At what speed do turbos kick in?
What Speed Does Turbo Kick In [Turbo boost explained]
If you’ve ever wondered at what speed does your turbo kick in, then you have come to the right place. This article explains exactly what it is that causes your turbo to “kick in” and how to take full control of it with some minor upgrades. The thing that makes a turbocharger “kick in” is exhaust pressure. This pressure is created by increasing the RPMs (Revolutions per minute), not necessarily the speed. A turbo needs to build enough pressure inside the turbo to spool/spin up the compressor wheel, this pressure is achieved between 1800 to 2200 RPM. Most everyday turbo cars come stock with a small single turbo that usually operates at between 6-8lbs of boost. The reason for this is that it’s perfect for everyday driving, it provides a little more horsepower, making the car more responsive, while still not being too aggressive for daily driving. Plus it drastically cuts down on emissions due to the turbo basically recycling the exhaust gasses.
Most people over time will find they notice what speed the turbo kicks in in each gear and assume that the turbo is controlled by the speed of the vehicle when in fact it is controlled by the RPM range of the engine. A small single turbo will generally need between 1800 to 2000 RPM to make it “kick in” or “boost” as it is more commonly known. This is because a small turbocharger will only need a small volume of air/gas to fill the housing of the turbo and create an adequate amount of boost pressure. A bigger turbocharger, however, will take much more air to fill it thus it will take a higher RPM to create a sufficient amount of boost pressure, it will also take slightly longer for the turbo to build maximum boost pressure, this time delay is known as turbo lag. Turbo lag is felt when you press down on the accelerator and it feels like the car is not as responsive as it should be, it may also feel sluggish for a second or two after you accelerate, then build full boost and stick you back in the seat. Bigger turbos will generally need between 2000 – 2500 RPM to build enough boost pressure to get the turbo to kick in and create enough pressure to get the compressor wheel spooling at full speed. This is the reason smaller turbochargers are more popular for most applications if it is quick acceleration with a lower BHP that is needed. A turbo can kick in at speed as low as 10 MPH under hard acceleration and high RPMs, but on the other hand, you could be driving along at a speed of 60 MPH at 3000 RPM under light acceleration and the turbo will not build boost pressure at all because the engine is not forcing out huge amount of gas as it would under hard acceleration. Although technically a turbo is always on or at least always spinning, it is not always spinning fast enough to build the correct pressure inside the compressor housing of the turbocharger. To find out all the different types of turbos and how exactly how each one works, you should check out this article, I think you will enjoy it.
Gavin With over twenty years worth of experience in the motorsport industry and many happy customers you can rest assured that the information you get here on BackyardBuildz.com is 100% free, reliable and without the fluff.
Recent Posts
A question I get asked a lot is should you let a turbo car warm up and cool down before driving it? And if so, how do you do it? Well, the answer is simple. If the ambient temperature is below.
Our Mission
Our mission here at Backyard Buildz is to save you hours of precious time by giving you the answers you need to all your motoring problems and needs without fluff or bias. We cover everything from step-by-step repairs and maintenance to the best tools to buy your husband for his birthday with industry-leading reviews and insights. We as petrol heads know the frustration of spending hours scrolling through useless information, that’s why we here at Backyard Buildz pride ourselves on only providing 100% reliable information. Meet the Author
LEGAL INFORMATION
BackyardBuildz.com is a participant in the Amazon Services LLC Associates Program. As an Amazon Associate, I earn from qualifying purchases. This Does Not cost you extra. This site also participates in other affiliate programs and is compensated for referring traffic and business to these companies.
What is a Turbo Engine and How Does It Work?
We’ve all heard of turbo engines but how much do you know about how they work? In this guide, we look at the ins and outs of turbochargers, from their benefits and downsides to how they differ from normally aspirated engines.
What is a Turbocharger?
A turbocharger is a component comprised of a turbine and air compressor which is used to harness the waste exhaust gases emitted from an engine. It forces more air into the cylinders, helping the engine to produce more power.
How Do They Work?
Turbos are composed of a shaft with a turbine wheel on one end and a compressor wheel on the other. These are covered by a snail-shaped housing featuring an inlet port, which the wasted exhaust gases enter at a high pressure. As the air passes through the turbine, the turbine spins and the compressor turns with it, drawing in vast quantities of air which are compressed and passed out of the outlet port.
