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Old 12-03-2003, 04:20 PM   #26
Portly
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To add to that, the real issue is not turbo life.
What we're concerned about here is driveablity and boost spikes.

When you tap into the manifold, you'll get no boost or full boost - it's hard to get anything in between because boost will keep building in the charge pipe until it overwhelms your throttle setting. IowaRS used the term "digital driving" and that's the best description. It's pretty much all or nothing.

The other issue, and the real reason I brought it to IowaRS's attention, was the potential for boost spikes. If you are at part throttle and have 5 psi in the manifold, but 15 psi in the charge pipe, and then you fully open the throttle, you'll get a brief surge of high pressure air before the wastegate can get things regulated down to 5 psi again. It'll be very short, but it's probably gonna be good for a knock or two. So my concern was engine life.
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Old 12-03-2003, 04:37 PM   #27
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Well said portly.

I prefer to have the "digital throttle" that you described because coming out of a tight autocross corner the boost is right there on tap when needed. If you modulate the throttle and don't drive like the pedal has 2 positions, the boost spikes really aren't too much of an issue (really don't ever want to "mash" the gas, if you go from a narrow throttle opening to a wide opening instantly, it causes a ton of turbulence in the intake tract and will cause a small hickup in alot of situations, especially if there is alot of pressure behind the throttle plate). Yes, it all comes together to make the car a tad touchy and it requires a bit more care in driving, but overall the performance, especially coming out of corners is worth it.
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Old 12-03-2003, 04:43 PM   #28
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Quote:
Originally posted by no-coast-punk

No, the BOV needs a vacuum on one side to actuate, the BOV operates entirely independant of pretty much everything else on the car, so a reference between 2 taps is meaningless. But yeah.... keep your wastegate/boost gauge/BOV taps in the manifold because that's where your boost really matters because that is what your motor is seeing, as long as your charge pipe fittings are up to holding the extra boost it shouldn't be a problem. But yeah... it does sound like your BOV is flaking out if you have those kinds of transients being reported for much longer than the time it takes your BOV to vent. I still stand by what I said for why you SHOULD tap your wastegate reference in the manifold after the TB.
Does a bov need a vacuum on one side or a difference in pressure between 2 sides ( bov before throttle plate, vacuum tapped on manifold)? So would this mean the bov will always be venting while the engine is in vacuum (boost < 0)?
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Old 12-03-2003, 04:46 PM   #29
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BOV's are venting under vacuum, if you listen very closely you can hear it, it's just very quiet, and very subdued, and with some models you may not be able to hear it. If BOV's worked on a pressure differential and not vacuum, anything less than ~14lbs of boost (atmospheric) would cause the BOV to vent
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Old 12-03-2003, 05:08 PM   #30
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Quote:
Originally posted by no-coast-punk
Well said portly.

I prefer to have the "digital throttle" that you described because coming out of a tight autocross corner the boost is right there on tap when needed. If you modulate the throttle and don't drive like the pedal has 2 positions, the boost spikes really aren't too much of an issue (really don't ever want to "mash" the gas, if you go from a narrow throttle opening to a wide opening instantly, it causes a ton of turbulence in the intake tract and will cause a small hickup in alot of situations, especially if there is alot of pressure behind the throttle plate). Yes, it all comes together to make the car a tad touchy and it requires a bit more care in driving, but overall the performance, especially coming out of corners is worth it.

Unfortunately I can't DISagree with you more.
I've done a lot of autocrossing with this car.
I drive on the street far faster than I should, always pushing the car. I can go through corners faster now with the gradual throttle instead of on/off throttle.

Ever heard of trail braking?
Heavy braking going into the corner with gradually lighter braking up to the apex.

Well, throttle application works in the reverse.
Small throttle after the apex building up to full-throttle at the end of the corner.

