Interesting Wastegate (non-Honda)
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From: Orlando, UCF, FL, Broward
Interesting Wastegate (non-Honda)
Sorry if this is a repost And also, no link. Got this from another forum, Carand driver.com forum to be exact. Thought it was kind of cool what BMW did with the wastegate(s).
The Shiv Vishnu known for tuning insanely fast EVO MR recently received a BMW 335i TT. He dyno tested and wrote his thoughts on the topic. I thought I would share it with fellow H-T members.
Here are direct quotes:
"Dyno'd our new 335i today. The dyno actually reads a bit low for a dynojet. Other dynojets in the area usually read 8-12whp higher. Regardless, the results were better than expected. Yes, the car is grossly under-rated from the factory.
All results were taken in 4th gear, btw. A 3rd gear pull made a few more ponies but the run was very short.
Best Regards,
Shiv
Vishnu Performance Systems"
Later on he also added the following in another statement.
"The stock turbos do seem capable of holding more boost at redline. In stock form, boost peaks at 9ps but falls down to 5psi up top and then again to 0psi at redline. This is one of the things I'm playing around with right now.
For more info on how the boost controls stem works, here's a post i made the other day...
I've been playing around with our new 335i and found a few interesting bits. One thing I noticed, after much datalogging, probing and head-scratching is its boost control system. It's pretty unique. I haven't seen anything like this employed before in any turbo application, twin turbo or otherwise.
Unlike other turbo systems (evo included) which have a positive mechanical wastegate pressure (that keeps the wastegate normally shut); the wastegates on the turbo are designed to remain fully extended in its natural state. This means if you disconnected all forms of boost control, the 335i runs 0psi of boost. On the other hand, if you do this to an EVO, it will run 11psi of boost. To get more boost in the EVO, the factory boost control solenoid bleeds off the wastegate pressure so the wastegate stays more shut. If the wastegate signal hose, for some reason, were to pop off or rupture, the wastegate would get no boost signal, and you'd get an engine-grenading overboost condition.
With the BMW, to get more boost, it regulates a *VACUUM* signal to pull *CLOSE* the naturally open wastegate. During normal off-boost driving, the wastegate is fed 10" of vacuum which keeps the wastegate partially open. During WOT, but before full boost is reached, the wastegate is fed 20" of vacuum, which completely closes the wastegates for maximum boost response. Once full boost is reached, the wastegate sees 3-5" of vacuum used to regulate the wastegate opening for sustaining the desired boost. Once fuel cut is reached, the clever folks at BMW decided that boost needs to go to 0psi so as to not result in a big, uncivilized "bang bang bang" against the rev limiter. To do this, it cuts all vacuum to the wastegates and they go fully open (no boost!).
The upside to this approach, as i see it at least, is as follows:
1) During start-up, the wastegates are open and the turbos are effectively bypassed. This means that much of the hot exhaust coming out of the engine doesn't go through the turbine wheel and cool off. Instead, it goes right out the wastegate and right into the catalyst. This gets them up to temp quicker and makes the boys at the EPA happy. This also means that BMW can push the cats back downstream a little bit instead of cramming them right up against the turbo where backpressure effects are most deleterious.
2) There is no way to induce an overboost since the natural state of the wastegate is fully open. In other turbo cars, something as simple as a wastegate line rupture will cause the car to overboost.
3) Its just cool engineering. Leave it to the Germans.
The downside to this approach, as i see it at least, is as follows:
1) It requires the use of a separate vacuum tank that needs to be smuggled under the hood somewhere. This takes up a little bit of space and costs extra money. Not much but we all know how OEMs like to shave off every extra bit of material and cost.
2) It confused me for a good part of the morning."
The Shiv Vishnu known for tuning insanely fast EVO MR recently received a BMW 335i TT. He dyno tested and wrote his thoughts on the topic. I thought I would share it with fellow H-T members.
Here are direct quotes:
"Dyno'd our new 335i today. The dyno actually reads a bit low for a dynojet. Other dynojets in the area usually read 8-12whp higher. Regardless, the results were better than expected. Yes, the car is grossly under-rated from the factory.
All results were taken in 4th gear, btw. A 3rd gear pull made a few more ponies but the run was very short.
Best Regards,
Shiv
Vishnu Performance Systems"
Later on he also added the following in another statement.
"The stock turbos do seem capable of holding more boost at redline. In stock form, boost peaks at 9ps but falls down to 5psi up top and then again to 0psi at redline. This is one of the things I'm playing around with right now.
For more info on how the boost controls stem works, here's a post i made the other day...
I've been playing around with our new 335i and found a few interesting bits. One thing I noticed, after much datalogging, probing and head-scratching is its boost control system. It's pretty unique. I haven't seen anything like this employed before in any turbo application, twin turbo or otherwise.
Unlike other turbo systems (evo included) which have a positive mechanical wastegate pressure (that keeps the wastegate normally shut); the wastegates on the turbo are designed to remain fully extended in its natural state. This means if you disconnected all forms of boost control, the 335i runs 0psi of boost. On the other hand, if you do this to an EVO, it will run 11psi of boost. To get more boost in the EVO, the factory boost control solenoid bleeds off the wastegate pressure so the wastegate stays more shut. If the wastegate signal hose, for some reason, were to pop off or rupture, the wastegate would get no boost signal, and you'd get an engine-grenading overboost condition.