A pipe feeds this compressed air back into the cylinders via an intercooler, which cools the air before it reaches the cylinders. As turbos run at such high speeds (up to 250,000 RPM), they typically have an oil cooling system to make sure they don’t run too hot. Most systems also contain a valve known as a ‘wastegate’, which is used to divert excess gas away from the turbocharger when the engine produces too much boost, preventing damage to the turbine by limiting its rotational speed.
Turbocharged engines differ from standard engines in that they make use of wasted exhaust gases to pull more air into the intake valve. While naturally-aspirated engines rely on natural air pressure to draw air into the engine, turbos speed up this process, producing power more economically.
What Are the Benefits of Turbos?
Turbochargers offer a range of benefits, hence why they’re now so popular on modern cars. Here, we list the main plus points of a turbocharged engine.
Power
Turbos produce more power in the same sized engine. That’s because every stroke of the piston generates more power than in naturally-aspirated engines. This means that more cars are now fitted with smaller, turbocharged engines, replacing larger and less economical units. A good example of this is Ford’s decision to replace its standard 1.6L petrol engine with a 1L turbocharged unit, which it calls EcoBoost.
Economy
Because turbochargers can produce the same power output as larger, naturally-aspirated engines, this paves the way for the use of smaller, lighter and more economical engines. Now, all modern diesel cars are fitted with a turbocharger, improving fuel economy and reducing emissions.
Torque and Performance
Even on the smallest engines, turbochargers produce more torque, particularly lower down the rev range. This means cars benefit from strong, nippy performance, which is great around town and helps the engine to feel more refined at higher speeds on motorways and A roads. At low speeds, small turbocharged engines can outpace cars fitted with larger, naturally-aspirated engines, because of the torque they produce.
Quiet Engines
As the air in a turbocharged engine is filtered through more pipes and components, the intake and exhaust noise is reduced and refined, making for a quieter and smoother engine noise – perhaps one of the most unexpected benefits of a turbocharged engine.
And What are the Downsides?
While turbos are becoming ever more popular, they do have some pitfalls, which we’ve listed below.
Expensive Repair Costs
Turbochargers add complexity to an engine, with a whole host of other components beneath the bonnet that can fail or develop faults. These problems can be expensive to put right, and can have an impact on other components if they fail.
Turbo Lag
Turbo lag is a brief delay in response after pressing the throttle, which can occur when the engine isn’t producing enough exhaust gas to spin the turbo’s intake turbine quick enough. This only really happens when the car is being driven aggressively, or from a closed throttle position. In high-performance cars, manufacturers prevent turbo lag by adding two turbochargers of differing geometry, rather than one big one with only a single turbine.
Efficiency vs Driving Style
Achieving the claimed efficiency figures of a turbocharged engine requires careful throttle control, whereby the accelerator isn’t pressed too hard. When a turbocharger is ‘on boost’, the cylinders are burning fuel more quickly, leading to poor efficiency. Drivers going from a naturally-aspirated car to a turbocharged model may need to adjust their driving style to maintain good efficiency, particularly when first setting off.
Where Do Turbochargers Come From?
The first turbocharger was produced in the late 19 th century by German engineer, Gottlieb Daimler, but they didn’t come to prominence until after WWI, when aircraft manufacturers began adding them to aeroplanes to provide power to engines operating at higher altitudes, where the air is thinner.
Turbochargers weren’t added to car engines until 1961, when US manufacturer Oldsmobile, used a simple turbo to boost the power of a 3.5L V8 engine. In 1984, Saab developed a new, more efficient turbo system, and this design, with a few tweaks and modifications, remains the most popular turbocharger configuration today.
At Redex, our fuel system additives improve performance in turbocharged and naturally-aspirated diesel and petrol engines. With a shot of Redex in every tank of fuel, you can enjoy improved performance and engine health. For more information, visit the Redex homepage.
At what speed do turbos kick in?
I am sure I read somewhere that driving a cdti below 1500 rpm is like driving an old lugger as the turbo cuts in a those revs. I been getting poor fuel returns (38-41mpg on a run) and I was advised to keep it above 1500 if possible. My engine really doesn’t do anything until I hit 2000rpm and then it takes off like a rocket. When should it do this 1500 or 2000? I have been driving it very carefully in the past but now I am driving it harder to see if it makes a difference.
While on the subject I am really beginning to notice the difference between this manual and my old auto. Lots of strange noises one of which sounds like a thrust bearing issue, on deceleration, which is the opposite of what I would expect. I get a whining noise when I switch the AC on too but it works like a dream and has no leaks.
