'03 Cobra

[Rootus]

The only issue was a lift throttle stalling problem that turned out to be a deficiancy with the speedbrain and negative MAF airflow and not related to the turbo system at all.

Speaking of negative MAF airflow -- is it typical of larger engines and turbos that you *need* to vent the BOV to atmosphere? Will said his car had a tendency to stall because of the air being released into the intake screwing up the MAF reading.

Dave

 

[Darkness]

Speaking of negative MAF airflow -- is it typical of larger engines and turbos that you *need* to vent the BOV to atmosphere? Will said his car had a tendency to stall because of the air being released into the intake screwing up the MAF reading.

Dave

Most stock turbo systems vent the BOV back to the intake, had a few turbo cars and were all like that. But it actually hurts the spool up on shifts or plainly when you let off the throttle.

 

[Rootus]

Most stock turbo systems vent the BOV back to the intake, had a few turbo cars and were all like that. But it actually hurts the spool up on shifts or plainly when you let off the throttle.

I'm thinking of bigger turbo systems, moving a lot of air -- like, V8 sized . Basically the only time it would come into play would be aftermarket. The consensus I've seen on turbomustangs suggests that most people say that atmospheric BOV has no advantage to bypass.

 

[Toddzilla]

I'm thinking of bigger turbo systems, moving a lot of air -- like, V8 sized . Basically the only time it would come into play would be aftermarket. The consensus I've seen on turbomustangs suggests that most people say that atmospheric BOV has no advantage to bypass.

I don't see why it would. I think people just like the sound of a BOV.

 

[Darkness]

I don't see why it would. I think people just like the sound of a BOV.

Dont quote me on this, but I read somewhere that a BOV actually prolongs the turbo life, because of when you let off the throttle all the pressure go back against the turbine wheel and force it backwards, hence also creating longer spool up times.

 

[Toddzilla]

Dont quote me on this, but I read somewhere that a BOV actually prolongs the turbo life, because of when you let off the throttle all the pressure go back against the turbine wheel and force it backwards, hence also creating longer spool up times.

They do prolong the life of the turbo. But that has nothing to do with whether it is bypassed to the compressor inlet, or blown off to the atmosphere.

 

[Rootus]

I don't see why it would. I think people just like the sound of a BOV.

That's what I've heard. But in the case where it causes the MAF to produce incorrect readings because of the disturbance of the air, I wonder if it becomes a requirement to vent it to atmosphere. I guess it would be a moot point if the MAF is setup as blow-through.

Dave

 

[Toddzilla]

That's what I've heard. But in the case where it causes the MAF to produce incorrect readings because of the disturbance of the air, I wonder if it becomes a requirement to vent it to atmosphere. I guess it would be a moot point if the MAF is setup as blow-through.

Dave

Ah, I think I understand what they are saying.

In a setup that is flowing a lot of air, when the BOV actuates and routes the air to the compressor inlet it's possible that there is so much flow/pressure that it blows backwards out of the MAF. I can see that.

When I had my vortech, I did a home made cold air intake for it, but I routed the bypass valve to close to the MAF and that gave the car a few hiccups, but when I moved it further away from the MAF and closer to the compressor inlet it went away.

 

[SLIGHTLY_INSANE]

I don't see why it would. I think people just like the sound of a BOV.

In some circles, can you say status symbol?

 

[Rootus]

In some circles, can you say status symbol?

I wouldn't mind . Yes, I'm a dork. But I think a nice rumbly V8 sounds real good. And if you're next to it right as it blows off 15 psi, that would be double cool. Just a very audible demonstration of what it's like having the best of both worlds...

Dave

 

[SLIGHTLY_INSANE]

sorta like the whine of a supercharger...stupid v2 quiet ones.

 

[Darkness]

I wouldn't mind . Yes, I'm a dork. But I think a nice rumbly V8 sounds real good. And if you're next to it right as it blows off 15 psi, that would be double cool. Just a very audible demonstration of what it's like having the best of both worlds...

Dave

Kinda like doing a couple purges of nitrous huh? I know some one that did it at a stop light next to a cop.

 

[Rootus]

Kinda like doing a couple purges of nitrous huh? I know some one that did it at a stop light next to a cop.

