit...lol.

This is not something I am going to do right away...first things first is I am enrolling in a welding course, from there I can practise on many a thing.

As for fabrication count me in...I love working with my hands and I also am a geek. That is why these compressor maps are fukin killin me.

But thanks for the heads up, I just wish someone on the jet would answer my question about our engines VE :lol:

[darkpuppet]

I would venture to say that unless your daily driver is a tow truck, that working on your own engine is a bitch.

also, I would say that worrying about compressor maps and engine VE is not necessary at your point in the game. You're going to be so far out in undiscovered country with just fabbing your own header/FMIC/ etc, that you're best to just get a turbo that everyone else is using for your HP needs.

I would go with a good starter turbo that everyone else is running, and when you want to get all fancy-schmancy with a custom turbo and high HP numbers, then sell what you started with, and buy new.

The thing is worrying about individual compressor maps, and the stock engines VE in relation to them is going to lead you to the path of 'most expensive turbo'.. stick with what is cheap and what works. And besides, the credit card companies get large enough Christmas bonuses from just myself :P

[Paparoach]

See I know basically what everyone is running from reading the Jet and listening to Jay and Rob....but

I just need to know...sounds stupid but for myself I need to know how to figure this stuff out. I am just that type of guy especially when it comes to math sheat.

So Puppet find me the VE and stop posting.... :lol:

[darkpuppet]

yeesh.. fine, here it is: calculating volumetric efficiency

:D

[Paparoach]

darkpuppet,Jun 10 2004, 01:44 PM Wrote:yeesh.. fine, here it is: calculating volumetric efficiency

:D

Now I have grown to love you ;)

Thank you very much....off to reading.