{"id":20749,"date":"2024-09-30T16:50:19","date_gmt":"2024-09-30T20:50:19","guid":{"rendered":"https:\/\/maxtorqueperformance.com\/staging\/?p=20749"},"modified":"2024-09-30T17:08:05","modified_gmt":"2024-09-30T21:08:05","slug":"wastegating-101-how-does-a-wastegate-work-and-do-you-need-one","status":"publish","type":"post","link":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/2024\/09\/30\/wastegating-101-how-does-a-wastegate-work-and-do-you-need-one\/","title":{"rendered":"Wastegating 101: How Does A Wastegate Work, And Do You Need One?"},"content":{"rendered":"
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By\u00a0<\/span>Jason Sands<\/a><\/span><\/span>\u00a0<\/span>April 09, 2021<\/span><\/div>\n


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It\u2019s wrong to say that a diesel engine absolutely needs a turbocharger, but boy do they help. Naturally aspirated, a 7.0-liter diesel (basically the size of a new pickup engine) might only make a little over 100 horsepower, so it\u2019s clear that boost is much-needed. That\u2019s why virtually all modern diesel engines are turbocharged, so much so that the term turbodiesel is actually recognized as one word.<\/p>\n

In the early years (think 1989 Dodge Ram with a Cummins<\/a>), turbo systems were fairly simple. A turbo was hung off the exhaust manifold and was spun by exhaust pressure in order to feed air into the engine. That was it. No wastegate, no intercooler, no variable geometry\u2013nothin\u2019. As technology progressed, however, all of these things were added, as all of them are beneficial to the turbodiesel engine. One of the very first items that made its way into turbodiesels was the wastegate. But what exactly does a wastegate do?<\/p>\n

The most popular wastegate design for turbocharged diesels is the internal wastegate. It\u2019s called this because the wastegate is incorporated into the turbine housing, and is used to bypass the turbine through a small hole right before the downpipe.<\/p>\n

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The Advantages of Running a Wastegate<\/strong><\/p>\n

Turbochargers spin at a very high rate of speed\u2013up to 100,000 rpm in some cases\u2013in order to windmill air into an engine at pressures that are much higher than atmospheric. A modern OEM turbo may run at 30 psi or more, while competition versions can run upwards of 70, 80, or even 100psi. In the end, though, every turbo has its limit. Over-pressurizing or over-speeding a turbo can result in catastrophic failure and that will ruin a turbo. Possibly even damage the engine.<\/p>\n

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Simply put, a wastegate bleeds off the exhaust pressure that drives the turbocharger. This in term limits the amount of boost the turbocharger creates, and also the maximum compressor speed. Score one for the turbo that was just saved. There\u2019s more, however, as turbo sizing can also be adjusted, which means a smaller, quicker spooling exhaust side can be fitted for low-rpm response, and then pressure can be bled off up top in the rpm range. This is the main reason that Ram, Ford, and GM all went with wastegate setups; it protected the engine from damage and gave a more usable and extended rpm range.<\/p>\n

\"wastegate\"<\/a> <\/p>\n

Sled pullers don\u2019t normally run a wastegate because they need every last pound of boost the turbo can create in order to make maximum horsepower. The large safety blankets are installed to prevent shrapnel in case the turbo explodes.<\/p>\n<\/p><\/div>\n

When Don\u2019t You Need A Wastegate?<\/strong><\/p>\n

If there are times that you need a wastegate, surely there are times when the opposite is true, and you don\u2019t need one. Many competition vehicles that aren\u2019t using nitrous oxide injection (we\u2019ll get into that later) will run non-wastegate turbochargers, as they\u2019re looking for literally the most boost pressure the turbo can produce, and are also not too concerned with elevation changes or drivability.<\/p>\n

Other applications that run at a fairly specific rpm like tractors or generators can also get away without running a wastegate, mainly for cost reasons. But for the diesel performance industry, wastegates are beneficial.<\/p>\n

