ALTITUDE AND BOOST CONTROLLERS DISCUSSION

hook · Nov 15, 2016

I do not have an electronic boost controller. I have a wastegate with a spring pretensioned to open at 6psi. I have boost controller that I used to set my boost at 10 psi. Once I had this set at 10 psi I have not touched the knob. The MAP readings off my vipec logs have stayed at the same reading at all elevations.

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brycter · Nov 15, 2016

hook said:
I do not have an electronic boost controller. I have a wastegate with a spring pretensioned to open at 6psi. I have boost controller that I used to set my boost at 10 psi. Once I had this set at 10 psi I have not touched the knob. The MAP readings off my vipec logs have stayed at the same reading at all elevations.

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When things are done right this is how a fuel controller should work. set it up for what you want and then it is just ride eat sleep repeat!

hook · Nov 15, 2016

I had mountain horse move this so we could get more discussion about this topic. Any more input would be great!

mountainhorse · Nov 15, 2016

Sea Level and turbos, wrapping your head around it.

Heres a post that was put up in another thread.

NWaxys said:
I'd really like to see this out at sea level in Maine or Quebec. That's the turbo run terrible grounds. Not sure they have the perimeters for that as they come.....also clutching included? Or clickers on primary work?

Good topic.

Here is my take, my opinion.

A turbo on a low elevation sled needs to be looked at in a different way.

Since the charge pressure, as MAP, on a sea level sled are already higher from ambient atmospheric pressures.... the change in HP is not as apparent to a flatlander because he has more hp on tap to start with.

Lets say you have an N/A engine that is making 165 hp at low elevations... You put a turbo on it to bump up your HP...
Add say, 6 lbs of MAP to make it 20.7 (1.4 bar) after turbo, ambient 14.7 + 6 = 20.7... You will still be making the same power as that same sled at 10,000 feet that has a MAP of 1.4 bar (+/- a small fraction).

But here is where the Perception plays a roll... The guy that rides at 10,000 feet may have 120 hp on tap on his NA sled because he's removed around 4 psi of atmospheric pressure. That '10,000 foot guy' adds a turbo to the same sled as you have to get that 1.4 bar MAP and VIOLA!!... he now has that 180 + hp that you have on your sled at low elevation (+/-)...but the difference HE feels is 50% more Horsepower.... BIG Difference.

Compare this 50% gain at 10,000 ft to your situation... You have gained 15 hp at the same boost level (1.4 bar)... which is only 11%.... Many would perceive this as 'less bang for the buck'. You don't feel as much of a difference as your buddy on HIS stock machine riding next to you at sea level as the guy who is riding at 10,000 ft next to his buddys same N/A sled.

If you want to pump up the hp beyond "reasonable" MAP pressures... which seems to hover around 1.3-1.5 bar for practical purposes with our 2-stroke sleds and a well designed turbo systems... you are going to have to really push the engine and turbo system.

If you wanted to feel that same 50% kick from your same sea level sled... you are talking about a sled that will have around 250 hp on tap... That sled probably would be running north of 1.8 bar... which will require different fuels, intercooling, bigger injectors etc etc... IMO... you would become a tuning guru by necessity in that scenario.

In short...getting 180-200 hp from a given 2-cylinder 2-stroke is a whole different story than getting 250 hp from the same engine....IMO.

The job of the turbo system here is to provide as CONSISTENT as possible charge-side pressure (MAP) and temperature as possible.
The best turbo systems provide the most consistent MAP/Temps throughout the range of elevations, and rider input for the desired HP level.

Have a look at the helpful chart from gmmustangt below... it may put this into perspective.
Note: I've changed his title of 'Turbo PSI" to "Gauge PSI"

See this thread for a description of what I mean by "gauge psi"
Clickable link
http://www.snowest.com/forum/showthread.php?p=4000543

gmustangt said:
Simply put if you are running "6psi" at sea level. With an altitude compensating feature. Rough numbers:
Typed on my phone .. Hopefully it lines up.