With the BMW, to get more boost, it regulates a *VACUUM* signal to pull *CLOSE* the naturally open wastegate. During normal off-boost driving, the wastegate is fed 10" of vacuum which keeps the wastegate partially open. During WOT, but before full boost is reached, the wastegate is fed 20" of vacuum, which completely closes the wastegates for maximum boost response. Once full boost is reached, the wastegate sees 3-5" of vacuum used to regulate the wastegate opening for sustaining the desired boost. Once fuel cut is reached, the clever folks at BMW decided that boost needs to go to 0psi so as to not result in a big, uncivilized "bang bang bang" against the rev limiter. To do this, it cuts all vacuum to the wastegates and they go fully open (no boost!).
The upside to this approach, as i see it at least, is as follows:
1) During start-up, the wastegates are open and the turbos are effectively bypassed. This means that much of the hot exhaust coming out of the engine doesn't go through the turbine wheel and cool off. Instead, it goes right out the wastegate and right into the catalyst. This gets them up to temp quicker and makes the boys at the EPA happy. This also means that BMW can push the cats back downstream a little bit instead of cramming them right up against the turbo where backpressure effects are most deleterious.
2) There is no way to induce an overboost since the natural state of the wastegate is fully open. In other turbo cars, something as simple as a wastegate line rupture will cause the car to overboost.
3) Its just cool engineering. Leave it to the Germans.
The downside to this approach, as i see it at least, is as follows:
1) It requires the use of a separate vacuum tank that needs to be smuggled under the hood somewhere. This takes up a little bit of space and costs extra money. Not much but we all know how OEMs like to shave off every extra bit of material and cost.
2) It confused me for a good part of the morning."
Honda-Tech Member
Joined: Sep 2003
Posts: 707
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From: NY
Re: Interesting Wastegate (Mach69)
That's a nice powerband for a fun daily driver around town.......pretty much peak torque at 2,000rpm and holding it decently well till 6k then its probably dying due to no boost at redline. Would probably be awesome with some aftermarket boost control, wonder how it would work with that setup.
The wastegating is pretty cool, nice insurance against possibility of engine damage due to overboosting......I wonder if conventional wastegates can be setup to function like that.
The wastegating is pretty cool, nice insurance against possibility of engine damage due to overboosting......I wonder if conventional wastegates can be setup to function like that.
Honda-Tech Member
Joined: Apr 2001
Posts: 16,905
Likes: 3
From: Lansdale, PA
Re: Interesting Wastegate (LeGeND4LiFe)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mach693 »</TD></TR><TR><TD CLASS="quote"> Its just cool engineering. Leave it to the Germans.
</TD></TR></TABLE>
F them. worst pos cars ever FT MF-ing LOSE
</TD></TR></TABLE>
F them. worst pos cars ever FT MF-ing LOSE
Honda-Tech Member
Joined: May 2003
Posts: 5,735
Likes: 0
From: Portland, Oregon
Re: Interesting Wastegate (dturbocivic)
Is that really how the AF ratio looks stock?
Doesn't that seem really lean? I suppose I don't spend much time looking at stock boosted cars' AF ratios. But geeze, if that were a Honda plot I wouldn't give it much time.
Doesn't that seem really lean? I suppose I don't spend much time looking at stock boosted cars' AF ratios. But geeze, if that were a Honda plot I wouldn't give it much time.
Member
Joined: Dec 2002
Posts: 1,740
Likes: 2
From: Tampa, Fl, US
Re: Interesting Wastegate (EJ1 wilcox)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EJ1 wilcox »</TD></TR><TR><TD CLASS="quote">Is that really how the AF ratio looks stock?
Doesn't that seem really lean? I suppose I don't spend much time looking at stock boosted cars' AF ratios. But geeze, if that were a Honda plot I wouldn't give it much time. </TD></TR></TABLE>
im guessing it has something to do with the type of direct fuel injection it uses
Doesn't that seem really lean? I suppose I don't spend much time looking at stock boosted cars' AF ratios. But geeze, if that were a Honda plot I wouldn't give it much time.
</TD></TR></TABLE>im guessing it has something to do with the type of direct fuel injection it uses
Honda-Tech Member
Joined: Sep 2001
Posts: 12,978
Likes: 1
From: Reading, PA, usa
Re: Interesting Wastegate (dturbocivic)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dturbocivic »</TD></TR><TR><TD CLASS="quote">
F them. worst pos cars ever FT MF-ing LOSE</TD></TR></TABLE>
Dont hate man. I agree they are a little over complicated though.
I read this same thing on Bimmerforums like 2 weeks ago.
Deffinately interesting.
F them. worst pos cars ever FT MF-ing LOSE
</TD></TR></TABLE>Dont hate man. I agree they are a little over complicated though.
I read this same thing on Bimmerforums like 2 weeks ago.
Deffinately interesting.
Honda-Tech Member
Joined: May 2003
Posts: 5,735
Likes: 0
From: Portland, Oregon
Re: Interesting Wastegate (PM-Performance)
Sounds like it's going to be hard to increase the boost with this setup. I can understand why they did it this way, I suppose....
Is it often that stock turbo motors overboost and grenade? I have never heard of this happening before. Couldn't they just have integrated a boost cut into the EMS that would have solved the same problem for cheaper?
I suppose a boost cut wouldn't address the wastegate being open at idle and startup to warm the cats...
Hmm... interesting stuff.
Is it often that stock turbo motors overboost and grenade? I have never heard of this happening before. Couldn't they just have integrated a boost cut into the EMS that would have solved the same problem for cheaper?
I suppose a boost cut wouldn't address the wastegate being open at idle and startup to warm the cats...
Hmm... interesting stuff.
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