If you can apply full throttle in the middle of the corner you aren't cornering fast enough
In theory at the cornering limit more throttle would just cause the car to slide sideways or spin because the tires are already at their traction limits.
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Old 12-03-2003, 05:25 PM   #31
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I never said the car wasn't touchy, and the throttle can be modulated, but it requires a very light touch and the throttle must be progressively rolled on when coming out of a corner. More difficult to learn to drive... yes, but there is much more power on tap without having to wait for the turbo to catch up. The throttle application you described is how the car has to be driven (combined with some heel/toe action into really wide turns) otherwise the violent power delivery from mashing the gas will put you sidways.
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Old 12-03-2003, 05:49 PM   #32
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Quote:
Originally posted by IowaRS
Ah, this is not true.
I didn't lose enough boost to even read on my gauge.
That's a fact.

There isn't that much loss in the throttle body!!!!!!

Now, pre-intercooler vs. post intercooler is a totally different story.
Exactly. I've never seen an intercooler with a port for a vaccum line on it. I think its a safe bet that 99.9% of people are either using the manifold or the turbo outlet for the wastegate line. When comparing those two (as opposed to your setup, which is very uncommon) there is fairly large difference in pressures.
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Old 12-03-2003, 11:20 PM   #33
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Here's a picture of my wastegate control tapped into the intercooler.

http://us.f1f.yahoofs.com/bc/3fb4fca...qerz_Akhkj_MRU

Hopefully that link works.

And, just because somebody asked, this is where the fitting for the charge pipe is:
http://us.f1f.yahoofs.com/bc/3fb4fca...qerz_AeKgo2YkB


And finally.........the fact is that tapping into the manifold will cause higher boost before the throttle body.
The charge pipe, turbo outlet is probably the best place overall to tap in, considering transients and such.

The whole reason for my posting this discovery is that I don't think people realize what is happening when they tap the wastegate control into the manifold.

Tapping in just before the throttle body is a win-win situation.
You maintain the same boost level as tapping into the manifold, but without the negative effects of boost spikes and ON/OFF throttle.

What you all want to do with this information is up to y'all.
Done, finished. We could debate this ad nauseam.

Last edited by IowaRS; 12-03-2003 at 11:30 PM.
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Old 12-03-2003, 11:39 PM   #34
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Quote:
Originally posted by no-coast-punk
I never said the car wasn't touchy, and the throttle can be modulated, but it requires a very light touch and the throttle must be progressively rolled on when coming out of a corner. More difficult to learn to drive... yes, but there is much more power on tap without having to wait for the turbo to catch up. The throttle application you described is how the car has to be driven (combined with some heel/toe action into really wide turns) otherwise the violent power delivery from mashing the gas will put you sidways.

Much more power on tap?

At partial throttle I have less than 4.5psi in the intake.
That's not as much power as 4.5psi.
Once I go WOT the boost in the intake goes to 4.5psi, max power.
The 4.5psi is available instantly anywhere above 2750rpm because it's knocking at the door of the throttle body, the wastegate is already open by 2750rpm regardless of throttle position.
I get just as quick of response, but without the risk of significant overboost for a brief moment, and a throttle that's much easier to modulate to boot.
Why adapt your driving style around a car that's operating sub-optimally?
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Old 12-03-2003, 11:41 PM   #35
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Neither of the links worked. If you have the time, could you send some pics to [email protected]

I want to try this out, worse comes worse I just plug the hole in the IC, and go back to the manifold. But this sounds like it works pretty decent.

-Kevin
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Old 12-04-2003, 12:03 AM   #36
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Yeah apparently Yahoo! briefcase is no longer free to share pictures with others, bummer.
Attached Images
File Type: jpg wastegate tap highlighted1.jpg (33.7 KB, 92 views)
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Old 12-04-2003, 01:19 AM   #37
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So that is the line that goes to the BOV, right?(just wanna make sure)
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Old 12-04-2003, 09:04 AM   #38
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NO, that's the line that goes to the wastegate control.

The BOV control is tapped into the intake manifold.

You can see the BOV there on the left.

Last edited by IowaRS; 12-04-2003 at 10:48 AM.
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Old 12-04-2003, 04:50 PM   #39
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so you are saying that there will be no change in volumetric efficiency if you change the location of the wastegate tap? i dont see why there would be because what you are saying makes sense, just wondering if it might effect that cause then i would need to retune.

thanks
Ben
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Old 12-04-2003, 05:29 PM   #40
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Where is the wastegate control?
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Old 12-04-2003, 07:02 PM   #41
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its the vacuum line circled in the pic
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Old 12-04-2003, 09:33 PM   #42
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*sigh*, but where does it go to? (where is the wastegate control located?