Nitrous is cool, not next to a cop though . Back when I had my '98 Cobra (which was chrome yellow, of course ), there was an issue of MM&FF with a '98 yellow Cobra on the cover purging out through the "nostrils" on the hood... it was vaguely entertaining...

Dave

 

[Visceral]

wait... I dont mean to be crass, but you havent sorted out your current NA combo and you are thinking about adding a turbo setup? That sounds, on first pass, totally insane.

Buy some comp cams 918 springs, some comp cams lifters, and a 224/230 Xtreme Energy on either a 110 or 112 lsa. Put them in. Put an A9L in and get rid of all the tuning for now. Dynotune the crap out of it and then take it to the drag strip with the wideband (I have one if you want to borrow one), and then tune it some more (fuel pressure and spark advance...nothing complicated). Why? SIMPLIFY. You have spent alot of money and now you'd throw more at it before finishing the first? SIMPLIFY. DOnt look at other people's dyno numbers if they dont apply. Scott went 10s, Gregg may soon go 11s... So what? I'd really enjoy sorting out a combo with as many cool parts as you have... so if you want to trade it for a 260 rwhp stock setup with a Cobra intake... I'd be glad to give you some money too

Quit talking about turbos. Very few are plug-n-play, and putting one on an already unsorted combo is asking for trouble. Im with Toddzilla... these things are basically minefields for the average hobbyist. Turbo hardcores can make them seem easy and safe, but for us mortals, they arent.

jmo.

chris

 

[Rootus]

Yes, replacing the cam, lifters, and valve springs, as well as splicing in a new computer, that would definitely be simplifying . Of course, it would also be spending $1000 to downgrade the combo, which is not usually a direction I try to go...

Dave

 

[duner]

I wouldn't mind . Yes, I'm a dork. But I think a nice rumbly V8 sounds real good. And if you're next to it right as it blows off 15 psi, that would be double cool. Just a very audible demonstration of what it's like having the best of both worlds...

Dave

I just found something to help ya out. Since you already have the V8 rumble here's something to help achieve the "double cool" sound you're looking for.

BLOW OFF

 

[Toddzilla]

I do agree that you should maybe try to sort your combo out further.

I don't think that you should go to the A9L as that IS a downgrade. What was your AF last time you were on the dyno?

But your car is running 105 mph, that's not bad at all....and it probably has more in it too.

Are you running on drag radials or street tires?

 

[Rootus]

I do agree that you should maybe try to sort your combo out further.

I'm pretty sure the problem has something to do with how the cam is degreed. There's not a lot of other good explanation for why the torque curve is so skewed to the bottom end.

What was your AF last time you were on the dyno?

14 at 3000 RPM, dropping to mid-13's for most of the run, down to just about 13 flat above 5500. See the dyno graph link in my sig, that was from a few weeks ago.

But your car is running 105 mph, that's not bad at all....and it probably has more in it too.

Are you running on drag radials or street tires?

Peak power ain't great, but the AFR's are making decent power under the curve in any case. I've only run on street tires, spinning through 1st & 2nd. My torque curve combined with 3.73's makes for a very squirrely launch on street tires. With traction I hope to add two or three mph to my traps, and hopefully get this pig solidly into the 12's. And maybe I'll let someone with the skillz (Chris) see what he can get out of it...

Dave

 

[Rootus]

Hey, how about this.

Drop these into my car:
http://www.stangparts.com/products/partpic.cfm?TypeID=5&ID=4013&Page=1&ShowSpecials=FALSE
.. and ..
http://www.stangparts.com/products/partpic.cfm?TypeID=3&ID=3713&Page=5&ShowSpecials=FALSE

And skip the turbo...

 

[duner]

Hey, how about this.

Drop these into my car:
http://www.stangparts.com/products/partpic.cfm?TypeID=5&ID=4013&Page=1&ShowSpecials=FALSE
.. and ..
http://www.stangparts.com/products/partpic.cfm?TypeID=3&ID=3713&Page=5&ShowSpecials=FALSE

And skip the turbo...

Sweet. There ya go.

You didn't like my other suggestion?