\"wastegate\"<\/a> <\/p>\n

Exploded diagram of a wastegate. Photo courtesy Precision Turbo and Engine<\/p>\n<\/p><\/div>\n

How a Wastegate Works<\/strong><\/p>\n

A wastegate is a fairly simple system. Most mechanical wastegates use a simple diaphragm with a spring inside that opens at a preset pressure. This pressure can be changed anywhere from 5psi to 50psi (or more) depending on the spring setups and boost referencing available. This assembly in turn actuates a valve, that opens towards the atmosphere, venting excess pressure.<\/p>\n

This type of wastegate is simple and effective and can be used outside the turbocharger (an external wastegate) or integrated into the turbo (internal wastegate). Variable geometry turbos can also create a wastegate effect through a nozzle or vanes, but since they are complex and computer-controlled, we\u2019ll stick mainly to valved gates.<\/p>\n

\"wastegate\"<\/a> <\/p>\n

In addition to wastegate springs, boost can be regulated to the top and bottom ports to control when and if the wastegate opens. This way the wastegate can almost be infinitely adjusted, down to 1psi increments.<\/p>\n<\/p><\/div>\n

Wastegate Tuning<\/strong><\/p>\n

At first, this may sound counter-intuitive, after all the wastegate is the control right? Technically, yes that\u2019s correct, but there\u2019s still a lot of \u201cdialing in\u201d that has to occur. A good starter spring for a wastegate is somewhere around a 15-pound spring. This means that once the turbocharger reaches 15psi, a boost line to the bottom of the diaphragm will open the wastegate and relieve some back pressure.<\/p>\n

On a diesel, however, you may want a lot more boost, something along the order of 40 to 70 psi for most trucks, so, therefore, regulated air must be run to the top of the diaphragm to keep it shut. Adding a regulated 30-psi to the top of the gate now means that the turbo won\u2019t overcome the spring pressure (and boost on top of it) until about 45 psi. Adding full boost to the top of the gate will effectively keep the wastegate shut; eliminating it completely.<\/p>\n

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Case Studies<\/strong><\/p>\n

Sometimes it\u2019s best to have a few examples in order to get the hang of how something works. Here we have a couple of street trucks, a drag truck, and a sled-pulling rig all to show how a wastegate is used (or not used) on each setup.<\/p>\n

Truck number one is a street truck. It is a 1996 Dodge Ram with minor fueling upgrades and 57mm\/71mm\u00a0<\/span>ATS<\/a>\u00a0<\/span>compound turbos with a single internal wastegate.<\/p>\n

We had the pleasure of tuning this truck on the dyno with pressure monitors everywhere, so we could report how much power it made under various configurations. Before we hit the dyno, we ran it on the street where it only made 57psi with its limited fueling. That seemed low so we pinched off the wastegate line, effectively closing it. Boost hit 65psi, but the truck didn\u2019t feel any faster.<\/p>\n

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How much back pressure can a diesel create you ask? Well, if the giant flame out of Cole Dow\u2019s race truck is any indication, a lot. Heavy nitrous use is one application where an external wastegate is almost mandatory.<\/p>\n<\/p><\/div>\n

The dyno would tell the story. After our first run, the truck made 400rwhp at 65psi, but with a whopping 99psi of backpressure (or drive pressure) which was far and away from the magical 1:1 boost to drive pressure that most folks aim for. Opening the wastegate saw a drop in boost of 8psi to 57psi, but drive pressure was a mild 64psi, and the truck actually picked up in power to 432rwhp! In this case, proper wastegating netted an increase in power even at a lower boost level, due to an increase in engine efficiency.<\/p>\n

Truck number two is a drag truck. It is a 2003 GMC 2500 with heavy fueling upgrades and tuning, a stock turbo with an internal wastegate, and a lot of nitrous.<\/p>\n