I have just noticed all these things as I have done my first long run in traffic going to Cornwall and back. I may have to go back to an auto soon!
spyder
25th July 2015, 14:20
The turbo is turning all the time while the engine is running. The higher the engine revs, the more exhaust gases, the faster the turbo will turn, the higher the pressure will be.
What does change is the waste gate will open to exhaust some of the pressure to atmosphere. This is controlled by vacuum, which is in turn controlled by diaphragm. On these cars it is electronically controlled by the ECU using amongst others, readings from the boost pressure (MAP) as well as the engine revs.
How, why and when it opens I have no idea. But driving any car within the appropriate torque range will always save fuel.
arnosvale65
25th July 2015, 14:26
Thanks for that Spyder. I take it then that I should keep the revs up and not let it lug in too high a gear?
Mike Noc
25th July 2015, 14:54
Sluggish running below 2000 rpm is often a sign that the MAF is not working correctly. Try unplugging it and see if things improve.
arnosvale65
25th July 2015, 18:46
Sluggish running below 2000 rpm is often a sign that the MAF is not working correctly. Try unplugging it and see if things improve.
I will Mike, thanks for the tip.
grivas
25th July 2015, 19:01
I will Mike, thanks for the tip.
The symptoms you describe point to a MAF sensor that has had its day, what is the history of this sensor when was it last changed, as suggested elsewhere, disconnect it and go for a run if the car drives well and pulls well in all gears and well within the useful rev range, then there is your problem, buy a new GENUINE MAF sensor not which is aftermarket, better still get a Pierburg version and a digimafam from Roveron, and that is it you will not likely need to change it again.
Please remember to drive the car sensibly within the rev range appropriate to the driving conditions, no need to aim to keep revs at approx. 1500rps, you are not driving a racing car, but do please give the car a good run to get the engine really moving from time to time, once it is thoroughly warmed up, etc..
arnosvale65
26th July 2015, 12:53
The symptoms you describe point to a MAF sensor that has had its day, what is the history of this sensor when was it last changed, as suggested elsewhere, disconnect it and go for a run if the car drives well and pulls well in all gears and well within the useful rev range, then there is your problem, buy a new GENUINE MAF sensor not which is aftermarket, better still get a Pierburg version and a digimafam from Roveron, and that is it you will not likely need to change it again.
Please remember to drive the car sensibly within the rev range appropriate to the driving conditions, no need to aim to keep revs at approx. 1500rps, you are not driving a racing car, but do please give the car a good run to get the engine really moving from time to time, once it is thoroughly warmed up, etc..
Thanks Grivas. Looks like I will have to bite the bullet and get a new MAF sensor. It may work out cheaper to get another 75 as mine also needs rear pads and discs. It has done 190000 miles so I don’t really want to keep spending money on it.
Ken Lion
26th July 2015, 16:14
What’s the situation with your EGR Steve?
— by-passed? — cleaned? — never touched?
If it’s not been by-passed you might want to have a look at that before you spend serious dosh on a Maf.
bl52krz
26th July 2015, 17:19
Turbo starts to give the engine more power supposedly around 1760/1900 rpm.
spyder
26th July 2015, 18:25
Turbo starts to give the engine more power supposedly around 1760/1900 rpm.
That is the start of the torque curve for the diesels, basically where the pressure available begins to exceed atmospheric pressure-in very simplistic terms that is.;)
arnosvale65
26th July 2015, 22:05
What’s the situation with your EGR Steve?
— by-passed? — cleaned? — never touched?
If it’s not been by-passed you might want to have a look at that before you spend serious dosh on a Maf.
I don’t think it has ever been touched according to the History. I went for a drive today and in the lower gears she seems OK. The main problem is when I take my foot off in 5th or 4th and then accelerate again. She is very poor until she reaches 2000rpm, then woosh! Off she goes.
Ken Lion
27th July 2015, 10:46
I don’t think it has ever been touched according to the History. I went for a drive today and in the lower gears she seems OK. The main problem is when I take my foot off in 5th or 4th and then accelerate again. She is very poor until she reaches 2000rpm, then woosh! Off she goes.
Well, cleaning out the EGR is a cheap first step before spending serious money elsewhere — but it’s a messy job.
A quicker/easier way may be to deactivate the EGR by pulling off and stopping-up the vacuum tube (with a suitable screw). But if the EGR is seriously gummed up and restricting air flow from the turbo then it’s not improving anything (see thread from Eddiemc05 http://www.the75andztclub.co.uk/forum/showthread.php?t=222086 ).
