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Heard of a Part Throttle Wastegate?

I read about a PTO wastegate. It is the same as a normal one but also opens up at vacum and part throttle... so the turbo doesnt spoil up when not needed.

The acutator had two springs in it to get this to work on vac and on the max boost pressure set . Some guy called Stanely Updike invented it.

Any clues if they make this?
Any disagreement on not having the wastgeate open at idle/vac?
I guess an electronic boost controller could do this?

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Old 12-06-2006, 02:29 PM
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This would have the same effect as running a very low base boost spring in your wastegate and regulating the upper boost limit using a highly configurable boost controller, such as the Apexi AVC-R. You could turn off the EBC when you don't wany any boost and rely on the base boost spring. Then you can have a number of preset boost settings for, say, medium boost and one for high boost.
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Old 12-06-2006, 02:46 PM
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Miles, I don't think I can answer your questions, but...

I'm interested in the concept of limiting boost at part throttle. For a road racing application, it's not advantageous to have full boost at part throttle, though that's exactly what happens. It can be disconcerting and dangerous to have too much power too soon. That nonlinear "rubber band" feel is what makes turbocharged cars so spooky to drive, especially when exiting a corner. The last thing you want as you round the apex and slowly advance the throttle is a disproportionate change of torque to the rear wheels. I think it would be ideal to have (say) half the torque available at half throttle and full torque at full throttle (but not before).

We tried doing this during the tuning of my EFI engine. Considerable time was spent mapping the boost controller versus TPS. The boost control solenoid is a VW turbo part and it's controlled by my DTA ECU. What we found was that we were able to limit boost a bit (about 10% less torque at part throttle) from our efforts, but nowhere near enough to give the car a truly linear feel. There just wasn't enough range of controllability with that system (for that particular solenoid, Garrett turbo, and Tial wastegate) to get it where I wanted it.

For one of my 0.9 bar maps, with a TPS-based boost reduction scheme, at 5250 RPM we saw 496 ft-lb at 100% throttle, 478@85%, 464@76% and 448@66%, 451@57%, and 437@47%. So, that's about 10% less torque at 50% throttle. Not much, but it's something. To really interpret how much of this was due to TPS-based reduction, and how much was just because the throttle wasn't open all the way, would require more data, but I'm sure we made a difference with this tuning technique.
Old 12-06-2006, 04:49 PM
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Quote:
Originally posted by Rob 930
The boost control solenoid is a VW turbo part and it's controlled by my DTA ECU.
The N-75 has a few variants that define the responsiveness of the solenoid to the voltage signal. N-75C, N-75F, N-75H and so on. Slow response variants cause higher boost spikes at partial throttle. Faster response will be lower and smoother at PT.
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Old 12-07-2006, 09:21 AM
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A wastegate being opened partially at low throttle openings is certainly a concept I've never heard of, but then I don't get out much.

The compressor side of a turbo becomes an inlet restriction if the impeller is not turning. Modern efficient impellers with swept blade tips need shaft power to move air through them.

Strange concept about the wastegate, but I suppose there may be some hi-tech tuning like this that results in certain performance gains.
Old 12-07-2006, 05:35 PM
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I think the main point is for example when you are crusing on the highway at 70 but sometimes you will get some small boost when you dont really need it.
Old 12-09-2006, 09:54 AM
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"The N-75 has a few variants that define the responsiveness of the solenoid to the voltage signal. N-75C, N-75F, N-75H and so on. Slow response variants cause higher boost spikes at partial throttle. Faster response will be lower and smoother at PT."

Tsuter,

I'm not sure which variant I have. But my concern was not about boost spikes or transients related to the solenoid valve, it's about steady state boost level. I don't recall seeing any boost spikes from the valve, and even if they were there, they would have been short lived. What I was trying to do was restrict steady state boost so that I had much less than full boost when I was much less than full throttle. I don't know why I (or anyone) would ever want full boost at anything less than full throttle. But I definitely get full boost way before full throttle. Or at least, I get way more boost than I want or can use. Accurate control of the wastegate -- and ultimately boost level -- (especially with a big turbo like mine) may not be easy to do with any type of available hardware or tuning regimen. If anyone has any ideas, I'm very open to hearing them.


Rob
Old 12-09-2006, 02:26 PM
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You could go to a two position boost switch with the lower setting at about .3 or .4 bar and the other position at your full determined boost. With a shift or wheel mounted button switch it would be easy to select which ever boost you wanted. Ie; coming out of a turn select the lower boost and then when you get everything squared away, select the full bost. A computer would do it more consistently but what would you use for parameters? Only you know when and how much you need.
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Old 12-09-2006, 07:12 PM
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This has been done. I remember people on Rennlist talking about it. I think the guy that helped "Sandman" with his rebuild has done it for a Rennlister. I think that was the guy that recommended "Sandman" go to him. It may have been Neil of Performance developments who done it and the customer might have been "M42racer".

I'm sure Sandman will help you out here if I am right or wrong.
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Old 12-10-2006, 08:59 AM
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Are there wastegates available that are, essentially, servo valves? Something similar to what's used in hydraulic applications? Then it could be mapped to a fine gradient with the ECU, instead of some sort of two-stage setup.

rob
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Old 12-10-2006, 10:03 AM
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Rudy,

The driver-selected boost you describe is sort of what I'm talking about, though it would really be a crude solution to have to push a button to raise the boost. I'm looking for a "smarter" automated system, based on thottle position, that limits boost below full throttle. Funny, I guess what I'm really looking for is a normally aspirated engine! Or at least, I want to see how closely I can simulate the linear throttle characteristics of an N/A engine, while still having the huge torque benefit of a turbo engine.

Nathan,

Thanks. I can check with Neil or M42 Racer to see if they've come up with anything like this. I've been following the Rennlist board for years and I've never seen a discussion about this topic. I'll look again, and/or I'll check with Neil.

I would think that if this kind throttle-position-based torque control could be exerted over a turbo system, then everyone would want to have it. My guess is that it can't be practically accomplished with a traditional turbo/wastegate/controller system or it would have been done long ago.
Old 12-10-2006, 10:17 AM
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As said, couldnt you just have a very light spring and a solendoid boost controller that just goes by TPS.

BTW Has anyone heard of a BOV that can open under boost and be vac operated???
Old 12-11-2006, 11:14 AM
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In Megasquirt looks like the case

http://www.msextra.com/manuals/MS_Extra_Hardware_Manual.htm#boost
Old 12-11-2006, 11:33 AM
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Rooked 930 and Miles,

I don't know about servo-valve wastegates, or if there are any such things. If there were, it might be interesting. But I have a light spring with and ECU-controlled solenoid valve. And for whatever reason, the system (ECU/turbo/wastgate/solenoid valve) can't be controlled to the level I'd like. I didn't study the Megasquirt system, but it looks similar to the DTA system, which is what I was using. Below is a screen print of the DTA window with my settings. Though it made a small difference in the correct direction, it didn't have nearly enough control range to reduce boost as much as I wanted. As I said earlier, it may have reduced engine torque by a few percent (up to 10%).

Old 12-11-2006, 12:53 PM
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