I have a nipple that goes out of my turbo>boost controller>then to the actuater(do i tap one of those lines?)
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Old 12-04-2003, 10:10 PM   #43
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remove the line from your turbo to the boost controller. connect the new line coming out of the intercooler to the boost controller. use something to plug the line coming out of the turbo.

Be careful with the boost controller settings. You're probably gonna need to lower it a couple psi from where its at now to keep the same level of boost you had in the manifold as before. It won't be seeing the pressure drop from the IC anymore so you need to account for that.
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Old 12-04-2003, 10:38 PM   #44
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FCT - If your wastegate is currently connected near the outlet of the turbo compressor, and you're satisfied with the boost level you get, I wouldn't move it to the far side of the intercooler. IowaRS started this post in regard to people who were connecting their wastegate control line to the intake manifold. A location very close to the turbo outlet is actually the safest spot. IowaRS is connecting his after the intercooler because he'll get an extra (rooughly) 1 psi of boost - that's about how much he was loosing in the intercooler due to pressure drop.

Frankly, if there was such a thing as a 5.5 psi spring for a Tial wastegate, I'm pretty sure IowaRS would be connecting his wastegate control to a spot closer to the turbo. Then he'd see the 4-ish psi at the manifold that he wants. The intercooler location is a compromise, but is (IMHO) a much better location then the intake manifold.

_Jeff
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Old 12-04-2003, 11:14 PM   #45
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I was under the impression that he did this for driveability, not the extra psi. I have plenty of boost and am looking for not on/off throttle.
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Old 12-05-2003, 06:13 PM   #46
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The purpose of the post was to alert everyone to the higher pressure at partial throttle, and indicate that any location pre-throttle body will make the car more driveable than a location after the throttle body.

When I say before and after I'm referencing in the direction to airflow.

That said, the reason I tapped in AFTER the intercooler was boost pressure. If I tap in on the charge pipe I get about 3 psi in the intake.
Tapped in after the intercooler gives me 4psi in the intake.

Portly is 100% right, if they made a 5.5psi spring I would tap into the charge pipe, and the result would be 4-4.5psi in the intake.

In fact I still debate putting my 6.6psi spring in to put the intake at 5-5.5psi, but that takes my fuel pressure up to over 80psi, and I just don't want to do that to stock injectors.
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Old 12-05-2003, 06:17 PM   #47
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Quote:
Originally posted by FatCatTurbo
*sigh*, but where does it go to? (where is the wastegate control located?

I have a nipple that goes out of my turbo>boost controller>then to the actuater(do i tap one of those lines?)
Do you have a line that goes from the intake manifold to the boost controller?
That's the one you want to put in pre-throttle body.
Unless the mfg says to put it elsewhere.
It might be that the EBC wants to see vacuum too.
And the only way to get vacuum is to tap into the intake.

See, I'm talking about a mechanical boost controller (wastegate only). The "wastegate control" as I call it is actually just a vacuum/boost line that now goes from my IC to the bottom part of the wastegate.
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Old 09-13-2019, 09:17 AM   #48
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Default Some bad information here

I know this thread is ancient, but if anyone does come across it, please do not listen to no-coast-punk's advice. Tapping the boost reference line to your wastegate actuator post-throttle body as he advises will isolate it from the actual boost the car is producing, as IowaRS mentioned, causing boost at anything below WOT to differ considerably from what the wastegate actuator is actually seeing. It also removes most ECU control over boost in this region, which is never a good thing.

The right way to get more boost is to adjust wastegate duty cycle and boost tables, either using an accessport or a tactrix cable/romraider. This will allow you to retain much more control over boost and result in much better part-throttle drivability. Doing what no-coast-punk recommends merely forces the car to run part-throttle boost levels that the car is not intended or tuned to. Not only will this result in a touchy pedal that will make it more difficult to approach the limits, due to spiky, high, uncontrolled boost at part throttle, it will not net you any additional power, slight pressure drops being ignored, since pressure equalizes anyway when WOT.
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