There’s a great picture by picture how-to thread from Arctic Steve about removing / cleaning the egr (and manifold) if it’s new to you:
Avulon
27th July 2015, 13:57
I don’t think it has ever been touched according to the History. I went for a drive today and in the lower gears she seems OK. The main problem is when I take my foot off in 5th or 4th and then accelerate again. She is very poor until she reaches 2000rpm, then woosh! Off she goes.
Without knowing your experience with cars — i.e. what you’ve driven before. ‘very poor’ could mean a wide variety of ‘not much go’. To be honest you won’t get much ‘go’ below 2000rpm if you shove your foot down hard in 4th and 5th gear. It’ll pull about as well as an asthmatic 1.8 (nasp) at best. Any MAF problems and the response will be a lot worse. If you can test the MAF or get to a T4 operator who can take the readings for you then get it checked. Bear in mind that 1500rpm in 5th is 50mph, and you won’t get any real acceleration at that speed in top gear at all anyway. Shift up a 1000 rpm and it’ll go just fine (between 1700 and 2400) don’t be afraid to rev it a little — red line isn’t until 4600rpm and you’ll never need to take it over 3000 unless you want to :). However you should get reasonable engine response from as little as 1000 rpm in the lower gears. (1,2,3).
arnosvale65
27th July 2015, 15:43
Without knowing your experience with cars — i.e. what you’ve driven before. ‘very poor’ could mean a wide variety of ‘not much go’. To be honest you won’t get much ‘go’ below 2000rpm if you shove your foot down hard in 4th and 5th gear. It’ll pull about as well as an asthmatic 1.8 (nasp) at best. Any MAF problems and the response will be a lot worse. If you can test the MAF or get to a T4 operator who can take the readings for you then get it checked. Bear in mind that 1500rpm in 5th is 50mph, and you won’t get any real acceleration at that speed in top gear at all anyway. Shift up a 1000 rpm and it’ll go just fine (between 1700 and 2400) don’t be afraid to rev it a little — red line isn’t until 4600rpm and you’ll never need to take it over 3000 unless you want to :). However you should get reasonable engine response from as little as 1000 rpm in the lower gears. (1,2,3).
Thanks very much Avulon. I have experience of the Ford 2.0tdci engine fitted to an X type Jag which went like the proverbial, the 2.2 even better. My wife has a Laguna 111 2.0 cdti which is very quiet, great on fuel and goes well. I think I am not giving it enough revs and expecting it to take off in too high a gear as you suggest, mind you the Laguna tells you when to change up or down. The downshifts always coming way before I would normally.
I have just ordered an EGR valve by-pass from DMGRS. My X types suffered terribly with problems with the EGR. I don’t know if you have ever read any of Diesel Bob’s articles about different makes of diesel engines but it is well worth a look.
He doesn’t have a good thing to say about Ford’s 2.0ltr tdci
James.uk
27th July 2015, 18:28
Nothing works well when over geared (i.e. in too high a gear) even a bicycle struggles to accelerate from low speeds in top gear.. :duh:
For the sake of engine longevity, you should always try to keep enough revs on to allow your engine to perform well. :>
Flogging an engine in too low a gear puts severe strains on all parts of the drive train including the gearbox. 😮
Diesel engines thrive on hard work, so give em bags of welly innit. :D:D:D
.
Avulon
27th July 2015, 19:42
Thanks very much Avulon. I have experience of the Ford 2.0tdci engine fitted to an X type Jag which went like the proverbial, the 2.2 even better. My wife has a Laguna 111 2.0 cdti which is very quiet, great on fuel and goes well. I think I am not giving it enough revs and expecting it to take off in too high a gear as you suggest, mind you the Laguna tells you when to change up or down. The downshifts always coming way before I would normally.
I have just ordered an EGR valve by-pass from DMGRS. My X types suffered terribly with problems with the EGR. I don’t know if you have ever read any of Diesel Bob’s articles about different makes of diesel engines but it is well worth a look.
He doesn’t have a good thing to say about Ford’s 2.0ltr tdci
I also think that if your diesel is 115 then it’s going to feel sluggish next to any of those others you list, the 135 tune is much more driveable. the 160 is best though as the turbo boost is felt earlier in the rev range. Sounds like the laguna is a 147 so will be way quicker than a 115 (which is carrying an extra 100kg as well). Give it more revs and get the MAF checked. If it’s still too slow then get the 160 map on it.