Elevation. / Atmosphere PSI. / Gauge PSI. / PSI Absolute

0ft ...... ...... 14.7 .................. 6 ............ 20.7

1000ft. ...... ...... 14.2 ...... ...... 6.5 ...... ...... 20.7

2000ft. ...... ...... 13.7 ...... ...... 7 ...... ...... 20.7

3000ft. ...... ...... 13.2 ...... ...... 7.5 ............ 20.7

4000ft. ...... ...... 12.7 ....... ...... 8 ...... ...... 20.7

5000ft. ...... ...... 12.2 ...... ...... 8.5 ............ 20.7

6000ft. ...... ...... 11.8 ...... ...... 8.9 ............ 20.7

7000ft. ...... ...... 11.3 ...... ...... 9.4 ............ 20.7

8000ft. ...... ...... 10.9 ...... ...... 9.8 ............ 20.7

9000ft. ...... ...... 10.5 ...... ...... 10.2 ............ 20.7

10000ft. ...... ...... 10.1 ...... ...... 10.6 ............ 20.7

fredw · Nov 16, 2016

Had a buddy that had the bd boost controller on his Poo.. Said it was cats *** but glitchy at times.. But that was a few years back

Only thing I see is if it's keeping constant hp your leaving staging area you could be in Revy as low as 1200' and by riding area over 7000' that is a lot of boost variance the controller will have control.. Wonder how well clutching will handle the same difference because of difference in air pressure.. No one wants a over rev..I see still some fine tuning needed with the controller

But forsure everything that can compensate for altitude and hp changes once figured out makes life just that much eaisier to tune

mountainhorse · Nov 18, 2016

Except for some small differences from other minor factors...

Power levels and clutching should remain consistent if the "EBC" and turbo system is doing its job at maintaining charge side pressures at a consistent level.

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chad006 · Dec 2, 2016

Bringing this back up just because it's been rollin around my head for a while now. But would a wastegate not operate based on psi absolute? So let's say I've set my gate up with a 7lb spring for example which in my mind would actually be a 21.7lb spring at sea level. The air is less dense at altitude thus your charger will have to spin faster to make the same boost, however your wastegate still needs its 7psi or 21.7psi absolute to actuate. I have been doing some data logs on my sled recently and at 2400' 93kpa (13.489psi) barometric pressure. I consistently pull 145kpa with "7lb" spring in actuator. 145kpa=21.03, 21.03-13.489=7.5psi. So in theory a wastegate is essentially a boost controller that adjusts with altitude. I haven't gotten a chance to take any logs at altitude but when I do I will update my findings.

hook · Dec 4, 2016

That's my train of thought too. In my first post I stated that I only have manual wastegate on my turbo. I have it set to build up 10 psi of boost pressure. With the fuel and timing tables in my vipec, I am able to adjust those settings to be able to have my sled run at the same 10 lbs at home in Iowa at 1500 ft and out west in various places ranging from 7500 to 10000 ft with all corrections made off the fuel and ignition tables. No electonic boost controller needed.

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mountainhorse · Dec 6, 2016

Hook,

Can you post up some of your VIPEC logs??... even a photo of your screen(s) would work... It would be great to see that info.

What is your setup?
(What sled, turbo, turbo trim, BOV, wastegate actuator, WG... int or ext, wg spring rating, are you running a mechanical boost controller etc...)

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hook · Dec 6, 2016

These are some logs from before I turned up my boost.

I have a 2012 pro rmk 163 with a turbo performance kit. Garrett 2860 with spring controlled wastegate.

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hook · Dec 6, 2016

The first pic is a run I did at home at 1500 ft. (Note the 96.7 kpa on the BAP) The second pic is a run from up at Togwotee (BAP is 74.7) I wasn't hitting full boost at Togwotee because I had too heavy of weights in, I was only at 7600 rpm. (5.12 psi MAP) At home, I was hitting full boost at 8169 rpm (5.99 psi MAP)

mountainhorse · Dec 6, 2016

Hook,

Is there a BOV?... if so, which one and where?

Where is the sensor located that is reading the Baro pressure?

It would be cool to read some logs of WOT/CHOP/WOT/CHOP.... and check recovery rates of the turbo.

