 | Home > Td5 > TD5 - VNT Spool? |
 
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| TexasRover Member Since: 24 Nov 2022 Location: Paris Posts: 1304   
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Not 100% sure it's that simple. While petrol engines always digest a correct (stoic) airlfuel mixture, diesels take all the air (no throttle) and fuel is added as required up until there is too much fuel resulting in black smoke. A lot of tuning is simply adding more fuel with the risk of smoke (aka coal rolling). Not good.
So while you could add more air (different turbo) you still need to use that air by adding more fuel. So apart from the turbo you also have to change the fuelling, which is a different program in the computer (ECU). Then at some point with more air and fuel you start raising the exhaust gas temp adding a lot more stress to the engine. I do agree that the lack of decent low end torque of the Td5 sucks |
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20th Aug 2025 5:36pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1454  
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A vnt will spool different to standard/ hybrid turbo. The actual rpm won’t be that significant on paper, but it’s where the toque hits. Mine hits peak torque at 1950….. peak bhp is further along the rev range. It’s a lazier drive….. you have a wider power band, especially in 3/4/5 th. You don’t necessarily get a kick like you can off a standard/hybrid, it just pulls…. Very deceptive. It feels slower,predominately because you don’t have change down and hang onto gears. I’ve had all 3…. In a defender, and plenty of hybrids in other vehicles. It took a while to get used to a vnt…… would I go back…… for everyday use not a chance. Track car ….. maybe
Best thing is to have a go in one ….  |
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20th Aug 2025 5:41pm |
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| jonny Member Since: 10 Mar 2013 Location: North Wilts Posts: 221 |
VNT turbos are supposed to help with the compromises in turbo sizing. You could put a tiny turbo on a TD5, which would generate boost from tickover, but it would run out of puff by 2000RPM. Or you could put a bigger one on, which would be flat until 3000RPM but have the capability to generate massive boost at 5000RPM. VNT is supposed to 'fix' that by behaving like smaller turbo at lower revs, and a larger one at higher revs so you get the best of both. But yes, any turbo will likely need to be supported by a remap... |
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20th Aug 2025 5:55pm |
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| jonny Member Since: 10 Mar 2013 Location: North Wilts Posts: 221 |
I should try and find someone local to have a go in one - it's been a long time since I've had a diesel, and even longer since a manual one. Coming from a big torquey v8 auto I'm finding that I'm driving round outside the power band all the time because it's so flat under 1500RPM (and makes rattly diesel noises at higher revs), so wondering if a VNT would help with that... |
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20th Aug 2025 6:02pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1454
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Also owning a TDV8 L322 fatty, the TD5 drives/delivers the same sort of drive. It’s not got the same power/torque, but is a good deal lighter
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20th Aug 2025 9:39pm |
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| jonny Member Since: 10 Mar 2013 Location: North Wilts Posts: 221 |
Having owned an L322 3.6 TDV8, that was on a totally different level to a TD5!
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21st Aug 2025 9:07am |
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| bankz5152 Member Since: 02 Feb 2017 Location: South London/North Kent Posts: 2225  
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Empires watercooled VNT in a 110, my old 110 and old D2.
The difference is astonishing. While I can't give you any graphs (apart from one dyno from my old 110) I can give you some real world experience. I've been going to Marquenterre in France off roading for the last 10 or so years. In the time Ive taken a stock 90 on 31s, 90 with a map and big IC, 110 with hybrid turbo, D2 on 33s with stock turbo but big IC and mapped and a 110 with a VNT. My 90 would struggle, alot. Required huge run ups and often having to change up to 3rd before getting to the hills. The 110 with the hybrid was similar but less run up and had more umph before it ran out of puff when bogging down in sand. The D2 struggled, alot. The 110 with a VNT. Could start at the base of the same hills and just drive. Then feed power in when needed. Even conquered some of the more extreme hills which where barely driven meaning extremely soft sand. 110 VNT sailed but, albeit with a fair bit of right foot. However never came out of 2nd, never felt the need. Never ran out of puff, torque felt almost unlimited. The guide was very impressed to say the least. As was I. As for road driving its excellent, bundles of low end power then when it opens up it just keeps going. https://youtube.com/shorts/3fZ0Q4wBpww I am fairly on the limit in this video but one of the only people to make it in our group, the other was twin locked with 35s and a VNT. https://youtube.com/shorts/TP1YRL8uV4o The D2 struggling. Can see me flooring in 2nd, snatching 3rd trying to get the revs up b - Keep in mind this also has front and rear ATBS, Difflocked & TC same as the 110. https://youtube.com/shorts/xSLeMZRunK0 https://youtube.com/shorts/GiOe7F8ksI0 https://youtube.com/shorts/lCyASG-A_3w Difference being the 110 has a VNT and around 260hp 580nm torque vs the D2 on around 170/430 or there abouts. A dyno from my old 110.  Click image to enlarge So in short, a VNT makes a huge difference. However only with appropriate mapping and supporting mods. |
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21st Aug 2025 3:01pm |
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| jonny Member Since: 10 Mar 2013 Location: North Wilts Posts: 221 |
Thanks... If you were to find a steepish hill, start off at 1000RPM, at what point would it pick up and go, roughly?
With the standard turbo, you can feel it really pick up around 1500RPM - this is what I'm interested to see if it's improved from a VNT powered engine  |
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21st Aug 2025 3:20pm |
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| bankz5152 Member Since: 02 Feb 2017 Location: South London/North Kent Posts: 2225
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Hard to say as it would depend on the type of VNT and the mapping to suit.
Some tuners effectively dump fuel seems fast but in reality very inefficient and boggy. Some tune well and have a nice linear curve up to max torque and tapers off. So it will vary. VNT will build boost much faster Without doing some side by side testing with some diagnostics be difficult to say. |
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21st Aug 2025 3:29pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8373 
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The vnt adjusts to airflow, you'll never really feel any noticablenkick likens std turbo can produce as its working over a far greater range amd adjusting the kick out, if that makes sense. Cheers James 110 2010 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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21st Aug 2025 3:36pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8373
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Really? Tdv8 must have had problems. My 3.6 and both 4.4 tdv8s l322 and l405 both far outperformed my td5 defender, turned, out perform my m57s with 320bhp too. Cheers James 110 2010 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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21st Aug 2025 3:38pm |
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| bankz5152 Member Since: 02 Feb 2017 Location: South London/North Kent Posts: 2225
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Tbf i second this. Dads got an 07 RR, my TD5 pulls the same. Also beat my mates 05 TDV8 L322 in a drag race 🤣 |
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21st Aug 2025 5:14pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1454
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Glad someone can see the comparison
They basically DRIVE similarly. With the VNT you change earlier, as you don’t need to rev it to keep on boost. You drive it more lazily, hence the comparison to a tdv8. it’s a lot calmer, no need to keep going up and down the box.‘I rarely go above 2500 rpm there’s little point. A turbo is a compromise however you have it……. You have to be on boost to have a gain…. And thats limiting factor. Where do you want the boost??? Vnt will drop it to lower revs… |
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21st Aug 2025 7:36pm |
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| bankz5152 Member Since: 02 Feb 2017 Location: South London/North Kent Posts: 2225
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Pretty solid answer there.
VNT just works, when you need it |
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21st Aug 2025 7:59pm |
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