After this truck ran 6.60s in the eighth mile we had to adjust our glasses, because there was no way it should have been that fast on the factory turbocharger. The racer had initially been running the turbo in the danger zone at nearly 40psi, but he found that by putting a larger diaphragm actuator (Banks Big Head<\/a>) he could lower the boost to 30psi and just add more nitrous and run even faster! This was a case where the wastegate was being used to just keep the turbocharger alive with nitrous, since adding N2O to the mix dramatically increases drive pressure.<\/p>\n

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Truck number three is a 1999 Dodge Ram sled puller. This truck features heavy fueling upgrades and a 3.0-inch turbo with no wastegate.<\/p>\n

Sled-pulling trucks are great examples of diesels that may be run without a wastegate, even though they make extreme amounts of boost and horsepower. Since these engines operate at an extremely high (4,000 to 6,000rpm) rev range and go down track at a fairly constant rpm (say 4,500 to 5,500rpm) they don\u2019t necessarily need a wastegate.<\/p>\n

Instead, the boost is controlled by very large exhaust sides and effective intercooling on the intake side. If the turbo explodes because of excess speed or pressure, a \u201cbetter turbo\u201d is simply found instead of a wastegate. It\u2019s for this reason the best turbos for pulling can cost $5,000 or more, and while you could drive this type of setup on the street, it would be downright miserable. There have also been claims (mostly on tractors) of 100psi or more from a single turbo, which is downright insane.<\/p>\n

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The piping for turbo systems can get pretty complex on V-shaped engines, especially when compound or triple turbos are involved. Still, it\u2019s almost always beneficial to run a wastegate.<\/p>\n<\/p><\/div>\n

Truck number four is another street tuck. This 2008 Ford F-250 utilizes heavy fueling upgrades, a\u00a0<\/span>Compound Turbo system<\/a>\u00a0<\/span>with a VGT high-pressure turbo, and twin external wastegates.<\/p>\n

The turbo setup on 6.4-liter Fords is a factory compound setup<\/a>\u00a0<\/span>that includes a variable geometry high-pressure turbo. So right from the factory, they\u2019re fairly complicated. This particular truck has probably the most extensive wastegate-tuning time on the dyno we\u2019ve ever heard of, and took nearly 100 hours of fuel, timing, and tweaking to dial in.<\/p>\n

After some initial runs, the truck made 730rwhp, but the tuner decided there had to be more in the combination because the 82mm turbo made enough air to flow more than 1,000rwhp. So the tweaking began. As the boost began to rise, the backpressure climbed fast, and at a little over 40 psi, the truck had a backpressure reading of more than 80psi. The trend continued until the sensor peaked at 85psi.<\/p>\n

True backpressure was over 100psi. So, the decision was made to incorporate two external wastegates (one per bank since it was a V8) and dial it into work with the factory VGT curve. After a bunch of tweaking, the truck arrived at 67psi of boost with 84psi of backpressure, and 908 hp. It was also dead reliable and driveable, although the quick-spooling turbos ate transmissions after a few dynos run with more than 1,800 lb-ft of torque. Again some changes were made and the wastegates and VGT were used to limit power down low to 1,600 lb-ft, and the truck lived a long and happy life.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

By\u00a0Jason Sands\u00a0April 09, 2021 It\u2019s wrong to say that a diesel engine absolutely needs a turbocharger, but boy do they […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[41],"tags":[],"class_list":["post-20749","post","type-post","status-publish","format-standard","hentry","category-techpost"],"_links":{"self":[{"href":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/wp-json\/wp\/v2\/posts\/20749","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/wp-json\/wp\/v2\/comments?post=20749"}],"version-history":[{"count":0,"href":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/wp-json\/wp\/v2\/posts\/20749\/revisions"}],"wp:attachment":[{"href":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/wp-json\/wp\/v2\/media?parent=20749"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/wp-json\/wp\/v2\/categories?post=20749"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/wp-json\/wp\/v2\/tags?post=20749"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}