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mountainhorse · Dec 6, 2016

Heres my 2¢... My opinion

With a spring controlled WG, I would think that the WG would stay open more, dumping a little boost at a higher elevation and lower BAP.. there is a larger ∆P across the wastegate which allows the exhaust pressure push against the WG-door/spring with more force.

Rather than looking at your weights as holding back your boost.... I look at it as your slightly lower boost, because of wastegate being open more, holding back your weights... The turbo could not make the full 6lbs at Togwotee because the ∆P across the WG bypassed more exhaust around the turbine.... I doubt your turbo was 'flat-lining' as it can easily make double that boost on an 800 at Togwotee before hitting the choke line.

A fixed spring force acting against the WG is able hold the WG closed less as Baro drops.
Another way to look at this is that a given pipe pressure will open the WG more as BAP drops (increase in elevation)

This is where a self compensating EBC will have better altitude compensation as it regulates MAP regardless of ∆P-baro.... within the confines of the turbos capabilities of course... and the 2860 certainly is working within it's capabilities in your situation and pressure levels.

Just my opinion.... I'm sure Bryce could add more to this.

Glossary..
MAP -- Manifold Abslolute Pressure (PSIa/ kPa etc)

BAP -- Barometric Absolute Pressure (PSIa/ kPa etc) (AKA 'Baro')

MGP -- Manifold Gauge Pressure

WG -- Waste Gate

∆P -- Delta P -- differential pressure -- pressure on one side compared to the other.... eg a WG, turbine in/out or a compressor in/out

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mountainhorse · Dec 6, 2016

Bryce,

Since hooks system has a VIPEC unit on it... can't it control a solenoid & WG actuator to maintain a target MAP rather than the spring setup?

If so, what are the challenges in configuration of the VIPEC to do this?

.

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mountainhorse · Dec 6, 2016

chad006 said:
Bringing this back up just because it's been rollin around my head for a while now. But would a wastegate not operate based on psi absolute? So let's say I've set my gate up with a 7lb spring for example which in my mind would actually be a 21.7lb spring at sea level. The air is less dense at altitude thus your charger will have to spin faster to make the same boost, however your wastegate still needs its 7psi or 21.7psi absolute to actuate. I have been doing some data logs on my sled recently and at 2400' 93kpa (13.489psi) barometric pressure. I consistently pull 145kpa with "7lb" spring in actuator. 145kpa=21.03, 21.03-13.489=7.5psi. So in theory a wastegate is essentially a boost controller that adjusts with altitude. I haven't gotten a chance to take any logs at altitude but when I do I will update my findings.

When you are talking about the "spring" .... are you talking about a Waste Gate Actuator with a '7 lb' spring inside of it... or a spring that replaces the actuator? ie Does your system have an actuator, or a spring alone?

Yes, the wastegate does control boost...The actuator or stand alone spring that pulls the WG door closed is what adjusts to a large degree for altitude.

BAP changes this as described above.

AND... a boost controller device that you plumb between your boost reference point and the wastegate actuator.. it is a threshold device that does not open the wastegate till a set MAP pressure is met... at that point... the controller opens it's valve and permits the boost pressure to push on the actuator, opening the WG.

Without a boost control device, a typical WG will begin to bleed off some exhaust as the target pressure is met... the WG BEGINS to open at the target boost level...which can make the throttle response less crisp

Here is a helpful description that has weight here.

Wastegate spring pressure is the highest boost level you can reach.

False. Wastegate spring pressure is the lowest boost level you can reach. You can easily increase boost pressure over wastegate spring pressure by using a boost controller, but you can’t achieve a maximum boost level under the wastegate’s spring pressure.

If a wastegate is fitted with springs rated to 7PSI, it will open when it receives 7PSI of pressure to the actuator. Any pressure lower than that will not be able to overcome the spring force, and it will remain closed.

http://www.turbosmart.com.au/news/five-facts-about-wastegates-that-are-wrong

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chad006 · Dec 6, 2016

I am running an aero kit with a different fuel controller, I was using the wastegate as an example. With vanes I don't think the baro is going to affect the vanes much if at all. Is drive pressure really going to change that much with a drop in baro you still need a certain drive pressure to make a certain boost? I would assume that drive pressures are around the 1:1 or 1.5:1 per pound of boost (correct me if I'm wrong) so for 7lbs of boost your most likely to have around 10lbs drive pressure. I do believe that I will see a small loss of boost PSIA as you drop baro as obviously ambient air temp and humidity, charge temps will take their toll at altitude as well. However I don't believe that it is enough to require any boost compensation. With a properly setup system I just haven't seen the need for it. Now take this all with a grain of salt guys I'm just a farmer.

mountainhorse · Dec 6, 2016

Your are right... ride em and have fun.

A lot of the control is not what boost numbers you can hit or keep...but HOW does the turbo sled run.... what kind of throttle response and is it consistent at all the altitudes you will ride (not ALL altitudes)... how is lag and recovery?

How it runs is as (or more) important to me as max power... In fact... Max power is less important...

For a sled that normally has about 110-120 hp at 10k feet... what a hoot is it when you add 50% more hp (60 hp) at that elevation... HUGE... Sure, 200+ hp is fun, but what are the tradeoffs in reliability or need to tune and how to get consistency... without the need to be 'tinkering", adding race fuels or wearing out parts faster.

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chad006 · Dec 7, 2016

Honestly throttle response with the aero is very very crisp, especially with the controller I am running. I can adjust my vanes to build drive pressure very early in the curve. The charger definitely has its drawbacks though the major one is charger replacement/maintenance. Kinda nice to be able to swing down to the local turbo distributor and pick up a center section. However it works well and is a dream to ride now with the system I'm running. Fuel delivery is a huge factor in how these turbo etecs perform I have found. Most of the kits now days are very similar in specs, the major difference being fueling and charge temp management.

hook · Dec 7, 2016

My sled at togwotee did not build the six pounds because of the heavy weights not letting my sled wind up to 8200 rpm not because of the wastegate. It is spring operate not held in place by atmosphere pressure. Since the motor was lugging down, the exhaust wasn't flowing into the turbo fast enough to spin it hard enough to build up the boost.

My question I am wondering is if the ebc is such an effective way to control your power, why is turbo performance, silber, impulse, mountain tech, and other turbo builders utilizing a manual type of wastegate instead of an ebc.

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mountainhorse · Dec 7, 2016

Heres my opinion...

My point is that your 2860 has plenty of capacity to make 20.7 PSIa MAP (142 kPa) target ("6 lbs boost) at Togwotee... even with the 74 gram weights.

With no servo-actuator, as I believe you are describing... and just a simple spring, the dynamics of the WG operation are different at differing ambient pressures.

If it is not making the target "6 lbs" ... It must be bleeding off exhaust through the wastegate. And actually, a turbine will spin faster because of the larger ∆P from the stinger vs. the exhaust exit at higher elevations (lower ambient baro).... but not enough to also overcome the increased bleed off past the WG.

The lower ambient pressure at Togwotee is 'helping' the WG spring keep the WG-door closed less than at low elevation ... it will open at a lower pipe pressure at altitude than at lower elevation and the result is making less MAP, resulting in less power, resulting in lower RPM.

Even if you ran lighter weights at Togwotee, your engine would indeed spin faster (AKA 'wind up") but the turbo would not be making more pressure.

Try this simple test: Increase the spring pre-load on the WG-spring when you are at altitude, leaving the weights the same, and tell me if you make, and maintain, your target 20.7 MAP (142 kPa) and pull the 74's at 8200..... or rather the same 138 kPa (20.02 PSIa) you are getting at 1500 ft.

I don't believe that at that low of boost target, "6 lbs", that charge temps will rise enough to make a noticeable difference in charge density.

Although this photo below is a MTNTK EFR turbo... (I'm ONLY showing this for illustration purposes). I understand you have a Garrett turbo and this is an EFR....
From your description, I am assuming that you have a spring ONLY, and NOT an actuator with a spring inside of it, on your Waste-Gate.... similar to the one shown in this photo. If you DO actually have an actuator and a manual boost controller... then the discussion changes.

Does your Kit run a BOV??

ALTITUDE AND BOOST CONTROLLERS DISCUSSION

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